Adding upstream version 14.5.upstream/14.5upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

36 files changed, 43197 insertions, 0 deletions

diff --git a/src/backend/replication/.gitignore b/src/backend/replication/.gitignore
new file mode 100644
index 0000000..d1df614
--- /dev/null
+++ b/src/backend/replication/.gitignore
@@ -0,0 +1,4 @@
+/repl_gram.c
+/repl_scanner.c
+/syncrep_gram.c
+/syncrep_scanner.c
diff --git a/src/backend/replication/Makefile b/src/backend/replication/Makefile
new file mode 100644
index 0000000..a0381e5
--- /dev/null
+++ b/src/backend/replication/Makefile
@@ -0,0 +1,41 @@
+#-------------------------------------------------------------------------
+#
+# Makefile--
+#    Makefile for src/backend/replication
+#
+# IDENTIFICATION
+#    src/backend/replication/Makefile
+#
+#-------------------------------------------------------------------------
+
+subdir = src/backend/replication
+top_builddir = ../../..
+include $(top_builddir)/src/Makefile.global
+
+override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)
+
+OBJS = \
+	backup_manifest.o \
+	basebackup.o \
+	repl_gram.o \
+	slot.o \
+	slotfuncs.o \
+	syncrep.o \
+	syncrep_gram.o \
+	walreceiver.o \
+	walreceiverfuncs.o \
+	walsender.o
+
+SUBDIRS = logical
+
+include $(top_srcdir)/src/backend/common.mk
+
+# repl_scanner is compiled as part of repl_gram
+repl_gram.o: repl_scanner.c
+
+# syncrep_scanner is compiled as part of syncrep_gram
+syncrep_gram.o: syncrep_scanner.c
+
+# repl_gram.c, repl_scanner.c, syncrep_gram.c and syncrep_scanner.c
+# are in the distribution tarball, so they are not cleaned here.
+# (Our parent Makefile takes care of them during maintainer-clean.)
diff --git a/src/backend/replication/README b/src/backend/replication/README
new file mode 100644
index 0000000..8fcd78d
--- /dev/null
+++ b/src/backend/replication/README
@@ -0,0 +1,76 @@
+src/backend/replication/README
+
+Walreceiver - libpqwalreceiver API
+----------------------------------
+
+The transport-specific part of walreceiver, responsible for connecting to
+the primary server, receiving WAL files and sending messages, is loaded
+dynamically to avoid having to link the main server binary with libpq.
+The dynamically loaded module is in libpqwalreceiver subdirectory.
+
+The dynamically loaded module implements a set of functions with details
+about each one of them provided in src/include/replication/walreceiver.h.
+
+This API should be considered internal at the moment, but we could open it
+up for 3rd party replacements of libpqwalreceiver in the future, allowing
+pluggable methods for receiving WAL.
+
+Walreceiver IPC
+---------------
+
+When the WAL replay in startup process has reached the end of archived WAL,
+restorable using restore_command, it starts up the walreceiver process
+to fetch more WAL (if streaming replication is configured).
+
+Walreceiver is a postmaster subprocess, so the startup process can't fork it
+directly. Instead, it sends a signal to postmaster, asking postmaster to launch
+it. Before that, however, startup process fills in WalRcvData->conninfo
+and WalRcvData->slotname, and initializes the starting point in
+WalRcvData->receiveStart.
+
+As walreceiver receives WAL from the primary server, and writes and flushes
+it to disk (in pg_wal), it updates WalRcvData->flushedUpto and signals
+the startup process to know how far WAL replay can advance.
+
+Walreceiver sends information about replication progress to the primary server
+whenever it either writes or flushes new WAL, or the specified interval elapses.
+This is used for reporting purpose.
+
+Walsender IPC
+-------------
+
+At shutdown, postmaster handles walsender processes differently from regular
+backends. It waits for regular backends to die before writing the
+shutdown checkpoint and terminating pgarch and other auxiliary processes, but
+that's not desirable for walsenders, because we want the standby servers to
+receive all the WAL, including the shutdown checkpoint, before the primary
+is shut down. Therefore postmaster treats walsenders like the pgarch process,
+and instructs them to terminate at PM_SHUTDOWN_2 phase, after all regular
+backends have died and checkpointer has issued the shutdown checkpoint.
+
+When postmaster accepts a connection, it immediately forks a new process
+to handle the handshake and authentication, and the process initializes to
+become a backend. Postmaster doesn't know if the process becomes a regular
+backend or a walsender process at that time - that's indicated in the
+connection handshake - so we need some extra signaling to let postmaster
+identify walsender processes.
+
+When walsender process starts up, it marks itself as a walsender process in
+the PMSignal array. That way postmaster can tell it apart from regular
+backends.
+
+Note that no big harm is done if postmaster thinks that a walsender is a
+regular backend; it will just terminate the walsender earlier in the shutdown
+phase. A walsender will look like a regular backend until it's done with the
+initialization and has marked itself in PMSignal array, and at process
+termination, after unmarking the PMSignal slot.
+
+Each walsender allocates an entry from the WalSndCtl array, and tracks
+information about replication progress. User can monitor them via
+statistics views.
+
+
+Walsender - walreceiver protocol
+--------------------------------
+
+See manual.
diff --git a/src/backend/replication/backup_manifest.c b/src/backend/replication/backup_manifest.c
new file mode 100644
index 0000000..04ca455
--- /dev/null
+++ b/src/backend/replication/backup_manifest.c
@@ -0,0 +1,408 @@
+/*-------------------------------------------------------------------------
+ *
+ * backup_manifest.c
+ *	  code for generating and sending a backup manifest
+ *
+ * Portions Copyright (c) 2010-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/backup_manifest.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/timeline.h"
+#include "libpq/libpq.h"
+#include "libpq/pqformat.h"
+#include "mb/pg_wchar.h"
+#include "replication/backup_manifest.h"
+#include "utils/builtins.h"
+#include "utils/json.h"
+
+static void AppendStringToManifest(backup_manifest_info *manifest, char *s);
+
+/*
+ * Does the user want a backup manifest?
+ *
+ * It's simplest to always have a manifest_info object, so that we don't need
+ * checks for NULL pointers in too many places. However, if the user doesn't
+ * want a manifest, we set manifest->buffile to NULL.
+ */
+static inline bool
+IsManifestEnabled(backup_manifest_info *manifest)
+{
+	return (manifest->buffile != NULL);
+}
+
+/*
+ * Convenience macro for appending data to the backup manifest.
+ */
+#define AppendToManifest(manifest, ...) \
+	{ \
+		char *_manifest_s = psprintf(__VA_ARGS__);	\
+		AppendStringToManifest(manifest, _manifest_s);	\
+		pfree(_manifest_s);	\
+	}
+
+/*
+ * Initialize state so that we can construct a backup manifest.
+ *
+ * NB: Although the checksum type for the data files is configurable, the
+ * checksum for the manifest itself always uses SHA-256. See comments in
+ * SendBackupManifest.
+ */
+void
+InitializeBackupManifest(backup_manifest_info *manifest,
+						 backup_manifest_option want_manifest,
+						 pg_checksum_type manifest_checksum_type)
+{
+	memset(manifest, 0, sizeof(backup_manifest_info));
+	manifest->checksum_type = manifest_checksum_type;
+
+	if (want_manifest == MANIFEST_OPTION_NO)
+		manifest->buffile = NULL;
+	else
+	{
+		manifest->buffile = BufFileCreateTemp(false);
+		manifest->manifest_ctx = pg_cryptohash_create(PG_SHA256);
+		if (pg_cryptohash_init(manifest->manifest_ctx) < 0)
+			elog(ERROR, "failed to initialize checksum of backup manifest");
+	}
+
+	manifest->manifest_size = UINT64CONST(0);
+	manifest->force_encode = (want_manifest == MANIFEST_OPTION_FORCE_ENCODE);
+	manifest->first_file = true;
+	manifest->still_checksumming = true;
+
+	if (want_manifest != MANIFEST_OPTION_NO)
+		AppendToManifest(manifest,
+						 "{ \"PostgreSQL-Backup-Manifest-Version\": 1,\n"
+						 "\"Files\": [");
+}
+
+/*
+ * Free resources assigned to a backup manifest constructed.
+ */
+void
+FreeBackupManifest(backup_manifest_info *manifest)
+{
+	pg_cryptohash_free(manifest->manifest_ctx);
+	manifest->manifest_ctx = NULL;
+}
+
+/*
+ * Add an entry to the backup manifest for a file.
+ */
+void
+AddFileToBackupManifest(backup_manifest_info *manifest, const char *spcoid,
+						const char *pathname, size_t size, pg_time_t mtime,
+						pg_checksum_context *checksum_ctx)
+{
+	char		pathbuf[MAXPGPATH];
+	int			pathlen;
+	StringInfoData buf;
+
+	if (!IsManifestEnabled(manifest))
+		return;
+
+	/*
+	 * If this file is part of a tablespace, the pathname passed to this
+	 * function will be relative to the tar file that contains it. We want the
+	 * pathname relative to the data directory (ignoring the intermediate
+	 * symlink traversal).
+	 */
+	if (spcoid != NULL)
+	{
+		snprintf(pathbuf, sizeof(pathbuf), "pg_tblspc/%s/%s", spcoid,
+				 pathname);
+		pathname = pathbuf;
+	}
+
+	/*
+	 * Each file's entry needs to be separated from any entry that follows by
+	 * a comma, but there's no comma before the first one or after the last
+	 * one. To make that work, adding a file to the manifest starts by
+	 * terminating the most recently added line, with a comma if appropriate,
+	 * but does not terminate the line inserted for this file.
+	 */
+	initStringInfo(&buf);
+	if (manifest->first_file)
+	{
+		appendStringInfoChar(&buf, '\n');
+		manifest->first_file = false;
+	}
+	else
+		appendStringInfoString(&buf, ",\n");
+
+	/*
+	 * Write the relative pathname to this file out to the manifest. The
+	 * manifest is always stored in UTF-8, so we have to encode paths that are
+	 * not valid in that encoding.
+	 */
+	pathlen = strlen(pathname);
+	if (!manifest->force_encode &&
+		pg_verify_mbstr(PG_UTF8, pathname, pathlen, true))
+	{
+		appendStringInfoString(&buf, "{ \"Path\": ");
+		escape_json(&buf, pathname);
+		appendStringInfoString(&buf, ", ");
+	}
+	else
+	{
+		appendStringInfoString(&buf, "{ \"Encoded-Path\": \"");
+		enlargeStringInfo(&buf, 2 * pathlen);
+		buf.len += hex_encode(pathname, pathlen,
+							  &buf.data[buf.len]);
+		appendStringInfoString(&buf, "\", ");
+	}
+
+	appendStringInfo(&buf, "\"Size\": %zu, ", size);
+
+	/*
+	 * Convert last modification time to a string and append it to the
+	 * manifest. Since it's not clear what time zone to use and since time
+	 * zone definitions can change, possibly causing confusion, use GMT
+	 * always.
+	 */
+	appendStringInfoString(&buf, "\"Last-Modified\": \"");
+	enlargeStringInfo(&buf, 128);
+	buf.len += pg_strftime(&buf.data[buf.len], 128, "%Y-%m-%d %H:%M:%S %Z",
+						   pg_gmtime(&mtime));
+	appendStringInfoChar(&buf, '"');
+
+	/* Add checksum information. */
+	if (checksum_ctx->type != CHECKSUM_TYPE_NONE)
+	{
+		uint8		checksumbuf[PG_CHECKSUM_MAX_LENGTH];
+		int			checksumlen;
+
+		checksumlen = pg_checksum_final(checksum_ctx, checksumbuf);
+		if (checksumlen < 0)
+			elog(ERROR, "could not finalize checksum of file \"%s\"",
+				 pathname);
+
+		appendStringInfo(&buf,
+						 ", \"Checksum-Algorithm\": \"%s\", \"Checksum\": \"",
+						 pg_checksum_type_name(checksum_ctx->type));
+		enlargeStringInfo(&buf, 2 * checksumlen);
+		buf.len += hex_encode((char *) checksumbuf, checksumlen,
+							  &buf.data[buf.len]);
+		appendStringInfoChar(&buf, '"');
+	}
+
+	/* Close out the object. */
+	appendStringInfoString(&buf, " }");
+
+	/* OK, add it to the manifest. */
+	AppendStringToManifest(manifest, buf.data);
+
+	/* Avoid leaking memory. */
+	pfree(buf.data);
+}
+
+/*
+ * Add information about the WAL that will need to be replayed when restoring
+ * this backup to the manifest.
+ */
+void
+AddWALInfoToBackupManifest(backup_manifest_info *manifest, XLogRecPtr startptr,
+						   TimeLineID starttli, XLogRecPtr endptr,
+						   TimeLineID endtli)
+{
+	List	   *timelines;
+	ListCell   *lc;
+	bool		first_wal_range = true;
+	bool		found_start_timeline = false;
+
+	if (!IsManifestEnabled(manifest))
+		return;
+
+	/* Terminate the list of files. */
+	AppendStringToManifest(manifest, "\n],\n");
+
+	/* Read the timeline history for the ending timeline. */
+	timelines = readTimeLineHistory(endtli);
+
+	/* Start a list of LSN ranges. */
+	AppendStringToManifest(manifest, "\"WAL-Ranges\": [\n");
+
+	foreach(lc, timelines)
+	{
+		TimeLineHistoryEntry *entry = lfirst(lc);
+		XLogRecPtr	tl_beginptr;
+
+		/*
+		 * We only care about timelines that were active during the backup.
+		 * Skip any that ended before the backup started. (Note that if
+		 * entry->end is InvalidXLogRecPtr, it means that the timeline has not
+		 * yet ended.)
+		 */
+		if (!XLogRecPtrIsInvalid(entry->end) && entry->end < startptr)
+			continue;
+
+		/*
+		 * Because the timeline history file lists newer timelines before
+		 * older ones, the first timeline we encounter that is new enough to
+		 * matter ought to match the ending timeline of the backup.
+		 */
+		if (first_wal_range && endtli != entry->tli)
+			ereport(ERROR,
+					errmsg("expected end timeline %u but found timeline %u",
+						   starttli, entry->tli));
+
+		/*
+		 * If this timeline entry matches with the timeline on which the
+		 * backup started, WAL needs to be checked from the start LSN of the
+		 * backup.  If this entry refers to a newer timeline, WAL needs to be
+		 * checked since the beginning of this timeline, so use the LSN where
+		 * the timeline began.
+		 */
+		if (starttli == entry->tli)
+			tl_beginptr = startptr;
+		else
+		{
+			tl_beginptr = entry->begin;
+
+			/*
+			 * If we reach a TLI that has no valid beginning LSN, there can't
+			 * be any more timelines in the history after this point, so we'd
+			 * better have arrived at the expected starting TLI. If not,
+			 * something's gone horribly wrong.
+			 */
+			if (XLogRecPtrIsInvalid(entry->begin))
+				ereport(ERROR,
+						errmsg("expected start timeline %u but found timeline %u",
+							   starttli, entry->tli));
+		}
+
+		AppendToManifest(manifest,
+						 "%s{ \"Timeline\": %u, \"Start-LSN\": \"%X/%X\", \"End-LSN\": \"%X/%X\" }",
+						 first_wal_range ? "" : ",\n",
+						 entry->tli,
+						 LSN_FORMAT_ARGS(tl_beginptr),
+						 LSN_FORMAT_ARGS(endptr));
+
+		if (starttli == entry->tli)
+		{
+			found_start_timeline = true;
+			break;
+		}
+
+		endptr = entry->begin;
+		first_wal_range = false;
+	}
+
+	/*
+	 * The last entry in the timeline history for the ending timeline should
+	 * be the ending timeline itself. Verify that this is what we observed.
+	 */
+	if (!found_start_timeline)
+		ereport(ERROR,
+				errmsg("start timeline %u not found in history of timeline %u",
+					   starttli, endtli));
+
+	/* Terminate the list of WAL ranges. */
+	AppendStringToManifest(manifest, "\n],\n");
+}
+
+/*
+ * Finalize the backup manifest, and send it to the client.
+ */
+void
+SendBackupManifest(backup_manifest_info *manifest)
+{
+	StringInfoData protobuf;
+	uint8		checksumbuf[PG_SHA256_DIGEST_LENGTH];
+	char		checksumstringbuf[PG_SHA256_DIGEST_STRING_LENGTH];
+	size_t		manifest_bytes_done = 0;
+
+	if (!IsManifestEnabled(manifest))
+		return;
+
+	/*
+	 * Append manifest checksum, so that the problems with the manifest itself
+	 * can be detected.
+	 *
+	 * We always use SHA-256 for this, regardless of what algorithm is chosen
+	 * for checksumming the files.  If we ever want to make the checksum
+	 * algorithm used for the manifest file variable, the client will need a
+	 * way to figure out which algorithm to use as close to the beginning of
+	 * the manifest file as possible, to avoid having to read the whole thing
+	 * twice.
+	 */
+	manifest->still_checksumming = false;
+	if (pg_cryptohash_final(manifest->manifest_ctx, checksumbuf,
+							sizeof(checksumbuf)) < 0)
+		elog(ERROR, "failed to finalize checksum of backup manifest");
+	AppendStringToManifest(manifest, "\"Manifest-Checksum\": \"");
+
+	hex_encode((char *) checksumbuf, sizeof checksumbuf, checksumstringbuf);
+	checksumstringbuf[PG_SHA256_DIGEST_STRING_LENGTH - 1] = '\0';
+
+	AppendStringToManifest(manifest, checksumstringbuf);
+	AppendStringToManifest(manifest, "\"}\n");
+
+	/*
+	 * We've written all the data to the manifest file.  Rewind the file so
+	 * that we can read it all back.
+	 */
+	if (BufFileSeek(manifest->buffile, 0, 0L, SEEK_SET))
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not rewind temporary file")));
+
+	/* Send CopyOutResponse message */
+	pq_beginmessage(&protobuf, 'H');
+	pq_sendbyte(&protobuf, 0);	/* overall format */
+	pq_sendint16(&protobuf, 0); /* natts */
+	pq_endmessage(&protobuf);
+
+	/*
+	 * Send CopyData messages.
+	 *
+	 * We choose to read back the data from the temporary file in chunks of
+	 * size BLCKSZ; this isn't necessary, but buffile.c uses that as the I/O
+	 * size, so it seems to make sense to match that value here.
+	 */
+	while (manifest_bytes_done < manifest->manifest_size)
+	{
+		char		manifestbuf[BLCKSZ];
+		size_t		bytes_to_read;
+		size_t		rc;
+
+		bytes_to_read = Min(sizeof(manifestbuf),
+							manifest->manifest_size - manifest_bytes_done);
+		rc = BufFileRead(manifest->buffile, manifestbuf, bytes_to_read);
+		if (rc != bytes_to_read)
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not read from temporary file: %m")));
+		pq_putmessage('d', manifestbuf, bytes_to_read);
+		manifest_bytes_done += bytes_to_read;
+	}
+
+	/* No more data, so send CopyDone message */
+	pq_putemptymessage('c');
+
+	/* Release resources */
+	BufFileClose(manifest->buffile);
+}
+
+/*
+ * Append a cstring to the manifest.
+ */
+static void
+AppendStringToManifest(backup_manifest_info *manifest, char *s)
+{
+	int			len = strlen(s);
+
+	Assert(manifest != NULL);
+	if (manifest->still_checksumming)
+	{
+		if (pg_cryptohash_update(manifest->manifest_ctx, (uint8 *) s, len) < 0)
+			elog(ERROR, "failed to update checksum of backup manifest");
+	}
+	BufFileWrite(manifest->buffile, s, len);
+	manifest->manifest_size += len;
+}
diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
new file mode 100644
index 0000000..d142cc2
--- /dev/null
+++ b/src/backend/replication/basebackup.c
@@ -0,0 +1,2034 @@
+/*-------------------------------------------------------------------------
+ *
+ * basebackup.c
+ *	  code for taking a base backup and streaming it to a standby
+ *
+ * Portions Copyright (c) 2010-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/basebackup.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <sys/stat.h>
+#include <unistd.h>
+#include <time.h>
+
+#include "access/xlog_internal.h"	/* for pg_start/stop_backup */
+#include "catalog/pg_type.h"
+#include "common/file_perm.h"
+#include "commands/progress.h"
+#include "lib/stringinfo.h"
+#include "libpq/libpq.h"
+#include "libpq/pqformat.h"
+#include "miscadmin.h"
+#include "nodes/pg_list.h"
+#include "pgstat.h"
+#include "pgtar.h"
+#include "port.h"
+#include "postmaster/syslogger.h"
+#include "replication/basebackup.h"
+#include "replication/backup_manifest.h"
+#include "replication/walsender.h"
+#include "replication/walsender_private.h"
+#include "storage/bufpage.h"
+#include "storage/checksum.h"
+#include "storage/dsm_impl.h"
+#include "storage/fd.h"
+#include "storage/ipc.h"
+#include "storage/reinit.h"
+#include "utils/builtins.h"
+#include "utils/ps_status.h"
+#include "utils/relcache.h"
+#include "utils/resowner.h"
+#include "utils/timestamp.h"
+
+typedef struct
+{
+	const char *label;
+	bool		progress;
+	bool		fastcheckpoint;
+	bool		nowait;
+	bool		includewal;
+	uint32		maxrate;
+	bool		sendtblspcmapfile;
+	backup_manifest_option manifest;
+	pg_checksum_type manifest_checksum_type;
+} basebackup_options;
+
+static int64 sendTablespace(char *path, char *oid, bool sizeonly,
+							struct backup_manifest_info *manifest);
+static int64 sendDir(const char *path, int basepathlen, bool sizeonly,
+					 List *tablespaces, bool sendtblspclinks,
+					 backup_manifest_info *manifest, const char *spcoid);
+static bool sendFile(const char *readfilename, const char *tarfilename,
+					 struct stat *statbuf, bool missing_ok, Oid dboid,
+					 backup_manifest_info *manifest, const char *spcoid);
+static void sendFileWithContent(const char *filename, const char *content,
+								backup_manifest_info *manifest);
+static int64 _tarWriteHeader(const char *filename, const char *linktarget,
+							 struct stat *statbuf, bool sizeonly);
+static int64 _tarWriteDir(const char *pathbuf, int basepathlen, struct stat *statbuf,
+						  bool sizeonly);
+static void send_int8_string(StringInfoData *buf, int64 intval);
+static void SendBackupHeader(List *tablespaces);
+static void perform_base_backup(basebackup_options *opt);
+static void parse_basebackup_options(List *options, basebackup_options *opt);
+static void SendXlogRecPtrResult(XLogRecPtr ptr, TimeLineID tli);
+static int	compareWalFileNames(const ListCell *a, const ListCell *b);
+static void throttle(size_t increment);
+static void update_basebackup_progress(int64 delta);
+static bool is_checksummed_file(const char *fullpath, const char *filename);
+static int	basebackup_read_file(int fd, char *buf, size_t nbytes, off_t offset,
+								 const char *filename, bool partial_read_ok);
+
+/* Was the backup currently in-progress initiated in recovery mode? */
+static bool backup_started_in_recovery = false;
+
+/* Relative path of temporary statistics directory */
+static char *statrelpath = NULL;
+
+/*
+ * Size of each block sent into the tar stream for larger files.
+ */
+#define TAR_SEND_SIZE 32768
+
+/*
+ * How frequently to throttle, as a fraction of the specified rate-second.
+ */
+#define THROTTLING_FREQUENCY	8
+
+/* The actual number of bytes, transfer of which may cause sleep. */
+static uint64 throttling_sample;
+
+/* Amount of data already transferred but not yet throttled.  */
+static int64 throttling_counter;
+
+/* The minimum time required to transfer throttling_sample bytes. */
+static TimeOffset elapsed_min_unit;
+
+/* The last check of the transfer rate. */
+static TimestampTz throttled_last;
+
+/* The starting XLOG position of the base backup. */
+static XLogRecPtr startptr;
+
+/* Total number of checksum failures during base backup. */
+static long long int total_checksum_failures;
+
+/* Do not verify checksums. */
+static bool noverify_checksums = false;
+
+/*
+ * Total amount of backup data that will be streamed.
+ * -1 means that the size is not estimated.
+ */
+static int64 backup_total = 0;
+
+/* Amount of backup data already streamed */
+static int64 backup_streamed = 0;
+
+/*
+ * Definition of one element part of an exclusion list, used for paths part
+ * of checksum validation or base backups.  "name" is the name of the file
+ * or path to check for exclusion.  If "match_prefix" is true, any items
+ * matching the name as prefix are excluded.
+ */
+struct exclude_list_item
+{
+	const char *name;
+	bool		match_prefix;
+};
+
+/*
+ * The contents of these directories are removed or recreated during server
+ * start so they are not included in backups.  The directories themselves are
+ * kept and included as empty to preserve access permissions.
+ *
+ * Note: this list should be kept in sync with the filter lists in pg_rewind's
+ * filemap.c.
+ */
+static const char *const excludeDirContents[] =
+{
+	/*
+	 * Skip temporary statistics files. PG_STAT_TMP_DIR must be skipped even
+	 * when stats_temp_directory is set because PGSS_TEXT_FILE is always
+	 * created there.
+	 */
+	PG_STAT_TMP_DIR,
+
+	/*
+	 * It is generally not useful to backup the contents of this directory
+	 * even if the intention is to restore to another primary. See backup.sgml
+	 * for a more detailed description.
+	 */
+	"pg_replslot",
+
+	/* Contents removed on startup, see dsm_cleanup_for_mmap(). */
+	PG_DYNSHMEM_DIR,
+
+	/* Contents removed on startup, see AsyncShmemInit(). */
+	"pg_notify",
+
+	/*
+	 * Old contents are loaded for possible debugging but are not required for
+	 * normal operation, see SerialInit().
+	 */
+	"pg_serial",
+
+	/* Contents removed on startup, see DeleteAllExportedSnapshotFiles(). */
+	"pg_snapshots",
+
+	/* Contents zeroed on startup, see StartupSUBTRANS(). */
+	"pg_subtrans",
+
+	/* end of list */
+	NULL
+};
+
+/*
+ * List of files excluded from backups.
+ */
+static const struct exclude_list_item excludeFiles[] =
+{
+	/* Skip auto conf temporary file. */
+	{PG_AUTOCONF_FILENAME ".tmp", false},
+
+	/* Skip current log file temporary file */
+	{LOG_METAINFO_DATAFILE_TMP, false},
+
+	/*
+	 * Skip relation cache because it is rebuilt on startup.  This includes
+	 * temporary files.
+	 */
+	{RELCACHE_INIT_FILENAME, true},
+
+	/*
+	 * If there's a backup_label or tablespace_map file, it belongs to a
+	 * backup started by the user with pg_start_backup().  It is *not* correct
+	 * for this backup.  Our backup_label/tablespace_map is injected into the
+	 * tar separately.
+	 */
+	{BACKUP_LABEL_FILE, false},
+	{TABLESPACE_MAP, false},
+
+	/*
+	 * If there's a backup_manifest, it belongs to a backup that was used to
+	 * start this server. It is *not* correct for this backup. Our
+	 * backup_manifest is injected into the backup separately if users want
+	 * it.
+	 */
+	{"backup_manifest", false},
+
+	{"postmaster.pid", false},
+	{"postmaster.opts", false},
+
+	/* end of list */
+	{NULL, false}
+};
+
+/*
+ * List of files excluded from checksum validation.
+ *
+ * Note: this list should be kept in sync with what pg_checksums.c
+ * includes.
+ */
+static const struct exclude_list_item noChecksumFiles[] = {
+	{"pg_control", false},
+	{"pg_filenode.map", false},
+	{"pg_internal.init", true},
+	{"PG_VERSION", false},
+#ifdef EXEC_BACKEND
+	{"config_exec_params", true},
+#endif
+	{NULL, false}
+};
+
+/*
+ * Actually do a base backup for the specified tablespaces.
+ *
+ * This is split out mainly to avoid complaints about "variable might be
+ * clobbered by longjmp" from stupider versions of gcc.
+ */
+static void
+perform_base_backup(basebackup_options *opt)
+{
+	TimeLineID	starttli;
+	XLogRecPtr	endptr;
+	TimeLineID	endtli;
+	StringInfo	labelfile;
+	StringInfo	tblspc_map_file;
+	backup_manifest_info manifest;
+	int			datadirpathlen;
+	List	   *tablespaces = NIL;
+
+	backup_total = 0;
+	backup_streamed = 0;
+	pgstat_progress_start_command(PROGRESS_COMMAND_BASEBACKUP, InvalidOid);
+
+	/*
+	 * If the estimation of the total backup size is disabled, make the
+	 * backup_total column in the view return NULL by setting the parameter to
+	 * -1.
+	 */
+	if (!opt->progress)
+	{
+		backup_total = -1;
+		pgstat_progress_update_param(PROGRESS_BASEBACKUP_BACKUP_TOTAL,
+									 backup_total);
+	}
+
+	/* we're going to use a BufFile, so we need a ResourceOwner */
+	Assert(CurrentResourceOwner == NULL);
+	CurrentResourceOwner = ResourceOwnerCreate(NULL, "base backup");
+
+	datadirpathlen = strlen(DataDir);
+
+	backup_started_in_recovery = RecoveryInProgress();
+
+	labelfile = makeStringInfo();
+	tblspc_map_file = makeStringInfo();
+	InitializeBackupManifest(&manifest, opt->manifest,
+							 opt->manifest_checksum_type);
+
+	total_checksum_failures = 0;
+
+	pgstat_progress_update_param(PROGRESS_BASEBACKUP_PHASE,
+								 PROGRESS_BASEBACKUP_PHASE_WAIT_CHECKPOINT);
+	startptr = do_pg_start_backup(opt->label, opt->fastcheckpoint, &starttli,
+								  labelfile, &tablespaces,
+								  tblspc_map_file);
+
+	/*
+	 * Once do_pg_start_backup has been called, ensure that any failure causes
+	 * us to abort the backup so we don't "leak" a backup counter. For this
+	 * reason, *all* functionality between do_pg_start_backup() and the end of
+	 * do_pg_stop_backup() should be inside the error cleanup block!
+	 */
+
+	PG_ENSURE_ERROR_CLEANUP(do_pg_abort_backup, BoolGetDatum(false));
+	{
+		ListCell   *lc;
+		tablespaceinfo *ti;
+		int			tblspc_streamed = 0;
+
+		/*
+		 * Calculate the relative path of temporary statistics directory in
+		 * order to skip the files which are located in that directory later.
+		 */
+		if (is_absolute_path(pgstat_stat_directory) &&
+			strncmp(pgstat_stat_directory, DataDir, datadirpathlen) == 0)
+			statrelpath = psprintf("./%s", pgstat_stat_directory + datadirpathlen + 1);
+		else if (strncmp(pgstat_stat_directory, "./", 2) != 0)
+			statrelpath = psprintf("./%s", pgstat_stat_directory);
+		else
+			statrelpath = pgstat_stat_directory;
+
+		/* Add a node for the base directory at the end */
+		ti = palloc0(sizeof(tablespaceinfo));
+		ti->size = -1;
+		tablespaces = lappend(tablespaces, ti);
+
+		/*
+		 * Calculate the total backup size by summing up the size of each
+		 * tablespace
+		 */
+		if (opt->progress)
+		{
+			pgstat_progress_update_param(PROGRESS_BASEBACKUP_PHASE,
+										 PROGRESS_BASEBACKUP_PHASE_ESTIMATE_BACKUP_SIZE);
+
+			foreach(lc, tablespaces)
+			{
+				tablespaceinfo *tmp = (tablespaceinfo *) lfirst(lc);
+
+				if (tmp->path == NULL)
+					tmp->size = sendDir(".", 1, true, tablespaces, true, NULL,
+										NULL);
+				else
+					tmp->size = sendTablespace(tmp->path, tmp->oid, true,
+											   NULL);
+				backup_total += tmp->size;
+			}
+		}
+
+		/* Report that we are now streaming database files as a base backup */
+		{
+			const int	index[] = {
+				PROGRESS_BASEBACKUP_PHASE,
+				PROGRESS_BASEBACKUP_BACKUP_TOTAL,
+				PROGRESS_BASEBACKUP_TBLSPC_TOTAL
+			};
+			const int64 val[] = {
+				PROGRESS_BASEBACKUP_PHASE_STREAM_BACKUP,
+				backup_total, list_length(tablespaces)
+			};
+
+			pgstat_progress_update_multi_param(3, index, val);
+		}
+
+		/* Send the starting position of the backup */
+		SendXlogRecPtrResult(startptr, starttli);
+
+		/* Send tablespace header */
+		SendBackupHeader(tablespaces);
+
+		/* Setup and activate network throttling, if client requested it */
+		if (opt->maxrate > 0)
+		{
+			throttling_sample =
+				(int64) opt->maxrate * (int64) 1024 / THROTTLING_FREQUENCY;
+
+			/*
+			 * The minimum amount of time for throttling_sample bytes to be
+			 * transferred.
+			 */
+			elapsed_min_unit = USECS_PER_SEC / THROTTLING_FREQUENCY;
+
+			/* Enable throttling. */
+			throttling_counter = 0;
+
+			/* The 'real data' starts now (header was ignored). */
+			throttled_last = GetCurrentTimestamp();
+		}
+		else
+		{
+			/* Disable throttling. */
+			throttling_counter = -1;
+		}
+
+		/* Send off our tablespaces one by one */
+		foreach(lc, tablespaces)
+		{
+			tablespaceinfo *ti = (tablespaceinfo *) lfirst(lc);
+			StringInfoData buf;
+
+			/* Send CopyOutResponse message */
+			pq_beginmessage(&buf, 'H');
+			pq_sendbyte(&buf, 0);	/* overall format */
+			pq_sendint16(&buf, 0);	/* natts */
+			pq_endmessage(&buf);
+
+			if (ti->path == NULL)
+			{
+				struct stat statbuf;
+				bool		sendtblspclinks = true;
+
+				/* In the main tar, include the backup_label first... */
+				sendFileWithContent(BACKUP_LABEL_FILE, labelfile->data,
+									&manifest);
+
+				/* Then the tablespace_map file, if required... */
+				if (opt->sendtblspcmapfile)
+				{
+					sendFileWithContent(TABLESPACE_MAP, tblspc_map_file->data,
+										&manifest);
+					sendtblspclinks = false;
+				}
+
+				/* Then the bulk of the files... */
+				sendDir(".", 1, false, tablespaces, sendtblspclinks,
+						&manifest, NULL);
+
+				/* ... and pg_control after everything else. */
+				if (lstat(XLOG_CONTROL_FILE, &statbuf) != 0)
+					ereport(ERROR,
+							(errcode_for_file_access(),
+							 errmsg("could not stat file \"%s\": %m",
+									XLOG_CONTROL_FILE)));
+				sendFile(XLOG_CONTROL_FILE, XLOG_CONTROL_FILE, &statbuf,
+						 false, InvalidOid, &manifest, NULL);
+			}
+			else
+				sendTablespace(ti->path, ti->oid, false, &manifest);
+
+			/*
+			 * If we're including WAL, and this is the main data directory we
+			 * don't terminate the tar stream here. Instead, we will append
+			 * the xlog files below and terminate it then. This is safe since
+			 * the main data directory is always sent *last*.
+			 */
+			if (opt->includewal && ti->path == NULL)
+			{
+				Assert(lnext(tablespaces, lc) == NULL);
+			}
+			else
+				pq_putemptymessage('c');	/* CopyDone */
+
+			tblspc_streamed++;
+			pgstat_progress_update_param(PROGRESS_BASEBACKUP_TBLSPC_STREAMED,
+										 tblspc_streamed);
+		}
+
+		pgstat_progress_update_param(PROGRESS_BASEBACKUP_PHASE,
+									 PROGRESS_BASEBACKUP_PHASE_WAIT_WAL_ARCHIVE);
+		endptr = do_pg_stop_backup(labelfile->data, !opt->nowait, &endtli);
+	}
+	PG_END_ENSURE_ERROR_CLEANUP(do_pg_abort_backup, BoolGetDatum(false));
+
+
+	if (opt->includewal)
+	{
+		/*
+		 * We've left the last tar file "open", so we can now append the
+		 * required WAL files to it.
+		 */
+		char		pathbuf[MAXPGPATH];
+		XLogSegNo	segno;
+		XLogSegNo	startsegno;
+		XLogSegNo	endsegno;
+		struct stat statbuf;
+		List	   *historyFileList = NIL;
+		List	   *walFileList = NIL;
+		char		firstoff[MAXFNAMELEN];
+		char		lastoff[MAXFNAMELEN];
+		DIR		   *dir;
+		struct dirent *de;
+		ListCell   *lc;
+		TimeLineID	tli;
+
+		pgstat_progress_update_param(PROGRESS_BASEBACKUP_PHASE,
+									 PROGRESS_BASEBACKUP_PHASE_TRANSFER_WAL);
+
+		/*
+		 * I'd rather not worry about timelines here, so scan pg_wal and
+		 * include all WAL files in the range between 'startptr' and 'endptr',
+		 * regardless of the timeline the file is stamped with. If there are
+		 * some spurious WAL files belonging to timelines that don't belong in
+		 * this server's history, they will be included too. Normally there
+		 * shouldn't be such files, but if there are, there's little harm in
+		 * including them.
+		 */
+		XLByteToSeg(startptr, startsegno, wal_segment_size);
+		XLogFileName(firstoff, ThisTimeLineID, startsegno, wal_segment_size);
+		XLByteToPrevSeg(endptr, endsegno, wal_segment_size);
+		XLogFileName(lastoff, ThisTimeLineID, endsegno, wal_segment_size);
+
+		dir = AllocateDir("pg_wal");
+		while ((de = ReadDir(dir, "pg_wal")) != NULL)
+		{
+			/* Does it look like a WAL segment, and is it in the range? */
+			if (IsXLogFileName(de->d_name) &&
+				strcmp(de->d_name + 8, firstoff + 8) >= 0 &&
+				strcmp(de->d_name + 8, lastoff + 8) <= 0)
+			{
+				walFileList = lappend(walFileList, pstrdup(de->d_name));
+			}
+			/* Does it look like a timeline history file? */
+			else if (IsTLHistoryFileName(de->d_name))
+			{
+				historyFileList = lappend(historyFileList, pstrdup(de->d_name));
+			}
+		}
+		FreeDir(dir);
+
+		/*
+		 * Before we go any further, check that none of the WAL segments we
+		 * need were removed.
+		 */
+		CheckXLogRemoved(startsegno, ThisTimeLineID);
+
+		/*
+		 * Sort the WAL filenames.  We want to send the files in order from
+		 * oldest to newest, to reduce the chance that a file is recycled
+		 * before we get a chance to send it over.
+		 */
+		list_sort(walFileList, compareWalFileNames);
+
+		/*
+		 * There must be at least one xlog file in the pg_wal directory, since
+		 * we are doing backup-including-xlog.
+		 */
+		if (walFileList == NIL)
+			ereport(ERROR,
+					(errmsg("could not find any WAL files")));
+
+		/*
+		 * Sanity check: the first and last segment should cover startptr and
+		 * endptr, with no gaps in between.
+		 */
+		XLogFromFileName((char *) linitial(walFileList),
+						 &tli, &segno, wal_segment_size);
+		if (segno != startsegno)
+		{
+			char		startfname[MAXFNAMELEN];
+
+			XLogFileName(startfname, ThisTimeLineID, startsegno,
+						 wal_segment_size);
+			ereport(ERROR,
+					(errmsg("could not find WAL file \"%s\"", startfname)));
+		}
+		foreach(lc, walFileList)
+		{
+			char	   *walFileName = (char *) lfirst(lc);
+			XLogSegNo	currsegno = segno;
+			XLogSegNo	nextsegno = segno + 1;
+
+			XLogFromFileName(walFileName, &tli, &segno, wal_segment_size);
+			if (!(nextsegno == segno || currsegno == segno))
+			{
+				char		nextfname[MAXFNAMELEN];
+
+				XLogFileName(nextfname, ThisTimeLineID, nextsegno,
+							 wal_segment_size);
+				ereport(ERROR,
+						(errmsg("could not find WAL file \"%s\"", nextfname)));
+			}
+		}
+		if (segno != endsegno)
+		{
+			char		endfname[MAXFNAMELEN];
+
+			XLogFileName(endfname, ThisTimeLineID, endsegno, wal_segment_size);
+			ereport(ERROR,
+					(errmsg("could not find WAL file \"%s\"", endfname)));
+		}
+
+		/* Ok, we have everything we need. Send the WAL files. */
+		foreach(lc, walFileList)
+		{
+			char	   *walFileName = (char *) lfirst(lc);
+			int			fd;
+			char		buf[TAR_SEND_SIZE];
+			size_t		cnt;
+			pgoff_t		len = 0;
+
+			snprintf(pathbuf, MAXPGPATH, XLOGDIR "/%s", walFileName);
+			XLogFromFileName(walFileName, &tli, &segno, wal_segment_size);
+
+			fd = OpenTransientFile(pathbuf, O_RDONLY | PG_BINARY);
+			if (fd < 0)
+			{
+				int			save_errno = errno;
+
+				/*
+				 * Most likely reason for this is that the file was already
+				 * removed by a checkpoint, so check for that to get a better
+				 * error message.
+				 */
+				CheckXLogRemoved(segno, tli);
+
+				errno = save_errno;
+				ereport(ERROR,
+						(errcode_for_file_access(),
+						 errmsg("could not open file \"%s\": %m", pathbuf)));
+			}
+
+			if (fstat(fd, &statbuf) != 0)
+				ereport(ERROR,
+						(errcode_for_file_access(),
+						 errmsg("could not stat file \"%s\": %m",
+								pathbuf)));
+			if (statbuf.st_size != wal_segment_size)
+			{
+				CheckXLogRemoved(segno, tli);
+				ereport(ERROR,
+						(errcode_for_file_access(),
+						 errmsg("unexpected WAL file size \"%s\"", walFileName)));
+			}
+
+			/* send the WAL file itself */
+			_tarWriteHeader(pathbuf, NULL, &statbuf, false);
+
+			while ((cnt = basebackup_read_file(fd, buf,
+											   Min(sizeof(buf),
+												   wal_segment_size - len),
+											   len, pathbuf, true)) > 0)
+			{
+				CheckXLogRemoved(segno, tli);
+				/* Send the chunk as a CopyData message */
+				if (pq_putmessage('d', buf, cnt))
+					ereport(ERROR,
+							(errmsg("base backup could not send data, aborting backup")));
+				update_basebackup_progress(cnt);
+
+				len += cnt;
+				throttle(cnt);
+
+				if (len == wal_segment_size)
+					break;
+			}
+
+			if (len != wal_segment_size)
+			{
+				CheckXLogRemoved(segno, tli);
+				ereport(ERROR,
+						(errcode_for_file_access(),
+						 errmsg("unexpected WAL file size \"%s\"", walFileName)));
+			}
+
+			/*
+			 * wal_segment_size is a multiple of TAR_BLOCK_SIZE, so no need
+			 * for padding.
+			 */
+			Assert(wal_segment_size % TAR_BLOCK_SIZE == 0);
+
+			CloseTransientFile(fd);
+
+			/*
+			 * Mark file as archived, otherwise files can get archived again
+			 * after promotion of a new node. This is in line with
+			 * walreceiver.c always doing an XLogArchiveForceDone() after a
+			 * complete segment.
+			 */
+			StatusFilePath(pathbuf, walFileName, ".done");
+			sendFileWithContent(pathbuf, "", &manifest);
+		}
+
+		/*
+		 * Send timeline history files too. Only the latest timeline history
+		 * file is required for recovery, and even that only if there happens
+		 * to be a timeline switch in the first WAL segment that contains the
+		 * checkpoint record, or if we're taking a base backup from a standby
+		 * server and the target timeline changes while the backup is taken.
+		 * But they are small and highly useful for debugging purposes, so
+		 * better include them all, always.
+		 */
+		foreach(lc, historyFileList)
+		{
+			char	   *fname = lfirst(lc);
+
+			snprintf(pathbuf, MAXPGPATH, XLOGDIR "/%s", fname);
+
+			if (lstat(pathbuf, &statbuf) != 0)
+				ereport(ERROR,
+						(errcode_for_file_access(),
+						 errmsg("could not stat file \"%s\": %m", pathbuf)));
+
+			sendFile(pathbuf, pathbuf, &statbuf, false, InvalidOid,
+					 &manifest, NULL);
+
+			/* unconditionally mark file as archived */
+			StatusFilePath(pathbuf, fname, ".done");
+			sendFileWithContent(pathbuf, "", &manifest);
+		}
+
+		/* Send CopyDone message for the last tar file */
+		pq_putemptymessage('c');
+	}
+
+	AddWALInfoToBackupManifest(&manifest, startptr, starttli, endptr, endtli);
+
+	SendBackupManifest(&manifest);
+
+	SendXlogRecPtrResult(endptr, endtli);
+
+	if (total_checksum_failures)
+	{
+		if (total_checksum_failures > 1)
+			ereport(WARNING,
+					(errmsg_plural("%lld total checksum verification failure",
+								   "%lld total checksum verification failures",
+								   total_checksum_failures,
+								   total_checksum_failures)));
+
+		ereport(ERROR,
+				(errcode(ERRCODE_DATA_CORRUPTED),
+				 errmsg("checksum verification failure during base backup")));
+	}
+
+	/*
+	 * Make sure to free the manifest before the resource owners as manifests
+	 * use cryptohash contexts that may depend on resource owners (like
+	 * OpenSSL).
+	 */
+	FreeBackupManifest(&manifest);
+
+	/* clean up the resource owner we created */
+	WalSndResourceCleanup(true);
+
+	pgstat_progress_end_command();
+}
+
+/*
+ * list_sort comparison function, to compare log/seg portion of WAL segment
+ * filenames, ignoring the timeline portion.
+ */
+static int
+compareWalFileNames(const ListCell *a, const ListCell *b)
+{
+	char	   *fna = (char *) lfirst(a);
+	char	   *fnb = (char *) lfirst(b);
+
+	return strcmp(fna + 8, fnb + 8);
+}
+
+/*
+ * Parse the base backup options passed down by the parser
+ */
+static void
+parse_basebackup_options(List *options, basebackup_options *opt)
+{
+	ListCell   *lopt;
+	bool		o_label = false;
+	bool		o_progress = false;
+	bool		o_fast = false;
+	bool		o_nowait = false;
+	bool		o_wal = false;
+	bool		o_maxrate = false;
+	bool		o_tablespace_map = false;
+	bool		o_noverify_checksums = false;
+	bool		o_manifest = false;
+	bool		o_manifest_checksums = false;
+
+	MemSet(opt, 0, sizeof(*opt));
+	opt->manifest = MANIFEST_OPTION_NO;
+	opt->manifest_checksum_type = CHECKSUM_TYPE_CRC32C;
+
+	foreach(lopt, options)
+	{
+		DefElem    *defel = (DefElem *) lfirst(lopt);
+
+		if (strcmp(defel->defname, "label") == 0)
+		{
+			if (o_label)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("duplicate option \"%s\"", defel->defname)));
+			opt->label = strVal(defel->arg);
+			o_label = true;
+		}
+		else if (strcmp(defel->defname, "progress") == 0)
+		{
+			if (o_progress)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("duplicate option \"%s\"", defel->defname)));
+			opt->progress = true;
+			o_progress = true;
+		}
+		else if (strcmp(defel->defname, "fast") == 0)
+		{
+			if (o_fast)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("duplicate option \"%s\"", defel->defname)));
+			opt->fastcheckpoint = true;
+			o_fast = true;
+		}
+		else if (strcmp(defel->defname, "nowait") == 0)
+		{
+			if (o_nowait)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("duplicate option \"%s\"", defel->defname)));
+			opt->nowait = true;
+			o_nowait = true;
+		}
+		else if (strcmp(defel->defname, "wal") == 0)
+		{
+			if (o_wal)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("duplicate option \"%s\"", defel->defname)));
+			opt->includewal = true;
+			o_wal = true;
+		}
+		else if (strcmp(defel->defname, "max_rate") == 0)
+		{
+			long		maxrate;
+
+			if (o_maxrate)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("duplicate option \"%s\"", defel->defname)));
+
+			maxrate = intVal(defel->arg);
+			if (maxrate < MAX_RATE_LOWER || maxrate > MAX_RATE_UPPER)
+				ereport(ERROR,
+						(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+						 errmsg("%d is outside the valid range for parameter \"%s\" (%d .. %d)",
+								(int) maxrate, "MAX_RATE", MAX_RATE_LOWER, MAX_RATE_UPPER)));
+
+			opt->maxrate = (uint32) maxrate;
+			o_maxrate = true;
+		}
+		else if (strcmp(defel->defname, "tablespace_map") == 0)
+		{
+			if (o_tablespace_map)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("duplicate option \"%s\"", defel->defname)));
+			opt->sendtblspcmapfile = true;
+			o_tablespace_map = true;
+		}
+		else if (strcmp(defel->defname, "noverify_checksums") == 0)
+		{
+			if (o_noverify_checksums)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("duplicate option \"%s\"", defel->defname)));
+			noverify_checksums = true;
+			o_noverify_checksums = true;
+		}
+		else if (strcmp(defel->defname, "manifest") == 0)
+		{
+			char	   *optval = strVal(defel->arg);
+			bool		manifest_bool;
+
+			if (o_manifest)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("duplicate option \"%s\"", defel->defname)));
+			if (parse_bool(optval, &manifest_bool))
+			{
+				if (manifest_bool)
+					opt->manifest = MANIFEST_OPTION_YES;
+				else
+					opt->manifest = MANIFEST_OPTION_NO;
+			}
+			else if (pg_strcasecmp(optval, "force-encode") == 0)
+				opt->manifest = MANIFEST_OPTION_FORCE_ENCODE;
+			else
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("unrecognized manifest option: \"%s\"",
+								optval)));
+			o_manifest = true;
+		}
+		else if (strcmp(defel->defname, "manifest_checksums") == 0)
+		{
+			char	   *optval = strVal(defel->arg);
+
+			if (o_manifest_checksums)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("duplicate option \"%s\"", defel->defname)));
+			if (!pg_checksum_parse_type(optval,
+										&opt->manifest_checksum_type))
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("unrecognized checksum algorithm: \"%s\"",
+								optval)));
+			o_manifest_checksums = true;
+		}
+		else
+			elog(ERROR, "option \"%s\" not recognized",
+				 defel->defname);
+	}
+	if (opt->label == NULL)
+		opt->label = "base backup";
+	if (opt->manifest == MANIFEST_OPTION_NO)
+	{
+		if (o_manifest_checksums)
+			ereport(ERROR,
+					(errcode(ERRCODE_SYNTAX_ERROR),
+					 errmsg("manifest checksums require a backup manifest")));
+		opt->manifest_checksum_type = CHECKSUM_TYPE_NONE;
+	}
+}
+
+
+/*
+ * SendBaseBackup() - send a complete base backup.
+ *
+ * The function will put the system into backup mode like pg_start_backup()
+ * does, so that the backup is consistent even though we read directly from
+ * the filesystem, bypassing the buffer cache.
+ */
+void
+SendBaseBackup(BaseBackupCmd *cmd)
+{
+	basebackup_options opt;
+	SessionBackupState status = get_backup_status();
+
+	if (status == SESSION_BACKUP_NON_EXCLUSIVE)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("a backup is already in progress in this session")));
+
+	parse_basebackup_options(cmd->options, &opt);
+
+	WalSndSetState(WALSNDSTATE_BACKUP);
+
+	if (update_process_title)
+	{
+		char		activitymsg[50];
+
+		snprintf(activitymsg, sizeof(activitymsg), "sending backup \"%s\"",
+				 opt.label);
+		set_ps_display(activitymsg);
+	}
+
+	perform_base_backup(&opt);
+}
+
+static void
+send_int8_string(StringInfoData *buf, int64 intval)
+{
+	char		is[32];
+
+	sprintf(is, INT64_FORMAT, intval);
+	pq_sendint32(buf, strlen(is));
+	pq_sendbytes(buf, is, strlen(is));
+}
+
+static void
+SendBackupHeader(List *tablespaces)
+{
+	StringInfoData buf;
+	ListCell   *lc;
+
+	/* Construct and send the directory information */
+	pq_beginmessage(&buf, 'T'); /* RowDescription */
+	pq_sendint16(&buf, 3);		/* 3 fields */
+
+	/* First field - spcoid */
+	pq_sendstring(&buf, "spcoid");
+	pq_sendint32(&buf, 0);		/* table oid */
+	pq_sendint16(&buf, 0);		/* attnum */
+	pq_sendint32(&buf, OIDOID); /* type oid */
+	pq_sendint16(&buf, 4);		/* typlen */
+	pq_sendint32(&buf, 0);		/* typmod */
+	pq_sendint16(&buf, 0);		/* format code */
+
+	/* Second field - spclocation */
+	pq_sendstring(&buf, "spclocation");
+	pq_sendint32(&buf, 0);
+	pq_sendint16(&buf, 0);
+	pq_sendint32(&buf, TEXTOID);
+	pq_sendint16(&buf, -1);
+	pq_sendint32(&buf, 0);
+	pq_sendint16(&buf, 0);
+
+	/* Third field - size */
+	pq_sendstring(&buf, "size");
+	pq_sendint32(&buf, 0);
+	pq_sendint16(&buf, 0);
+	pq_sendint32(&buf, INT8OID);
+	pq_sendint16(&buf, 8);
+	pq_sendint32(&buf, 0);
+	pq_sendint16(&buf, 0);
+	pq_endmessage(&buf);
+
+	foreach(lc, tablespaces)
+	{
+		tablespaceinfo *ti = lfirst(lc);
+
+		/* Send one datarow message */
+		pq_beginmessage(&buf, 'D');
+		pq_sendint16(&buf, 3);	/* number of columns */
+		if (ti->path == NULL)
+		{
+			pq_sendint32(&buf, -1); /* Length = -1 ==> NULL */
+			pq_sendint32(&buf, -1);
+		}
+		else
+		{
+			Size		len;
+
+			len = strlen(ti->oid);
+			pq_sendint32(&buf, len);
+			pq_sendbytes(&buf, ti->oid, len);
+
+			len = strlen(ti->path);
+			pq_sendint32(&buf, len);
+			pq_sendbytes(&buf, ti->path, len);
+		}
+		if (ti->size >= 0)
+			send_int8_string(&buf, ti->size / 1024);
+		else
+			pq_sendint32(&buf, -1); /* NULL */
+
+		pq_endmessage(&buf);
+	}
+
+	/* Send a CommandComplete message */
+	pq_puttextmessage('C', "SELECT");
+}
+
+/*
+ * Send a single resultset containing just a single
+ * XLogRecPtr record (in text format)
+ */
+static void
+SendXlogRecPtrResult(XLogRecPtr ptr, TimeLineID tli)
+{
+	StringInfoData buf;
+	char		str[MAXFNAMELEN];
+	Size		len;
+
+	pq_beginmessage(&buf, 'T'); /* RowDescription */
+	pq_sendint16(&buf, 2);		/* 2 fields */
+
+	/* Field headers */
+	pq_sendstring(&buf, "recptr");
+	pq_sendint32(&buf, 0);		/* table oid */
+	pq_sendint16(&buf, 0);		/* attnum */
+	pq_sendint32(&buf, TEXTOID);	/* type oid */
+	pq_sendint16(&buf, -1);
+	pq_sendint32(&buf, 0);
+	pq_sendint16(&buf, 0);
+
+	pq_sendstring(&buf, "tli");
+	pq_sendint32(&buf, 0);		/* table oid */
+	pq_sendint16(&buf, 0);		/* attnum */
+
+	/*
+	 * int8 may seem like a surprising data type for this, but in theory int4
+	 * would not be wide enough for this, as TimeLineID is unsigned.
+	 */
+	pq_sendint32(&buf, INT8OID);	/* type oid */
+	pq_sendint16(&buf, -1);
+	pq_sendint32(&buf, 0);
+	pq_sendint16(&buf, 0);
+	pq_endmessage(&buf);
+
+	/* Data row */
+	pq_beginmessage(&buf, 'D');
+	pq_sendint16(&buf, 2);		/* number of columns */
+
+	len = snprintf(str, sizeof(str),
+				   "%X/%X", LSN_FORMAT_ARGS(ptr));
+	pq_sendint32(&buf, len);
+	pq_sendbytes(&buf, str, len);
+
+	len = snprintf(str, sizeof(str), "%u", tli);
+	pq_sendint32(&buf, len);
+	pq_sendbytes(&buf, str, len);
+
+	pq_endmessage(&buf);
+
+	/* Send a CommandComplete message */
+	pq_puttextmessage('C', "SELECT");
+}
+
+/*
+ * Inject a file with given name and content in the output tar stream.
+ */
+static void
+sendFileWithContent(const char *filename, const char *content,
+					backup_manifest_info *manifest)
+{
+	struct stat statbuf;
+	int			pad,
+				len;
+	pg_checksum_context checksum_ctx;
+
+	if (pg_checksum_init(&checksum_ctx, manifest->checksum_type) < 0)
+		elog(ERROR, "could not initialize checksum of file \"%s\"",
+			 filename);
+
+	len = strlen(content);
+
+	/*
+	 * Construct a stat struct for the backup_label file we're injecting in
+	 * the tar.
+	 */
+	/* Windows doesn't have the concept of uid and gid */
+#ifdef WIN32
+	statbuf.st_uid = 0;
+	statbuf.st_gid = 0;
+#else
+	statbuf.st_uid = geteuid();
+	statbuf.st_gid = getegid();
+#endif
+	statbuf.st_mtime = time(NULL);
+	statbuf.st_mode = pg_file_create_mode;
+	statbuf.st_size = len;
+
+	_tarWriteHeader(filename, NULL, &statbuf, false);
+	/* Send the contents as a CopyData message */
+	pq_putmessage('d', content, len);
+	update_basebackup_progress(len);
+
+	/* Pad to a multiple of the tar block size. */
+	pad = tarPaddingBytesRequired(len);
+	if (pad > 0)
+	{
+		char		buf[TAR_BLOCK_SIZE];
+
+		MemSet(buf, 0, pad);
+		pq_putmessage('d', buf, pad);
+		update_basebackup_progress(pad);
+	}
+
+	if (pg_checksum_update(&checksum_ctx, (uint8 *) content, len) < 0)
+		elog(ERROR, "could not update checksum of file \"%s\"",
+			 filename);
+
+	AddFileToBackupManifest(manifest, NULL, filename, len,
+							(pg_time_t) statbuf.st_mtime, &checksum_ctx);
+}
+
+/*
+ * Include the tablespace directory pointed to by 'path' in the output tar
+ * stream.  If 'sizeonly' is true, we just calculate a total length and return
+ * it, without actually sending anything.
+ *
+ * Only used to send auxiliary tablespaces, not PGDATA.
+ */
+static int64
+sendTablespace(char *path, char *spcoid, bool sizeonly,
+			   backup_manifest_info *manifest)
+{
+	int64		size;
+	char		pathbuf[MAXPGPATH];
+	struct stat statbuf;
+
+	/*
+	 * 'path' points to the tablespace location, but we only want to include
+	 * the version directory in it that belongs to us.
+	 */
+	snprintf(pathbuf, sizeof(pathbuf), "%s/%s", path,
+			 TABLESPACE_VERSION_DIRECTORY);
+
+	/*
+	 * Store a directory entry in the tar file so we get the permissions
+	 * right.
+	 */
+	if (lstat(pathbuf, &statbuf) != 0)
+	{
+		if (errno != ENOENT)
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not stat file or directory \"%s\": %m",
+							pathbuf)));
+
+		/* If the tablespace went away while scanning, it's no error. */
+		return 0;
+	}
+
+	size = _tarWriteHeader(TABLESPACE_VERSION_DIRECTORY, NULL, &statbuf,
+						   sizeonly);
+
+	/* Send all the files in the tablespace version directory */
+	size += sendDir(pathbuf, strlen(path), sizeonly, NIL, true, manifest,
+					spcoid);
+
+	return size;
+}
+
+/*
+ * Include all files from the given directory in the output tar stream. If
+ * 'sizeonly' is true, we just calculate a total length and return it, without
+ * actually sending anything.
+ *
+ * Omit any directory in the tablespaces list, to avoid backing up
+ * tablespaces twice when they were created inside PGDATA.
+ *
+ * If sendtblspclinks is true, we need to include symlink
+ * information in the tar file. If not, we can skip that
+ * as it will be sent separately in the tablespace_map file.
+ */
+static int64
+sendDir(const char *path, int basepathlen, bool sizeonly, List *tablespaces,
+		bool sendtblspclinks, backup_manifest_info *manifest,
+		const char *spcoid)
+{
+	DIR		   *dir;
+	struct dirent *de;
+	char		pathbuf[MAXPGPATH * 2];
+	struct stat statbuf;
+	int64		size = 0;
+	const char *lastDir;		/* Split last dir from parent path. */
+	bool		isDbDir = false;	/* Does this directory contain relations? */
+
+	/*
+	 * Determine if the current path is a database directory that can contain
+	 * relations.
+	 *
+	 * Start by finding the location of the delimiter between the parent path
+	 * and the current path.
+	 */
+	lastDir = last_dir_separator(path);
+
+	/* Does this path look like a database path (i.e. all digits)? */
+	if (lastDir != NULL &&
+		strspn(lastDir + 1, "0123456789") == strlen(lastDir + 1))
+	{
+		/* Part of path that contains the parent directory. */
+		int			parentPathLen = lastDir - path;
+
+		/*
+		 * Mark path as a database directory if the parent path is either
+		 * $PGDATA/base or a tablespace version path.
+		 */
+		if (strncmp(path, "./base", parentPathLen) == 0 ||
+			(parentPathLen >= (sizeof(TABLESPACE_VERSION_DIRECTORY) - 1) &&
+			 strncmp(lastDir - (sizeof(TABLESPACE_VERSION_DIRECTORY) - 1),
+					 TABLESPACE_VERSION_DIRECTORY,
+					 sizeof(TABLESPACE_VERSION_DIRECTORY) - 1) == 0))
+			isDbDir = true;
+	}
+
+	dir = AllocateDir(path);
+	while ((de = ReadDir(dir, path)) != NULL)
+	{
+		int			excludeIdx;
+		bool		excludeFound;
+		ForkNumber	relForkNum; /* Type of fork if file is a relation */
+		int			relOidChars;	/* Chars in filename that are the rel oid */
+
+		/* Skip special stuff */
+		if (strcmp(de->d_name, ".") == 0 || strcmp(de->d_name, "..") == 0)
+			continue;
+
+		/* Skip temporary files */
+		if (strncmp(de->d_name,
+					PG_TEMP_FILE_PREFIX,
+					strlen(PG_TEMP_FILE_PREFIX)) == 0)
+			continue;
+
+		/*
+		 * Check if the postmaster has signaled us to exit, and abort with an
+		 * error in that case. The error handler further up will call
+		 * do_pg_abort_backup() for us. Also check that if the backup was
+		 * started while still in recovery, the server wasn't promoted.
+		 * do_pg_stop_backup() will check that too, but it's better to stop
+		 * the backup early than continue to the end and fail there.
+		 */
+		CHECK_FOR_INTERRUPTS();
+		if (RecoveryInProgress() != backup_started_in_recovery)
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					 errmsg("the standby was promoted during online backup"),
+					 errhint("This means that the backup being taken is corrupt "
+							 "and should not be used. "
+							 "Try taking another online backup.")));
+
+		/* Scan for files that should be excluded */
+		excludeFound = false;
+		for (excludeIdx = 0; excludeFiles[excludeIdx].name != NULL; excludeIdx++)
+		{
+			int			cmplen = strlen(excludeFiles[excludeIdx].name);
+
+			if (!excludeFiles[excludeIdx].match_prefix)
+				cmplen++;
+			if (strncmp(de->d_name, excludeFiles[excludeIdx].name, cmplen) == 0)
+			{
+				elog(DEBUG1, "file \"%s\" excluded from backup", de->d_name);
+				excludeFound = true;
+				break;
+			}
+		}
+
+		if (excludeFound)
+			continue;
+
+		/* Exclude all forks for unlogged tables except the init fork */
+		if (isDbDir &&
+			parse_filename_for_nontemp_relation(de->d_name, &relOidChars,
+												&relForkNum))
+		{
+			/* Never exclude init forks */
+			if (relForkNum != INIT_FORKNUM)
+			{
+				char		initForkFile[MAXPGPATH];
+				char		relOid[OIDCHARS + 1];
+
+				/*
+				 * If any other type of fork, check if there is an init fork
+				 * with the same OID. If so, the file can be excluded.
+				 */
+				memcpy(relOid, de->d_name, relOidChars);
+				relOid[relOidChars] = '\0';
+				snprintf(initForkFile, sizeof(initForkFile), "%s/%s_init",
+						 path, relOid);
+
+				if (lstat(initForkFile, &statbuf) == 0)
+				{
+					elog(DEBUG2,
+						 "unlogged relation file \"%s\" excluded from backup",
+						 de->d_name);
+
+					continue;
+				}
+			}
+		}
+
+		/* Exclude temporary relations */
+		if (isDbDir && looks_like_temp_rel_name(de->d_name))
+		{
+			elog(DEBUG2,
+				 "temporary relation file \"%s\" excluded from backup",
+				 de->d_name);
+
+			continue;
+		}
+
+		snprintf(pathbuf, sizeof(pathbuf), "%s/%s", path, de->d_name);
+
+		/* Skip pg_control here to back up it last */
+		if (strcmp(pathbuf, "./global/pg_control") == 0)
+			continue;
+
+		if (lstat(pathbuf, &statbuf) != 0)
+		{
+			if (errno != ENOENT)
+				ereport(ERROR,
+						(errcode_for_file_access(),
+						 errmsg("could not stat file or directory \"%s\": %m",
+								pathbuf)));
+
+			/* If the file went away while scanning, it's not an error. */
+			continue;
+		}
+
+		/* Scan for directories whose contents should be excluded */
+		excludeFound = false;
+		for (excludeIdx = 0; excludeDirContents[excludeIdx] != NULL; excludeIdx++)
+		{
+			if (strcmp(de->d_name, excludeDirContents[excludeIdx]) == 0)
+			{
+				elog(DEBUG1, "contents of directory \"%s\" excluded from backup", de->d_name);
+				size += _tarWriteDir(pathbuf, basepathlen, &statbuf, sizeonly);
+				excludeFound = true;
+				break;
+			}
+		}
+
+		if (excludeFound)
+			continue;
+
+		/*
+		 * Exclude contents of directory specified by statrelpath if not set
+		 * to the default (pg_stat_tmp) which is caught in the loop above.
+		 */
+		if (statrelpath != NULL && strcmp(pathbuf, statrelpath) == 0)
+		{
+			elog(DEBUG1, "contents of directory \"%s\" excluded from backup", statrelpath);
+			size += _tarWriteDir(pathbuf, basepathlen, &statbuf, sizeonly);
+			continue;
+		}
+
+		/*
+		 * We can skip pg_wal, the WAL segments need to be fetched from the
+		 * WAL archive anyway. But include it as an empty directory anyway, so
+		 * we get permissions right.
+		 */
+		if (strcmp(pathbuf, "./pg_wal") == 0)
+		{
+			/* If pg_wal is a symlink, write it as a directory anyway */
+			size += _tarWriteDir(pathbuf, basepathlen, &statbuf, sizeonly);
+
+			/*
+			 * Also send archive_status directory (by hackishly reusing
+			 * statbuf from above ...).
+			 */
+			size += _tarWriteHeader("./pg_wal/archive_status", NULL, &statbuf,
+									sizeonly);
+
+			continue;			/* don't recurse into pg_wal */
+		}
+
+		/* Allow symbolic links in pg_tblspc only */
+		if (strcmp(path, "./pg_tblspc") == 0 &&
+#ifndef WIN32
+			S_ISLNK(statbuf.st_mode)
+#else
+			pgwin32_is_junction(pathbuf)
+#endif
+			)
+		{
+#if defined(HAVE_READLINK) || defined(WIN32)
+			char		linkpath[MAXPGPATH];
+			int			rllen;
+
+			rllen = readlink(pathbuf, linkpath, sizeof(linkpath));
+			if (rllen < 0)
+				ereport(ERROR,
+						(errcode_for_file_access(),
+						 errmsg("could not read symbolic link \"%s\": %m",
+								pathbuf)));
+			if (rllen >= sizeof(linkpath))
+				ereport(ERROR,
+						(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+						 errmsg("symbolic link \"%s\" target is too long",
+								pathbuf)));
+			linkpath[rllen] = '\0';
+
+			size += _tarWriteHeader(pathbuf + basepathlen + 1, linkpath,
+									&statbuf, sizeonly);
+#else
+
+			/*
+			 * If the platform does not have symbolic links, it should not be
+			 * possible to have tablespaces - clearly somebody else created
+			 * them. Warn about it and ignore.
+			 */
+			ereport(WARNING,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("tablespaces are not supported on this platform")));
+			continue;
+#endif							/* HAVE_READLINK */
+		}
+		else if (S_ISDIR(statbuf.st_mode))
+		{
+			bool		skip_this_dir = false;
+			ListCell   *lc;
+
+			/*
+			 * Store a directory entry in the tar file so we can get the
+			 * permissions right.
+			 */
+			size += _tarWriteHeader(pathbuf + basepathlen + 1, NULL, &statbuf,
+									sizeonly);
+
+			/*
+			 * Call ourselves recursively for a directory, unless it happens
+			 * to be a separate tablespace located within PGDATA.
+			 */
+			foreach(lc, tablespaces)
+			{
+				tablespaceinfo *ti = (tablespaceinfo *) lfirst(lc);
+
+				/*
+				 * ti->rpath is the tablespace relative path within PGDATA, or
+				 * NULL if the tablespace has been properly located somewhere
+				 * else.
+				 *
+				 * Skip past the leading "./" in pathbuf when comparing.
+				 */
+				if (ti->rpath && strcmp(ti->rpath, pathbuf + 2) == 0)
+				{
+					skip_this_dir = true;
+					break;
+				}
+			}
+
+			/*
+			 * skip sending directories inside pg_tblspc, if not required.
+			 */
+			if (strcmp(pathbuf, "./pg_tblspc") == 0 && !sendtblspclinks)
+				skip_this_dir = true;
+
+			if (!skip_this_dir)
+				size += sendDir(pathbuf, basepathlen, sizeonly, tablespaces,
+								sendtblspclinks, manifest, spcoid);
+		}
+		else if (S_ISREG(statbuf.st_mode))
+		{
+			bool		sent = false;
+
+			if (!sizeonly)
+				sent = sendFile(pathbuf, pathbuf + basepathlen + 1, &statbuf,
+								true, isDbDir ? atooid(lastDir + 1) : InvalidOid,
+								manifest, spcoid);
+
+			if (sent || sizeonly)
+			{
+				/* Add size. */
+				size += statbuf.st_size;
+
+				/* Pad to a multiple of the tar block size. */
+				size += tarPaddingBytesRequired(statbuf.st_size);
+
+				/* Size of the header for the file. */
+				size += TAR_BLOCK_SIZE;
+			}
+		}
+		else
+			ereport(WARNING,
+					(errmsg("skipping special file \"%s\"", pathbuf)));
+	}
+	FreeDir(dir);
+	return size;
+}
+
+/*
+ * Check if a file should have its checksum validated.
+ * We validate checksums on files in regular tablespaces
+ * (including global and default) only, and in those there
+ * are some files that are explicitly excluded.
+ */
+static bool
+is_checksummed_file(const char *fullpath, const char *filename)
+{
+	/* Check that the file is in a tablespace */
+	if (strncmp(fullpath, "./global/", 9) == 0 ||
+		strncmp(fullpath, "./base/", 7) == 0 ||
+		strncmp(fullpath, "/", 1) == 0)
+	{
+		int			excludeIdx;
+
+		/* Compare file against noChecksumFiles skip list */
+		for (excludeIdx = 0; noChecksumFiles[excludeIdx].name != NULL; excludeIdx++)
+		{
+			int			cmplen = strlen(noChecksumFiles[excludeIdx].name);
+
+			if (!noChecksumFiles[excludeIdx].match_prefix)
+				cmplen++;
+			if (strncmp(filename, noChecksumFiles[excludeIdx].name,
+						cmplen) == 0)
+				return false;
+		}
+
+		return true;
+	}
+	else
+		return false;
+}
+
+/*****
+ * Functions for handling tar file format
+ *
+ * Copied from pg_dump, but modified to work with libpq for sending
+ */
+
+
+/*
+ * Given the member, write the TAR header & send the file.
+ *
+ * If 'missing_ok' is true, will not throw an error if the file is not found.
+ *
+ * If dboid is anything other than InvalidOid then any checksum failures detected
+ * will get reported to the stats collector.
+ *
+ * Returns true if the file was successfully sent, false if 'missing_ok',
+ * and the file did not exist.
+ */
+static bool
+sendFile(const char *readfilename, const char *tarfilename,
+		 struct stat *statbuf, bool missing_ok, Oid dboid,
+		 backup_manifest_info *manifest, const char *spcoid)
+{
+	int			fd;
+	BlockNumber blkno = 0;
+	bool		block_retry = false;
+	char		buf[TAR_SEND_SIZE];
+	uint16		checksum;
+	int			checksum_failures = 0;
+	off_t		cnt;
+	int			i;
+	pgoff_t		len = 0;
+	char	   *page;
+	size_t		pad;
+	PageHeader	phdr;
+	int			segmentno = 0;
+	char	   *segmentpath;
+	bool		verify_checksum = false;
+	pg_checksum_context checksum_ctx;
+
+	if (pg_checksum_init(&checksum_ctx, manifest->checksum_type) < 0)
+		elog(ERROR, "could not initialize checksum of file \"%s\"",
+			 readfilename);
+
+	fd = OpenTransientFile(readfilename, O_RDONLY | PG_BINARY);
+	if (fd < 0)
+	{
+		if (errno == ENOENT && missing_ok)
+			return false;
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not open file \"%s\": %m", readfilename)));
+	}
+
+	_tarWriteHeader(tarfilename, NULL, statbuf, false);
+
+	if (!noverify_checksums && DataChecksumsEnabled())
+	{
+		char	   *filename;
+
+		/*
+		 * Get the filename (excluding path).  As last_dir_separator()
+		 * includes the last directory separator, we chop that off by
+		 * incrementing the pointer.
+		 */
+		filename = last_dir_separator(readfilename) + 1;
+
+		if (is_checksummed_file(readfilename, filename))
+		{
+			verify_checksum = true;
+
+			/*
+			 * Cut off at the segment boundary (".") to get the segment number
+			 * in order to mix it into the checksum.
+			 */
+			segmentpath = strstr(filename, ".");
+			if (segmentpath != NULL)
+			{
+				segmentno = atoi(segmentpath + 1);
+				if (segmentno == 0)
+					ereport(ERROR,
+							(errmsg("invalid segment number %d in file \"%s\"",
+									segmentno, filename)));
+			}
+		}
+	}
+
+	/*
+	 * Loop until we read the amount of data the caller told us to expect. The
+	 * file could be longer, if it was extended while we were sending it, but
+	 * for a base backup we can ignore such extended data. It will be restored
+	 * from WAL.
+	 */
+	while (len < statbuf->st_size)
+	{
+		/* Try to read some more data. */
+		cnt = basebackup_read_file(fd, buf,
+								   Min(sizeof(buf), statbuf->st_size - len),
+								   len, readfilename, true);
+
+		/*
+		 * If we hit end-of-file, a concurrent truncation must have occurred.
+		 * That's not an error condition, because WAL replay will fix things
+		 * up.
+		 */
+		if (cnt == 0)
+			break;
+
+		/*
+		 * The checksums are verified at block level, so we iterate over the
+		 * buffer in chunks of BLCKSZ, after making sure that
+		 * TAR_SEND_SIZE/buf is divisible by BLCKSZ and we read a multiple of
+		 * BLCKSZ bytes.
+		 */
+		Assert(TAR_SEND_SIZE % BLCKSZ == 0);
+
+		if (verify_checksum && (cnt % BLCKSZ != 0))
+		{
+			ereport(WARNING,
+					(errmsg("could not verify checksum in file \"%s\", block "
+							"%u: read buffer size %d and page size %d "
+							"differ",
+							readfilename, blkno, (int) cnt, BLCKSZ)));
+			verify_checksum = false;
+		}
+
+		if (verify_checksum)
+		{
+			for (i = 0; i < cnt / BLCKSZ; i++)
+			{
+				page = buf + BLCKSZ * i;
+
+				/*
+				 * Only check pages which have not been modified since the
+				 * start of the base backup. Otherwise, they might have been
+				 * written only halfway and the checksum would not be valid.
+				 * However, replaying WAL would reinstate the correct page in
+				 * this case. We also skip completely new pages, since they
+				 * don't have a checksum yet.
+				 */
+				if (!PageIsNew(page) && PageGetLSN(page) < startptr)
+				{
+					checksum = pg_checksum_page((char *) page, blkno + segmentno * RELSEG_SIZE);
+					phdr = (PageHeader) page;
+					if (phdr->pd_checksum != checksum)
+					{
+						/*
+						 * Retry the block on the first failure.  It's
+						 * possible that we read the first 4K page of the
+						 * block just before postgres updated the entire block
+						 * so it ends up looking torn to us.  We only need to
+						 * retry once because the LSN should be updated to
+						 * something we can ignore on the next pass.  If the
+						 * error happens again then it is a true validation
+						 * failure.
+						 */
+						if (block_retry == false)
+						{
+							int			reread_cnt;
+
+							/* Reread the failed block */
+							reread_cnt =
+								basebackup_read_file(fd, buf + BLCKSZ * i,
+													 BLCKSZ, len + BLCKSZ * i,
+													 readfilename,
+													 false);
+							if (reread_cnt == 0)
+							{
+								/*
+								 * If we hit end-of-file, a concurrent
+								 * truncation must have occurred, so break out
+								 * of this loop just as if the initial fread()
+								 * returned 0. We'll drop through to the same
+								 * code that handles that case. (We must fix
+								 * up cnt first, though.)
+								 */
+								cnt = BLCKSZ * i;
+								break;
+							}
+
+							/* Set flag so we know a retry was attempted */
+							block_retry = true;
+
+							/* Reset loop to validate the block again */
+							i--;
+							continue;
+						}
+
+						checksum_failures++;
+
+						if (checksum_failures <= 5)
+							ereport(WARNING,
+									(errmsg("checksum verification failed in "
+											"file \"%s\", block %u: calculated "
+											"%X but expected %X",
+											readfilename, blkno, checksum,
+											phdr->pd_checksum)));
+						if (checksum_failures == 5)
+							ereport(WARNING,
+									(errmsg("further checksum verification "
+											"failures in file \"%s\" will not "
+											"be reported", readfilename)));
+					}
+				}
+				block_retry = false;
+				blkno++;
+			}
+		}
+
+		/* Send the chunk as a CopyData message */
+		if (pq_putmessage('d', buf, cnt))
+			ereport(ERROR,
+					(errmsg("base backup could not send data, aborting backup")));
+		update_basebackup_progress(cnt);
+
+		/* Also feed it to the checksum machinery. */
+		if (pg_checksum_update(&checksum_ctx, (uint8 *) buf, cnt) < 0)
+			elog(ERROR, "could not update checksum of base backup");
+
+		len += cnt;
+		throttle(cnt);
+	}
+
+	/* If the file was truncated while we were sending it, pad it with zeros */
+	if (len < statbuf->st_size)
+	{
+		MemSet(buf, 0, sizeof(buf));
+		while (len < statbuf->st_size)
+		{
+			cnt = Min(sizeof(buf), statbuf->st_size - len);
+			pq_putmessage('d', buf, cnt);
+			if (pg_checksum_update(&checksum_ctx, (uint8 *) buf, cnt) < 0)
+				elog(ERROR, "could not update checksum of base backup");
+			update_basebackup_progress(cnt);
+			len += cnt;
+			throttle(cnt);
+		}
+	}
+
+	/*
+	 * Pad to a block boundary, per tar format requirements. (This small piece
+	 * of data is probably not worth throttling, and is not checksummed
+	 * because it's not actually part of the file.)
+	 */
+	pad = tarPaddingBytesRequired(len);
+	if (pad > 0)
+	{
+		MemSet(buf, 0, pad);
+		pq_putmessage('d', buf, pad);
+		update_basebackup_progress(pad);
+	}
+
+	CloseTransientFile(fd);
+
+	if (checksum_failures > 1)
+	{
+		ereport(WARNING,
+				(errmsg_plural("file \"%s\" has a total of %d checksum verification failure",
+							   "file \"%s\" has a total of %d checksum verification failures",
+							   checksum_failures,
+							   readfilename, checksum_failures)));
+
+		pgstat_report_checksum_failures_in_db(dboid, checksum_failures);
+	}
+
+	total_checksum_failures += checksum_failures;
+
+	AddFileToBackupManifest(manifest, spcoid, tarfilename, statbuf->st_size,
+							(pg_time_t) statbuf->st_mtime, &checksum_ctx);
+
+	return true;
+}
+
+
+static int64
+_tarWriteHeader(const char *filename, const char *linktarget,
+				struct stat *statbuf, bool sizeonly)
+{
+	char		h[TAR_BLOCK_SIZE];
+	enum tarError rc;
+
+	if (!sizeonly)
+	{
+		rc = tarCreateHeader(h, filename, linktarget, statbuf->st_size,
+							 statbuf->st_mode, statbuf->st_uid, statbuf->st_gid,
+							 statbuf->st_mtime);
+
+		switch (rc)
+		{
+			case TAR_OK:
+				break;
+			case TAR_NAME_TOO_LONG:
+				ereport(ERROR,
+						(errmsg("file name too long for tar format: \"%s\"",
+								filename)));
+				break;
+			case TAR_SYMLINK_TOO_LONG:
+				ereport(ERROR,
+						(errmsg("symbolic link target too long for tar format: "
+								"file name \"%s\", target \"%s\"",
+								filename, linktarget)));
+				break;
+			default:
+				elog(ERROR, "unrecognized tar error: %d", rc);
+		}
+
+		pq_putmessage('d', h, sizeof(h));
+		update_basebackup_progress(sizeof(h));
+	}
+
+	return sizeof(h);
+}
+
+/*
+ * Write tar header for a directory.  If the entry in statbuf is a link then
+ * write it as a directory anyway.
+ */
+static int64
+_tarWriteDir(const char *pathbuf, int basepathlen, struct stat *statbuf,
+			 bool sizeonly)
+{
+	/* If symlink, write it as a directory anyway */
+#ifndef WIN32
+	if (S_ISLNK(statbuf->st_mode))
+#else
+	if (pgwin32_is_junction(pathbuf))
+#endif
+		statbuf->st_mode = S_IFDIR | pg_dir_create_mode;
+
+	return _tarWriteHeader(pathbuf + basepathlen + 1, NULL, statbuf, sizeonly);
+}
+
+/*
+ * Increment the network transfer counter by the given number of bytes,
+ * and sleep if necessary to comply with the requested network transfer
+ * rate.
+ */
+static void
+throttle(size_t increment)
+{
+	TimeOffset	elapsed_min;
+
+	if (throttling_counter < 0)
+		return;
+
+	throttling_counter += increment;
+	if (throttling_counter < throttling_sample)
+		return;
+
+	/* How much time should have elapsed at minimum? */
+	elapsed_min = elapsed_min_unit *
+		(throttling_counter / throttling_sample);
+
+	/*
+	 * Since the latch could be set repeatedly because of concurrently WAL
+	 * activity, sleep in a loop to ensure enough time has passed.
+	 */
+	for (;;)
+	{
+		TimeOffset	elapsed,
+					sleep;
+		int			wait_result;
+
+		/* Time elapsed since the last measurement (and possible wake up). */
+		elapsed = GetCurrentTimestamp() - throttled_last;
+
+		/* sleep if the transfer is faster than it should be */
+		sleep = elapsed_min - elapsed;
+		if (sleep <= 0)
+			break;
+
+		ResetLatch(MyLatch);
+
+		/* We're eating a potentially set latch, so check for interrupts */
+		CHECK_FOR_INTERRUPTS();
+
+		/*
+		 * (TAR_SEND_SIZE / throttling_sample * elapsed_min_unit) should be
+		 * the maximum time to sleep. Thus the cast to long is safe.
+		 */
+		wait_result = WaitLatch(MyLatch,
+								WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
+								(long) (sleep / 1000),
+								WAIT_EVENT_BASE_BACKUP_THROTTLE);
+
+		if (wait_result & WL_LATCH_SET)
+			CHECK_FOR_INTERRUPTS();
+
+		/* Done waiting? */
+		if (wait_result & WL_TIMEOUT)
+			break;
+	}
+
+	/*
+	 * As we work with integers, only whole multiple of throttling_sample was
+	 * processed. The rest will be done during the next call of this function.
+	 */
+	throttling_counter %= throttling_sample;
+
+	/*
+	 * Time interval for the remaining amount and possible next increments
+	 * starts now.
+	 */
+	throttled_last = GetCurrentTimestamp();
+}
+
+/*
+ * Increment the counter for the amount of data already streamed
+ * by the given number of bytes, and update the progress report for
+ * pg_stat_progress_basebackup.
+ */
+static void
+update_basebackup_progress(int64 delta)
+{
+	const int	index[] = {
+		PROGRESS_BASEBACKUP_BACKUP_STREAMED,
+		PROGRESS_BASEBACKUP_BACKUP_TOTAL
+	};
+	int64		val[2];
+	int			nparam = 0;
+
+	backup_streamed += delta;
+	val[nparam++] = backup_streamed;
+
+	/*
+	 * Avoid overflowing past 100% or the full size. This may make the total
+	 * size number change as we approach the end of the backup (the estimate
+	 * will always be wrong if WAL is included), but that's better than having
+	 * the done column be bigger than the total.
+	 */
+	if (backup_total > -1 && backup_streamed > backup_total)
+	{
+		backup_total = backup_streamed;
+		val[nparam++] = backup_total;
+	}
+
+	pgstat_progress_update_multi_param(nparam, index, val);
+}
+
+/*
+ * Read some data from a file, setting a wait event and reporting any error
+ * encountered.
+ *
+ * If partial_read_ok is false, also report an error if the number of bytes
+ * read is not equal to the number of bytes requested.
+ *
+ * Returns the number of bytes read.
+ */
+static int
+basebackup_read_file(int fd, char *buf, size_t nbytes, off_t offset,
+					 const char *filename, bool partial_read_ok)
+{
+	int			rc;
+
+	pgstat_report_wait_start(WAIT_EVENT_BASEBACKUP_READ);
+	rc = pg_pread(fd, buf, nbytes, offset);
+	pgstat_report_wait_end();
+
+	if (rc < 0)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not read file \"%s\": %m", filename)));
+	if (!partial_read_ok && rc > 0 && rc != nbytes)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not read file \"%s\": read %d of %zu",
+						filename, rc, nbytes)));
+
+	return rc;
+}
diff --git a/src/backend/replication/libpqwalreceiver/Makefile b/src/backend/replication/libpqwalreceiver/Makefile
new file mode 100644
index 0000000..f26daa1
--- /dev/null
+++ b/src/backend/replication/libpqwalreceiver/Makefile
@@ -0,0 +1,37 @@
+#-------------------------------------------------------------------------
+#
+# Makefile--
+#    Makefile for src/backend/replication/libpqwalreceiver
+#
+# IDENTIFICATION
+#    src/backend/replication/libpqwalreceiver/Makefile
+#
+#-------------------------------------------------------------------------
+
+subdir = src/backend/replication/libpqwalreceiver
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+
+override CPPFLAGS := -I$(srcdir) -I$(libpq_srcdir) $(CPPFLAGS)
+
+OBJS = \
+	$(WIN32RES) \
+	libpqwalreceiver.o
+SHLIB_LINK_INTERNAL = $(libpq)
+SHLIB_LINK = $(filter -lintl, $(LIBS))
+SHLIB_PREREQS = submake-libpq
+PGFILEDESC = "libpqwalreceiver - receive WAL during streaming replication"
+NAME = libpqwalreceiver
+
+all: all-shared-lib
+
+include $(top_srcdir)/src/Makefile.shlib
+
+install: all installdirs install-lib
+
+installdirs: installdirs-lib
+
+uninstall: uninstall-lib
+
+clean distclean maintainer-clean: clean-lib
+	rm -f $(OBJS)
diff --git a/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
new file mode 100644
index 0000000..6eaa84a
--- /dev/null
+++ b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
@@ -0,0 +1,1112 @@
+/*-------------------------------------------------------------------------
+ *
+ * libpqwalreceiver.c
+ *
+ * This file contains the libpq-specific parts of walreceiver. It's
+ * loaded as a dynamic module to avoid linking the main server binary with
+ * libpq.
+ *
+ * Portions Copyright (c) 2010-2021, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <unistd.h>
+#include <sys/time.h>
+
+#include "access/xlog.h"
+#include "catalog/pg_type.h"
+#include "common/connect.h"
+#include "funcapi.h"
+#include "libpq-fe.h"
+#include "mb/pg_wchar.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "pqexpbuffer.h"
+#include "replication/walreceiver.h"
+#include "utils/builtins.h"
+#include "utils/memutils.h"
+#include "utils/pg_lsn.h"
+#include "utils/tuplestore.h"
+
+PG_MODULE_MAGIC;
+
+void		_PG_init(void);
+
+struct WalReceiverConn
+{
+	/* Current connection to the primary, if any */
+	PGconn	   *streamConn;
+	/* Used to remember if the connection is logical or physical */
+	bool		logical;
+	/* Buffer for currently read records */
+	char	   *recvBuf;
+};
+
+/* Prototypes for interface functions */
+static WalReceiverConn *libpqrcv_connect(const char *conninfo,
+										 bool logical, const char *appname,
+										 char **err);
+static void libpqrcv_check_conninfo(const char *conninfo);
+static char *libpqrcv_get_conninfo(WalReceiverConn *conn);
+static void libpqrcv_get_senderinfo(WalReceiverConn *conn,
+									char **sender_host, int *sender_port);
+static char *libpqrcv_identify_system(WalReceiverConn *conn,
+									  TimeLineID *primary_tli);
+static int	libpqrcv_server_version(WalReceiverConn *conn);
+static void libpqrcv_readtimelinehistoryfile(WalReceiverConn *conn,
+											 TimeLineID tli, char **filename,
+											 char **content, int *len);
+static bool libpqrcv_startstreaming(WalReceiverConn *conn,
+									const WalRcvStreamOptions *options);
+static void libpqrcv_endstreaming(WalReceiverConn *conn,
+								  TimeLineID *next_tli);
+static int	libpqrcv_receive(WalReceiverConn *conn, char **buffer,
+							 pgsocket *wait_fd);
+static void libpqrcv_send(WalReceiverConn *conn, const char *buffer,
+						  int nbytes);
+static char *libpqrcv_create_slot(WalReceiverConn *conn,
+								  const char *slotname,
+								  bool temporary,
+								  CRSSnapshotAction snapshot_action,
+								  XLogRecPtr *lsn);
+static pid_t libpqrcv_get_backend_pid(WalReceiverConn *conn);
+static WalRcvExecResult *libpqrcv_exec(WalReceiverConn *conn,
+									   const char *query,
+									   const int nRetTypes,
+									   const Oid *retTypes);
+static void libpqrcv_disconnect(WalReceiverConn *conn);
+
+static WalReceiverFunctionsType PQWalReceiverFunctions = {
+	libpqrcv_connect,
+	libpqrcv_check_conninfo,
+	libpqrcv_get_conninfo,
+	libpqrcv_get_senderinfo,
+	libpqrcv_identify_system,
+	libpqrcv_server_version,
+	libpqrcv_readtimelinehistoryfile,
+	libpqrcv_startstreaming,
+	libpqrcv_endstreaming,
+	libpqrcv_receive,
+	libpqrcv_send,
+	libpqrcv_create_slot,
+	libpqrcv_get_backend_pid,
+	libpqrcv_exec,
+	libpqrcv_disconnect
+};
+
+/* Prototypes for private functions */
+static PGresult *libpqrcv_PQexec(PGconn *streamConn, const char *query);
+static PGresult *libpqrcv_PQgetResult(PGconn *streamConn);
+static char *stringlist_to_identifierstr(PGconn *conn, List *strings);
+
+/*
+ * Module initialization function
+ */
+void
+_PG_init(void)
+{
+	if (WalReceiverFunctions != NULL)
+		elog(ERROR, "libpqwalreceiver already loaded");
+	WalReceiverFunctions = &PQWalReceiverFunctions;
+}
+
+/*
+ * Establish the connection to the primary server for XLOG streaming
+ *
+ * Returns NULL on error and fills the err with palloc'ed error message.
+ */
+static WalReceiverConn *
+libpqrcv_connect(const char *conninfo, bool logical, const char *appname,
+				 char **err)
+{
+	WalReceiverConn *conn;
+	PostgresPollingStatusType status;
+	const char *keys[5];
+	const char *vals[5];
+	int			i = 0;
+
+	/*
+	 * We use the expand_dbname parameter to process the connection string (or
+	 * URI), and pass some extra options.
+	 */
+	keys[i] = "dbname";
+	vals[i] = conninfo;
+	keys[++i] = "replication";
+	vals[i] = logical ? "database" : "true";
+	if (!logical)
+	{
+		/*
+		 * The database name is ignored by the server in replication mode, but
+		 * specify "replication" for .pgpass lookup.
+		 */
+		keys[++i] = "dbname";
+		vals[i] = "replication";
+	}
+	keys[++i] = "fallback_application_name";
+	vals[i] = appname;
+	if (logical)
+	{
+		keys[++i] = "client_encoding";
+		vals[i] = GetDatabaseEncodingName();
+	}
+	keys[++i] = NULL;
+	vals[i] = NULL;
+
+	Assert(i < sizeof(keys));
+
+	conn = palloc0(sizeof(WalReceiverConn));
+	conn->streamConn = PQconnectStartParams(keys, vals,
+											 /* expand_dbname = */ true);
+	if (PQstatus(conn->streamConn) == CONNECTION_BAD)
+	{
+		*err = pchomp(PQerrorMessage(conn->streamConn));
+		return NULL;
+	}
+
+	/*
+	 * Poll connection until we have OK or FAILED status.
+	 *
+	 * Per spec for PQconnectPoll, first wait till socket is write-ready.
+	 */
+	status = PGRES_POLLING_WRITING;
+	do
+	{
+		int			io_flag;
+		int			rc;
+
+		if (status == PGRES_POLLING_READING)
+			io_flag = WL_SOCKET_READABLE;
+#ifdef WIN32
+		/* Windows needs a different test while waiting for connection-made */
+		else if (PQstatus(conn->streamConn) == CONNECTION_STARTED)
+			io_flag = WL_SOCKET_CONNECTED;
+#endif
+		else
+			io_flag = WL_SOCKET_WRITEABLE;
+
+		rc = WaitLatchOrSocket(MyLatch,
+							   WL_EXIT_ON_PM_DEATH | WL_LATCH_SET | io_flag,
+							   PQsocket(conn->streamConn),
+							   0,
+							   WAIT_EVENT_LIBPQWALRECEIVER_CONNECT);
+
+		/* Interrupted? */
+		if (rc & WL_LATCH_SET)
+		{
+			ResetLatch(MyLatch);
+			ProcessWalRcvInterrupts();
+		}
+
+		/* If socket is ready, advance the libpq state machine */
+		if (rc & io_flag)
+			status = PQconnectPoll(conn->streamConn);
+	} while (status != PGRES_POLLING_OK && status != PGRES_POLLING_FAILED);
+
+	if (PQstatus(conn->streamConn) != CONNECTION_OK)
+	{
+		*err = pchomp(PQerrorMessage(conn->streamConn));
+		return NULL;
+	}
+
+	if (logical)
+	{
+		PGresult   *res;
+
+		res = libpqrcv_PQexec(conn->streamConn,
+							  ALWAYS_SECURE_SEARCH_PATH_SQL);
+		if (PQresultStatus(res) != PGRES_TUPLES_OK)
+		{
+			PQclear(res);
+			ereport(ERROR,
+					(errmsg("could not clear search path: %s",
+							pchomp(PQerrorMessage(conn->streamConn)))));
+		}
+		PQclear(res);
+	}
+
+	conn->logical = logical;
+
+	return conn;
+}
+
+/*
+ * Validate connection info string (just try to parse it)
+ */
+static void
+libpqrcv_check_conninfo(const char *conninfo)
+{
+	PQconninfoOption *opts = NULL;
+	char	   *err = NULL;
+
+	opts = PQconninfoParse(conninfo, &err);
+	if (opts == NULL)
+	{
+		/* The error string is malloc'd, so we must free it explicitly */
+		char	   *errcopy = err ? pstrdup(err) : "out of memory";
+
+		PQfreemem(err);
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("invalid connection string syntax: %s", errcopy)));
+	}
+
+	PQconninfoFree(opts);
+}
+
+/*
+ * Return a user-displayable conninfo string.  Any security-sensitive fields
+ * are obfuscated.
+ */
+static char *
+libpqrcv_get_conninfo(WalReceiverConn *conn)
+{
+	PQconninfoOption *conn_opts;
+	PQconninfoOption *conn_opt;
+	PQExpBufferData buf;
+	char	   *retval;
+
+	Assert(conn->streamConn != NULL);
+
+	initPQExpBuffer(&buf);
+	conn_opts = PQconninfo(conn->streamConn);
+
+	if (conn_opts == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_OUT_OF_MEMORY),
+				 errmsg("could not parse connection string: %s",
+						_("out of memory"))));
+
+	/* build a clean connection string from pieces */
+	for (conn_opt = conn_opts; conn_opt->keyword != NULL; conn_opt++)
+	{
+		bool		obfuscate;
+
+		/* Skip debug and empty options */
+		if (strchr(conn_opt->dispchar, 'D') ||
+			conn_opt->val == NULL ||
+			conn_opt->val[0] == '\0')
+			continue;
+
+		/* Obfuscate security-sensitive options */
+		obfuscate = strchr(conn_opt->dispchar, '*') != NULL;
+
+		appendPQExpBuffer(&buf, "%s%s=%s",
+						  buf.len == 0 ? "" : " ",
+						  conn_opt->keyword,
+						  obfuscate ? "********" : conn_opt->val);
+	}
+
+	PQconninfoFree(conn_opts);
+
+	retval = PQExpBufferDataBroken(buf) ? NULL : pstrdup(buf.data);
+	termPQExpBuffer(&buf);
+	return retval;
+}
+
+/*
+ * Provides information of sender this WAL receiver is connected to.
+ */
+static void
+libpqrcv_get_senderinfo(WalReceiverConn *conn, char **sender_host,
+						int *sender_port)
+{
+	char	   *ret = NULL;
+
+	*sender_host = NULL;
+	*sender_port = 0;
+
+	Assert(conn->streamConn != NULL);
+
+	ret = PQhost(conn->streamConn);
+	if (ret && strlen(ret) != 0)
+		*sender_host = pstrdup(ret);
+
+	ret = PQport(conn->streamConn);
+	if (ret && strlen(ret) != 0)
+		*sender_port = atoi(ret);
+}
+
+/*
+ * Check that primary's system identifier matches ours, and fetch the current
+ * timeline ID of the primary.
+ */
+static char *
+libpqrcv_identify_system(WalReceiverConn *conn, TimeLineID *primary_tli)
+{
+	PGresult   *res;
+	char	   *primary_sysid;
+
+	/*
+	 * Get the system identifier and timeline ID as a DataRow message from the
+	 * primary server.
+	 */
+	res = libpqrcv_PQexec(conn->streamConn, "IDENTIFY_SYSTEM");
+	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+	{
+		PQclear(res);
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("could not receive database system identifier and timeline ID from "
+						"the primary server: %s",
+						pchomp(PQerrorMessage(conn->streamConn)))));
+	}
+	if (PQnfields(res) < 3 || PQntuples(res) != 1)
+	{
+		int			ntuples = PQntuples(res);
+		int			nfields = PQnfields(res);
+
+		PQclear(res);
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("invalid response from primary server"),
+				 errdetail("Could not identify system: got %d rows and %d fields, expected %d rows and %d or more fields.",
+						   ntuples, nfields, 3, 1)));
+	}
+	primary_sysid = pstrdup(PQgetvalue(res, 0, 0));
+	*primary_tli = pg_strtoint32(PQgetvalue(res, 0, 1));
+	PQclear(res);
+
+	return primary_sysid;
+}
+
+/*
+ * Thin wrapper around libpq to obtain server version.
+ */
+static int
+libpqrcv_server_version(WalReceiverConn *conn)
+{
+	return PQserverVersion(conn->streamConn);
+}
+
+/*
+ * Start streaming WAL data from given streaming options.
+ *
+ * Returns true if we switched successfully to copy-both mode. False
+ * means the server received the command and executed it successfully, but
+ * didn't switch to copy-mode.  That means that there was no WAL on the
+ * requested timeline and starting point, because the server switched to
+ * another timeline at or before the requested starting point. On failure,
+ * throws an ERROR.
+ */
+static bool
+libpqrcv_startstreaming(WalReceiverConn *conn,
+						const WalRcvStreamOptions *options)
+{
+	StringInfoData cmd;
+	PGresult   *res;
+
+	Assert(options->logical == conn->logical);
+	Assert(options->slotname || !options->logical);
+
+	initStringInfo(&cmd);
+
+	/* Build the command. */
+	appendStringInfoString(&cmd, "START_REPLICATION");
+	if (options->slotname != NULL)
+		appendStringInfo(&cmd, " SLOT \"%s\"",
+						 options->slotname);
+
+	if (options->logical)
+		appendStringInfoString(&cmd, " LOGICAL");
+
+	appendStringInfo(&cmd, " %X/%X", LSN_FORMAT_ARGS(options->startpoint));
+
+	/*
+	 * Additional options are different depending on if we are doing logical
+	 * or physical replication.
+	 */
+	if (options->logical)
+	{
+		char	   *pubnames_str;
+		List	   *pubnames;
+		char	   *pubnames_literal;
+
+		appendStringInfoString(&cmd, " (");
+
+		appendStringInfo(&cmd, "proto_version '%u'",
+						 options->proto.logical.proto_version);
+
+		if (options->proto.logical.streaming &&
+			PQserverVersion(conn->streamConn) >= 140000)
+			appendStringInfoString(&cmd, ", streaming 'on'");
+
+		pubnames = options->proto.logical.publication_names;
+		pubnames_str = stringlist_to_identifierstr(conn->streamConn, pubnames);
+		if (!pubnames_str)
+			ereport(ERROR,
+					(errcode(ERRCODE_OUT_OF_MEMORY),	/* likely guess */
+					 errmsg("could not start WAL streaming: %s",
+							pchomp(PQerrorMessage(conn->streamConn)))));
+		pubnames_literal = PQescapeLiteral(conn->streamConn, pubnames_str,
+										   strlen(pubnames_str));
+		if (!pubnames_literal)
+			ereport(ERROR,
+					(errcode(ERRCODE_OUT_OF_MEMORY),	/* likely guess */
+					 errmsg("could not start WAL streaming: %s",
+							pchomp(PQerrorMessage(conn->streamConn)))));
+		appendStringInfo(&cmd, ", publication_names %s", pubnames_literal);
+		PQfreemem(pubnames_literal);
+		pfree(pubnames_str);
+
+		if (options->proto.logical.binary &&
+			PQserverVersion(conn->streamConn) >= 140000)
+			appendStringInfoString(&cmd, ", binary 'true'");
+
+		appendStringInfoChar(&cmd, ')');
+	}
+	else
+		appendStringInfo(&cmd, " TIMELINE %u",
+						 options->proto.physical.startpointTLI);
+
+	/* Start streaming. */
+	res = libpqrcv_PQexec(conn->streamConn, cmd.data);
+	pfree(cmd.data);
+
+	if (PQresultStatus(res) == PGRES_COMMAND_OK)
+	{
+		PQclear(res);
+		return false;
+	}
+	else if (PQresultStatus(res) != PGRES_COPY_BOTH)
+	{
+		PQclear(res);
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("could not start WAL streaming: %s",
+						pchomp(PQerrorMessage(conn->streamConn)))));
+	}
+	PQclear(res);
+	return true;
+}
+
+/*
+ * Stop streaming WAL data. Returns the next timeline's ID in *next_tli, as
+ * reported by the server, or 0 if it did not report it.
+ */
+static void
+libpqrcv_endstreaming(WalReceiverConn *conn, TimeLineID *next_tli)
+{
+	PGresult   *res;
+
+	/*
+	 * Send copy-end message.  As in libpqrcv_PQexec, this could theoretically
+	 * block, but the risk seems small.
+	 */
+	if (PQputCopyEnd(conn->streamConn, NULL) <= 0 ||
+		PQflush(conn->streamConn))
+		ereport(ERROR,
+				(errcode(ERRCODE_CONNECTION_FAILURE),
+				 errmsg("could not send end-of-streaming message to primary: %s",
+						pchomp(PQerrorMessage(conn->streamConn)))));
+
+	*next_tli = 0;
+
+	/*
+	 * After COPY is finished, we should receive a result set indicating the
+	 * next timeline's ID, or just CommandComplete if the server was shut
+	 * down.
+	 *
+	 * If we had not yet received CopyDone from the backend, PGRES_COPY_OUT is
+	 * also possible in case we aborted the copy in mid-stream.
+	 */
+	res = libpqrcv_PQgetResult(conn->streamConn);
+	if (PQresultStatus(res) == PGRES_TUPLES_OK)
+	{
+		/*
+		 * Read the next timeline's ID. The server also sends the timeline's
+		 * starting point, but it is ignored.
+		 */
+		if (PQnfields(res) < 2 || PQntuples(res) != 1)
+			ereport(ERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("unexpected result set after end-of-streaming")));
+		*next_tli = pg_strtoint32(PQgetvalue(res, 0, 0));
+		PQclear(res);
+
+		/* the result set should be followed by CommandComplete */
+		res = libpqrcv_PQgetResult(conn->streamConn);
+	}
+	else if (PQresultStatus(res) == PGRES_COPY_OUT)
+	{
+		PQclear(res);
+
+		/* End the copy */
+		if (PQendcopy(conn->streamConn))
+			ereport(ERROR,
+					(errcode(ERRCODE_CONNECTION_FAILURE),
+					 errmsg("error while shutting down streaming COPY: %s",
+							pchomp(PQerrorMessage(conn->streamConn)))));
+
+		/* CommandComplete should follow */
+		res = libpqrcv_PQgetResult(conn->streamConn);
+	}
+
+	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("error reading result of streaming command: %s",
+						pchomp(PQerrorMessage(conn->streamConn)))));
+	PQclear(res);
+
+	/* Verify that there are no more results */
+	res = libpqrcv_PQgetResult(conn->streamConn);
+	if (res != NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("unexpected result after CommandComplete: %s",
+						pchomp(PQerrorMessage(conn->streamConn)))));
+}
+
+/*
+ * Fetch the timeline history file for 'tli' from primary.
+ */
+static void
+libpqrcv_readtimelinehistoryfile(WalReceiverConn *conn,
+								 TimeLineID tli, char **filename,
+								 char **content, int *len)
+{
+	PGresult   *res;
+	char		cmd[64];
+
+	Assert(!conn->logical);
+
+	/*
+	 * Request the primary to send over the history file for given timeline.
+	 */
+	snprintf(cmd, sizeof(cmd), "TIMELINE_HISTORY %u", tli);
+	res = libpqrcv_PQexec(conn->streamConn, cmd);
+	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+	{
+		PQclear(res);
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("could not receive timeline history file from "
+						"the primary server: %s",
+						pchomp(PQerrorMessage(conn->streamConn)))));
+	}
+	if (PQnfields(res) != 2 || PQntuples(res) != 1)
+	{
+		int			ntuples = PQntuples(res);
+		int			nfields = PQnfields(res);
+
+		PQclear(res);
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("invalid response from primary server"),
+				 errdetail("Expected 1 tuple with 2 fields, got %d tuples with %d fields.",
+						   ntuples, nfields)));
+	}
+	*filename = pstrdup(PQgetvalue(res, 0, 0));
+
+	*len = PQgetlength(res, 0, 1);
+	*content = palloc(*len);
+	memcpy(*content, PQgetvalue(res, 0, 1), *len);
+	PQclear(res);
+}
+
+/*
+ * Send a query and wait for the results by using the asynchronous libpq
+ * functions and socket readiness events.
+ *
+ * We must not use the regular blocking libpq functions like PQexec()
+ * since they are uninterruptible by signals on some platforms, such as
+ * Windows.
+ *
+ * The function is modeled on PQexec() in libpq, but only implements
+ * those parts that are in use in the walreceiver api.
+ *
+ * May return NULL, rather than an error result, on failure.
+ */
+static PGresult *
+libpqrcv_PQexec(PGconn *streamConn, const char *query)
+{
+	PGresult   *lastResult = NULL;
+
+	/*
+	 * PQexec() silently discards any prior query results on the connection.
+	 * This is not required for this function as it's expected that the caller
+	 * (which is this library in all cases) will behave correctly and we don't
+	 * have to be backwards compatible with old libpq.
+	 */
+
+	/*
+	 * Submit the query.  Since we don't use non-blocking mode, this could
+	 * theoretically block.  In practice, since we don't send very long query
+	 * strings, the risk seems negligible.
+	 */
+	if (!PQsendQuery(streamConn, query))
+		return NULL;
+
+	for (;;)
+	{
+		/* Wait for, and collect, the next PGresult. */
+		PGresult   *result;
+
+		result = libpqrcv_PQgetResult(streamConn);
+		if (result == NULL)
+			break;				/* query is complete, or failure */
+
+		/*
+		 * Emulate PQexec()'s behavior of returning the last result when there
+		 * are many.  We are fine with returning just last error message.
+		 */
+		PQclear(lastResult);
+		lastResult = result;
+
+		if (PQresultStatus(lastResult) == PGRES_COPY_IN ||
+			PQresultStatus(lastResult) == PGRES_COPY_OUT ||
+			PQresultStatus(lastResult) == PGRES_COPY_BOTH ||
+			PQstatus(streamConn) == CONNECTION_BAD)
+			break;
+	}
+
+	return lastResult;
+}
+
+/*
+ * Perform the equivalent of PQgetResult(), but watch for interrupts.
+ */
+static PGresult *
+libpqrcv_PQgetResult(PGconn *streamConn)
+{
+	/*
+	 * Collect data until PQgetResult is ready to get the result without
+	 * blocking.
+	 */
+	while (PQisBusy(streamConn))
+	{
+		int			rc;
+
+		/*
+		 * We don't need to break down the sleep into smaller increments,
+		 * since we'll get interrupted by signals and can handle any
+		 * interrupts here.
+		 */
+		rc = WaitLatchOrSocket(MyLatch,
+							   WL_EXIT_ON_PM_DEATH | WL_SOCKET_READABLE |
+							   WL_LATCH_SET,
+							   PQsocket(streamConn),
+							   0,
+							   WAIT_EVENT_LIBPQWALRECEIVER_RECEIVE);
+
+		/* Interrupted? */
+		if (rc & WL_LATCH_SET)
+		{
+			ResetLatch(MyLatch);
+			ProcessWalRcvInterrupts();
+		}
+
+		/* Consume whatever data is available from the socket */
+		if (PQconsumeInput(streamConn) == 0)
+		{
+			/* trouble; return NULL */
+			return NULL;
+		}
+	}
+
+	/* Now we can collect and return the next PGresult */
+	return PQgetResult(streamConn);
+}
+
+/*
+ * Disconnect connection to primary, if any.
+ */
+static void
+libpqrcv_disconnect(WalReceiverConn *conn)
+{
+	PQfinish(conn->streamConn);
+	if (conn->recvBuf != NULL)
+		PQfreemem(conn->recvBuf);
+	pfree(conn);
+}
+
+/*
+ * Receive a message available from XLOG stream.
+ *
+ * Returns:
+ *
+ *	 If data was received, returns the length of the data. *buffer is set to
+ *	 point to a buffer holding the received message. The buffer is only valid
+ *	 until the next libpqrcv_* call.
+ *
+ *	 If no data was available immediately, returns 0, and *wait_fd is set to a
+ *	 socket descriptor which can be waited on before trying again.
+ *
+ *	 -1 if the server ended the COPY.
+ *
+ * ereports on error.
+ */
+static int
+libpqrcv_receive(WalReceiverConn *conn, char **buffer,
+				 pgsocket *wait_fd)
+{
+	int			rawlen;
+
+	if (conn->recvBuf != NULL)
+		PQfreemem(conn->recvBuf);
+	conn->recvBuf = NULL;
+
+	/* Try to receive a CopyData message */
+	rawlen = PQgetCopyData(conn->streamConn, &conn->recvBuf, 1);
+	if (rawlen == 0)
+	{
+		/* Try consuming some data. */
+		if (PQconsumeInput(conn->streamConn) == 0)
+			ereport(ERROR,
+					(errcode(ERRCODE_CONNECTION_FAILURE),
+					 errmsg("could not receive data from WAL stream: %s",
+							pchomp(PQerrorMessage(conn->streamConn)))));
+
+		/* Now that we've consumed some input, try again */
+		rawlen = PQgetCopyData(conn->streamConn, &conn->recvBuf, 1);
+		if (rawlen == 0)
+		{
+			/* Tell caller to try again when our socket is ready. */
+			*wait_fd = PQsocket(conn->streamConn);
+			return 0;
+		}
+	}
+	if (rawlen == -1)			/* end-of-streaming or error */
+	{
+		PGresult   *res;
+
+		res = libpqrcv_PQgetResult(conn->streamConn);
+		if (PQresultStatus(res) == PGRES_COMMAND_OK)
+		{
+			PQclear(res);
+
+			/* Verify that there are no more results. */
+			res = libpqrcv_PQgetResult(conn->streamConn);
+			if (res != NULL)
+			{
+				PQclear(res);
+
+				/*
+				 * If the other side closed the connection orderly (otherwise
+				 * we'd seen an error, or PGRES_COPY_IN) don't report an error
+				 * here, but let callers deal with it.
+				 */
+				if (PQstatus(conn->streamConn) == CONNECTION_BAD)
+					return -1;
+
+				ereport(ERROR,
+						(errcode(ERRCODE_PROTOCOL_VIOLATION),
+						 errmsg("unexpected result after CommandComplete: %s",
+								PQerrorMessage(conn->streamConn))));
+			}
+
+			return -1;
+		}
+		else if (PQresultStatus(res) == PGRES_COPY_IN)
+		{
+			PQclear(res);
+			return -1;
+		}
+		else
+		{
+			PQclear(res);
+			ereport(ERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("could not receive data from WAL stream: %s",
+							pchomp(PQerrorMessage(conn->streamConn)))));
+		}
+	}
+	if (rawlen < -1)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("could not receive data from WAL stream: %s",
+						pchomp(PQerrorMessage(conn->streamConn)))));
+
+	/* Return received messages to caller */
+	*buffer = conn->recvBuf;
+	return rawlen;
+}
+
+/*
+ * Send a message to XLOG stream.
+ *
+ * ereports on error.
+ */
+static void
+libpqrcv_send(WalReceiverConn *conn, const char *buffer, int nbytes)
+{
+	if (PQputCopyData(conn->streamConn, buffer, nbytes) <= 0 ||
+		PQflush(conn->streamConn))
+		ereport(ERROR,
+				(errcode(ERRCODE_CONNECTION_FAILURE),
+				 errmsg("could not send data to WAL stream: %s",
+						pchomp(PQerrorMessage(conn->streamConn)))));
+}
+
+/*
+ * Create new replication slot.
+ * Returns the name of the exported snapshot for logical slot or NULL for
+ * physical slot.
+ */
+static char *
+libpqrcv_create_slot(WalReceiverConn *conn, const char *slotname,
+					 bool temporary, CRSSnapshotAction snapshot_action,
+					 XLogRecPtr *lsn)
+{
+	PGresult   *res;
+	StringInfoData cmd;
+	char	   *snapshot;
+
+	initStringInfo(&cmd);
+
+	appendStringInfo(&cmd, "CREATE_REPLICATION_SLOT \"%s\"", slotname);
+
+	if (temporary)
+		appendStringInfoString(&cmd, " TEMPORARY");
+
+	if (conn->logical)
+	{
+		appendStringInfoString(&cmd, " LOGICAL pgoutput");
+		switch (snapshot_action)
+		{
+			case CRS_EXPORT_SNAPSHOT:
+				appendStringInfoString(&cmd, " EXPORT_SNAPSHOT");
+				break;
+			case CRS_NOEXPORT_SNAPSHOT:
+				appendStringInfoString(&cmd, " NOEXPORT_SNAPSHOT");
+				break;
+			case CRS_USE_SNAPSHOT:
+				appendStringInfoString(&cmd, " USE_SNAPSHOT");
+				break;
+		}
+	}
+	else
+	{
+		appendStringInfoString(&cmd, " PHYSICAL RESERVE_WAL");
+	}
+
+	res = libpqrcv_PQexec(conn->streamConn, cmd.data);
+	pfree(cmd.data);
+
+	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+	{
+		PQclear(res);
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("could not create replication slot \"%s\": %s",
+						slotname, pchomp(PQerrorMessage(conn->streamConn)))));
+	}
+
+	if (lsn)
+		*lsn = DatumGetLSN(DirectFunctionCall1Coll(pg_lsn_in, InvalidOid,
+												   CStringGetDatum(PQgetvalue(res, 0, 1))));
+
+	if (!PQgetisnull(res, 0, 2))
+		snapshot = pstrdup(PQgetvalue(res, 0, 2));
+	else
+		snapshot = NULL;
+
+	PQclear(res);
+
+	return snapshot;
+}
+
+/*
+ * Return PID of remote backend process.
+ */
+static pid_t
+libpqrcv_get_backend_pid(WalReceiverConn *conn)
+{
+	return PQbackendPID(conn->streamConn);
+}
+
+/*
+ * Convert tuple query result to tuplestore.
+ */
+static void
+libpqrcv_processTuples(PGresult *pgres, WalRcvExecResult *walres,
+					   const int nRetTypes, const Oid *retTypes)
+{
+	int			tupn;
+	int			coln;
+	int			nfields = PQnfields(pgres);
+	HeapTuple	tuple;
+	AttInMetadata *attinmeta;
+	MemoryContext rowcontext;
+	MemoryContext oldcontext;
+
+	/* Make sure we got expected number of fields. */
+	if (nfields != nRetTypes)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("invalid query response"),
+				 errdetail("Expected %d fields, got %d fields.",
+						   nRetTypes, nfields)));
+
+	walres->tuplestore = tuplestore_begin_heap(true, false, work_mem);
+
+	/* Create tuple descriptor corresponding to expected result. */
+	walres->tupledesc = CreateTemplateTupleDesc(nRetTypes);
+	for (coln = 0; coln < nRetTypes; coln++)
+		TupleDescInitEntry(walres->tupledesc, (AttrNumber) coln + 1,
+						   PQfname(pgres, coln), retTypes[coln], -1, 0);
+	attinmeta = TupleDescGetAttInMetadata(walres->tupledesc);
+
+	/* No point in doing more here if there were no tuples returned. */
+	if (PQntuples(pgres) == 0)
+		return;
+
+	/* Create temporary context for local allocations. */
+	rowcontext = AllocSetContextCreate(CurrentMemoryContext,
+									   "libpqrcv query result context",
+									   ALLOCSET_DEFAULT_SIZES);
+
+	/* Process returned rows. */
+	for (tupn = 0; tupn < PQntuples(pgres); tupn++)
+	{
+		char	   *cstrs[MaxTupleAttributeNumber];
+
+		ProcessWalRcvInterrupts();
+
+		/* Do the allocations in temporary context. */
+		oldcontext = MemoryContextSwitchTo(rowcontext);
+
+		/*
+		 * Fill cstrs with null-terminated strings of column values.
+		 */
+		for (coln = 0; coln < nfields; coln++)
+		{
+			if (PQgetisnull(pgres, tupn, coln))
+				cstrs[coln] = NULL;
+			else
+				cstrs[coln] = PQgetvalue(pgres, tupn, coln);
+		}
+
+		/* Convert row to a tuple, and add it to the tuplestore */
+		tuple = BuildTupleFromCStrings(attinmeta, cstrs);
+		tuplestore_puttuple(walres->tuplestore, tuple);
+
+		/* Clean up */
+		MemoryContextSwitchTo(oldcontext);
+		MemoryContextReset(rowcontext);
+	}
+
+	MemoryContextDelete(rowcontext);
+}
+
+/*
+ * Public interface for sending generic queries (and commands).
+ *
+ * This can only be called from process connected to database.
+ */
+static WalRcvExecResult *
+libpqrcv_exec(WalReceiverConn *conn, const char *query,
+			  const int nRetTypes, const Oid *retTypes)
+{
+	PGresult   *pgres = NULL;
+	WalRcvExecResult *walres = palloc0(sizeof(WalRcvExecResult));
+	char	   *diag_sqlstate;
+
+	if (MyDatabaseId == InvalidOid)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("the query interface requires a database connection")));
+
+	pgres = libpqrcv_PQexec(conn->streamConn, query);
+
+	switch (PQresultStatus(pgres))
+	{
+		case PGRES_SINGLE_TUPLE:
+		case PGRES_TUPLES_OK:
+			walres->status = WALRCV_OK_TUPLES;
+			libpqrcv_processTuples(pgres, walres, nRetTypes, retTypes);
+			break;
+
+		case PGRES_COPY_IN:
+			walres->status = WALRCV_OK_COPY_IN;
+			break;
+
+		case PGRES_COPY_OUT:
+			walres->status = WALRCV_OK_COPY_OUT;
+			break;
+
+		case PGRES_COPY_BOTH:
+			walres->status = WALRCV_OK_COPY_BOTH;
+			break;
+
+		case PGRES_COMMAND_OK:
+			walres->status = WALRCV_OK_COMMAND;
+			break;
+
+			/* Empty query is considered error. */
+		case PGRES_EMPTY_QUERY:
+			walres->status = WALRCV_ERROR;
+			walres->err = _("empty query");
+			break;
+
+		case PGRES_PIPELINE_SYNC:
+		case PGRES_PIPELINE_ABORTED:
+			walres->status = WALRCV_ERROR;
+			walres->err = _("unexpected pipeline mode");
+			break;
+
+		case PGRES_NONFATAL_ERROR:
+		case PGRES_FATAL_ERROR:
+		case PGRES_BAD_RESPONSE:
+			walres->status = WALRCV_ERROR;
+			walres->err = pchomp(PQerrorMessage(conn->streamConn));
+			diag_sqlstate = PQresultErrorField(pgres, PG_DIAG_SQLSTATE);
+			if (diag_sqlstate)
+				walres->sqlstate = MAKE_SQLSTATE(diag_sqlstate[0],
+												 diag_sqlstate[1],
+												 diag_sqlstate[2],
+												 diag_sqlstate[3],
+												 diag_sqlstate[4]);
+			break;
+	}
+
+	PQclear(pgres);
+
+	return walres;
+}
+
+/*
+ * Given a List of strings, return it as single comma separated
+ * string, quoting identifiers as needed.
+ *
+ * This is essentially the reverse of SplitIdentifierString.
+ *
+ * The caller should free the result.
+ */
+static char *
+stringlist_to_identifierstr(PGconn *conn, List *strings)
+{
+	ListCell   *lc;
+	StringInfoData res;
+	bool		first = true;
+
+	initStringInfo(&res);
+
+	foreach(lc, strings)
+	{
+		char	   *val = strVal(lfirst(lc));
+		char	   *val_escaped;
+
+		if (first)
+			first = false;
+		else
+			appendStringInfoChar(&res, ',');
+
+		val_escaped = PQescapeIdentifier(conn, val, strlen(val));
+		if (!val_escaped)
+		{
+			free(res.data);
+			return NULL;
+		}
+		appendStringInfoString(&res, val_escaped);
+		PQfreemem(val_escaped);
+	}
+
+	return res.data;
+}
diff --git a/src/backend/replication/logical/Makefile b/src/backend/replication/logical/Makefile
new file mode 100644
index 0000000..c4e2fde
--- /dev/null
+++ b/src/backend/replication/logical/Makefile
@@ -0,0 +1,31 @@
+#-------------------------------------------------------------------------
+#
+# Makefile--
+#    Makefile for src/backend/replication/logical
+#
+# IDENTIFICATION
+#    src/backend/replication/logical/Makefile
+#
+#-------------------------------------------------------------------------
+
+subdir = src/backend/replication/logical
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+
+override CPPFLAGS := -I$(srcdir) $(CPPFLAGS)
+
+OBJS = \
+	decode.o \
+	launcher.o \
+	logical.o \
+	logicalfuncs.o \
+	message.o \
+	origin.o \
+	proto.o \
+	relation.o \
+	reorderbuffer.o \
+	snapbuild.o \
+	tablesync.o \
+	worker.o
+
+include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c
new file mode 100644
index 0000000..92dfafc
--- /dev/null
+++ b/src/backend/replication/logical/decode.c
@@ -0,0 +1,1316 @@
+/* -------------------------------------------------------------------------
+ *
+ * decode.c
+ *		This module decodes WAL records read using xlogreader.h's APIs for the
+ *		purpose of logical decoding by passing information to the
+ *		reorderbuffer module (containing the actual changes) and to the
+ *		snapbuild module to build a fitting catalog snapshot (to be able to
+ *		properly decode the changes in the reorderbuffer).
+ *
+ * NOTE:
+ *		This basically tries to handle all low level xlog stuff for
+ *		reorderbuffer.c and snapbuild.c. There's some minor leakage where a
+ *		specific record's struct is used to pass data along, but those just
+ *		happen to contain the right amount of data in a convenient
+ *		format. There isn't and shouldn't be much intelligence about the
+ *		contents of records in here except turning them into a more usable
+ *		format.
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/decode.c
+ *
+ * -------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/heapam.h"
+#include "access/heapam_xlog.h"
+#include "access/transam.h"
+#include "access/xact.h"
+#include "access/xlog_internal.h"
+#include "access/xlogreader.h"
+#include "access/xlogrecord.h"
+#include "access/xlogutils.h"
+#include "catalog/pg_control.h"
+#include "replication/decode.h"
+#include "replication/logical.h"
+#include "replication/message.h"
+#include "replication/origin.h"
+#include "replication/reorderbuffer.h"
+#include "replication/snapbuild.h"
+#include "storage/standby.h"
+
+typedef struct XLogRecordBuffer
+{
+	XLogRecPtr	origptr;
+	XLogRecPtr	endptr;
+	XLogReaderState *record;
+} XLogRecordBuffer;
+
+/* RMGR Handlers */
+static void DecodeXLogOp(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
+static void DecodeHeapOp(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
+static void DecodeHeap2Op(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
+static void DecodeXactOp(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
+static void DecodeStandbyOp(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
+static void DecodeLogicalMsgOp(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
+
+/* individual record(group)'s handlers */
+static void DecodeInsert(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
+static void DecodeUpdate(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
+static void DecodeDelete(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
+static void DecodeTruncate(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
+static void DecodeMultiInsert(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
+static void DecodeSpecConfirm(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
+
+static void DecodeCommit(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
+						 xl_xact_parsed_commit *parsed, TransactionId xid,
+						 bool two_phase);
+static void DecodeAbort(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
+						xl_xact_parsed_abort *parsed, TransactionId xid,
+						bool two_phase);
+static void DecodePrepare(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
+						  xl_xact_parsed_prepare *parsed);
+
+
+/* common function to decode tuples */
+static void DecodeXLogTuple(char *data, Size len, ReorderBufferTupleBuf *tup);
+
+/* helper functions for decoding transactions */
+static inline bool FilterPrepare(LogicalDecodingContext *ctx,
+								 TransactionId xid, const char *gid);
+static bool DecodeTXNNeedSkip(LogicalDecodingContext *ctx,
+							  XLogRecordBuffer *buf, Oid dbId,
+							  RepOriginId origin_id);
+
+/*
+ * Take every XLogReadRecord()ed record and perform the actions required to
+ * decode it using the output plugin already setup in the logical decoding
+ * context.
+ *
+ * NB: Note that every record's xid needs to be processed by reorderbuffer
+ * (xids contained in the content of records are not relevant for this rule).
+ * That means that for records which'd otherwise not go through the
+ * reorderbuffer ReorderBufferProcessXid() has to be called. We don't want to
+ * call ReorderBufferProcessXid for each record type by default, because
+ * e.g. empty xacts can be handled more efficiently if there's no previous
+ * state for them.
+ *
+ * We also support the ability to fast forward thru records, skipping some
+ * record types completely - see individual record types for details.
+ */
+void
+LogicalDecodingProcessRecord(LogicalDecodingContext *ctx, XLogReaderState *record)
+{
+	XLogRecordBuffer buf;
+	TransactionId txid;
+
+	buf.origptr = ctx->reader->ReadRecPtr;
+	buf.endptr = ctx->reader->EndRecPtr;
+	buf.record = record;
+
+	txid = XLogRecGetTopXid(record);
+
+	/*
+	 * If the top-level xid is valid, we need to assign the subxact to the
+	 * top-level xact. We need to do this for all records, hence we do it
+	 * before the switch.
+	 */
+	if (TransactionIdIsValid(txid))
+	{
+		ReorderBufferAssignChild(ctx->reorder,
+								 txid,
+								 record->decoded_record->xl_xid,
+								 buf.origptr);
+	}
+
+	/* cast so we get a warning when new rmgrs are added */
+	switch ((RmgrId) XLogRecGetRmid(record))
+	{
+			/*
+			 * Rmgrs we care about for logical decoding. Add new rmgrs in
+			 * rmgrlist.h's order.
+			 */
+		case RM_XLOG_ID:
+			DecodeXLogOp(ctx, &buf);
+			break;
+
+		case RM_XACT_ID:
+			DecodeXactOp(ctx, &buf);
+			break;
+
+		case RM_STANDBY_ID:
+			DecodeStandbyOp(ctx, &buf);
+			break;
+
+		case RM_HEAP2_ID:
+			DecodeHeap2Op(ctx, &buf);
+			break;
+
+		case RM_HEAP_ID:
+			DecodeHeapOp(ctx, &buf);
+			break;
+
+		case RM_LOGICALMSG_ID:
+			DecodeLogicalMsgOp(ctx, &buf);
+			break;
+
+			/*
+			 * Rmgrs irrelevant for logical decoding; they describe stuff not
+			 * represented in logical decoding. Add new rmgrs in rmgrlist.h's
+			 * order.
+			 */
+		case RM_SMGR_ID:
+		case RM_CLOG_ID:
+		case RM_DBASE_ID:
+		case RM_TBLSPC_ID:
+		case RM_MULTIXACT_ID:
+		case RM_RELMAP_ID:
+		case RM_BTREE_ID:
+		case RM_HASH_ID:
+		case RM_GIN_ID:
+		case RM_GIST_ID:
+		case RM_SEQ_ID:
+		case RM_SPGIST_ID:
+		case RM_BRIN_ID:
+		case RM_COMMIT_TS_ID:
+		case RM_REPLORIGIN_ID:
+		case RM_GENERIC_ID:
+			/* just deal with xid, and done */
+			ReorderBufferProcessXid(ctx->reorder, XLogRecGetXid(record),
+									buf.origptr);
+			break;
+		case RM_NEXT_ID:
+			elog(ERROR, "unexpected RM_NEXT_ID rmgr_id: %u", (RmgrIds) XLogRecGetRmid(buf.record));
+	}
+}
+
+/*
+ * Handle rmgr XLOG_ID records for DecodeRecordIntoReorderBuffer().
+ */
+static void
+DecodeXLogOp(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
+{
+	SnapBuild  *builder = ctx->snapshot_builder;
+	uint8		info = XLogRecGetInfo(buf->record) & ~XLR_INFO_MASK;
+
+	ReorderBufferProcessXid(ctx->reorder, XLogRecGetXid(buf->record),
+							buf->origptr);
+
+	switch (info)
+	{
+			/* this is also used in END_OF_RECOVERY checkpoints */
+		case XLOG_CHECKPOINT_SHUTDOWN:
+		case XLOG_END_OF_RECOVERY:
+			SnapBuildSerializationPoint(builder, buf->origptr);
+
+			break;
+		case XLOG_CHECKPOINT_ONLINE:
+
+			/*
+			 * a RUNNING_XACTS record will have been logged near to this, we
+			 * can restart from there.
+			 */
+			break;
+		case XLOG_NOOP:
+		case XLOG_NEXTOID:
+		case XLOG_SWITCH:
+		case XLOG_BACKUP_END:
+		case XLOG_PARAMETER_CHANGE:
+		case XLOG_RESTORE_POINT:
+		case XLOG_FPW_CHANGE:
+		case XLOG_FPI_FOR_HINT:
+		case XLOG_FPI:
+		case XLOG_OVERWRITE_CONTRECORD:
+			break;
+		default:
+			elog(ERROR, "unexpected RM_XLOG_ID record type: %u", info);
+	}
+}
+
+/*
+ * Handle rmgr XACT_ID records for DecodeRecordIntoReorderBuffer().
+ */
+static void
+DecodeXactOp(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
+{
+	SnapBuild  *builder = ctx->snapshot_builder;
+	ReorderBuffer *reorder = ctx->reorder;
+	XLogReaderState *r = buf->record;
+	uint8		info = XLogRecGetInfo(r) & XLOG_XACT_OPMASK;
+
+	/*
+	 * If the snapshot isn't yet fully built, we cannot decode anything, so
+	 * bail out.
+	 */
+	if (SnapBuildCurrentState(builder) < SNAPBUILD_FULL_SNAPSHOT)
+		return;
+
+	switch (info)
+	{
+		case XLOG_XACT_COMMIT:
+		case XLOG_XACT_COMMIT_PREPARED:
+			{
+				xl_xact_commit *xlrec;
+				xl_xact_parsed_commit parsed;
+				TransactionId xid;
+				bool		two_phase = false;
+
+				xlrec = (xl_xact_commit *) XLogRecGetData(r);
+				ParseCommitRecord(XLogRecGetInfo(buf->record), xlrec, &parsed);
+
+				if (!TransactionIdIsValid(parsed.twophase_xid))
+					xid = XLogRecGetXid(r);
+				else
+					xid = parsed.twophase_xid;
+
+				/*
+				 * We would like to process the transaction in a two-phase
+				 * manner iff output plugin supports two-phase commits and
+				 * doesn't filter the transaction at prepare time.
+				 */
+				if (info == XLOG_XACT_COMMIT_PREPARED)
+					two_phase = !(FilterPrepare(ctx, xid,
+												parsed.twophase_gid));
+
+				DecodeCommit(ctx, buf, &parsed, xid, two_phase);
+				break;
+			}
+		case XLOG_XACT_ABORT:
+		case XLOG_XACT_ABORT_PREPARED:
+			{
+				xl_xact_abort *xlrec;
+				xl_xact_parsed_abort parsed;
+				TransactionId xid;
+				bool		two_phase = false;
+
+				xlrec = (xl_xact_abort *) XLogRecGetData(r);
+				ParseAbortRecord(XLogRecGetInfo(buf->record), xlrec, &parsed);
+
+				if (!TransactionIdIsValid(parsed.twophase_xid))
+					xid = XLogRecGetXid(r);
+				else
+					xid = parsed.twophase_xid;
+
+				/*
+				 * We would like to process the transaction in a two-phase
+				 * manner iff output plugin supports two-phase commits and
+				 * doesn't filter the transaction at prepare time.
+				 */
+				if (info == XLOG_XACT_ABORT_PREPARED)
+					two_phase = !(FilterPrepare(ctx, xid,
+												parsed.twophase_gid));
+
+				DecodeAbort(ctx, buf, &parsed, xid, two_phase);
+				break;
+			}
+		case XLOG_XACT_ASSIGNMENT:
+
+			/*
+			 * We assign subxact to the toplevel xact while processing each
+			 * record if required.  So, we don't need to do anything here. See
+			 * LogicalDecodingProcessRecord.
+			 */
+			break;
+		case XLOG_XACT_INVALIDATIONS:
+			{
+				TransactionId xid;
+				xl_xact_invals *invals;
+
+				xid = XLogRecGetXid(r);
+				invals = (xl_xact_invals *) XLogRecGetData(r);
+
+				/*
+				 * Execute the invalidations for xid-less transactions,
+				 * otherwise, accumulate them so that they can be processed at
+				 * the commit time.
+				 */
+				if (TransactionIdIsValid(xid))
+				{
+					if (!ctx->fast_forward)
+						ReorderBufferAddInvalidations(reorder, xid,
+													  buf->origptr,
+													  invals->nmsgs,
+													  invals->msgs);
+					ReorderBufferXidSetCatalogChanges(ctx->reorder, xid,
+													  buf->origptr);
+				}
+				else if ((!ctx->fast_forward))
+					ReorderBufferImmediateInvalidation(ctx->reorder,
+													   invals->nmsgs,
+													   invals->msgs);
+			}
+			break;
+		case XLOG_XACT_PREPARE:
+			{
+				xl_xact_parsed_prepare parsed;
+				xl_xact_prepare *xlrec;
+
+				/* ok, parse it */
+				xlrec = (xl_xact_prepare *) XLogRecGetData(r);
+				ParsePrepareRecord(XLogRecGetInfo(buf->record),
+								   xlrec, &parsed);
+
+				/*
+				 * We would like to process the transaction in a two-phase
+				 * manner iff output plugin supports two-phase commits and
+				 * doesn't filter the transaction at prepare time.
+				 */
+				if (FilterPrepare(ctx, parsed.twophase_xid,
+								  parsed.twophase_gid))
+				{
+					ReorderBufferProcessXid(reorder, parsed.twophase_xid,
+											buf->origptr);
+					break;
+				}
+
+				/*
+				 * Note that if the prepared transaction has locked [user]
+				 * catalog tables exclusively then decoding prepare can block
+				 * till the main transaction is committed because it needs to
+				 * lock the catalog tables.
+				 *
+				 * XXX Now, this can even lead to a deadlock if the prepare
+				 * transaction is waiting to get it logically replicated for
+				 * distributed 2PC. Currently, we don't have an in-core
+				 * implementation of prepares for distributed 2PC but some
+				 * out-of-core logical replication solution can have such an
+				 * implementation. They need to inform users to not have locks
+				 * on catalog tables in such transactions.
+				 */
+				DecodePrepare(ctx, buf, &parsed);
+				break;
+			}
+		default:
+			elog(ERROR, "unexpected RM_XACT_ID record type: %u", info);
+	}
+}
+
+/*
+ * Handle rmgr STANDBY_ID records for DecodeRecordIntoReorderBuffer().
+ */
+static void
+DecodeStandbyOp(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
+{
+	SnapBuild  *builder = ctx->snapshot_builder;
+	XLogReaderState *r = buf->record;
+	uint8		info = XLogRecGetInfo(r) & ~XLR_INFO_MASK;
+
+	ReorderBufferProcessXid(ctx->reorder, XLogRecGetXid(r), buf->origptr);
+
+	switch (info)
+	{
+		case XLOG_RUNNING_XACTS:
+			{
+				xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r);
+
+				SnapBuildProcessRunningXacts(builder, buf->origptr, running);
+
+				/*
+				 * Abort all transactions that we keep track of, that are
+				 * older than the record's oldestRunningXid. This is the most
+				 * convenient spot for doing so since, in contrast to shutdown
+				 * or end-of-recovery checkpoints, we have information about
+				 * all running transactions which includes prepared ones,
+				 * while shutdown checkpoints just know that no non-prepared
+				 * transactions are in progress.
+				 */
+				ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid);
+			}
+			break;
+		case XLOG_STANDBY_LOCK:
+			break;
+		case XLOG_INVALIDATIONS:
+
+			/*
+			 * We are processing the invalidations at the command level via
+			 * XLOG_XACT_INVALIDATIONS.  So we don't need to do anything here.
+			 */
+			break;
+		default:
+			elog(ERROR, "unexpected RM_STANDBY_ID record type: %u", info);
+	}
+}
+
+/*
+ * Handle rmgr HEAP2_ID records for DecodeRecordIntoReorderBuffer().
+ */
+static void
+DecodeHeap2Op(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
+{
+	uint8		info = XLogRecGetInfo(buf->record) & XLOG_HEAP_OPMASK;
+	TransactionId xid = XLogRecGetXid(buf->record);
+	SnapBuild  *builder = ctx->snapshot_builder;
+
+	ReorderBufferProcessXid(ctx->reorder, xid, buf->origptr);
+
+	/*
+	 * If we don't have snapshot or we are just fast-forwarding, there is no
+	 * point in decoding changes.
+	 */
+	if (SnapBuildCurrentState(builder) < SNAPBUILD_FULL_SNAPSHOT ||
+		ctx->fast_forward)
+		return;
+
+	switch (info)
+	{
+		case XLOG_HEAP2_MULTI_INSERT:
+			if (!ctx->fast_forward &&
+				SnapBuildProcessChange(builder, xid, buf->origptr))
+				DecodeMultiInsert(ctx, buf);
+			break;
+		case XLOG_HEAP2_NEW_CID:
+			{
+				xl_heap_new_cid *xlrec;
+
+				xlrec = (xl_heap_new_cid *) XLogRecGetData(buf->record);
+				SnapBuildProcessNewCid(builder, xid, buf->origptr, xlrec);
+
+				break;
+			}
+		case XLOG_HEAP2_REWRITE:
+
+			/*
+			 * Although these records only exist to serve the needs of logical
+			 * decoding, all the work happens as part of crash or archive
+			 * recovery, so we don't need to do anything here.
+			 */
+			break;
+
+			/*
+			 * Everything else here is just low level physical stuff we're not
+			 * interested in.
+			 */
+		case XLOG_HEAP2_FREEZE_PAGE:
+		case XLOG_HEAP2_PRUNE:
+		case XLOG_HEAP2_VACUUM:
+		case XLOG_HEAP2_VISIBLE:
+		case XLOG_HEAP2_LOCK_UPDATED:
+			break;
+		default:
+			elog(ERROR, "unexpected RM_HEAP2_ID record type: %u", info);
+	}
+}
+
+/*
+ * Handle rmgr HEAP_ID records for DecodeRecordIntoReorderBuffer().
+ */
+static void
+DecodeHeapOp(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
+{
+	uint8		info = XLogRecGetInfo(buf->record) & XLOG_HEAP_OPMASK;
+	TransactionId xid = XLogRecGetXid(buf->record);
+	SnapBuild  *builder = ctx->snapshot_builder;
+
+	ReorderBufferProcessXid(ctx->reorder, xid, buf->origptr);
+
+	/*
+	 * If we don't have snapshot or we are just fast-forwarding, there is no
+	 * point in decoding data changes.
+	 */
+	if (SnapBuildCurrentState(builder) < SNAPBUILD_FULL_SNAPSHOT ||
+		ctx->fast_forward)
+		return;
+
+	switch (info)
+	{
+		case XLOG_HEAP_INSERT:
+			if (SnapBuildProcessChange(builder, xid, buf->origptr))
+				DecodeInsert(ctx, buf);
+			break;
+
+			/*
+			 * Treat HOT update as normal updates. There is no useful
+			 * information in the fact that we could make it a HOT update
+			 * locally and the WAL layout is compatible.
+			 */
+		case XLOG_HEAP_HOT_UPDATE:
+		case XLOG_HEAP_UPDATE:
+			if (SnapBuildProcessChange(builder, xid, buf->origptr))
+				DecodeUpdate(ctx, buf);
+			break;
+
+		case XLOG_HEAP_DELETE:
+			if (SnapBuildProcessChange(builder, xid, buf->origptr))
+				DecodeDelete(ctx, buf);
+			break;
+
+		case XLOG_HEAP_TRUNCATE:
+			if (SnapBuildProcessChange(builder, xid, buf->origptr))
+				DecodeTruncate(ctx, buf);
+			break;
+
+		case XLOG_HEAP_INPLACE:
+
+			/*
+			 * Inplace updates are only ever performed on catalog tuples and
+			 * can, per definition, not change tuple visibility.  Since we
+			 * don't decode catalog tuples, we're not interested in the
+			 * record's contents.
+			 *
+			 * In-place updates can be used either by XID-bearing transactions
+			 * (e.g.  in CREATE INDEX CONCURRENTLY) or by XID-less
+			 * transactions (e.g.  VACUUM).  In the former case, the commit
+			 * record will include cache invalidations, so we mark the
+			 * transaction as catalog modifying here. Currently that's
+			 * redundant because the commit will do that as well, but once we
+			 * support decoding in-progress relations, this will be important.
+			 */
+			if (!TransactionIdIsValid(xid))
+				break;
+
+			SnapBuildProcessChange(builder, xid, buf->origptr);
+			ReorderBufferXidSetCatalogChanges(ctx->reorder, xid, buf->origptr);
+			break;
+
+		case XLOG_HEAP_CONFIRM:
+			if (SnapBuildProcessChange(builder, xid, buf->origptr))
+				DecodeSpecConfirm(ctx, buf);
+			break;
+
+		case XLOG_HEAP_LOCK:
+			/* we don't care about row level locks for now */
+			break;
+
+		default:
+			elog(ERROR, "unexpected RM_HEAP_ID record type: %u", info);
+			break;
+	}
+}
+
+/*
+ * Ask output plugin whether we want to skip this PREPARE and send
+ * this transaction as a regular commit later.
+ */
+static inline bool
+FilterPrepare(LogicalDecodingContext *ctx, TransactionId xid,
+			  const char *gid)
+{
+	/*
+	 * Skip if decoding of two-phase transactions at PREPARE time is not
+	 * enabled. In that case, all two-phase transactions are considered
+	 * filtered out and will be applied as regular transactions at COMMIT
+	 * PREPARED.
+	 */
+	if (!ctx->twophase)
+		return true;
+
+	/*
+	 * The filter_prepare callback is optional. When not supplied, all
+	 * prepared transactions should go through.
+	 */
+	if (ctx->callbacks.filter_prepare_cb == NULL)
+		return false;
+
+	return filter_prepare_cb_wrapper(ctx, xid, gid);
+}
+
+static inline bool
+FilterByOrigin(LogicalDecodingContext *ctx, RepOriginId origin_id)
+{
+	if (ctx->callbacks.filter_by_origin_cb == NULL)
+		return false;
+
+	return filter_by_origin_cb_wrapper(ctx, origin_id);
+}
+
+/*
+ * Handle rmgr LOGICALMSG_ID records for DecodeRecordIntoReorderBuffer().
+ */
+static void
+DecodeLogicalMsgOp(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
+{
+	SnapBuild  *builder = ctx->snapshot_builder;
+	XLogReaderState *r = buf->record;
+	TransactionId xid = XLogRecGetXid(r);
+	uint8		info = XLogRecGetInfo(r) & ~XLR_INFO_MASK;
+	RepOriginId origin_id = XLogRecGetOrigin(r);
+	Snapshot	snapshot;
+	xl_logical_message *message;
+
+	if (info != XLOG_LOGICAL_MESSAGE)
+		elog(ERROR, "unexpected RM_LOGICALMSG_ID record type: %u", info);
+
+	ReorderBufferProcessXid(ctx->reorder, XLogRecGetXid(r), buf->origptr);
+
+	/*
+	 * If we don't have snapshot or we are just fast-forwarding, there is no
+	 * point in decoding messages.
+	 */
+	if (SnapBuildCurrentState(builder) < SNAPBUILD_FULL_SNAPSHOT ||
+		ctx->fast_forward)
+		return;
+
+	message = (xl_logical_message *) XLogRecGetData(r);
+
+	if (message->dbId != ctx->slot->data.database ||
+		FilterByOrigin(ctx, origin_id))
+		return;
+
+	if (message->transactional &&
+		!SnapBuildProcessChange(builder, xid, buf->origptr))
+		return;
+	else if (!message->transactional &&
+			 (SnapBuildCurrentState(builder) != SNAPBUILD_CONSISTENT ||
+			  SnapBuildXactNeedsSkip(builder, buf->origptr)))
+		return;
+
+	snapshot = SnapBuildGetOrBuildSnapshot(builder, xid);
+	ReorderBufferQueueMessage(ctx->reorder, xid, snapshot, buf->endptr,
+							  message->transactional,
+							  message->message, /* first part of message is
+												 * prefix */
+							  message->message_size,
+							  message->message + message->prefix_size);
+}
+
+/*
+ * Consolidated commit record handling between the different form of commit
+ * records.
+ *
+ * 'two_phase' indicates that caller wants to process the transaction in two
+ * phases, first process prepare if not already done and then process
+ * commit_prepared.
+ */
+static void
+DecodeCommit(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
+			 xl_xact_parsed_commit *parsed, TransactionId xid,
+			 bool two_phase)
+{
+	XLogRecPtr	origin_lsn = InvalidXLogRecPtr;
+	TimestampTz commit_time = parsed->xact_time;
+	RepOriginId origin_id = XLogRecGetOrigin(buf->record);
+	int			i;
+
+	if (parsed->xinfo & XACT_XINFO_HAS_ORIGIN)
+	{
+		origin_lsn = parsed->origin_lsn;
+		commit_time = parsed->origin_timestamp;
+	}
+
+	SnapBuildCommitTxn(ctx->snapshot_builder, buf->origptr, xid,
+					   parsed->nsubxacts, parsed->subxacts);
+
+	/* ----
+	 * Check whether we are interested in this specific transaction, and tell
+	 * the reorderbuffer to forget the content of the (sub-)transactions
+	 * if not.
+	 *
+	 * We can't just use ReorderBufferAbort() here, because we need to execute
+	 * the transaction's invalidations.  This currently won't be needed if
+	 * we're just skipping over the transaction because currently we only do
+	 * so during startup, to get to the first transaction the client needs. As
+	 * we have reset the catalog caches before starting to read WAL, and we
+	 * haven't yet touched any catalogs, there can't be anything to invalidate.
+	 * But if we're "forgetting" this commit because it happened in another
+	 * database, the invalidations might be important, because they could be
+	 * for shared catalogs and we might have loaded data into the relevant
+	 * syscaches.
+	 * ---
+	 */
+	if (DecodeTXNNeedSkip(ctx, buf, parsed->dbId, origin_id))
+	{
+		for (i = 0; i < parsed->nsubxacts; i++)
+		{
+			ReorderBufferForget(ctx->reorder, parsed->subxacts[i], buf->origptr);
+		}
+		ReorderBufferForget(ctx->reorder, xid, buf->origptr);
+
+		return;
+	}
+
+	/* tell the reorderbuffer about the surviving subtransactions */
+	for (i = 0; i < parsed->nsubxacts; i++)
+	{
+		ReorderBufferCommitChild(ctx->reorder, xid, parsed->subxacts[i],
+								 buf->origptr, buf->endptr);
+	}
+
+	/*
+	 * Send the final commit record if the transaction data is already
+	 * decoded, otherwise, process the entire transaction.
+	 */
+	if (two_phase)
+	{
+		ReorderBufferFinishPrepared(ctx->reorder, xid, buf->origptr, buf->endptr,
+									SnapBuildInitialConsistentPoint(ctx->snapshot_builder),
+									commit_time, origin_id, origin_lsn,
+									parsed->twophase_gid, true);
+	}
+	else
+	{
+		ReorderBufferCommit(ctx->reorder, xid, buf->origptr, buf->endptr,
+							commit_time, origin_id, origin_lsn);
+	}
+
+	/*
+	 * Update the decoding stats at transaction prepare/commit/abort.
+	 * Additionally we send the stats when we spill or stream the changes to
+	 * avoid losing them in case the decoding is interrupted. It is not clear
+	 * that sending more or less frequently than this would be better.
+	 */
+	UpdateDecodingStats(ctx);
+}
+
+/*
+ * Decode PREPARE record. Similar logic as in DecodeCommit.
+ *
+ * Note that we don't skip prepare even if have detected concurrent abort
+ * because it is quite possible that we had already sent some changes before we
+ * detect abort in which case we need to abort those changes in the subscriber.
+ * To abort such changes, we do send the prepare and then the rollback prepared
+ * which is what happened on the publisher-side as well. Now, we can invent a
+ * new abort API wherein in such cases we send abort and skip sending prepared
+ * and rollback prepared but then it is not that straightforward because we
+ * might have streamed this transaction by that time in which case it is
+ * handled when the rollback is encountered. It is not impossible to optimize
+ * the concurrent abort case but it can introduce design complexity w.r.t
+ * handling different cases so leaving it for now as it doesn't seem worth it.
+ */
+static void
+DecodePrepare(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
+			  xl_xact_parsed_prepare *parsed)
+{
+	SnapBuild  *builder = ctx->snapshot_builder;
+	XLogRecPtr	origin_lsn = parsed->origin_lsn;
+	TimestampTz prepare_time = parsed->xact_time;
+	XLogRecPtr	origin_id = XLogRecGetOrigin(buf->record);
+	int			i;
+	TransactionId xid = parsed->twophase_xid;
+
+	if (parsed->origin_timestamp != 0)
+		prepare_time = parsed->origin_timestamp;
+
+	/*
+	 * Remember the prepare info for a txn so that it can be used later in
+	 * commit prepared if required. See ReorderBufferFinishPrepared.
+	 */
+	if (!ReorderBufferRememberPrepareInfo(ctx->reorder, xid, buf->origptr,
+										  buf->endptr, prepare_time, origin_id,
+										  origin_lsn))
+		return;
+
+	/* We can't start streaming unless a consistent state is reached. */
+	if (SnapBuildCurrentState(builder) < SNAPBUILD_CONSISTENT)
+	{
+		ReorderBufferSkipPrepare(ctx->reorder, xid);
+		return;
+	}
+
+	/*
+	 * Check whether we need to process this transaction. See
+	 * DecodeTXNNeedSkip for the reasons why we sometimes want to skip the
+	 * transaction.
+	 *
+	 * We can't call ReorderBufferForget as we did in DecodeCommit as the txn
+	 * hasn't yet been committed, removing this txn before a commit might
+	 * result in the computation of an incorrect restart_lsn. See
+	 * SnapBuildProcessRunningXacts. But we need to process cache
+	 * invalidations if there are any for the reasons mentioned in
+	 * DecodeCommit.
+	 */
+	if (DecodeTXNNeedSkip(ctx, buf, parsed->dbId, origin_id))
+	{
+		ReorderBufferSkipPrepare(ctx->reorder, xid);
+		ReorderBufferInvalidate(ctx->reorder, xid, buf->origptr);
+		return;
+	}
+
+	/* Tell the reorderbuffer about the surviving subtransactions. */
+	for (i = 0; i < parsed->nsubxacts; i++)
+	{
+		ReorderBufferCommitChild(ctx->reorder, xid, parsed->subxacts[i],
+								 buf->origptr, buf->endptr);
+	}
+
+	/* replay actions of all transaction + subtransactions in order */
+	ReorderBufferPrepare(ctx->reorder, xid, parsed->twophase_gid);
+
+	/*
+	 * Update the decoding stats at transaction prepare/commit/abort.
+	 * Additionally we send the stats when we spill or stream the changes to
+	 * avoid losing them in case the decoding is interrupted. It is not clear
+	 * that sending more or less frequently than this would be better.
+	 */
+	UpdateDecodingStats(ctx);
+}
+
+
+/*
+ * Get the data from the various forms of abort records and pass it on to
+ * snapbuild.c and reorderbuffer.c.
+ *
+ * 'two_phase' indicates to finish prepared transaction.
+ */
+static void
+DecodeAbort(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
+			xl_xact_parsed_abort *parsed, TransactionId xid,
+			bool two_phase)
+{
+	int			i;
+	XLogRecPtr	origin_lsn = InvalidXLogRecPtr;
+	TimestampTz abort_time = parsed->xact_time;
+	XLogRecPtr	origin_id = XLogRecGetOrigin(buf->record);
+	bool		skip_xact;
+
+	if (parsed->xinfo & XACT_XINFO_HAS_ORIGIN)
+	{
+		origin_lsn = parsed->origin_lsn;
+		abort_time = parsed->origin_timestamp;
+	}
+
+	/*
+	 * Check whether we need to process this transaction. See
+	 * DecodeTXNNeedSkip for the reasons why we sometimes want to skip the
+	 * transaction.
+	 */
+	skip_xact = DecodeTXNNeedSkip(ctx, buf, parsed->dbId, origin_id);
+
+	/*
+	 * Send the final rollback record for a prepared transaction unless we
+	 * need to skip it. For non-two-phase xacts, simply forget the xact.
+	 */
+	if (two_phase && !skip_xact)
+	{
+		ReorderBufferFinishPrepared(ctx->reorder, xid, buf->origptr, buf->endptr,
+									InvalidXLogRecPtr,
+									abort_time, origin_id, origin_lsn,
+									parsed->twophase_gid, false);
+	}
+	else
+	{
+		for (i = 0; i < parsed->nsubxacts; i++)
+		{
+			ReorderBufferAbort(ctx->reorder, parsed->subxacts[i],
+							   buf->record->EndRecPtr);
+		}
+
+		ReorderBufferAbort(ctx->reorder, xid, buf->record->EndRecPtr);
+	}
+
+	/* update the decoding stats */
+	UpdateDecodingStats(ctx);
+}
+
+/*
+ * Parse XLOG_HEAP_INSERT (not MULTI_INSERT!) records into tuplebufs.
+ *
+ * Deletes can contain the new tuple.
+ */
+static void
+DecodeInsert(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
+{
+	Size		datalen;
+	char	   *tupledata;
+	Size		tuplelen;
+	XLogReaderState *r = buf->record;
+	xl_heap_insert *xlrec;
+	ReorderBufferChange *change;
+	RelFileNode target_node;
+
+	xlrec = (xl_heap_insert *) XLogRecGetData(r);
+
+	/*
+	 * Ignore insert records without new tuples (this does happen when
+	 * raw_heap_insert marks the TOAST record as HEAP_INSERT_NO_LOGICAL).
+	 */
+	if (!(xlrec->flags & XLH_INSERT_CONTAINS_NEW_TUPLE))
+		return;
+
+	/* only interested in our database */
+	XLogRecGetBlockTag(r, 0, &target_node, NULL, NULL);
+	if (target_node.dbNode != ctx->slot->data.database)
+		return;
+
+	/* output plugin doesn't look for this origin, no need to queue */
+	if (FilterByOrigin(ctx, XLogRecGetOrigin(r)))
+		return;
+
+	change = ReorderBufferGetChange(ctx->reorder);
+	if (!(xlrec->flags & XLH_INSERT_IS_SPECULATIVE))
+		change->action = REORDER_BUFFER_CHANGE_INSERT;
+	else
+		change->action = REORDER_BUFFER_CHANGE_INTERNAL_SPEC_INSERT;
+	change->origin_id = XLogRecGetOrigin(r);
+
+	memcpy(&change->data.tp.relnode, &target_node, sizeof(RelFileNode));
+
+	tupledata = XLogRecGetBlockData(r, 0, &datalen);
+	tuplelen = datalen - SizeOfHeapHeader;
+
+	change->data.tp.newtuple =
+		ReorderBufferGetTupleBuf(ctx->reorder, tuplelen);
+
+	DecodeXLogTuple(tupledata, datalen, change->data.tp.newtuple);
+
+	change->data.tp.clear_toast_afterwards = true;
+
+	ReorderBufferQueueChange(ctx->reorder, XLogRecGetXid(r), buf->origptr,
+							 change,
+							 xlrec->flags & XLH_INSERT_ON_TOAST_RELATION);
+}
+
+/*
+ * Parse XLOG_HEAP_UPDATE and XLOG_HEAP_HOT_UPDATE, which have the same layout
+ * in the record, from wal into proper tuplebufs.
+ *
+ * Updates can possibly contain a new tuple and the old primary key.
+ */
+static void
+DecodeUpdate(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
+{
+	XLogReaderState *r = buf->record;
+	xl_heap_update *xlrec;
+	ReorderBufferChange *change;
+	char	   *data;
+	RelFileNode target_node;
+
+	xlrec = (xl_heap_update *) XLogRecGetData(r);
+
+	/* only interested in our database */
+	XLogRecGetBlockTag(r, 0, &target_node, NULL, NULL);
+	if (target_node.dbNode != ctx->slot->data.database)
+		return;
+
+	/* output plugin doesn't look for this origin, no need to queue */
+	if (FilterByOrigin(ctx, XLogRecGetOrigin(r)))
+		return;
+
+	change = ReorderBufferGetChange(ctx->reorder);
+	change->action = REORDER_BUFFER_CHANGE_UPDATE;
+	change->origin_id = XLogRecGetOrigin(r);
+	memcpy(&change->data.tp.relnode, &target_node, sizeof(RelFileNode));
+
+	if (xlrec->flags & XLH_UPDATE_CONTAINS_NEW_TUPLE)
+	{
+		Size		datalen;
+		Size		tuplelen;
+
+		data = XLogRecGetBlockData(r, 0, &datalen);
+
+		tuplelen = datalen - SizeOfHeapHeader;
+
+		change->data.tp.newtuple =
+			ReorderBufferGetTupleBuf(ctx->reorder, tuplelen);
+
+		DecodeXLogTuple(data, datalen, change->data.tp.newtuple);
+	}
+
+	if (xlrec->flags & XLH_UPDATE_CONTAINS_OLD)
+	{
+		Size		datalen;
+		Size		tuplelen;
+
+		/* caution, remaining data in record is not aligned */
+		data = XLogRecGetData(r) + SizeOfHeapUpdate;
+		datalen = XLogRecGetDataLen(r) - SizeOfHeapUpdate;
+		tuplelen = datalen - SizeOfHeapHeader;
+
+		change->data.tp.oldtuple =
+			ReorderBufferGetTupleBuf(ctx->reorder, tuplelen);
+
+		DecodeXLogTuple(data, datalen, change->data.tp.oldtuple);
+	}
+
+	change->data.tp.clear_toast_afterwards = true;
+
+	ReorderBufferQueueChange(ctx->reorder, XLogRecGetXid(r), buf->origptr,
+							 change, false);
+}
+
+/*
+ * Parse XLOG_HEAP_DELETE from wal into proper tuplebufs.
+ *
+ * Deletes can possibly contain the old primary key.
+ */
+static void
+DecodeDelete(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
+{
+	XLogReaderState *r = buf->record;
+	xl_heap_delete *xlrec;
+	ReorderBufferChange *change;
+	RelFileNode target_node;
+
+	xlrec = (xl_heap_delete *) XLogRecGetData(r);
+
+	/* only interested in our database */
+	XLogRecGetBlockTag(r, 0, &target_node, NULL, NULL);
+	if (target_node.dbNode != ctx->slot->data.database)
+		return;
+
+	/* output plugin doesn't look for this origin, no need to queue */
+	if (FilterByOrigin(ctx, XLogRecGetOrigin(r)))
+		return;
+
+	change = ReorderBufferGetChange(ctx->reorder);
+
+	if (xlrec->flags & XLH_DELETE_IS_SUPER)
+		change->action = REORDER_BUFFER_CHANGE_INTERNAL_SPEC_ABORT;
+	else
+		change->action = REORDER_BUFFER_CHANGE_DELETE;
+
+	change->origin_id = XLogRecGetOrigin(r);
+
+	memcpy(&change->data.tp.relnode, &target_node, sizeof(RelFileNode));
+
+	/* old primary key stored */
+	if (xlrec->flags & XLH_DELETE_CONTAINS_OLD)
+	{
+		Size		datalen = XLogRecGetDataLen(r) - SizeOfHeapDelete;
+		Size		tuplelen = datalen - SizeOfHeapHeader;
+
+		Assert(XLogRecGetDataLen(r) > (SizeOfHeapDelete + SizeOfHeapHeader));
+
+		change->data.tp.oldtuple =
+			ReorderBufferGetTupleBuf(ctx->reorder, tuplelen);
+
+		DecodeXLogTuple((char *) xlrec + SizeOfHeapDelete,
+						datalen, change->data.tp.oldtuple);
+	}
+
+	change->data.tp.clear_toast_afterwards = true;
+
+	ReorderBufferQueueChange(ctx->reorder, XLogRecGetXid(r), buf->origptr,
+							 change, false);
+}
+
+/*
+ * Parse XLOG_HEAP_TRUNCATE from wal
+ */
+static void
+DecodeTruncate(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
+{
+	XLogReaderState *r = buf->record;
+	xl_heap_truncate *xlrec;
+	ReorderBufferChange *change;
+
+	xlrec = (xl_heap_truncate *) XLogRecGetData(r);
+
+	/* only interested in our database */
+	if (xlrec->dbId != ctx->slot->data.database)
+		return;
+
+	/* output plugin doesn't look for this origin, no need to queue */
+	if (FilterByOrigin(ctx, XLogRecGetOrigin(r)))
+		return;
+
+	change = ReorderBufferGetChange(ctx->reorder);
+	change->action = REORDER_BUFFER_CHANGE_TRUNCATE;
+	change->origin_id = XLogRecGetOrigin(r);
+	if (xlrec->flags & XLH_TRUNCATE_CASCADE)
+		change->data.truncate.cascade = true;
+	if (xlrec->flags & XLH_TRUNCATE_RESTART_SEQS)
+		change->data.truncate.restart_seqs = true;
+	change->data.truncate.nrelids = xlrec->nrelids;
+	change->data.truncate.relids = ReorderBufferGetRelids(ctx->reorder,
+														  xlrec->nrelids);
+	memcpy(change->data.truncate.relids, xlrec->relids,
+		   xlrec->nrelids * sizeof(Oid));
+	ReorderBufferQueueChange(ctx->reorder, XLogRecGetXid(r),
+							 buf->origptr, change, false);
+}
+
+/*
+ * Decode XLOG_HEAP2_MULTI_INSERT_insert record into multiple tuplebufs.
+ *
+ * Currently MULTI_INSERT will always contain the full tuples.
+ */
+static void
+DecodeMultiInsert(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
+{
+	XLogReaderState *r = buf->record;
+	xl_heap_multi_insert *xlrec;
+	int			i;
+	char	   *data;
+	char	   *tupledata;
+	Size		tuplelen;
+	RelFileNode rnode;
+
+	xlrec = (xl_heap_multi_insert *) XLogRecGetData(r);
+
+	/*
+	 * Ignore insert records without new tuples.  This happens when a
+	 * multi_insert is done on a catalog or on a non-persistent relation.
+	 */
+	if (!(xlrec->flags & XLH_INSERT_CONTAINS_NEW_TUPLE))
+		return;
+
+	/* only interested in our database */
+	XLogRecGetBlockTag(r, 0, &rnode, NULL, NULL);
+	if (rnode.dbNode != ctx->slot->data.database)
+		return;
+
+	/* output plugin doesn't look for this origin, no need to queue */
+	if (FilterByOrigin(ctx, XLogRecGetOrigin(r)))
+		return;
+
+	/*
+	 * We know that this multi_insert isn't for a catalog, so the block should
+	 * always have data even if a full-page write of it is taken.
+	 */
+	tupledata = XLogRecGetBlockData(r, 0, &tuplelen);
+	Assert(tupledata != NULL);
+
+	data = tupledata;
+	for (i = 0; i < xlrec->ntuples; i++)
+	{
+		ReorderBufferChange *change;
+		xl_multi_insert_tuple *xlhdr;
+		int			datalen;
+		ReorderBufferTupleBuf *tuple;
+		HeapTupleHeader header;
+
+		change = ReorderBufferGetChange(ctx->reorder);
+		change->action = REORDER_BUFFER_CHANGE_INSERT;
+		change->origin_id = XLogRecGetOrigin(r);
+
+		memcpy(&change->data.tp.relnode, &rnode, sizeof(RelFileNode));
+
+		xlhdr = (xl_multi_insert_tuple *) SHORTALIGN(data);
+		data = ((char *) xlhdr) + SizeOfMultiInsertTuple;
+		datalen = xlhdr->datalen;
+
+		change->data.tp.newtuple =
+			ReorderBufferGetTupleBuf(ctx->reorder, datalen);
+
+		tuple = change->data.tp.newtuple;
+		header = tuple->tuple.t_data;
+
+		/* not a disk based tuple */
+		ItemPointerSetInvalid(&tuple->tuple.t_self);
+
+		/*
+		 * We can only figure this out after reassembling the transactions.
+		 */
+		tuple->tuple.t_tableOid = InvalidOid;
+
+		tuple->tuple.t_len = datalen + SizeofHeapTupleHeader;
+
+		memset(header, 0, SizeofHeapTupleHeader);
+
+		memcpy((char *) tuple->tuple.t_data + SizeofHeapTupleHeader,
+			   (char *) data,
+			   datalen);
+		header->t_infomask = xlhdr->t_infomask;
+		header->t_infomask2 = xlhdr->t_infomask2;
+		header->t_hoff = xlhdr->t_hoff;
+
+		/*
+		 * Reset toast reassembly state only after the last row in the last
+		 * xl_multi_insert_tuple record emitted by one heap_multi_insert()
+		 * call.
+		 */
+		if (xlrec->flags & XLH_INSERT_LAST_IN_MULTI &&
+			(i + 1) == xlrec->ntuples)
+			change->data.tp.clear_toast_afterwards = true;
+		else
+			change->data.tp.clear_toast_afterwards = false;
+
+		ReorderBufferQueueChange(ctx->reorder, XLogRecGetXid(r),
+								 buf->origptr, change, false);
+
+		/* move to the next xl_multi_insert_tuple entry */
+		data += datalen;
+	}
+	Assert(data == tupledata + tuplelen);
+}
+
+/*
+ * Parse XLOG_HEAP_CONFIRM from wal into a confirmation change.
+ *
+ * This is pretty trivial, all the state essentially already setup by the
+ * speculative insertion.
+ */
+static void
+DecodeSpecConfirm(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
+{
+	XLogReaderState *r = buf->record;
+	ReorderBufferChange *change;
+	RelFileNode target_node;
+
+	/* only interested in our database */
+	XLogRecGetBlockTag(r, 0, &target_node, NULL, NULL);
+	if (target_node.dbNode != ctx->slot->data.database)
+		return;
+
+	/* output plugin doesn't look for this origin, no need to queue */
+	if (FilterByOrigin(ctx, XLogRecGetOrigin(r)))
+		return;
+
+	change = ReorderBufferGetChange(ctx->reorder);
+	change->action = REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM;
+	change->origin_id = XLogRecGetOrigin(r);
+
+	memcpy(&change->data.tp.relnode, &target_node, sizeof(RelFileNode));
+
+	change->data.tp.clear_toast_afterwards = true;
+
+	ReorderBufferQueueChange(ctx->reorder, XLogRecGetXid(r), buf->origptr,
+							 change, false);
+}
+
+
+/*
+ * Read a HeapTuple as WAL logged by heap_insert, heap_update and heap_delete
+ * (but not by heap_multi_insert) into a tuplebuf.
+ *
+ * The size 'len' and the pointer 'data' in the record need to be
+ * computed outside as they are record specific.
+ */
+static void
+DecodeXLogTuple(char *data, Size len, ReorderBufferTupleBuf *tuple)
+{
+	xl_heap_header xlhdr;
+	int			datalen = len - SizeOfHeapHeader;
+	HeapTupleHeader header;
+
+	Assert(datalen >= 0);
+
+	tuple->tuple.t_len = datalen + SizeofHeapTupleHeader;
+	header = tuple->tuple.t_data;
+
+	/* not a disk based tuple */
+	ItemPointerSetInvalid(&tuple->tuple.t_self);
+
+	/* we can only figure this out after reassembling the transactions */
+	tuple->tuple.t_tableOid = InvalidOid;
+
+	/* data is not stored aligned, copy to aligned storage */
+	memcpy((char *) &xlhdr,
+		   data,
+		   SizeOfHeapHeader);
+
+	memset(header, 0, SizeofHeapTupleHeader);
+
+	memcpy(((char *) tuple->tuple.t_data) + SizeofHeapTupleHeader,
+		   data + SizeOfHeapHeader,
+		   datalen);
+
+	header->t_infomask = xlhdr.t_infomask;
+	header->t_infomask2 = xlhdr.t_infomask2;
+	header->t_hoff = xlhdr.t_hoff;
+}
+
+/*
+ * Check whether we are interested in this specific transaction.
+ *
+ * There can be several reasons we might not be interested in this
+ * transaction:
+ * 1) We might not be interested in decoding transactions up to this
+ *	  LSN. This can happen because we previously decoded it and now just
+ *	  are restarting or if we haven't assembled a consistent snapshot yet.
+ * 2) The transaction happened in another database.
+ * 3) The output plugin is not interested in the origin.
+ * 4) We are doing fast-forwarding
+ */
+static bool
+DecodeTXNNeedSkip(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
+				  Oid txn_dbid, RepOriginId origin_id)
+{
+	return (SnapBuildXactNeedsSkip(ctx->snapshot_builder, buf->origptr) ||
+			(txn_dbid != InvalidOid && txn_dbid != ctx->slot->data.database) ||
+			ctx->fast_forward || FilterByOrigin(ctx, origin_id));
+}
diff --git a/src/backend/replication/logical/launcher.c b/src/backend/replication/logical/launcher.c
new file mode 100644
index 0000000..3c69817
--- /dev/null
+++ b/src/backend/replication/logical/launcher.c
@@ -0,0 +1,1024 @@
+/*-------------------------------------------------------------------------
+ * launcher.c
+ *	   PostgreSQL logical replication worker launcher process
+ *
+ * Copyright (c) 2016-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/launcher.c
+ *
+ * NOTES
+ *	  This module contains the logical replication worker launcher which
+ *	  uses the background worker infrastructure to start the logical
+ *	  replication workers for every enabled subscription.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/heapam.h"
+#include "access/htup.h"
+#include "access/htup_details.h"
+#include "access/tableam.h"
+#include "access/xact.h"
+#include "catalog/pg_subscription.h"
+#include "catalog/pg_subscription_rel.h"
+#include "funcapi.h"
+#include "libpq/pqsignal.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "postmaster/bgworker.h"
+#include "postmaster/fork_process.h"
+#include "postmaster/interrupt.h"
+#include "postmaster/postmaster.h"
+#include "replication/logicallauncher.h"
+#include "replication/logicalworker.h"
+#include "replication/slot.h"
+#include "replication/walreceiver.h"
+#include "replication/worker_internal.h"
+#include "storage/ipc.h"
+#include "storage/proc.h"
+#include "storage/procarray.h"
+#include "storage/procsignal.h"
+#include "tcop/tcopprot.h"
+#include "utils/memutils.h"
+#include "utils/pg_lsn.h"
+#include "utils/ps_status.h"
+#include "utils/snapmgr.h"
+#include "utils/timeout.h"
+
+/* max sleep time between cycles (3min) */
+#define DEFAULT_NAPTIME_PER_CYCLE 180000L
+
+int			max_logical_replication_workers = 4;
+int			max_sync_workers_per_subscription = 2;
+
+LogicalRepWorker *MyLogicalRepWorker = NULL;
+
+typedef struct LogicalRepCtxStruct
+{
+	/* Supervisor process. */
+	pid_t		launcher_pid;
+
+	/* Background workers. */
+	LogicalRepWorker workers[FLEXIBLE_ARRAY_MEMBER];
+} LogicalRepCtxStruct;
+
+LogicalRepCtxStruct *LogicalRepCtx;
+
+static void ApplyLauncherWakeup(void);
+static void logicalrep_launcher_onexit(int code, Datum arg);
+static void logicalrep_worker_onexit(int code, Datum arg);
+static void logicalrep_worker_detach(void);
+static void logicalrep_worker_cleanup(LogicalRepWorker *worker);
+
+static bool on_commit_launcher_wakeup = false;
+
+Datum		pg_stat_get_subscription(PG_FUNCTION_ARGS);
+
+
+/*
+ * Load the list of subscriptions.
+ *
+ * Only the fields interesting for worker start/stop functions are filled for
+ * each subscription.
+ */
+static List *
+get_subscription_list(void)
+{
+	List	   *res = NIL;
+	Relation	rel;
+	TableScanDesc scan;
+	HeapTuple	tup;
+	MemoryContext resultcxt;
+
+	/* This is the context that we will allocate our output data in */
+	resultcxt = CurrentMemoryContext;
+
+	/*
+	 * Start a transaction so we can access pg_database, and get a snapshot.
+	 * We don't have a use for the snapshot itself, but we're interested in
+	 * the secondary effect that it sets RecentGlobalXmin.  (This is critical
+	 * for anything that reads heap pages, because HOT may decide to prune
+	 * them even if the process doesn't attempt to modify any tuples.)
+	 *
+	 * FIXME: This comment is inaccurate / the code buggy. A snapshot that is
+	 * not pushed/active does not reliably prevent HOT pruning (->xmin could
+	 * e.g. be cleared when cache invalidations are processed).
+	 */
+	StartTransactionCommand();
+	(void) GetTransactionSnapshot();
+
+	rel = table_open(SubscriptionRelationId, AccessShareLock);
+	scan = table_beginscan_catalog(rel, 0, NULL);
+
+	while (HeapTupleIsValid(tup = heap_getnext(scan, ForwardScanDirection)))
+	{
+		Form_pg_subscription subform = (Form_pg_subscription) GETSTRUCT(tup);
+		Subscription *sub;
+		MemoryContext oldcxt;
+
+		/*
+		 * Allocate our results in the caller's context, not the
+		 * transaction's. We do this inside the loop, and restore the original
+		 * context at the end, so that leaky things like heap_getnext() are
+		 * not called in a potentially long-lived context.
+		 */
+		oldcxt = MemoryContextSwitchTo(resultcxt);
+
+		sub = (Subscription *) palloc0(sizeof(Subscription));
+		sub->oid = subform->oid;
+		sub->dbid = subform->subdbid;
+		sub->owner = subform->subowner;
+		sub->enabled = subform->subenabled;
+		sub->name = pstrdup(NameStr(subform->subname));
+		/* We don't fill fields we are not interested in. */
+
+		res = lappend(res, sub);
+		MemoryContextSwitchTo(oldcxt);
+	}
+
+	table_endscan(scan);
+	table_close(rel, AccessShareLock);
+
+	CommitTransactionCommand();
+
+	return res;
+}
+
+/*
+ * Wait for a background worker to start up and attach to the shmem context.
+ *
+ * This is only needed for cleaning up the shared memory in case the worker
+ * fails to attach.
+ */
+static void
+WaitForReplicationWorkerAttach(LogicalRepWorker *worker,
+							   uint16 generation,
+							   BackgroundWorkerHandle *handle)
+{
+	BgwHandleStatus status;
+	int			rc;
+
+	for (;;)
+	{
+		pid_t		pid;
+
+		CHECK_FOR_INTERRUPTS();
+
+		LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
+
+		/* Worker either died or has started; no need to do anything. */
+		if (!worker->in_use || worker->proc)
+		{
+			LWLockRelease(LogicalRepWorkerLock);
+			return;
+		}
+
+		LWLockRelease(LogicalRepWorkerLock);
+
+		/* Check if worker has died before attaching, and clean up after it. */
+		status = GetBackgroundWorkerPid(handle, &pid);
+
+		if (status == BGWH_STOPPED)
+		{
+			LWLockAcquire(LogicalRepWorkerLock, LW_EXCLUSIVE);
+			/* Ensure that this was indeed the worker we waited for. */
+			if (generation == worker->generation)
+				logicalrep_worker_cleanup(worker);
+			LWLockRelease(LogicalRepWorkerLock);
+			return;
+		}
+
+		/*
+		 * We need timeout because we generally don't get notified via latch
+		 * about the worker attach.  But we don't expect to have to wait long.
+		 */
+		rc = WaitLatch(MyLatch,
+					   WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
+					   10L, WAIT_EVENT_BGWORKER_STARTUP);
+
+		if (rc & WL_LATCH_SET)
+		{
+			ResetLatch(MyLatch);
+			CHECK_FOR_INTERRUPTS();
+		}
+	}
+}
+
+/*
+ * Walks the workers array and searches for one that matches given
+ * subscription id and relid.
+ */
+LogicalRepWorker *
+logicalrep_worker_find(Oid subid, Oid relid, bool only_running)
+{
+	int			i;
+	LogicalRepWorker *res = NULL;
+
+	Assert(LWLockHeldByMe(LogicalRepWorkerLock));
+
+	/* Search for attached worker for a given subscription id. */
+	for (i = 0; i < max_logical_replication_workers; i++)
+	{
+		LogicalRepWorker *w = &LogicalRepCtx->workers[i];
+
+		if (w->in_use && w->subid == subid && w->relid == relid &&
+			(!only_running || w->proc))
+		{
+			res = w;
+			break;
+		}
+	}
+
+	return res;
+}
+
+/*
+ * Similar to logicalrep_worker_find(), but returns list of all workers for
+ * the subscription, instead just one.
+ */
+List *
+logicalrep_workers_find(Oid subid, bool only_running)
+{
+	int			i;
+	List	   *res = NIL;
+
+	Assert(LWLockHeldByMe(LogicalRepWorkerLock));
+
+	/* Search for attached worker for a given subscription id. */
+	for (i = 0; i < max_logical_replication_workers; i++)
+	{
+		LogicalRepWorker *w = &LogicalRepCtx->workers[i];
+
+		if (w->in_use && w->subid == subid && (!only_running || w->proc))
+			res = lappend(res, w);
+	}
+
+	return res;
+}
+
+/*
+ * Start new apply background worker, if possible.
+ */
+void
+logicalrep_worker_launch(Oid dbid, Oid subid, const char *subname, Oid userid,
+						 Oid relid)
+{
+	BackgroundWorker bgw;
+	BackgroundWorkerHandle *bgw_handle;
+	uint16		generation;
+	int			i;
+	int			slot = 0;
+	LogicalRepWorker *worker = NULL;
+	int			nsyncworkers;
+	TimestampTz now;
+
+	ereport(DEBUG1,
+			(errmsg_internal("starting logical replication worker for subscription \"%s\"",
+							 subname)));
+
+	/* Report this after the initial starting message for consistency. */
+	if (max_replication_slots == 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
+				 errmsg("cannot start logical replication workers when max_replication_slots = 0")));
+
+	/*
+	 * We need to do the modification of the shared memory under lock so that
+	 * we have consistent view.
+	 */
+	LWLockAcquire(LogicalRepWorkerLock, LW_EXCLUSIVE);
+
+retry:
+	/* Find unused worker slot. */
+	for (i = 0; i < max_logical_replication_workers; i++)
+	{
+		LogicalRepWorker *w = &LogicalRepCtx->workers[i];
+
+		if (!w->in_use)
+		{
+			worker = w;
+			slot = i;
+			break;
+		}
+	}
+
+	nsyncworkers = logicalrep_sync_worker_count(subid);
+
+	now = GetCurrentTimestamp();
+
+	/*
+	 * If we didn't find a free slot, try to do garbage collection.  The
+	 * reason we do this is because if some worker failed to start up and its
+	 * parent has crashed while waiting, the in_use state was never cleared.
+	 */
+	if (worker == NULL || nsyncworkers >= max_sync_workers_per_subscription)
+	{
+		bool		did_cleanup = false;
+
+		for (i = 0; i < max_logical_replication_workers; i++)
+		{
+			LogicalRepWorker *w = &LogicalRepCtx->workers[i];
+
+			/*
+			 * If the worker was marked in use but didn't manage to attach in
+			 * time, clean it up.
+			 */
+			if (w->in_use && !w->proc &&
+				TimestampDifferenceExceeds(w->launch_time, now,
+										   wal_receiver_timeout))
+			{
+				elog(WARNING,
+					 "logical replication worker for subscription %u took too long to start; canceled",
+					 w->subid);
+
+				logicalrep_worker_cleanup(w);
+				did_cleanup = true;
+			}
+		}
+
+		if (did_cleanup)
+			goto retry;
+	}
+
+	/*
+	 * We don't allow to invoke more sync workers once we have reached the sync
+	 * worker limit per subscription. So, just return silently as we might get
+	 * here because of an otherwise harmless race condition.
+	 */
+	if (OidIsValid(relid) && nsyncworkers >= max_sync_workers_per_subscription)
+	{
+		LWLockRelease(LogicalRepWorkerLock);
+		return;
+	}
+
+	/*
+	 * However if there are no more free worker slots, inform user about it
+	 * before exiting.
+	 */
+	if (worker == NULL)
+	{
+		LWLockRelease(LogicalRepWorkerLock);
+		ereport(WARNING,
+				(errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
+				 errmsg("out of logical replication worker slots"),
+				 errhint("You might need to increase max_logical_replication_workers.")));
+		return;
+	}
+
+	/* Prepare the worker slot. */
+	worker->launch_time = now;
+	worker->in_use = true;
+	worker->generation++;
+	worker->proc = NULL;
+	worker->dbid = dbid;
+	worker->userid = userid;
+	worker->subid = subid;
+	worker->relid = relid;
+	worker->relstate = SUBREL_STATE_UNKNOWN;
+	worker->relstate_lsn = InvalidXLogRecPtr;
+	worker->last_lsn = InvalidXLogRecPtr;
+	TIMESTAMP_NOBEGIN(worker->last_send_time);
+	TIMESTAMP_NOBEGIN(worker->last_recv_time);
+	worker->reply_lsn = InvalidXLogRecPtr;
+	TIMESTAMP_NOBEGIN(worker->reply_time);
+
+	/* Before releasing lock, remember generation for future identification. */
+	generation = worker->generation;
+
+	LWLockRelease(LogicalRepWorkerLock);
+
+	/* Register the new dynamic worker. */
+	memset(&bgw, 0, sizeof(bgw));
+	bgw.bgw_flags = BGWORKER_SHMEM_ACCESS |
+		BGWORKER_BACKEND_DATABASE_CONNECTION;
+	bgw.bgw_start_time = BgWorkerStart_RecoveryFinished;
+	snprintf(bgw.bgw_library_name, BGW_MAXLEN, "postgres");
+	snprintf(bgw.bgw_function_name, BGW_MAXLEN, "ApplyWorkerMain");
+	if (OidIsValid(relid))
+		snprintf(bgw.bgw_name, BGW_MAXLEN,
+				 "logical replication worker for subscription %u sync %u", subid, relid);
+	else
+		snprintf(bgw.bgw_name, BGW_MAXLEN,
+				 "logical replication worker for subscription %u", subid);
+	snprintf(bgw.bgw_type, BGW_MAXLEN, "logical replication worker");
+
+	bgw.bgw_restart_time = BGW_NEVER_RESTART;
+	bgw.bgw_notify_pid = MyProcPid;
+	bgw.bgw_main_arg = Int32GetDatum(slot);
+
+	if (!RegisterDynamicBackgroundWorker(&bgw, &bgw_handle))
+	{
+		/* Failed to start worker, so clean up the worker slot. */
+		LWLockAcquire(LogicalRepWorkerLock, LW_EXCLUSIVE);
+		Assert(generation == worker->generation);
+		logicalrep_worker_cleanup(worker);
+		LWLockRelease(LogicalRepWorkerLock);
+
+		ereport(WARNING,
+				(errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
+				 errmsg("out of background worker slots"),
+				 errhint("You might need to increase max_worker_processes.")));
+		return;
+	}
+
+	/* Now wait until it attaches. */
+	WaitForReplicationWorkerAttach(worker, generation, bgw_handle);
+}
+
+/*
+ * Stop the logical replication worker for subid/relid, if any, and wait until
+ * it detaches from the slot.
+ */
+void
+logicalrep_worker_stop(Oid subid, Oid relid)
+{
+	LogicalRepWorker *worker;
+	uint16		generation;
+
+	LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
+
+	worker = logicalrep_worker_find(subid, relid, false);
+
+	/* No worker, nothing to do. */
+	if (!worker)
+	{
+		LWLockRelease(LogicalRepWorkerLock);
+		return;
+	}
+
+	/*
+	 * Remember which generation was our worker so we can check if what we see
+	 * is still the same one.
+	 */
+	generation = worker->generation;
+
+	/*
+	 * If we found a worker but it does not have proc set then it is still
+	 * starting up; wait for it to finish starting and then kill it.
+	 */
+	while (worker->in_use && !worker->proc)
+	{
+		int			rc;
+
+		LWLockRelease(LogicalRepWorkerLock);
+
+		/* Wait a bit --- we don't expect to have to wait long. */
+		rc = WaitLatch(MyLatch,
+					   WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
+					   10L, WAIT_EVENT_BGWORKER_STARTUP);
+
+		if (rc & WL_LATCH_SET)
+		{
+			ResetLatch(MyLatch);
+			CHECK_FOR_INTERRUPTS();
+		}
+
+		/* Recheck worker status. */
+		LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
+
+		/*
+		 * Check whether the worker slot is no longer used, which would mean
+		 * that the worker has exited, or whether the worker generation is
+		 * different, meaning that a different worker has taken the slot.
+		 */
+		if (!worker->in_use || worker->generation != generation)
+		{
+			LWLockRelease(LogicalRepWorkerLock);
+			return;
+		}
+
+		/* Worker has assigned proc, so it has started. */
+		if (worker->proc)
+			break;
+	}
+
+	/* Now terminate the worker ... */
+	kill(worker->proc->pid, SIGTERM);
+
+	/* ... and wait for it to die. */
+	for (;;)
+	{
+		int			rc;
+
+		/* is it gone? */
+		if (!worker->proc || worker->generation != generation)
+			break;
+
+		LWLockRelease(LogicalRepWorkerLock);
+
+		/* Wait a bit --- we don't expect to have to wait long. */
+		rc = WaitLatch(MyLatch,
+					   WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
+					   10L, WAIT_EVENT_BGWORKER_SHUTDOWN);
+
+		if (rc & WL_LATCH_SET)
+		{
+			ResetLatch(MyLatch);
+			CHECK_FOR_INTERRUPTS();
+		}
+
+		LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
+	}
+
+	LWLockRelease(LogicalRepWorkerLock);
+}
+
+/*
+ * Wake up (using latch) any logical replication worker for specified sub/rel.
+ */
+void
+logicalrep_worker_wakeup(Oid subid, Oid relid)
+{
+	LogicalRepWorker *worker;
+
+	LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
+
+	worker = logicalrep_worker_find(subid, relid, true);
+
+	if (worker)
+		logicalrep_worker_wakeup_ptr(worker);
+
+	LWLockRelease(LogicalRepWorkerLock);
+}
+
+/*
+ * Wake up (using latch) the specified logical replication worker.
+ *
+ * Caller must hold lock, else worker->proc could change under us.
+ */
+void
+logicalrep_worker_wakeup_ptr(LogicalRepWorker *worker)
+{
+	Assert(LWLockHeldByMe(LogicalRepWorkerLock));
+
+	SetLatch(&worker->proc->procLatch);
+}
+
+/*
+ * Attach to a slot.
+ */
+void
+logicalrep_worker_attach(int slot)
+{
+	/* Block concurrent access. */
+	LWLockAcquire(LogicalRepWorkerLock, LW_EXCLUSIVE);
+
+	Assert(slot >= 0 && slot < max_logical_replication_workers);
+	MyLogicalRepWorker = &LogicalRepCtx->workers[slot];
+
+	if (!MyLogicalRepWorker->in_use)
+	{
+		LWLockRelease(LogicalRepWorkerLock);
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("logical replication worker slot %d is empty, cannot attach",
+						slot)));
+	}
+
+	if (MyLogicalRepWorker->proc)
+	{
+		LWLockRelease(LogicalRepWorkerLock);
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("logical replication worker slot %d is already used by "
+						"another worker, cannot attach", slot)));
+	}
+
+	MyLogicalRepWorker->proc = MyProc;
+	before_shmem_exit(logicalrep_worker_onexit, (Datum) 0);
+
+	LWLockRelease(LogicalRepWorkerLock);
+}
+
+/*
+ * Detach the worker (cleans up the worker info).
+ */
+static void
+logicalrep_worker_detach(void)
+{
+	/* Block concurrent access. */
+	LWLockAcquire(LogicalRepWorkerLock, LW_EXCLUSIVE);
+
+	logicalrep_worker_cleanup(MyLogicalRepWorker);
+
+	LWLockRelease(LogicalRepWorkerLock);
+}
+
+/*
+ * Clean up worker info.
+ */
+static void
+logicalrep_worker_cleanup(LogicalRepWorker *worker)
+{
+	Assert(LWLockHeldByMeInMode(LogicalRepWorkerLock, LW_EXCLUSIVE));
+
+	worker->in_use = false;
+	worker->proc = NULL;
+	worker->dbid = InvalidOid;
+	worker->userid = InvalidOid;
+	worker->subid = InvalidOid;
+	worker->relid = InvalidOid;
+}
+
+/*
+ * Cleanup function for logical replication launcher.
+ *
+ * Called on logical replication launcher exit.
+ */
+static void
+logicalrep_launcher_onexit(int code, Datum arg)
+{
+	LogicalRepCtx->launcher_pid = 0;
+}
+
+/*
+ * Cleanup function.
+ *
+ * Called on logical replication worker exit.
+ */
+static void
+logicalrep_worker_onexit(int code, Datum arg)
+{
+	/* Disconnect gracefully from the remote side. */
+	if (LogRepWorkerWalRcvConn)
+		walrcv_disconnect(LogRepWorkerWalRcvConn);
+
+	logicalrep_worker_detach();
+
+	ApplyLauncherWakeup();
+}
+
+/*
+ * Count the number of registered (not necessarily running) sync workers
+ * for a subscription.
+ */
+int
+logicalrep_sync_worker_count(Oid subid)
+{
+	int			i;
+	int			res = 0;
+
+	Assert(LWLockHeldByMe(LogicalRepWorkerLock));
+
+	/* Search for attached worker for a given subscription id. */
+	for (i = 0; i < max_logical_replication_workers; i++)
+	{
+		LogicalRepWorker *w = &LogicalRepCtx->workers[i];
+
+		if (w->subid == subid && OidIsValid(w->relid))
+			res++;
+	}
+
+	return res;
+}
+
+/*
+ * ApplyLauncherShmemSize
+ *		Compute space needed for replication launcher shared memory
+ */
+Size
+ApplyLauncherShmemSize(void)
+{
+	Size		size;
+
+	/*
+	 * Need the fixed struct and the array of LogicalRepWorker.
+	 */
+	size = sizeof(LogicalRepCtxStruct);
+	size = MAXALIGN(size);
+	size = add_size(size, mul_size(max_logical_replication_workers,
+								   sizeof(LogicalRepWorker)));
+	return size;
+}
+
+/*
+ * ApplyLauncherRegister
+ *		Register a background worker running the logical replication launcher.
+ */
+void
+ApplyLauncherRegister(void)
+{
+	BackgroundWorker bgw;
+
+	if (max_logical_replication_workers == 0)
+		return;
+
+	memset(&bgw, 0, sizeof(bgw));
+	bgw.bgw_flags = BGWORKER_SHMEM_ACCESS |
+		BGWORKER_BACKEND_DATABASE_CONNECTION;
+	bgw.bgw_start_time = BgWorkerStart_RecoveryFinished;
+	snprintf(bgw.bgw_library_name, BGW_MAXLEN, "postgres");
+	snprintf(bgw.bgw_function_name, BGW_MAXLEN, "ApplyLauncherMain");
+	snprintf(bgw.bgw_name, BGW_MAXLEN,
+			 "logical replication launcher");
+	snprintf(bgw.bgw_type, BGW_MAXLEN,
+			 "logical replication launcher");
+	bgw.bgw_restart_time = 5;
+	bgw.bgw_notify_pid = 0;
+	bgw.bgw_main_arg = (Datum) 0;
+
+	RegisterBackgroundWorker(&bgw);
+}
+
+/*
+ * ApplyLauncherShmemInit
+ *		Allocate and initialize replication launcher shared memory
+ */
+void
+ApplyLauncherShmemInit(void)
+{
+	bool		found;
+
+	LogicalRepCtx = (LogicalRepCtxStruct *)
+		ShmemInitStruct("Logical Replication Launcher Data",
+						ApplyLauncherShmemSize(),
+						&found);
+
+	if (!found)
+	{
+		int			slot;
+
+		memset(LogicalRepCtx, 0, ApplyLauncherShmemSize());
+
+		/* Initialize memory and spin locks for each worker slot. */
+		for (slot = 0; slot < max_logical_replication_workers; slot++)
+		{
+			LogicalRepWorker *worker = &LogicalRepCtx->workers[slot];
+
+			memset(worker, 0, sizeof(LogicalRepWorker));
+			SpinLockInit(&worker->relmutex);
+		}
+	}
+}
+
+/*
+ * Wakeup the launcher on commit if requested.
+ */
+void
+AtEOXact_ApplyLauncher(bool isCommit)
+{
+	if (isCommit)
+	{
+		if (on_commit_launcher_wakeup)
+			ApplyLauncherWakeup();
+	}
+
+	on_commit_launcher_wakeup = false;
+}
+
+/*
+ * Request wakeup of the launcher on commit of the transaction.
+ *
+ * This is used to send launcher signal to stop sleeping and process the
+ * subscriptions when current transaction commits. Should be used when new
+ * tuple was added to the pg_subscription catalog.
+*/
+void
+ApplyLauncherWakeupAtCommit(void)
+{
+	if (!on_commit_launcher_wakeup)
+		on_commit_launcher_wakeup = true;
+}
+
+static void
+ApplyLauncherWakeup(void)
+{
+	if (LogicalRepCtx->launcher_pid != 0)
+		kill(LogicalRepCtx->launcher_pid, SIGUSR1);
+}
+
+/*
+ * Main loop for the apply launcher process.
+ */
+void
+ApplyLauncherMain(Datum main_arg)
+{
+	TimestampTz last_start_time = 0;
+
+	ereport(DEBUG1,
+			(errmsg_internal("logical replication launcher started")));
+
+	before_shmem_exit(logicalrep_launcher_onexit, (Datum) 0);
+
+	Assert(LogicalRepCtx->launcher_pid == 0);
+	LogicalRepCtx->launcher_pid = MyProcPid;
+
+	/* Establish signal handlers. */
+	pqsignal(SIGHUP, SignalHandlerForConfigReload);
+	pqsignal(SIGTERM, die);
+	BackgroundWorkerUnblockSignals();
+
+	/*
+	 * Establish connection to nailed catalogs (we only ever access
+	 * pg_subscription).
+	 */
+	BackgroundWorkerInitializeConnection(NULL, NULL, 0);
+
+	/* Enter main loop */
+	for (;;)
+	{
+		int			rc;
+		List	   *sublist;
+		ListCell   *lc;
+		MemoryContext subctx;
+		MemoryContext oldctx;
+		TimestampTz now;
+		long		wait_time = DEFAULT_NAPTIME_PER_CYCLE;
+
+		CHECK_FOR_INTERRUPTS();
+
+		now = GetCurrentTimestamp();
+
+		/* Limit the start retry to once a wal_retrieve_retry_interval */
+		if (TimestampDifferenceExceeds(last_start_time, now,
+									   wal_retrieve_retry_interval))
+		{
+			/* Use temporary context for the database list and worker info. */
+			subctx = AllocSetContextCreate(TopMemoryContext,
+										   "Logical Replication Launcher sublist",
+										   ALLOCSET_DEFAULT_SIZES);
+			oldctx = MemoryContextSwitchTo(subctx);
+
+			/* search for subscriptions to start or stop. */
+			sublist = get_subscription_list();
+
+			/* Start the missing workers for enabled subscriptions. */
+			foreach(lc, sublist)
+			{
+				Subscription *sub = (Subscription *) lfirst(lc);
+				LogicalRepWorker *w;
+
+				if (!sub->enabled)
+					continue;
+
+				LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
+				w = logicalrep_worker_find(sub->oid, InvalidOid, false);
+				LWLockRelease(LogicalRepWorkerLock);
+
+				if (w == NULL)
+				{
+					last_start_time = now;
+					wait_time = wal_retrieve_retry_interval;
+
+					logicalrep_worker_launch(sub->dbid, sub->oid, sub->name,
+											 sub->owner, InvalidOid);
+				}
+			}
+
+			/* Switch back to original memory context. */
+			MemoryContextSwitchTo(oldctx);
+			/* Clean the temporary memory. */
+			MemoryContextDelete(subctx);
+		}
+		else
+		{
+			/*
+			 * The wait in previous cycle was interrupted in less than
+			 * wal_retrieve_retry_interval since last worker was started, this
+			 * usually means crash of the worker, so we should retry in
+			 * wal_retrieve_retry_interval again.
+			 */
+			wait_time = wal_retrieve_retry_interval;
+		}
+
+		/* Wait for more work. */
+		rc = WaitLatch(MyLatch,
+					   WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
+					   wait_time,
+					   WAIT_EVENT_LOGICAL_LAUNCHER_MAIN);
+
+		if (rc & WL_LATCH_SET)
+		{
+			ResetLatch(MyLatch);
+			CHECK_FOR_INTERRUPTS();
+		}
+
+		if (ConfigReloadPending)
+		{
+			ConfigReloadPending = false;
+			ProcessConfigFile(PGC_SIGHUP);
+		}
+	}
+
+	/* Not reachable */
+}
+
+/*
+ * Is current process the logical replication launcher?
+ */
+bool
+IsLogicalLauncher(void)
+{
+	return LogicalRepCtx->launcher_pid == MyProcPid;
+}
+
+/*
+ * Returns state of the subscriptions.
+ */
+Datum
+pg_stat_get_subscription(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_SUBSCRIPTION_COLS	8
+	Oid			subid = PG_ARGISNULL(0) ? InvalidOid : PG_GETARG_OID(0);
+	int			i;
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+	TupleDesc	tupdesc;
+	Tuplestorestate *tupstore;
+	MemoryContext per_query_ctx;
+	MemoryContext oldcontext;
+
+	/* check to see if caller supports us returning a tuplestore */
+	if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("set-valued function called in context that cannot accept a set")));
+	if (!(rsinfo->allowedModes & SFRM_Materialize))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("materialize mode required, but it is not allowed in this context")));
+
+	/* Build a tuple descriptor for our result type */
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+		elog(ERROR, "return type must be a row type");
+
+	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
+	oldcontext = MemoryContextSwitchTo(per_query_ctx);
+
+	tupstore = tuplestore_begin_heap(true, false, work_mem);
+	rsinfo->returnMode = SFRM_Materialize;
+	rsinfo->setResult = tupstore;
+	rsinfo->setDesc = tupdesc;
+
+	MemoryContextSwitchTo(oldcontext);
+
+	/* Make sure we get consistent view of the workers. */
+	LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
+
+	for (i = 0; i < max_logical_replication_workers; i++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_SUBSCRIPTION_COLS];
+		bool		nulls[PG_STAT_GET_SUBSCRIPTION_COLS];
+		int			worker_pid;
+		LogicalRepWorker worker;
+
+		memcpy(&worker, &LogicalRepCtx->workers[i],
+			   sizeof(LogicalRepWorker));
+		if (!worker.proc || !IsBackendPid(worker.proc->pid))
+			continue;
+
+		if (OidIsValid(subid) && worker.subid != subid)
+			continue;
+
+		worker_pid = worker.proc->pid;
+
+		MemSet(values, 0, sizeof(values));
+		MemSet(nulls, 0, sizeof(nulls));
+
+		values[0] = ObjectIdGetDatum(worker.subid);
+		if (OidIsValid(worker.relid))
+			values[1] = ObjectIdGetDatum(worker.relid);
+		else
+			nulls[1] = true;
+		values[2] = Int32GetDatum(worker_pid);
+		if (XLogRecPtrIsInvalid(worker.last_lsn))
+			nulls[3] = true;
+		else
+			values[3] = LSNGetDatum(worker.last_lsn);
+		if (worker.last_send_time == 0)
+			nulls[4] = true;
+		else
+			values[4] = TimestampTzGetDatum(worker.last_send_time);
+		if (worker.last_recv_time == 0)
+			nulls[5] = true;
+		else
+			values[5] = TimestampTzGetDatum(worker.last_recv_time);
+		if (XLogRecPtrIsInvalid(worker.reply_lsn))
+			nulls[6] = true;
+		else
+			values[6] = LSNGetDatum(worker.reply_lsn);
+		if (worker.reply_time == 0)
+			nulls[7] = true;
+		else
+			values[7] = TimestampTzGetDatum(worker.reply_time);
+
+		tuplestore_putvalues(tupstore, tupdesc, values, nulls);
+
+		/*
+		 * If only a single subscription was requested, and we found it,
+		 * break.
+		 */
+		if (OidIsValid(subid))
+			break;
+	}
+
+	LWLockRelease(LogicalRepWorkerLock);
+
+	/* clean up and return the tuplestore */
+	tuplestore_donestoring(tupstore);
+
+	return (Datum) 0;
+}
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
new file mode 100644
index 0000000..f7d1491
--- /dev/null
+++ b/src/backend/replication/logical/logical.c
@@ -0,0 +1,1840 @@
+/*-------------------------------------------------------------------------
+ * logical.c
+ *	   PostgreSQL logical decoding coordination
+ *
+ * Copyright (c) 2012-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/logical.c
+ *
+ * NOTES
+ *	  This file coordinates interaction between the various modules that
+ *	  together provide logical decoding, primarily by providing so
+ *	  called LogicalDecodingContexts. The goal is to encapsulate most of the
+ *	  internal complexity for consumers of logical decoding, so they can
+ *	  create and consume a changestream with a low amount of code. Builtin
+ *	  consumers are the walsender and SQL SRF interface, but it's possible to
+ *	  add further ones without changing core code, e.g. to consume changes in
+ *	  a bgworker.
+ *
+ *	  The idea is that a consumer provides three callbacks, one to read WAL,
+ *	  one to prepare a data write, and a final one for actually writing since
+ *	  their implementation depends on the type of consumer.  Check
+ *	  logicalfuncs.c for an example implementation of a fairly simple consumer
+ *	  and an implementation of a WAL reading callback that's suitable for
+ *	  simple consumers.
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/xact.h"
+#include "access/xlog_internal.h"
+#include "fmgr.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "replication/decode.h"
+#include "replication/logical.h"
+#include "replication/origin.h"
+#include "replication/reorderbuffer.h"
+#include "replication/snapbuild.h"
+#include "storage/proc.h"
+#include "storage/procarray.h"
+#include "utils/builtins.h"
+#include "utils/memutils.h"
+
+/* data for errcontext callback */
+typedef struct LogicalErrorCallbackState
+{
+	LogicalDecodingContext *ctx;
+	const char *callback_name;
+	XLogRecPtr	report_location;
+} LogicalErrorCallbackState;
+
+/* wrappers around output plugin callbacks */
+static void output_plugin_error_callback(void *arg);
+static void startup_cb_wrapper(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
+							   bool is_init);
+static void shutdown_cb_wrapper(LogicalDecodingContext *ctx);
+static void begin_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn);
+static void commit_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+							  XLogRecPtr commit_lsn);
+static void begin_prepare_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn);
+static void prepare_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+							   XLogRecPtr prepare_lsn);
+static void commit_prepared_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+									   XLogRecPtr commit_lsn);
+static void rollback_prepared_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+										 XLogRecPtr prepare_end_lsn, TimestampTz prepare_time);
+static void change_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+							  Relation relation, ReorderBufferChange *change);
+static void truncate_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+								int nrelations, Relation relations[], ReorderBufferChange *change);
+static void message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+							   XLogRecPtr message_lsn, bool transactional,
+							   const char *prefix, Size message_size, const char *message);
+
+/* streaming callbacks */
+static void stream_start_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+									XLogRecPtr first_lsn);
+static void stream_stop_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+								   XLogRecPtr last_lsn);
+static void stream_abort_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+									XLogRecPtr abort_lsn);
+static void stream_prepare_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+									  XLogRecPtr prepare_lsn);
+static void stream_commit_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+									 XLogRecPtr commit_lsn);
+static void stream_change_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+									 Relation relation, ReorderBufferChange *change);
+static void stream_message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+									  XLogRecPtr message_lsn, bool transactional,
+									  const char *prefix, Size message_size, const char *message);
+static void stream_truncate_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+									   int nrelations, Relation relations[], ReorderBufferChange *change);
+
+static void LoadOutputPlugin(OutputPluginCallbacks *callbacks, const char *plugin);
+
+/*
+ * Make sure the current settings & environment are capable of doing logical
+ * decoding.
+ */
+void
+CheckLogicalDecodingRequirements(void)
+{
+	CheckSlotRequirements();
+
+	/*
+	 * NB: Adding a new requirement likely means that RestoreSlotFromDisk()
+	 * needs the same check.
+	 */
+
+	if (wal_level < WAL_LEVEL_LOGICAL)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("logical decoding requires wal_level >= logical")));
+
+	if (MyDatabaseId == InvalidOid)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("logical decoding requires a database connection")));
+
+	/* ----
+	 * TODO: We got to change that someday soon...
+	 *
+	 * There's basically three things missing to allow this:
+	 * 1) We need to be able to correctly and quickly identify the timeline a
+	 *	  LSN belongs to
+	 * 2) We need to force hot_standby_feedback to be enabled at all times so
+	 *	  the primary cannot remove rows we need.
+	 * 3) support dropping replication slots referring to a database, in
+	 *	  dbase_redo. There can't be any active ones due to HS recovery
+	 *	  conflicts, so that should be relatively easy.
+	 * ----
+	 */
+	if (RecoveryInProgress())
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("logical decoding cannot be used while in recovery")));
+}
+
+/*
+ * Helper function for CreateInitDecodingContext() and
+ * CreateDecodingContext() performing common tasks.
+ */
+static LogicalDecodingContext *
+StartupDecodingContext(List *output_plugin_options,
+					   XLogRecPtr start_lsn,
+					   TransactionId xmin_horizon,
+					   bool need_full_snapshot,
+					   bool fast_forward,
+					   XLogReaderRoutine *xl_routine,
+					   LogicalOutputPluginWriterPrepareWrite prepare_write,
+					   LogicalOutputPluginWriterWrite do_write,
+					   LogicalOutputPluginWriterUpdateProgress update_progress)
+{
+	ReplicationSlot *slot;
+	MemoryContext context,
+				old_context;
+	LogicalDecodingContext *ctx;
+
+	/* shorter lines... */
+	slot = MyReplicationSlot;
+
+	context = AllocSetContextCreate(CurrentMemoryContext,
+									"Logical decoding context",
+									ALLOCSET_DEFAULT_SIZES);
+	old_context = MemoryContextSwitchTo(context);
+	ctx = palloc0(sizeof(LogicalDecodingContext));
+
+	ctx->context = context;
+
+	/*
+	 * (re-)load output plugins, so we detect a bad (removed) output plugin
+	 * now.
+	 */
+	if (!fast_forward)
+		LoadOutputPlugin(&ctx->callbacks, NameStr(slot->data.plugin));
+
+	/*
+	 * Now that the slot's xmin has been set, we can announce ourselves as a
+	 * logical decoding backend which doesn't need to be checked individually
+	 * when computing the xmin horizon because the xmin is enforced via
+	 * replication slots.
+	 *
+	 * We can only do so if we're outside of a transaction (i.e. the case when
+	 * streaming changes via walsender), otherwise an already setup
+	 * snapshot/xid would end up being ignored. That's not a particularly
+	 * bothersome restriction since the SQL interface can't be used for
+	 * streaming anyway.
+	 */
+	if (!IsTransactionOrTransactionBlock())
+	{
+		LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
+		MyProc->statusFlags |= PROC_IN_LOGICAL_DECODING;
+		ProcGlobal->statusFlags[MyProc->pgxactoff] = MyProc->statusFlags;
+		LWLockRelease(ProcArrayLock);
+	}
+
+	ctx->slot = slot;
+
+	ctx->reader = XLogReaderAllocate(wal_segment_size, NULL, xl_routine, ctx);
+	if (!ctx->reader)
+		ereport(ERROR,
+				(errcode(ERRCODE_OUT_OF_MEMORY),
+				 errmsg("out of memory")));
+
+	ctx->reorder = ReorderBufferAllocate();
+	ctx->snapshot_builder =
+		AllocateSnapshotBuilder(ctx->reorder, xmin_horizon, start_lsn,
+								need_full_snapshot, slot->data.initial_consistent_point);
+
+	ctx->reorder->private_data = ctx;
+
+	/* wrap output plugin callbacks, so we can add error context information */
+	ctx->reorder->begin = begin_cb_wrapper;
+	ctx->reorder->apply_change = change_cb_wrapper;
+	ctx->reorder->apply_truncate = truncate_cb_wrapper;
+	ctx->reorder->commit = commit_cb_wrapper;
+	ctx->reorder->message = message_cb_wrapper;
+
+	/*
+	 * To support streaming, we require start/stop/abort/commit/change
+	 * callbacks. The message and truncate callbacks are optional, similar to
+	 * regular output plugins. We however enable streaming when at least one
+	 * of the methods is enabled so that we can easily identify missing
+	 * methods.
+	 *
+	 * We decide it here, but only check it later in the wrappers.
+	 */
+	ctx->streaming = (ctx->callbacks.stream_start_cb != NULL) ||
+		(ctx->callbacks.stream_stop_cb != NULL) ||
+		(ctx->callbacks.stream_abort_cb != NULL) ||
+		(ctx->callbacks.stream_commit_cb != NULL) ||
+		(ctx->callbacks.stream_change_cb != NULL) ||
+		(ctx->callbacks.stream_message_cb != NULL) ||
+		(ctx->callbacks.stream_truncate_cb != NULL);
+
+	/*
+	 * streaming callbacks
+	 *
+	 * stream_message and stream_truncate callbacks are optional, so we do not
+	 * fail with ERROR when missing, but the wrappers simply do nothing. We
+	 * must set the ReorderBuffer callbacks to something, otherwise the calls
+	 * from there will crash (we don't want to move the checks there).
+	 */
+	ctx->reorder->stream_start = stream_start_cb_wrapper;
+	ctx->reorder->stream_stop = stream_stop_cb_wrapper;
+	ctx->reorder->stream_abort = stream_abort_cb_wrapper;
+	ctx->reorder->stream_prepare = stream_prepare_cb_wrapper;
+	ctx->reorder->stream_commit = stream_commit_cb_wrapper;
+	ctx->reorder->stream_change = stream_change_cb_wrapper;
+	ctx->reorder->stream_message = stream_message_cb_wrapper;
+	ctx->reorder->stream_truncate = stream_truncate_cb_wrapper;
+
+
+	/*
+	 * To support two-phase logical decoding, we require
+	 * begin_prepare/prepare/commit-prepare/abort-prepare callbacks. The
+	 * filter_prepare callback is optional. We however enable two-phase
+	 * logical decoding when at least one of the methods is enabled so that we
+	 * can easily identify missing methods.
+	 *
+	 * We decide it here, but only check it later in the wrappers.
+	 */
+	ctx->twophase = (ctx->callbacks.begin_prepare_cb != NULL) ||
+		(ctx->callbacks.prepare_cb != NULL) ||
+		(ctx->callbacks.commit_prepared_cb != NULL) ||
+		(ctx->callbacks.rollback_prepared_cb != NULL) ||
+		(ctx->callbacks.stream_prepare_cb != NULL) ||
+		(ctx->callbacks.filter_prepare_cb != NULL);
+
+	/*
+	 * Callback to support decoding at prepare time.
+	 */
+	ctx->reorder->begin_prepare = begin_prepare_cb_wrapper;
+	ctx->reorder->prepare = prepare_cb_wrapper;
+	ctx->reorder->commit_prepared = commit_prepared_cb_wrapper;
+	ctx->reorder->rollback_prepared = rollback_prepared_cb_wrapper;
+
+	ctx->out = makeStringInfo();
+	ctx->prepare_write = prepare_write;
+	ctx->write = do_write;
+	ctx->update_progress = update_progress;
+
+	ctx->output_plugin_options = output_plugin_options;
+
+	ctx->fast_forward = fast_forward;
+
+	MemoryContextSwitchTo(old_context);
+
+	return ctx;
+}
+
+/*
+ * Create a new decoding context, for a new logical slot.
+ *
+ * plugin -- contains the name of the output plugin
+ * output_plugin_options -- contains options passed to the output plugin
+ * need_full_snapshot -- if true, must obtain a snapshot able to read all
+ *		tables; if false, one that can read only catalogs is acceptable.
+ * restart_lsn -- if given as invalid, it's this routine's responsibility to
+ *		mark WAL as reserved by setting a convenient restart_lsn for the slot.
+ *		Otherwise, we set for decoding to start from the given LSN without
+ *		marking WAL reserved beforehand.  In that scenario, it's up to the
+ *		caller to guarantee that WAL remains available.
+ * xl_routine -- XLogReaderRoutine for underlying XLogReader
+ * prepare_write, do_write, update_progress --
+ *		callbacks that perform the use-case dependent, actual, work.
+ *
+ * Needs to be called while in a memory context that's at least as long lived
+ * as the decoding context because further memory contexts will be created
+ * inside it.
+ *
+ * Returns an initialized decoding context after calling the output plugin's
+ * startup function.
+ */
+LogicalDecodingContext *
+CreateInitDecodingContext(const char *plugin,
+						  List *output_plugin_options,
+						  bool need_full_snapshot,
+						  XLogRecPtr restart_lsn,
+						  XLogReaderRoutine *xl_routine,
+						  LogicalOutputPluginWriterPrepareWrite prepare_write,
+						  LogicalOutputPluginWriterWrite do_write,
+						  LogicalOutputPluginWriterUpdateProgress update_progress)
+{
+	TransactionId xmin_horizon = InvalidTransactionId;
+	ReplicationSlot *slot;
+	NameData	plugin_name;
+	LogicalDecodingContext *ctx;
+	MemoryContext old_context;
+
+	/* shorter lines... */
+	slot = MyReplicationSlot;
+
+	/* first some sanity checks that are unlikely to be violated */
+	if (slot == NULL)
+		elog(ERROR, "cannot perform logical decoding without an acquired slot");
+
+	if (plugin == NULL)
+		elog(ERROR, "cannot initialize logical decoding without a specified plugin");
+
+	/* Make sure the passed slot is suitable. These are user facing errors. */
+	if (SlotIsPhysical(slot))
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("cannot use physical replication slot for logical decoding")));
+
+	if (slot->data.database != MyDatabaseId)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("replication slot \"%s\" was not created in this database",
+						NameStr(slot->data.name))));
+
+	if (IsTransactionState() &&
+		GetTopTransactionIdIfAny() != InvalidTransactionId)
+		ereport(ERROR,
+				(errcode(ERRCODE_ACTIVE_SQL_TRANSACTION),
+				 errmsg("cannot create logical replication slot in transaction that has performed writes")));
+
+	/*
+	 * Register output plugin name with slot.  We need the mutex to avoid
+	 * concurrent reading of a partially copied string.  But we don't want any
+	 * complicated code while holding a spinlock, so do namestrcpy() outside.
+	 */
+	namestrcpy(&plugin_name, plugin);
+	SpinLockAcquire(&slot->mutex);
+	slot->data.plugin = plugin_name;
+	SpinLockRelease(&slot->mutex);
+
+	if (XLogRecPtrIsInvalid(restart_lsn))
+		ReplicationSlotReserveWal();
+	else
+	{
+		SpinLockAcquire(&slot->mutex);
+		slot->data.restart_lsn = restart_lsn;
+		SpinLockRelease(&slot->mutex);
+	}
+
+	/* ----
+	 * This is a bit tricky: We need to determine a safe xmin horizon to start
+	 * decoding from, to avoid starting from a running xacts record referring
+	 * to xids whose rows have been vacuumed or pruned
+	 * already. GetOldestSafeDecodingTransactionId() returns such a value, but
+	 * without further interlock its return value might immediately be out of
+	 * date.
+	 *
+	 * So we have to acquire the ProcArrayLock to prevent computation of new
+	 * xmin horizons by other backends, get the safe decoding xid, and inform
+	 * the slot machinery about the new limit. Once that's done the
+	 * ProcArrayLock can be released as the slot machinery now is
+	 * protecting against vacuum.
+	 *
+	 * Note that, temporarily, the data, not just the catalog, xmin has to be
+	 * reserved if a data snapshot is to be exported.  Otherwise the initial
+	 * data snapshot created here is not guaranteed to be valid. After that
+	 * the data xmin doesn't need to be managed anymore and the global xmin
+	 * should be recomputed. As we are fine with losing the pegged data xmin
+	 * after crash - no chance a snapshot would get exported anymore - we can
+	 * get away with just setting the slot's
+	 * effective_xmin. ReplicationSlotRelease will reset it again.
+	 *
+	 * ----
+	 */
+	LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
+
+	xmin_horizon = GetOldestSafeDecodingTransactionId(!need_full_snapshot);
+
+	SpinLockAcquire(&slot->mutex);
+	slot->effective_catalog_xmin = xmin_horizon;
+	slot->data.catalog_xmin = xmin_horizon;
+	if (need_full_snapshot)
+		slot->effective_xmin = xmin_horizon;
+	SpinLockRelease(&slot->mutex);
+
+	ReplicationSlotsComputeRequiredXmin(true);
+
+	LWLockRelease(ProcArrayLock);
+
+	ReplicationSlotMarkDirty();
+	ReplicationSlotSave();
+
+	ctx = StartupDecodingContext(NIL, restart_lsn, xmin_horizon,
+								 need_full_snapshot, false,
+								 xl_routine, prepare_write, do_write,
+								 update_progress);
+
+	/* call output plugin initialization callback */
+	old_context = MemoryContextSwitchTo(ctx->context);
+	if (ctx->callbacks.startup_cb != NULL)
+		startup_cb_wrapper(ctx, &ctx->options, true);
+	MemoryContextSwitchTo(old_context);
+
+	/*
+	 * We allow decoding of prepared transactions iff the two_phase option is
+	 * enabled at the time of slot creation.
+	 */
+	ctx->twophase &= MyReplicationSlot->data.two_phase;
+
+	ctx->reorder->output_rewrites = ctx->options.receive_rewrites;
+
+	return ctx;
+}
+
+/*
+ * Create a new decoding context, for a logical slot that has previously been
+ * used already.
+ *
+ * start_lsn
+ *		The LSN at which to start decoding.  If InvalidXLogRecPtr, restart
+ *		from the slot's confirmed_flush; otherwise, start from the specified
+ *		location (but move it forwards to confirmed_flush if it's older than
+ *		that, see below).
+ *
+ * output_plugin_options
+ *		options passed to the output plugin.
+ *
+ * fast_forward
+ *		bypass the generation of logical changes.
+ *
+ * xl_routine
+ *		XLogReaderRoutine used by underlying xlogreader
+ *
+ * prepare_write, do_write, update_progress
+ *		callbacks that have to be filled to perform the use-case dependent,
+ *		actual work.
+ *
+ * Needs to be called while in a memory context that's at least as long lived
+ * as the decoding context because further memory contexts will be created
+ * inside it.
+ *
+ * Returns an initialized decoding context after calling the output plugin's
+ * startup function.
+ */
+LogicalDecodingContext *
+CreateDecodingContext(XLogRecPtr start_lsn,
+					  List *output_plugin_options,
+					  bool fast_forward,
+					  XLogReaderRoutine *xl_routine,
+					  LogicalOutputPluginWriterPrepareWrite prepare_write,
+					  LogicalOutputPluginWriterWrite do_write,
+					  LogicalOutputPluginWriterUpdateProgress update_progress)
+{
+	LogicalDecodingContext *ctx;
+	ReplicationSlot *slot;
+	MemoryContext old_context;
+
+	/* shorter lines... */
+	slot = MyReplicationSlot;
+
+	/* first some sanity checks that are unlikely to be violated */
+	if (slot == NULL)
+		elog(ERROR, "cannot perform logical decoding without an acquired slot");
+
+	/* make sure the passed slot is suitable, these are user facing errors */
+	if (SlotIsPhysical(slot))
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("cannot use physical replication slot for logical decoding")));
+
+	if (slot->data.database != MyDatabaseId)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("replication slot \"%s\" was not created in this database",
+						NameStr(slot->data.name))));
+
+	if (start_lsn == InvalidXLogRecPtr)
+	{
+		/* continue from last position */
+		start_lsn = slot->data.confirmed_flush;
+	}
+	else if (start_lsn < slot->data.confirmed_flush)
+	{
+		/*
+		 * It might seem like we should error out in this case, but it's
+		 * pretty common for a client to acknowledge a LSN it doesn't have to
+		 * do anything for, and thus didn't store persistently, because the
+		 * xlog records didn't result in anything relevant for logical
+		 * decoding. Clients have to be able to do that to support synchronous
+		 * replication.
+		 */
+		elog(DEBUG1, "cannot stream from %X/%X, minimum is %X/%X, forwarding",
+			 LSN_FORMAT_ARGS(start_lsn),
+			 LSN_FORMAT_ARGS(slot->data.confirmed_flush));
+
+		start_lsn = slot->data.confirmed_flush;
+	}
+
+	ctx = StartupDecodingContext(output_plugin_options,
+								 start_lsn, InvalidTransactionId, false,
+								 fast_forward, xl_routine, prepare_write,
+								 do_write, update_progress);
+
+	/* call output plugin initialization callback */
+	old_context = MemoryContextSwitchTo(ctx->context);
+	if (ctx->callbacks.startup_cb != NULL)
+		startup_cb_wrapper(ctx, &ctx->options, false);
+	MemoryContextSwitchTo(old_context);
+
+	/*
+	 * We allow decoding of prepared transactions iff the two_phase option is
+	 * enabled at the time of slot creation.
+	 */
+	ctx->twophase &= MyReplicationSlot->data.two_phase;
+
+	ctx->reorder->output_rewrites = ctx->options.receive_rewrites;
+
+	ereport(LOG,
+			(errmsg("starting logical decoding for slot \"%s\"",
+					NameStr(slot->data.name)),
+			 errdetail("Streaming transactions committing after %X/%X, reading WAL from %X/%X.",
+					   LSN_FORMAT_ARGS(slot->data.confirmed_flush),
+					   LSN_FORMAT_ARGS(slot->data.restart_lsn))));
+
+	return ctx;
+}
+
+/*
+ * Returns true if a consistent initial decoding snapshot has been built.
+ */
+bool
+DecodingContextReady(LogicalDecodingContext *ctx)
+{
+	return SnapBuildCurrentState(ctx->snapshot_builder) == SNAPBUILD_CONSISTENT;
+}
+
+/*
+ * Read from the decoding slot, until it is ready to start extracting changes.
+ */
+void
+DecodingContextFindStartpoint(LogicalDecodingContext *ctx)
+{
+	ReplicationSlot *slot = ctx->slot;
+
+	/* Initialize from where to start reading WAL. */
+	XLogBeginRead(ctx->reader, slot->data.restart_lsn);
+
+	elog(DEBUG1, "searching for logical decoding starting point, starting at %X/%X",
+		 LSN_FORMAT_ARGS(slot->data.restart_lsn));
+
+	/* Wait for a consistent starting point */
+	for (;;)
+	{
+		XLogRecord *record;
+		char	   *err = NULL;
+
+		/* the read_page callback waits for new WAL */
+		record = XLogReadRecord(ctx->reader, &err);
+		if (err)
+			elog(ERROR, "%s", err);
+		if (!record)
+			elog(ERROR, "no record found"); /* shouldn't happen */
+
+		LogicalDecodingProcessRecord(ctx, ctx->reader);
+
+		/* only continue till we found a consistent spot */
+		if (DecodingContextReady(ctx))
+			break;
+
+		CHECK_FOR_INTERRUPTS();
+	}
+
+	SpinLockAcquire(&slot->mutex);
+	slot->data.confirmed_flush = ctx->reader->EndRecPtr;
+	slot->data.initial_consistent_point = ctx->reader->EndRecPtr;
+	SpinLockRelease(&slot->mutex);
+}
+
+/*
+ * Free a previously allocated decoding context, invoking the shutdown
+ * callback if necessary.
+ */
+void
+FreeDecodingContext(LogicalDecodingContext *ctx)
+{
+	if (ctx->callbacks.shutdown_cb != NULL)
+		shutdown_cb_wrapper(ctx);
+
+	ReorderBufferFree(ctx->reorder);
+	FreeSnapshotBuilder(ctx->snapshot_builder);
+	XLogReaderFree(ctx->reader);
+	MemoryContextDelete(ctx->context);
+}
+
+/*
+ * Prepare a write using the context's output routine.
+ */
+void
+OutputPluginPrepareWrite(struct LogicalDecodingContext *ctx, bool last_write)
+{
+	if (!ctx->accept_writes)
+		elog(ERROR, "writes are only accepted in commit, begin and change callbacks");
+
+	ctx->prepare_write(ctx, ctx->write_location, ctx->write_xid, last_write);
+	ctx->prepared_write = true;
+}
+
+/*
+ * Perform a write using the context's output routine.
+ */
+void
+OutputPluginWrite(struct LogicalDecodingContext *ctx, bool last_write)
+{
+	if (!ctx->prepared_write)
+		elog(ERROR, "OutputPluginPrepareWrite needs to be called before OutputPluginWrite");
+
+	ctx->write(ctx, ctx->write_location, ctx->write_xid, last_write);
+	ctx->prepared_write = false;
+}
+
+/*
+ * Update progress tracking (if supported).
+ */
+void
+OutputPluginUpdateProgress(struct LogicalDecodingContext *ctx)
+{
+	if (!ctx->update_progress)
+		return;
+
+	ctx->update_progress(ctx, ctx->write_location, ctx->write_xid);
+}
+
+/*
+ * Load the output plugin, lookup its output plugin init function, and check
+ * that it provides the required callbacks.
+ */
+static void
+LoadOutputPlugin(OutputPluginCallbacks *callbacks, const char *plugin)
+{
+	LogicalOutputPluginInit plugin_init;
+
+	plugin_init = (LogicalOutputPluginInit)
+		load_external_function(plugin, "_PG_output_plugin_init", false, NULL);
+
+	if (plugin_init == NULL)
+		elog(ERROR, "output plugins have to declare the _PG_output_plugin_init symbol");
+
+	/* ask the output plugin to fill the callback struct */
+	plugin_init(callbacks);
+
+	if (callbacks->begin_cb == NULL)
+		elog(ERROR, "output plugins have to register a begin callback");
+	if (callbacks->change_cb == NULL)
+		elog(ERROR, "output plugins have to register a change callback");
+	if (callbacks->commit_cb == NULL)
+		elog(ERROR, "output plugins have to register a commit callback");
+}
+
+static void
+output_plugin_error_callback(void *arg)
+{
+	LogicalErrorCallbackState *state = (LogicalErrorCallbackState *) arg;
+
+	/* not all callbacks have an associated LSN  */
+	if (state->report_location != InvalidXLogRecPtr)
+		errcontext("slot \"%s\", output plugin \"%s\", in the %s callback, associated LSN %X/%X",
+				   NameStr(state->ctx->slot->data.name),
+				   NameStr(state->ctx->slot->data.plugin),
+				   state->callback_name,
+				   LSN_FORMAT_ARGS(state->report_location));
+	else
+		errcontext("slot \"%s\", output plugin \"%s\", in the %s callback",
+				   NameStr(state->ctx->slot->data.name),
+				   NameStr(state->ctx->slot->data.plugin),
+				   state->callback_name);
+}
+
+static void
+startup_cb_wrapper(LogicalDecodingContext *ctx, OutputPluginOptions *opt, bool is_init)
+{
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "startup";
+	state.report_location = InvalidXLogRecPtr;
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = false;
+	ctx->end_xact = false;
+
+	/* do the actual work: call callback */
+	ctx->callbacks.startup_cb(ctx, opt, is_init);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
+static void
+shutdown_cb_wrapper(LogicalDecodingContext *ctx)
+{
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "shutdown";
+	state.report_location = InvalidXLogRecPtr;
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = false;
+	ctx->end_xact = false;
+
+	/* do the actual work: call callback */
+	ctx->callbacks.shutdown_cb(ctx);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
+
+/*
+ * Callbacks for ReorderBuffer which add in some more information and then call
+ * output_plugin.h plugins.
+ */
+static void
+begin_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn)
+{
+	LogicalDecodingContext *ctx = cache->private_data;
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "begin";
+	state.report_location = txn->first_lsn;
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = true;
+	ctx->write_xid = txn->xid;
+	ctx->write_location = txn->first_lsn;
+	ctx->end_xact = false;
+
+	/* do the actual work: call callback */
+	ctx->callbacks.begin_cb(ctx, txn);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
+static void
+commit_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+				  XLogRecPtr commit_lsn)
+{
+	LogicalDecodingContext *ctx = cache->private_data;
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "commit";
+	state.report_location = txn->final_lsn; /* beginning of commit record */
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = true;
+	ctx->write_xid = txn->xid;
+	ctx->write_location = txn->end_lsn; /* points to the end of the record */
+	ctx->end_xact = true;
+
+	/* do the actual work: call callback */
+	ctx->callbacks.commit_cb(ctx, txn, commit_lsn);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
+/*
+ * The functionality of begin_prepare is quite similar to begin with the
+ * exception that this will have gid (global transaction id) information which
+ * can be used by plugin. Now, we thought about extending the existing begin
+ * but that would break the replication protocol and additionally this looks
+ * cleaner.
+ */
+static void
+begin_prepare_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn)
+{
+	LogicalDecodingContext *ctx = cache->private_data;
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	/* We're only supposed to call this when two-phase commits are supported */
+	Assert(ctx->twophase);
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "begin_prepare";
+	state.report_location = txn->first_lsn;
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = true;
+	ctx->write_xid = txn->xid;
+	ctx->write_location = txn->first_lsn;
+	ctx->end_xact = false;
+
+	/*
+	 * If the plugin supports two-phase commits then begin prepare callback is
+	 * mandatory
+	 */
+	if (ctx->callbacks.begin_prepare_cb == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("logical replication at prepare time requires a %s callback",
+						"begin_prepare_cb")));
+
+	/* do the actual work: call callback */
+	ctx->callbacks.begin_prepare_cb(ctx, txn);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
+static void
+prepare_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+				   XLogRecPtr prepare_lsn)
+{
+	LogicalDecodingContext *ctx = cache->private_data;
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	/* We're only supposed to call this when two-phase commits are supported */
+	Assert(ctx->twophase);
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "prepare";
+	state.report_location = txn->final_lsn; /* beginning of prepare record */
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = true;
+	ctx->write_xid = txn->xid;
+	ctx->write_location = txn->end_lsn; /* points to the end of the record */
+	ctx->end_xact = true;
+
+	/*
+	 * If the plugin supports two-phase commits then prepare callback is
+	 * mandatory
+	 */
+	if (ctx->callbacks.prepare_cb == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("logical replication at prepare time requires a %s callback",
+						"prepare_cb")));
+
+	/* do the actual work: call callback */
+	ctx->callbacks.prepare_cb(ctx, txn, prepare_lsn);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
+static void
+commit_prepared_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+						   XLogRecPtr commit_lsn)
+{
+	LogicalDecodingContext *ctx = cache->private_data;
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	/* We're only supposed to call this when two-phase commits are supported */
+	Assert(ctx->twophase);
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "commit_prepared";
+	state.report_location = txn->final_lsn; /* beginning of commit record */
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = true;
+	ctx->write_xid = txn->xid;
+	ctx->write_location = txn->end_lsn; /* points to the end of the record */
+	ctx->end_xact = true;
+
+	/*
+	 * If the plugin support two-phase commits then commit prepared callback
+	 * is mandatory
+	 */
+	if (ctx->callbacks.commit_prepared_cb == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("logical replication at prepare time requires a %s callback",
+						"commit_prepared_cb")));
+
+	/* do the actual work: call callback */
+	ctx->callbacks.commit_prepared_cb(ctx, txn, commit_lsn);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
+static void
+rollback_prepared_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+							 XLogRecPtr prepare_end_lsn,
+							 TimestampTz prepare_time)
+{
+	LogicalDecodingContext *ctx = cache->private_data;
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	/* We're only supposed to call this when two-phase commits are supported */
+	Assert(ctx->twophase);
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "rollback_prepared";
+	state.report_location = txn->final_lsn; /* beginning of commit record */
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = true;
+	ctx->write_xid = txn->xid;
+	ctx->write_location = txn->end_lsn; /* points to the end of the record */
+	ctx->end_xact = true;
+
+	/*
+	 * If the plugin support two-phase commits then rollback prepared callback
+	 * is mandatory
+	 */
+	if (ctx->callbacks.rollback_prepared_cb == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("logical replication at prepare time requires a %s callback",
+						"rollback_prepared_cb")));
+
+	/* do the actual work: call callback */
+	ctx->callbacks.rollback_prepared_cb(ctx, txn, prepare_end_lsn,
+										prepare_time);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
+static void
+change_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+				  Relation relation, ReorderBufferChange *change)
+{
+	LogicalDecodingContext *ctx = cache->private_data;
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "change";
+	state.report_location = change->lsn;
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = true;
+	ctx->write_xid = txn->xid;
+
+	/*
+	 * report this change's lsn so replies from clients can give an up2date
+	 * answer. This won't ever be enough (and shouldn't be!) to confirm
+	 * receipt of this transaction, but it might allow another transaction's
+	 * commit to be confirmed with one message.
+	 */
+	ctx->write_location = change->lsn;
+
+	ctx->end_xact = false;
+
+	ctx->callbacks.change_cb(ctx, txn, relation, change);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
+static void
+truncate_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+					int nrelations, Relation relations[], ReorderBufferChange *change)
+{
+	LogicalDecodingContext *ctx = cache->private_data;
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	if (!ctx->callbacks.truncate_cb)
+		return;
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "truncate";
+	state.report_location = change->lsn;
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = true;
+	ctx->write_xid = txn->xid;
+
+	/*
+	 * report this change's lsn so replies from clients can give an up2date
+	 * answer. This won't ever be enough (and shouldn't be!) to confirm
+	 * receipt of this transaction, but it might allow another transaction's
+	 * commit to be confirmed with one message.
+	 */
+	ctx->write_location = change->lsn;
+
+	ctx->end_xact = false;
+
+	ctx->callbacks.truncate_cb(ctx, txn, nrelations, relations, change);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
+bool
+filter_prepare_cb_wrapper(LogicalDecodingContext *ctx, TransactionId xid,
+						  const char *gid)
+{
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+	bool		ret;
+
+	Assert(!ctx->fast_forward);
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "filter_prepare";
+	state.report_location = InvalidXLogRecPtr;
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = false;
+	ctx->end_xact = false;
+
+	/* do the actual work: call callback */
+	ret = ctx->callbacks.filter_prepare_cb(ctx, xid, gid);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+
+	return ret;
+}
+
+bool
+filter_by_origin_cb_wrapper(LogicalDecodingContext *ctx, RepOriginId origin_id)
+{
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+	bool		ret;
+
+	Assert(!ctx->fast_forward);
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "filter_by_origin";
+	state.report_location = InvalidXLogRecPtr;
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = false;
+	ctx->end_xact = false;
+
+	/* do the actual work: call callback */
+	ret = ctx->callbacks.filter_by_origin_cb(ctx, origin_id);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+
+	return ret;
+}
+
+static void
+message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+				   XLogRecPtr message_lsn, bool transactional,
+				   const char *prefix, Size message_size, const char *message)
+{
+	LogicalDecodingContext *ctx = cache->private_data;
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	if (ctx->callbacks.message_cb == NULL)
+		return;
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "message";
+	state.report_location = message_lsn;
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = true;
+	ctx->write_xid = txn != NULL ? txn->xid : InvalidTransactionId;
+	ctx->write_location = message_lsn;
+	ctx->end_xact = false;
+
+	/* do the actual work: call callback */
+	ctx->callbacks.message_cb(ctx, txn, message_lsn, transactional, prefix,
+							  message_size, message);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
+static void
+stream_start_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+						XLogRecPtr first_lsn)
+{
+	LogicalDecodingContext *ctx = cache->private_data;
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	/* We're only supposed to call this when streaming is supported. */
+	Assert(ctx->streaming);
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "stream_start";
+	state.report_location = first_lsn;
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = true;
+	ctx->write_xid = txn->xid;
+
+	/*
+	 * report this message's lsn so replies from clients can give an up2date
+	 * answer. This won't ever be enough (and shouldn't be!) to confirm
+	 * receipt of this transaction, but it might allow another transaction's
+	 * commit to be confirmed with one message.
+	 */
+	ctx->write_location = first_lsn;
+
+	ctx->end_xact = false;
+
+	/* in streaming mode, stream_start_cb is required */
+	if (ctx->callbacks.stream_start_cb == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("logical streaming requires a %s callback",
+						"stream_start_cb")));
+
+	ctx->callbacks.stream_start_cb(ctx, txn);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
+static void
+stream_stop_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+					   XLogRecPtr last_lsn)
+{
+	LogicalDecodingContext *ctx = cache->private_data;
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	/* We're only supposed to call this when streaming is supported. */
+	Assert(ctx->streaming);
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "stream_stop";
+	state.report_location = last_lsn;
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = true;
+	ctx->write_xid = txn->xid;
+
+	/*
+	 * report this message's lsn so replies from clients can give an up2date
+	 * answer. This won't ever be enough (and shouldn't be!) to confirm
+	 * receipt of this transaction, but it might allow another transaction's
+	 * commit to be confirmed with one message.
+	 */
+	ctx->write_location = last_lsn;
+
+	ctx->end_xact = false;
+
+	/* in streaming mode, stream_stop_cb is required */
+	if (ctx->callbacks.stream_stop_cb == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("logical streaming requires a %s callback",
+						"stream_stop_cb")));
+
+	ctx->callbacks.stream_stop_cb(ctx, txn);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
+static void
+stream_abort_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+						XLogRecPtr abort_lsn)
+{
+	LogicalDecodingContext *ctx = cache->private_data;
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	/* We're only supposed to call this when streaming is supported. */
+	Assert(ctx->streaming);
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "stream_abort";
+	state.report_location = abort_lsn;
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = true;
+	ctx->write_xid = txn->xid;
+	ctx->write_location = abort_lsn;
+	ctx->end_xact = true;
+
+	/* in streaming mode, stream_abort_cb is required */
+	if (ctx->callbacks.stream_abort_cb == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("logical streaming requires a %s callback",
+						"stream_abort_cb")));
+
+	ctx->callbacks.stream_abort_cb(ctx, txn, abort_lsn);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
+static void
+stream_prepare_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+						  XLogRecPtr prepare_lsn)
+{
+	LogicalDecodingContext *ctx = cache->private_data;
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	/*
+	 * We're only supposed to call this when streaming and two-phase commits
+	 * are supported.
+	 */
+	Assert(ctx->streaming);
+	Assert(ctx->twophase);
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "stream_prepare";
+	state.report_location = txn->final_lsn;
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = true;
+	ctx->write_xid = txn->xid;
+	ctx->write_location = txn->end_lsn;
+	ctx->end_xact = true;
+
+	/* in streaming mode with two-phase commits, stream_prepare_cb is required */
+	if (ctx->callbacks.stream_prepare_cb == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("logical streaming at prepare time requires a %s callback",
+						"stream_prepare_cb")));
+
+	ctx->callbacks.stream_prepare_cb(ctx, txn, prepare_lsn);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
+static void
+stream_commit_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+						 XLogRecPtr commit_lsn)
+{
+	LogicalDecodingContext *ctx = cache->private_data;
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	/* We're only supposed to call this when streaming is supported. */
+	Assert(ctx->streaming);
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "stream_commit";
+	state.report_location = txn->final_lsn;
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = true;
+	ctx->write_xid = txn->xid;
+	ctx->write_location = txn->end_lsn;
+	ctx->end_xact = true;
+
+	/* in streaming mode, stream_commit_cb is required */
+	if (ctx->callbacks.stream_commit_cb == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("logical streaming requires a %s callback",
+						"stream_commit_cb")));
+
+	ctx->callbacks.stream_commit_cb(ctx, txn, commit_lsn);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
+static void
+stream_change_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+						 Relation relation, ReorderBufferChange *change)
+{
+	LogicalDecodingContext *ctx = cache->private_data;
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	/* We're only supposed to call this when streaming is supported. */
+	Assert(ctx->streaming);
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "stream_change";
+	state.report_location = change->lsn;
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = true;
+	ctx->write_xid = txn->xid;
+
+	/*
+	 * report this change's lsn so replies from clients can give an up2date
+	 * answer. This won't ever be enough (and shouldn't be!) to confirm
+	 * receipt of this transaction, but it might allow another transaction's
+	 * commit to be confirmed with one message.
+	 */
+	ctx->write_location = change->lsn;
+
+	ctx->end_xact = false;
+
+	/* in streaming mode, stream_change_cb is required */
+	if (ctx->callbacks.stream_change_cb == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("logical streaming requires a %s callback",
+						"stream_change_cb")));
+
+	ctx->callbacks.stream_change_cb(ctx, txn, relation, change);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
+static void
+stream_message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+						  XLogRecPtr message_lsn, bool transactional,
+						  const char *prefix, Size message_size, const char *message)
+{
+	LogicalDecodingContext *ctx = cache->private_data;
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	/* We're only supposed to call this when streaming is supported. */
+	Assert(ctx->streaming);
+
+	/* this callback is optional */
+	if (ctx->callbacks.stream_message_cb == NULL)
+		return;
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "stream_message";
+	state.report_location = message_lsn;
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = true;
+	ctx->write_xid = txn != NULL ? txn->xid : InvalidTransactionId;
+	ctx->write_location = message_lsn;
+	ctx->end_xact = false;
+
+	/* do the actual work: call callback */
+	ctx->callbacks.stream_message_cb(ctx, txn, message_lsn, transactional, prefix,
+									 message_size, message);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
+static void
+stream_truncate_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+						   int nrelations, Relation relations[],
+						   ReorderBufferChange *change)
+{
+	LogicalDecodingContext *ctx = cache->private_data;
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	/* We're only supposed to call this when streaming is supported. */
+	Assert(ctx->streaming);
+
+	/* this callback is optional */
+	if (!ctx->callbacks.stream_truncate_cb)
+		return;
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "stream_truncate";
+	state.report_location = change->lsn;
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = true;
+	ctx->write_xid = txn->xid;
+
+	/*
+	 * report this change's lsn so replies from clients can give an up2date
+	 * answer. This won't ever be enough (and shouldn't be!) to confirm
+	 * receipt of this transaction, but it might allow another transaction's
+	 * commit to be confirmed with one message.
+	 */
+	ctx->write_location = change->lsn;
+
+	ctx->end_xact = false;
+
+	ctx->callbacks.stream_truncate_cb(ctx, txn, nrelations, relations, change);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
+/*
+ * Set the required catalog xmin horizon for historic snapshots in the current
+ * replication slot.
+ *
+ * Note that in the most cases, we won't be able to immediately use the xmin
+ * to increase the xmin horizon: we need to wait till the client has confirmed
+ * receiving current_lsn with LogicalConfirmReceivedLocation().
+ */
+void
+LogicalIncreaseXminForSlot(XLogRecPtr current_lsn, TransactionId xmin)
+{
+	bool		updated_xmin = false;
+	ReplicationSlot *slot;
+
+	slot = MyReplicationSlot;
+
+	Assert(slot != NULL);
+
+	SpinLockAcquire(&slot->mutex);
+
+	/*
+	 * don't overwrite if we already have a newer xmin. This can happen if we
+	 * restart decoding in a slot.
+	 */
+	if (TransactionIdPrecedesOrEquals(xmin, slot->data.catalog_xmin))
+	{
+	}
+
+	/*
+	 * If the client has already confirmed up to this lsn, we directly can
+	 * mark this as accepted. This can happen if we restart decoding in a
+	 * slot.
+	 */
+	else if (current_lsn <= slot->data.confirmed_flush)
+	{
+		slot->candidate_catalog_xmin = xmin;
+		slot->candidate_xmin_lsn = current_lsn;
+
+		/* our candidate can directly be used */
+		updated_xmin = true;
+	}
+
+	/*
+	 * Only increase if the previous values have been applied, otherwise we
+	 * might never end up updating if the receiver acks too slowly.
+	 */
+	else if (slot->candidate_xmin_lsn == InvalidXLogRecPtr)
+	{
+		slot->candidate_catalog_xmin = xmin;
+		slot->candidate_xmin_lsn = current_lsn;
+	}
+	SpinLockRelease(&slot->mutex);
+
+	/* candidate already valid with the current flush position, apply */
+	if (updated_xmin)
+		LogicalConfirmReceivedLocation(slot->data.confirmed_flush);
+}
+
+/*
+ * Mark the minimal LSN (restart_lsn) we need to read to replay all
+ * transactions that have not yet committed at current_lsn.
+ *
+ * Just like LogicalIncreaseXminForSlot this only takes effect when the
+ * client has confirmed to have received current_lsn.
+ */
+void
+LogicalIncreaseRestartDecodingForSlot(XLogRecPtr current_lsn, XLogRecPtr restart_lsn)
+{
+	bool		updated_lsn = false;
+	ReplicationSlot *slot;
+
+	slot = MyReplicationSlot;
+
+	Assert(slot != NULL);
+	Assert(restart_lsn != InvalidXLogRecPtr);
+	Assert(current_lsn != InvalidXLogRecPtr);
+
+	SpinLockAcquire(&slot->mutex);
+
+	/* don't overwrite if have a newer restart lsn */
+	if (restart_lsn <= slot->data.restart_lsn)
+	{
+	}
+
+	/*
+	 * We might have already flushed far enough to directly accept this lsn,
+	 * in this case there is no need to check for existing candidate LSNs
+	 */
+	else if (current_lsn <= slot->data.confirmed_flush)
+	{
+		slot->candidate_restart_valid = current_lsn;
+		slot->candidate_restart_lsn = restart_lsn;
+
+		/* our candidate can directly be used */
+		updated_lsn = true;
+	}
+
+	/*
+	 * Only increase if the previous values have been applied, otherwise we
+	 * might never end up updating if the receiver acks too slowly. A missed
+	 * value here will just cause some extra effort after reconnecting.
+	 */
+	if (slot->candidate_restart_valid == InvalidXLogRecPtr)
+	{
+		slot->candidate_restart_valid = current_lsn;
+		slot->candidate_restart_lsn = restart_lsn;
+		SpinLockRelease(&slot->mutex);
+
+		elog(DEBUG1, "got new restart lsn %X/%X at %X/%X",
+			 LSN_FORMAT_ARGS(restart_lsn),
+			 LSN_FORMAT_ARGS(current_lsn));
+	}
+	else
+	{
+		XLogRecPtr	candidate_restart_lsn;
+		XLogRecPtr	candidate_restart_valid;
+		XLogRecPtr	confirmed_flush;
+
+		candidate_restart_lsn = slot->candidate_restart_lsn;
+		candidate_restart_valid = slot->candidate_restart_valid;
+		confirmed_flush = slot->data.confirmed_flush;
+		SpinLockRelease(&slot->mutex);
+
+		elog(DEBUG1, "failed to increase restart lsn: proposed %X/%X, after %X/%X, current candidate %X/%X, current after %X/%X, flushed up to %X/%X",
+			 LSN_FORMAT_ARGS(restart_lsn),
+			 LSN_FORMAT_ARGS(current_lsn),
+			 LSN_FORMAT_ARGS(candidate_restart_lsn),
+			 LSN_FORMAT_ARGS(candidate_restart_valid),
+			 LSN_FORMAT_ARGS(confirmed_flush));
+	}
+
+	/* candidates are already valid with the current flush position, apply */
+	if (updated_lsn)
+		LogicalConfirmReceivedLocation(slot->data.confirmed_flush);
+}
+
+/*
+ * Handle a consumer's confirmation having received all changes up to lsn.
+ */
+void
+LogicalConfirmReceivedLocation(XLogRecPtr lsn)
+{
+	Assert(lsn != InvalidXLogRecPtr);
+
+	/* Do an unlocked check for candidate_lsn first. */
+	if (MyReplicationSlot->candidate_xmin_lsn != InvalidXLogRecPtr ||
+		MyReplicationSlot->candidate_restart_valid != InvalidXLogRecPtr)
+	{
+		bool		updated_xmin = false;
+		bool		updated_restart = false;
+
+		SpinLockAcquire(&MyReplicationSlot->mutex);
+
+		MyReplicationSlot->data.confirmed_flush = lsn;
+
+		/* if we're past the location required for bumping xmin, do so */
+		if (MyReplicationSlot->candidate_xmin_lsn != InvalidXLogRecPtr &&
+			MyReplicationSlot->candidate_xmin_lsn <= lsn)
+		{
+			/*
+			 * We have to write the changed xmin to disk *before* we change
+			 * the in-memory value, otherwise after a crash we wouldn't know
+			 * that some catalog tuples might have been removed already.
+			 *
+			 * Ensure that by first writing to ->xmin and only update
+			 * ->effective_xmin once the new state is synced to disk. After a
+			 * crash ->effective_xmin is set to ->xmin.
+			 */
+			if (TransactionIdIsValid(MyReplicationSlot->candidate_catalog_xmin) &&
+				MyReplicationSlot->data.catalog_xmin != MyReplicationSlot->candidate_catalog_xmin)
+			{
+				MyReplicationSlot->data.catalog_xmin = MyReplicationSlot->candidate_catalog_xmin;
+				MyReplicationSlot->candidate_catalog_xmin = InvalidTransactionId;
+				MyReplicationSlot->candidate_xmin_lsn = InvalidXLogRecPtr;
+				updated_xmin = true;
+			}
+		}
+
+		if (MyReplicationSlot->candidate_restart_valid != InvalidXLogRecPtr &&
+			MyReplicationSlot->candidate_restart_valid <= lsn)
+		{
+			Assert(MyReplicationSlot->candidate_restart_lsn != InvalidXLogRecPtr);
+
+			MyReplicationSlot->data.restart_lsn = MyReplicationSlot->candidate_restart_lsn;
+			MyReplicationSlot->candidate_restart_lsn = InvalidXLogRecPtr;
+			MyReplicationSlot->candidate_restart_valid = InvalidXLogRecPtr;
+			updated_restart = true;
+		}
+
+		SpinLockRelease(&MyReplicationSlot->mutex);
+
+		/* first write new xmin to disk, so we know what's up after a crash */
+		if (updated_xmin || updated_restart)
+		{
+			ReplicationSlotMarkDirty();
+			ReplicationSlotSave();
+			elog(DEBUG1, "updated xmin: %u restart: %u", updated_xmin, updated_restart);
+		}
+
+		/*
+		 * Now the new xmin is safely on disk, we can let the global value
+		 * advance. We do not take ProcArrayLock or similar since we only
+		 * advance xmin here and there's not much harm done by a concurrent
+		 * computation missing that.
+		 */
+		if (updated_xmin)
+		{
+			SpinLockAcquire(&MyReplicationSlot->mutex);
+			MyReplicationSlot->effective_catalog_xmin = MyReplicationSlot->data.catalog_xmin;
+			SpinLockRelease(&MyReplicationSlot->mutex);
+
+			ReplicationSlotsComputeRequiredXmin(false);
+			ReplicationSlotsComputeRequiredLSN();
+		}
+	}
+	else
+	{
+		SpinLockAcquire(&MyReplicationSlot->mutex);
+		MyReplicationSlot->data.confirmed_flush = lsn;
+		SpinLockRelease(&MyReplicationSlot->mutex);
+	}
+}
+
+/*
+ * Clear logical streaming state during (sub)transaction abort.
+ */
+void
+ResetLogicalStreamingState(void)
+{
+	CheckXidAlive = InvalidTransactionId;
+	bsysscan = false;
+}
+
+/*
+ * Report stats for a slot.
+ */
+void
+UpdateDecodingStats(LogicalDecodingContext *ctx)
+{
+	ReorderBuffer *rb = ctx->reorder;
+	PgStat_StatReplSlotEntry repSlotStat;
+
+	/* Nothing to do if we don't have any replication stats to be sent. */
+	if (rb->spillBytes <= 0 && rb->streamBytes <= 0 && rb->totalBytes <= 0)
+		return;
+
+	elog(DEBUG2, "UpdateDecodingStats: updating stats %p %lld %lld %lld %lld %lld %lld %lld %lld",
+		 rb,
+		 (long long) rb->spillTxns,
+		 (long long) rb->spillCount,
+		 (long long) rb->spillBytes,
+		 (long long) rb->streamTxns,
+		 (long long) rb->streamCount,
+		 (long long) rb->streamBytes,
+		 (long long) rb->totalTxns,
+		 (long long) rb->totalBytes);
+
+	namestrcpy(&repSlotStat.slotname, NameStr(ctx->slot->data.name));
+	repSlotStat.spill_txns = rb->spillTxns;
+	repSlotStat.spill_count = rb->spillCount;
+	repSlotStat.spill_bytes = rb->spillBytes;
+	repSlotStat.stream_txns = rb->streamTxns;
+	repSlotStat.stream_count = rb->streamCount;
+	repSlotStat.stream_bytes = rb->streamBytes;
+	repSlotStat.total_txns = rb->totalTxns;
+	repSlotStat.total_bytes = rb->totalBytes;
+
+	pgstat_report_replslot(&repSlotStat);
+
+	rb->spillTxns = 0;
+	rb->spillCount = 0;
+	rb->spillBytes = 0;
+	rb->streamTxns = 0;
+	rb->streamCount = 0;
+	rb->streamBytes = 0;
+	rb->totalTxns = 0;
+	rb->totalBytes = 0;
+}
diff --git a/src/backend/replication/logical/logicalfuncs.c b/src/backend/replication/logical/logicalfuncs.c
new file mode 100644
index 0000000..1f38c5b
--- /dev/null
+++ b/src/backend/replication/logical/logicalfuncs.c
@@ -0,0 +1,417 @@
+/*-------------------------------------------------------------------------
+ *
+ * logicalfuncs.c
+ *
+ *	   Support functions for using logical decoding and management of
+ *	   logical replication slots via SQL.
+ *
+ *
+ * Copyright (c) 2012-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logicalfuncs.c
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <unistd.h>
+
+#include "access/xact.h"
+#include "access/xlog_internal.h"
+#include "access/xlogutils.h"
+#include "catalog/pg_type.h"
+#include "fmgr.h"
+#include "funcapi.h"
+#include "mb/pg_wchar.h"
+#include "miscadmin.h"
+#include "nodes/makefuncs.h"
+#include "replication/decode.h"
+#include "replication/logical.h"
+#include "replication/message.h"
+#include "storage/fd.h"
+#include "utils/array.h"
+#include "utils/builtins.h"
+#include "utils/inval.h"
+#include "utils/lsyscache.h"
+#include "utils/memutils.h"
+#include "utils/pg_lsn.h"
+#include "utils/regproc.h"
+#include "utils/resowner.h"
+
+/* private date for writing out data */
+typedef struct DecodingOutputState
+{
+	Tuplestorestate *tupstore;
+	TupleDesc	tupdesc;
+	bool		binary_output;
+	int64		returned_rows;
+} DecodingOutputState;
+
+/*
+ * Prepare for an output plugin write.
+ */
+static void
+LogicalOutputPrepareWrite(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid,
+						  bool last_write)
+{
+	resetStringInfo(ctx->out);
+}
+
+/*
+ * Perform output plugin write into tuplestore.
+ */
+static void
+LogicalOutputWrite(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid,
+				   bool last_write)
+{
+	Datum		values[3];
+	bool		nulls[3];
+	DecodingOutputState *p;
+
+	/* SQL Datums can only be of a limited length... */
+	if (ctx->out->len > MaxAllocSize - VARHDRSZ)
+		elog(ERROR, "too much output for sql interface");
+
+	p = (DecodingOutputState *) ctx->output_writer_private;
+
+	memset(nulls, 0, sizeof(nulls));
+	values[0] = LSNGetDatum(lsn);
+	values[1] = TransactionIdGetDatum(xid);
+
+	/*
+	 * Assert ctx->out is in database encoding when we're writing textual
+	 * output.
+	 */
+	if (!p->binary_output)
+		Assert(pg_verify_mbstr(GetDatabaseEncoding(),
+							   ctx->out->data, ctx->out->len,
+							   false));
+
+	/* ick, but cstring_to_text_with_len works for bytea perfectly fine */
+	values[2] = PointerGetDatum(cstring_to_text_with_len(ctx->out->data, ctx->out->len));
+
+	tuplestore_putvalues(p->tupstore, p->tupdesc, values, nulls);
+	p->returned_rows++;
+}
+
+static void
+check_permissions(void)
+{
+	if (!superuser() && !has_rolreplication(GetUserId()))
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("must be superuser or replication role to use replication slots")));
+}
+
+/*
+ * Helper function for the various SQL callable logical decoding functions.
+ */
+static Datum
+pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool binary)
+{
+	Name		name;
+	XLogRecPtr	upto_lsn;
+	int32		upto_nchanges;
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+	MemoryContext per_query_ctx;
+	MemoryContext oldcontext;
+	XLogRecPtr	end_of_wal;
+	LogicalDecodingContext *ctx;
+	ResourceOwner old_resowner = CurrentResourceOwner;
+	ArrayType  *arr;
+	Size		ndim;
+	List	   *options = NIL;
+	DecodingOutputState *p;
+
+	check_permissions();
+
+	CheckLogicalDecodingRequirements();
+
+	if (PG_ARGISNULL(0))
+		ereport(ERROR,
+				(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+				 errmsg("slot name must not be null")));
+	name = PG_GETARG_NAME(0);
+
+	if (PG_ARGISNULL(1))
+		upto_lsn = InvalidXLogRecPtr;
+	else
+		upto_lsn = PG_GETARG_LSN(1);
+
+	if (PG_ARGISNULL(2))
+		upto_nchanges = InvalidXLogRecPtr;
+	else
+		upto_nchanges = PG_GETARG_INT32(2);
+
+	if (PG_ARGISNULL(3))
+		ereport(ERROR,
+				(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+				 errmsg("options array must not be null")));
+	arr = PG_GETARG_ARRAYTYPE_P(3);
+
+	/* check to see if caller supports us returning a tuplestore */
+	if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("set-valued function called in context that cannot accept a set")));
+	if (!(rsinfo->allowedModes & SFRM_Materialize))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("materialize mode required, but it is not allowed in this context")));
+
+	/* state to write output to */
+	p = palloc0(sizeof(DecodingOutputState));
+
+	p->binary_output = binary;
+
+	/* Build a tuple descriptor for our result type */
+	if (get_call_result_type(fcinfo, NULL, &p->tupdesc) != TYPEFUNC_COMPOSITE)
+		elog(ERROR, "return type must be a row type");
+
+	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
+	oldcontext = MemoryContextSwitchTo(per_query_ctx);
+
+	/* Deconstruct options array */
+	ndim = ARR_NDIM(arr);
+	if (ndim > 1)
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("array must be one-dimensional")));
+	}
+	else if (array_contains_nulls(arr))
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("array must not contain nulls")));
+	}
+	else if (ndim == 1)
+	{
+		int			nelems;
+		Datum	   *datum_opts;
+		int			i;
+
+		Assert(ARR_ELEMTYPE(arr) == TEXTOID);
+
+		deconstruct_array(arr, TEXTOID, -1, false, TYPALIGN_INT,
+						  &datum_opts, NULL, &nelems);
+
+		if (nelems % 2 != 0)
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("array must have even number of elements")));
+
+		for (i = 0; i < nelems; i += 2)
+		{
+			char	   *name = TextDatumGetCString(datum_opts[i]);
+			char	   *opt = TextDatumGetCString(datum_opts[i + 1]);
+
+			options = lappend(options, makeDefElem(name, (Node *) makeString(opt), -1));
+		}
+	}
+
+	p->tupstore = tuplestore_begin_heap(true, false, work_mem);
+	rsinfo->returnMode = SFRM_Materialize;
+	rsinfo->setResult = p->tupstore;
+	rsinfo->setDesc = p->tupdesc;
+
+	/*
+	 * Compute the current end-of-wal and maintain ThisTimeLineID.
+	 * RecoveryInProgress() will update ThisTimeLineID on promotion.
+	 */
+	if (!RecoveryInProgress())
+		end_of_wal = GetFlushRecPtr();
+	else
+		end_of_wal = GetXLogReplayRecPtr(&ThisTimeLineID);
+
+	ReplicationSlotAcquire(NameStr(*name), true);
+
+	PG_TRY();
+	{
+		/* restart at slot's confirmed_flush */
+		ctx = CreateDecodingContext(InvalidXLogRecPtr,
+									options,
+									false,
+									XL_ROUTINE(.page_read = read_local_xlog_page,
+											   .segment_open = wal_segment_open,
+											   .segment_close = wal_segment_close),
+									LogicalOutputPrepareWrite,
+									LogicalOutputWrite, NULL);
+
+		/*
+		 * After the sanity checks in CreateDecodingContext, make sure the
+		 * restart_lsn is valid.  Avoid "cannot get changes" wording in this
+		 * errmsg because that'd be confusingly ambiguous about no changes
+		 * being available.
+		 */
+		if (XLogRecPtrIsInvalid(MyReplicationSlot->data.restart_lsn))
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					 errmsg("can no longer get changes from replication slot \"%s\"",
+							NameStr(*name)),
+					 errdetail("This slot has never previously reserved WAL, or it has been invalidated.")));
+
+		MemoryContextSwitchTo(oldcontext);
+
+		/*
+		 * Check whether the output plugin writes textual output if that's
+		 * what we need.
+		 */
+		if (!binary &&
+			ctx->options.output_type !=OUTPUT_PLUGIN_TEXTUAL_OUTPUT)
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("logical decoding output plugin \"%s\" produces binary output, but function \"%s\" expects textual data",
+							NameStr(MyReplicationSlot->data.plugin),
+							format_procedure(fcinfo->flinfo->fn_oid))));
+
+		ctx->output_writer_private = p;
+
+		/*
+		 * Decoding of WAL must start at restart_lsn so that the entirety of
+		 * xacts that committed after the slot's confirmed_flush can be
+		 * accumulated into reorder buffers.
+		 */
+		XLogBeginRead(ctx->reader, MyReplicationSlot->data.restart_lsn);
+
+		/* invalidate non-timetravel entries */
+		InvalidateSystemCaches();
+
+		/* Decode until we run out of records */
+		while (ctx->reader->EndRecPtr < end_of_wal)
+		{
+			XLogRecord *record;
+			char	   *errm = NULL;
+
+			record = XLogReadRecord(ctx->reader, &errm);
+			if (errm)
+				elog(ERROR, "%s", errm);
+
+			/*
+			 * The {begin_txn,change,commit_txn}_wrapper callbacks above will
+			 * store the description into our tuplestore.
+			 */
+			if (record != NULL)
+				LogicalDecodingProcessRecord(ctx, ctx->reader);
+
+			/* check limits */
+			if (upto_lsn != InvalidXLogRecPtr &&
+				upto_lsn <= ctx->reader->EndRecPtr)
+				break;
+			if (upto_nchanges != 0 &&
+				upto_nchanges <= p->returned_rows)
+				break;
+			CHECK_FOR_INTERRUPTS();
+		}
+
+		tuplestore_donestoring(tupstore);
+
+		/*
+		 * Logical decoding could have clobbered CurrentResourceOwner during
+		 * transaction management, so restore the executor's value.  (This is
+		 * a kluge, but it's not worth cleaning up right now.)
+		 */
+		CurrentResourceOwner = old_resowner;
+
+		/*
+		 * Next time, start where we left off. (Hunting things, the family
+		 * business..)
+		 */
+		if (ctx->reader->EndRecPtr != InvalidXLogRecPtr && confirm)
+		{
+			LogicalConfirmReceivedLocation(ctx->reader->EndRecPtr);
+
+			/*
+			 * If only the confirmed_flush_lsn has changed the slot won't get
+			 * marked as dirty by the above. Callers on the walsender
+			 * interface are expected to keep track of their own progress and
+			 * don't need it written out. But SQL-interface users cannot
+			 * specify their own start positions and it's harder for them to
+			 * keep track of their progress, so we should make more of an
+			 * effort to save it for them.
+			 *
+			 * Dirty the slot so it's written out at the next checkpoint.
+			 * We'll still lose its position on crash, as documented, but it's
+			 * better than always losing the position even on clean restart.
+			 */
+			ReplicationSlotMarkDirty();
+		}
+
+		/* free context, call shutdown callback */
+		FreeDecodingContext(ctx);
+
+		ReplicationSlotRelease();
+		InvalidateSystemCaches();
+	}
+	PG_CATCH();
+	{
+		/* clear all timetravel entries */
+		InvalidateSystemCaches();
+
+		PG_RE_THROW();
+	}
+	PG_END_TRY();
+
+	return (Datum) 0;
+}
+
+/*
+ * SQL function returning the changestream as text, consuming the data.
+ */
+Datum
+pg_logical_slot_get_changes(PG_FUNCTION_ARGS)
+{
+	return pg_logical_slot_get_changes_guts(fcinfo, true, false);
+}
+
+/*
+ * SQL function returning the changestream as text, only peeking ahead.
+ */
+Datum
+pg_logical_slot_peek_changes(PG_FUNCTION_ARGS)
+{
+	return pg_logical_slot_get_changes_guts(fcinfo, false, false);
+}
+
+/*
+ * SQL function returning the changestream in binary, consuming the data.
+ */
+Datum
+pg_logical_slot_get_binary_changes(PG_FUNCTION_ARGS)
+{
+	return pg_logical_slot_get_changes_guts(fcinfo, true, true);
+}
+
+/*
+ * SQL function returning the changestream in binary, only peeking ahead.
+ */
+Datum
+pg_logical_slot_peek_binary_changes(PG_FUNCTION_ARGS)
+{
+	return pg_logical_slot_get_changes_guts(fcinfo, false, true);
+}
+
+
+/*
+ * SQL function for writing logical decoding message into WAL.
+ */
+Datum
+pg_logical_emit_message_bytea(PG_FUNCTION_ARGS)
+{
+	bool		transactional = PG_GETARG_BOOL(0);
+	char	   *prefix = text_to_cstring(PG_GETARG_TEXT_PP(1));
+	bytea	   *data = PG_GETARG_BYTEA_PP(2);
+	XLogRecPtr	lsn;
+
+	lsn = LogLogicalMessage(prefix, VARDATA_ANY(data), VARSIZE_ANY_EXHDR(data),
+							transactional);
+	PG_RETURN_LSN(lsn);
+}
+
+Datum
+pg_logical_emit_message_text(PG_FUNCTION_ARGS)
+{
+	/* bytea and text are compatible */
+	return pg_logical_emit_message_bytea(fcinfo);
+}
diff --git a/src/backend/replication/logical/message.c b/src/backend/replication/logical/message.c
new file mode 100644
index 0000000..93bd372
--- /dev/null
+++ b/src/backend/replication/logical/message.c
@@ -0,0 +1,88 @@
+/*-------------------------------------------------------------------------
+ *
+ * message.c
+ *	  Generic logical messages.
+ *
+ * Copyright (c) 2013-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/message.c
+ *
+ * NOTES
+ *
+ * Generic logical messages allow XLOG logging of arbitrary binary blobs that
+ * get passed to the logical decoding plugin. In normal XLOG processing they
+ * are same as NOOP.
+ *
+ * These messages can be either transactional or non-transactional.
+ * Transactional messages are part of current transaction and will be sent to
+ * decoding plugin using in a same way as DML operations.
+ * Non-transactional messages are sent to the plugin at the time when the
+ * logical decoding reads them from XLOG. This also means that transactional
+ * messages won't be delivered if the transaction was rolled back but the
+ * non-transactional one will always be delivered.
+ *
+ * Every message carries prefix to avoid conflicts between different decoding
+ * plugins. The plugin authors must take extra care to use unique prefix,
+ * good options seems to be for example to use the name of the extension.
+ *
+ * ---------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/xact.h"
+#include "miscadmin.h"
+#include "nodes/execnodes.h"
+#include "replication/logical.h"
+#include "replication/message.h"
+#include "utils/memutils.h"
+
+/*
+ * Write logical decoding message into XLog.
+ */
+XLogRecPtr
+LogLogicalMessage(const char *prefix, const char *message, size_t size,
+				  bool transactional)
+{
+	xl_logical_message xlrec;
+
+	/*
+	 * Force xid to be allocated if we're emitting a transactional message.
+	 */
+	if (transactional)
+	{
+		Assert(IsTransactionState());
+		GetCurrentTransactionId();
+	}
+
+	xlrec.dbId = MyDatabaseId;
+	xlrec.transactional = transactional;
+	/* trailing zero is critical; see logicalmsg_desc */
+	xlrec.prefix_size = strlen(prefix) + 1;
+	xlrec.message_size = size;
+
+	XLogBeginInsert();
+	XLogRegisterData((char *) &xlrec, SizeOfLogicalMessage);
+	XLogRegisterData(unconstify(char *, prefix), xlrec.prefix_size);
+	XLogRegisterData(unconstify(char *, message), size);
+
+	/* allow origin filtering */
+	XLogSetRecordFlags(XLOG_INCLUDE_ORIGIN);
+
+	return XLogInsert(RM_LOGICALMSG_ID, XLOG_LOGICAL_MESSAGE);
+}
+
+/*
+ * Redo is basically just noop for logical decoding messages.
+ */
+void
+logicalmsg_redo(XLogReaderState *record)
+{
+	uint8		info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;
+
+	if (info != XLOG_LOGICAL_MESSAGE)
+		elog(PANIC, "logicalmsg_redo: unknown op code %u", info);
+
+	/* This is only interesting for logical decoding, see decode.c. */
+}
diff --git a/src/backend/replication/logical/origin.c b/src/backend/replication/logical/origin.c
new file mode 100644
index 0000000..6988840
--- /dev/null
+++ b/src/backend/replication/logical/origin.c
@@ -0,0 +1,1574 @@
+/*-------------------------------------------------------------------------
+ *
+ * origin.c
+ *	  Logical replication progress tracking support.
+ *
+ * Copyright (c) 2013-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/origin.c
+ *
+ * NOTES
+ *
+ * This file provides the following:
+ * * An infrastructure to name nodes in a replication setup
+ * * A facility to efficiently store and persist replication progress in an
+ *	 efficient and durable manner.
+ *
+ * Replication origin consist out of a descriptive, user defined, external
+ * name and a short, thus space efficient, internal 2 byte one. This split
+ * exists because replication origin have to be stored in WAL and shared
+ * memory and long descriptors would be inefficient.  For now only use 2 bytes
+ * for the internal id of a replication origin as it seems unlikely that there
+ * soon will be more than 65k nodes in one replication setup; and using only
+ * two bytes allow us to be more space efficient.
+ *
+ * Replication progress is tracked in a shared memory table
+ * (ReplicationState) that's dumped to disk every checkpoint. Entries
+ * ('slots') in this table are identified by the internal id. That's the case
+ * because it allows to increase replication progress during crash
+ * recovery. To allow doing so we store the original LSN (from the originating
+ * system) of a transaction in the commit record. That allows to recover the
+ * precise replayed state after crash recovery; without requiring synchronous
+ * commits. Allowing logical replication to use asynchronous commit is
+ * generally good for performance, but especially important as it allows a
+ * single threaded replay process to keep up with a source that has multiple
+ * backends generating changes concurrently.  For efficiency and simplicity
+ * reasons a backend can setup one replication origin that's from then used as
+ * the source of changes produced by the backend, until reset again.
+ *
+ * This infrastructure is intended to be used in cooperation with logical
+ * decoding. When replaying from a remote system the configured origin is
+ * provided to output plugins, allowing prevention of replication loops and
+ * other filtering.
+ *
+ * There are several levels of locking at work:
+ *
+ * * To create and drop replication origins an exclusive lock on
+ *	 pg_replication_slot is required for the duration. That allows us to
+ *	 safely and conflict free assign new origins using a dirty snapshot.
+ *
+ * * When creating an in-memory replication progress slot the ReplicationOrigin
+ *	 LWLock has to be held exclusively; when iterating over the replication
+ *	 progress a shared lock has to be held, the same when advancing the
+ *	 replication progress of an individual backend that has not setup as the
+ *	 session's replication origin.
+ *
+ * * When manipulating or looking at the remote_lsn and local_lsn fields of a
+ *	 replication progress slot that slot's lwlock has to be held. That's
+ *	 primarily because we do not assume 8 byte writes (the LSN) is atomic on
+ *	 all our platforms, but it also simplifies memory ordering concerns
+ *	 between the remote and local lsn. We use a lwlock instead of a spinlock
+ *	 so it's less harmful to hold the lock over a WAL write
+ *	 (cf. AdvanceReplicationProgress).
+ *
+ * ---------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <unistd.h>
+#include <sys/stat.h>
+
+#include "access/genam.h"
+#include "access/htup_details.h"
+#include "access/table.h"
+#include "access/xact.h"
+#include "catalog/catalog.h"
+#include "catalog/indexing.h"
+#include "funcapi.h"
+#include "miscadmin.h"
+#include "nodes/execnodes.h"
+#include "pgstat.h"
+#include "replication/logical.h"
+#include "replication/origin.h"
+#include "storage/condition_variable.h"
+#include "storage/copydir.h"
+#include "storage/fd.h"
+#include "storage/ipc.h"
+#include "storage/lmgr.h"
+#include "utils/builtins.h"
+#include "utils/fmgroids.h"
+#include "utils/pg_lsn.h"
+#include "utils/rel.h"
+#include "utils/snapmgr.h"
+#include "utils/syscache.h"
+
+/*
+ * Replay progress of a single remote node.
+ */
+typedef struct ReplicationState
+{
+	/*
+	 * Local identifier for the remote node.
+	 */
+	RepOriginId roident;
+
+	/*
+	 * Location of the latest commit from the remote side.
+	 */
+	XLogRecPtr	remote_lsn;
+
+	/*
+	 * Remember the local lsn of the commit record so we can XLogFlush() to it
+	 * during a checkpoint so we know the commit record actually is safe on
+	 * disk.
+	 */
+	XLogRecPtr	local_lsn;
+
+	/*
+	 * PID of backend that's acquired slot, or 0 if none.
+	 */
+	int			acquired_by;
+
+	/*
+	 * Condition variable that's signaled when acquired_by changes.
+	 */
+	ConditionVariable origin_cv;
+
+	/*
+	 * Lock protecting remote_lsn and local_lsn.
+	 */
+	LWLock		lock;
+} ReplicationState;
+
+/*
+ * On disk version of ReplicationState.
+ */
+typedef struct ReplicationStateOnDisk
+{
+	RepOriginId roident;
+	XLogRecPtr	remote_lsn;
+} ReplicationStateOnDisk;
+
+
+typedef struct ReplicationStateCtl
+{
+	/* Tranche to use for per-origin LWLocks */
+	int			tranche_id;
+	/* Array of length max_replication_slots */
+	ReplicationState states[FLEXIBLE_ARRAY_MEMBER];
+} ReplicationStateCtl;
+
+/* external variables */
+RepOriginId replorigin_session_origin = InvalidRepOriginId; /* assumed identity */
+XLogRecPtr	replorigin_session_origin_lsn = InvalidXLogRecPtr;
+TimestampTz replorigin_session_origin_timestamp = 0;
+
+/*
+ * Base address into a shared memory array of replication states of size
+ * max_replication_slots.
+ *
+ * XXX: Should we use a separate variable to size this rather than
+ * max_replication_slots?
+ */
+static ReplicationState *replication_states;
+
+/*
+ * Actual shared memory block (replication_states[] is now part of this).
+ */
+static ReplicationStateCtl *replication_states_ctl;
+
+/*
+ * Backend-local, cached element from ReplicationState for use in a backend
+ * replaying remote commits, so we don't have to search ReplicationState for
+ * the backends current RepOriginId.
+ */
+static ReplicationState *session_replication_state = NULL;
+
+/* Magic for on disk files. */
+#define REPLICATION_STATE_MAGIC ((uint32) 0x1257DADE)
+
+static void
+replorigin_check_prerequisites(bool check_slots, bool recoveryOK)
+{
+	if (check_slots && max_replication_slots == 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("cannot query or manipulate replication origin when max_replication_slots = 0")));
+
+	if (!recoveryOK && RecoveryInProgress())
+		ereport(ERROR,
+				(errcode(ERRCODE_READ_ONLY_SQL_TRANSACTION),
+				 errmsg("cannot manipulate replication origins during recovery")));
+
+}
+
+
+/* ---------------------------------------------------------------------------
+ * Functions for working with replication origins themselves.
+ * ---------------------------------------------------------------------------
+ */
+
+/*
+ * Check for a persistent replication origin identified by name.
+ *
+ * Returns InvalidOid if the node isn't known yet and missing_ok is true.
+ */
+RepOriginId
+replorigin_by_name(const char *roname, bool missing_ok)
+{
+	Form_pg_replication_origin ident;
+	Oid			roident = InvalidOid;
+	HeapTuple	tuple;
+	Datum		roname_d;
+
+	roname_d = CStringGetTextDatum(roname);
+
+	tuple = SearchSysCache1(REPLORIGNAME, roname_d);
+	if (HeapTupleIsValid(tuple))
+	{
+		ident = (Form_pg_replication_origin) GETSTRUCT(tuple);
+		roident = ident->roident;
+		ReleaseSysCache(tuple);
+	}
+	else if (!missing_ok)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("replication origin \"%s\" does not exist",
+						roname)));
+
+	return roident;
+}
+
+/*
+ * Create a replication origin.
+ *
+ * Needs to be called in a transaction.
+ */
+RepOriginId
+replorigin_create(const char *roname)
+{
+	Oid			roident;
+	HeapTuple	tuple = NULL;
+	Relation	rel;
+	Datum		roname_d;
+	SnapshotData SnapshotDirty;
+	SysScanDesc scan;
+	ScanKeyData key;
+
+	roname_d = CStringGetTextDatum(roname);
+
+	Assert(IsTransactionState());
+
+	/*
+	 * We need the numeric replication origin to be 16bit wide, so we cannot
+	 * rely on the normal oid allocation. Instead we simply scan
+	 * pg_replication_origin for the first unused id. That's not particularly
+	 * efficient, but this should be a fairly infrequent operation - we can
+	 * easily spend a bit more code on this when it turns out it needs to be
+	 * faster.
+	 *
+	 * We handle concurrency by taking an exclusive lock (allowing reads!)
+	 * over the table for the duration of the search. Because we use a "dirty
+	 * snapshot" we can read rows that other in-progress sessions have
+	 * written, even though they would be invisible with normal snapshots. Due
+	 * to the exclusive lock there's no danger that new rows can appear while
+	 * we're checking.
+	 */
+	InitDirtySnapshot(SnapshotDirty);
+
+	rel = table_open(ReplicationOriginRelationId, ExclusiveLock);
+
+	for (roident = InvalidOid + 1; roident < PG_UINT16_MAX; roident++)
+	{
+		bool		nulls[Natts_pg_replication_origin];
+		Datum		values[Natts_pg_replication_origin];
+		bool		collides;
+
+		CHECK_FOR_INTERRUPTS();
+
+		ScanKeyInit(&key,
+					Anum_pg_replication_origin_roident,
+					BTEqualStrategyNumber, F_OIDEQ,
+					ObjectIdGetDatum(roident));
+
+		scan = systable_beginscan(rel, ReplicationOriginIdentIndex,
+								  true /* indexOK */ ,
+								  &SnapshotDirty,
+								  1, &key);
+
+		collides = HeapTupleIsValid(systable_getnext(scan));
+
+		systable_endscan(scan);
+
+		if (!collides)
+		{
+			/*
+			 * Ok, found an unused roident, insert the new row and do a CCI,
+			 * so our callers can look it up if they want to.
+			 */
+			memset(&nulls, 0, sizeof(nulls));
+
+			values[Anum_pg_replication_origin_roident - 1] = ObjectIdGetDatum(roident);
+			values[Anum_pg_replication_origin_roname - 1] = roname_d;
+
+			tuple = heap_form_tuple(RelationGetDescr(rel), values, nulls);
+			CatalogTupleInsert(rel, tuple);
+			CommandCounterIncrement();
+			break;
+		}
+	}
+
+	/* now release lock again,	*/
+	table_close(rel, ExclusiveLock);
+
+	if (tuple == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("could not find free replication origin OID")));
+
+	heap_freetuple(tuple);
+	return roident;
+}
+
+/*
+ * Helper function to drop a replication origin.
+ */
+static void
+replorigin_drop_guts(Relation rel, RepOriginId roident, bool nowait)
+{
+	HeapTuple	tuple;
+	int			i;
+
+	/*
+	 * First, clean up the slot state info, if there is any matching slot.
+	 */
+restart:
+	tuple = NULL;
+	LWLockAcquire(ReplicationOriginLock, LW_EXCLUSIVE);
+
+	for (i = 0; i < max_replication_slots; i++)
+	{
+		ReplicationState *state = &replication_states[i];
+
+		if (state->roident == roident)
+		{
+			/* found our slot, is it busy? */
+			if (state->acquired_by != 0)
+			{
+				ConditionVariable *cv;
+
+				if (nowait)
+					ereport(ERROR,
+							(errcode(ERRCODE_OBJECT_IN_USE),
+							 errmsg("could not drop replication origin with OID %d, in use by PID %d",
+									state->roident,
+									state->acquired_by)));
+
+				/*
+				 * We must wait and then retry.  Since we don't know which CV
+				 * to wait on until here, we can't readily use
+				 * ConditionVariablePrepareToSleep (calling it here would be
+				 * wrong, since we could miss the signal if we did so); just
+				 * use ConditionVariableSleep directly.
+				 */
+				cv = &state->origin_cv;
+
+				LWLockRelease(ReplicationOriginLock);
+
+				ConditionVariableSleep(cv, WAIT_EVENT_REPLICATION_ORIGIN_DROP);
+				goto restart;
+			}
+
+			/* first make a WAL log entry */
+			{
+				xl_replorigin_drop xlrec;
+
+				xlrec.node_id = roident;
+				XLogBeginInsert();
+				XLogRegisterData((char *) (&xlrec), sizeof(xlrec));
+				XLogInsert(RM_REPLORIGIN_ID, XLOG_REPLORIGIN_DROP);
+			}
+
+			/* then clear the in-memory slot */
+			state->roident = InvalidRepOriginId;
+			state->remote_lsn = InvalidXLogRecPtr;
+			state->local_lsn = InvalidXLogRecPtr;
+			break;
+		}
+	}
+	LWLockRelease(ReplicationOriginLock);
+	ConditionVariableCancelSleep();
+
+	/*
+	 * Now, we can delete the catalog entry.
+	 */
+	tuple = SearchSysCache1(REPLORIGIDENT, ObjectIdGetDatum(roident));
+	if (!HeapTupleIsValid(tuple))
+		elog(ERROR, "cache lookup failed for replication origin with oid %u",
+			 roident);
+
+	CatalogTupleDelete(rel, &tuple->t_self);
+	ReleaseSysCache(tuple);
+
+	CommandCounterIncrement();
+}
+
+/*
+ * Drop replication origin (by name).
+ *
+ * Needs to be called in a transaction.
+ */
+void
+replorigin_drop_by_name(const char *name, bool missing_ok, bool nowait)
+{
+	RepOriginId roident;
+	Relation	rel;
+
+	Assert(IsTransactionState());
+
+	/*
+	 * To interlock against concurrent drops, we hold ExclusiveLock on
+	 * pg_replication_origin till xact commit.
+	 *
+	 * XXX We can optimize this by acquiring the lock on a specific origin by
+	 * using LockSharedObject if required. However, for that, we first to
+	 * acquire a lock on ReplicationOriginRelationId, get the origin_id, lock
+	 * the specific origin and then re-check if the origin still exists.
+	 */
+	rel = table_open(ReplicationOriginRelationId, ExclusiveLock);
+
+	roident = replorigin_by_name(name, missing_ok);
+
+	if (OidIsValid(roident))
+		replorigin_drop_guts(rel, roident, nowait);
+
+	/* We keep the lock on pg_replication_origin until commit */
+	table_close(rel, NoLock);
+}
+
+/*
+ * Lookup replication origin via its oid and return the name.
+ *
+ * The external name is palloc'd in the calling context.
+ *
+ * Returns true if the origin is known, false otherwise.
+ */
+bool
+replorigin_by_oid(RepOriginId roident, bool missing_ok, char **roname)
+{
+	HeapTuple	tuple;
+	Form_pg_replication_origin ric;
+
+	Assert(OidIsValid((Oid) roident));
+	Assert(roident != InvalidRepOriginId);
+	Assert(roident != DoNotReplicateId);
+
+	tuple = SearchSysCache1(REPLORIGIDENT,
+							ObjectIdGetDatum((Oid) roident));
+
+	if (HeapTupleIsValid(tuple))
+	{
+		ric = (Form_pg_replication_origin) GETSTRUCT(tuple);
+		*roname = text_to_cstring(&ric->roname);
+		ReleaseSysCache(tuple);
+
+		return true;
+	}
+	else
+	{
+		*roname = NULL;
+
+		if (!missing_ok)
+			ereport(ERROR,
+					(errcode(ERRCODE_UNDEFINED_OBJECT),
+					 errmsg("replication origin with OID %u does not exist",
+							roident)));
+
+		return false;
+	}
+}
+
+
+/* ---------------------------------------------------------------------------
+ * Functions for handling replication progress.
+ * ---------------------------------------------------------------------------
+ */
+
+Size
+ReplicationOriginShmemSize(void)
+{
+	Size		size = 0;
+
+	/*
+	 * XXX: max_replication_slots is arguably the wrong thing to use, as here
+	 * we keep the replay state of *remote* transactions. But for now it seems
+	 * sufficient to reuse it, rather than introduce a separate GUC.
+	 */
+	if (max_replication_slots == 0)
+		return size;
+
+	size = add_size(size, offsetof(ReplicationStateCtl, states));
+
+	size = add_size(size,
+					mul_size(max_replication_slots, sizeof(ReplicationState)));
+	return size;
+}
+
+void
+ReplicationOriginShmemInit(void)
+{
+	bool		found;
+
+	if (max_replication_slots == 0)
+		return;
+
+	replication_states_ctl = (ReplicationStateCtl *)
+		ShmemInitStruct("ReplicationOriginState",
+						ReplicationOriginShmemSize(),
+						&found);
+	replication_states = replication_states_ctl->states;
+
+	if (!found)
+	{
+		int			i;
+
+		MemSet(replication_states_ctl, 0, ReplicationOriginShmemSize());
+
+		replication_states_ctl->tranche_id = LWTRANCHE_REPLICATION_ORIGIN_STATE;
+
+		for (i = 0; i < max_replication_slots; i++)
+		{
+			LWLockInitialize(&replication_states[i].lock,
+							 replication_states_ctl->tranche_id);
+			ConditionVariableInit(&replication_states[i].origin_cv);
+		}
+	}
+}
+
+/* ---------------------------------------------------------------------------
+ * Perform a checkpoint of each replication origin's progress with respect to
+ * the replayed remote_lsn. Make sure that all transactions we refer to in the
+ * checkpoint (local_lsn) are actually on-disk. This might not yet be the case
+ * if the transactions were originally committed asynchronously.
+ *
+ * We store checkpoints in the following format:
+ * +-------+------------------------+------------------+-----+--------+
+ * | MAGIC | ReplicationStateOnDisk | struct Replic... | ... | CRC32C | EOF
+ * +-------+------------------------+------------------+-----+--------+
+ *
+ * So its just the magic, followed by the statically sized
+ * ReplicationStateOnDisk structs. Note that the maximum number of
+ * ReplicationState is determined by max_replication_slots.
+ * ---------------------------------------------------------------------------
+ */
+void
+CheckPointReplicationOrigin(void)
+{
+	const char *tmppath = "pg_logical/replorigin_checkpoint.tmp";
+	const char *path = "pg_logical/replorigin_checkpoint";
+	int			tmpfd;
+	int			i;
+	uint32		magic = REPLICATION_STATE_MAGIC;
+	pg_crc32c	crc;
+
+	if (max_replication_slots == 0)
+		return;
+
+	INIT_CRC32C(crc);
+
+	/* make sure no old temp file is remaining */
+	if (unlink(tmppath) < 0 && errno != ENOENT)
+		ereport(PANIC,
+				(errcode_for_file_access(),
+				 errmsg("could not remove file \"%s\": %m",
+						tmppath)));
+
+	/*
+	 * no other backend can perform this at the same time; only one checkpoint
+	 * can happen at a time.
+	 */
+	tmpfd = OpenTransientFile(tmppath,
+							  O_CREAT | O_EXCL | O_WRONLY | PG_BINARY);
+	if (tmpfd < 0)
+		ereport(PANIC,
+				(errcode_for_file_access(),
+				 errmsg("could not create file \"%s\": %m",
+						tmppath)));
+
+	/* write magic */
+	errno = 0;
+	if ((write(tmpfd, &magic, sizeof(magic))) != sizeof(magic))
+	{
+		/* if write didn't set errno, assume problem is no disk space */
+		if (errno == 0)
+			errno = ENOSPC;
+		ereport(PANIC,
+				(errcode_for_file_access(),
+				 errmsg("could not write to file \"%s\": %m",
+						tmppath)));
+	}
+	COMP_CRC32C(crc, &magic, sizeof(magic));
+
+	/* prevent concurrent creations/drops */
+	LWLockAcquire(ReplicationOriginLock, LW_SHARED);
+
+	/* write actual data */
+	for (i = 0; i < max_replication_slots; i++)
+	{
+		ReplicationStateOnDisk disk_state;
+		ReplicationState *curstate = &replication_states[i];
+		XLogRecPtr	local_lsn;
+
+		if (curstate->roident == InvalidRepOriginId)
+			continue;
+
+		/* zero, to avoid uninitialized padding bytes */
+		memset(&disk_state, 0, sizeof(disk_state));
+
+		LWLockAcquire(&curstate->lock, LW_SHARED);
+
+		disk_state.roident = curstate->roident;
+
+		disk_state.remote_lsn = curstate->remote_lsn;
+		local_lsn = curstate->local_lsn;
+
+		LWLockRelease(&curstate->lock);
+
+		/* make sure we only write out a commit that's persistent */
+		XLogFlush(local_lsn);
+
+		errno = 0;
+		if ((write(tmpfd, &disk_state, sizeof(disk_state))) !=
+			sizeof(disk_state))
+		{
+			/* if write didn't set errno, assume problem is no disk space */
+			if (errno == 0)
+				errno = ENOSPC;
+			ereport(PANIC,
+					(errcode_for_file_access(),
+					 errmsg("could not write to file \"%s\": %m",
+							tmppath)));
+		}
+
+		COMP_CRC32C(crc, &disk_state, sizeof(disk_state));
+	}
+
+	LWLockRelease(ReplicationOriginLock);
+
+	/* write out the CRC */
+	FIN_CRC32C(crc);
+	errno = 0;
+	if ((write(tmpfd, &crc, sizeof(crc))) != sizeof(crc))
+	{
+		/* if write didn't set errno, assume problem is no disk space */
+		if (errno == 0)
+			errno = ENOSPC;
+		ereport(PANIC,
+				(errcode_for_file_access(),
+				 errmsg("could not write to file \"%s\": %m",
+						tmppath)));
+	}
+
+	if (CloseTransientFile(tmpfd) != 0)
+		ereport(PANIC,
+				(errcode_for_file_access(),
+				 errmsg("could not close file \"%s\": %m",
+						tmppath)));
+
+	/* fsync, rename to permanent file, fsync file and directory */
+	durable_rename(tmppath, path, PANIC);
+}
+
+/*
+ * Recover replication replay status from checkpoint data saved earlier by
+ * CheckPointReplicationOrigin.
+ *
+ * This only needs to be called at startup and *not* during every checkpoint
+ * read during recovery (e.g. in HS or PITR from a base backup) afterwards. All
+ * state thereafter can be recovered by looking at commit records.
+ */
+void
+StartupReplicationOrigin(void)
+{
+	const char *path = "pg_logical/replorigin_checkpoint";
+	int			fd;
+	int			readBytes;
+	uint32		magic = REPLICATION_STATE_MAGIC;
+	int			last_state = 0;
+	pg_crc32c	file_crc;
+	pg_crc32c	crc;
+
+	/* don't want to overwrite already existing state */
+#ifdef USE_ASSERT_CHECKING
+	static bool already_started = false;
+
+	Assert(!already_started);
+	already_started = true;
+#endif
+
+	if (max_replication_slots == 0)
+		return;
+
+	INIT_CRC32C(crc);
+
+	elog(DEBUG2, "starting up replication origin progress state");
+
+	fd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
+
+	/*
+	 * might have had max_replication_slots == 0 last run, or we just brought
+	 * up a standby.
+	 */
+	if (fd < 0 && errno == ENOENT)
+		return;
+	else if (fd < 0)
+		ereport(PANIC,
+				(errcode_for_file_access(),
+				 errmsg("could not open file \"%s\": %m",
+						path)));
+
+	/* verify magic, that is written even if nothing was active */
+	readBytes = read(fd, &magic, sizeof(magic));
+	if (readBytes != sizeof(magic))
+	{
+		if (readBytes < 0)
+			ereport(PANIC,
+					(errcode_for_file_access(),
+					 errmsg("could not read file \"%s\": %m",
+							path)));
+		else
+			ereport(PANIC,
+					(errcode(ERRCODE_DATA_CORRUPTED),
+					 errmsg("could not read file \"%s\": read %d of %zu",
+							path, readBytes, sizeof(magic))));
+	}
+	COMP_CRC32C(crc, &magic, sizeof(magic));
+
+	if (magic != REPLICATION_STATE_MAGIC)
+		ereport(PANIC,
+				(errmsg("replication checkpoint has wrong magic %u instead of %u",
+						magic, REPLICATION_STATE_MAGIC)));
+
+	/* we can skip locking here, no other access is possible */
+
+	/* recover individual states, until there are no more to be found */
+	while (true)
+	{
+		ReplicationStateOnDisk disk_state;
+
+		readBytes = read(fd, &disk_state, sizeof(disk_state));
+
+		/* no further data */
+		if (readBytes == sizeof(crc))
+		{
+			/* not pretty, but simple ... */
+			file_crc = *(pg_crc32c *) &disk_state;
+			break;
+		}
+
+		if (readBytes < 0)
+		{
+			ereport(PANIC,
+					(errcode_for_file_access(),
+					 errmsg("could not read file \"%s\": %m",
+							path)));
+		}
+
+		if (readBytes != sizeof(disk_state))
+		{
+			ereport(PANIC,
+					(errcode_for_file_access(),
+					 errmsg("could not read file \"%s\": read %d of %zu",
+							path, readBytes, sizeof(disk_state))));
+		}
+
+		COMP_CRC32C(crc, &disk_state, sizeof(disk_state));
+
+		if (last_state == max_replication_slots)
+			ereport(PANIC,
+					(errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
+					 errmsg("could not find free replication state, increase max_replication_slots")));
+
+		/* copy data to shared memory */
+		replication_states[last_state].roident = disk_state.roident;
+		replication_states[last_state].remote_lsn = disk_state.remote_lsn;
+		last_state++;
+
+		ereport(LOG,
+				(errmsg("recovered replication state of node %u to %X/%X",
+						disk_state.roident,
+						LSN_FORMAT_ARGS(disk_state.remote_lsn))));
+	}
+
+	/* now check checksum */
+	FIN_CRC32C(crc);
+	if (file_crc != crc)
+		ereport(PANIC,
+				(errcode(ERRCODE_DATA_CORRUPTED),
+				 errmsg("replication slot checkpoint has wrong checksum %u, expected %u",
+						crc, file_crc)));
+
+	if (CloseTransientFile(fd) != 0)
+		ereport(PANIC,
+				(errcode_for_file_access(),
+				 errmsg("could not close file \"%s\": %m",
+						path)));
+}
+
+void
+replorigin_redo(XLogReaderState *record)
+{
+	uint8		info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;
+
+	switch (info)
+	{
+		case XLOG_REPLORIGIN_SET:
+			{
+				xl_replorigin_set *xlrec =
+				(xl_replorigin_set *) XLogRecGetData(record);
+
+				replorigin_advance(xlrec->node_id,
+								   xlrec->remote_lsn, record->EndRecPtr,
+								   xlrec->force /* backward */ ,
+								   false /* WAL log */ );
+				break;
+			}
+		case XLOG_REPLORIGIN_DROP:
+			{
+				xl_replorigin_drop *xlrec;
+				int			i;
+
+				xlrec = (xl_replorigin_drop *) XLogRecGetData(record);
+
+				for (i = 0; i < max_replication_slots; i++)
+				{
+					ReplicationState *state = &replication_states[i];
+
+					/* found our slot */
+					if (state->roident == xlrec->node_id)
+					{
+						/* reset entry */
+						state->roident = InvalidRepOriginId;
+						state->remote_lsn = InvalidXLogRecPtr;
+						state->local_lsn = InvalidXLogRecPtr;
+						break;
+					}
+				}
+				break;
+			}
+		default:
+			elog(PANIC, "replorigin_redo: unknown op code %u", info);
+	}
+}
+
+
+/*
+ * Tell the replication origin progress machinery that a commit from 'node'
+ * that originated at the LSN remote_commit on the remote node was replayed
+ * successfully and that we don't need to do so again. In combination with
+ * setting up replorigin_session_origin_lsn and replorigin_session_origin
+ * that ensures we won't lose knowledge about that after a crash if the
+ * transaction had a persistent effect (think of asynchronous commits).
+ *
+ * local_commit needs to be a local LSN of the commit so that we can make sure
+ * upon a checkpoint that enough WAL has been persisted to disk.
+ *
+ * Needs to be called with a RowExclusiveLock on pg_replication_origin,
+ * unless running in recovery.
+ */
+void
+replorigin_advance(RepOriginId node,
+				   XLogRecPtr remote_commit, XLogRecPtr local_commit,
+				   bool go_backward, bool wal_log)
+{
+	int			i;
+	ReplicationState *replication_state = NULL;
+	ReplicationState *free_state = NULL;
+
+	Assert(node != InvalidRepOriginId);
+
+	/* we don't track DoNotReplicateId */
+	if (node == DoNotReplicateId)
+		return;
+
+	/*
+	 * XXX: For the case where this is called by WAL replay, it'd be more
+	 * efficient to restore into a backend local hashtable and only dump into
+	 * shmem after recovery is finished. Let's wait with implementing that
+	 * till it's shown to be a measurable expense
+	 */
+
+	/* Lock exclusively, as we may have to create a new table entry. */
+	LWLockAcquire(ReplicationOriginLock, LW_EXCLUSIVE);
+
+	/*
+	 * Search for either an existing slot for the origin, or a free one we can
+	 * use.
+	 */
+	for (i = 0; i < max_replication_slots; i++)
+	{
+		ReplicationState *curstate = &replication_states[i];
+
+		/* remember where to insert if necessary */
+		if (curstate->roident == InvalidRepOriginId &&
+			free_state == NULL)
+		{
+			free_state = curstate;
+			continue;
+		}
+
+		/* not our slot */
+		if (curstate->roident != node)
+		{
+			continue;
+		}
+
+		/* ok, found slot */
+		replication_state = curstate;
+
+		LWLockAcquire(&replication_state->lock, LW_EXCLUSIVE);
+
+		/* Make sure it's not used by somebody else */
+		if (replication_state->acquired_by != 0)
+		{
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_IN_USE),
+					 errmsg("replication origin with OID %d is already active for PID %d",
+							replication_state->roident,
+							replication_state->acquired_by)));
+		}
+
+		break;
+	}
+
+	if (replication_state == NULL && free_state == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
+				 errmsg("could not find free replication state slot for replication origin with OID %u",
+						node),
+				 errhint("Increase max_replication_slots and try again.")));
+
+	if (replication_state == NULL)
+	{
+		/* initialize new slot */
+		LWLockAcquire(&free_state->lock, LW_EXCLUSIVE);
+		replication_state = free_state;
+		Assert(replication_state->remote_lsn == InvalidXLogRecPtr);
+		Assert(replication_state->local_lsn == InvalidXLogRecPtr);
+		replication_state->roident = node;
+	}
+
+	Assert(replication_state->roident != InvalidRepOriginId);
+
+	/*
+	 * If somebody "forcefully" sets this slot, WAL log it, so it's durable
+	 * and the standby gets the message. Primarily this will be called during
+	 * WAL replay (of commit records) where no WAL logging is necessary.
+	 */
+	if (wal_log)
+	{
+		xl_replorigin_set xlrec;
+
+		xlrec.remote_lsn = remote_commit;
+		xlrec.node_id = node;
+		xlrec.force = go_backward;
+
+		XLogBeginInsert();
+		XLogRegisterData((char *) (&xlrec), sizeof(xlrec));
+
+		XLogInsert(RM_REPLORIGIN_ID, XLOG_REPLORIGIN_SET);
+	}
+
+	/*
+	 * Due to - harmless - race conditions during a checkpoint we could see
+	 * values here that are older than the ones we already have in memory.
+	 * Don't overwrite those.
+	 */
+	if (go_backward || replication_state->remote_lsn < remote_commit)
+		replication_state->remote_lsn = remote_commit;
+	if (local_commit != InvalidXLogRecPtr &&
+		(go_backward || replication_state->local_lsn < local_commit))
+		replication_state->local_lsn = local_commit;
+	LWLockRelease(&replication_state->lock);
+
+	/*
+	 * Release *after* changing the LSNs, slot isn't acquired and thus could
+	 * otherwise be dropped anytime.
+	 */
+	LWLockRelease(ReplicationOriginLock);
+}
+
+
+XLogRecPtr
+replorigin_get_progress(RepOriginId node, bool flush)
+{
+	int			i;
+	XLogRecPtr	local_lsn = InvalidXLogRecPtr;
+	XLogRecPtr	remote_lsn = InvalidXLogRecPtr;
+
+	/* prevent slots from being concurrently dropped */
+	LWLockAcquire(ReplicationOriginLock, LW_SHARED);
+
+	for (i = 0; i < max_replication_slots; i++)
+	{
+		ReplicationState *state;
+
+		state = &replication_states[i];
+
+		if (state->roident == node)
+		{
+			LWLockAcquire(&state->lock, LW_SHARED);
+
+			remote_lsn = state->remote_lsn;
+			local_lsn = state->local_lsn;
+
+			LWLockRelease(&state->lock);
+
+			break;
+		}
+	}
+
+	LWLockRelease(ReplicationOriginLock);
+
+	if (flush && local_lsn != InvalidXLogRecPtr)
+		XLogFlush(local_lsn);
+
+	return remote_lsn;
+}
+
+/*
+ * Tear down a (possibly) configured session replication origin during process
+ * exit.
+ */
+static void
+ReplicationOriginExitCleanup(int code, Datum arg)
+{
+	ConditionVariable *cv = NULL;
+
+	LWLockAcquire(ReplicationOriginLock, LW_EXCLUSIVE);
+
+	if (session_replication_state != NULL &&
+		session_replication_state->acquired_by == MyProcPid)
+	{
+		cv = &session_replication_state->origin_cv;
+
+		session_replication_state->acquired_by = 0;
+		session_replication_state = NULL;
+	}
+
+	LWLockRelease(ReplicationOriginLock);
+
+	if (cv)
+		ConditionVariableBroadcast(cv);
+}
+
+/*
+ * Setup a replication origin in the shared memory struct if it doesn't
+ * already exists and cache access to the specific ReplicationSlot so the
+ * array doesn't have to be searched when calling
+ * replorigin_session_advance().
+ *
+ * Obviously only one such cached origin can exist per process and the current
+ * cached value can only be set again after the previous value is torn down
+ * with replorigin_session_reset().
+ */
+void
+replorigin_session_setup(RepOriginId node)
+{
+	static bool registered_cleanup;
+	int			i;
+	int			free_slot = -1;
+
+	if (!registered_cleanup)
+	{
+		on_shmem_exit(ReplicationOriginExitCleanup, 0);
+		registered_cleanup = true;
+	}
+
+	Assert(max_replication_slots > 0);
+
+	if (session_replication_state != NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("cannot setup replication origin when one is already setup")));
+
+	/* Lock exclusively, as we may have to create a new table entry. */
+	LWLockAcquire(ReplicationOriginLock, LW_EXCLUSIVE);
+
+	/*
+	 * Search for either an existing slot for the origin, or a free one we can
+	 * use.
+	 */
+	for (i = 0; i < max_replication_slots; i++)
+	{
+		ReplicationState *curstate = &replication_states[i];
+
+		/* remember where to insert if necessary */
+		if (curstate->roident == InvalidRepOriginId &&
+			free_slot == -1)
+		{
+			free_slot = i;
+			continue;
+		}
+
+		/* not our slot */
+		if (curstate->roident != node)
+			continue;
+
+		else if (curstate->acquired_by != 0)
+		{
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_IN_USE),
+					 errmsg("replication origin with OID %d is already active for PID %d",
+							curstate->roident, curstate->acquired_by)));
+		}
+
+		/* ok, found slot */
+		session_replication_state = curstate;
+	}
+
+
+	if (session_replication_state == NULL && free_slot == -1)
+		ereport(ERROR,
+				(errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
+				 errmsg("could not find free replication state slot for replication origin with OID %u",
+						node),
+				 errhint("Increase max_replication_slots and try again.")));
+	else if (session_replication_state == NULL)
+	{
+		/* initialize new slot */
+		session_replication_state = &replication_states[free_slot];
+		Assert(session_replication_state->remote_lsn == InvalidXLogRecPtr);
+		Assert(session_replication_state->local_lsn == InvalidXLogRecPtr);
+		session_replication_state->roident = node;
+	}
+
+
+	Assert(session_replication_state->roident != InvalidRepOriginId);
+
+	session_replication_state->acquired_by = MyProcPid;
+
+	LWLockRelease(ReplicationOriginLock);
+
+	/* probably this one is pointless */
+	ConditionVariableBroadcast(&session_replication_state->origin_cv);
+}
+
+/*
+ * Reset replay state previously setup in this session.
+ *
+ * This function may only be called if an origin was setup with
+ * replorigin_session_setup().
+ */
+void
+replorigin_session_reset(void)
+{
+	ConditionVariable *cv;
+
+	Assert(max_replication_slots != 0);
+
+	if (session_replication_state == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("no replication origin is configured")));
+
+	LWLockAcquire(ReplicationOriginLock, LW_EXCLUSIVE);
+
+	session_replication_state->acquired_by = 0;
+	cv = &session_replication_state->origin_cv;
+	session_replication_state = NULL;
+
+	LWLockRelease(ReplicationOriginLock);
+
+	ConditionVariableBroadcast(cv);
+}
+
+/*
+ * Do the same work replorigin_advance() does, just on the session's
+ * configured origin.
+ *
+ * This is noticeably cheaper than using replorigin_advance().
+ */
+void
+replorigin_session_advance(XLogRecPtr remote_commit, XLogRecPtr local_commit)
+{
+	Assert(session_replication_state != NULL);
+	Assert(session_replication_state->roident != InvalidRepOriginId);
+
+	LWLockAcquire(&session_replication_state->lock, LW_EXCLUSIVE);
+	if (session_replication_state->local_lsn < local_commit)
+		session_replication_state->local_lsn = local_commit;
+	if (session_replication_state->remote_lsn < remote_commit)
+		session_replication_state->remote_lsn = remote_commit;
+	LWLockRelease(&session_replication_state->lock);
+}
+
+/*
+ * Ask the machinery about the point up to which we successfully replayed
+ * changes from an already setup replication origin.
+ */
+XLogRecPtr
+replorigin_session_get_progress(bool flush)
+{
+	XLogRecPtr	remote_lsn;
+	XLogRecPtr	local_lsn;
+
+	Assert(session_replication_state != NULL);
+
+	LWLockAcquire(&session_replication_state->lock, LW_SHARED);
+	remote_lsn = session_replication_state->remote_lsn;
+	local_lsn = session_replication_state->local_lsn;
+	LWLockRelease(&session_replication_state->lock);
+
+	if (flush && local_lsn != InvalidXLogRecPtr)
+		XLogFlush(local_lsn);
+
+	return remote_lsn;
+}
+
+
+
+/* ---------------------------------------------------------------------------
+ * SQL functions for working with replication origin.
+ *
+ * These mostly should be fairly short wrappers around more generic functions.
+ * ---------------------------------------------------------------------------
+ */
+
+/*
+ * Create replication origin for the passed in name, and return the assigned
+ * oid.
+ */
+Datum
+pg_replication_origin_create(PG_FUNCTION_ARGS)
+{
+	char	   *name;
+	RepOriginId roident;
+
+	replorigin_check_prerequisites(false, false);
+
+	name = text_to_cstring((text *) DatumGetPointer(PG_GETARG_DATUM(0)));
+
+	/* Replication origins "pg_xxx" are reserved for internal use */
+	if (IsReservedName(name))
+		ereport(ERROR,
+				(errcode(ERRCODE_RESERVED_NAME),
+				 errmsg("replication origin name \"%s\" is reserved",
+						name),
+				 errdetail("Origin names starting with \"pg_\" are reserved.")));
+
+	/*
+	 * If built with appropriate switch, whine when regression-testing
+	 * conventions for replication origin names are violated.
+	 */
+#ifdef ENFORCE_REGRESSION_TEST_NAME_RESTRICTIONS
+	if (strncmp(name, "regress_", 8) != 0)
+		elog(WARNING, "replication origins created by regression test cases should have names starting with \"regress_\"");
+#endif
+
+	roident = replorigin_create(name);
+
+	pfree(name);
+
+	PG_RETURN_OID(roident);
+}
+
+/*
+ * Drop replication origin.
+ */
+Datum
+pg_replication_origin_drop(PG_FUNCTION_ARGS)
+{
+	char	   *name;
+
+	replorigin_check_prerequisites(false, false);
+
+	name = text_to_cstring((text *) DatumGetPointer(PG_GETARG_DATUM(0)));
+
+	replorigin_drop_by_name(name, false, true);
+
+	pfree(name);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Return oid of a replication origin.
+ */
+Datum
+pg_replication_origin_oid(PG_FUNCTION_ARGS)
+{
+	char	   *name;
+	RepOriginId roident;
+
+	replorigin_check_prerequisites(false, false);
+
+	name = text_to_cstring((text *) DatumGetPointer(PG_GETARG_DATUM(0)));
+	roident = replorigin_by_name(name, true);
+
+	pfree(name);
+
+	if (OidIsValid(roident))
+		PG_RETURN_OID(roident);
+	PG_RETURN_NULL();
+}
+
+/*
+ * Setup a replication origin for this session.
+ */
+Datum
+pg_replication_origin_session_setup(PG_FUNCTION_ARGS)
+{
+	char	   *name;
+	RepOriginId origin;
+
+	replorigin_check_prerequisites(true, false);
+
+	name = text_to_cstring((text *) DatumGetPointer(PG_GETARG_DATUM(0)));
+	origin = replorigin_by_name(name, false);
+	replorigin_session_setup(origin);
+
+	replorigin_session_origin = origin;
+
+	pfree(name);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset previously setup origin in this session
+ */
+Datum
+pg_replication_origin_session_reset(PG_FUNCTION_ARGS)
+{
+	replorigin_check_prerequisites(true, false);
+
+	replorigin_session_reset();
+
+	replorigin_session_origin = InvalidRepOriginId;
+	replorigin_session_origin_lsn = InvalidXLogRecPtr;
+	replorigin_session_origin_timestamp = 0;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Has a replication origin been setup for this session.
+ */
+Datum
+pg_replication_origin_session_is_setup(PG_FUNCTION_ARGS)
+{
+	replorigin_check_prerequisites(false, false);
+
+	PG_RETURN_BOOL(replorigin_session_origin != InvalidRepOriginId);
+}
+
+
+/*
+ * Return the replication progress for origin setup in the current session.
+ *
+ * If 'flush' is set to true it is ensured that the returned value corresponds
+ * to a local transaction that has been flushed. This is useful if asynchronous
+ * commits are used when replaying replicated transactions.
+ */
+Datum
+pg_replication_origin_session_progress(PG_FUNCTION_ARGS)
+{
+	XLogRecPtr	remote_lsn = InvalidXLogRecPtr;
+	bool		flush = PG_GETARG_BOOL(0);
+
+	replorigin_check_prerequisites(true, false);
+
+	if (session_replication_state == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("no replication origin is configured")));
+
+	remote_lsn = replorigin_session_get_progress(flush);
+
+	if (remote_lsn == InvalidXLogRecPtr)
+		PG_RETURN_NULL();
+
+	PG_RETURN_LSN(remote_lsn);
+}
+
+Datum
+pg_replication_origin_xact_setup(PG_FUNCTION_ARGS)
+{
+	XLogRecPtr	location = PG_GETARG_LSN(0);
+
+	replorigin_check_prerequisites(true, false);
+
+	if (session_replication_state == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("no replication origin is configured")));
+
+	replorigin_session_origin_lsn = location;
+	replorigin_session_origin_timestamp = PG_GETARG_TIMESTAMPTZ(1);
+
+	PG_RETURN_VOID();
+}
+
+Datum
+pg_replication_origin_xact_reset(PG_FUNCTION_ARGS)
+{
+	replorigin_check_prerequisites(true, false);
+
+	replorigin_session_origin_lsn = InvalidXLogRecPtr;
+	replorigin_session_origin_timestamp = 0;
+
+	PG_RETURN_VOID();
+}
+
+
+Datum
+pg_replication_origin_advance(PG_FUNCTION_ARGS)
+{
+	text	   *name = PG_GETARG_TEXT_PP(0);
+	XLogRecPtr	remote_commit = PG_GETARG_LSN(1);
+	RepOriginId node;
+
+	replorigin_check_prerequisites(true, false);
+
+	/* lock to prevent the replication origin from vanishing */
+	LockRelationOid(ReplicationOriginRelationId, RowExclusiveLock);
+
+	node = replorigin_by_name(text_to_cstring(name), false);
+
+	/*
+	 * Can't sensibly pass a local commit to be flushed at checkpoint - this
+	 * xact hasn't committed yet. This is why this function should be used to
+	 * set up the initial replication state, but not for replay.
+	 */
+	replorigin_advance(node, remote_commit, InvalidXLogRecPtr,
+					   true /* go backward */ , true /* WAL log */ );
+
+	UnlockRelationOid(ReplicationOriginRelationId, RowExclusiveLock);
+
+	PG_RETURN_VOID();
+}
+
+
+/*
+ * Return the replication progress for an individual replication origin.
+ *
+ * If 'flush' is set to true it is ensured that the returned value corresponds
+ * to a local transaction that has been flushed. This is useful if asynchronous
+ * commits are used when replaying replicated transactions.
+ */
+Datum
+pg_replication_origin_progress(PG_FUNCTION_ARGS)
+{
+	char	   *name;
+	bool		flush;
+	RepOriginId roident;
+	XLogRecPtr	remote_lsn = InvalidXLogRecPtr;
+
+	replorigin_check_prerequisites(true, true);
+
+	name = text_to_cstring((text *) DatumGetPointer(PG_GETARG_DATUM(0)));
+	flush = PG_GETARG_BOOL(1);
+
+	roident = replorigin_by_name(name, false);
+	Assert(OidIsValid(roident));
+
+	remote_lsn = replorigin_get_progress(roident, flush);
+
+	if (remote_lsn == InvalidXLogRecPtr)
+		PG_RETURN_NULL();
+
+	PG_RETURN_LSN(remote_lsn);
+}
+
+
+Datum
+pg_show_replication_origin_status(PG_FUNCTION_ARGS)
+{
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+	TupleDesc	tupdesc;
+	Tuplestorestate *tupstore;
+	MemoryContext per_query_ctx;
+	MemoryContext oldcontext;
+	int			i;
+#define REPLICATION_ORIGIN_PROGRESS_COLS 4
+
+	/* we want to return 0 rows if slot is set to zero */
+	replorigin_check_prerequisites(false, true);
+
+	if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("set-valued function called in context that cannot accept a set")));
+	if (!(rsinfo->allowedModes & SFRM_Materialize))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("materialize mode required, but it is not allowed in this context")));
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+		elog(ERROR, "return type must be a row type");
+
+	if (tupdesc->natts != REPLICATION_ORIGIN_PROGRESS_COLS)
+		elog(ERROR, "wrong function definition");
+
+	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
+	oldcontext = MemoryContextSwitchTo(per_query_ctx);
+
+	tupstore = tuplestore_begin_heap(true, false, work_mem);
+	rsinfo->returnMode = SFRM_Materialize;
+	rsinfo->setResult = tupstore;
+	rsinfo->setDesc = tupdesc;
+
+	MemoryContextSwitchTo(oldcontext);
+
+
+	/* prevent slots from being concurrently dropped */
+	LWLockAcquire(ReplicationOriginLock, LW_SHARED);
+
+	/*
+	 * Iterate through all possible replication_states, display if they are
+	 * filled. Note that we do not take any locks, so slightly corrupted/out
+	 * of date values are a possibility.
+	 */
+	for (i = 0; i < max_replication_slots; i++)
+	{
+		ReplicationState *state;
+		Datum		values[REPLICATION_ORIGIN_PROGRESS_COLS];
+		bool		nulls[REPLICATION_ORIGIN_PROGRESS_COLS];
+		char	   *roname;
+
+		state = &replication_states[i];
+
+		/* unused slot, nothing to display */
+		if (state->roident == InvalidRepOriginId)
+			continue;
+
+		memset(values, 0, sizeof(values));
+		memset(nulls, 1, sizeof(nulls));
+
+		values[0] = ObjectIdGetDatum(state->roident);
+		nulls[0] = false;
+
+		/*
+		 * We're not preventing the origin to be dropped concurrently, so
+		 * silently accept that it might be gone.
+		 */
+		if (replorigin_by_oid(state->roident, true,
+							  &roname))
+		{
+			values[1] = CStringGetTextDatum(roname);
+			nulls[1] = false;
+		}
+
+		LWLockAcquire(&state->lock, LW_SHARED);
+
+		values[2] = LSNGetDatum(state->remote_lsn);
+		nulls[2] = false;
+
+		values[3] = LSNGetDatum(state->local_lsn);
+		nulls[3] = false;
+
+		LWLockRelease(&state->lock);
+
+		tuplestore_putvalues(tupstore, tupdesc, values, nulls);
+	}
+
+	tuplestore_donestoring(tupstore);
+
+	LWLockRelease(ReplicationOriginLock);
+
+#undef REPLICATION_ORIGIN_PROGRESS_COLS
+
+	return (Datum) 0;
+}
diff --git a/src/backend/replication/logical/proto.c b/src/backend/replication/logical/proto.c
new file mode 100644
index 0000000..1cf59e0
--- /dev/null
+++ b/src/backend/replication/logical/proto.c
@@ -0,0 +1,900 @@
+/*-------------------------------------------------------------------------
+ *
+ * proto.c
+ *		logical replication protocol functions
+ *
+ * Copyright (c) 2015-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *		src/backend/replication/logical/proto.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/sysattr.h"
+#include "catalog/pg_namespace.h"
+#include "catalog/pg_type.h"
+#include "libpq/pqformat.h"
+#include "replication/logicalproto.h"
+#include "utils/lsyscache.h"
+#include "utils/syscache.h"
+
+/*
+ * Protocol message flags.
+ */
+#define LOGICALREP_IS_REPLICA_IDENTITY 1
+
+#define MESSAGE_TRANSACTIONAL (1<<0)
+#define TRUNCATE_CASCADE		(1<<0)
+#define TRUNCATE_RESTART_SEQS	(1<<1)
+
+static void logicalrep_write_attrs(StringInfo out, Relation rel);
+static void logicalrep_write_tuple(StringInfo out, Relation rel,
+								   HeapTuple tuple, bool binary);
+
+static void logicalrep_read_attrs(StringInfo in, LogicalRepRelation *rel);
+static void logicalrep_read_tuple(StringInfo in, LogicalRepTupleData *tuple);
+
+static void logicalrep_write_namespace(StringInfo out, Oid nspid);
+static const char *logicalrep_read_namespace(StringInfo in);
+
+/*
+ * Write BEGIN to the output stream.
+ */
+void
+logicalrep_write_begin(StringInfo out, ReorderBufferTXN *txn)
+{
+	pq_sendbyte(out, LOGICAL_REP_MSG_BEGIN);
+
+	/* fixed fields */
+	pq_sendint64(out, txn->final_lsn);
+	pq_sendint64(out, txn->commit_time);
+	pq_sendint32(out, txn->xid);
+}
+
+/*
+ * Read transaction BEGIN from the stream.
+ */
+void
+logicalrep_read_begin(StringInfo in, LogicalRepBeginData *begin_data)
+{
+	/* read fields */
+	begin_data->final_lsn = pq_getmsgint64(in);
+	if (begin_data->final_lsn == InvalidXLogRecPtr)
+		elog(ERROR, "final_lsn not set in begin message");
+	begin_data->committime = pq_getmsgint64(in);
+	begin_data->xid = pq_getmsgint(in, 4);
+}
+
+
+/*
+ * Write COMMIT to the output stream.
+ */
+void
+logicalrep_write_commit(StringInfo out, ReorderBufferTXN *txn,
+						XLogRecPtr commit_lsn)
+{
+	uint8		flags = 0;
+
+	pq_sendbyte(out, LOGICAL_REP_MSG_COMMIT);
+
+	/* send the flags field (unused for now) */
+	pq_sendbyte(out, flags);
+
+	/* send fields */
+	pq_sendint64(out, commit_lsn);
+	pq_sendint64(out, txn->end_lsn);
+	pq_sendint64(out, txn->commit_time);
+}
+
+/*
+ * Read transaction COMMIT from the stream.
+ */
+void
+logicalrep_read_commit(StringInfo in, LogicalRepCommitData *commit_data)
+{
+	/* read flags (unused for now) */
+	uint8		flags = pq_getmsgbyte(in);
+
+	if (flags != 0)
+		elog(ERROR, "unrecognized flags %u in commit message", flags);
+
+	/* read fields */
+	commit_data->commit_lsn = pq_getmsgint64(in);
+	commit_data->end_lsn = pq_getmsgint64(in);
+	commit_data->committime = pq_getmsgint64(in);
+}
+
+/*
+ * Write ORIGIN to the output stream.
+ */
+void
+logicalrep_write_origin(StringInfo out, const char *origin,
+						XLogRecPtr origin_lsn)
+{
+	pq_sendbyte(out, LOGICAL_REP_MSG_ORIGIN);
+
+	/* fixed fields */
+	pq_sendint64(out, origin_lsn);
+
+	/* origin string */
+	pq_sendstring(out, origin);
+}
+
+/*
+ * Read ORIGIN from the output stream.
+ */
+char *
+logicalrep_read_origin(StringInfo in, XLogRecPtr *origin_lsn)
+{
+	/* fixed fields */
+	*origin_lsn = pq_getmsgint64(in);
+
+	/* return origin */
+	return pstrdup(pq_getmsgstring(in));
+}
+
+/*
+ * Write INSERT to the output stream.
+ */
+void
+logicalrep_write_insert(StringInfo out, TransactionId xid, Relation rel,
+						HeapTuple newtuple, bool binary)
+{
+	pq_sendbyte(out, LOGICAL_REP_MSG_INSERT);
+
+	/* transaction ID (if not valid, we're not streaming) */
+	if (TransactionIdIsValid(xid))
+		pq_sendint32(out, xid);
+
+	/* use Oid as relation identifier */
+	pq_sendint32(out, RelationGetRelid(rel));
+
+	pq_sendbyte(out, 'N');		/* new tuple follows */
+	logicalrep_write_tuple(out, rel, newtuple, binary);
+}
+
+/*
+ * Read INSERT from stream.
+ *
+ * Fills the new tuple.
+ */
+LogicalRepRelId
+logicalrep_read_insert(StringInfo in, LogicalRepTupleData *newtup)
+{
+	char		action;
+	LogicalRepRelId relid;
+
+	/* read the relation id */
+	relid = pq_getmsgint(in, 4);
+
+	action = pq_getmsgbyte(in);
+	if (action != 'N')
+		elog(ERROR, "expected new tuple but got %d",
+			 action);
+
+	logicalrep_read_tuple(in, newtup);
+
+	return relid;
+}
+
+/*
+ * Write UPDATE to the output stream.
+ */
+void
+logicalrep_write_update(StringInfo out, TransactionId xid, Relation rel,
+						HeapTuple oldtuple, HeapTuple newtuple, bool binary)
+{
+	pq_sendbyte(out, LOGICAL_REP_MSG_UPDATE);
+
+	Assert(rel->rd_rel->relreplident == REPLICA_IDENTITY_DEFAULT ||
+		   rel->rd_rel->relreplident == REPLICA_IDENTITY_FULL ||
+		   rel->rd_rel->relreplident == REPLICA_IDENTITY_INDEX);
+
+	/* transaction ID (if not valid, we're not streaming) */
+	if (TransactionIdIsValid(xid))
+		pq_sendint32(out, xid);
+
+	/* use Oid as relation identifier */
+	pq_sendint32(out, RelationGetRelid(rel));
+
+	if (oldtuple != NULL)
+	{
+		if (rel->rd_rel->relreplident == REPLICA_IDENTITY_FULL)
+			pq_sendbyte(out, 'O');	/* old tuple follows */
+		else
+			pq_sendbyte(out, 'K');	/* old key follows */
+		logicalrep_write_tuple(out, rel, oldtuple, binary);
+	}
+
+	pq_sendbyte(out, 'N');		/* new tuple follows */
+	logicalrep_write_tuple(out, rel, newtuple, binary);
+}
+
+/*
+ * Read UPDATE from stream.
+ */
+LogicalRepRelId
+logicalrep_read_update(StringInfo in, bool *has_oldtuple,
+					   LogicalRepTupleData *oldtup,
+					   LogicalRepTupleData *newtup)
+{
+	char		action;
+	LogicalRepRelId relid;
+
+	/* read the relation id */
+	relid = pq_getmsgint(in, 4);
+
+	/* read and verify action */
+	action = pq_getmsgbyte(in);
+	if (action != 'K' && action != 'O' && action != 'N')
+		elog(ERROR, "expected action 'N', 'O' or 'K', got %c",
+			 action);
+
+	/* check for old tuple */
+	if (action == 'K' || action == 'O')
+	{
+		logicalrep_read_tuple(in, oldtup);
+		*has_oldtuple = true;
+
+		action = pq_getmsgbyte(in);
+	}
+	else
+		*has_oldtuple = false;
+
+	/* check for new  tuple */
+	if (action != 'N')
+		elog(ERROR, "expected action 'N', got %c",
+			 action);
+
+	logicalrep_read_tuple(in, newtup);
+
+	return relid;
+}
+
+/*
+ * Write DELETE to the output stream.
+ */
+void
+logicalrep_write_delete(StringInfo out, TransactionId xid, Relation rel,
+						HeapTuple oldtuple, bool binary)
+{
+	Assert(rel->rd_rel->relreplident == REPLICA_IDENTITY_DEFAULT ||
+		   rel->rd_rel->relreplident == REPLICA_IDENTITY_FULL ||
+		   rel->rd_rel->relreplident == REPLICA_IDENTITY_INDEX);
+
+	pq_sendbyte(out, LOGICAL_REP_MSG_DELETE);
+
+	/* transaction ID (if not valid, we're not streaming) */
+	if (TransactionIdIsValid(xid))
+		pq_sendint32(out, xid);
+
+	/* use Oid as relation identifier */
+	pq_sendint32(out, RelationGetRelid(rel));
+
+	if (rel->rd_rel->relreplident == REPLICA_IDENTITY_FULL)
+		pq_sendbyte(out, 'O');	/* old tuple follows */
+	else
+		pq_sendbyte(out, 'K');	/* old key follows */
+
+	logicalrep_write_tuple(out, rel, oldtuple, binary);
+}
+
+/*
+ * Read DELETE from stream.
+ *
+ * Fills the old tuple.
+ */
+LogicalRepRelId
+logicalrep_read_delete(StringInfo in, LogicalRepTupleData *oldtup)
+{
+	char		action;
+	LogicalRepRelId relid;
+
+	/* read the relation id */
+	relid = pq_getmsgint(in, 4);
+
+	/* read and verify action */
+	action = pq_getmsgbyte(in);
+	if (action != 'K' && action != 'O')
+		elog(ERROR, "expected action 'O' or 'K', got %c", action);
+
+	logicalrep_read_tuple(in, oldtup);
+
+	return relid;
+}
+
+/*
+ * Write TRUNCATE to the output stream.
+ */
+void
+logicalrep_write_truncate(StringInfo out,
+						  TransactionId xid,
+						  int nrelids,
+						  Oid relids[],
+						  bool cascade, bool restart_seqs)
+{
+	int			i;
+	uint8		flags = 0;
+
+	pq_sendbyte(out, LOGICAL_REP_MSG_TRUNCATE);
+
+	/* transaction ID (if not valid, we're not streaming) */
+	if (TransactionIdIsValid(xid))
+		pq_sendint32(out, xid);
+
+	pq_sendint32(out, nrelids);
+
+	/* encode and send truncate flags */
+	if (cascade)
+		flags |= TRUNCATE_CASCADE;
+	if (restart_seqs)
+		flags |= TRUNCATE_RESTART_SEQS;
+	pq_sendint8(out, flags);
+
+	for (i = 0; i < nrelids; i++)
+		pq_sendint32(out, relids[i]);
+}
+
+/*
+ * Read TRUNCATE from stream.
+ */
+List *
+logicalrep_read_truncate(StringInfo in,
+						 bool *cascade, bool *restart_seqs)
+{
+	int			i;
+	int			nrelids;
+	List	   *relids = NIL;
+	uint8		flags;
+
+	nrelids = pq_getmsgint(in, 4);
+
+	/* read and decode truncate flags */
+	flags = pq_getmsgint(in, 1);
+	*cascade = (flags & TRUNCATE_CASCADE) > 0;
+	*restart_seqs = (flags & TRUNCATE_RESTART_SEQS) > 0;
+
+	for (i = 0; i < nrelids; i++)
+		relids = lappend_oid(relids, pq_getmsgint(in, 4));
+
+	return relids;
+}
+
+/*
+ * Write MESSAGE to stream
+ */
+void
+logicalrep_write_message(StringInfo out, TransactionId xid, XLogRecPtr lsn,
+						 bool transactional, const char *prefix, Size sz,
+						 const char *message)
+{
+	uint8		flags = 0;
+
+	pq_sendbyte(out, LOGICAL_REP_MSG_MESSAGE);
+
+	/* encode and send message flags */
+	if (transactional)
+		flags |= MESSAGE_TRANSACTIONAL;
+
+	/* transaction ID (if not valid, we're not streaming) */
+	if (TransactionIdIsValid(xid))
+		pq_sendint32(out, xid);
+
+	pq_sendint8(out, flags);
+	pq_sendint64(out, lsn);
+	pq_sendstring(out, prefix);
+	pq_sendint32(out, sz);
+	pq_sendbytes(out, message, sz);
+}
+
+/*
+ * Write relation description to the output stream.
+ */
+void
+logicalrep_write_rel(StringInfo out, TransactionId xid, Relation rel)
+{
+	char	   *relname;
+
+	pq_sendbyte(out, LOGICAL_REP_MSG_RELATION);
+
+	/* transaction ID (if not valid, we're not streaming) */
+	if (TransactionIdIsValid(xid))
+		pq_sendint32(out, xid);
+
+	/* use Oid as relation identifier */
+	pq_sendint32(out, RelationGetRelid(rel));
+
+	/* send qualified relation name */
+	logicalrep_write_namespace(out, RelationGetNamespace(rel));
+	relname = RelationGetRelationName(rel);
+	pq_sendstring(out, relname);
+
+	/* send replica identity */
+	pq_sendbyte(out, rel->rd_rel->relreplident);
+
+	/* send the attribute info */
+	logicalrep_write_attrs(out, rel);
+}
+
+/*
+ * Read the relation info from stream and return as LogicalRepRelation.
+ */
+LogicalRepRelation *
+logicalrep_read_rel(StringInfo in)
+{
+	LogicalRepRelation *rel = palloc(sizeof(LogicalRepRelation));
+
+	rel->remoteid = pq_getmsgint(in, 4);
+
+	/* Read relation name from stream */
+	rel->nspname = pstrdup(logicalrep_read_namespace(in));
+	rel->relname = pstrdup(pq_getmsgstring(in));
+
+	/* Read the replica identity. */
+	rel->replident = pq_getmsgbyte(in);
+
+	/* Get attribute description */
+	logicalrep_read_attrs(in, rel);
+
+	return rel;
+}
+
+/*
+ * Write type info to the output stream.
+ *
+ * This function will always write base type info.
+ */
+void
+logicalrep_write_typ(StringInfo out, TransactionId xid, Oid typoid)
+{
+	Oid			basetypoid = getBaseType(typoid);
+	HeapTuple	tup;
+	Form_pg_type typtup;
+
+	pq_sendbyte(out, LOGICAL_REP_MSG_TYPE);
+
+	/* transaction ID (if not valid, we're not streaming) */
+	if (TransactionIdIsValid(xid))
+		pq_sendint32(out, xid);
+
+	tup = SearchSysCache1(TYPEOID, ObjectIdGetDatum(basetypoid));
+	if (!HeapTupleIsValid(tup))
+		elog(ERROR, "cache lookup failed for type %u", basetypoid);
+	typtup = (Form_pg_type) GETSTRUCT(tup);
+
+	/* use Oid as relation identifier */
+	pq_sendint32(out, typoid);
+
+	/* send qualified type name */
+	logicalrep_write_namespace(out, typtup->typnamespace);
+	pq_sendstring(out, NameStr(typtup->typname));
+
+	ReleaseSysCache(tup);
+}
+
+/*
+ * Read type info from the output stream.
+ */
+void
+logicalrep_read_typ(StringInfo in, LogicalRepTyp *ltyp)
+{
+	ltyp->remoteid = pq_getmsgint(in, 4);
+
+	/* Read type name from stream */
+	ltyp->nspname = pstrdup(logicalrep_read_namespace(in));
+	ltyp->typname = pstrdup(pq_getmsgstring(in));
+}
+
+/*
+ * Write a tuple to the outputstream, in the most efficient format possible.
+ */
+static void
+logicalrep_write_tuple(StringInfo out, Relation rel, HeapTuple tuple, bool binary)
+{
+	TupleDesc	desc;
+	Datum		values[MaxTupleAttributeNumber];
+	bool		isnull[MaxTupleAttributeNumber];
+	int			i;
+	uint16		nliveatts = 0;
+
+	desc = RelationGetDescr(rel);
+
+	for (i = 0; i < desc->natts; i++)
+	{
+		if (TupleDescAttr(desc, i)->attisdropped || TupleDescAttr(desc, i)->attgenerated)
+			continue;
+		nliveatts++;
+	}
+	pq_sendint16(out, nliveatts);
+
+	/* try to allocate enough memory from the get-go */
+	enlargeStringInfo(out, tuple->t_len +
+					  nliveatts * (1 + 4));
+
+	heap_deform_tuple(tuple, desc, values, isnull);
+
+	/* Write the values */
+	for (i = 0; i < desc->natts; i++)
+	{
+		HeapTuple	typtup;
+		Form_pg_type typclass;
+		Form_pg_attribute att = TupleDescAttr(desc, i);
+
+		if (att->attisdropped || att->attgenerated)
+			continue;
+
+		if (isnull[i])
+		{
+			pq_sendbyte(out, LOGICALREP_COLUMN_NULL);
+			continue;
+		}
+
+		if (att->attlen == -1 && VARATT_IS_EXTERNAL_ONDISK(values[i]))
+		{
+			/*
+			 * Unchanged toasted datum.  (Note that we don't promise to detect
+			 * unchanged data in general; this is just a cheap check to avoid
+			 * sending large values unnecessarily.)
+			 */
+			pq_sendbyte(out, LOGICALREP_COLUMN_UNCHANGED);
+			continue;
+		}
+
+		typtup = SearchSysCache1(TYPEOID, ObjectIdGetDatum(att->atttypid));
+		if (!HeapTupleIsValid(typtup))
+			elog(ERROR, "cache lookup failed for type %u", att->atttypid);
+		typclass = (Form_pg_type) GETSTRUCT(typtup);
+
+		/*
+		 * Send in binary if requested and type has suitable send function.
+		 */
+		if (binary && OidIsValid(typclass->typsend))
+		{
+			bytea	   *outputbytes;
+			int			len;
+
+			pq_sendbyte(out, LOGICALREP_COLUMN_BINARY);
+			outputbytes = OidSendFunctionCall(typclass->typsend, values[i]);
+			len = VARSIZE(outputbytes) - VARHDRSZ;
+			pq_sendint(out, len, 4);	/* length */
+			pq_sendbytes(out, VARDATA(outputbytes), len);	/* data */
+			pfree(outputbytes);
+		}
+		else
+		{
+			char	   *outputstr;
+
+			pq_sendbyte(out, LOGICALREP_COLUMN_TEXT);
+			outputstr = OidOutputFunctionCall(typclass->typoutput, values[i]);
+			pq_sendcountedtext(out, outputstr, strlen(outputstr), false);
+			pfree(outputstr);
+		}
+
+		ReleaseSysCache(typtup);
+	}
+}
+
+/*
+ * Read tuple in logical replication format from stream.
+ */
+static void
+logicalrep_read_tuple(StringInfo in, LogicalRepTupleData *tuple)
+{
+	int			i;
+	int			natts;
+
+	/* Get number of attributes */
+	natts = pq_getmsgint(in, 2);
+
+	/* Allocate space for per-column values; zero out unused StringInfoDatas */
+	tuple->colvalues = (StringInfoData *) palloc0(natts * sizeof(StringInfoData));
+	tuple->colstatus = (char *) palloc(natts * sizeof(char));
+	tuple->ncols = natts;
+
+	/* Read the data */
+	for (i = 0; i < natts; i++)
+	{
+		char		kind;
+		int			len;
+		StringInfo	value = &tuple->colvalues[i];
+
+		kind = pq_getmsgbyte(in);
+		tuple->colstatus[i] = kind;
+
+		switch (kind)
+		{
+			case LOGICALREP_COLUMN_NULL:
+				/* nothing more to do */
+				break;
+			case LOGICALREP_COLUMN_UNCHANGED:
+				/* we don't receive the value of an unchanged column */
+				break;
+			case LOGICALREP_COLUMN_TEXT:
+				len = pq_getmsgint(in, 4);	/* read length */
+
+				/* and data */
+				value->data = palloc(len + 1);
+				pq_copymsgbytes(in, value->data, len);
+				value->data[len] = '\0';
+				/* make StringInfo fully valid */
+				value->len = len;
+				value->cursor = 0;
+				value->maxlen = len;
+				break;
+			case LOGICALREP_COLUMN_BINARY:
+				len = pq_getmsgint(in, 4);	/* read length */
+
+				/* and data */
+				value->data = palloc(len + 1);
+				pq_copymsgbytes(in, value->data, len);
+				/* not strictly necessary but per StringInfo practice */
+				value->data[len] = '\0';
+				/* make StringInfo fully valid */
+				value->len = len;
+				value->cursor = 0;
+				value->maxlen = len;
+				break;
+			default:
+				elog(ERROR, "unrecognized data representation type '%c'", kind);
+		}
+	}
+}
+
+/*
+ * Write relation attribute metadata to the stream.
+ */
+static void
+logicalrep_write_attrs(StringInfo out, Relation rel)
+{
+	TupleDesc	desc;
+	int			i;
+	uint16		nliveatts = 0;
+	Bitmapset  *idattrs = NULL;
+	bool		replidentfull;
+
+	desc = RelationGetDescr(rel);
+
+	/* send number of live attributes */
+	for (i = 0; i < desc->natts; i++)
+	{
+		if (TupleDescAttr(desc, i)->attisdropped || TupleDescAttr(desc, i)->attgenerated)
+			continue;
+		nliveatts++;
+	}
+	pq_sendint16(out, nliveatts);
+
+	/* fetch bitmap of REPLICATION IDENTITY attributes */
+	replidentfull = (rel->rd_rel->relreplident == REPLICA_IDENTITY_FULL);
+	if (!replidentfull)
+		idattrs = RelationGetIdentityKeyBitmap(rel);
+
+	/* send the attributes */
+	for (i = 0; i < desc->natts; i++)
+	{
+		Form_pg_attribute att = TupleDescAttr(desc, i);
+		uint8		flags = 0;
+
+		if (att->attisdropped || att->attgenerated)
+			continue;
+
+		/* REPLICA IDENTITY FULL means all columns are sent as part of key. */
+		if (replidentfull ||
+			bms_is_member(att->attnum - FirstLowInvalidHeapAttributeNumber,
+						  idattrs))
+			flags |= LOGICALREP_IS_REPLICA_IDENTITY;
+
+		pq_sendbyte(out, flags);
+
+		/* attribute name */
+		pq_sendstring(out, NameStr(att->attname));
+
+		/* attribute type id */
+		pq_sendint32(out, (int) att->atttypid);
+
+		/* attribute mode */
+		pq_sendint32(out, att->atttypmod);
+	}
+
+	bms_free(idattrs);
+}
+
+/*
+ * Read relation attribute metadata from the stream.
+ */
+static void
+logicalrep_read_attrs(StringInfo in, LogicalRepRelation *rel)
+{
+	int			i;
+	int			natts;
+	char	  **attnames;
+	Oid		   *atttyps;
+	Bitmapset  *attkeys = NULL;
+
+	natts = pq_getmsgint(in, 2);
+	attnames = palloc(natts * sizeof(char *));
+	atttyps = palloc(natts * sizeof(Oid));
+
+	/* read the attributes */
+	for (i = 0; i < natts; i++)
+	{
+		uint8		flags;
+
+		/* Check for replica identity column */
+		flags = pq_getmsgbyte(in);
+		if (flags & LOGICALREP_IS_REPLICA_IDENTITY)
+			attkeys = bms_add_member(attkeys, i);
+
+		/* attribute name */
+		attnames[i] = pstrdup(pq_getmsgstring(in));
+
+		/* attribute type id */
+		atttyps[i] = (Oid) pq_getmsgint(in, 4);
+
+		/* we ignore attribute mode for now */
+		(void) pq_getmsgint(in, 4);
+	}
+
+	rel->attnames = attnames;
+	rel->atttyps = atttyps;
+	rel->attkeys = attkeys;
+	rel->natts = natts;
+}
+
+/*
+ * Write the namespace name or empty string for pg_catalog (to save space).
+ */
+static void
+logicalrep_write_namespace(StringInfo out, Oid nspid)
+{
+	if (nspid == PG_CATALOG_NAMESPACE)
+		pq_sendbyte(out, '\0');
+	else
+	{
+		char	   *nspname = get_namespace_name(nspid);
+
+		if (nspname == NULL)
+			elog(ERROR, "cache lookup failed for namespace %u",
+				 nspid);
+
+		pq_sendstring(out, nspname);
+	}
+}
+
+/*
+ * Read the namespace name while treating empty string as pg_catalog.
+ */
+static const char *
+logicalrep_read_namespace(StringInfo in)
+{
+	const char *nspname = pq_getmsgstring(in);
+
+	if (nspname[0] == '\0')
+		nspname = "pg_catalog";
+
+	return nspname;
+}
+
+/*
+ * Write the information for the start stream message to the output stream.
+ */
+void
+logicalrep_write_stream_start(StringInfo out,
+							  TransactionId xid, bool first_segment)
+{
+	pq_sendbyte(out, LOGICAL_REP_MSG_STREAM_START);
+
+	Assert(TransactionIdIsValid(xid));
+
+	/* transaction ID (we're starting to stream, so must be valid) */
+	pq_sendint32(out, xid);
+
+	/* 1 if this is the first streaming segment for this xid */
+	pq_sendbyte(out, first_segment ? 1 : 0);
+}
+
+/*
+ * Read the information about the start stream message from output stream.
+ */
+TransactionId
+logicalrep_read_stream_start(StringInfo in, bool *first_segment)
+{
+	TransactionId xid;
+
+	Assert(first_segment);
+
+	xid = pq_getmsgint(in, 4);
+	*first_segment = (pq_getmsgbyte(in) == 1);
+
+	return xid;
+}
+
+/*
+ * Write the stop stream message to the output stream.
+ */
+void
+logicalrep_write_stream_stop(StringInfo out)
+{
+	pq_sendbyte(out, LOGICAL_REP_MSG_STREAM_END);
+}
+
+/*
+ * Write STREAM COMMIT to the output stream.
+ */
+void
+logicalrep_write_stream_commit(StringInfo out, ReorderBufferTXN *txn,
+							   XLogRecPtr commit_lsn)
+{
+	uint8		flags = 0;
+
+	pq_sendbyte(out, LOGICAL_REP_MSG_STREAM_COMMIT);
+
+	Assert(TransactionIdIsValid(txn->xid));
+
+	/* transaction ID */
+	pq_sendint32(out, txn->xid);
+
+	/* send the flags field (unused for now) */
+	pq_sendbyte(out, flags);
+
+	/* send fields */
+	pq_sendint64(out, commit_lsn);
+	pq_sendint64(out, txn->end_lsn);
+	pq_sendint64(out, txn->commit_time);
+}
+
+/*
+ * Read STREAM COMMIT from the output stream.
+ */
+TransactionId
+logicalrep_read_stream_commit(StringInfo in, LogicalRepCommitData *commit_data)
+{
+	TransactionId xid;
+	uint8		flags;
+
+	xid = pq_getmsgint(in, 4);
+
+	/* read flags (unused for now) */
+	flags = pq_getmsgbyte(in);
+
+	if (flags != 0)
+		elog(ERROR, "unrecognized flags %u in commit message", flags);
+
+	/* read fields */
+	commit_data->commit_lsn = pq_getmsgint64(in);
+	commit_data->end_lsn = pq_getmsgint64(in);
+	commit_data->committime = pq_getmsgint64(in);
+
+	return xid;
+}
+
+/*
+ * Write STREAM ABORT to the output stream. Note that xid and subxid will be
+ * same for the top-level transaction abort.
+ */
+void
+logicalrep_write_stream_abort(StringInfo out, TransactionId xid,
+							  TransactionId subxid)
+{
+	pq_sendbyte(out, LOGICAL_REP_MSG_STREAM_ABORT);
+
+	Assert(TransactionIdIsValid(xid) && TransactionIdIsValid(subxid));
+
+	/* transaction ID */
+	pq_sendint32(out, xid);
+	pq_sendint32(out, subxid);
+}
+
+/*
+ * Read STREAM ABORT from the output stream.
+ */
+void
+logicalrep_read_stream_abort(StringInfo in, TransactionId *xid,
+							 TransactionId *subxid)
+{
+	Assert(xid && subxid);
+
+	*xid = pq_getmsgint(in, 4);
+	*subxid = pq_getmsgint(in, 4);
+}
diff --git a/src/backend/replication/logical/relation.c b/src/backend/replication/logical/relation.c
new file mode 100644
index 0000000..a5e5bf9
--- /dev/null
+++ b/src/backend/replication/logical/relation.c
@@ -0,0 +1,705 @@
+/*-------------------------------------------------------------------------
+ * relation.c
+ *	   PostgreSQL logical replication relation mapping cache
+ *
+ * Copyright (c) 2016-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/relation.c
+ *
+ * NOTES
+ *	  Routines in this file mainly have to do with mapping the properties
+ *	  of local replication target relations to the properties of their
+ *	  remote counterpart.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/table.h"
+#include "catalog/namespace.h"
+#include "catalog/pg_subscription_rel.h"
+#include "executor/executor.h"
+#include "nodes/makefuncs.h"
+#include "replication/logicalrelation.h"
+#include "replication/worker_internal.h"
+#include "utils/inval.h"
+
+
+static MemoryContext LogicalRepRelMapContext = NULL;
+
+static HTAB *LogicalRepRelMap = NULL;
+
+/*
+ * Partition map (LogicalRepPartMap)
+ *
+ * When a partitioned table is used as replication target, replicated
+ * operations are actually performed on its leaf partitions, which requires
+ * the partitions to also be mapped to the remote relation.  Parent's entry
+ * (LogicalRepRelMapEntry) cannot be used as-is for all partitions, because
+ * individual partitions may have different attribute numbers, which means
+ * attribute mappings to remote relation's attributes must be maintained
+ * separately for each partition.
+ */
+static MemoryContext LogicalRepPartMapContext = NULL;
+static HTAB *LogicalRepPartMap = NULL;
+typedef struct LogicalRepPartMapEntry
+{
+	Oid			partoid;		/* LogicalRepPartMap's key */
+	LogicalRepRelMapEntry relmapentry;
+} LogicalRepPartMapEntry;
+
+/*
+ * Relcache invalidation callback for our relation map cache.
+ */
+static void
+logicalrep_relmap_invalidate_cb(Datum arg, Oid reloid)
+{
+	LogicalRepRelMapEntry *entry;
+
+	/* Just to be sure. */
+	if (LogicalRepRelMap == NULL)
+		return;
+
+	if (reloid != InvalidOid)
+	{
+		HASH_SEQ_STATUS status;
+
+		hash_seq_init(&status, LogicalRepRelMap);
+
+		/* TODO, use inverse lookup hashtable? */
+		while ((entry = (LogicalRepRelMapEntry *) hash_seq_search(&status)) != NULL)
+		{
+			if (entry->localreloid == reloid)
+			{
+				entry->localrelvalid = false;
+				hash_seq_term(&status);
+				break;
+			}
+		}
+	}
+	else
+	{
+		/* invalidate all cache entries */
+		HASH_SEQ_STATUS status;
+
+		hash_seq_init(&status, LogicalRepRelMap);
+
+		while ((entry = (LogicalRepRelMapEntry *) hash_seq_search(&status)) != NULL)
+			entry->localrelvalid = false;
+	}
+}
+
+/*
+ * Initialize the relation map cache.
+ */
+static void
+logicalrep_relmap_init(void)
+{
+	HASHCTL		ctl;
+
+	if (!LogicalRepRelMapContext)
+		LogicalRepRelMapContext =
+			AllocSetContextCreate(CacheMemoryContext,
+								  "LogicalRepRelMapContext",
+								  ALLOCSET_DEFAULT_SIZES);
+
+	/* Initialize the relation hash table. */
+	ctl.keysize = sizeof(LogicalRepRelId);
+	ctl.entrysize = sizeof(LogicalRepRelMapEntry);
+	ctl.hcxt = LogicalRepRelMapContext;
+
+	LogicalRepRelMap = hash_create("logicalrep relation map cache", 128, &ctl,
+								   HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
+
+	/* Watch for invalidation events. */
+	CacheRegisterRelcacheCallback(logicalrep_relmap_invalidate_cb,
+								  (Datum) 0);
+}
+
+/*
+ * Free the entry of a relation map cache.
+ */
+static void
+logicalrep_relmap_free_entry(LogicalRepRelMapEntry *entry)
+{
+	LogicalRepRelation *remoterel;
+
+	remoterel = &entry->remoterel;
+
+	pfree(remoterel->nspname);
+	pfree(remoterel->relname);
+
+	if (remoterel->natts > 0)
+	{
+		int			i;
+
+		for (i = 0; i < remoterel->natts; i++)
+			pfree(remoterel->attnames[i]);
+
+		pfree(remoterel->attnames);
+		pfree(remoterel->atttyps);
+	}
+	bms_free(remoterel->attkeys);
+
+	if (entry->attrmap)
+		free_attrmap(entry->attrmap);
+}
+
+/*
+ * Add new entry or update existing entry in the relation map cache.
+ *
+ * Called when new relation mapping is sent by the publisher to update
+ * our expected view of incoming data from said publisher.
+ */
+void
+logicalrep_relmap_update(LogicalRepRelation *remoterel)
+{
+	MemoryContext oldctx;
+	LogicalRepRelMapEntry *entry;
+	bool		found;
+	int			i;
+
+	if (LogicalRepRelMap == NULL)
+		logicalrep_relmap_init();
+
+	/*
+	 * HASH_ENTER returns the existing entry if present or creates a new one.
+	 */
+	entry = hash_search(LogicalRepRelMap, (void *) &remoterel->remoteid,
+						HASH_ENTER, &found);
+
+	if (found)
+		logicalrep_relmap_free_entry(entry);
+
+	memset(entry, 0, sizeof(LogicalRepRelMapEntry));
+
+	/* Make cached copy of the data */
+	oldctx = MemoryContextSwitchTo(LogicalRepRelMapContext);
+	entry->remoterel.remoteid = remoterel->remoteid;
+	entry->remoterel.nspname = pstrdup(remoterel->nspname);
+	entry->remoterel.relname = pstrdup(remoterel->relname);
+	entry->remoterel.natts = remoterel->natts;
+	entry->remoterel.attnames = palloc(remoterel->natts * sizeof(char *));
+	entry->remoterel.atttyps = palloc(remoterel->natts * sizeof(Oid));
+	for (i = 0; i < remoterel->natts; i++)
+	{
+		entry->remoterel.attnames[i] = pstrdup(remoterel->attnames[i]);
+		entry->remoterel.atttyps[i] = remoterel->atttyps[i];
+	}
+	entry->remoterel.replident = remoterel->replident;
+	entry->remoterel.attkeys = bms_copy(remoterel->attkeys);
+	MemoryContextSwitchTo(oldctx);
+}
+
+/*
+ * Find attribute index in TupleDesc struct by attribute name.
+ *
+ * Returns -1 if not found.
+ */
+static int
+logicalrep_rel_att_by_name(LogicalRepRelation *remoterel, const char *attname)
+{
+	int			i;
+
+	for (i = 0; i < remoterel->natts; i++)
+	{
+		if (strcmp(remoterel->attnames[i], attname) == 0)
+			return i;
+	}
+
+	return -1;
+}
+
+/*
+ * Report error with names of the missing local relation column(s), if any.
+ */
+static void
+logicalrep_report_missing_attrs(LogicalRepRelation *remoterel,
+								Bitmapset *missingatts)
+{
+	if (!bms_is_empty(missingatts))
+	{
+		StringInfoData missingattsbuf;
+		int			missingattcnt = 0;
+		int			i;
+
+		initStringInfo(&missingattsbuf);
+
+		while ((i = bms_first_member(missingatts)) >= 0)
+		{
+			missingattcnt++;
+			if (missingattcnt == 1)
+				appendStringInfo(&missingattsbuf, _("\"%s\""),
+								 remoterel->attnames[i]);
+			else
+				appendStringInfo(&missingattsbuf, _(", \"%s\""),
+								 remoterel->attnames[i]);
+		}
+
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg_plural("logical replication target relation \"%s.%s\" is missing replicated column: %s",
+							   "logical replication target relation \"%s.%s\" is missing replicated columns: %s",
+							   missingattcnt,
+							   remoterel->nspname,
+							   remoterel->relname,
+							   missingattsbuf.data)));
+	}
+}
+
+/*
+ * Check if replica identity matches and mark the updatable flag.
+ *
+ * We allow for stricter replica identity (fewer columns) on subscriber as
+ * that will not stop us from finding unique tuple. IE, if publisher has
+ * identity (id,timestamp) and subscriber just (id) this will not be a
+ * problem, but in the opposite scenario it will.
+ *
+ * We just mark the relation entry as not updatable here if the local
+ * replica identity is found to be insufficient for applying
+ * updates/deletes (inserts don't care!) and leave it to
+ * check_relation_updatable() to throw the actual error if needed.
+ */
+static void
+logicalrep_rel_mark_updatable(LogicalRepRelMapEntry *entry)
+{
+	Bitmapset  *idkey;
+	LogicalRepRelation *remoterel = &entry->remoterel;
+	int			i;
+
+	entry->updatable = true;
+
+	idkey = RelationGetIndexAttrBitmap(entry->localrel,
+									   INDEX_ATTR_BITMAP_IDENTITY_KEY);
+	/* fallback to PK if no replica identity */
+	if (idkey == NULL)
+	{
+		idkey = RelationGetIndexAttrBitmap(entry->localrel,
+										   INDEX_ATTR_BITMAP_PRIMARY_KEY);
+
+		/*
+		 * If no replica identity index and no PK, the published table must
+		 * have replica identity FULL.
+		 */
+		if (idkey == NULL && remoterel->replident != REPLICA_IDENTITY_FULL)
+			entry->updatable = false;
+	}
+
+	i = -1;
+	while ((i = bms_next_member(idkey, i)) >= 0)
+	{
+		int			attnum = i + FirstLowInvalidHeapAttributeNumber;
+
+		if (!AttrNumberIsForUserDefinedAttr(attnum))
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					 errmsg("logical replication target relation \"%s.%s\" uses "
+							"system columns in REPLICA IDENTITY index",
+							remoterel->nspname, remoterel->relname)));
+
+		attnum = AttrNumberGetAttrOffset(attnum);
+
+		if (entry->attrmap->attnums[attnum] < 0 ||
+			!bms_is_member(entry->attrmap->attnums[attnum], remoterel->attkeys))
+		{
+			entry->updatable = false;
+			break;
+		}
+	}
+}
+
+/*
+ * Open the local relation associated with the remote one.
+ *
+ * Rebuilds the Relcache mapping if it was invalidated by local DDL.
+ */
+LogicalRepRelMapEntry *
+logicalrep_rel_open(LogicalRepRelId remoteid, LOCKMODE lockmode)
+{
+	LogicalRepRelMapEntry *entry;
+	bool		found;
+	LogicalRepRelation *remoterel;
+
+	if (LogicalRepRelMap == NULL)
+		logicalrep_relmap_init();
+
+	/* Search for existing entry. */
+	entry = hash_search(LogicalRepRelMap, (void *) &remoteid,
+						HASH_FIND, &found);
+
+	if (!found)
+		elog(ERROR, "no relation map entry for remote relation ID %u",
+			 remoteid);
+
+	remoterel = &entry->remoterel;
+
+	/* Ensure we don't leak a relcache refcount. */
+	if (entry->localrel)
+		elog(ERROR, "remote relation ID %u is already open", remoteid);
+
+	/*
+	 * When opening and locking a relation, pending invalidation messages are
+	 * processed which can invalidate the relation.  Hence, if the entry is
+	 * currently considered valid, try to open the local relation by OID and
+	 * see if invalidation ensues.
+	 */
+	if (entry->localrelvalid)
+	{
+		entry->localrel = try_table_open(entry->localreloid, lockmode);
+		if (!entry->localrel)
+		{
+			/* Table was renamed or dropped. */
+			entry->localrelvalid = false;
+		}
+		else if (!entry->localrelvalid)
+		{
+			/* Note we release the no-longer-useful lock here. */
+			table_close(entry->localrel, lockmode);
+			entry->localrel = NULL;
+		}
+	}
+
+	/*
+	 * If the entry has been marked invalid since we last had lock on it,
+	 * re-open the local relation by name and rebuild all derived data.
+	 */
+	if (!entry->localrelvalid)
+	{
+		Oid			relid;
+		TupleDesc	desc;
+		MemoryContext oldctx;
+		int			i;
+		Bitmapset  *missingatts;
+
+		/* Release the no-longer-useful attrmap, if any. */
+		if (entry->attrmap)
+		{
+			free_attrmap(entry->attrmap);
+			entry->attrmap = NULL;
+		}
+
+		/* Try to find and lock the relation by name. */
+		relid = RangeVarGetRelid(makeRangeVar(remoterel->nspname,
+											  remoterel->relname, -1),
+								 lockmode, true);
+		if (!OidIsValid(relid))
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					 errmsg("logical replication target relation \"%s.%s\" does not exist",
+							remoterel->nspname, remoterel->relname)));
+		entry->localrel = table_open(relid, NoLock);
+		entry->localreloid = relid;
+
+		/* Check for supported relkind. */
+		CheckSubscriptionRelkind(entry->localrel->rd_rel->relkind,
+								 remoterel->nspname, remoterel->relname);
+
+		/*
+		 * Build the mapping of local attribute numbers to remote attribute
+		 * numbers and validate that we don't miss any replicated columns as
+		 * that would result in potentially unwanted data loss.
+		 */
+		desc = RelationGetDescr(entry->localrel);
+		oldctx = MemoryContextSwitchTo(LogicalRepRelMapContext);
+		entry->attrmap = make_attrmap(desc->natts);
+		MemoryContextSwitchTo(oldctx);
+
+		/* check and report missing attrs, if any */
+		missingatts = bms_add_range(NULL, 0, remoterel->natts - 1);
+		for (i = 0; i < desc->natts; i++)
+		{
+			int			attnum;
+			Form_pg_attribute attr = TupleDescAttr(desc, i);
+
+			if (attr->attisdropped || attr->attgenerated)
+			{
+				entry->attrmap->attnums[i] = -1;
+				continue;
+			}
+
+			attnum = logicalrep_rel_att_by_name(remoterel,
+												NameStr(attr->attname));
+
+			entry->attrmap->attnums[i] = attnum;
+			if (attnum >= 0)
+				missingatts = bms_del_member(missingatts, attnum);
+		}
+
+		logicalrep_report_missing_attrs(remoterel, missingatts);
+
+		/* be tidy */
+		bms_free(missingatts);
+
+		/*
+		 * Set if the table's replica identity is enough to apply
+		 * update/delete.
+		 */
+		logicalrep_rel_mark_updatable(entry);
+
+		entry->localrelvalid = true;
+	}
+
+	if (entry->state != SUBREL_STATE_READY)
+		entry->state = GetSubscriptionRelState(MySubscription->oid,
+											   entry->localreloid,
+											   &entry->statelsn);
+
+	return entry;
+}
+
+/*
+ * Close the previously opened logical relation.
+ */
+void
+logicalrep_rel_close(LogicalRepRelMapEntry *rel, LOCKMODE lockmode)
+{
+	table_close(rel->localrel, lockmode);
+	rel->localrel = NULL;
+}
+
+/*
+ * Partition cache: look up partition LogicalRepRelMapEntry's
+ *
+ * Unlike relation map cache, this is keyed by partition OID, not remote
+ * relation OID, because we only have to use this cache in the case where
+ * partitions are not directly mapped to any remote relation, such as when
+ * replication is occurring with one of their ancestors as target.
+ */
+
+/*
+ * Relcache invalidation callback
+ */
+static void
+logicalrep_partmap_invalidate_cb(Datum arg, Oid reloid)
+{
+	LogicalRepPartMapEntry *entry;
+
+	/* Just to be sure. */
+	if (LogicalRepPartMap == NULL)
+		return;
+
+	if (reloid != InvalidOid)
+	{
+		HASH_SEQ_STATUS status;
+
+		hash_seq_init(&status, LogicalRepPartMap);
+
+		/* TODO, use inverse lookup hashtable? */
+		while ((entry = (LogicalRepPartMapEntry *) hash_seq_search(&status)) != NULL)
+		{
+			if (entry->relmapentry.localreloid == reloid)
+			{
+				entry->relmapentry.localrelvalid = false;
+				hash_seq_term(&status);
+				break;
+			}
+		}
+	}
+	else
+	{
+		/* invalidate all cache entries */
+		HASH_SEQ_STATUS status;
+
+		hash_seq_init(&status, LogicalRepPartMap);
+
+		while ((entry = (LogicalRepPartMapEntry *) hash_seq_search(&status)) != NULL)
+			entry->relmapentry.localrelvalid = false;
+	}
+}
+
+/*
+ * Reset the entries in the partition map that refer to remoterel.
+ *
+ * Called when new relation mapping is sent by the publisher to update our
+ * expected view of incoming data from said publisher.
+ *
+ * Note that we don't update the remoterel information in the entry here,
+ * we will update the information in logicalrep_partition_open to avoid
+ * unnecessary work.
+ */
+void
+logicalrep_partmap_reset_relmap(LogicalRepRelation *remoterel)
+{
+	HASH_SEQ_STATUS status;
+	LogicalRepPartMapEntry *part_entry;
+	LogicalRepRelMapEntry *entry;
+
+	if (LogicalRepPartMap == NULL)
+		return;
+
+	hash_seq_init(&status, LogicalRepPartMap);
+	while ((part_entry = (LogicalRepPartMapEntry *) hash_seq_search(&status)) != NULL)
+	{
+		entry = &part_entry->relmapentry;
+
+		if (entry->remoterel.remoteid != remoterel->remoteid)
+			continue;
+
+		logicalrep_relmap_free_entry(entry);
+
+		memset(entry, 0, sizeof(LogicalRepRelMapEntry));
+	}
+}
+
+/*
+ * Initialize the partition map cache.
+ */
+static void
+logicalrep_partmap_init(void)
+{
+	HASHCTL		ctl;
+
+	if (!LogicalRepPartMapContext)
+		LogicalRepPartMapContext =
+			AllocSetContextCreate(CacheMemoryContext,
+								  "LogicalRepPartMapContext",
+								  ALLOCSET_DEFAULT_SIZES);
+
+	/* Initialize the relation hash table. */
+	ctl.keysize = sizeof(Oid);	/* partition OID */
+	ctl.entrysize = sizeof(LogicalRepPartMapEntry);
+	ctl.hcxt = LogicalRepPartMapContext;
+
+	LogicalRepPartMap = hash_create("logicalrep partition map cache", 64, &ctl,
+									HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
+
+	/* Watch for invalidation events. */
+	CacheRegisterRelcacheCallback(logicalrep_partmap_invalidate_cb,
+								  (Datum) 0);
+}
+
+/*
+ * logicalrep_partition_open
+ *
+ * Returned entry reuses most of the values of the root table's entry, save
+ * the attribute map, which can be different for the partition.  However,
+ * we must physically copy all the data, in case the root table's entry
+ * gets freed/rebuilt.
+ *
+ * Note there's no logicalrep_partition_close, because the caller closes the
+ * component relation.
+ */
+LogicalRepRelMapEntry *
+logicalrep_partition_open(LogicalRepRelMapEntry *root,
+						  Relation partrel, AttrMap *map)
+{
+	LogicalRepRelMapEntry *entry;
+	LogicalRepPartMapEntry *part_entry;
+	LogicalRepRelation *remoterel = &root->remoterel;
+	Oid			partOid = RelationGetRelid(partrel);
+	AttrMap    *attrmap = root->attrmap;
+	bool		found;
+	MemoryContext oldctx;
+
+	if (LogicalRepPartMap == NULL)
+		logicalrep_partmap_init();
+
+	/* Search for existing entry. */
+	part_entry = (LogicalRepPartMapEntry *) hash_search(LogicalRepPartMap,
+														(void *) &partOid,
+														HASH_ENTER, &found);
+
+	entry = &part_entry->relmapentry;
+
+	/*
+	 * We must always overwrite entry->localrel with the latest partition
+	 * Relation pointer, because the Relation pointed to by the old value may
+	 * have been cleared after the caller would have closed the partition
+	 * relation after the last use of this entry.  Note that localrelvalid is
+	 * only updated by the relcache invalidation callback, so it may still be
+	 * true irrespective of whether the Relation pointed to by localrel has
+	 * been cleared or not.
+	 */
+	if (found && entry->localrelvalid)
+	{
+		entry->localrel = partrel;
+		return entry;
+	}
+
+	/* Switch to longer-lived context. */
+	oldctx = MemoryContextSwitchTo(LogicalRepPartMapContext);
+
+	if (!found)
+	{
+		memset(part_entry, 0, sizeof(LogicalRepPartMapEntry));
+		part_entry->partoid = partOid;
+	}
+
+	/* Release the no-longer-useful attrmap, if any. */
+	if (entry->attrmap)
+	{
+		free_attrmap(entry->attrmap);
+		entry->attrmap = NULL;
+	}
+
+	if (!entry->remoterel.remoteid)
+	{
+		int			i;
+
+		/* Remote relation is copied as-is from the root entry. */
+		entry = &part_entry->relmapentry;
+		entry->remoterel.remoteid = remoterel->remoteid;
+		entry->remoterel.nspname = pstrdup(remoterel->nspname);
+		entry->remoterel.relname = pstrdup(remoterel->relname);
+		entry->remoterel.natts = remoterel->natts;
+		entry->remoterel.attnames = palloc(remoterel->natts * sizeof(char *));
+		entry->remoterel.atttyps = palloc(remoterel->natts * sizeof(Oid));
+		for (i = 0; i < remoterel->natts; i++)
+		{
+			entry->remoterel.attnames[i] = pstrdup(remoterel->attnames[i]);
+			entry->remoterel.atttyps[i] = remoterel->atttyps[i];
+		}
+		entry->remoterel.replident = remoterel->replident;
+		entry->remoterel.attkeys = bms_copy(remoterel->attkeys);
+	}
+
+	entry->localrel = partrel;
+	entry->localreloid = partOid;
+
+	/*
+	 * If the partition's attributes don't match the root relation's, we'll
+	 * need to make a new attrmap which maps partition attribute numbers to
+	 * remoterel's, instead of the original which maps root relation's
+	 * attribute numbers to remoterel's.
+	 *
+	 * Note that 'map' which comes from the tuple routing data structure
+	 * contains 1-based attribute numbers (of the parent relation).  However,
+	 * the map in 'entry', a logical replication data structure, contains
+	 * 0-based attribute numbers (of the remote relation).
+	 */
+	if (map)
+	{
+		AttrNumber	attno;
+
+		entry->attrmap = make_attrmap(map->maplen);
+		for (attno = 0; attno < entry->attrmap->maplen; attno++)
+		{
+			AttrNumber	root_attno = map->attnums[attno];
+
+			/* 0 means it's a dropped attribute.  See comments atop AttrMap. */
+			if (root_attno == 0)
+				entry->attrmap->attnums[attno] = -1;
+			else
+				entry->attrmap->attnums[attno] = attrmap->attnums[root_attno - 1];
+		}
+	}
+	else
+	{
+		/* Lacking copy_attmap, do this the hard way. */
+		entry->attrmap = make_attrmap(attrmap->maplen);
+		memcpy(entry->attrmap->attnums, attrmap->attnums,
+			   attrmap->maplen * sizeof(AttrNumber));
+	}
+
+	/* Set if the table's replica identity is enough to apply update/delete. */
+	logicalrep_rel_mark_updatable(entry);
+
+	entry->localrelvalid = true;
+
+	/* state and statelsn are left set to 0. */
+	MemoryContextSwitchTo(oldctx);
+
+	return entry;
+}
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
new file mode 100644
index 0000000..e59d139
--- /dev/null
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -0,0 +1,5156 @@
+/*-------------------------------------------------------------------------
+ *
+ * reorderbuffer.c
+ *	  PostgreSQL logical replay/reorder buffer management
+ *
+ *
+ * Copyright (c) 2012-2021, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/reorderbuffer.c
+ *
+ * NOTES
+ *	  This module gets handed individual pieces of transactions in the order
+ *	  they are written to the WAL and is responsible to reassemble them into
+ *	  toplevel transaction sized pieces. When a transaction is completely
+ *	  reassembled - signaled by reading the transaction commit record - it
+ *	  will then call the output plugin (cf. ReorderBufferCommit()) with the
+ *	  individual changes. The output plugins rely on snapshots built by
+ *	  snapbuild.c which hands them to us.
+ *
+ *	  Transactions and subtransactions/savepoints in postgres are not
+ *	  immediately linked to each other from outside the performing
+ *	  backend. Only at commit/abort (or special xact_assignment records) they
+ *	  are linked together. Which means that we will have to splice together a
+ *	  toplevel transaction from its subtransactions. To do that efficiently we
+ *	  build a binary heap indexed by the smallest current lsn of the individual
+ *	  subtransactions' changestreams. As the individual streams are inherently
+ *	  ordered by LSN - since that is where we build them from - the transaction
+ *	  can easily be reassembled by always using the subtransaction with the
+ *	  smallest current LSN from the heap.
+ *
+ *	  In order to cope with large transactions - which can be several times as
+ *	  big as the available memory - this module supports spooling the contents
+ *	  of a large transactions to disk. When the transaction is replayed the
+ *	  contents of individual (sub-)transactions will be read from disk in
+ *	  chunks.
+ *
+ *	  This module also has to deal with reassembling toast records from the
+ *	  individual chunks stored in WAL. When a new (or initial) version of a
+ *	  tuple is stored in WAL it will always be preceded by the toast chunks
+ *	  emitted for the columns stored out of line. Within a single toplevel
+ *	  transaction there will be no other data carrying records between a row's
+ *	  toast chunks and the row data itself. See ReorderBufferToast* for
+ *	  details.
+ *
+ *	  ReorderBuffer uses two special memory context types - SlabContext for
+ *	  allocations of fixed-length structures (changes and transactions), and
+ *	  GenerationContext for the variable-length transaction data (allocated
+ *	  and freed in groups with similar lifespans).
+ *
+ *	  To limit the amount of memory used by decoded changes, we track memory
+ *	  used at the reorder buffer level (i.e. total amount of memory), and for
+ *	  each transaction. When the total amount of used memory exceeds the
+ *	  limit, the transaction consuming the most memory is then serialized to
+ *	  disk.
+ *
+ *	  Only decoded changes are evicted from memory (spilled to disk), not the
+ *	  transaction records. The number of toplevel transactions is limited,
+ *	  but a transaction with many subtransactions may still consume significant
+ *	  amounts of memory. However, the transaction records are fairly small and
+ *	  are not included in the memory limit.
+ *
+ *	  The current eviction algorithm is very simple - the transaction is
+ *	  picked merely by size, while it might be useful to also consider age
+ *	  (LSN) of the changes for example. With the new Generational memory
+ *	  allocator, evicting the oldest changes would make it more likely the
+ *	  memory gets actually freed.
+ *
+ *	  We still rely on max_changes_in_memory when loading serialized changes
+ *	  back into memory. At that point we can't use the memory limit directly
+ *	  as we load the subxacts independently. One option to deal with this
+ *	  would be to count the subxacts, and allow each to allocate 1/N of the
+ *	  memory limit. That however does not seem very appealing, because with
+ *	  many subtransactions it may easily cause thrashing (short cycles of
+ *	  deserializing and applying very few changes). We probably should give
+ *	  a bit more memory to the oldest subtransactions, because it's likely
+ *	  they are the source for the next sequence of changes.
+ *
+ * -------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <unistd.h>
+#include <sys/stat.h>
+
+#include "access/detoast.h"
+#include "access/heapam.h"
+#include "access/rewriteheap.h"
+#include "access/transam.h"
+#include "access/xact.h"
+#include "access/xlog_internal.h"
+#include "catalog/catalog.h"
+#include "lib/binaryheap.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "replication/logical.h"
+#include "replication/reorderbuffer.h"
+#include "replication/slot.h"
+#include "replication/snapbuild.h"	/* just for SnapBuildSnapDecRefcount */
+#include "storage/bufmgr.h"
+#include "storage/fd.h"
+#include "storage/sinval.h"
+#include "utils/builtins.h"
+#include "utils/combocid.h"
+#include "utils/memdebug.h"
+#include "utils/memutils.h"
+#include "utils/rel.h"
+#include "utils/relfilenodemap.h"
+
+
+/* entry for a hash table we use to map from xid to our transaction state */
+typedef struct ReorderBufferTXNByIdEnt
+{
+	TransactionId xid;
+	ReorderBufferTXN *txn;
+} ReorderBufferTXNByIdEnt;
+
+/* data structures for (relfilenode, ctid) => (cmin, cmax) mapping */
+typedef struct ReorderBufferTupleCidKey
+{
+	RelFileNode relnode;
+	ItemPointerData tid;
+} ReorderBufferTupleCidKey;
+
+typedef struct ReorderBufferTupleCidEnt
+{
+	ReorderBufferTupleCidKey key;
+	CommandId	cmin;
+	CommandId	cmax;
+	CommandId	combocid;		/* just for debugging */
+} ReorderBufferTupleCidEnt;
+
+/* Virtual file descriptor with file offset tracking */
+typedef struct TXNEntryFile
+{
+	File		vfd;			/* -1 when the file is closed */
+	off_t		curOffset;		/* offset for next write or read. Reset to 0
+								 * when vfd is opened. */
+} TXNEntryFile;
+
+/* k-way in-order change iteration support structures */
+typedef struct ReorderBufferIterTXNEntry
+{
+	XLogRecPtr	lsn;
+	ReorderBufferChange *change;
+	ReorderBufferTXN *txn;
+	TXNEntryFile file;
+	XLogSegNo	segno;
+} ReorderBufferIterTXNEntry;
+
+typedef struct ReorderBufferIterTXNState
+{
+	binaryheap *heap;
+	Size		nr_txns;
+	dlist_head	old_change;
+	ReorderBufferIterTXNEntry entries[FLEXIBLE_ARRAY_MEMBER];
+} ReorderBufferIterTXNState;
+
+/* toast datastructures */
+typedef struct ReorderBufferToastEnt
+{
+	Oid			chunk_id;		/* toast_table.chunk_id */
+	int32		last_chunk_seq; /* toast_table.chunk_seq of the last chunk we
+								 * have seen */
+	Size		num_chunks;		/* number of chunks we've already seen */
+	Size		size;			/* combined size of chunks seen */
+	dlist_head	chunks;			/* linked list of chunks */
+	struct varlena *reconstructed;	/* reconstructed varlena now pointed to in
+									 * main tup */
+} ReorderBufferToastEnt;
+
+/* Disk serialization support datastructures */
+typedef struct ReorderBufferDiskChange
+{
+	Size		size;
+	ReorderBufferChange change;
+	/* data follows */
+} ReorderBufferDiskChange;
+
+#define IsSpecInsert(action) \
+( \
+	((action) == REORDER_BUFFER_CHANGE_INTERNAL_SPEC_INSERT) \
+)
+#define IsSpecConfirmOrAbort(action) \
+( \
+	(((action) == REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM) || \
+	((action) == REORDER_BUFFER_CHANGE_INTERNAL_SPEC_ABORT)) \
+)
+#define IsInsertOrUpdate(action) \
+( \
+	(((action) == REORDER_BUFFER_CHANGE_INSERT) || \
+	((action) == REORDER_BUFFER_CHANGE_UPDATE) || \
+	((action) == REORDER_BUFFER_CHANGE_INTERNAL_SPEC_INSERT)) \
+)
+
+/*
+ * Maximum number of changes kept in memory, per transaction. After that,
+ * changes are spooled to disk.
+ *
+ * The current value should be sufficient to decode the entire transaction
+ * without hitting disk in OLTP workloads, while starting to spool to disk in
+ * other workloads reasonably fast.
+ *
+ * At some point in the future it probably makes sense to have a more elaborate
+ * resource management here, but it's not entirely clear what that would look
+ * like.
+ */
+int			logical_decoding_work_mem;
+static const Size max_changes_in_memory = 4096; /* XXX for restore only */
+
+/* ---------------------------------------
+ * primary reorderbuffer support routines
+ * ---------------------------------------
+ */
+static ReorderBufferTXN *ReorderBufferGetTXN(ReorderBuffer *rb);
+static void ReorderBufferReturnTXN(ReorderBuffer *rb, ReorderBufferTXN *txn);
+static ReorderBufferTXN *ReorderBufferTXNByXid(ReorderBuffer *rb,
+											   TransactionId xid, bool create, bool *is_new,
+											   XLogRecPtr lsn, bool create_as_top);
+static void ReorderBufferTransferSnapToParent(ReorderBufferTXN *txn,
+											  ReorderBufferTXN *subtxn);
+
+static void AssertTXNLsnOrder(ReorderBuffer *rb);
+
+/* ---------------------------------------
+ * support functions for lsn-order iterating over the ->changes of a
+ * transaction and its subtransactions
+ *
+ * used for iteration over the k-way heap merge of a transaction and its
+ * subtransactions
+ * ---------------------------------------
+ */
+static void ReorderBufferIterTXNInit(ReorderBuffer *rb, ReorderBufferTXN *txn,
+									 ReorderBufferIterTXNState *volatile *iter_state);
+static ReorderBufferChange *ReorderBufferIterTXNNext(ReorderBuffer *rb, ReorderBufferIterTXNState *state);
+static void ReorderBufferIterTXNFinish(ReorderBuffer *rb,
+									   ReorderBufferIterTXNState *state);
+static void ReorderBufferExecuteInvalidations(uint32 nmsgs, SharedInvalidationMessage *msgs);
+
+/*
+ * ---------------------------------------
+ * Disk serialization support functions
+ * ---------------------------------------
+ */
+static void ReorderBufferCheckMemoryLimit(ReorderBuffer *rb);
+static void ReorderBufferSerializeTXN(ReorderBuffer *rb, ReorderBufferTXN *txn);
+static void ReorderBufferSerializeChange(ReorderBuffer *rb, ReorderBufferTXN *txn,
+										 int fd, ReorderBufferChange *change);
+static Size ReorderBufferRestoreChanges(ReorderBuffer *rb, ReorderBufferTXN *txn,
+										TXNEntryFile *file, XLogSegNo *segno);
+static void ReorderBufferRestoreChange(ReorderBuffer *rb, ReorderBufferTXN *txn,
+									   char *change);
+static void ReorderBufferRestoreCleanup(ReorderBuffer *rb, ReorderBufferTXN *txn);
+static void ReorderBufferTruncateTXN(ReorderBuffer *rb, ReorderBufferTXN *txn,
+									 bool txn_prepared);
+static void ReorderBufferCleanupSerializedTXNs(const char *slotname);
+static void ReorderBufferSerializedPath(char *path, ReplicationSlot *slot,
+										TransactionId xid, XLogSegNo segno);
+
+static void ReorderBufferFreeSnap(ReorderBuffer *rb, Snapshot snap);
+static Snapshot ReorderBufferCopySnap(ReorderBuffer *rb, Snapshot orig_snap,
+									  ReorderBufferTXN *txn, CommandId cid);
+
+/*
+ * ---------------------------------------
+ * Streaming support functions
+ * ---------------------------------------
+ */
+static inline bool ReorderBufferCanStream(ReorderBuffer *rb);
+static inline bool ReorderBufferCanStartStreaming(ReorderBuffer *rb);
+static void ReorderBufferStreamTXN(ReorderBuffer *rb, ReorderBufferTXN *txn);
+static void ReorderBufferStreamCommit(ReorderBuffer *rb, ReorderBufferTXN *txn);
+
+/* ---------------------------------------
+ * toast reassembly support
+ * ---------------------------------------
+ */
+static void ReorderBufferToastInitHash(ReorderBuffer *rb, ReorderBufferTXN *txn);
+static void ReorderBufferToastReset(ReorderBuffer *rb, ReorderBufferTXN *txn);
+static void ReorderBufferToastReplace(ReorderBuffer *rb, ReorderBufferTXN *txn,
+									  Relation relation, ReorderBufferChange *change);
+static void ReorderBufferToastAppendChunk(ReorderBuffer *rb, ReorderBufferTXN *txn,
+										  Relation relation, ReorderBufferChange *change);
+
+/*
+ * ---------------------------------------
+ * memory accounting
+ * ---------------------------------------
+ */
+static Size ReorderBufferChangeSize(ReorderBufferChange *change);
+static void ReorderBufferChangeMemoryUpdate(ReorderBuffer *rb,
+											ReorderBufferChange *change,
+											bool addition, Size sz);
+
+/*
+ * Allocate a new ReorderBuffer and clean out any old serialized state from
+ * prior ReorderBuffer instances for the same slot.
+ */
+ReorderBuffer *
+ReorderBufferAllocate(void)
+{
+	ReorderBuffer *buffer;
+	HASHCTL		hash_ctl;
+	MemoryContext new_ctx;
+
+	Assert(MyReplicationSlot != NULL);
+
+	/* allocate memory in own context, to have better accountability */
+	new_ctx = AllocSetContextCreate(CurrentMemoryContext,
+									"ReorderBuffer",
+									ALLOCSET_DEFAULT_SIZES);
+
+	buffer =
+		(ReorderBuffer *) MemoryContextAlloc(new_ctx, sizeof(ReorderBuffer));
+
+	memset(&hash_ctl, 0, sizeof(hash_ctl));
+
+	buffer->context = new_ctx;
+
+	buffer->change_context = SlabContextCreate(new_ctx,
+											   "Change",
+											   SLAB_DEFAULT_BLOCK_SIZE,
+											   sizeof(ReorderBufferChange));
+
+	buffer->txn_context = SlabContextCreate(new_ctx,
+											"TXN",
+											SLAB_DEFAULT_BLOCK_SIZE,
+											sizeof(ReorderBufferTXN));
+
+	buffer->tup_context = GenerationContextCreate(new_ctx,
+												  "Tuples",
+												  SLAB_LARGE_BLOCK_SIZE);
+
+	hash_ctl.keysize = sizeof(TransactionId);
+	hash_ctl.entrysize = sizeof(ReorderBufferTXNByIdEnt);
+	hash_ctl.hcxt = buffer->context;
+
+	buffer->by_txn = hash_create("ReorderBufferByXid", 1000, &hash_ctl,
+								 HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
+
+	buffer->by_txn_last_xid = InvalidTransactionId;
+	buffer->by_txn_last_txn = NULL;
+
+	buffer->outbuf = NULL;
+	buffer->outbufsize = 0;
+	buffer->size = 0;
+
+	buffer->spillTxns = 0;
+	buffer->spillCount = 0;
+	buffer->spillBytes = 0;
+	buffer->streamTxns = 0;
+	buffer->streamCount = 0;
+	buffer->streamBytes = 0;
+	buffer->totalTxns = 0;
+	buffer->totalBytes = 0;
+
+	buffer->current_restart_decoding_lsn = InvalidXLogRecPtr;
+
+	dlist_init(&buffer->toplevel_by_lsn);
+	dlist_init(&buffer->txns_by_base_snapshot_lsn);
+
+	/*
+	 * Ensure there's no stale data from prior uses of this slot, in case some
+	 * prior exit avoided calling ReorderBufferFree. Failure to do this can
+	 * produce duplicated txns, and it's very cheap if there's nothing there.
+	 */
+	ReorderBufferCleanupSerializedTXNs(NameStr(MyReplicationSlot->data.name));
+
+	return buffer;
+}
+
+/*
+ * Free a ReorderBuffer
+ */
+void
+ReorderBufferFree(ReorderBuffer *rb)
+{
+	MemoryContext context = rb->context;
+
+	/*
+	 * We free separately allocated data by entirely scrapping reorderbuffer's
+	 * memory context.
+	 */
+	MemoryContextDelete(context);
+
+	/* Free disk space used by unconsumed reorder buffers */
+	ReorderBufferCleanupSerializedTXNs(NameStr(MyReplicationSlot->data.name));
+}
+
+/*
+ * Get an unused, possibly preallocated, ReorderBufferTXN.
+ */
+static ReorderBufferTXN *
+ReorderBufferGetTXN(ReorderBuffer *rb)
+{
+	ReorderBufferTXN *txn;
+
+	txn = (ReorderBufferTXN *)
+		MemoryContextAlloc(rb->txn_context, sizeof(ReorderBufferTXN));
+
+	memset(txn, 0, sizeof(ReorderBufferTXN));
+
+	dlist_init(&txn->changes);
+	dlist_init(&txn->tuplecids);
+	dlist_init(&txn->subtxns);
+
+	/* InvalidCommandId is not zero, so set it explicitly */
+	txn->command_id = InvalidCommandId;
+	txn->output_plugin_private = NULL;
+
+	return txn;
+}
+
+/*
+ * Free a ReorderBufferTXN.
+ */
+static void
+ReorderBufferReturnTXN(ReorderBuffer *rb, ReorderBufferTXN *txn)
+{
+	/* clean the lookup cache if we were cached (quite likely) */
+	if (rb->by_txn_last_xid == txn->xid)
+	{
+		rb->by_txn_last_xid = InvalidTransactionId;
+		rb->by_txn_last_txn = NULL;
+	}
+
+	/* free data that's contained */
+
+	if (txn->gid != NULL)
+	{
+		pfree(txn->gid);
+		txn->gid = NULL;
+	}
+
+	if (txn->tuplecid_hash != NULL)
+	{
+		hash_destroy(txn->tuplecid_hash);
+		txn->tuplecid_hash = NULL;
+	}
+
+	if (txn->invalidations)
+	{
+		pfree(txn->invalidations);
+		txn->invalidations = NULL;
+	}
+
+	/* Reset the toast hash */
+	ReorderBufferToastReset(rb, txn);
+
+	pfree(txn);
+}
+
+/*
+ * Get a fresh ReorderBufferChange.
+ */
+ReorderBufferChange *
+ReorderBufferGetChange(ReorderBuffer *rb)
+{
+	ReorderBufferChange *change;
+
+	change = (ReorderBufferChange *)
+		MemoryContextAlloc(rb->change_context, sizeof(ReorderBufferChange));
+
+	memset(change, 0, sizeof(ReorderBufferChange));
+	return change;
+}
+
+/*
+ * Free a ReorderBufferChange and update memory accounting, if requested.
+ */
+void
+ReorderBufferReturnChange(ReorderBuffer *rb, ReorderBufferChange *change,
+						  bool upd_mem)
+{
+	/* update memory accounting info */
+	if (upd_mem)
+		ReorderBufferChangeMemoryUpdate(rb, change, false,
+										ReorderBufferChangeSize(change));
+
+	/* free contained data */
+	switch (change->action)
+	{
+		case REORDER_BUFFER_CHANGE_INSERT:
+		case REORDER_BUFFER_CHANGE_UPDATE:
+		case REORDER_BUFFER_CHANGE_DELETE:
+		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_INSERT:
+			if (change->data.tp.newtuple)
+			{
+				ReorderBufferReturnTupleBuf(rb, change->data.tp.newtuple);
+				change->data.tp.newtuple = NULL;
+			}
+
+			if (change->data.tp.oldtuple)
+			{
+				ReorderBufferReturnTupleBuf(rb, change->data.tp.oldtuple);
+				change->data.tp.oldtuple = NULL;
+			}
+			break;
+		case REORDER_BUFFER_CHANGE_MESSAGE:
+			if (change->data.msg.prefix != NULL)
+				pfree(change->data.msg.prefix);
+			change->data.msg.prefix = NULL;
+			if (change->data.msg.message != NULL)
+				pfree(change->data.msg.message);
+			change->data.msg.message = NULL;
+			break;
+		case REORDER_BUFFER_CHANGE_INVALIDATION:
+			if (change->data.inval.invalidations)
+				pfree(change->data.inval.invalidations);
+			change->data.inval.invalidations = NULL;
+			break;
+		case REORDER_BUFFER_CHANGE_INTERNAL_SNAPSHOT:
+			if (change->data.snapshot)
+			{
+				ReorderBufferFreeSnap(rb, change->data.snapshot);
+				change->data.snapshot = NULL;
+			}
+			break;
+			/* no data in addition to the struct itself */
+		case REORDER_BUFFER_CHANGE_TRUNCATE:
+			if (change->data.truncate.relids != NULL)
+			{
+				ReorderBufferReturnRelids(rb, change->data.truncate.relids);
+				change->data.truncate.relids = NULL;
+			}
+			break;
+		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM:
+		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_ABORT:
+		case REORDER_BUFFER_CHANGE_INTERNAL_COMMAND_ID:
+		case REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID:
+			break;
+	}
+
+	pfree(change);
+}
+
+/*
+ * Get a fresh ReorderBufferTupleBuf fitting at least a tuple of size
+ * tuple_len (excluding header overhead).
+ */
+ReorderBufferTupleBuf *
+ReorderBufferGetTupleBuf(ReorderBuffer *rb, Size tuple_len)
+{
+	ReorderBufferTupleBuf *tuple;
+	Size		alloc_len;
+
+	alloc_len = tuple_len + SizeofHeapTupleHeader;
+
+	tuple = (ReorderBufferTupleBuf *)
+		MemoryContextAlloc(rb->tup_context,
+						   sizeof(ReorderBufferTupleBuf) +
+						   MAXIMUM_ALIGNOF + alloc_len);
+	tuple->alloc_tuple_size = alloc_len;
+	tuple->tuple.t_data = ReorderBufferTupleBufData(tuple);
+
+	return tuple;
+}
+
+/*
+ * Free a ReorderBufferTupleBuf.
+ */
+void
+ReorderBufferReturnTupleBuf(ReorderBuffer *rb, ReorderBufferTupleBuf *tuple)
+{
+	pfree(tuple);
+}
+
+/*
+ * Get an array for relids of truncated relations.
+ *
+ * We use the global memory context (for the whole reorder buffer), because
+ * none of the existing ones seems like a good match (some are SLAB, so we
+ * can't use those, and tup_context is meant for tuple data, not relids). We
+ * could add yet another context, but it seems like an overkill - TRUNCATE is
+ * not particularly common operation, so it does not seem worth it.
+ */
+Oid *
+ReorderBufferGetRelids(ReorderBuffer *rb, int nrelids)
+{
+	Oid		   *relids;
+	Size		alloc_len;
+
+	alloc_len = sizeof(Oid) * nrelids;
+
+	relids = (Oid *) MemoryContextAlloc(rb->context, alloc_len);
+
+	return relids;
+}
+
+/*
+ * Free an array of relids.
+ */
+void
+ReorderBufferReturnRelids(ReorderBuffer *rb, Oid *relids)
+{
+	pfree(relids);
+}
+
+/*
+ * Return the ReorderBufferTXN from the given buffer, specified by Xid.
+ * If create is true, and a transaction doesn't already exist, create it
+ * (with the given LSN, and as top transaction if that's specified);
+ * when this happens, is_new is set to true.
+ */
+static ReorderBufferTXN *
+ReorderBufferTXNByXid(ReorderBuffer *rb, TransactionId xid, bool create,
+					  bool *is_new, XLogRecPtr lsn, bool create_as_top)
+{
+	ReorderBufferTXN *txn;
+	ReorderBufferTXNByIdEnt *ent;
+	bool		found;
+
+	Assert(TransactionIdIsValid(xid));
+
+	/*
+	 * Check the one-entry lookup cache first
+	 */
+	if (TransactionIdIsValid(rb->by_txn_last_xid) &&
+		rb->by_txn_last_xid == xid)
+	{
+		txn = rb->by_txn_last_txn;
+
+		if (txn != NULL)
+		{
+			/* found it, and it's valid */
+			if (is_new)
+				*is_new = false;
+			return txn;
+		}
+
+		/*
+		 * cached as non-existent, and asked not to create? Then nothing else
+		 * to do.
+		 */
+		if (!create)
+			return NULL;
+		/* otherwise fall through to create it */
+	}
+
+	/*
+	 * If the cache wasn't hit or it yielded a "does-not-exist" and we want
+	 * to create an entry.
+	 */
+
+	/* search the lookup table */
+	ent = (ReorderBufferTXNByIdEnt *)
+		hash_search(rb->by_txn,
+					(void *) &xid,
+					create ? HASH_ENTER : HASH_FIND,
+					&found);
+	if (found)
+		txn = ent->txn;
+	else if (create)
+	{
+		/* initialize the new entry, if creation was requested */
+		Assert(ent != NULL);
+		Assert(lsn != InvalidXLogRecPtr);
+
+		ent->txn = ReorderBufferGetTXN(rb);
+		ent->txn->xid = xid;
+		txn = ent->txn;
+		txn->first_lsn = lsn;
+		txn->restart_decoding_lsn = rb->current_restart_decoding_lsn;
+
+		if (create_as_top)
+		{
+			dlist_push_tail(&rb->toplevel_by_lsn, &txn->node);
+			AssertTXNLsnOrder(rb);
+		}
+	}
+	else
+		txn = NULL;				/* not found and not asked to create */
+
+	/* update cache */
+	rb->by_txn_last_xid = xid;
+	rb->by_txn_last_txn = txn;
+
+	if (is_new)
+		*is_new = !found;
+
+	Assert(!create || txn != NULL);
+	return txn;
+}
+
+/*
+ * Record the partial change for the streaming of in-progress transactions.  We
+ * can stream only complete changes so if we have a partial change like toast
+ * table insert or speculative insert then we mark such a 'txn' so that it
+ * can't be streamed.  We also ensure that if the changes in such a 'txn' are
+ * above logical_decoding_work_mem threshold then we stream them as soon as we
+ * have a complete change.
+ */
+static void
+ReorderBufferProcessPartialChange(ReorderBuffer *rb, ReorderBufferTXN *txn,
+								  ReorderBufferChange *change,
+								  bool toast_insert)
+{
+	ReorderBufferTXN *toptxn;
+
+	/*
+	 * The partial changes need to be processed only while streaming
+	 * in-progress transactions.
+	 */
+	if (!ReorderBufferCanStream(rb))
+		return;
+
+	/* Get the top transaction. */
+	if (txn->toptxn != NULL)
+		toptxn = txn->toptxn;
+	else
+		toptxn = txn;
+
+	/*
+	 * Indicate a partial change for toast inserts.  The change will be
+	 * considered as complete once we get the insert or update on the main
+	 * table and we are sure that the pending toast chunks are not required
+	 * anymore.
+	 *
+	 * If we allow streaming when there are pending toast chunks then such
+	 * chunks won't be released till the insert (multi_insert) is complete and
+	 * we expect the txn to have streamed all changes after streaming.  This
+	 * restriction is mainly to ensure the correctness of streamed
+	 * transactions and it doesn't seem worth uplifting such a restriction
+	 * just to allow this case because anyway we will stream the transaction
+	 * once such an insert is complete.
+	 */
+	if (toast_insert)
+		toptxn->txn_flags |= RBTXN_HAS_PARTIAL_CHANGE;
+	else if (rbtxn_has_partial_change(toptxn) &&
+			 IsInsertOrUpdate(change->action) &&
+			 change->data.tp.clear_toast_afterwards)
+		toptxn->txn_flags &= ~RBTXN_HAS_PARTIAL_CHANGE;
+
+	/*
+	 * Indicate a partial change for speculative inserts.  The change will be
+	 * considered as complete once we get the speculative confirm or abort
+	 * token.
+	 */
+	if (IsSpecInsert(change->action))
+		toptxn->txn_flags |= RBTXN_HAS_PARTIAL_CHANGE;
+	else if (rbtxn_has_partial_change(toptxn) &&
+			 IsSpecConfirmOrAbort(change->action))
+		toptxn->txn_flags &= ~RBTXN_HAS_PARTIAL_CHANGE;
+
+	/*
+	 * Stream the transaction if it is serialized before and the changes are
+	 * now complete in the top-level transaction.
+	 *
+	 * The reason for doing the streaming of such a transaction as soon as we
+	 * get the complete change for it is that previously it would have reached
+	 * the memory threshold and wouldn't get streamed because of incomplete
+	 * changes.  Delaying such transactions would increase apply lag for them.
+	 */
+	if (ReorderBufferCanStartStreaming(rb) &&
+		!(rbtxn_has_partial_change(toptxn)) &&
+		rbtxn_is_serialized(txn))
+		ReorderBufferStreamTXN(rb, toptxn);
+}
+
+/*
+ * Queue a change into a transaction so it can be replayed upon commit or will be
+ * streamed when we reach logical_decoding_work_mem threshold.
+ */
+void
+ReorderBufferQueueChange(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn,
+						 ReorderBufferChange *change, bool toast_insert)
+{
+	ReorderBufferTXN *txn;
+
+	txn = ReorderBufferTXNByXid(rb, xid, true, NULL, lsn, true);
+
+	/*
+	 * While streaming the previous changes we have detected that the
+	 * transaction is aborted.  So there is no point in collecting further
+	 * changes for it.
+	 */
+	if (txn->concurrent_abort)
+	{
+		/*
+		 * We don't need to update memory accounting for this change as we
+		 * have not added it to the queue yet.
+		 */
+		ReorderBufferReturnChange(rb, change, false);
+		return;
+	}
+
+	change->lsn = lsn;
+	change->txn = txn;
+
+	Assert(InvalidXLogRecPtr != lsn);
+	dlist_push_tail(&txn->changes, &change->node);
+	txn->nentries++;
+	txn->nentries_mem++;
+
+	/* update memory accounting information */
+	ReorderBufferChangeMemoryUpdate(rb, change, true,
+									ReorderBufferChangeSize(change));
+
+	/* process partial change */
+	ReorderBufferProcessPartialChange(rb, txn, change, toast_insert);
+
+	/* check the memory limits and evict something if needed */
+	ReorderBufferCheckMemoryLimit(rb);
+}
+
+/*
+ * A transactional message is queued to be processed upon commit and a
+ * non-transactional message gets processed immediately.
+ */
+void
+ReorderBufferQueueMessage(ReorderBuffer *rb, TransactionId xid,
+						  Snapshot snapshot, XLogRecPtr lsn,
+						  bool transactional, const char *prefix,
+						  Size message_size, const char *message)
+{
+	if (transactional)
+	{
+		MemoryContext oldcontext;
+		ReorderBufferChange *change;
+
+		Assert(xid != InvalidTransactionId);
+
+		oldcontext = MemoryContextSwitchTo(rb->context);
+
+		change = ReorderBufferGetChange(rb);
+		change->action = REORDER_BUFFER_CHANGE_MESSAGE;
+		change->data.msg.prefix = pstrdup(prefix);
+		change->data.msg.message_size = message_size;
+		change->data.msg.message = palloc(message_size);
+		memcpy(change->data.msg.message, message, message_size);
+
+		ReorderBufferQueueChange(rb, xid, lsn, change, false);
+
+		MemoryContextSwitchTo(oldcontext);
+	}
+	else
+	{
+		ReorderBufferTXN *txn = NULL;
+		volatile Snapshot snapshot_now = snapshot;
+
+		if (xid != InvalidTransactionId)
+			txn = ReorderBufferTXNByXid(rb, xid, true, NULL, lsn, true);
+
+		/* setup snapshot to allow catalog access */
+		SetupHistoricSnapshot(snapshot_now, NULL);
+		PG_TRY();
+		{
+			rb->message(rb, txn, lsn, false, prefix, message_size, message);
+
+			TeardownHistoricSnapshot(false);
+		}
+		PG_CATCH();
+		{
+			TeardownHistoricSnapshot(true);
+			PG_RE_THROW();
+		}
+		PG_END_TRY();
+	}
+}
+
+/*
+ * AssertTXNLsnOrder
+ *		Verify LSN ordering of transaction lists in the reorderbuffer
+ *
+ * Other LSN-related invariants are checked too.
+ *
+ * No-op if assertions are not in use.
+ */
+static void
+AssertTXNLsnOrder(ReorderBuffer *rb)
+{
+#ifdef USE_ASSERT_CHECKING
+	dlist_iter	iter;
+	XLogRecPtr	prev_first_lsn = InvalidXLogRecPtr;
+	XLogRecPtr	prev_base_snap_lsn = InvalidXLogRecPtr;
+
+	dlist_foreach(iter, &rb->toplevel_by_lsn)
+	{
+		ReorderBufferTXN *cur_txn = dlist_container(ReorderBufferTXN, node,
+													iter.cur);
+
+		/* start LSN must be set */
+		Assert(cur_txn->first_lsn != InvalidXLogRecPtr);
+
+		/* If there is an end LSN, it must be higher than start LSN */
+		if (cur_txn->end_lsn != InvalidXLogRecPtr)
+			Assert(cur_txn->first_lsn <= cur_txn->end_lsn);
+
+		/* Current initial LSN must be strictly higher than previous */
+		if (prev_first_lsn != InvalidXLogRecPtr)
+			Assert(prev_first_lsn < cur_txn->first_lsn);
+
+		/* known-as-subtxn txns must not be listed */
+		Assert(!rbtxn_is_known_subxact(cur_txn));
+
+		prev_first_lsn = cur_txn->first_lsn;
+	}
+
+	dlist_foreach(iter, &rb->txns_by_base_snapshot_lsn)
+	{
+		ReorderBufferTXN *cur_txn = dlist_container(ReorderBufferTXN,
+													base_snapshot_node,
+													iter.cur);
+
+		/* base snapshot (and its LSN) must be set */
+		Assert(cur_txn->base_snapshot != NULL);
+		Assert(cur_txn->base_snapshot_lsn != InvalidXLogRecPtr);
+
+		/* current LSN must be strictly higher than previous */
+		if (prev_base_snap_lsn != InvalidXLogRecPtr)
+			Assert(prev_base_snap_lsn < cur_txn->base_snapshot_lsn);
+
+		/* known-as-subtxn txns must not be listed */
+		Assert(!rbtxn_is_known_subxact(cur_txn));
+
+		prev_base_snap_lsn = cur_txn->base_snapshot_lsn;
+	}
+#endif
+}
+
+/*
+ * AssertChangeLsnOrder
+ *
+ * Check ordering of changes in the (sub)transaction.
+ */
+static void
+AssertChangeLsnOrder(ReorderBufferTXN *txn)
+{
+#ifdef USE_ASSERT_CHECKING
+	dlist_iter	iter;
+	XLogRecPtr	prev_lsn = txn->first_lsn;
+
+	dlist_foreach(iter, &txn->changes)
+	{
+		ReorderBufferChange *cur_change;
+
+		cur_change = dlist_container(ReorderBufferChange, node, iter.cur);
+
+		Assert(txn->first_lsn != InvalidXLogRecPtr);
+		Assert(cur_change->lsn != InvalidXLogRecPtr);
+		Assert(txn->first_lsn <= cur_change->lsn);
+
+		if (txn->end_lsn != InvalidXLogRecPtr)
+			Assert(cur_change->lsn <= txn->end_lsn);
+
+		Assert(prev_lsn <= cur_change->lsn);
+
+		prev_lsn = cur_change->lsn;
+	}
+#endif
+}
+
+/*
+ * ReorderBufferGetOldestTXN
+ *		Return oldest transaction in reorderbuffer
+ */
+ReorderBufferTXN *
+ReorderBufferGetOldestTXN(ReorderBuffer *rb)
+{
+	ReorderBufferTXN *txn;
+
+	AssertTXNLsnOrder(rb);
+
+	if (dlist_is_empty(&rb->toplevel_by_lsn))
+		return NULL;
+
+	txn = dlist_head_element(ReorderBufferTXN, node, &rb->toplevel_by_lsn);
+
+	Assert(!rbtxn_is_known_subxact(txn));
+	Assert(txn->first_lsn != InvalidXLogRecPtr);
+	return txn;
+}
+
+/*
+ * ReorderBufferGetOldestXmin
+ *		Return oldest Xmin in reorderbuffer
+ *
+ * Returns oldest possibly running Xid from the point of view of snapshots
+ * used in the transactions kept by reorderbuffer, or InvalidTransactionId if
+ * there are none.
+ *
+ * Since snapshots are assigned monotonically, this equals the Xmin of the
+ * base snapshot with minimal base_snapshot_lsn.
+ */
+TransactionId
+ReorderBufferGetOldestXmin(ReorderBuffer *rb)
+{
+	ReorderBufferTXN *txn;
+
+	AssertTXNLsnOrder(rb);
+
+	if (dlist_is_empty(&rb->txns_by_base_snapshot_lsn))
+		return InvalidTransactionId;
+
+	txn = dlist_head_element(ReorderBufferTXN, base_snapshot_node,
+							 &rb->txns_by_base_snapshot_lsn);
+	return txn->base_snapshot->xmin;
+}
+
+void
+ReorderBufferSetRestartPoint(ReorderBuffer *rb, XLogRecPtr ptr)
+{
+	rb->current_restart_decoding_lsn = ptr;
+}
+
+/*
+ * ReorderBufferAssignChild
+ *
+ * Make note that we know that subxid is a subtransaction of xid, seen as of
+ * the given lsn.
+ */
+void
+ReorderBufferAssignChild(ReorderBuffer *rb, TransactionId xid,
+						 TransactionId subxid, XLogRecPtr lsn)
+{
+	ReorderBufferTXN *txn;
+	ReorderBufferTXN *subtxn;
+	bool		new_top;
+	bool		new_sub;
+
+	txn = ReorderBufferTXNByXid(rb, xid, true, &new_top, lsn, true);
+	subtxn = ReorderBufferTXNByXid(rb, subxid, true, &new_sub, lsn, false);
+
+	if (!new_sub)
+	{
+		if (rbtxn_is_known_subxact(subtxn))
+		{
+			/* already associated, nothing to do */
+			return;
+		}
+		else
+		{
+			/*
+			 * We already saw this transaction, but initially added it to the
+			 * list of top-level txns.  Now that we know it's not top-level,
+			 * remove it from there.
+			 */
+			dlist_delete(&subtxn->node);
+		}
+	}
+
+	subtxn->txn_flags |= RBTXN_IS_SUBXACT;
+	subtxn->toplevel_xid = xid;
+	Assert(subtxn->nsubtxns == 0);
+
+	/* set the reference to top-level transaction */
+	subtxn->toptxn = txn;
+
+	/* add to subtransaction list */
+	dlist_push_tail(&txn->subtxns, &subtxn->node);
+	txn->nsubtxns++;
+
+	/* Possibly transfer the subtxn's snapshot to its top-level txn. */
+	ReorderBufferTransferSnapToParent(txn, subtxn);
+
+	/* Verify LSN-ordering invariant */
+	AssertTXNLsnOrder(rb);
+}
+
+/*
+ * ReorderBufferTransferSnapToParent
+ *		Transfer base snapshot from subtxn to top-level txn, if needed
+ *
+ * This is done if the top-level txn doesn't have a base snapshot, or if the
+ * subtxn's base snapshot has an earlier LSN than the top-level txn's base
+ * snapshot's LSN.  This can happen if there are no changes in the toplevel
+ * txn but there are some in the subtxn, or the first change in subtxn has
+ * earlier LSN than first change in the top-level txn and we learned about
+ * their kinship only now.
+ *
+ * The subtransaction's snapshot is cleared regardless of the transfer
+ * happening, since it's not needed anymore in either case.
+ *
+ * We do this as soon as we become aware of their kinship, to avoid queueing
+ * extra snapshots to txns known-as-subtxns -- only top-level txns will
+ * receive further snapshots.
+ */
+static void
+ReorderBufferTransferSnapToParent(ReorderBufferTXN *txn,
+								  ReorderBufferTXN *subtxn)
+{
+	Assert(subtxn->toplevel_xid == txn->xid);
+
+	if (subtxn->base_snapshot != NULL)
+	{
+		if (txn->base_snapshot == NULL ||
+			subtxn->base_snapshot_lsn < txn->base_snapshot_lsn)
+		{
+			/*
+			 * If the toplevel transaction already has a base snapshot but
+			 * it's newer than the subxact's, purge it.
+			 */
+			if (txn->base_snapshot != NULL)
+			{
+				SnapBuildSnapDecRefcount(txn->base_snapshot);
+				dlist_delete(&txn->base_snapshot_node);
+			}
+
+			/*
+			 * The snapshot is now the top transaction's; transfer it, and
+			 * adjust the list position of the top transaction in the list by
+			 * moving it to where the subtransaction is.
+			 */
+			txn->base_snapshot = subtxn->base_snapshot;
+			txn->base_snapshot_lsn = subtxn->base_snapshot_lsn;
+			dlist_insert_before(&subtxn->base_snapshot_node,
+								&txn->base_snapshot_node);
+
+			/*
+			 * The subtransaction doesn't have a snapshot anymore (so it
+			 * mustn't be in the list.)
+			 */
+			subtxn->base_snapshot = NULL;
+			subtxn->base_snapshot_lsn = InvalidXLogRecPtr;
+			dlist_delete(&subtxn->base_snapshot_node);
+		}
+		else
+		{
+			/* Base snap of toplevel is fine, so subxact's is not needed */
+			SnapBuildSnapDecRefcount(subtxn->base_snapshot);
+			dlist_delete(&subtxn->base_snapshot_node);
+			subtxn->base_snapshot = NULL;
+			subtxn->base_snapshot_lsn = InvalidXLogRecPtr;
+		}
+	}
+}
+
+/*
+ * Associate a subtransaction with its toplevel transaction at commit
+ * time. There may be no further changes added after this.
+ */
+void
+ReorderBufferCommitChild(ReorderBuffer *rb, TransactionId xid,
+						 TransactionId subxid, XLogRecPtr commit_lsn,
+						 XLogRecPtr end_lsn)
+{
+	ReorderBufferTXN *subtxn;
+
+	subtxn = ReorderBufferTXNByXid(rb, subxid, false, NULL,
+								   InvalidXLogRecPtr, false);
+
+	/*
+	 * No need to do anything if that subtxn didn't contain any changes
+	 */
+	if (!subtxn)
+		return;
+
+	subtxn->final_lsn = commit_lsn;
+	subtxn->end_lsn = end_lsn;
+
+	/*
+	 * Assign this subxact as a child of the toplevel xact (no-op if already
+	 * done.)
+	 */
+	ReorderBufferAssignChild(rb, xid, subxid, InvalidXLogRecPtr);
+}
+
+
+/*
+ * Support for efficiently iterating over a transaction's and its
+ * subtransactions' changes.
+ *
+ * We do by doing a k-way merge between transactions/subtransactions. For that
+ * we model the current heads of the different transactions as a binary heap
+ * so we easily know which (sub-)transaction has the change with the smallest
+ * lsn next.
+ *
+ * We assume the changes in individual transactions are already sorted by LSN.
+ */
+
+/*
+ * Binary heap comparison function.
+ */
+static int
+ReorderBufferIterCompare(Datum a, Datum b, void *arg)
+{
+	ReorderBufferIterTXNState *state = (ReorderBufferIterTXNState *) arg;
+	XLogRecPtr	pos_a = state->entries[DatumGetInt32(a)].lsn;
+	XLogRecPtr	pos_b = state->entries[DatumGetInt32(b)].lsn;
+
+	if (pos_a < pos_b)
+		return 1;
+	else if (pos_a == pos_b)
+		return 0;
+	return -1;
+}
+
+/*
+ * Allocate & initialize an iterator which iterates in lsn order over a
+ * transaction and all its subtransactions.
+ *
+ * Note: The iterator state is returned through iter_state parameter rather
+ * than the function's return value.  This is because the state gets cleaned up
+ * in a PG_CATCH block in the caller, so we want to make sure the caller gets
+ * back the state even if this function throws an exception.
+ */
+static void
+ReorderBufferIterTXNInit(ReorderBuffer *rb, ReorderBufferTXN *txn,
+						 ReorderBufferIterTXNState *volatile *iter_state)
+{
+	Size		nr_txns = 0;
+	ReorderBufferIterTXNState *state;
+	dlist_iter	cur_txn_i;
+	int32		off;
+
+	*iter_state = NULL;
+
+	/* Check ordering of changes in the toplevel transaction. */
+	AssertChangeLsnOrder(txn);
+
+	/*
+	 * Calculate the size of our heap: one element for every transaction that
+	 * contains changes.  (Besides the transactions already in the reorder
+	 * buffer, we count the one we were directly passed.)
+	 */
+	if (txn->nentries > 0)
+		nr_txns++;
+
+	dlist_foreach(cur_txn_i, &txn->subtxns)
+	{
+		ReorderBufferTXN *cur_txn;
+
+		cur_txn = dlist_container(ReorderBufferTXN, node, cur_txn_i.cur);
+
+		/* Check ordering of changes in this subtransaction. */
+		AssertChangeLsnOrder(cur_txn);
+
+		if (cur_txn->nentries > 0)
+			nr_txns++;
+	}
+
+	/* allocate iteration state */
+	state = (ReorderBufferIterTXNState *)
+		MemoryContextAllocZero(rb->context,
+							   sizeof(ReorderBufferIterTXNState) +
+							   sizeof(ReorderBufferIterTXNEntry) * nr_txns);
+
+	state->nr_txns = nr_txns;
+	dlist_init(&state->old_change);
+
+	for (off = 0; off < state->nr_txns; off++)
+	{
+		state->entries[off].file.vfd = -1;
+		state->entries[off].segno = 0;
+	}
+
+	/* allocate heap */
+	state->heap = binaryheap_allocate(state->nr_txns,
+									  ReorderBufferIterCompare,
+									  state);
+
+	/* Now that the state fields are initialized, it is safe to return it. */
+	*iter_state = state;
+
+	/*
+	 * Now insert items into the binary heap, in an unordered fashion.  (We
+	 * will run a heap assembly step at the end; this is more efficient.)
+	 */
+
+	off = 0;
+
+	/* add toplevel transaction if it contains changes */
+	if (txn->nentries > 0)
+	{
+		ReorderBufferChange *cur_change;
+
+		if (rbtxn_is_serialized(txn))
+		{
+			/* serialize remaining changes */
+			ReorderBufferSerializeTXN(rb, txn);
+			ReorderBufferRestoreChanges(rb, txn, &state->entries[off].file,
+										&state->entries[off].segno);
+		}
+
+		cur_change = dlist_head_element(ReorderBufferChange, node,
+										&txn->changes);
+
+		state->entries[off].lsn = cur_change->lsn;
+		state->entries[off].change = cur_change;
+		state->entries[off].txn = txn;
+
+		binaryheap_add_unordered(state->heap, Int32GetDatum(off++));
+	}
+
+	/* add subtransactions if they contain changes */
+	dlist_foreach(cur_txn_i, &txn->subtxns)
+	{
+		ReorderBufferTXN *cur_txn;
+
+		cur_txn = dlist_container(ReorderBufferTXN, node, cur_txn_i.cur);
+
+		if (cur_txn->nentries > 0)
+		{
+			ReorderBufferChange *cur_change;
+
+			if (rbtxn_is_serialized(cur_txn))
+			{
+				/* serialize remaining changes */
+				ReorderBufferSerializeTXN(rb, cur_txn);
+				ReorderBufferRestoreChanges(rb, cur_txn,
+											&state->entries[off].file,
+											&state->entries[off].segno);
+			}
+			cur_change = dlist_head_element(ReorderBufferChange, node,
+											&cur_txn->changes);
+
+			state->entries[off].lsn = cur_change->lsn;
+			state->entries[off].change = cur_change;
+			state->entries[off].txn = cur_txn;
+
+			binaryheap_add_unordered(state->heap, Int32GetDatum(off++));
+		}
+	}
+
+	/* assemble a valid binary heap */
+	binaryheap_build(state->heap);
+}
+
+/*
+ * Return the next change when iterating over a transaction and its
+ * subtransactions.
+ *
+ * Returns NULL when no further changes exist.
+ */
+static ReorderBufferChange *
+ReorderBufferIterTXNNext(ReorderBuffer *rb, ReorderBufferIterTXNState *state)
+{
+	ReorderBufferChange *change;
+	ReorderBufferIterTXNEntry *entry;
+	int32		off;
+
+	/* nothing there anymore */
+	if (state->heap->bh_size == 0)
+		return NULL;
+
+	off = DatumGetInt32(binaryheap_first(state->heap));
+	entry = &state->entries[off];
+
+	/* free memory we might have "leaked" in the previous *Next call */
+	if (!dlist_is_empty(&state->old_change))
+	{
+		change = dlist_container(ReorderBufferChange, node,
+								 dlist_pop_head_node(&state->old_change));
+		ReorderBufferReturnChange(rb, change, true);
+		Assert(dlist_is_empty(&state->old_change));
+	}
+
+	change = entry->change;
+
+	/*
+	 * update heap with information about which transaction has the next
+	 * relevant change in LSN order
+	 */
+
+	/* there are in-memory changes */
+	if (dlist_has_next(&entry->txn->changes, &entry->change->node))
+	{
+		dlist_node *next = dlist_next_node(&entry->txn->changes, &change->node);
+		ReorderBufferChange *next_change =
+		dlist_container(ReorderBufferChange, node, next);
+
+		/* txn stays the same */
+		state->entries[off].lsn = next_change->lsn;
+		state->entries[off].change = next_change;
+
+		binaryheap_replace_first(state->heap, Int32GetDatum(off));
+		return change;
+	}
+
+	/* try to load changes from disk */
+	if (entry->txn->nentries != entry->txn->nentries_mem)
+	{
+		/*
+		 * Ugly: restoring changes will reuse *Change records, thus delete the
+		 * current one from the per-tx list and only free in the next call.
+		 */
+		dlist_delete(&change->node);
+		dlist_push_tail(&state->old_change, &change->node);
+
+		/*
+		 * Update the total bytes processed by the txn for which we are
+		 * releasing the current set of changes and restoring the new set of
+		 * changes.
+		 */
+		rb->totalBytes += entry->txn->size;
+		if (ReorderBufferRestoreChanges(rb, entry->txn, &entry->file,
+										&state->entries[off].segno))
+		{
+			/* successfully restored changes from disk */
+			ReorderBufferChange *next_change =
+			dlist_head_element(ReorderBufferChange, node,
+							   &entry->txn->changes);
+
+			elog(DEBUG2, "restored %u/%u changes from disk",
+				 (uint32) entry->txn->nentries_mem,
+				 (uint32) entry->txn->nentries);
+
+			Assert(entry->txn->nentries_mem);
+			/* txn stays the same */
+			state->entries[off].lsn = next_change->lsn;
+			state->entries[off].change = next_change;
+			binaryheap_replace_first(state->heap, Int32GetDatum(off));
+
+			return change;
+		}
+	}
+
+	/* ok, no changes there anymore, remove */
+	binaryheap_remove_first(state->heap);
+
+	return change;
+}
+
+/*
+ * Deallocate the iterator
+ */
+static void
+ReorderBufferIterTXNFinish(ReorderBuffer *rb,
+						   ReorderBufferIterTXNState *state)
+{
+	int32		off;
+
+	for (off = 0; off < state->nr_txns; off++)
+	{
+		if (state->entries[off].file.vfd != -1)
+			FileClose(state->entries[off].file.vfd);
+	}
+
+	/* free memory we might have "leaked" in the last *Next call */
+	if (!dlist_is_empty(&state->old_change))
+	{
+		ReorderBufferChange *change;
+
+		change = dlist_container(ReorderBufferChange, node,
+								 dlist_pop_head_node(&state->old_change));
+		ReorderBufferReturnChange(rb, change, true);
+		Assert(dlist_is_empty(&state->old_change));
+	}
+
+	binaryheap_free(state->heap);
+	pfree(state);
+}
+
+/*
+ * Cleanup the contents of a transaction, usually after the transaction
+ * committed or aborted.
+ */
+static void
+ReorderBufferCleanupTXN(ReorderBuffer *rb, ReorderBufferTXN *txn)
+{
+	bool		found;
+	dlist_mutable_iter iter;
+
+	/* cleanup subtransactions & their changes */
+	dlist_foreach_modify(iter, &txn->subtxns)
+	{
+		ReorderBufferTXN *subtxn;
+
+		subtxn = dlist_container(ReorderBufferTXN, node, iter.cur);
+
+		/*
+		 * Subtransactions are always associated to the toplevel TXN, even if
+		 * they originally were happening inside another subtxn, so we won't
+		 * ever recurse more than one level deep here.
+		 */
+		Assert(rbtxn_is_known_subxact(subtxn));
+		Assert(subtxn->nsubtxns == 0);
+
+		ReorderBufferCleanupTXN(rb, subtxn);
+	}
+
+	/* cleanup changes in the txn */
+	dlist_foreach_modify(iter, &txn->changes)
+	{
+		ReorderBufferChange *change;
+
+		change = dlist_container(ReorderBufferChange, node, iter.cur);
+
+		/* Check we're not mixing changes from different transactions. */
+		Assert(change->txn == txn);
+
+		ReorderBufferReturnChange(rb, change, true);
+	}
+
+	/*
+	 * Cleanup the tuplecids we stored for decoding catalog snapshot access.
+	 * They are always stored in the toplevel transaction.
+	 */
+	dlist_foreach_modify(iter, &txn->tuplecids)
+	{
+		ReorderBufferChange *change;
+
+		change = dlist_container(ReorderBufferChange, node, iter.cur);
+
+		/* Check we're not mixing changes from different transactions. */
+		Assert(change->txn == txn);
+		Assert(change->action == REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID);
+
+		ReorderBufferReturnChange(rb, change, true);
+	}
+
+	/*
+	 * Cleanup the base snapshot, if set.
+	 */
+	if (txn->base_snapshot != NULL)
+	{
+		SnapBuildSnapDecRefcount(txn->base_snapshot);
+		dlist_delete(&txn->base_snapshot_node);
+	}
+
+	/*
+	 * Cleanup the snapshot for the last streamed run.
+	 */
+	if (txn->snapshot_now != NULL)
+	{
+		Assert(rbtxn_is_streamed(txn));
+		ReorderBufferFreeSnap(rb, txn->snapshot_now);
+	}
+
+	/*
+	 * Remove TXN from its containing list.
+	 *
+	 * Note: if txn is known as subxact, we are deleting the TXN from its
+	 * parent's list of known subxacts; this leaves the parent's nsubxacts
+	 * count too high, but we don't care.  Otherwise, we are deleting the TXN
+	 * from the LSN-ordered list of toplevel TXNs.
+	 */
+	dlist_delete(&txn->node);
+
+	/* now remove reference from buffer */
+	hash_search(rb->by_txn,
+				(void *) &txn->xid,
+				HASH_REMOVE,
+				&found);
+	Assert(found);
+
+	/* remove entries spilled to disk */
+	if (rbtxn_is_serialized(txn))
+		ReorderBufferRestoreCleanup(rb, txn);
+
+	/* deallocate */
+	ReorderBufferReturnTXN(rb, txn);
+}
+
+/*
+ * Discard changes from a transaction (and subtransactions), either after
+ * streaming or decoding them at PREPARE. Keep the remaining info -
+ * transactions, tuplecids, invalidations and snapshots.
+ *
+ * We additionaly remove tuplecids after decoding the transaction at prepare
+ * time as we only need to perform invalidation at rollback or commit prepared.
+ *
+ * 'txn_prepared' indicates that we have decoded the transaction at prepare
+ * time.
+ */
+static void
+ReorderBufferTruncateTXN(ReorderBuffer *rb, ReorderBufferTXN *txn, bool txn_prepared)
+{
+	dlist_mutable_iter iter;
+
+	/* cleanup subtransactions & their changes */
+	dlist_foreach_modify(iter, &txn->subtxns)
+	{
+		ReorderBufferTXN *subtxn;
+
+		subtxn = dlist_container(ReorderBufferTXN, node, iter.cur);
+
+		/*
+		 * Subtransactions are always associated to the toplevel TXN, even if
+		 * they originally were happening inside another subtxn, so we won't
+		 * ever recurse more than one level deep here.
+		 */
+		Assert(rbtxn_is_known_subxact(subtxn));
+		Assert(subtxn->nsubtxns == 0);
+
+		ReorderBufferTruncateTXN(rb, subtxn, txn_prepared);
+	}
+
+	/* cleanup changes in the txn */
+	dlist_foreach_modify(iter, &txn->changes)
+	{
+		ReorderBufferChange *change;
+
+		change = dlist_container(ReorderBufferChange, node, iter.cur);
+
+		/* Check we're not mixing changes from different transactions. */
+		Assert(change->txn == txn);
+
+		/* remove the change from it's containing list */
+		dlist_delete(&change->node);
+
+		ReorderBufferReturnChange(rb, change, true);
+	}
+
+	/*
+	 * Mark the transaction as streamed.
+	 *
+	 * The toplevel transaction, identified by (toptxn==NULL), is marked as
+	 * streamed always, even if it does not contain any changes (that is, when
+	 * all the changes are in subtransactions).
+	 *
+	 * For subtransactions, we only mark them as streamed when there are
+	 * changes in them.
+	 *
+	 * We do it this way because of aborts - we don't want to send aborts for
+	 * XIDs the downstream is not aware of. And of course, it always knows
+	 * about the toplevel xact (we send the XID in all messages), but we never
+	 * stream XIDs of empty subxacts.
+	 */
+	if ((!txn_prepared) && ((!txn->toptxn) || (txn->nentries_mem != 0)))
+		txn->txn_flags |= RBTXN_IS_STREAMED;
+
+	if (txn_prepared)
+	{
+		/*
+		 * If this is a prepared txn, cleanup the tuplecids we stored for
+		 * decoding catalog snapshot access. They are always stored in the
+		 * toplevel transaction.
+		 */
+		dlist_foreach_modify(iter, &txn->tuplecids)
+		{
+			ReorderBufferChange *change;
+
+			change = dlist_container(ReorderBufferChange, node, iter.cur);
+
+			/* Check we're not mixing changes from different transactions. */
+			Assert(change->txn == txn);
+			Assert(change->action == REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID);
+
+			/* Remove the change from its containing list. */
+			dlist_delete(&change->node);
+
+			ReorderBufferReturnChange(rb, change, true);
+		}
+	}
+
+	/*
+	 * Destroy the (relfilenode, ctid) hashtable, so that we don't leak any
+	 * memory. We could also keep the hash table and update it with new ctid
+	 * values, but this seems simpler and good enough for now.
+	 */
+	if (txn->tuplecid_hash != NULL)
+	{
+		hash_destroy(txn->tuplecid_hash);
+		txn->tuplecid_hash = NULL;
+	}
+
+	/* If this txn is serialized then clean the disk space. */
+	if (rbtxn_is_serialized(txn))
+	{
+		ReorderBufferRestoreCleanup(rb, txn);
+		txn->txn_flags &= ~RBTXN_IS_SERIALIZED;
+
+		/*
+		 * We set this flag to indicate if the transaction is ever serialized.
+		 * We need this to accurately update the stats as otherwise the same
+		 * transaction can be counted as serialized multiple times.
+		 */
+		txn->txn_flags |= RBTXN_IS_SERIALIZED_CLEAR;
+	}
+
+	/* also reset the number of entries in the transaction */
+	txn->nentries_mem = 0;
+	txn->nentries = 0;
+}
+
+/*
+ * Build a hash with a (relfilenode, ctid) -> (cmin, cmax) mapping for use by
+ * HeapTupleSatisfiesHistoricMVCC.
+ */
+static void
+ReorderBufferBuildTupleCidHash(ReorderBuffer *rb, ReorderBufferTXN *txn)
+{
+	dlist_iter	iter;
+	HASHCTL		hash_ctl;
+
+	if (!rbtxn_has_catalog_changes(txn) || dlist_is_empty(&txn->tuplecids))
+		return;
+
+	hash_ctl.keysize = sizeof(ReorderBufferTupleCidKey);
+	hash_ctl.entrysize = sizeof(ReorderBufferTupleCidEnt);
+	hash_ctl.hcxt = rb->context;
+
+	/*
+	 * create the hash with the exact number of to-be-stored tuplecids from
+	 * the start
+	 */
+	txn->tuplecid_hash =
+		hash_create("ReorderBufferTupleCid", txn->ntuplecids, &hash_ctl,
+					HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
+
+	dlist_foreach(iter, &txn->tuplecids)
+	{
+		ReorderBufferTupleCidKey key;
+		ReorderBufferTupleCidEnt *ent;
+		bool		found;
+		ReorderBufferChange *change;
+
+		change = dlist_container(ReorderBufferChange, node, iter.cur);
+
+		Assert(change->action == REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID);
+
+		/* be careful about padding */
+		memset(&key, 0, sizeof(ReorderBufferTupleCidKey));
+
+		key.relnode = change->data.tuplecid.node;
+
+		ItemPointerCopy(&change->data.tuplecid.tid,
+						&key.tid);
+
+		ent = (ReorderBufferTupleCidEnt *)
+			hash_search(txn->tuplecid_hash,
+						(void *) &key,
+						HASH_ENTER,
+						&found);
+		if (!found)
+		{
+			ent->cmin = change->data.tuplecid.cmin;
+			ent->cmax = change->data.tuplecid.cmax;
+			ent->combocid = change->data.tuplecid.combocid;
+		}
+		else
+		{
+			/*
+			 * Maybe we already saw this tuple before in this transaction, but
+			 * if so it must have the same cmin.
+			 */
+			Assert(ent->cmin == change->data.tuplecid.cmin);
+
+			/*
+			 * cmax may be initially invalid, but once set it can only grow,
+			 * and never become invalid again.
+			 */
+			Assert((ent->cmax == InvalidCommandId) ||
+				   ((change->data.tuplecid.cmax != InvalidCommandId) &&
+					(change->data.tuplecid.cmax > ent->cmax)));
+			ent->cmax = change->data.tuplecid.cmax;
+		}
+	}
+}
+
+/*
+ * Copy a provided snapshot so we can modify it privately. This is needed so
+ * that catalog modifying transactions can look into intermediate catalog
+ * states.
+ */
+static Snapshot
+ReorderBufferCopySnap(ReorderBuffer *rb, Snapshot orig_snap,
+					  ReorderBufferTXN *txn, CommandId cid)
+{
+	Snapshot	snap;
+	dlist_iter	iter;
+	int			i = 0;
+	Size		size;
+
+	size = sizeof(SnapshotData) +
+		sizeof(TransactionId) * orig_snap->xcnt +
+		sizeof(TransactionId) * (txn->nsubtxns + 1);
+
+	snap = MemoryContextAllocZero(rb->context, size);
+	memcpy(snap, orig_snap, sizeof(SnapshotData));
+
+	snap->copied = true;
+	snap->active_count = 1;		/* mark as active so nobody frees it */
+	snap->regd_count = 0;
+	snap->xip = (TransactionId *) (snap + 1);
+
+	memcpy(snap->xip, orig_snap->xip, sizeof(TransactionId) * snap->xcnt);
+
+	/*
+	 * snap->subxip contains all txids that belong to our transaction which we
+	 * need to check via cmin/cmax. That's why we store the toplevel
+	 * transaction in there as well.
+	 */
+	snap->subxip = snap->xip + snap->xcnt;
+	snap->subxip[i++] = txn->xid;
+
+	/*
+	 * subxcnt isn't decreased when subtransactions abort, so count manually.
+	 * Since it's an upper boundary it is safe to use it for the allocation
+	 * above.
+	 */
+	snap->subxcnt = 1;
+
+	dlist_foreach(iter, &txn->subtxns)
+	{
+		ReorderBufferTXN *sub_txn;
+
+		sub_txn = dlist_container(ReorderBufferTXN, node, iter.cur);
+		snap->subxip[i++] = sub_txn->xid;
+		snap->subxcnt++;
+	}
+
+	/* sort so we can bsearch() later */
+	qsort(snap->subxip, snap->subxcnt, sizeof(TransactionId), xidComparator);
+
+	/* store the specified current CommandId */
+	snap->curcid = cid;
+
+	return snap;
+}
+
+/*
+ * Free a previously ReorderBufferCopySnap'ed snapshot
+ */
+static void
+ReorderBufferFreeSnap(ReorderBuffer *rb, Snapshot snap)
+{
+	if (snap->copied)
+		pfree(snap);
+	else
+		SnapBuildSnapDecRefcount(snap);
+}
+
+/*
+ * If the transaction was (partially) streamed, we need to prepare or commit
+ * it in a 'streamed' way.  That is, we first stream the remaining part of the
+ * transaction, and then invoke stream_prepare or stream_commit message as per
+ * the case.
+ */
+static void
+ReorderBufferStreamCommit(ReorderBuffer *rb, ReorderBufferTXN *txn)
+{
+	/* we should only call this for previously streamed transactions */
+	Assert(rbtxn_is_streamed(txn));
+
+	ReorderBufferStreamTXN(rb, txn);
+
+	if (rbtxn_prepared(txn))
+	{
+		/*
+		 * Note, we send stream prepare even if a concurrent abort is
+		 * detected. See DecodePrepare for more information.
+		 */
+		rb->stream_prepare(rb, txn, txn->final_lsn);
+
+		/*
+		 * This is a PREPARED transaction, part of a two-phase commit. The
+		 * full cleanup will happen as part of the COMMIT PREPAREDs, so now
+		 * just truncate txn by removing changes and tuple_cids.
+		 */
+		ReorderBufferTruncateTXN(rb, txn, true);
+		/* Reset the CheckXidAlive */
+		CheckXidAlive = InvalidTransactionId;
+	}
+	else
+	{
+		rb->stream_commit(rb, txn, txn->final_lsn);
+		ReorderBufferCleanupTXN(rb, txn);
+	}
+}
+
+/*
+ * Set xid to detect concurrent aborts.
+ *
+ * While streaming an in-progress transaction or decoding a prepared
+ * transaction there is a possibility that the (sub)transaction might get
+ * aborted concurrently.  In such case if the (sub)transaction has catalog
+ * update then we might decode the tuple using wrong catalog version.  For
+ * example, suppose there is one catalog tuple with (xmin: 500, xmax: 0).  Now,
+ * the transaction 501 updates the catalog tuple and after that we will have
+ * two tuples (xmin: 500, xmax: 501) and (xmin: 501, xmax: 0).  Now, if 501 is
+ * aborted and some other transaction say 502 updates the same catalog tuple
+ * then the first tuple will be changed to (xmin: 500, xmax: 502).  So, the
+ * problem is that when we try to decode the tuple inserted/updated in 501
+ * after the catalog update, we will see the catalog tuple with (xmin: 500,
+ * xmax: 502) as visible because it will consider that the tuple is deleted by
+ * xid 502 which is not visible to our snapshot.  And when we will try to
+ * decode with that catalog tuple, it can lead to a wrong result or a crash.
+ * So, it is necessary to detect concurrent aborts to allow streaming of
+ * in-progress transactions or decoding of prepared  transactions.
+ *
+ * For detecting the concurrent abort we set CheckXidAlive to the current
+ * (sub)transaction's xid for which this change belongs to.  And, during
+ * catalog scan we can check the status of the xid and if it is aborted we will
+ * report a specific error so that we can stop streaming current transaction
+ * and discard the already streamed changes on such an error.  We might have
+ * already streamed some of the changes for the aborted (sub)transaction, but
+ * that is fine because when we decode the abort we will stream abort message
+ * to truncate the changes in the subscriber. Similarly, for prepared
+ * transactions, we stop decoding if concurrent abort is detected and then
+ * rollback the changes when rollback prepared is encountered. See
+ * DecodePrepare.
+ */
+static inline void
+SetupCheckXidLive(TransactionId xid)
+{
+	/*
+	 * If the input transaction id is already set as a CheckXidAlive then
+	 * nothing to do.
+	 */
+	if (TransactionIdEquals(CheckXidAlive, xid))
+		return;
+
+	/*
+	 * setup CheckXidAlive if it's not committed yet.  We don't check if the
+	 * xid is aborted.  That will happen during catalog access.
+	 */
+	if (!TransactionIdDidCommit(xid))
+		CheckXidAlive = xid;
+	else
+		CheckXidAlive = InvalidTransactionId;
+}
+
+/*
+ * Helper function for ReorderBufferProcessTXN for applying change.
+ */
+static inline void
+ReorderBufferApplyChange(ReorderBuffer *rb, ReorderBufferTXN *txn,
+						 Relation relation, ReorderBufferChange *change,
+						 bool streaming)
+{
+	if (streaming)
+		rb->stream_change(rb, txn, relation, change);
+	else
+		rb->apply_change(rb, txn, relation, change);
+}
+
+/*
+ * Helper function for ReorderBufferProcessTXN for applying the truncate.
+ */
+static inline void
+ReorderBufferApplyTruncate(ReorderBuffer *rb, ReorderBufferTXN *txn,
+						   int nrelations, Relation *relations,
+						   ReorderBufferChange *change, bool streaming)
+{
+	if (streaming)
+		rb->stream_truncate(rb, txn, nrelations, relations, change);
+	else
+		rb->apply_truncate(rb, txn, nrelations, relations, change);
+}
+
+/*
+ * Helper function for ReorderBufferProcessTXN for applying the message.
+ */
+static inline void
+ReorderBufferApplyMessage(ReorderBuffer *rb, ReorderBufferTXN *txn,
+						  ReorderBufferChange *change, bool streaming)
+{
+	if (streaming)
+		rb->stream_message(rb, txn, change->lsn, true,
+						   change->data.msg.prefix,
+						   change->data.msg.message_size,
+						   change->data.msg.message);
+	else
+		rb->message(rb, txn, change->lsn, true,
+					change->data.msg.prefix,
+					change->data.msg.message_size,
+					change->data.msg.message);
+}
+
+/*
+ * Function to store the command id and snapshot at the end of the current
+ * stream so that we can reuse the same while sending the next stream.
+ */
+static inline void
+ReorderBufferSaveTXNSnapshot(ReorderBuffer *rb, ReorderBufferTXN *txn,
+							 Snapshot snapshot_now, CommandId command_id)
+{
+	txn->command_id = command_id;
+
+	/* Avoid copying if it's already copied. */
+	if (snapshot_now->copied)
+		txn->snapshot_now = snapshot_now;
+	else
+		txn->snapshot_now = ReorderBufferCopySnap(rb, snapshot_now,
+												  txn, command_id);
+}
+
+/*
+ * Helper function for ReorderBufferProcessTXN to handle the concurrent
+ * abort of the streaming transaction.  This resets the TXN such that it
+ * can be used to stream the remaining data of transaction being processed.
+ * This can happen when the subtransaction is aborted and we still want to
+ * continue processing the main or other subtransactions data.
+ */
+static void
+ReorderBufferResetTXN(ReorderBuffer *rb, ReorderBufferTXN *txn,
+					  Snapshot snapshot_now,
+					  CommandId command_id,
+					  XLogRecPtr last_lsn,
+					  ReorderBufferChange *specinsert)
+{
+	/* Discard the changes that we just streamed */
+	ReorderBufferTruncateTXN(rb, txn, rbtxn_prepared(txn));
+
+	/* Free all resources allocated for toast reconstruction */
+	ReorderBufferToastReset(rb, txn);
+
+	/* Return the spec insert change if it is not NULL */
+	if (specinsert != NULL)
+	{
+		ReorderBufferReturnChange(rb, specinsert, true);
+		specinsert = NULL;
+	}
+
+	/*
+	 * For the streaming case, stop the stream and remember the command ID and
+	 * snapshot for the streaming run.
+	 */
+	if (rbtxn_is_streamed(txn))
+	{
+		rb->stream_stop(rb, txn, last_lsn);
+		ReorderBufferSaveTXNSnapshot(rb, txn, snapshot_now, command_id);
+	}
+}
+
+/*
+ * Helper function for ReorderBufferReplay and ReorderBufferStreamTXN.
+ *
+ * Send data of a transaction (and its subtransactions) to the
+ * output plugin. We iterate over the top and subtransactions (using a k-way
+ * merge) and replay the changes in lsn order.
+ *
+ * If streaming is true then data will be sent using stream API.
+ *
+ * Note: "volatile" markers on some parameters are to avoid trouble with
+ * PG_TRY inside the function.
+ */
+static void
+ReorderBufferProcessTXN(ReorderBuffer *rb, ReorderBufferTXN *txn,
+						XLogRecPtr commit_lsn,
+						volatile Snapshot snapshot_now,
+						volatile CommandId command_id,
+						bool streaming)
+{
+	bool		using_subtxn;
+	MemoryContext ccxt = CurrentMemoryContext;
+	ReorderBufferIterTXNState *volatile iterstate = NULL;
+	volatile XLogRecPtr prev_lsn = InvalidXLogRecPtr;
+	ReorderBufferChange *volatile specinsert = NULL;
+	volatile bool stream_started = false;
+	ReorderBufferTXN *volatile curtxn = NULL;
+
+	/* build data to be able to lookup the CommandIds of catalog tuples */
+	ReorderBufferBuildTupleCidHash(rb, txn);
+
+	/* setup the initial snapshot */
+	SetupHistoricSnapshot(snapshot_now, txn->tuplecid_hash);
+
+	/*
+	 * Decoding needs access to syscaches et al., which in turn use
+	 * heavyweight locks and such. Thus we need to have enough state around to
+	 * keep track of those.  The easiest way is to simply use a transaction
+	 * internally.  That also allows us to easily enforce that nothing writes
+	 * to the database by checking for xid assignments.
+	 *
+	 * When we're called via the SQL SRF there's already a transaction
+	 * started, so start an explicit subtransaction there.
+	 */
+	using_subtxn = IsTransactionOrTransactionBlock();
+
+	PG_TRY();
+	{
+		ReorderBufferChange *change;
+
+		if (using_subtxn)
+			BeginInternalSubTransaction(streaming ? "stream" : "replay");
+		else
+			StartTransactionCommand();
+
+		/*
+		 * We only need to send begin/begin-prepare for non-streamed
+		 * transactions.
+		 */
+		if (!streaming)
+		{
+			if (rbtxn_prepared(txn))
+				rb->begin_prepare(rb, txn);
+			else
+				rb->begin(rb, txn);
+		}
+
+		ReorderBufferIterTXNInit(rb, txn, &iterstate);
+		while ((change = ReorderBufferIterTXNNext(rb, iterstate)) != NULL)
+		{
+			Relation	relation = NULL;
+			Oid			reloid;
+
+			/*
+			 * We can't call start stream callback before processing first
+			 * change.
+			 */
+			if (prev_lsn == InvalidXLogRecPtr)
+			{
+				if (streaming)
+				{
+					txn->origin_id = change->origin_id;
+					rb->stream_start(rb, txn, change->lsn);
+					stream_started = true;
+				}
+			}
+
+			/*
+			 * Enforce correct ordering of changes, merged from multiple
+			 * subtransactions. The changes may have the same LSN due to
+			 * MULTI_INSERT xlog records.
+			 */
+			Assert(prev_lsn == InvalidXLogRecPtr || prev_lsn <= change->lsn);
+
+			prev_lsn = change->lsn;
+
+			/*
+			 * Set the current xid to detect concurrent aborts. This is
+			 * required for the cases when we decode the changes before the
+			 * COMMIT record is processed.
+			 */
+			if (streaming || rbtxn_prepared(change->txn))
+			{
+				curtxn = change->txn;
+				SetupCheckXidLive(curtxn->xid);
+			}
+
+			switch (change->action)
+			{
+				case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM:
+
+					/*
+					 * Confirmation for speculative insertion arrived. Simply
+					 * use as a normal record. It'll be cleaned up at the end
+					 * of INSERT processing.
+					 */
+					if (specinsert == NULL)
+						elog(ERROR, "invalid ordering of speculative insertion changes");
+					Assert(specinsert->data.tp.oldtuple == NULL);
+					change = specinsert;
+					change->action = REORDER_BUFFER_CHANGE_INSERT;
+
+					/* intentionally fall through */
+				case REORDER_BUFFER_CHANGE_INSERT:
+				case REORDER_BUFFER_CHANGE_UPDATE:
+				case REORDER_BUFFER_CHANGE_DELETE:
+					Assert(snapshot_now);
+
+					reloid = RelidByRelfilenode(change->data.tp.relnode.spcNode,
+												change->data.tp.relnode.relNode);
+
+					/*
+					 * Mapped catalog tuple without data, emitted while
+					 * catalog table was in the process of being rewritten. We
+					 * can fail to look up the relfilenode, because the
+					 * relmapper has no "historic" view, in contrast to the
+					 * normal catalog during decoding. Thus repeated rewrites
+					 * can cause a lookup failure. That's OK because we do not
+					 * decode catalog changes anyway. Normally such tuples
+					 * would be skipped over below, but we can't identify
+					 * whether the table should be logically logged without
+					 * mapping the relfilenode to the oid.
+					 */
+					if (reloid == InvalidOid &&
+						change->data.tp.newtuple == NULL &&
+						change->data.tp.oldtuple == NULL)
+						goto change_done;
+					else if (reloid == InvalidOid)
+						elog(ERROR, "could not map filenode \"%s\" to relation OID",
+							 relpathperm(change->data.tp.relnode,
+										 MAIN_FORKNUM));
+
+					relation = RelationIdGetRelation(reloid);
+
+					if (!RelationIsValid(relation))
+						elog(ERROR, "could not open relation with OID %u (for filenode \"%s\")",
+							 reloid,
+							 relpathperm(change->data.tp.relnode,
+										 MAIN_FORKNUM));
+
+					if (!RelationIsLogicallyLogged(relation))
+						goto change_done;
+
+					/*
+					 * Ignore temporary heaps created during DDL unless the
+					 * plugin has asked for them.
+					 */
+					if (relation->rd_rel->relrewrite && !rb->output_rewrites)
+						goto change_done;
+
+					/*
+					 * For now ignore sequence changes entirely. Most of the
+					 * time they don't log changes using records we
+					 * understand, so it doesn't make sense to handle the few
+					 * cases we do.
+					 */
+					if (relation->rd_rel->relkind == RELKIND_SEQUENCE)
+						goto change_done;
+
+					/* user-triggered change */
+					if (!IsToastRelation(relation))
+					{
+						ReorderBufferToastReplace(rb, txn, relation, change);
+						ReorderBufferApplyChange(rb, txn, relation, change,
+												 streaming);
+
+						/*
+						 * Only clear reassembled toast chunks if we're sure
+						 * they're not required anymore. The creator of the
+						 * tuple tells us.
+						 */
+						if (change->data.tp.clear_toast_afterwards)
+							ReorderBufferToastReset(rb, txn);
+					}
+					/* we're not interested in toast deletions */
+					else if (change->action == REORDER_BUFFER_CHANGE_INSERT)
+					{
+						/*
+						 * Need to reassemble the full toasted Datum in
+						 * memory, to ensure the chunks don't get reused till
+						 * we're done remove it from the list of this
+						 * transaction's changes. Otherwise it will get
+						 * freed/reused while restoring spooled data from
+						 * disk.
+						 */
+						Assert(change->data.tp.newtuple != NULL);
+
+						dlist_delete(&change->node);
+						ReorderBufferToastAppendChunk(rb, txn, relation,
+													  change);
+					}
+
+			change_done:
+
+					/*
+					 * If speculative insertion was confirmed, the record
+					 * isn't needed anymore.
+					 */
+					if (specinsert != NULL)
+					{
+						ReorderBufferReturnChange(rb, specinsert, true);
+						specinsert = NULL;
+					}
+
+					if (RelationIsValid(relation))
+					{
+						RelationClose(relation);
+						relation = NULL;
+					}
+					break;
+
+				case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_INSERT:
+
+					/*
+					 * Speculative insertions are dealt with by delaying the
+					 * processing of the insert until the confirmation record
+					 * arrives. For that we simply unlink the record from the
+					 * chain, so it does not get freed/reused while restoring
+					 * spooled data from disk.
+					 *
+					 * This is safe in the face of concurrent catalog changes
+					 * because the relevant relation can't be changed between
+					 * speculative insertion and confirmation due to
+					 * CheckTableNotInUse() and locking.
+					 */
+
+					/* clear out a pending (and thus failed) speculation */
+					if (specinsert != NULL)
+					{
+						ReorderBufferReturnChange(rb, specinsert, true);
+						specinsert = NULL;
+					}
+
+					/* and memorize the pending insertion */
+					dlist_delete(&change->node);
+					specinsert = change;
+					break;
+
+				case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_ABORT:
+
+					/*
+					 * Abort for speculative insertion arrived. So cleanup the
+					 * specinsert tuple and toast hash.
+					 *
+					 * Note that we get the spec abort change for each toast
+					 * entry but we need to perform the cleanup only the first
+					 * time we get it for the main table.
+					 */
+					if (specinsert != NULL)
+					{
+						/*
+						 * We must clean the toast hash before processing a
+						 * completely new tuple to avoid confusion about the
+						 * previous tuple's toast chunks.
+						 */
+						Assert(change->data.tp.clear_toast_afterwards);
+						ReorderBufferToastReset(rb, txn);
+
+						/* We don't need this record anymore. */
+						ReorderBufferReturnChange(rb, specinsert, true);
+						specinsert = NULL;
+					}
+					break;
+
+				case REORDER_BUFFER_CHANGE_TRUNCATE:
+					{
+						int			i;
+						int			nrelids = change->data.truncate.nrelids;
+						int			nrelations = 0;
+						Relation   *relations;
+
+						relations = palloc0(nrelids * sizeof(Relation));
+						for (i = 0; i < nrelids; i++)
+						{
+							Oid			relid = change->data.truncate.relids[i];
+							Relation	relation;
+
+							relation = RelationIdGetRelation(relid);
+
+							if (!RelationIsValid(relation))
+								elog(ERROR, "could not open relation with OID %u", relid);
+
+							if (!RelationIsLogicallyLogged(relation))
+								continue;
+
+							relations[nrelations++] = relation;
+						}
+
+						/* Apply the truncate. */
+						ReorderBufferApplyTruncate(rb, txn, nrelations,
+												   relations, change,
+												   streaming);
+
+						for (i = 0; i < nrelations; i++)
+							RelationClose(relations[i]);
+
+						break;
+					}
+
+				case REORDER_BUFFER_CHANGE_MESSAGE:
+					ReorderBufferApplyMessage(rb, txn, change, streaming);
+					break;
+
+				case REORDER_BUFFER_CHANGE_INVALIDATION:
+					/* Execute the invalidation messages locally */
+					ReorderBufferExecuteInvalidations(
+													  change->data.inval.ninvalidations,
+													  change->data.inval.invalidations);
+					break;
+
+				case REORDER_BUFFER_CHANGE_INTERNAL_SNAPSHOT:
+					/* get rid of the old */
+					TeardownHistoricSnapshot(false);
+
+					if (snapshot_now->copied)
+					{
+						ReorderBufferFreeSnap(rb, snapshot_now);
+						snapshot_now =
+							ReorderBufferCopySnap(rb, change->data.snapshot,
+												  txn, command_id);
+					}
+
+					/*
+					 * Restored from disk, need to be careful not to double
+					 * free. We could introduce refcounting for that, but for
+					 * now this seems infrequent enough not to care.
+					 */
+					else if (change->data.snapshot->copied)
+					{
+						snapshot_now =
+							ReorderBufferCopySnap(rb, change->data.snapshot,
+												  txn, command_id);
+					}
+					else
+					{
+						snapshot_now = change->data.snapshot;
+					}
+
+					/* and continue with the new one */
+					SetupHistoricSnapshot(snapshot_now, txn->tuplecid_hash);
+					break;
+
+				case REORDER_BUFFER_CHANGE_INTERNAL_COMMAND_ID:
+					Assert(change->data.command_id != InvalidCommandId);
+
+					if (command_id < change->data.command_id)
+					{
+						command_id = change->data.command_id;
+
+						if (!snapshot_now->copied)
+						{
+							/* we don't use the global one anymore */
+							snapshot_now = ReorderBufferCopySnap(rb, snapshot_now,
+																 txn, command_id);
+						}
+
+						snapshot_now->curcid = command_id;
+
+						TeardownHistoricSnapshot(false);
+						SetupHistoricSnapshot(snapshot_now, txn->tuplecid_hash);
+					}
+
+					break;
+
+				case REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID:
+					elog(ERROR, "tuplecid value in changequeue");
+					break;
+			}
+		}
+
+		/* speculative insertion record must be freed by now */
+		Assert(!specinsert);
+
+		/* clean up the iterator */
+		ReorderBufferIterTXNFinish(rb, iterstate);
+		iterstate = NULL;
+
+		/*
+		 * Update total transaction count and total bytes processed by the
+		 * transaction and its subtransactions. Ensure to not count the
+		 * streamed transaction multiple times.
+		 *
+		 * Note that the statistics computation has to be done after
+		 * ReorderBufferIterTXNFinish as it releases the serialized change
+		 * which we have already accounted in ReorderBufferIterTXNNext.
+		 */
+		if (!rbtxn_is_streamed(txn))
+			rb->totalTxns++;
+
+		rb->totalBytes += txn->total_size;
+
+		/*
+		 * Done with current changes, send the last message for this set of
+		 * changes depending upon streaming mode.
+		 */
+		if (streaming)
+		{
+			if (stream_started)
+			{
+				rb->stream_stop(rb, txn, prev_lsn);
+				stream_started = false;
+			}
+		}
+		else
+		{
+			/*
+			 * Call either PREPARE (for two-phase transactions) or COMMIT (for
+			 * regular ones).
+			 */
+			if (rbtxn_prepared(txn))
+				rb->prepare(rb, txn, commit_lsn);
+			else
+				rb->commit(rb, txn, commit_lsn);
+		}
+
+		/* this is just a sanity check against bad output plugin behaviour */
+		if (GetCurrentTransactionIdIfAny() != InvalidTransactionId)
+			elog(ERROR, "output plugin used XID %u",
+				 GetCurrentTransactionId());
+
+		/*
+		 * Remember the command ID and snapshot for the next set of changes in
+		 * streaming mode.
+		 */
+		if (streaming)
+			ReorderBufferSaveTXNSnapshot(rb, txn, snapshot_now, command_id);
+		else if (snapshot_now->copied)
+			ReorderBufferFreeSnap(rb, snapshot_now);
+
+		/* cleanup */
+		TeardownHistoricSnapshot(false);
+
+		/*
+		 * Aborting the current (sub-)transaction as a whole has the right
+		 * semantics. We want all locks acquired in here to be released, not
+		 * reassigned to the parent and we do not want any database access
+		 * have persistent effects.
+		 */
+		AbortCurrentTransaction();
+
+		/* make sure there's no cache pollution */
+		ReorderBufferExecuteInvalidations(txn->ninvalidations, txn->invalidations);
+
+		if (using_subtxn)
+			RollbackAndReleaseCurrentSubTransaction();
+
+		/*
+		 * We are here due to one of the four reasons: 1. Decoding an
+		 * in-progress txn. 2. Decoding a prepared txn. 3. Decoding of a
+		 * prepared txn that was (partially) streamed. 4. Decoding a committed
+		 * txn.
+		 *
+		 * For 1, we allow truncation of txn data by removing the changes
+		 * already streamed but still keeping other things like invalidations,
+		 * snapshot, and tuplecids. For 2 and 3, we indicate
+		 * ReorderBufferTruncateTXN to do more elaborate truncation of txn
+		 * data as the entire transaction has been decoded except for commit.
+		 * For 4, as the entire txn has been decoded, we can fully clean up
+		 * the TXN reorder buffer.
+		 */
+		if (streaming || rbtxn_prepared(txn))
+		{
+			ReorderBufferTruncateTXN(rb, txn, rbtxn_prepared(txn));
+			/* Reset the CheckXidAlive */
+			CheckXidAlive = InvalidTransactionId;
+		}
+		else
+			ReorderBufferCleanupTXN(rb, txn);
+	}
+	PG_CATCH();
+	{
+		MemoryContext ecxt = MemoryContextSwitchTo(ccxt);
+		ErrorData  *errdata = CopyErrorData();
+
+		/* TODO: Encapsulate cleanup from the PG_TRY and PG_CATCH blocks */
+		if (iterstate)
+			ReorderBufferIterTXNFinish(rb, iterstate);
+
+		TeardownHistoricSnapshot(true);
+
+		/*
+		 * Force cache invalidation to happen outside of a valid transaction
+		 * to prevent catalog access as we just caught an error.
+		 */
+		AbortCurrentTransaction();
+
+		/* make sure there's no cache pollution */
+		ReorderBufferExecuteInvalidations(txn->ninvalidations,
+										  txn->invalidations);
+
+		if (using_subtxn)
+			RollbackAndReleaseCurrentSubTransaction();
+
+		/*
+		 * The error code ERRCODE_TRANSACTION_ROLLBACK indicates a concurrent
+		 * abort of the (sub)transaction we are streaming or preparing. We
+		 * need to do the cleanup and return gracefully on this error, see
+		 * SetupCheckXidLive.
+		 *
+		 * This error code can be thrown by one of the callbacks we call
+		 * during decoding so we need to ensure that we return gracefully only
+		 * when we are sending the data in streaming mode and the streaming is
+		 * not finished yet or when we are sending the data out on a PREPARE
+		 * during a two-phase commit.
+		 */
+		if (errdata->sqlerrcode == ERRCODE_TRANSACTION_ROLLBACK &&
+			(stream_started || rbtxn_prepared(txn)))
+		{
+			/* curtxn must be set for streaming or prepared transactions */
+			Assert(curtxn);
+
+			/* Cleanup the temporary error state. */
+			FlushErrorState();
+			FreeErrorData(errdata);
+			errdata = NULL;
+			curtxn->concurrent_abort = true;
+
+			/* Reset the TXN so that it is allowed to stream remaining data. */
+			ReorderBufferResetTXN(rb, txn, snapshot_now,
+								  command_id, prev_lsn,
+								  specinsert);
+		}
+		else
+		{
+			ReorderBufferCleanupTXN(rb, txn);
+			MemoryContextSwitchTo(ecxt);
+			PG_RE_THROW();
+		}
+	}
+	PG_END_TRY();
+}
+
+/*
+ * Perform the replay of a transaction and its non-aborted subtransactions.
+ *
+ * Subtransactions previously have to be processed by
+ * ReorderBufferCommitChild(), even if previously assigned to the toplevel
+ * transaction with ReorderBufferAssignChild.
+ *
+ * This interface is called once a prepare or toplevel commit is read for both
+ * streamed as well as non-streamed transactions.
+ */
+static void
+ReorderBufferReplay(ReorderBufferTXN *txn,
+					ReorderBuffer *rb, TransactionId xid,
+					XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
+					TimestampTz commit_time,
+					RepOriginId origin_id, XLogRecPtr origin_lsn)
+{
+	Snapshot	snapshot_now;
+	CommandId	command_id = FirstCommandId;
+
+	txn->final_lsn = commit_lsn;
+	txn->end_lsn = end_lsn;
+	txn->commit_time = commit_time;
+	txn->origin_id = origin_id;
+	txn->origin_lsn = origin_lsn;
+
+	/*
+	 * If the transaction was (partially) streamed, we need to commit it in a
+	 * 'streamed' way. That is, we first stream the remaining part of the
+	 * transaction, and then invoke stream_commit message.
+	 *
+	 * Called after everything (origin ID, LSN, ...) is stored in the
+	 * transaction to avoid passing that information directly.
+	 */
+	if (rbtxn_is_streamed(txn))
+	{
+		ReorderBufferStreamCommit(rb, txn);
+		return;
+	}
+
+	/*
+	 * If this transaction has no snapshot, it didn't make any changes to the
+	 * database, so there's nothing to decode.  Note that
+	 * ReorderBufferCommitChild will have transferred any snapshots from
+	 * subtransactions if there were any.
+	 */
+	if (txn->base_snapshot == NULL)
+	{
+		Assert(txn->ninvalidations == 0);
+
+		/*
+		 * Removing this txn before a commit might result in the computation
+		 * of an incorrect restart_lsn. See SnapBuildProcessRunningXacts.
+		 */
+		if (!rbtxn_prepared(txn))
+			ReorderBufferCleanupTXN(rb, txn);
+		return;
+	}
+
+	snapshot_now = txn->base_snapshot;
+
+	/* Process and send the changes to output plugin. */
+	ReorderBufferProcessTXN(rb, txn, commit_lsn, snapshot_now,
+							command_id, false);
+}
+
+/*
+ * Commit a transaction.
+ *
+ * See comments for ReorderBufferReplay().
+ */
+void
+ReorderBufferCommit(ReorderBuffer *rb, TransactionId xid,
+					XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
+					TimestampTz commit_time,
+					RepOriginId origin_id, XLogRecPtr origin_lsn)
+{
+	ReorderBufferTXN *txn;
+
+	txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr,
+								false);
+
+	/* unknown transaction, nothing to replay */
+	if (txn == NULL)
+		return;
+
+	ReorderBufferReplay(txn, rb, xid, commit_lsn, end_lsn, commit_time,
+						origin_id, origin_lsn);
+}
+
+/*
+ * Record the prepare information for a transaction.
+ */
+bool
+ReorderBufferRememberPrepareInfo(ReorderBuffer *rb, TransactionId xid,
+								 XLogRecPtr prepare_lsn, XLogRecPtr end_lsn,
+								 TimestampTz prepare_time,
+								 RepOriginId origin_id, XLogRecPtr origin_lsn)
+{
+	ReorderBufferTXN *txn;
+
+	txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr, false);
+
+	/* unknown transaction, nothing to do */
+	if (txn == NULL)
+		return false;
+
+	/*
+	 * Remember the prepare information to be later used by commit prepared in
+	 * case we skip doing prepare.
+	 */
+	txn->final_lsn = prepare_lsn;
+	txn->end_lsn = end_lsn;
+	txn->commit_time = prepare_time;
+	txn->origin_id = origin_id;
+	txn->origin_lsn = origin_lsn;
+
+	return true;
+}
+
+/* Remember that we have skipped prepare */
+void
+ReorderBufferSkipPrepare(ReorderBuffer *rb, TransactionId xid)
+{
+	ReorderBufferTXN *txn;
+
+	txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr, false);
+
+	/* unknown transaction, nothing to do */
+	if (txn == NULL)
+		return;
+
+	txn->txn_flags |= RBTXN_SKIPPED_PREPARE;
+}
+
+/*
+ * Prepare a two-phase transaction.
+ *
+ * See comments for ReorderBufferReplay().
+ */
+void
+ReorderBufferPrepare(ReorderBuffer *rb, TransactionId xid,
+					 char *gid)
+{
+	ReorderBufferTXN *txn;
+
+	txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr,
+								false);
+
+	/* unknown transaction, nothing to replay */
+	if (txn == NULL)
+		return;
+
+	txn->txn_flags |= RBTXN_PREPARE;
+	txn->gid = pstrdup(gid);
+
+	/* The prepare info must have been updated in txn by now. */
+	Assert(txn->final_lsn != InvalidXLogRecPtr);
+
+	ReorderBufferReplay(txn, rb, xid, txn->final_lsn, txn->end_lsn,
+						txn->commit_time, txn->origin_id, txn->origin_lsn);
+
+	/*
+	 * We send the prepare for the concurrently aborted xacts so that later
+	 * when rollback prepared is decoded and sent, the downstream should be
+	 * able to rollback such a xact. See comments atop DecodePrepare.
+	 *
+	 * Note, for the concurrent_abort + streaming case a stream_prepare was
+	 * already sent within the ReorderBufferReplay call above.
+	 */
+	if (txn->concurrent_abort && !rbtxn_is_streamed(txn))
+		rb->prepare(rb, txn, txn->final_lsn);
+}
+
+/*
+ * This is used to handle COMMIT/ROLLBACK PREPARED.
+ */
+void
+ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
+							XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
+							XLogRecPtr initial_consistent_point,
+							TimestampTz commit_time, RepOriginId origin_id,
+							XLogRecPtr origin_lsn, char *gid, bool is_commit)
+{
+	ReorderBufferTXN *txn;
+	XLogRecPtr	prepare_end_lsn;
+	TimestampTz prepare_time;
+
+	txn = ReorderBufferTXNByXid(rb, xid, false, NULL, commit_lsn, false);
+
+	/* unknown transaction, nothing to do */
+	if (txn == NULL)
+		return;
+
+	/*
+	 * By this time the txn has the prepare record information, remember it to
+	 * be later used for rollback.
+	 */
+	prepare_end_lsn = txn->end_lsn;
+	prepare_time = txn->commit_time;
+
+	/* add the gid in the txn */
+	txn->gid = pstrdup(gid);
+
+	/*
+	 * It is possible that this transaction is not decoded at prepare time
+	 * either because by that time we didn't have a consistent snapshot or it
+	 * was decoded earlier but we have restarted. We only need to send the
+	 * prepare if it was not decoded earlier. We don't need to decode the xact
+	 * for aborts if it is not done already.
+	 */
+	if ((txn->final_lsn < initial_consistent_point) && is_commit)
+	{
+		txn->txn_flags |= RBTXN_PREPARE;
+
+		/*
+		 * The prepare info must have been updated in txn even if we skip
+		 * prepare.
+		 */
+		Assert(txn->final_lsn != InvalidXLogRecPtr);
+
+		/*
+		 * By this time the txn has the prepare record information and it is
+		 * important to use that so that downstream gets the accurate
+		 * information. If instead, we have passed commit information here
+		 * then downstream can behave as it has already replayed commit
+		 * prepared after the restart.
+		 */
+		ReorderBufferReplay(txn, rb, xid, txn->final_lsn, txn->end_lsn,
+							txn->commit_time, txn->origin_id, txn->origin_lsn);
+	}
+
+	txn->final_lsn = commit_lsn;
+	txn->end_lsn = end_lsn;
+	txn->commit_time = commit_time;
+	txn->origin_id = origin_id;
+	txn->origin_lsn = origin_lsn;
+
+	if (is_commit)
+		rb->commit_prepared(rb, txn, commit_lsn);
+	else
+		rb->rollback_prepared(rb, txn, prepare_end_lsn, prepare_time);
+
+	/* cleanup: make sure there's no cache pollution */
+	ReorderBufferExecuteInvalidations(txn->ninvalidations,
+									  txn->invalidations);
+	ReorderBufferCleanupTXN(rb, txn);
+}
+
+/*
+ * Abort a transaction that possibly has previous changes. Needs to be first
+ * called for subtransactions and then for the toplevel xid.
+ *
+ * NB: Transactions handled here have to have actively aborted (i.e. have
+ * produced an abort record). Implicitly aborted transactions are handled via
+ * ReorderBufferAbortOld(); transactions we're just not interested in, but
+ * which have committed are handled in ReorderBufferForget().
+ *
+ * This function purges this transaction and its contents from memory and
+ * disk.
+ */
+void
+ReorderBufferAbort(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn)
+{
+	ReorderBufferTXN *txn;
+
+	txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr,
+								false);
+
+	/* unknown, nothing to remove */
+	if (txn == NULL)
+		return;
+
+	/* For streamed transactions notify the remote node about the abort. */
+	if (rbtxn_is_streamed(txn))
+	{
+		rb->stream_abort(rb, txn, lsn);
+
+		/*
+		 * We might have decoded changes for this transaction that could load
+		 * the cache as per the current transaction's view (consider DDL's
+		 * happened in this transaction). We don't want the decoding of future
+		 * transactions to use those cache entries so execute invalidations.
+		 */
+		if (txn->ninvalidations > 0)
+			ReorderBufferImmediateInvalidation(rb, txn->ninvalidations,
+											   txn->invalidations);
+	}
+
+	/* cosmetic... */
+	txn->final_lsn = lsn;
+
+	/* remove potential on-disk data, and deallocate */
+	ReorderBufferCleanupTXN(rb, txn);
+}
+
+/*
+ * Abort all transactions that aren't actually running anymore because the
+ * server restarted.
+ *
+ * NB: These really have to be transactions that have aborted due to a server
+ * crash/immediate restart, as we don't deal with invalidations here.
+ */
+void
+ReorderBufferAbortOld(ReorderBuffer *rb, TransactionId oldestRunningXid)
+{
+	dlist_mutable_iter it;
+
+	/*
+	 * Iterate through all (potential) toplevel TXNs and abort all that are
+	 * older than what possibly can be running. Once we've found the first
+	 * that is alive we stop, there might be some that acquired an xid earlier
+	 * but started writing later, but it's unlikely and they will be cleaned
+	 * up in a later call to this function.
+	 */
+	dlist_foreach_modify(it, &rb->toplevel_by_lsn)
+	{
+		ReorderBufferTXN *txn;
+
+		txn = dlist_container(ReorderBufferTXN, node, it.cur);
+
+		if (TransactionIdPrecedes(txn->xid, oldestRunningXid))
+		{
+			elog(DEBUG2, "aborting old transaction %u", txn->xid);
+
+			/* remove potential on-disk data, and deallocate this tx */
+			ReorderBufferCleanupTXN(rb, txn);
+		}
+		else
+			return;
+	}
+}
+
+/*
+ * Forget the contents of a transaction if we aren't interested in its
+ * contents. Needs to be first called for subtransactions and then for the
+ * toplevel xid.
+ *
+ * This is significantly different to ReorderBufferAbort() because
+ * transactions that have committed need to be treated differently from aborted
+ * ones since they may have modified the catalog.
+ *
+ * Note that this is only allowed to be called in the moment a transaction
+ * commit has just been read, not earlier; otherwise later records referring
+ * to this xid might re-create the transaction incompletely.
+ */
+void
+ReorderBufferForget(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn)
+{
+	ReorderBufferTXN *txn;
+
+	txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr,
+								false);
+
+	/* unknown, nothing to forget */
+	if (txn == NULL)
+		return;
+
+	/* For streamed transactions notify the remote node about the abort. */
+	if (rbtxn_is_streamed(txn))
+		rb->stream_abort(rb, txn, lsn);
+
+	/* cosmetic... */
+	txn->final_lsn = lsn;
+
+	/*
+	 * Process cache invalidation messages if there are any. Even if we're not
+	 * interested in the transaction's contents, it could have manipulated the
+	 * catalog and we need to update the caches according to that.
+	 */
+	if (txn->base_snapshot != NULL && txn->ninvalidations > 0)
+		ReorderBufferImmediateInvalidation(rb, txn->ninvalidations,
+										   txn->invalidations);
+	else
+		Assert(txn->ninvalidations == 0);
+
+	/* remove potential on-disk data, and deallocate */
+	ReorderBufferCleanupTXN(rb, txn);
+}
+
+/*
+ * Invalidate cache for those transactions that need to be skipped just in case
+ * catalogs were manipulated as part of the transaction.
+ *
+ * Note that this is a special-purpose function for prepared transactions where
+ * we don't want to clean up the TXN even when we decide to skip it. See
+ * DecodePrepare.
+ */
+void
+ReorderBufferInvalidate(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn)
+{
+	ReorderBufferTXN *txn;
+
+	txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr,
+								false);
+
+	/* unknown, nothing to do */
+	if (txn == NULL)
+		return;
+
+	/*
+	 * Process cache invalidation messages if there are any. Even if we're not
+	 * interested in the transaction's contents, it could have manipulated the
+	 * catalog and we need to update the caches according to that.
+	 */
+	if (txn->base_snapshot != NULL && txn->ninvalidations > 0)
+		ReorderBufferImmediateInvalidation(rb, txn->ninvalidations,
+										   txn->invalidations);
+	else
+		Assert(txn->ninvalidations == 0);
+}
+
+
+/*
+ * Execute invalidations happening outside the context of a decoded
+ * transaction. That currently happens either for xid-less commits
+ * (cf. RecordTransactionCommit()) or for invalidations in uninteresting
+ * transactions (via ReorderBufferForget()).
+ */
+void
+ReorderBufferImmediateInvalidation(ReorderBuffer *rb, uint32 ninvalidations,
+								   SharedInvalidationMessage *invalidations)
+{
+	bool		use_subtxn = IsTransactionOrTransactionBlock();
+	int			i;
+
+	if (use_subtxn)
+		BeginInternalSubTransaction("replay");
+
+	/*
+	 * Force invalidations to happen outside of a valid transaction - that way
+	 * entries will just be marked as invalid without accessing the catalog.
+	 * That's advantageous because we don't need to setup the full state
+	 * necessary for catalog access.
+	 */
+	if (use_subtxn)
+		AbortCurrentTransaction();
+
+	for (i = 0; i < ninvalidations; i++)
+		LocalExecuteInvalidationMessage(&invalidations[i]);
+
+	if (use_subtxn)
+		RollbackAndReleaseCurrentSubTransaction();
+}
+
+/*
+ * Tell reorderbuffer about an xid seen in the WAL stream. Has to be called at
+ * least once for every xid in XLogRecord->xl_xid (other places in records
+ * may, but do not have to be passed through here).
+ *
+ * Reorderbuffer keeps some datastructures about transactions in LSN order,
+ * for efficiency. To do that it has to know about when transactions are seen
+ * first in the WAL. As many types of records are not actually interesting for
+ * logical decoding, they do not necessarily pass though here.
+ */
+void
+ReorderBufferProcessXid(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn)
+{
+	/* many records won't have an xid assigned, centralize check here */
+	if (xid != InvalidTransactionId)
+		ReorderBufferTXNByXid(rb, xid, true, NULL, lsn, true);
+}
+
+/*
+ * Add a new snapshot to this transaction that may only used after lsn 'lsn'
+ * because the previous snapshot doesn't describe the catalog correctly for
+ * following rows.
+ */
+void
+ReorderBufferAddSnapshot(ReorderBuffer *rb, TransactionId xid,
+						 XLogRecPtr lsn, Snapshot snap)
+{
+	ReorderBufferChange *change = ReorderBufferGetChange(rb);
+
+	change->data.snapshot = snap;
+	change->action = REORDER_BUFFER_CHANGE_INTERNAL_SNAPSHOT;
+
+	ReorderBufferQueueChange(rb, xid, lsn, change, false);
+}
+
+/*
+ * Set up the transaction's base snapshot.
+ *
+ * If we know that xid is a subtransaction, set the base snapshot on the
+ * top-level transaction instead.
+ */
+void
+ReorderBufferSetBaseSnapshot(ReorderBuffer *rb, TransactionId xid,
+							 XLogRecPtr lsn, Snapshot snap)
+{
+	ReorderBufferTXN *txn;
+	bool		is_new;
+
+	AssertArg(snap != NULL);
+
+	/*
+	 * Fetch the transaction to operate on.  If we know it's a subtransaction,
+	 * operate on its top-level transaction instead.
+	 */
+	txn = ReorderBufferTXNByXid(rb, xid, true, &is_new, lsn, true);
+	if (rbtxn_is_known_subxact(txn))
+		txn = ReorderBufferTXNByXid(rb, txn->toplevel_xid, false,
+									NULL, InvalidXLogRecPtr, false);
+	Assert(txn->base_snapshot == NULL);
+
+	txn->base_snapshot = snap;
+	txn->base_snapshot_lsn = lsn;
+	dlist_push_tail(&rb->txns_by_base_snapshot_lsn, &txn->base_snapshot_node);
+
+	AssertTXNLsnOrder(rb);
+}
+
+/*
+ * Access the catalog with this CommandId at this point in the changestream.
+ *
+ * May only be called for command ids > 1
+ */
+void
+ReorderBufferAddNewCommandId(ReorderBuffer *rb, TransactionId xid,
+							 XLogRecPtr lsn, CommandId cid)
+{
+	ReorderBufferChange *change = ReorderBufferGetChange(rb);
+
+	change->data.command_id = cid;
+	change->action = REORDER_BUFFER_CHANGE_INTERNAL_COMMAND_ID;
+
+	ReorderBufferQueueChange(rb, xid, lsn, change, false);
+}
+
+/*
+ * Update memory counters to account for the new or removed change.
+ *
+ * We update two counters - in the reorder buffer, and in the transaction
+ * containing the change. The reorder buffer counter allows us to quickly
+ * decide if we reached the memory limit, the transaction counter allows
+ * us to quickly pick the largest transaction for eviction.
+ *
+ * When streaming is enabled, we need to update the toplevel transaction
+ * counters instead - we don't really care about subtransactions as we
+ * can't stream them individually anyway, and we only pick toplevel
+ * transactions for eviction. So only toplevel transactions matter.
+ */
+static void
+ReorderBufferChangeMemoryUpdate(ReorderBuffer *rb,
+								ReorderBufferChange *change,
+								bool addition, Size sz)
+{
+	ReorderBufferTXN *txn;
+	ReorderBufferTXN *toptxn;
+
+	Assert(change->txn);
+
+	/*
+	 * Ignore tuple CID changes, because those are not evicted when reaching
+	 * memory limit. So we just don't count them, because it might easily
+	 * trigger a pointless attempt to spill.
+	 */
+	if (change->action == REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID)
+		return;
+
+	txn = change->txn;
+
+	/*
+	 * Update the total size in top level as well. This is later used to
+	 * compute the decoding stats.
+	 */
+	if (txn->toptxn != NULL)
+		toptxn = txn->toptxn;
+	else
+		toptxn = txn;
+
+	if (addition)
+	{
+		txn->size += sz;
+		rb->size += sz;
+
+		/* Update the total size in the top transaction. */
+		toptxn->total_size += sz;
+	}
+	else
+	{
+		Assert((rb->size >= sz) && (txn->size >= sz));
+		txn->size -= sz;
+		rb->size -= sz;
+
+		/* Update the total size in the top transaction. */
+		toptxn->total_size -= sz;
+	}
+
+	Assert(txn->size <= rb->size);
+}
+
+/*
+ * Add new (relfilenode, tid) -> (cmin, cmax) mappings.
+ *
+ * We do not include this change type in memory accounting, because we
+ * keep CIDs in a separate list and do not evict them when reaching
+ * the memory limit.
+ */
+void
+ReorderBufferAddNewTupleCids(ReorderBuffer *rb, TransactionId xid,
+							 XLogRecPtr lsn, RelFileNode node,
+							 ItemPointerData tid, CommandId cmin,
+							 CommandId cmax, CommandId combocid)
+{
+	ReorderBufferChange *change = ReorderBufferGetChange(rb);
+	ReorderBufferTXN *txn;
+
+	txn = ReorderBufferTXNByXid(rb, xid, true, NULL, lsn, true);
+
+	change->data.tuplecid.node = node;
+	change->data.tuplecid.tid = tid;
+	change->data.tuplecid.cmin = cmin;
+	change->data.tuplecid.cmax = cmax;
+	change->data.tuplecid.combocid = combocid;
+	change->lsn = lsn;
+	change->txn = txn;
+	change->action = REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID;
+
+	dlist_push_tail(&txn->tuplecids, &change->node);
+	txn->ntuplecids++;
+}
+
+/*
+ * Setup the invalidation of the toplevel transaction.
+ *
+ * This needs to be called for each XLOG_XACT_INVALIDATIONS message and
+ * accumulates all the invalidation messages in the toplevel transaction as
+ * well as in the form of change in reorder buffer.  We require to record it in
+ * form of the change so that we can execute only the required invalidations
+ * instead of executing all the invalidations on each CommandId increment.  We
+ * also need to accumulate these in the toplevel transaction because in some
+ * cases we skip processing the transaction (see ReorderBufferForget), we need
+ * to execute all the invalidations together.
+ */
+void
+ReorderBufferAddInvalidations(ReorderBuffer *rb, TransactionId xid,
+							  XLogRecPtr lsn, Size nmsgs,
+							  SharedInvalidationMessage *msgs)
+{
+	ReorderBufferTXN *txn;
+	MemoryContext oldcontext;
+	ReorderBufferChange *change;
+
+	txn = ReorderBufferTXNByXid(rb, xid, true, NULL, lsn, true);
+
+	oldcontext = MemoryContextSwitchTo(rb->context);
+
+	/*
+	 * Collect all the invalidations under the top transaction so that we can
+	 * execute them all together.  See comment atop this function
+	 */
+	if (txn->toptxn)
+		txn = txn->toptxn;
+
+	Assert(nmsgs > 0);
+
+	/* Accumulate invalidations. */
+	if (txn->ninvalidations == 0)
+	{
+		txn->ninvalidations = nmsgs;
+		txn->invalidations = (SharedInvalidationMessage *)
+			palloc(sizeof(SharedInvalidationMessage) * nmsgs);
+		memcpy(txn->invalidations, msgs,
+			   sizeof(SharedInvalidationMessage) * nmsgs);
+	}
+	else
+	{
+		txn->invalidations = (SharedInvalidationMessage *)
+			repalloc(txn->invalidations, sizeof(SharedInvalidationMessage) *
+					 (txn->ninvalidations + nmsgs));
+
+		memcpy(txn->invalidations + txn->ninvalidations, msgs,
+			   nmsgs * sizeof(SharedInvalidationMessage));
+		txn->ninvalidations += nmsgs;
+	}
+
+	change = ReorderBufferGetChange(rb);
+	change->action = REORDER_BUFFER_CHANGE_INVALIDATION;
+	change->data.inval.ninvalidations = nmsgs;
+	change->data.inval.invalidations = (SharedInvalidationMessage *)
+		palloc(sizeof(SharedInvalidationMessage) * nmsgs);
+	memcpy(change->data.inval.invalidations, msgs,
+		   sizeof(SharedInvalidationMessage) * nmsgs);
+
+	ReorderBufferQueueChange(rb, xid, lsn, change, false);
+
+	MemoryContextSwitchTo(oldcontext);
+}
+
+/*
+ * Apply all invalidations we know. Possibly we only need parts at this point
+ * in the changestream but we don't know which those are.
+ */
+static void
+ReorderBufferExecuteInvalidations(uint32 nmsgs, SharedInvalidationMessage *msgs)
+{
+	int			i;
+
+	for (i = 0; i < nmsgs; i++)
+		LocalExecuteInvalidationMessage(&msgs[i]);
+}
+
+/*
+ * Mark a transaction as containing catalog changes
+ */
+void
+ReorderBufferXidSetCatalogChanges(ReorderBuffer *rb, TransactionId xid,
+								  XLogRecPtr lsn)
+{
+	ReorderBufferTXN *txn;
+
+	txn = ReorderBufferTXNByXid(rb, xid, true, NULL, lsn, true);
+
+	txn->txn_flags |= RBTXN_HAS_CATALOG_CHANGES;
+
+	/*
+	 * Mark top-level transaction as having catalog changes too if one of its
+	 * children has so that the ReorderBufferBuildTupleCidHash can
+	 * conveniently check just top-level transaction and decide whether to
+	 * build the hash table or not.
+	 */
+	if (txn->toptxn != NULL)
+		txn->toptxn->txn_flags |= RBTXN_HAS_CATALOG_CHANGES;
+}
+
+/*
+ * Query whether a transaction is already *known* to contain catalog
+ * changes. This can be wrong until directly before the commit!
+ */
+bool
+ReorderBufferXidHasCatalogChanges(ReorderBuffer *rb, TransactionId xid)
+{
+	ReorderBufferTXN *txn;
+
+	txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr,
+								false);
+	if (txn == NULL)
+		return false;
+
+	return rbtxn_has_catalog_changes(txn);
+}
+
+/*
+ * ReorderBufferXidHasBaseSnapshot
+ *		Have we already set the base snapshot for the given txn/subtxn?
+ */
+bool
+ReorderBufferXidHasBaseSnapshot(ReorderBuffer *rb, TransactionId xid)
+{
+	ReorderBufferTXN *txn;
+
+	txn = ReorderBufferTXNByXid(rb, xid, false,
+								NULL, InvalidXLogRecPtr, false);
+
+	/* transaction isn't known yet, ergo no snapshot */
+	if (txn == NULL)
+		return false;
+
+	/* a known subtxn? operate on top-level txn instead */
+	if (rbtxn_is_known_subxact(txn))
+		txn = ReorderBufferTXNByXid(rb, txn->toplevel_xid, false,
+									NULL, InvalidXLogRecPtr, false);
+
+	return txn->base_snapshot != NULL;
+}
+
+
+/*
+ * ---------------------------------------
+ * Disk serialization support
+ * ---------------------------------------
+ */
+
+/*
+ * Ensure the IO buffer is >= sz.
+ */
+static void
+ReorderBufferSerializeReserve(ReorderBuffer *rb, Size sz)
+{
+	if (!rb->outbufsize)
+	{
+		rb->outbuf = MemoryContextAlloc(rb->context, sz);
+		rb->outbufsize = sz;
+	}
+	else if (rb->outbufsize < sz)
+	{
+		rb->outbuf = repalloc(rb->outbuf, sz);
+		rb->outbufsize = sz;
+	}
+}
+
+/*
+ * Find the largest transaction (toplevel or subxact) to evict (spill to disk).
+ *
+ * XXX With many subtransactions this might be quite slow, because we'll have
+ * to walk through all of them. There are some options how we could improve
+ * that: (a) maintain some secondary structure with transactions sorted by
+ * amount of changes, (b) not looking for the entirely largest transaction,
+ * but e.g. for transaction using at least some fraction of the memory limit,
+ * and (c) evicting multiple transactions at once, e.g. to free a given portion
+ * of the memory limit (e.g. 50%).
+ */
+static ReorderBufferTXN *
+ReorderBufferLargestTXN(ReorderBuffer *rb)
+{
+	HASH_SEQ_STATUS hash_seq;
+	ReorderBufferTXNByIdEnt *ent;
+	ReorderBufferTXN *largest = NULL;
+
+	hash_seq_init(&hash_seq, rb->by_txn);
+	while ((ent = hash_seq_search(&hash_seq)) != NULL)
+	{
+		ReorderBufferTXN *txn = ent->txn;
+
+		/* if the current transaction is larger, remember it */
+		if ((!largest) || (txn->size > largest->size))
+			largest = txn;
+	}
+
+	Assert(largest);
+	Assert(largest->size > 0);
+	Assert(largest->size <= rb->size);
+
+	return largest;
+}
+
+/*
+ * Find the largest toplevel transaction to evict (by streaming).
+ *
+ * This can be seen as an optimized version of ReorderBufferLargestTXN, which
+ * should give us the same transaction (because we don't update memory account
+ * for subtransaction with streaming, so it's always 0). But we can simply
+ * iterate over the limited number of toplevel transactions that have a base
+ * snapshot. There is no use of selecting a transaction that doesn't have base
+ * snapshot because we don't decode such transactions.
+ *
+ * Note that, we skip transactions that contains incomplete changes. There
+ * is a scope of optimization here such that we can select the largest
+ * transaction which has incomplete changes.  But that will make the code and
+ * design quite complex and that might not be worth the benefit.  If we plan to
+ * stream the transactions that contains incomplete changes then we need to
+ * find a way to partially stream/truncate the transaction changes in-memory
+ * and build a mechanism to partially truncate the spilled files.
+ * Additionally, whenever we partially stream the transaction we need to
+ * maintain the last streamed lsn and next time we need to restore from that
+ * segment and the offset in WAL.  As we stream the changes from the top
+ * transaction and restore them subtransaction wise, we need to even remember
+ * the subxact from where we streamed the last change.
+ */
+static ReorderBufferTXN *
+ReorderBufferLargestTopTXN(ReorderBuffer *rb)
+{
+	dlist_iter	iter;
+	Size		largest_size = 0;
+	ReorderBufferTXN *largest = NULL;
+
+	/* Find the largest top-level transaction having a base snapshot. */
+	dlist_foreach(iter, &rb->txns_by_base_snapshot_lsn)
+	{
+		ReorderBufferTXN *txn;
+
+		txn = dlist_container(ReorderBufferTXN, base_snapshot_node, iter.cur);
+
+		/* must not be a subtxn */
+		Assert(!rbtxn_is_known_subxact(txn));
+		/* base_snapshot must be set */
+		Assert(txn->base_snapshot != NULL);
+
+		if ((largest == NULL || txn->total_size > largest_size) &&
+			(txn->total_size > 0) && !(rbtxn_has_partial_change(txn)))
+		{
+			largest = txn;
+			largest_size = txn->total_size;
+		}
+	}
+
+	return largest;
+}
+
+/*
+ * Check whether the logical_decoding_work_mem limit was reached, and if yes
+ * pick the largest (sub)transaction at-a-time to evict and spill its changes to
+ * disk until we reach under the memory limit.
+ *
+ * XXX At this point we select the transactions until we reach under the memory
+ * limit, but we might also adapt a more elaborate eviction strategy - for example
+ * evicting enough transactions to free certain fraction (e.g. 50%) of the memory
+ * limit.
+ */
+static void
+ReorderBufferCheckMemoryLimit(ReorderBuffer *rb)
+{
+	ReorderBufferTXN *txn;
+
+	/* bail out if we haven't exceeded the memory limit */
+	if (rb->size < logical_decoding_work_mem * 1024L)
+		return;
+
+	/*
+	 * Loop until we reach under the memory limit.  One might think that just
+	 * by evicting the largest (sub)transaction we will come under the memory
+	 * limit based on assumption that the selected transaction is at least as
+	 * large as the most recent change (which caused us to go over the memory
+	 * limit). However, that is not true because a user can reduce the
+	 * logical_decoding_work_mem to a smaller value before the most recent
+	 * change.
+	 */
+	while (rb->size >= logical_decoding_work_mem * 1024L)
+	{
+		/*
+		 * Pick the largest transaction (or subtransaction) and evict it from
+		 * memory by streaming, if possible.  Otherwise, spill to disk.
+		 */
+		if (ReorderBufferCanStartStreaming(rb) &&
+			(txn = ReorderBufferLargestTopTXN(rb)) != NULL)
+		{
+			/* we know there has to be one, because the size is not zero */
+			Assert(txn && !txn->toptxn);
+			Assert(txn->total_size > 0);
+			Assert(rb->size >= txn->total_size);
+
+			ReorderBufferStreamTXN(rb, txn);
+		}
+		else
+		{
+			/*
+			 * Pick the largest transaction (or subtransaction) and evict it
+			 * from memory by serializing it to disk.
+			 */
+			txn = ReorderBufferLargestTXN(rb);
+
+			/* we know there has to be one, because the size is not zero */
+			Assert(txn);
+			Assert(txn->size > 0);
+			Assert(rb->size >= txn->size);
+
+			ReorderBufferSerializeTXN(rb, txn);
+		}
+
+		/*
+		 * After eviction, the transaction should have no entries in memory,
+		 * and should use 0 bytes for changes.
+		 */
+		Assert(txn->size == 0);
+		Assert(txn->nentries_mem == 0);
+	}
+
+	/* We must be under the memory limit now. */
+	Assert(rb->size < logical_decoding_work_mem * 1024L);
+}
+
+/*
+ * Spill data of a large transaction (and its subtransactions) to disk.
+ */
+static void
+ReorderBufferSerializeTXN(ReorderBuffer *rb, ReorderBufferTXN *txn)
+{
+	dlist_iter	subtxn_i;
+	dlist_mutable_iter change_i;
+	int			fd = -1;
+	XLogSegNo	curOpenSegNo = 0;
+	Size		spilled = 0;
+	Size		size = txn->size;
+
+	elog(DEBUG2, "spill %u changes in XID %u to disk",
+		 (uint32) txn->nentries_mem, txn->xid);
+
+	/* do the same to all child TXs */
+	dlist_foreach(subtxn_i, &txn->subtxns)
+	{
+		ReorderBufferTXN *subtxn;
+
+		subtxn = dlist_container(ReorderBufferTXN, node, subtxn_i.cur);
+		ReorderBufferSerializeTXN(rb, subtxn);
+	}
+
+	/* serialize changestream */
+	dlist_foreach_modify(change_i, &txn->changes)
+	{
+		ReorderBufferChange *change;
+
+		change = dlist_container(ReorderBufferChange, node, change_i.cur);
+
+		/*
+		 * store in segment in which it belongs by start lsn, don't split over
+		 * multiple segments tho
+		 */
+		if (fd == -1 ||
+			!XLByteInSeg(change->lsn, curOpenSegNo, wal_segment_size))
+		{
+			char		path[MAXPGPATH];
+
+			if (fd != -1)
+				CloseTransientFile(fd);
+
+			XLByteToSeg(change->lsn, curOpenSegNo, wal_segment_size);
+
+			/*
+			 * No need to care about TLIs here, only used during a single run,
+			 * so each LSN only maps to a specific WAL record.
+			 */
+			ReorderBufferSerializedPath(path, MyReplicationSlot, txn->xid,
+										curOpenSegNo);
+
+			/* open segment, create it if necessary */
+			fd = OpenTransientFile(path,
+								   O_CREAT | O_WRONLY | O_APPEND | PG_BINARY);
+
+			if (fd < 0)
+				ereport(ERROR,
+						(errcode_for_file_access(),
+						 errmsg("could not open file \"%s\": %m", path)));
+		}
+
+		ReorderBufferSerializeChange(rb, txn, fd, change);
+		dlist_delete(&change->node);
+		ReorderBufferReturnChange(rb, change, true);
+
+		spilled++;
+	}
+
+	/* update the statistics iff we have spilled anything */
+	if (spilled)
+	{
+		rb->spillCount += 1;
+		rb->spillBytes += size;
+
+		/* don't consider already serialized transactions */
+		rb->spillTxns += (rbtxn_is_serialized(txn) || rbtxn_is_serialized_clear(txn)) ? 0 : 1;
+
+		/* update the decoding stats */
+		UpdateDecodingStats((LogicalDecodingContext *) rb->private_data);
+	}
+
+	Assert(spilled == txn->nentries_mem);
+	Assert(dlist_is_empty(&txn->changes));
+	txn->nentries_mem = 0;
+	txn->txn_flags |= RBTXN_IS_SERIALIZED;
+
+	if (fd != -1)
+		CloseTransientFile(fd);
+}
+
+/*
+ * Serialize individual change to disk.
+ */
+static void
+ReorderBufferSerializeChange(ReorderBuffer *rb, ReorderBufferTXN *txn,
+							 int fd, ReorderBufferChange *change)
+{
+	ReorderBufferDiskChange *ondisk;
+	Size		sz = sizeof(ReorderBufferDiskChange);
+
+	ReorderBufferSerializeReserve(rb, sz);
+
+	ondisk = (ReorderBufferDiskChange *) rb->outbuf;
+	memcpy(&ondisk->change, change, sizeof(ReorderBufferChange));
+
+	switch (change->action)
+	{
+			/* fall through these, they're all similar enough */
+		case REORDER_BUFFER_CHANGE_INSERT:
+		case REORDER_BUFFER_CHANGE_UPDATE:
+		case REORDER_BUFFER_CHANGE_DELETE:
+		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_INSERT:
+			{
+				char	   *data;
+				ReorderBufferTupleBuf *oldtup,
+						   *newtup;
+				Size		oldlen = 0;
+				Size		newlen = 0;
+
+				oldtup = change->data.tp.oldtuple;
+				newtup = change->data.tp.newtuple;
+
+				if (oldtup)
+				{
+					sz += sizeof(HeapTupleData);
+					oldlen = oldtup->tuple.t_len;
+					sz += oldlen;
+				}
+
+				if (newtup)
+				{
+					sz += sizeof(HeapTupleData);
+					newlen = newtup->tuple.t_len;
+					sz += newlen;
+				}
+
+				/* make sure we have enough space */
+				ReorderBufferSerializeReserve(rb, sz);
+
+				data = ((char *) rb->outbuf) + sizeof(ReorderBufferDiskChange);
+				/* might have been reallocated above */
+				ondisk = (ReorderBufferDiskChange *) rb->outbuf;
+
+				if (oldlen)
+				{
+					memcpy(data, &oldtup->tuple, sizeof(HeapTupleData));
+					data += sizeof(HeapTupleData);
+
+					memcpy(data, oldtup->tuple.t_data, oldlen);
+					data += oldlen;
+				}
+
+				if (newlen)
+				{
+					memcpy(data, &newtup->tuple, sizeof(HeapTupleData));
+					data += sizeof(HeapTupleData);
+
+					memcpy(data, newtup->tuple.t_data, newlen);
+					data += newlen;
+				}
+				break;
+			}
+		case REORDER_BUFFER_CHANGE_MESSAGE:
+			{
+				char	   *data;
+				Size		prefix_size = strlen(change->data.msg.prefix) + 1;
+
+				sz += prefix_size + change->data.msg.message_size +
+					sizeof(Size) + sizeof(Size);
+				ReorderBufferSerializeReserve(rb, sz);
+
+				data = ((char *) rb->outbuf) + sizeof(ReorderBufferDiskChange);
+
+				/* might have been reallocated above */
+				ondisk = (ReorderBufferDiskChange *) rb->outbuf;
+
+				/* write the prefix including the size */
+				memcpy(data, &prefix_size, sizeof(Size));
+				data += sizeof(Size);
+				memcpy(data, change->data.msg.prefix,
+					   prefix_size);
+				data += prefix_size;
+
+				/* write the message including the size */
+				memcpy(data, &change->data.msg.message_size, sizeof(Size));
+				data += sizeof(Size);
+				memcpy(data, change->data.msg.message,
+					   change->data.msg.message_size);
+				data += change->data.msg.message_size;
+
+				break;
+			}
+		case REORDER_BUFFER_CHANGE_INVALIDATION:
+			{
+				char	   *data;
+				Size		inval_size = sizeof(SharedInvalidationMessage) *
+				change->data.inval.ninvalidations;
+
+				sz += inval_size;
+
+				ReorderBufferSerializeReserve(rb, sz);
+				data = ((char *) rb->outbuf) + sizeof(ReorderBufferDiskChange);
+
+				/* might have been reallocated above */
+				ondisk = (ReorderBufferDiskChange *) rb->outbuf;
+				memcpy(data, change->data.inval.invalidations, inval_size);
+				data += inval_size;
+
+				break;
+			}
+		case REORDER_BUFFER_CHANGE_INTERNAL_SNAPSHOT:
+			{
+				Snapshot	snap;
+				char	   *data;
+
+				snap = change->data.snapshot;
+
+				sz += sizeof(SnapshotData) +
+					sizeof(TransactionId) * snap->xcnt +
+					sizeof(TransactionId) * snap->subxcnt;
+
+				/* make sure we have enough space */
+				ReorderBufferSerializeReserve(rb, sz);
+				data = ((char *) rb->outbuf) + sizeof(ReorderBufferDiskChange);
+				/* might have been reallocated above */
+				ondisk = (ReorderBufferDiskChange *) rb->outbuf;
+
+				memcpy(data, snap, sizeof(SnapshotData));
+				data += sizeof(SnapshotData);
+
+				if (snap->xcnt)
+				{
+					memcpy(data, snap->xip,
+						   sizeof(TransactionId) * snap->xcnt);
+					data += sizeof(TransactionId) * snap->xcnt;
+				}
+
+				if (snap->subxcnt)
+				{
+					memcpy(data, snap->subxip,
+						   sizeof(TransactionId) * snap->subxcnt);
+					data += sizeof(TransactionId) * snap->subxcnt;
+				}
+				break;
+			}
+		case REORDER_BUFFER_CHANGE_TRUNCATE:
+			{
+				Size		size;
+				char	   *data;
+
+				/* account for the OIDs of truncated relations */
+				size = sizeof(Oid) * change->data.truncate.nrelids;
+				sz += size;
+
+				/* make sure we have enough space */
+				ReorderBufferSerializeReserve(rb, sz);
+
+				data = ((char *) rb->outbuf) + sizeof(ReorderBufferDiskChange);
+				/* might have been reallocated above */
+				ondisk = (ReorderBufferDiskChange *) rb->outbuf;
+
+				memcpy(data, change->data.truncate.relids, size);
+				data += size;
+
+				break;
+			}
+		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM:
+		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_ABORT:
+		case REORDER_BUFFER_CHANGE_INTERNAL_COMMAND_ID:
+		case REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID:
+			/* ReorderBufferChange contains everything important */
+			break;
+	}
+
+	ondisk->size = sz;
+
+	errno = 0;
+	pgstat_report_wait_start(WAIT_EVENT_REORDER_BUFFER_WRITE);
+	if (write(fd, rb->outbuf, ondisk->size) != ondisk->size)
+	{
+		int			save_errno = errno;
+
+		CloseTransientFile(fd);
+
+		/* if write didn't set errno, assume problem is no disk space */
+		errno = save_errno ? save_errno : ENOSPC;
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not write to data file for XID %u: %m",
+						txn->xid)));
+	}
+	pgstat_report_wait_end();
+
+	/*
+	 * Keep the transaction's final_lsn up to date with each change we send to
+	 * disk, so that ReorderBufferRestoreCleanup works correctly.  (We used to
+	 * only do this on commit and abort records, but that doesn't work if a
+	 * system crash leaves a transaction without its abort record).
+	 *
+	 * Make sure not to move it backwards.
+	 */
+	if (txn->final_lsn < change->lsn)
+		txn->final_lsn = change->lsn;
+
+	Assert(ondisk->change.action == change->action);
+}
+
+/* Returns true, if the output plugin supports streaming, false, otherwise. */
+static inline bool
+ReorderBufferCanStream(ReorderBuffer *rb)
+{
+	LogicalDecodingContext *ctx = rb->private_data;
+
+	return ctx->streaming;
+}
+
+/* Returns true, if the streaming can be started now, false, otherwise. */
+static inline bool
+ReorderBufferCanStartStreaming(ReorderBuffer *rb)
+{
+	LogicalDecodingContext *ctx = rb->private_data;
+	SnapBuild  *builder = ctx->snapshot_builder;
+
+	/* We can't start streaming unless a consistent state is reached. */
+	if (SnapBuildCurrentState(builder) < SNAPBUILD_CONSISTENT)
+		return false;
+
+	/*
+	 * We can't start streaming immediately even if the streaming is enabled
+	 * because we previously decoded this transaction and now just are
+	 * restarting.
+	 */
+	if (ReorderBufferCanStream(rb) &&
+		!SnapBuildXactNeedsSkip(builder, ctx->reader->EndRecPtr))
+		return true;
+
+	return false;
+}
+
+/*
+ * Send data of a large transaction (and its subtransactions) to the
+ * output plugin, but using the stream API.
+ */
+static void
+ReorderBufferStreamTXN(ReorderBuffer *rb, ReorderBufferTXN *txn)
+{
+	Snapshot	snapshot_now;
+	CommandId	command_id;
+	Size		stream_bytes;
+	bool		txn_is_streamed;
+
+	/* We can never reach here for a subtransaction. */
+	Assert(txn->toptxn == NULL);
+
+	/*
+	 * We can't make any assumptions about base snapshot here, similar to what
+	 * ReorderBufferCommit() does. That relies on base_snapshot getting
+	 * transferred from subxact in ReorderBufferCommitChild(), but that was
+	 * not yet called as the transaction is in-progress.
+	 *
+	 * So just walk the subxacts and use the same logic here. But we only need
+	 * to do that once, when the transaction is streamed for the first time.
+	 * After that we need to reuse the snapshot from the previous run.
+	 *
+	 * Unlike DecodeCommit which adds xids of all the subtransactions in
+	 * snapshot's xip array via SnapBuildCommittedTxn, we can't do that here
+	 * but we do add them to subxip array instead via ReorderBufferCopySnap.
+	 * This allows the catalog changes made in subtransactions decoded till
+	 * now to be visible.
+	 */
+	if (txn->snapshot_now == NULL)
+	{
+		dlist_iter	subxact_i;
+
+		/* make sure this transaction is streamed for the first time */
+		Assert(!rbtxn_is_streamed(txn));
+
+		/* at the beginning we should have invalid command ID */
+		Assert(txn->command_id == InvalidCommandId);
+
+		dlist_foreach(subxact_i, &txn->subtxns)
+		{
+			ReorderBufferTXN *subtxn;
+
+			subtxn = dlist_container(ReorderBufferTXN, node, subxact_i.cur);
+			ReorderBufferTransferSnapToParent(txn, subtxn);
+		}
+
+		/*
+		 * If this transaction has no snapshot, it didn't make any changes to
+		 * the database till now, so there's nothing to decode.
+		 */
+		if (txn->base_snapshot == NULL)
+		{
+			Assert(txn->ninvalidations == 0);
+			return;
+		}
+
+		command_id = FirstCommandId;
+		snapshot_now = ReorderBufferCopySnap(rb, txn->base_snapshot,
+											 txn, command_id);
+	}
+	else
+	{
+		/* the transaction must have been already streamed */
+		Assert(rbtxn_is_streamed(txn));
+
+		/*
+		 * Nah, we already have snapshot from the previous streaming run. We
+		 * assume new subxacts can't move the LSN backwards, and so can't beat
+		 * the LSN condition in the previous branch (so no need to walk
+		 * through subxacts again). In fact, we must not do that as we may be
+		 * using snapshot half-way through the subxact.
+		 */
+		command_id = txn->command_id;
+
+		/*
+		 * We can't use txn->snapshot_now directly because after the last
+		 * streaming run, we might have got some new sub-transactions. So we
+		 * need to add them to the snapshot.
+		 */
+		snapshot_now = ReorderBufferCopySnap(rb, txn->snapshot_now,
+											 txn, command_id);
+
+		/* Free the previously copied snapshot. */
+		Assert(txn->snapshot_now->copied);
+		ReorderBufferFreeSnap(rb, txn->snapshot_now);
+		txn->snapshot_now = NULL;
+	}
+
+	/*
+	 * Remember this information to be used later to update stats. We can't
+	 * update the stats here as an error while processing the changes would
+	 * lead to the accumulation of stats even though we haven't streamed all
+	 * the changes.
+	 */
+	txn_is_streamed = rbtxn_is_streamed(txn);
+	stream_bytes = txn->total_size;
+
+	/* Process and send the changes to output plugin. */
+	ReorderBufferProcessTXN(rb, txn, InvalidXLogRecPtr, snapshot_now,
+							command_id, true);
+
+	rb->streamCount += 1;
+	rb->streamBytes += stream_bytes;
+
+	/* Don't consider already streamed transaction. */
+	rb->streamTxns += (txn_is_streamed) ? 0 : 1;
+
+	/* update the decoding stats */
+	UpdateDecodingStats((LogicalDecodingContext *) rb->private_data);
+
+	Assert(dlist_is_empty(&txn->changes));
+	Assert(txn->nentries == 0);
+	Assert(txn->nentries_mem == 0);
+}
+
+/*
+ * Size of a change in memory.
+ */
+static Size
+ReorderBufferChangeSize(ReorderBufferChange *change)
+{
+	Size		sz = sizeof(ReorderBufferChange);
+
+	switch (change->action)
+	{
+			/* fall through these, they're all similar enough */
+		case REORDER_BUFFER_CHANGE_INSERT:
+		case REORDER_BUFFER_CHANGE_UPDATE:
+		case REORDER_BUFFER_CHANGE_DELETE:
+		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_INSERT:
+			{
+				ReorderBufferTupleBuf *oldtup,
+						   *newtup;
+				Size		oldlen = 0;
+				Size		newlen = 0;
+
+				oldtup = change->data.tp.oldtuple;
+				newtup = change->data.tp.newtuple;
+
+				if (oldtup)
+				{
+					sz += sizeof(HeapTupleData);
+					oldlen = oldtup->tuple.t_len;
+					sz += oldlen;
+				}
+
+				if (newtup)
+				{
+					sz += sizeof(HeapTupleData);
+					newlen = newtup->tuple.t_len;
+					sz += newlen;
+				}
+
+				break;
+			}
+		case REORDER_BUFFER_CHANGE_MESSAGE:
+			{
+				Size		prefix_size = strlen(change->data.msg.prefix) + 1;
+
+				sz += prefix_size + change->data.msg.message_size +
+					sizeof(Size) + sizeof(Size);
+
+				break;
+			}
+		case REORDER_BUFFER_CHANGE_INVALIDATION:
+			{
+				sz += sizeof(SharedInvalidationMessage) *
+					change->data.inval.ninvalidations;
+				break;
+			}
+		case REORDER_BUFFER_CHANGE_INTERNAL_SNAPSHOT:
+			{
+				Snapshot	snap;
+
+				snap = change->data.snapshot;
+
+				sz += sizeof(SnapshotData) +
+					sizeof(TransactionId) * snap->xcnt +
+					sizeof(TransactionId) * snap->subxcnt;
+
+				break;
+			}
+		case REORDER_BUFFER_CHANGE_TRUNCATE:
+			{
+				sz += sizeof(Oid) * change->data.truncate.nrelids;
+
+				break;
+			}
+		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM:
+		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_ABORT:
+		case REORDER_BUFFER_CHANGE_INTERNAL_COMMAND_ID:
+		case REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID:
+			/* ReorderBufferChange contains everything important */
+			break;
+	}
+
+	return sz;
+}
+
+
+/*
+ * Restore a number of changes spilled to disk back into memory.
+ */
+static Size
+ReorderBufferRestoreChanges(ReorderBuffer *rb, ReorderBufferTXN *txn,
+							TXNEntryFile *file, XLogSegNo *segno)
+{
+	Size		restored = 0;
+	XLogSegNo	last_segno;
+	dlist_mutable_iter cleanup_iter;
+	File	   *fd = &file->vfd;
+
+	Assert(txn->first_lsn != InvalidXLogRecPtr);
+	Assert(txn->final_lsn != InvalidXLogRecPtr);
+
+	/* free current entries, so we have memory for more */
+	dlist_foreach_modify(cleanup_iter, &txn->changes)
+	{
+		ReorderBufferChange *cleanup =
+		dlist_container(ReorderBufferChange, node, cleanup_iter.cur);
+
+		dlist_delete(&cleanup->node);
+		ReorderBufferReturnChange(rb, cleanup, true);
+	}
+	txn->nentries_mem = 0;
+	Assert(dlist_is_empty(&txn->changes));
+
+	XLByteToSeg(txn->final_lsn, last_segno, wal_segment_size);
+
+	while (restored < max_changes_in_memory && *segno <= last_segno)
+	{
+		int			readBytes;
+		ReorderBufferDiskChange *ondisk;
+
+		if (*fd == -1)
+		{
+			char		path[MAXPGPATH];
+
+			/* first time in */
+			if (*segno == 0)
+				XLByteToSeg(txn->first_lsn, *segno, wal_segment_size);
+
+			Assert(*segno != 0 || dlist_is_empty(&txn->changes));
+
+			/*
+			 * No need to care about TLIs here, only used during a single run,
+			 * so each LSN only maps to a specific WAL record.
+			 */
+			ReorderBufferSerializedPath(path, MyReplicationSlot, txn->xid,
+										*segno);
+
+			*fd = PathNameOpenFile(path, O_RDONLY | PG_BINARY);
+
+			/* No harm in resetting the offset even in case of failure */
+			file->curOffset = 0;
+
+			if (*fd < 0 && errno == ENOENT)
+			{
+				*fd = -1;
+				(*segno)++;
+				continue;
+			}
+			else if (*fd < 0)
+				ereport(ERROR,
+						(errcode_for_file_access(),
+						 errmsg("could not open file \"%s\": %m",
+								path)));
+		}
+
+		/*
+		 * Read the statically sized part of a change which has information
+		 * about the total size. If we couldn't read a record, we're at the
+		 * end of this file.
+		 */
+		ReorderBufferSerializeReserve(rb, sizeof(ReorderBufferDiskChange));
+		readBytes = FileRead(file->vfd, rb->outbuf,
+							 sizeof(ReorderBufferDiskChange),
+							 file->curOffset, WAIT_EVENT_REORDER_BUFFER_READ);
+
+		/* eof */
+		if (readBytes == 0)
+		{
+			FileClose(*fd);
+			*fd = -1;
+			(*segno)++;
+			continue;
+		}
+		else if (readBytes < 0)
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not read from reorderbuffer spill file: %m")));
+		else if (readBytes != sizeof(ReorderBufferDiskChange))
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not read from reorderbuffer spill file: read %d instead of %u bytes",
+							readBytes,
+							(uint32) sizeof(ReorderBufferDiskChange))));
+
+		file->curOffset += readBytes;
+
+		ondisk = (ReorderBufferDiskChange *) rb->outbuf;
+
+		ReorderBufferSerializeReserve(rb,
+									  sizeof(ReorderBufferDiskChange) + ondisk->size);
+		ondisk = (ReorderBufferDiskChange *) rb->outbuf;
+
+		readBytes = FileRead(file->vfd,
+							 rb->outbuf + sizeof(ReorderBufferDiskChange),
+							 ondisk->size - sizeof(ReorderBufferDiskChange),
+							 file->curOffset,
+							 WAIT_EVENT_REORDER_BUFFER_READ);
+
+		if (readBytes < 0)
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not read from reorderbuffer spill file: %m")));
+		else if (readBytes != ondisk->size - sizeof(ReorderBufferDiskChange))
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not read from reorderbuffer spill file: read %d instead of %u bytes",
+							readBytes,
+							(uint32) (ondisk->size - sizeof(ReorderBufferDiskChange)))));
+
+		file->curOffset += readBytes;
+
+		/*
+		 * ok, read a full change from disk, now restore it into proper
+		 * in-memory format
+		 */
+		ReorderBufferRestoreChange(rb, txn, rb->outbuf);
+		restored++;
+	}
+
+	return restored;
+}
+
+/*
+ * Convert change from its on-disk format to in-memory format and queue it onto
+ * the TXN's ->changes list.
+ *
+ * Note: although "data" is declared char*, at entry it points to a
+ * maxalign'd buffer, making it safe in most of this function to assume
+ * that the pointed-to data is suitably aligned for direct access.
+ */
+static void
+ReorderBufferRestoreChange(ReorderBuffer *rb, ReorderBufferTXN *txn,
+						   char *data)
+{
+	ReorderBufferDiskChange *ondisk;
+	ReorderBufferChange *change;
+
+	ondisk = (ReorderBufferDiskChange *) data;
+
+	change = ReorderBufferGetChange(rb);
+
+	/* copy static part */
+	memcpy(change, &ondisk->change, sizeof(ReorderBufferChange));
+
+	data += sizeof(ReorderBufferDiskChange);
+
+	/* restore individual stuff */
+	switch (change->action)
+	{
+			/* fall through these, they're all similar enough */
+		case REORDER_BUFFER_CHANGE_INSERT:
+		case REORDER_BUFFER_CHANGE_UPDATE:
+		case REORDER_BUFFER_CHANGE_DELETE:
+		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_INSERT:
+			if (change->data.tp.oldtuple)
+			{
+				uint32		tuplelen = ((HeapTuple) data)->t_len;
+
+				change->data.tp.oldtuple =
+					ReorderBufferGetTupleBuf(rb, tuplelen - SizeofHeapTupleHeader);
+
+				/* restore ->tuple */
+				memcpy(&change->data.tp.oldtuple->tuple, data,
+					   sizeof(HeapTupleData));
+				data += sizeof(HeapTupleData);
+
+				/* reset t_data pointer into the new tuplebuf */
+				change->data.tp.oldtuple->tuple.t_data =
+					ReorderBufferTupleBufData(change->data.tp.oldtuple);
+
+				/* restore tuple data itself */
+				memcpy(change->data.tp.oldtuple->tuple.t_data, data, tuplelen);
+				data += tuplelen;
+			}
+
+			if (change->data.tp.newtuple)
+			{
+				/* here, data might not be suitably aligned! */
+				uint32		tuplelen;
+
+				memcpy(&tuplelen, data + offsetof(HeapTupleData, t_len),
+					   sizeof(uint32));
+
+				change->data.tp.newtuple =
+					ReorderBufferGetTupleBuf(rb, tuplelen - SizeofHeapTupleHeader);
+
+				/* restore ->tuple */
+				memcpy(&change->data.tp.newtuple->tuple, data,
+					   sizeof(HeapTupleData));
+				data += sizeof(HeapTupleData);
+
+				/* reset t_data pointer into the new tuplebuf */
+				change->data.tp.newtuple->tuple.t_data =
+					ReorderBufferTupleBufData(change->data.tp.newtuple);
+
+				/* restore tuple data itself */
+				memcpy(change->data.tp.newtuple->tuple.t_data, data, tuplelen);
+				data += tuplelen;
+			}
+
+			break;
+		case REORDER_BUFFER_CHANGE_MESSAGE:
+			{
+				Size		prefix_size;
+
+				/* read prefix */
+				memcpy(&prefix_size, data, sizeof(Size));
+				data += sizeof(Size);
+				change->data.msg.prefix = MemoryContextAlloc(rb->context,
+															 prefix_size);
+				memcpy(change->data.msg.prefix, data, prefix_size);
+				Assert(change->data.msg.prefix[prefix_size - 1] == '\0');
+				data += prefix_size;
+
+				/* read the message */
+				memcpy(&change->data.msg.message_size, data, sizeof(Size));
+				data += sizeof(Size);
+				change->data.msg.message = MemoryContextAlloc(rb->context,
+															  change->data.msg.message_size);
+				memcpy(change->data.msg.message, data,
+					   change->data.msg.message_size);
+				data += change->data.msg.message_size;
+
+				break;
+			}
+		case REORDER_BUFFER_CHANGE_INVALIDATION:
+			{
+				Size		inval_size = sizeof(SharedInvalidationMessage) *
+				change->data.inval.ninvalidations;
+
+				change->data.inval.invalidations =
+					MemoryContextAlloc(rb->context, inval_size);
+
+				/* read the message */
+				memcpy(change->data.inval.invalidations, data, inval_size);
+
+				break;
+			}
+		case REORDER_BUFFER_CHANGE_INTERNAL_SNAPSHOT:
+			{
+				Snapshot	oldsnap;
+				Snapshot	newsnap;
+				Size		size;
+
+				oldsnap = (Snapshot) data;
+
+				size = sizeof(SnapshotData) +
+					sizeof(TransactionId) * oldsnap->xcnt +
+					sizeof(TransactionId) * (oldsnap->subxcnt + 0);
+
+				change->data.snapshot = MemoryContextAllocZero(rb->context, size);
+
+				newsnap = change->data.snapshot;
+
+				memcpy(newsnap, data, size);
+				newsnap->xip = (TransactionId *)
+					(((char *) newsnap) + sizeof(SnapshotData));
+				newsnap->subxip = newsnap->xip + newsnap->xcnt;
+				newsnap->copied = true;
+				break;
+			}
+			/* the base struct contains all the data, easy peasy */
+		case REORDER_BUFFER_CHANGE_TRUNCATE:
+			{
+				Oid		   *relids;
+
+				relids = ReorderBufferGetRelids(rb,
+												change->data.truncate.nrelids);
+				memcpy(relids, data, change->data.truncate.nrelids * sizeof(Oid));
+				change->data.truncate.relids = relids;
+
+				break;
+			}
+		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM:
+		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_ABORT:
+		case REORDER_BUFFER_CHANGE_INTERNAL_COMMAND_ID:
+		case REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID:
+			break;
+	}
+
+	dlist_push_tail(&txn->changes, &change->node);
+	txn->nentries_mem++;
+
+	/*
+	 * Update memory accounting for the restored change.  We need to do this
+	 * although we don't check the memory limit when restoring the changes in
+	 * this branch (we only do that when initially queueing the changes after
+	 * decoding), because we will release the changes later, and that will
+	 * update the accounting too (subtracting the size from the counters). And
+	 * we don't want to underflow there.
+	 */
+	ReorderBufferChangeMemoryUpdate(rb, change, true,
+									ReorderBufferChangeSize(change));
+}
+
+/*
+ * Remove all on-disk stored for the passed in transaction.
+ */
+static void
+ReorderBufferRestoreCleanup(ReorderBuffer *rb, ReorderBufferTXN *txn)
+{
+	XLogSegNo	first;
+	XLogSegNo	cur;
+	XLogSegNo	last;
+
+	Assert(txn->first_lsn != InvalidXLogRecPtr);
+	Assert(txn->final_lsn != InvalidXLogRecPtr);
+
+	XLByteToSeg(txn->first_lsn, first, wal_segment_size);
+	XLByteToSeg(txn->final_lsn, last, wal_segment_size);
+
+	/* iterate over all possible filenames, and delete them */
+	for (cur = first; cur <= last; cur++)
+	{
+		char		path[MAXPGPATH];
+
+		ReorderBufferSerializedPath(path, MyReplicationSlot, txn->xid, cur);
+		if (unlink(path) != 0 && errno != ENOENT)
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not remove file \"%s\": %m", path)));
+	}
+}
+
+/*
+ * Remove any leftover serialized reorder buffers from a slot directory after a
+ * prior crash or decoding session exit.
+ */
+static void
+ReorderBufferCleanupSerializedTXNs(const char *slotname)
+{
+	DIR		   *spill_dir;
+	struct dirent *spill_de;
+	struct stat statbuf;
+	char		path[MAXPGPATH * 2 + 12];
+
+	sprintf(path, "pg_replslot/%s", slotname);
+
+	/* we're only handling directories here, skip if it's not ours */
+	if (lstat(path, &statbuf) == 0 && !S_ISDIR(statbuf.st_mode))
+		return;
+
+	spill_dir = AllocateDir(path);
+	while ((spill_de = ReadDirExtended(spill_dir, path, INFO)) != NULL)
+	{
+		/* only look at names that can be ours */
+		if (strncmp(spill_de->d_name, "xid", 3) == 0)
+		{
+			snprintf(path, sizeof(path),
+					 "pg_replslot/%s/%s", slotname,
+					 spill_de->d_name);
+
+			if (unlink(path) != 0)
+				ereport(ERROR,
+						(errcode_for_file_access(),
+						 errmsg("could not remove file \"%s\" during removal of pg_replslot/%s/xid*: %m",
+								path, slotname)));
+		}
+	}
+	FreeDir(spill_dir);
+}
+
+/*
+ * Given a replication slot, transaction ID and segment number, fill in the
+ * corresponding spill file into 'path', which is a caller-owned buffer of size
+ * at least MAXPGPATH.
+ */
+static void
+ReorderBufferSerializedPath(char *path, ReplicationSlot *slot, TransactionId xid,
+							XLogSegNo segno)
+{
+	XLogRecPtr	recptr;
+
+	XLogSegNoOffsetToRecPtr(segno, 0, wal_segment_size, recptr);
+
+	snprintf(path, MAXPGPATH, "pg_replslot/%s/xid-%u-lsn-%X-%X.spill",
+			 NameStr(MyReplicationSlot->data.name),
+			 xid, LSN_FORMAT_ARGS(recptr));
+}
+
+/*
+ * Delete all data spilled to disk after we've restarted/crashed. It will be
+ * recreated when the respective slots are reused.
+ */
+void
+StartupReorderBuffer(void)
+{
+	DIR		   *logical_dir;
+	struct dirent *logical_de;
+
+	logical_dir = AllocateDir("pg_replslot");
+	while ((logical_de = ReadDir(logical_dir, "pg_replslot")) != NULL)
+	{
+		if (strcmp(logical_de->d_name, ".") == 0 ||
+			strcmp(logical_de->d_name, "..") == 0)
+			continue;
+
+		/* if it cannot be a slot, skip the directory */
+		if (!ReplicationSlotValidateName(logical_de->d_name, DEBUG2))
+			continue;
+
+		/*
+		 * ok, has to be a surviving logical slot, iterate and delete
+		 * everything starting with xid-*
+		 */
+		ReorderBufferCleanupSerializedTXNs(logical_de->d_name);
+	}
+	FreeDir(logical_dir);
+}
+
+/* ---------------------------------------
+ * toast reassembly support
+ * ---------------------------------------
+ */
+
+/*
+ * Initialize per tuple toast reconstruction support.
+ */
+static void
+ReorderBufferToastInitHash(ReorderBuffer *rb, ReorderBufferTXN *txn)
+{
+	HASHCTL		hash_ctl;
+
+	Assert(txn->toast_hash == NULL);
+
+	hash_ctl.keysize = sizeof(Oid);
+	hash_ctl.entrysize = sizeof(ReorderBufferToastEnt);
+	hash_ctl.hcxt = rb->context;
+	txn->toast_hash = hash_create("ReorderBufferToastHash", 5, &hash_ctl,
+								  HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
+}
+
+/*
+ * Per toast-chunk handling for toast reconstruction
+ *
+ * Appends a toast chunk so we can reconstruct it when the tuple "owning" the
+ * toasted Datum comes along.
+ */
+static void
+ReorderBufferToastAppendChunk(ReorderBuffer *rb, ReorderBufferTXN *txn,
+							  Relation relation, ReorderBufferChange *change)
+{
+	ReorderBufferToastEnt *ent;
+	ReorderBufferTupleBuf *newtup;
+	bool		found;
+	int32		chunksize;
+	bool		isnull;
+	Pointer		chunk;
+	TupleDesc	desc = RelationGetDescr(relation);
+	Oid			chunk_id;
+	int32		chunk_seq;
+
+	if (txn->toast_hash == NULL)
+		ReorderBufferToastInitHash(rb, txn);
+
+	Assert(IsToastRelation(relation));
+
+	newtup = change->data.tp.newtuple;
+	chunk_id = DatumGetObjectId(fastgetattr(&newtup->tuple, 1, desc, &isnull));
+	Assert(!isnull);
+	chunk_seq = DatumGetInt32(fastgetattr(&newtup->tuple, 2, desc, &isnull));
+	Assert(!isnull);
+
+	ent = (ReorderBufferToastEnt *)
+		hash_search(txn->toast_hash,
+					(void *) &chunk_id,
+					HASH_ENTER,
+					&found);
+
+	if (!found)
+	{
+		Assert(ent->chunk_id == chunk_id);
+		ent->num_chunks = 0;
+		ent->last_chunk_seq = 0;
+		ent->size = 0;
+		ent->reconstructed = NULL;
+		dlist_init(&ent->chunks);
+
+		if (chunk_seq != 0)
+			elog(ERROR, "got sequence entry %d for toast chunk %u instead of seq 0",
+				 chunk_seq, chunk_id);
+	}
+	else if (found && chunk_seq != ent->last_chunk_seq + 1)
+		elog(ERROR, "got sequence entry %d for toast chunk %u instead of seq %d",
+			 chunk_seq, chunk_id, ent->last_chunk_seq + 1);
+
+	chunk = DatumGetPointer(fastgetattr(&newtup->tuple, 3, desc, &isnull));
+	Assert(!isnull);
+
+	/* calculate size so we can allocate the right size at once later */
+	if (!VARATT_IS_EXTENDED(chunk))
+		chunksize = VARSIZE(chunk) - VARHDRSZ;
+	else if (VARATT_IS_SHORT(chunk))
+		/* could happen due to heap_form_tuple doing its thing */
+		chunksize = VARSIZE_SHORT(chunk) - VARHDRSZ_SHORT;
+	else
+		elog(ERROR, "unexpected type of toast chunk");
+
+	ent->size += chunksize;
+	ent->last_chunk_seq = chunk_seq;
+	ent->num_chunks++;
+	dlist_push_tail(&ent->chunks, &change->node);
+}
+
+/*
+ * Rejigger change->newtuple to point to in-memory toast tuples instead to
+ * on-disk toast tuples that may not longer exist (think DROP TABLE or VACUUM).
+ *
+ * We cannot replace unchanged toast tuples though, so those will still point
+ * to on-disk toast data.
+ *
+ * While updating the existing change with detoasted tuple data, we need to
+ * update the memory accounting info, because the change size will differ.
+ * Otherwise the accounting may get out of sync, triggering serialization
+ * at unexpected times.
+ *
+ * We simply subtract size of the change before rejiggering the tuple, and
+ * then adding the new size. This makes it look like the change was removed
+ * and then added back, except it only tweaks the accounting info.
+ *
+ * In particular it can't trigger serialization, which would be pointless
+ * anyway as it happens during commit processing right before handing
+ * the change to the output plugin.
+ */
+static void
+ReorderBufferToastReplace(ReorderBuffer *rb, ReorderBufferTXN *txn,
+						  Relation relation, ReorderBufferChange *change)
+{
+	TupleDesc	desc;
+	int			natt;
+	Datum	   *attrs;
+	bool	   *isnull;
+	bool	   *free;
+	HeapTuple	tmphtup;
+	Relation	toast_rel;
+	TupleDesc	toast_desc;
+	MemoryContext oldcontext;
+	ReorderBufferTupleBuf *newtup;
+	Size		old_size;
+
+	/* no toast tuples changed */
+	if (txn->toast_hash == NULL)
+		return;
+
+	/*
+	 * We're going to modify the size of the change. So, to make sure the
+	 * accounting is correct we record the current change size and then after
+	 * re-computing the change we'll subtract the recorded size and then
+	 * re-add the new change size at the end. We don't immediately subtract
+	 * the old size because if there is any error before we add the new size,
+	 * we will release the changes and that will update the accounting info
+	 * (subtracting the size from the counters). And we don't want to
+	 * underflow there.
+	 */
+	old_size = ReorderBufferChangeSize(change);
+
+	oldcontext = MemoryContextSwitchTo(rb->context);
+
+	/* we should only have toast tuples in an INSERT or UPDATE */
+	Assert(change->data.tp.newtuple);
+
+	desc = RelationGetDescr(relation);
+
+	toast_rel = RelationIdGetRelation(relation->rd_rel->reltoastrelid);
+	if (!RelationIsValid(toast_rel))
+		elog(ERROR, "could not open toast relation with OID %u (base relation \"%s\")",
+			 relation->rd_rel->reltoastrelid, RelationGetRelationName(relation));
+
+	toast_desc = RelationGetDescr(toast_rel);
+
+	/* should we allocate from stack instead? */
+	attrs = palloc0(sizeof(Datum) * desc->natts);
+	isnull = palloc0(sizeof(bool) * desc->natts);
+	free = palloc0(sizeof(bool) * desc->natts);
+
+	newtup = change->data.tp.newtuple;
+
+	heap_deform_tuple(&newtup->tuple, desc, attrs, isnull);
+
+	for (natt = 0; natt < desc->natts; natt++)
+	{
+		Form_pg_attribute attr = TupleDescAttr(desc, natt);
+		ReorderBufferToastEnt *ent;
+		struct varlena *varlena;
+
+		/* va_rawsize is the size of the original datum -- including header */
+		struct varatt_external toast_pointer;
+		struct varatt_indirect redirect_pointer;
+		struct varlena *new_datum = NULL;
+		struct varlena *reconstructed;
+		dlist_iter	it;
+		Size		data_done = 0;
+
+		/* system columns aren't toasted */
+		if (attr->attnum < 0)
+			continue;
+
+		if (attr->attisdropped)
+			continue;
+
+		/* not a varlena datatype */
+		if (attr->attlen != -1)
+			continue;
+
+		/* no data */
+		if (isnull[natt])
+			continue;
+
+		/* ok, we know we have a toast datum */
+		varlena = (struct varlena *) DatumGetPointer(attrs[natt]);
+
+		/* no need to do anything if the tuple isn't external */
+		if (!VARATT_IS_EXTERNAL(varlena))
+			continue;
+
+		VARATT_EXTERNAL_GET_POINTER(toast_pointer, varlena);
+
+		/*
+		 * Check whether the toast tuple changed, replace if so.
+		 */
+		ent = (ReorderBufferToastEnt *)
+			hash_search(txn->toast_hash,
+						(void *) &toast_pointer.va_valueid,
+						HASH_FIND,
+						NULL);
+		if (ent == NULL)
+			continue;
+
+		new_datum =
+			(struct varlena *) palloc0(INDIRECT_POINTER_SIZE);
+
+		free[natt] = true;
+
+		reconstructed = palloc0(toast_pointer.va_rawsize);
+
+		ent->reconstructed = reconstructed;
+
+		/* stitch toast tuple back together from its parts */
+		dlist_foreach(it, &ent->chunks)
+		{
+			bool		isnull;
+			ReorderBufferChange *cchange;
+			ReorderBufferTupleBuf *ctup;
+			Pointer		chunk;
+
+			cchange = dlist_container(ReorderBufferChange, node, it.cur);
+			ctup = cchange->data.tp.newtuple;
+			chunk = DatumGetPointer(fastgetattr(&ctup->tuple, 3, toast_desc, &isnull));
+
+			Assert(!isnull);
+			Assert(!VARATT_IS_EXTERNAL(chunk));
+			Assert(!VARATT_IS_SHORT(chunk));
+
+			memcpy(VARDATA(reconstructed) + data_done,
+				   VARDATA(chunk),
+				   VARSIZE(chunk) - VARHDRSZ);
+			data_done += VARSIZE(chunk) - VARHDRSZ;
+		}
+		Assert(data_done == VARATT_EXTERNAL_GET_EXTSIZE(toast_pointer));
+
+		/* make sure its marked as compressed or not */
+		if (VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer))
+			SET_VARSIZE_COMPRESSED(reconstructed, data_done + VARHDRSZ);
+		else
+			SET_VARSIZE(reconstructed, data_done + VARHDRSZ);
+
+		memset(&redirect_pointer, 0, sizeof(redirect_pointer));
+		redirect_pointer.pointer = reconstructed;
+
+		SET_VARTAG_EXTERNAL(new_datum, VARTAG_INDIRECT);
+		memcpy(VARDATA_EXTERNAL(new_datum), &redirect_pointer,
+			   sizeof(redirect_pointer));
+
+		attrs[natt] = PointerGetDatum(new_datum);
+	}
+
+	/*
+	 * Build tuple in separate memory & copy tuple back into the tuplebuf
+	 * passed to the output plugin. We can't directly heap_fill_tuple() into
+	 * the tuplebuf because attrs[] will point back into the current content.
+	 */
+	tmphtup = heap_form_tuple(desc, attrs, isnull);
+	Assert(newtup->tuple.t_len <= MaxHeapTupleSize);
+	Assert(ReorderBufferTupleBufData(newtup) == newtup->tuple.t_data);
+
+	memcpy(newtup->tuple.t_data, tmphtup->t_data, tmphtup->t_len);
+	newtup->tuple.t_len = tmphtup->t_len;
+
+	/*
+	 * free resources we won't further need, more persistent stuff will be
+	 * free'd in ReorderBufferToastReset().
+	 */
+	RelationClose(toast_rel);
+	pfree(tmphtup);
+	for (natt = 0; natt < desc->natts; natt++)
+	{
+		if (free[natt])
+			pfree(DatumGetPointer(attrs[natt]));
+	}
+	pfree(attrs);
+	pfree(free);
+	pfree(isnull);
+
+	MemoryContextSwitchTo(oldcontext);
+
+	/* subtract the old change size */
+	ReorderBufferChangeMemoryUpdate(rb, change, false, old_size);
+	/* now add the change back, with the correct size */
+	ReorderBufferChangeMemoryUpdate(rb, change, true,
+									ReorderBufferChangeSize(change));
+}
+
+/*
+ * Free all resources allocated for toast reconstruction.
+ */
+static void
+ReorderBufferToastReset(ReorderBuffer *rb, ReorderBufferTXN *txn)
+{
+	HASH_SEQ_STATUS hstat;
+	ReorderBufferToastEnt *ent;
+
+	if (txn->toast_hash == NULL)
+		return;
+
+	/* sequentially walk over the hash and free everything */
+	hash_seq_init(&hstat, txn->toast_hash);
+	while ((ent = (ReorderBufferToastEnt *) hash_seq_search(&hstat)) != NULL)
+	{
+		dlist_mutable_iter it;
+
+		if (ent->reconstructed != NULL)
+			pfree(ent->reconstructed);
+
+		dlist_foreach_modify(it, &ent->chunks)
+		{
+			ReorderBufferChange *change =
+			dlist_container(ReorderBufferChange, node, it.cur);
+
+			dlist_delete(&change->node);
+			ReorderBufferReturnChange(rb, change, true);
+		}
+	}
+
+	hash_destroy(txn->toast_hash);
+	txn->toast_hash = NULL;
+}
+
+
+/* ---------------------------------------
+ * Visibility support for logical decoding
+ *
+ *
+ * Lookup actual cmin/cmax values when using decoding snapshot. We can't
+ * always rely on stored cmin/cmax values because of two scenarios:
+ *
+ * * A tuple got changed multiple times during a single transaction and thus
+ *	 has got a combo CID. Combo CIDs are only valid for the duration of a
+ *	 single transaction.
+ * * A tuple with a cmin but no cmax (and thus no combo CID) got
+ *	 deleted/updated in another transaction than the one which created it
+ *	 which we are looking at right now. As only one of cmin, cmax or combo CID
+ *	 is actually stored in the heap we don't have access to the value we
+ *	 need anymore.
+ *
+ * To resolve those problems we have a per-transaction hash of (cmin,
+ * cmax) tuples keyed by (relfilenode, ctid) which contains the actual
+ * (cmin, cmax) values. That also takes care of combo CIDs by simply
+ * not caring about them at all. As we have the real cmin/cmax values
+ * combo CIDs aren't interesting.
+ *
+ * As we only care about catalog tuples here the overhead of this
+ * hashtable should be acceptable.
+ *
+ * Heap rewrites complicate this a bit, check rewriteheap.c for
+ * details.
+ * -------------------------------------------------------------------------
+ */
+
+/* struct for sorting mapping files by LSN efficiently */
+typedef struct RewriteMappingFile
+{
+	XLogRecPtr	lsn;
+	char		fname[MAXPGPATH];
+} RewriteMappingFile;
+
+#ifdef NOT_USED
+static void
+DisplayMapping(HTAB *tuplecid_data)
+{
+	HASH_SEQ_STATUS hstat;
+	ReorderBufferTupleCidEnt *ent;
+
+	hash_seq_init(&hstat, tuplecid_data);
+	while ((ent = (ReorderBufferTupleCidEnt *) hash_seq_search(&hstat)) != NULL)
+	{
+		elog(DEBUG3, "mapping: node: %u/%u/%u tid: %u/%u cmin: %u, cmax: %u",
+			 ent->key.relnode.dbNode,
+			 ent->key.relnode.spcNode,
+			 ent->key.relnode.relNode,
+			 ItemPointerGetBlockNumber(&ent->key.tid),
+			 ItemPointerGetOffsetNumber(&ent->key.tid),
+			 ent->cmin,
+			 ent->cmax
+			);
+	}
+}
+#endif
+
+/*
+ * Apply a single mapping file to tuplecid_data.
+ *
+ * The mapping file has to have been verified to be a) committed b) for our
+ * transaction c) applied in LSN order.
+ */
+static void
+ApplyLogicalMappingFile(HTAB *tuplecid_data, Oid relid, const char *fname)
+{
+	char		path[MAXPGPATH];
+	int			fd;
+	int			readBytes;
+	LogicalRewriteMappingData map;
+
+	sprintf(path, "pg_logical/mappings/%s", fname);
+	fd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
+	if (fd < 0)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not open file \"%s\": %m", path)));
+
+	while (true)
+	{
+		ReorderBufferTupleCidKey key;
+		ReorderBufferTupleCidEnt *ent;
+		ReorderBufferTupleCidEnt *new_ent;
+		bool		found;
+
+		/* be careful about padding */
+		memset(&key, 0, sizeof(ReorderBufferTupleCidKey));
+
+		/* read all mappings till the end of the file */
+		pgstat_report_wait_start(WAIT_EVENT_REORDER_LOGICAL_MAPPING_READ);
+		readBytes = read(fd, &map, sizeof(LogicalRewriteMappingData));
+		pgstat_report_wait_end();
+
+		if (readBytes < 0)
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not read file \"%s\": %m",
+							path)));
+		else if (readBytes == 0)	/* EOF */
+			break;
+		else if (readBytes != sizeof(LogicalRewriteMappingData))
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not read from file \"%s\": read %d instead of %d bytes",
+							path, readBytes,
+							(int32) sizeof(LogicalRewriteMappingData))));
+
+		key.relnode = map.old_node;
+		ItemPointerCopy(&map.old_tid,
+						&key.tid);
+
+
+		ent = (ReorderBufferTupleCidEnt *)
+			hash_search(tuplecid_data,
+						(void *) &key,
+						HASH_FIND,
+						NULL);
+
+		/* no existing mapping, no need to update */
+		if (!ent)
+			continue;
+
+		key.relnode = map.new_node;
+		ItemPointerCopy(&map.new_tid,
+						&key.tid);
+
+		new_ent = (ReorderBufferTupleCidEnt *)
+			hash_search(tuplecid_data,
+						(void *) &key,
+						HASH_ENTER,
+						&found);
+
+		if (found)
+		{
+			/*
+			 * Make sure the existing mapping makes sense. We sometime update
+			 * old records that did not yet have a cmax (e.g. pg_class' own
+			 * entry while rewriting it) during rewrites, so allow that.
+			 */
+			Assert(ent->cmin == InvalidCommandId || ent->cmin == new_ent->cmin);
+			Assert(ent->cmax == InvalidCommandId || ent->cmax == new_ent->cmax);
+		}
+		else
+		{
+			/* update mapping */
+			new_ent->cmin = ent->cmin;
+			new_ent->cmax = ent->cmax;
+			new_ent->combocid = ent->combocid;
+		}
+	}
+
+	if (CloseTransientFile(fd) != 0)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not close file \"%s\": %m", path)));
+}
+
+
+/*
+ * Check whether the TransactionId 'xid' is in the pre-sorted array 'xip'.
+ */
+static bool
+TransactionIdInArray(TransactionId xid, TransactionId *xip, Size num)
+{
+	return bsearch(&xid, xip, num,
+				   sizeof(TransactionId), xidComparator) != NULL;
+}
+
+/*
+ * list_sort() comparator for sorting RewriteMappingFiles in LSN order.
+ */
+static int
+file_sort_by_lsn(const ListCell *a_p, const ListCell *b_p)
+{
+	RewriteMappingFile *a = (RewriteMappingFile *) lfirst(a_p);
+	RewriteMappingFile *b = (RewriteMappingFile *) lfirst(b_p);
+
+	if (a->lsn < b->lsn)
+		return -1;
+	else if (a->lsn > b->lsn)
+		return 1;
+	return 0;
+}
+
+/*
+ * Apply any existing logical remapping files if there are any targeted at our
+ * transaction for relid.
+ */
+static void
+UpdateLogicalMappings(HTAB *tuplecid_data, Oid relid, Snapshot snapshot)
+{
+	DIR		   *mapping_dir;
+	struct dirent *mapping_de;
+	List	   *files = NIL;
+	ListCell   *file;
+	Oid			dboid = IsSharedRelation(relid) ? InvalidOid : MyDatabaseId;
+
+	mapping_dir = AllocateDir("pg_logical/mappings");
+	while ((mapping_de = ReadDir(mapping_dir, "pg_logical/mappings")) != NULL)
+	{
+		Oid			f_dboid;
+		Oid			f_relid;
+		TransactionId f_mapped_xid;
+		TransactionId f_create_xid;
+		XLogRecPtr	f_lsn;
+		uint32		f_hi,
+					f_lo;
+		RewriteMappingFile *f;
+
+		if (strcmp(mapping_de->d_name, ".") == 0 ||
+			strcmp(mapping_de->d_name, "..") == 0)
+			continue;
+
+		/* Ignore files that aren't ours */
+		if (strncmp(mapping_de->d_name, "map-", 4) != 0)
+			continue;
+
+		if (sscanf(mapping_de->d_name, LOGICAL_REWRITE_FORMAT,
+				   &f_dboid, &f_relid, &f_hi, &f_lo,
+				   &f_mapped_xid, &f_create_xid) != 6)
+			elog(ERROR, "could not parse filename \"%s\"", mapping_de->d_name);
+
+		f_lsn = ((uint64) f_hi) << 32 | f_lo;
+
+		/* mapping for another database */
+		if (f_dboid != dboid)
+			continue;
+
+		/* mapping for another relation */
+		if (f_relid != relid)
+			continue;
+
+		/* did the creating transaction abort? */
+		if (!TransactionIdDidCommit(f_create_xid))
+			continue;
+
+		/* not for our transaction */
+		if (!TransactionIdInArray(f_mapped_xid, snapshot->subxip, snapshot->subxcnt))
+			continue;
+
+		/* ok, relevant, queue for apply */
+		f = palloc(sizeof(RewriteMappingFile));
+		f->lsn = f_lsn;
+		strcpy(f->fname, mapping_de->d_name);
+		files = lappend(files, f);
+	}
+	FreeDir(mapping_dir);
+
+	/* sort files so we apply them in LSN order */
+	list_sort(files, file_sort_by_lsn);
+
+	foreach(file, files)
+	{
+		RewriteMappingFile *f = (RewriteMappingFile *) lfirst(file);
+
+		elog(DEBUG1, "applying mapping: \"%s\" in %u", f->fname,
+			 snapshot->subxip[0]);
+		ApplyLogicalMappingFile(tuplecid_data, relid, f->fname);
+		pfree(f);
+	}
+}
+
+/*
+ * Lookup cmin/cmax of a tuple, during logical decoding where we can't rely on
+ * combo CIDs.
+ */
+bool
+ResolveCminCmaxDuringDecoding(HTAB *tuplecid_data,
+							  Snapshot snapshot,
+							  HeapTuple htup, Buffer buffer,
+							  CommandId *cmin, CommandId *cmax)
+{
+	ReorderBufferTupleCidKey key;
+	ReorderBufferTupleCidEnt *ent;
+	ForkNumber	forkno;
+	BlockNumber blockno;
+	bool		updated_mapping = false;
+
+	/*
+	 * Return unresolved if tuplecid_data is not valid.  That's because when
+	 * streaming in-progress transactions we may run into tuples with the CID
+	 * before actually decoding them.  Think e.g. about INSERT followed by
+	 * TRUNCATE, where the TRUNCATE may not be decoded yet when applying the
+	 * INSERT.  So in such cases, we assume the CID is from the future
+	 * command.
+	 */
+	if (tuplecid_data == NULL)
+		return false;
+
+	/* be careful about padding */
+	memset(&key, 0, sizeof(key));
+
+	Assert(!BufferIsLocal(buffer));
+
+	/*
+	 * get relfilenode from the buffer, no convenient way to access it other
+	 * than that.
+	 */
+	BufferGetTag(buffer, &key.relnode, &forkno, &blockno);
+
+	/* tuples can only be in the main fork */
+	Assert(forkno == MAIN_FORKNUM);
+	Assert(blockno == ItemPointerGetBlockNumber(&htup->t_self));
+
+	ItemPointerCopy(&htup->t_self,
+					&key.tid);
+
+restart:
+	ent = (ReorderBufferTupleCidEnt *)
+		hash_search(tuplecid_data,
+					(void *) &key,
+					HASH_FIND,
+					NULL);
+
+	/*
+	 * failed to find a mapping, check whether the table was rewritten and
+	 * apply mapping if so, but only do that once - there can be no new
+	 * mappings while we are in here since we have to hold a lock on the
+	 * relation.
+	 */
+	if (ent == NULL && !updated_mapping)
+	{
+		UpdateLogicalMappings(tuplecid_data, htup->t_tableOid, snapshot);
+		/* now check but don't update for a mapping again */
+		updated_mapping = true;
+		goto restart;
+	}
+	else if (ent == NULL)
+		return false;
+
+	if (cmin)
+		*cmin = ent->cmin;
+	if (cmax)
+		*cmax = ent->cmax;
+	return true;
+}
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
new file mode 100644
index 0000000..6df6024
--- /dev/null
+++ b/src/backend/replication/logical/snapbuild.c
@@ -0,0 +1,1995 @@
+/*-------------------------------------------------------------------------
+ *
+ * snapbuild.c
+ *
+ *	  Infrastructure for building historic catalog snapshots based on contents
+ *	  of the WAL, for the purpose of decoding heapam.c style values in the
+ *	  WAL.
+ *
+ * NOTES:
+ *
+ * We build snapshots which can *only* be used to read catalog contents and we
+ * do so by reading and interpreting the WAL stream. The aim is to build a
+ * snapshot that behaves the same as a freshly taken MVCC snapshot would have
+ * at the time the XLogRecord was generated.
+ *
+ * To build the snapshots we reuse the infrastructure built for Hot
+ * Standby. The in-memory snapshots we build look different than HS' because
+ * we have different needs. To successfully decode data from the WAL we only
+ * need to access catalog tables and (sys|rel|cat)cache, not the actual user
+ * tables since the data we decode is wholly contained in the WAL
+ * records. Also, our snapshots need to be different in comparison to normal
+ * MVCC ones because in contrast to those we cannot fully rely on the clog and
+ * pg_subtrans for information about committed transactions because they might
+ * commit in the future from the POV of the WAL entry we're currently
+ * decoding. This definition has the advantage that we only need to prevent
+ * removal of catalog rows, while normal table's rows can still be
+ * removed. This is achieved by using the replication slot mechanism.
+ *
+ * As the percentage of transactions modifying the catalog normally is fairly
+ * small in comparisons to ones only manipulating user data, we keep track of
+ * the committed catalog modifying ones inside [xmin, xmax) instead of keeping
+ * track of all running transactions like it's done in a normal snapshot. Note
+ * that we're generally only looking at transactions that have acquired an
+ * xid. That is we keep a list of transactions between snapshot->(xmin, xmax)
+ * that we consider committed, everything else is considered aborted/in
+ * progress. That also allows us not to care about subtransactions before they
+ * have committed which means this module, in contrast to HS, doesn't have to
+ * care about suboverflowed subtransactions and similar.
+ *
+ * One complexity of doing this is that to e.g. handle mixed DDL/DML
+ * transactions we need Snapshots that see intermediate versions of the
+ * catalog in a transaction. During normal operation this is achieved by using
+ * CommandIds/cmin/cmax. The problem with that however is that for space
+ * efficiency reasons only one value of that is stored
+ * (cf. combocid.c). Since combo CIDs are only available in memory we log
+ * additional information which allows us to get the original (cmin, cmax)
+ * pair during visibility checks. Check the reorderbuffer.c's comment above
+ * ResolveCminCmaxDuringDecoding() for details.
+ *
+ * To facilitate all this we need our own visibility routine, as the normal
+ * ones are optimized for different usecases.
+ *
+ * To replace the normal catalog snapshots with decoding ones use the
+ * SetupHistoricSnapshot() and TeardownHistoricSnapshot() functions.
+ *
+ *
+ *
+ * The snapbuild machinery is starting up in several stages, as illustrated
+ * by the following graph describing the SnapBuild->state transitions:
+ *
+ *		   +-------------------------+
+ *	  +----|		 START			 |-------------+
+ *	  |    +-------------------------+			   |
+ *	  |					|						   |
+ *	  |					|						   |
+ *	  |		   running_xacts #1					   |
+ *	  |					|						   |
+ *	  |					|						   |
+ *	  |					v						   |
+ *	  |    +-------------------------+			   v
+ *	  |    |   BUILDING_SNAPSHOT	 |------------>|
+ *	  |    +-------------------------+			   |
+ *	  |					|						   |
+ *	  |					|						   |
+ *	  | running_xacts #2, xacts from #1 finished   |
+ *	  |					|						   |
+ *	  |					|						   |
+ *	  |					v						   |
+ *	  |    +-------------------------+			   v
+ *	  |    |	   FULL_SNAPSHOT	 |------------>|
+ *	  |    +-------------------------+			   |
+ *	  |					|						   |
+ * running_xacts		|					   saved snapshot
+ * with zero xacts		|				  at running_xacts's lsn
+ *	  |					|						   |
+ *	  | running_xacts with xacts from #2 finished  |
+ *	  |					|						   |
+ *	  |					v						   |
+ *	  |    +-------------------------+			   |
+ *	  +--->|SNAPBUILD_CONSISTENT	 |<------------+
+ *		   +-------------------------+
+ *
+ * Initially the machinery is in the START stage. When an xl_running_xacts
+ * record is read that is sufficiently new (above the safe xmin horizon),
+ * there's a state transition. If there were no running xacts when the
+ * running_xacts record was generated, we'll directly go into CONSISTENT
+ * state, otherwise we'll switch to the BUILDING_SNAPSHOT state. Having a full
+ * snapshot means that all transactions that start henceforth can be decoded
+ * in their entirety, but transactions that started previously can't. In
+ * FULL_SNAPSHOT we'll switch into CONSISTENT once all those previously
+ * running transactions have committed or aborted.
+ *
+ * Only transactions that commit after CONSISTENT state has been reached will
+ * be replayed, even though they might have started while still in
+ * FULL_SNAPSHOT. That ensures that we'll reach a point where no previous
+ * changes has been exported, but all the following ones will be. That point
+ * is a convenient point to initialize replication from, which is why we
+ * export a snapshot at that point, which *can* be used to read normal data.
+ *
+ * Copyright (c) 2012-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/snapbuild.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "access/heapam_xlog.h"
+#include "access/transam.h"
+#include "access/xact.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "replication/logical.h"
+#include "replication/reorderbuffer.h"
+#include "replication/snapbuild.h"
+#include "storage/block.h"		/* debugging output */
+#include "storage/fd.h"
+#include "storage/lmgr.h"
+#include "storage/proc.h"
+#include "storage/procarray.h"
+#include "storage/standby.h"
+#include "utils/builtins.h"
+#include "utils/memutils.h"
+#include "utils/snapmgr.h"
+#include "utils/snapshot.h"
+
+/*
+ * This struct contains the current state of the snapshot building
+ * machinery. Besides a forward declaration in the header, it is not exposed
+ * to the public, so we can easily change its contents.
+ */
+struct SnapBuild
+{
+	/* how far are we along building our first full snapshot */
+	SnapBuildState state;
+
+	/* private memory context used to allocate memory for this module. */
+	MemoryContext context;
+
+	/* all transactions < than this have committed/aborted */
+	TransactionId xmin;
+
+	/* all transactions >= than this are uncommitted */
+	TransactionId xmax;
+
+	/*
+	 * Don't replay commits from an LSN < this LSN. This can be set externally
+	 * but it will also be advanced (never retreat) from within snapbuild.c.
+	 */
+	XLogRecPtr	start_decoding_at;
+
+	/*
+	 * LSN at which we found a consistent point at the time of slot creation.
+	 * This is also the point where we have exported a snapshot for the
+	 * initial copy.
+	 *
+	 * The prepared transactions that are not covered by initial snapshot
+	 * needs to be sent later along with commit prepared and they must be
+	 * before this point.
+	 */
+	XLogRecPtr	initial_consistent_point;
+
+	/*
+	 * Don't start decoding WAL until the "xl_running_xacts" information
+	 * indicates there are no running xids with an xid smaller than this.
+	 */
+	TransactionId initial_xmin_horizon;
+
+	/* Indicates if we are building full snapshot or just catalog one. */
+	bool		building_full_snapshot;
+
+	/*
+	 * Snapshot that's valid to see the catalog state seen at this moment.
+	 */
+	Snapshot	snapshot;
+
+	/*
+	 * LSN of the last location we are sure a snapshot has been serialized to.
+	 */
+	XLogRecPtr	last_serialized_snapshot;
+
+	/*
+	 * The reorderbuffer we need to update with usable snapshots et al.
+	 */
+	ReorderBuffer *reorder;
+
+	/*
+	 * TransactionId at which the next phase of initial snapshot building will
+	 * happen. InvalidTransactionId if not known (i.e. SNAPBUILD_START), or
+	 * when no next phase necessary (SNAPBUILD_CONSISTENT).
+	 */
+	TransactionId next_phase_at;
+
+	/*
+	 * Array of transactions which could have catalog changes that committed
+	 * between xmin and xmax.
+	 */
+	struct
+	{
+		/* number of committed transactions */
+		size_t		xcnt;
+
+		/* available space for committed transactions */
+		size_t		xcnt_space;
+
+		/*
+		 * Until we reach a CONSISTENT state, we record commits of all
+		 * transactions, not just the catalog changing ones. Record when that
+		 * changes so we know we cannot export a snapshot safely anymore.
+		 */
+		bool		includes_all_transactions;
+
+		/*
+		 * Array of committed transactions that have modified the catalog.
+		 *
+		 * As this array is frequently modified we do *not* keep it in
+		 * xidComparator order. Instead we sort the array when building &
+		 * distributing a snapshot.
+		 *
+		 * TODO: It's unclear whether that reasoning has much merit. Every
+		 * time we add something here after becoming consistent will also
+		 * require distributing a snapshot. Storing them sorted would
+		 * potentially also make it easier to purge (but more complicated wrt
+		 * wraparound?). Should be improved if sorting while building the
+		 * snapshot shows up in profiles.
+		 */
+		TransactionId *xip;
+	}			committed;
+};
+
+/*
+ * Starting a transaction -- which we need to do while exporting a snapshot --
+ * removes knowledge about the previously used resowner, so we save it here.
+ */
+static ResourceOwner SavedResourceOwnerDuringExport = NULL;
+static bool ExportInProgress = false;
+
+/* ->committed manipulation */
+static void SnapBuildPurgeCommittedTxn(SnapBuild *builder);
+
+/* snapshot building/manipulation/distribution functions */
+static Snapshot SnapBuildBuildSnapshot(SnapBuild *builder);
+
+static void SnapBuildFreeSnapshot(Snapshot snap);
+
+static void SnapBuildSnapIncRefcount(Snapshot snap);
+
+static void SnapBuildDistributeNewCatalogSnapshot(SnapBuild *builder, XLogRecPtr lsn);
+
+/* xlog reading helper functions for SnapBuildProcessRunningXacts */
+static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running);
+static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff);
+
+/* serialization functions */
+static void SnapBuildSerialize(SnapBuild *builder, XLogRecPtr lsn);
+static bool SnapBuildRestore(SnapBuild *builder, XLogRecPtr lsn);
+
+/*
+ * Allocate a new snapshot builder.
+ *
+ * xmin_horizon is the xid >= which we can be sure no catalog rows have been
+ * removed, start_lsn is the LSN >= we want to replay commits.
+ */
+SnapBuild *
+AllocateSnapshotBuilder(ReorderBuffer *reorder,
+						TransactionId xmin_horizon,
+						XLogRecPtr start_lsn,
+						bool need_full_snapshot,
+						XLogRecPtr initial_consistent_point)
+{
+	MemoryContext context;
+	MemoryContext oldcontext;
+	SnapBuild  *builder;
+
+	/* allocate memory in own context, to have better accountability */
+	context = AllocSetContextCreate(CurrentMemoryContext,
+									"snapshot builder context",
+									ALLOCSET_DEFAULT_SIZES);
+	oldcontext = MemoryContextSwitchTo(context);
+
+	builder = palloc0(sizeof(SnapBuild));
+
+	builder->state = SNAPBUILD_START;
+	builder->context = context;
+	builder->reorder = reorder;
+	/* Other struct members initialized by zeroing via palloc0 above */
+
+	builder->committed.xcnt = 0;
+	builder->committed.xcnt_space = 128;	/* arbitrary number */
+	builder->committed.xip =
+		palloc0(builder->committed.xcnt_space * sizeof(TransactionId));
+	builder->committed.includes_all_transactions = true;
+
+	builder->initial_xmin_horizon = xmin_horizon;
+	builder->start_decoding_at = start_lsn;
+	builder->building_full_snapshot = need_full_snapshot;
+	builder->initial_consistent_point = initial_consistent_point;
+
+	MemoryContextSwitchTo(oldcontext);
+
+	return builder;
+}
+
+/*
+ * Free a snapshot builder.
+ */
+void
+FreeSnapshotBuilder(SnapBuild *builder)
+{
+	MemoryContext context = builder->context;
+
+	/* free snapshot explicitly, that contains some error checking */
+	if (builder->snapshot != NULL)
+	{
+		SnapBuildSnapDecRefcount(builder->snapshot);
+		builder->snapshot = NULL;
+	}
+
+	/* other resources are deallocated via memory context reset */
+	MemoryContextDelete(context);
+}
+
+/*
+ * Free an unreferenced snapshot that has previously been built by us.
+ */
+static void
+SnapBuildFreeSnapshot(Snapshot snap)
+{
+	/* make sure we don't get passed an external snapshot */
+	Assert(snap->snapshot_type == SNAPSHOT_HISTORIC_MVCC);
+
+	/* make sure nobody modified our snapshot */
+	Assert(snap->curcid == FirstCommandId);
+	Assert(!snap->suboverflowed);
+	Assert(!snap->takenDuringRecovery);
+	Assert(snap->regd_count == 0);
+
+	/* slightly more likely, so it's checked even without c-asserts */
+	if (snap->copied)
+		elog(ERROR, "cannot free a copied snapshot");
+
+	if (snap->active_count)
+		elog(ERROR, "cannot free an active snapshot");
+
+	pfree(snap);
+}
+
+/*
+ * In which state of snapshot building are we?
+ */
+SnapBuildState
+SnapBuildCurrentState(SnapBuild *builder)
+{
+	return builder->state;
+}
+
+/*
+ * Return the LSN at which the snapshot was exported
+ */
+XLogRecPtr
+SnapBuildInitialConsistentPoint(SnapBuild *builder)
+{
+	return builder->initial_consistent_point;
+}
+
+/*
+ * Should the contents of transaction ending at 'ptr' be decoded?
+ */
+bool
+SnapBuildXactNeedsSkip(SnapBuild *builder, XLogRecPtr ptr)
+{
+	return ptr < builder->start_decoding_at;
+}
+
+/*
+ * Increase refcount of a snapshot.
+ *
+ * This is used when handing out a snapshot to some external resource or when
+ * adding a Snapshot as builder->snapshot.
+ */
+static void
+SnapBuildSnapIncRefcount(Snapshot snap)
+{
+	snap->active_count++;
+}
+
+/*
+ * Decrease refcount of a snapshot and free if the refcount reaches zero.
+ *
+ * Externally visible, so that external resources that have been handed an
+ * IncRef'ed Snapshot can adjust its refcount easily.
+ */
+void
+SnapBuildSnapDecRefcount(Snapshot snap)
+{
+	/* make sure we don't get passed an external snapshot */
+	Assert(snap->snapshot_type == SNAPSHOT_HISTORIC_MVCC);
+
+	/* make sure nobody modified our snapshot */
+	Assert(snap->curcid == FirstCommandId);
+	Assert(!snap->suboverflowed);
+	Assert(!snap->takenDuringRecovery);
+
+	Assert(snap->regd_count == 0);
+
+	Assert(snap->active_count > 0);
+
+	/* slightly more likely, so it's checked even without casserts */
+	if (snap->copied)
+		elog(ERROR, "cannot free a copied snapshot");
+
+	snap->active_count--;
+	if (snap->active_count == 0)
+		SnapBuildFreeSnapshot(snap);
+}
+
+/*
+ * Build a new snapshot, based on currently committed catalog-modifying
+ * transactions.
+ *
+ * In-progress transactions with catalog access are *not* allowed to modify
+ * these snapshots; they have to copy them and fill in appropriate ->curcid
+ * and ->subxip/subxcnt values.
+ */
+static Snapshot
+SnapBuildBuildSnapshot(SnapBuild *builder)
+{
+	Snapshot	snapshot;
+	Size		ssize;
+
+	Assert(builder->state >= SNAPBUILD_FULL_SNAPSHOT);
+
+	ssize = sizeof(SnapshotData)
+		+ sizeof(TransactionId) * builder->committed.xcnt
+		+ sizeof(TransactionId) * 1 /* toplevel xid */ ;
+
+	snapshot = MemoryContextAllocZero(builder->context, ssize);
+
+	snapshot->snapshot_type = SNAPSHOT_HISTORIC_MVCC;
+
+	/*
+	 * We misuse the original meaning of SnapshotData's xip and subxip fields
+	 * to make the more fitting for our needs.
+	 *
+	 * In the 'xip' array we store transactions that have to be treated as
+	 * committed. Since we will only ever look at tuples from transactions
+	 * that have modified the catalog it's more efficient to store those few
+	 * that exist between xmin and xmax (frequently there are none).
+	 *
+	 * Snapshots that are used in transactions that have modified the catalog
+	 * also use the 'subxip' array to store their toplevel xid and all the
+	 * subtransaction xids so we can recognize when we need to treat rows as
+	 * visible that are not in xip but still need to be visible. Subxip only
+	 * gets filled when the transaction is copied into the context of a
+	 * catalog modifying transaction since we otherwise share a snapshot
+	 * between transactions. As long as a txn hasn't modified the catalog it
+	 * doesn't need to treat any uncommitted rows as visible, so there is no
+	 * need for those xids.
+	 *
+	 * Both arrays are qsort'ed so that we can use bsearch() on them.
+	 */
+	Assert(TransactionIdIsNormal(builder->xmin));
+	Assert(TransactionIdIsNormal(builder->xmax));
+
+	snapshot->xmin = builder->xmin;
+	snapshot->xmax = builder->xmax;
+
+	/* store all transactions to be treated as committed by this snapshot */
+	snapshot->xip =
+		(TransactionId *) ((char *) snapshot + sizeof(SnapshotData));
+	snapshot->xcnt = builder->committed.xcnt;
+	memcpy(snapshot->xip,
+		   builder->committed.xip,
+		   builder->committed.xcnt * sizeof(TransactionId));
+
+	/* sort so we can bsearch() */
+	qsort(snapshot->xip, snapshot->xcnt, sizeof(TransactionId), xidComparator);
+
+	/*
+	 * Initially, subxip is empty, i.e. it's a snapshot to be used by
+	 * transactions that don't modify the catalog. Will be filled by
+	 * ReorderBufferCopySnap() if necessary.
+	 */
+	snapshot->subxcnt = 0;
+	snapshot->subxip = NULL;
+
+	snapshot->suboverflowed = false;
+	snapshot->takenDuringRecovery = false;
+	snapshot->copied = false;
+	snapshot->curcid = FirstCommandId;
+	snapshot->active_count = 0;
+	snapshot->regd_count = 0;
+	snapshot->snapXactCompletionCount = 0;
+
+	return snapshot;
+}
+
+/*
+ * Build the initial slot snapshot and convert it to a normal snapshot that
+ * is understood by HeapTupleSatisfiesMVCC.
+ *
+ * The snapshot will be usable directly in current transaction or exported
+ * for loading in different transaction.
+ */
+Snapshot
+SnapBuildInitialSnapshot(SnapBuild *builder)
+{
+	Snapshot	snap;
+	TransactionId xid;
+	TransactionId *newxip;
+	int			newxcnt = 0;
+
+	Assert(!FirstSnapshotSet);
+	Assert(XactIsoLevel == XACT_REPEATABLE_READ);
+
+	if (builder->state != SNAPBUILD_CONSISTENT)
+		elog(ERROR, "cannot build an initial slot snapshot before reaching a consistent state");
+
+	if (!builder->committed.includes_all_transactions)
+		elog(ERROR, "cannot build an initial slot snapshot, not all transactions are monitored anymore");
+
+	/* so we don't overwrite the existing value */
+	if (TransactionIdIsValid(MyProc->xmin))
+		elog(ERROR, "cannot build an initial slot snapshot when MyProc->xmin already is valid");
+
+	snap = SnapBuildBuildSnapshot(builder);
+
+	/*
+	 * We know that snap->xmin is alive, enforced by the logical xmin
+	 * mechanism. Due to that we can do this without locks, we're only
+	 * changing our own value.
+	 */
+#ifdef USE_ASSERT_CHECKING
+	{
+		TransactionId safeXid;
+
+		LWLockAcquire(ProcArrayLock, LW_SHARED);
+		safeXid = GetOldestSafeDecodingTransactionId(false);
+		LWLockRelease(ProcArrayLock);
+
+		Assert(TransactionIdPrecedesOrEquals(safeXid, snap->xmin));
+	}
+#endif
+
+	MyProc->xmin = snap->xmin;
+
+	/* allocate in transaction context */
+	newxip = (TransactionId *)
+		palloc(sizeof(TransactionId) * GetMaxSnapshotXidCount());
+
+	/*
+	 * snapbuild.c builds transactions in an "inverted" manner, which means it
+	 * stores committed transactions in ->xip, not ones in progress. Build a
+	 * classical snapshot by marking all non-committed transactions as
+	 * in-progress. This can be expensive.
+	 */
+	for (xid = snap->xmin; NormalTransactionIdPrecedes(xid, snap->xmax);)
+	{
+		void	   *test;
+
+		/*
+		 * Check whether transaction committed using the decoding snapshot
+		 * meaning of ->xip.
+		 */
+		test = bsearch(&xid, snap->xip, snap->xcnt,
+					   sizeof(TransactionId), xidComparator);
+
+		if (test == NULL)
+		{
+			if (newxcnt >= GetMaxSnapshotXidCount())
+				ereport(ERROR,
+						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
+						 errmsg("initial slot snapshot too large")));
+
+			newxip[newxcnt++] = xid;
+		}
+
+		TransactionIdAdvance(xid);
+	}
+
+	/* adjust remaining snapshot fields as needed */
+	snap->snapshot_type = SNAPSHOT_MVCC;
+	snap->xcnt = newxcnt;
+	snap->xip = newxip;
+
+	return snap;
+}
+
+/*
+ * Export a snapshot so it can be set in another session with SET TRANSACTION
+ * SNAPSHOT.
+ *
+ * For that we need to start a transaction in the current backend as the
+ * importing side checks whether the source transaction is still open to make
+ * sure the xmin horizon hasn't advanced since then.
+ */
+const char *
+SnapBuildExportSnapshot(SnapBuild *builder)
+{
+	Snapshot	snap;
+	char	   *snapname;
+
+	if (IsTransactionOrTransactionBlock())
+		elog(ERROR, "cannot export a snapshot from within a transaction");
+
+	if (SavedResourceOwnerDuringExport)
+		elog(ERROR, "can only export one snapshot at a time");
+
+	SavedResourceOwnerDuringExport = CurrentResourceOwner;
+	ExportInProgress = true;
+
+	StartTransactionCommand();
+
+	/* There doesn't seem to a nice API to set these */
+	XactIsoLevel = XACT_REPEATABLE_READ;
+	XactReadOnly = true;
+
+	snap = SnapBuildInitialSnapshot(builder);
+
+	/*
+	 * now that we've built a plain snapshot, make it active and use the
+	 * normal mechanisms for exporting it
+	 */
+	snapname = ExportSnapshot(snap);
+
+	ereport(LOG,
+			(errmsg_plural("exported logical decoding snapshot: \"%s\" with %u transaction ID",
+						   "exported logical decoding snapshot: \"%s\" with %u transaction IDs",
+						   snap->xcnt,
+						   snapname, snap->xcnt)));
+	return snapname;
+}
+
+/*
+ * Ensure there is a snapshot and if not build one for current transaction.
+ */
+Snapshot
+SnapBuildGetOrBuildSnapshot(SnapBuild *builder, TransactionId xid)
+{
+	Assert(builder->state == SNAPBUILD_CONSISTENT);
+
+	/* only build a new snapshot if we don't have a prebuilt one */
+	if (builder->snapshot == NULL)
+	{
+		builder->snapshot = SnapBuildBuildSnapshot(builder);
+		/* increase refcount for the snapshot builder */
+		SnapBuildSnapIncRefcount(builder->snapshot);
+	}
+
+	return builder->snapshot;
+}
+
+/*
+ * Reset a previously SnapBuildExportSnapshot()'ed snapshot if there is
+ * any. Aborts the previously started transaction and resets the resource
+ * owner back to its original value.
+ */
+void
+SnapBuildClearExportedSnapshot(void)
+{
+	ResourceOwner tmpResOwner;
+
+	/* nothing exported, that is the usual case */
+	if (!ExportInProgress)
+		return;
+
+	if (!IsTransactionState())
+		elog(ERROR, "clearing exported snapshot in wrong transaction state");
+
+	/*
+	 * AbortCurrentTransaction() takes care of resetting the snapshot state,
+	 * so remember SavedResourceOwnerDuringExport.
+	 */
+	tmpResOwner = SavedResourceOwnerDuringExport;
+
+	/* make sure nothing could have ever happened */
+	AbortCurrentTransaction();
+
+	CurrentResourceOwner = tmpResOwner;
+}
+
+/*
+ * Clear snapshot export state during transaction abort.
+ */
+void
+SnapBuildResetExportedSnapshotState(void)
+{
+	SavedResourceOwnerDuringExport = NULL;
+	ExportInProgress = false;
+}
+
+/*
+ * Handle the effects of a single heap change, appropriate to the current state
+ * of the snapshot builder and returns whether changes made at (xid, lsn) can
+ * be decoded.
+ */
+bool
+SnapBuildProcessChange(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn)
+{
+	/*
+	 * We can't handle data in transactions if we haven't built a snapshot
+	 * yet, so don't store them.
+	 */
+	if (builder->state < SNAPBUILD_FULL_SNAPSHOT)
+		return false;
+
+	/*
+	 * No point in keeping track of changes in transactions that we don't have
+	 * enough information about to decode. This means that they started before
+	 * we got into the SNAPBUILD_FULL_SNAPSHOT state.
+	 */
+	if (builder->state < SNAPBUILD_CONSISTENT &&
+		TransactionIdPrecedes(xid, builder->next_phase_at))
+		return false;
+
+	/*
+	 * If the reorderbuffer doesn't yet have a snapshot, add one now, it will
+	 * be needed to decode the change we're currently processing.
+	 */
+	if (!ReorderBufferXidHasBaseSnapshot(builder->reorder, xid))
+	{
+		/* only build a new snapshot if we don't have a prebuilt one */
+		if (builder->snapshot == NULL)
+		{
+			builder->snapshot = SnapBuildBuildSnapshot(builder);
+			/* increase refcount for the snapshot builder */
+			SnapBuildSnapIncRefcount(builder->snapshot);
+		}
+
+		/*
+		 * Increase refcount for the transaction we're handing the snapshot
+		 * out to.
+		 */
+		SnapBuildSnapIncRefcount(builder->snapshot);
+		ReorderBufferSetBaseSnapshot(builder->reorder, xid, lsn,
+									 builder->snapshot);
+	}
+
+	return true;
+}
+
+/*
+ * Do CommandId/combo CID handling after reading an xl_heap_new_cid record.
+ * This implies that a transaction has done some form of write to system
+ * catalogs.
+ */
+void
+SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid,
+					   XLogRecPtr lsn, xl_heap_new_cid *xlrec)
+{
+	CommandId	cid;
+
+	/*
+	 * we only log new_cid's if a catalog tuple was modified, so mark the
+	 * transaction as containing catalog modifications
+	 */
+	ReorderBufferXidSetCatalogChanges(builder->reorder, xid, lsn);
+
+	ReorderBufferAddNewTupleCids(builder->reorder, xlrec->top_xid, lsn,
+								 xlrec->target_node, xlrec->target_tid,
+								 xlrec->cmin, xlrec->cmax,
+								 xlrec->combocid);
+
+	/* figure out new command id */
+	if (xlrec->cmin != InvalidCommandId &&
+		xlrec->cmax != InvalidCommandId)
+		cid = Max(xlrec->cmin, xlrec->cmax);
+	else if (xlrec->cmax != InvalidCommandId)
+		cid = xlrec->cmax;
+	else if (xlrec->cmin != InvalidCommandId)
+		cid = xlrec->cmin;
+	else
+	{
+		cid = InvalidCommandId; /* silence compiler */
+		elog(ERROR, "xl_heap_new_cid record without a valid CommandId");
+	}
+
+	ReorderBufferAddNewCommandId(builder->reorder, xid, lsn, cid + 1);
+}
+
+/*
+ * Add a new Snapshot to all transactions we're decoding that currently are
+ * in-progress so they can see new catalog contents made by the transaction
+ * that just committed. This is necessary because those in-progress
+ * transactions will use the new catalog's contents from here on (at the very
+ * least everything they do needs to be compatible with newer catalog
+ * contents).
+ */
+static void
+SnapBuildDistributeNewCatalogSnapshot(SnapBuild *builder, XLogRecPtr lsn)
+{
+	dlist_iter	txn_i;
+	ReorderBufferTXN *txn;
+
+	/*
+	 * Iterate through all toplevel transactions. This can include
+	 * subtransactions which we just don't yet know to be that, but that's
+	 * fine, they will just get an unnecessary snapshot queued.
+	 */
+	dlist_foreach(txn_i, &builder->reorder->toplevel_by_lsn)
+	{
+		txn = dlist_container(ReorderBufferTXN, node, txn_i.cur);
+
+		Assert(TransactionIdIsValid(txn->xid));
+
+		/*
+		 * If we don't have a base snapshot yet, there are no changes in this
+		 * transaction which in turn implies we don't yet need a snapshot at
+		 * all. We'll add a snapshot when the first change gets queued.
+		 *
+		 * NB: This works correctly even for subtransactions because
+		 * ReorderBufferAssignChild() takes care to transfer the base snapshot
+		 * to the top-level transaction, and while iterating the changequeue
+		 * we'll get the change from the subtxn.
+		 */
+		if (!ReorderBufferXidHasBaseSnapshot(builder->reorder, txn->xid))
+			continue;
+
+		/*
+		 * We don't need to add snapshot to prepared transactions as they
+		 * should not see the new catalog contents.
+		 */
+		if (rbtxn_prepared(txn) || rbtxn_skip_prepared(txn))
+			continue;
+
+		elog(DEBUG2, "adding a new snapshot to %u at %X/%X",
+			 txn->xid, LSN_FORMAT_ARGS(lsn));
+
+		/*
+		 * increase the snapshot's refcount for the transaction we are handing
+		 * it out to
+		 */
+		SnapBuildSnapIncRefcount(builder->snapshot);
+		ReorderBufferAddSnapshot(builder->reorder, txn->xid, lsn,
+								 builder->snapshot);
+	}
+}
+
+/*
+ * Keep track of a new catalog changing transaction that has committed.
+ */
+static void
+SnapBuildAddCommittedTxn(SnapBuild *builder, TransactionId xid)
+{
+	Assert(TransactionIdIsValid(xid));
+
+	if (builder->committed.xcnt == builder->committed.xcnt_space)
+	{
+		builder->committed.xcnt_space = builder->committed.xcnt_space * 2 + 1;
+
+		elog(DEBUG1, "increasing space for committed transactions to %u",
+			 (uint32) builder->committed.xcnt_space);
+
+		builder->committed.xip = repalloc(builder->committed.xip,
+										  builder->committed.xcnt_space * sizeof(TransactionId));
+	}
+
+	/*
+	 * TODO: It might make sense to keep the array sorted here instead of
+	 * doing it every time we build a new snapshot. On the other hand this
+	 * gets called repeatedly when a transaction with subtransactions commits.
+	 */
+	builder->committed.xip[builder->committed.xcnt++] = xid;
+}
+
+/*
+ * Remove knowledge about transactions we treat as committed that are smaller
+ * than ->xmin. Those won't ever get checked via the ->committed array but via
+ * the clog machinery, so we don't need to waste memory on them.
+ */
+static void
+SnapBuildPurgeCommittedTxn(SnapBuild *builder)
+{
+	int			off;
+	TransactionId *workspace;
+	int			surviving_xids = 0;
+
+	/* not ready yet */
+	if (!TransactionIdIsNormal(builder->xmin))
+		return;
+
+	/* TODO: Neater algorithm than just copying and iterating? */
+	workspace =
+		MemoryContextAlloc(builder->context,
+						   builder->committed.xcnt * sizeof(TransactionId));
+
+	/* copy xids that still are interesting to workspace */
+	for (off = 0; off < builder->committed.xcnt; off++)
+	{
+		if (NormalTransactionIdPrecedes(builder->committed.xip[off],
+										builder->xmin))
+			;					/* remove */
+		else
+			workspace[surviving_xids++] = builder->committed.xip[off];
+	}
+
+	/* copy workspace back to persistent state */
+	memcpy(builder->committed.xip, workspace,
+		   surviving_xids * sizeof(TransactionId));
+
+	elog(DEBUG3, "purged committed transactions from %u to %u, xmin: %u, xmax: %u",
+		 (uint32) builder->committed.xcnt, (uint32) surviving_xids,
+		 builder->xmin, builder->xmax);
+	builder->committed.xcnt = surviving_xids;
+
+	pfree(workspace);
+}
+
+/*
+ * Handle everything that needs to be done when a transaction commits
+ */
+void
+SnapBuildCommitTxn(SnapBuild *builder, XLogRecPtr lsn, TransactionId xid,
+				   int nsubxacts, TransactionId *subxacts)
+{
+	int			nxact;
+
+	bool		needs_snapshot = false;
+	bool		needs_timetravel = false;
+	bool		sub_needs_timetravel = false;
+
+	TransactionId xmax = xid;
+
+	/*
+	 * Transactions preceding BUILDING_SNAPSHOT will neither be decoded, nor
+	 * will they be part of a snapshot.  So we don't need to record anything.
+	 */
+	if (builder->state == SNAPBUILD_START ||
+		(builder->state == SNAPBUILD_BUILDING_SNAPSHOT &&
+		 TransactionIdPrecedes(xid, builder->next_phase_at)))
+	{
+		/* ensure that only commits after this are getting replayed */
+		if (builder->start_decoding_at <= lsn)
+			builder->start_decoding_at = lsn + 1;
+		return;
+	}
+
+	if (builder->state < SNAPBUILD_CONSISTENT)
+	{
+		/* ensure that only commits after this are getting replayed */
+		if (builder->start_decoding_at <= lsn)
+			builder->start_decoding_at = lsn + 1;
+
+		/*
+		 * If building an exportable snapshot, force xid to be tracked, even
+		 * if the transaction didn't modify the catalog.
+		 */
+		if (builder->building_full_snapshot)
+		{
+			needs_timetravel = true;
+		}
+	}
+
+	for (nxact = 0; nxact < nsubxacts; nxact++)
+	{
+		TransactionId subxid = subxacts[nxact];
+
+		/*
+		 * Add subtransaction to base snapshot if catalog modifying, we don't
+		 * distinguish to toplevel transactions there.
+		 */
+		if (ReorderBufferXidHasCatalogChanges(builder->reorder, subxid))
+		{
+			sub_needs_timetravel = true;
+			needs_snapshot = true;
+
+			elog(DEBUG1, "found subtransaction %u:%u with catalog changes",
+				 xid, subxid);
+
+			SnapBuildAddCommittedTxn(builder, subxid);
+
+			if (NormalTransactionIdFollows(subxid, xmax))
+				xmax = subxid;
+		}
+
+		/*
+		 * If we're forcing timetravel we also need visibility information
+		 * about subtransaction, so keep track of subtransaction's state, even
+		 * if not catalog modifying.  Don't need to distribute a snapshot in
+		 * that case.
+		 */
+		else if (needs_timetravel)
+		{
+			SnapBuildAddCommittedTxn(builder, subxid);
+			if (NormalTransactionIdFollows(subxid, xmax))
+				xmax = subxid;
+		}
+	}
+
+	/* if top-level modified catalog, it'll need a snapshot */
+	if (ReorderBufferXidHasCatalogChanges(builder->reorder, xid))
+	{
+		elog(DEBUG2, "found top level transaction %u, with catalog changes",
+			 xid);
+		needs_snapshot = true;
+		needs_timetravel = true;
+		SnapBuildAddCommittedTxn(builder, xid);
+	}
+	else if (sub_needs_timetravel)
+	{
+		/* track toplevel txn as well, subxact alone isn't meaningful */
+		SnapBuildAddCommittedTxn(builder, xid);
+	}
+	else if (needs_timetravel)
+	{
+		elog(DEBUG2, "forced transaction %u to do timetravel", xid);
+
+		SnapBuildAddCommittedTxn(builder, xid);
+	}
+
+	if (!needs_timetravel)
+	{
+		/* record that we cannot export a general snapshot anymore */
+		builder->committed.includes_all_transactions = false;
+	}
+
+	Assert(!needs_snapshot || needs_timetravel);
+
+	/*
+	 * Adjust xmax of the snapshot builder, we only do that for committed,
+	 * catalog modifying, transactions, everything else isn't interesting for
+	 * us since we'll never look at the respective rows.
+	 */
+	if (needs_timetravel &&
+		(!TransactionIdIsValid(builder->xmax) ||
+		 TransactionIdFollowsOrEquals(xmax, builder->xmax)))
+	{
+		builder->xmax = xmax;
+		TransactionIdAdvance(builder->xmax);
+	}
+
+	/* if there's any reason to build a historic snapshot, do so now */
+	if (needs_snapshot)
+	{
+		/*
+		 * If we haven't built a complete snapshot yet there's no need to hand
+		 * it out, it wouldn't (and couldn't) be used anyway.
+		 */
+		if (builder->state < SNAPBUILD_FULL_SNAPSHOT)
+			return;
+
+		/*
+		 * Decrease the snapshot builder's refcount of the old snapshot, note
+		 * that it still will be used if it has been handed out to the
+		 * reorderbuffer earlier.
+		 */
+		if (builder->snapshot)
+			SnapBuildSnapDecRefcount(builder->snapshot);
+
+		builder->snapshot = SnapBuildBuildSnapshot(builder);
+
+		/* we might need to execute invalidations, add snapshot */
+		if (!ReorderBufferXidHasBaseSnapshot(builder->reorder, xid))
+		{
+			SnapBuildSnapIncRefcount(builder->snapshot);
+			ReorderBufferSetBaseSnapshot(builder->reorder, xid, lsn,
+										 builder->snapshot);
+		}
+
+		/* refcount of the snapshot builder for the new snapshot */
+		SnapBuildSnapIncRefcount(builder->snapshot);
+
+		/* add a new catalog snapshot to all currently running transactions */
+		SnapBuildDistributeNewCatalogSnapshot(builder, lsn);
+	}
+}
+
+
+/* -----------------------------------
+ * Snapshot building functions dealing with xlog records
+ * -----------------------------------
+ */
+
+/*
+ * Process a running xacts record, and use its information to first build a
+ * historic snapshot and later to release resources that aren't needed
+ * anymore.
+ */
+void
+SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running)
+{
+	ReorderBufferTXN *txn;
+	TransactionId xmin;
+
+	/*
+	 * If we're not consistent yet, inspect the record to see whether it
+	 * allows to get closer to being consistent. If we are consistent, dump
+	 * our snapshot so others or we, after a restart, can use it.
+	 */
+	if (builder->state < SNAPBUILD_CONSISTENT)
+	{
+		/* returns false if there's no point in performing cleanup just yet */
+		if (!SnapBuildFindSnapshot(builder, lsn, running))
+			return;
+	}
+	else
+		SnapBuildSerialize(builder, lsn);
+
+	/*
+	 * Update range of interesting xids based on the running xacts
+	 * information. We don't increase ->xmax using it, because once we are in
+	 * a consistent state we can do that ourselves and much more efficiently
+	 * so, because we only need to do it for catalog transactions since we
+	 * only ever look at those.
+	 *
+	 * NB: We only increase xmax when a catalog modifying transaction commits
+	 * (see SnapBuildCommitTxn).  Because of this, xmax can be lower than
+	 * xmin, which looks odd but is correct and actually more efficient, since
+	 * we hit fast paths in heapam_visibility.c.
+	 */
+	builder->xmin = running->oldestRunningXid;
+
+	/* Remove transactions we don't need to keep track off anymore */
+	SnapBuildPurgeCommittedTxn(builder);
+
+	/*
+	 * Advance the xmin limit for the current replication slot, to allow
+	 * vacuum to clean up the tuples this slot has been protecting.
+	 *
+	 * The reorderbuffer might have an xmin among the currently running
+	 * snapshots; use it if so.  If not, we need only consider the snapshots
+	 * we'll produce later, which can't be less than the oldest running xid in
+	 * the record we're reading now.
+	 */
+	xmin = ReorderBufferGetOldestXmin(builder->reorder);
+	if (xmin == InvalidTransactionId)
+		xmin = running->oldestRunningXid;
+	elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u",
+		 builder->xmin, builder->xmax, running->oldestRunningXid, xmin);
+	LogicalIncreaseXminForSlot(lsn, xmin);
+
+	/*
+	 * Also tell the slot where we can restart decoding from. We don't want to
+	 * do that after every commit because changing that implies an fsync of
+	 * the logical slot's state file, so we only do it every time we see a
+	 * running xacts record.
+	 *
+	 * Do so by looking for the oldest in progress transaction (determined by
+	 * the first LSN of any of its relevant records). Every transaction
+	 * remembers the last location we stored the snapshot to disk before its
+	 * beginning. That point is where we can restart from.
+	 */
+
+	/*
+	 * Can't know about a serialized snapshot's location if we're not
+	 * consistent.
+	 */
+	if (builder->state < SNAPBUILD_CONSISTENT)
+		return;
+
+	txn = ReorderBufferGetOldestTXN(builder->reorder);
+
+	/*
+	 * oldest ongoing txn might have started when we didn't yet serialize
+	 * anything because we hadn't reached a consistent state yet.
+	 */
+	if (txn != NULL && txn->restart_decoding_lsn != InvalidXLogRecPtr)
+		LogicalIncreaseRestartDecodingForSlot(lsn, txn->restart_decoding_lsn);
+
+	/*
+	 * No in-progress transaction, can reuse the last serialized snapshot if
+	 * we have one.
+	 */
+	else if (txn == NULL &&
+			 builder->reorder->current_restart_decoding_lsn != InvalidXLogRecPtr &&
+			 builder->last_serialized_snapshot != InvalidXLogRecPtr)
+		LogicalIncreaseRestartDecodingForSlot(lsn,
+											  builder->last_serialized_snapshot);
+}
+
+
+/*
+ * Build the start of a snapshot that's capable of decoding the catalog.
+ *
+ * Helper function for SnapBuildProcessRunningXacts() while we're not yet
+ * consistent.
+ *
+ * Returns true if there is a point in performing internal maintenance/cleanup
+ * using the xl_running_xacts record.
+ */
+static bool
+SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running)
+{
+	/* ---
+	 * Build catalog decoding snapshot incrementally using information about
+	 * the currently running transactions. There are several ways to do that:
+	 *
+	 * a) There were no running transactions when the xl_running_xacts record
+	 *	  was inserted, jump to CONSISTENT immediately. We might find such a
+	 *	  state while waiting on c)'s sub-states.
+	 *
+	 * b) This (in a previous run) or another decoding slot serialized a
+	 *	  snapshot to disk that we can use.  Can't use this method for the
+	 *	  initial snapshot when slot is being created and needs full snapshot
+	 *	  for export or direct use, as that snapshot will only contain catalog
+	 *	  modifying transactions.
+	 *
+	 * c) First incrementally build a snapshot for catalog tuples
+	 *	  (BUILDING_SNAPSHOT), that requires all, already in-progress,
+	 *	  transactions to finish.  Every transaction starting after that
+	 *	  (FULL_SNAPSHOT state), has enough information to be decoded.  But
+	 *	  for older running transactions no viable snapshot exists yet, so
+	 *	  CONSISTENT will only be reached once all of those have finished.
+	 * ---
+	 */
+
+	/*
+	 * xl_running_xact record is older than what we can use, we might not have
+	 * all necessary catalog rows anymore.
+	 */
+	if (TransactionIdIsNormal(builder->initial_xmin_horizon) &&
+		NormalTransactionIdPrecedes(running->oldestRunningXid,
+									builder->initial_xmin_horizon))
+	{
+		ereport(DEBUG1,
+				(errmsg_internal("skipping snapshot at %X/%X while building logical decoding snapshot, xmin horizon too low",
+								 LSN_FORMAT_ARGS(lsn)),
+				 errdetail_internal("initial xmin horizon of %u vs the snapshot's %u",
+									builder->initial_xmin_horizon, running->oldestRunningXid)));
+
+
+		SnapBuildWaitSnapshot(running, builder->initial_xmin_horizon);
+
+		return true;
+	}
+
+	/*
+	 * a) No transaction were running, we can jump to consistent.
+	 *
+	 * This is not affected by races around xl_running_xacts, because we can
+	 * miss transaction commits, but currently not transactions starting.
+	 *
+	 * NB: We might have already started to incrementally assemble a snapshot,
+	 * so we need to be careful to deal with that.
+	 */
+	if (running->oldestRunningXid == running->nextXid)
+	{
+		if (builder->start_decoding_at == InvalidXLogRecPtr ||
+			builder->start_decoding_at <= lsn)
+			/* can decode everything after this */
+			builder->start_decoding_at = lsn + 1;
+
+		/* As no transactions were running xmin/xmax can be trivially set. */
+		builder->xmin = running->nextXid;	/* < are finished */
+		builder->xmax = running->nextXid;	/* >= are running */
+
+		/* so we can safely use the faster comparisons */
+		Assert(TransactionIdIsNormal(builder->xmin));
+		Assert(TransactionIdIsNormal(builder->xmax));
+
+		builder->state = SNAPBUILD_CONSISTENT;
+		builder->next_phase_at = InvalidTransactionId;
+
+		ereport(LOG,
+				(errmsg("logical decoding found consistent point at %X/%X",
+						LSN_FORMAT_ARGS(lsn)),
+				 errdetail("There are no running transactions.")));
+
+		return false;
+	}
+	/* b) valid on disk state and not building full snapshot */
+	else if (!builder->building_full_snapshot &&
+			 SnapBuildRestore(builder, lsn))
+	{
+		/* there won't be any state to cleanup */
+		return false;
+	}
+
+	/*
+	 * c) transition from START to BUILDING_SNAPSHOT.
+	 *
+	 * In START state, and a xl_running_xacts record with running xacts is
+	 * encountered.  In that case, switch to BUILDING_SNAPSHOT state, and
+	 * record xl_running_xacts->nextXid.  Once all running xacts have finished
+	 * (i.e. they're all >= nextXid), we have a complete catalog snapshot.  It
+	 * might look that we could use xl_running_xact's ->xids information to
+	 * get there quicker, but that is problematic because transactions marked
+	 * as running, might already have inserted their commit record - it's
+	 * infeasible to change that with locking.
+	 */
+	else if (builder->state == SNAPBUILD_START)
+	{
+		builder->state = SNAPBUILD_BUILDING_SNAPSHOT;
+		builder->next_phase_at = running->nextXid;
+
+		/*
+		 * Start with an xmin/xmax that's correct for future, when all the
+		 * currently running transactions have finished. We'll update both
+		 * while waiting for the pending transactions to finish.
+		 */
+		builder->xmin = running->nextXid;	/* < are finished */
+		builder->xmax = running->nextXid;	/* >= are running */
+
+		/* so we can safely use the faster comparisons */
+		Assert(TransactionIdIsNormal(builder->xmin));
+		Assert(TransactionIdIsNormal(builder->xmax));
+
+		ereport(LOG,
+				(errmsg("logical decoding found initial starting point at %X/%X",
+						LSN_FORMAT_ARGS(lsn)),
+				 errdetail("Waiting for transactions (approximately %d) older than %u to end.",
+						   running->xcnt, running->nextXid)));
+
+		SnapBuildWaitSnapshot(running, running->nextXid);
+	}
+
+	/*
+	 * c) transition from BUILDING_SNAPSHOT to FULL_SNAPSHOT.
+	 *
+	 * In BUILDING_SNAPSHOT state, and this xl_running_xacts' oldestRunningXid
+	 * is >= than nextXid from when we switched to BUILDING_SNAPSHOT.  This
+	 * means all transactions starting afterwards have enough information to
+	 * be decoded.  Switch to FULL_SNAPSHOT.
+	 */
+	else if (builder->state == SNAPBUILD_BUILDING_SNAPSHOT &&
+			 TransactionIdPrecedesOrEquals(builder->next_phase_at,
+										   running->oldestRunningXid))
+	{
+		builder->state = SNAPBUILD_FULL_SNAPSHOT;
+		builder->next_phase_at = running->nextXid;
+
+		ereport(LOG,
+				(errmsg("logical decoding found initial consistent point at %X/%X",
+						LSN_FORMAT_ARGS(lsn)),
+				 errdetail("Waiting for transactions (approximately %d) older than %u to end.",
+						   running->xcnt, running->nextXid)));
+
+		SnapBuildWaitSnapshot(running, running->nextXid);
+	}
+
+	/*
+	 * c) transition from FULL_SNAPSHOT to CONSISTENT.
+	 *
+	 * In FULL_SNAPSHOT state (see d) ), and this xl_running_xacts'
+	 * oldestRunningXid is >= than nextXid from when we switched to
+	 * FULL_SNAPSHOT.  This means all transactions that are currently in
+	 * progress have a catalog snapshot, and all their changes have been
+	 * collected.  Switch to CONSISTENT.
+	 */
+	else if (builder->state == SNAPBUILD_FULL_SNAPSHOT &&
+			 TransactionIdPrecedesOrEquals(builder->next_phase_at,
+										   running->oldestRunningXid))
+	{
+		builder->state = SNAPBUILD_CONSISTENT;
+		builder->next_phase_at = InvalidTransactionId;
+
+		ereport(LOG,
+				(errmsg("logical decoding found consistent point at %X/%X",
+						LSN_FORMAT_ARGS(lsn)),
+				 errdetail("There are no old transactions anymore.")));
+	}
+
+	/*
+	 * We already started to track running xacts and need to wait for all
+	 * in-progress ones to finish. We fall through to the normal processing of
+	 * records so incremental cleanup can be performed.
+	 */
+	return true;
+
+}
+
+/* ---
+ * Iterate through xids in record, wait for all older than the cutoff to
+ * finish.  Then, if possible, log a new xl_running_xacts record.
+ *
+ * This isn't required for the correctness of decoding, but to:
+ * a) allow isolationtester to notice that we're currently waiting for
+ *	  something.
+ * b) log a new xl_running_xacts record where it'd be helpful, without having
+ *	  to wait for bgwriter or checkpointer.
+ * ---
+ */
+static void
+SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff)
+{
+	int			off;
+
+	for (off = 0; off < running->xcnt; off++)
+	{
+		TransactionId xid = running->xids[off];
+
+		/*
+		 * Upper layers should prevent that we ever need to wait on ourselves.
+		 * Check anyway, since failing to do so would either result in an
+		 * endless wait or an Assert() failure.
+		 */
+		if (TransactionIdIsCurrentTransactionId(xid))
+			elog(ERROR, "waiting for ourselves");
+
+		if (TransactionIdFollows(xid, cutoff))
+			continue;
+
+		XactLockTableWait(xid, NULL, NULL, XLTW_None);
+	}
+
+	/*
+	 * All transactions we needed to finish finished - try to ensure there is
+	 * another xl_running_xacts record in a timely manner, without having to
+	 * wait for bgwriter or checkpointer to log one.  During recovery we can't
+	 * enforce that, so we'll have to wait.
+	 */
+	if (!RecoveryInProgress())
+	{
+		LogStandbySnapshot();
+	}
+}
+
+/* -----------------------------------
+ * Snapshot serialization support
+ * -----------------------------------
+ */
+
+/*
+ * We store current state of struct SnapBuild on disk in the following manner:
+ *
+ * struct SnapBuildOnDisk;
+ * TransactionId * running.xcnt_space;
+ * TransactionId * committed.xcnt; (*not xcnt_space*)
+ *
+ */
+typedef struct SnapBuildOnDisk
+{
+	/* first part of this struct needs to be version independent */
+
+	/* data not covered by checksum */
+	uint32		magic;
+	pg_crc32c	checksum;
+
+	/* data covered by checksum */
+
+	/* version, in case we want to support pg_upgrade */
+	uint32		version;
+	/* how large is the on disk data, excluding the constant sized part */
+	uint32		length;
+
+	/* version dependent part */
+	SnapBuild	builder;
+
+	/* variable amount of TransactionIds follows */
+} SnapBuildOnDisk;
+
+#define SnapBuildOnDiskConstantSize \
+	offsetof(SnapBuildOnDisk, builder)
+#define SnapBuildOnDiskNotChecksummedSize \
+	offsetof(SnapBuildOnDisk, version)
+
+#define SNAPBUILD_MAGIC 0x51A1E001
+#define SNAPBUILD_VERSION 4
+
+/*
+ * Store/Load a snapshot from disk, depending on the snapshot builder's state.
+ *
+ * Supposed to be used by external (i.e. not snapbuild.c) code that just read
+ * a record that's a potential location for a serialized snapshot.
+ */
+void
+SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn)
+{
+	if (builder->state < SNAPBUILD_CONSISTENT)
+		SnapBuildRestore(builder, lsn);
+	else
+		SnapBuildSerialize(builder, lsn);
+}
+
+/*
+ * Serialize the snapshot 'builder' at the location 'lsn' if it hasn't already
+ * been done by another decoding process.
+ */
+static void
+SnapBuildSerialize(SnapBuild *builder, XLogRecPtr lsn)
+{
+	Size		needed_length;
+	SnapBuildOnDisk *ondisk = NULL;
+	char	   *ondisk_c;
+	int			fd;
+	char		tmppath[MAXPGPATH];
+	char		path[MAXPGPATH];
+	int			ret;
+	struct stat stat_buf;
+	Size		sz;
+
+	Assert(lsn != InvalidXLogRecPtr);
+	Assert(builder->last_serialized_snapshot == InvalidXLogRecPtr ||
+		   builder->last_serialized_snapshot <= lsn);
+
+	/*
+	 * no point in serializing if we cannot continue to work immediately after
+	 * restoring the snapshot
+	 */
+	if (builder->state < SNAPBUILD_CONSISTENT)
+		return;
+
+	/* consistent snapshots have no next phase */
+	Assert(builder->next_phase_at == InvalidTransactionId);
+
+	/*
+	 * We identify snapshots by the LSN they are valid for. We don't need to
+	 * include timelines in the name as each LSN maps to exactly one timeline
+	 * unless the user used pg_resetwal or similar. If a user did so, there's
+	 * no hope continuing to decode anyway.
+	 */
+	sprintf(path, "pg_logical/snapshots/%X-%X.snap",
+			LSN_FORMAT_ARGS(lsn));
+
+	/*
+	 * first check whether some other backend already has written the snapshot
+	 * for this LSN. It's perfectly fine if there's none, so we accept ENOENT
+	 * as a valid state. Everything else is an unexpected error.
+	 */
+	ret = stat(path, &stat_buf);
+
+	if (ret != 0 && errno != ENOENT)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not stat file \"%s\": %m", path)));
+
+	else if (ret == 0)
+	{
+		/*
+		 * somebody else has already serialized to this point, don't overwrite
+		 * but remember location, so we don't need to read old data again.
+		 *
+		 * To be sure it has been synced to disk after the rename() from the
+		 * tempfile filename to the real filename, we just repeat the fsync.
+		 * That ought to be cheap because in most scenarios it should already
+		 * be safely on disk.
+		 */
+		fsync_fname(path, false);
+		fsync_fname("pg_logical/snapshots", true);
+
+		builder->last_serialized_snapshot = lsn;
+		goto out;
+	}
+
+	/*
+	 * there is an obvious race condition here between the time we stat(2) the
+	 * file and us writing the file. But we rename the file into place
+	 * atomically and all files created need to contain the same data anyway,
+	 * so this is perfectly fine, although a bit of a resource waste. Locking
+	 * seems like pointless complication.
+	 */
+	elog(DEBUG1, "serializing snapshot to %s", path);
+
+	/* to make sure only we will write to this tempfile, include pid */
+	sprintf(tmppath, "pg_logical/snapshots/%X-%X.snap.%d.tmp",
+			LSN_FORMAT_ARGS(lsn), MyProcPid);
+
+	/*
+	 * Unlink temporary file if it already exists, needs to have been before a
+	 * crash/error since we won't enter this function twice from within a
+	 * single decoding slot/backend and the temporary file contains the pid of
+	 * the current process.
+	 */
+	if (unlink(tmppath) != 0 && errno != ENOENT)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not remove file \"%s\": %m", tmppath)));
+
+	needed_length = sizeof(SnapBuildOnDisk) +
+		sizeof(TransactionId) * builder->committed.xcnt;
+
+	ondisk_c = MemoryContextAllocZero(builder->context, needed_length);
+	ondisk = (SnapBuildOnDisk *) ondisk_c;
+	ondisk->magic = SNAPBUILD_MAGIC;
+	ondisk->version = SNAPBUILD_VERSION;
+	ondisk->length = needed_length;
+	INIT_CRC32C(ondisk->checksum);
+	COMP_CRC32C(ondisk->checksum,
+				((char *) ondisk) + SnapBuildOnDiskNotChecksummedSize,
+				SnapBuildOnDiskConstantSize - SnapBuildOnDiskNotChecksummedSize);
+	ondisk_c += sizeof(SnapBuildOnDisk);
+
+	memcpy(&ondisk->builder, builder, sizeof(SnapBuild));
+	/* NULL-ify memory-only data */
+	ondisk->builder.context = NULL;
+	ondisk->builder.snapshot = NULL;
+	ondisk->builder.reorder = NULL;
+	ondisk->builder.committed.xip = NULL;
+
+	COMP_CRC32C(ondisk->checksum,
+				&ondisk->builder,
+				sizeof(SnapBuild));
+
+	/* copy committed xacts */
+	sz = sizeof(TransactionId) * builder->committed.xcnt;
+	memcpy(ondisk_c, builder->committed.xip, sz);
+	COMP_CRC32C(ondisk->checksum, ondisk_c, sz);
+	ondisk_c += sz;
+
+	FIN_CRC32C(ondisk->checksum);
+
+	/* we have valid data now, open tempfile and write it there */
+	fd = OpenTransientFile(tmppath,
+						   O_CREAT | O_EXCL | O_WRONLY | PG_BINARY);
+	if (fd < 0)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not open file \"%s\": %m", tmppath)));
+
+	errno = 0;
+	pgstat_report_wait_start(WAIT_EVENT_SNAPBUILD_WRITE);
+	if ((write(fd, ondisk, needed_length)) != needed_length)
+	{
+		int			save_errno = errno;
+
+		CloseTransientFile(fd);
+
+		/* if write didn't set errno, assume problem is no disk space */
+		errno = save_errno ? save_errno : ENOSPC;
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not write to file \"%s\": %m", tmppath)));
+	}
+	pgstat_report_wait_end();
+
+	/*
+	 * fsync the file before renaming so that even if we crash after this we
+	 * have either a fully valid file or nothing.
+	 *
+	 * It's safe to just ERROR on fsync() here because we'll retry the whole
+	 * operation including the writes.
+	 *
+	 * TODO: Do the fsync() via checkpoints/restartpoints, doing it here has
+	 * some noticeable overhead since it's performed synchronously during
+	 * decoding?
+	 */
+	pgstat_report_wait_start(WAIT_EVENT_SNAPBUILD_SYNC);
+	if (pg_fsync(fd) != 0)
+	{
+		int			save_errno = errno;
+
+		CloseTransientFile(fd);
+		errno = save_errno;
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not fsync file \"%s\": %m", tmppath)));
+	}
+	pgstat_report_wait_end();
+
+	if (CloseTransientFile(fd) != 0)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not close file \"%s\": %m", tmppath)));
+
+	fsync_fname("pg_logical/snapshots", true);
+
+	/*
+	 * We may overwrite the work from some other backend, but that's ok, our
+	 * snapshot is valid as well, we'll just have done some superfluous work.
+	 */
+	if (rename(tmppath, path) != 0)
+	{
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not rename file \"%s\" to \"%s\": %m",
+						tmppath, path)));
+	}
+
+	/* make sure we persist */
+	fsync_fname(path, false);
+	fsync_fname("pg_logical/snapshots", true);
+
+	/*
+	 * Now there's no way we can loose the dumped state anymore, remember this
+	 * as a serialization point.
+	 */
+	builder->last_serialized_snapshot = lsn;
+
+out:
+	ReorderBufferSetRestartPoint(builder->reorder,
+								 builder->last_serialized_snapshot);
+	/* be tidy */
+	if (ondisk)
+		pfree(ondisk);
+}
+
+/*
+ * Restore a snapshot into 'builder' if previously one has been stored at the
+ * location indicated by 'lsn'. Returns true if successful, false otherwise.
+ */
+static bool
+SnapBuildRestore(SnapBuild *builder, XLogRecPtr lsn)
+{
+	SnapBuildOnDisk ondisk;
+	int			fd;
+	char		path[MAXPGPATH];
+	Size		sz;
+	int			readBytes;
+	pg_crc32c	checksum;
+
+	/* no point in loading a snapshot if we're already there */
+	if (builder->state == SNAPBUILD_CONSISTENT)
+		return false;
+
+	sprintf(path, "pg_logical/snapshots/%X-%X.snap",
+			LSN_FORMAT_ARGS(lsn));
+
+	fd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
+
+	if (fd < 0 && errno == ENOENT)
+		return false;
+	else if (fd < 0)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not open file \"%s\": %m", path)));
+
+	/* ----
+	 * Make sure the snapshot had been stored safely to disk, that's normally
+	 * cheap.
+	 * Note that we do not need PANIC here, nobody will be able to use the
+	 * slot without fsyncing, and saving it won't succeed without an fsync()
+	 * either...
+	 * ----
+	 */
+	fsync_fname(path, false);
+	fsync_fname("pg_logical/snapshots", true);
+
+
+	/* read statically sized portion of snapshot */
+	pgstat_report_wait_start(WAIT_EVENT_SNAPBUILD_READ);
+	readBytes = read(fd, &ondisk, SnapBuildOnDiskConstantSize);
+	pgstat_report_wait_end();
+	if (readBytes != SnapBuildOnDiskConstantSize)
+	{
+		int			save_errno = errno;
+
+		CloseTransientFile(fd);
+
+		if (readBytes < 0)
+		{
+			errno = save_errno;
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not read file \"%s\": %m", path)));
+		}
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_DATA_CORRUPTED),
+					 errmsg("could not read file \"%s\": read %d of %zu",
+							path, readBytes,
+							(Size) SnapBuildOnDiskConstantSize)));
+	}
+
+	if (ondisk.magic != SNAPBUILD_MAGIC)
+		ereport(ERROR,
+				(errcode(ERRCODE_DATA_CORRUPTED),
+				 errmsg("snapbuild state file \"%s\" has wrong magic number: %u instead of %u",
+						path, ondisk.magic, SNAPBUILD_MAGIC)));
+
+	if (ondisk.version != SNAPBUILD_VERSION)
+		ereport(ERROR,
+				(errcode(ERRCODE_DATA_CORRUPTED),
+				 errmsg("snapbuild state file \"%s\" has unsupported version: %u instead of %u",
+						path, ondisk.version, SNAPBUILD_VERSION)));
+
+	INIT_CRC32C(checksum);
+	COMP_CRC32C(checksum,
+				((char *) &ondisk) + SnapBuildOnDiskNotChecksummedSize,
+				SnapBuildOnDiskConstantSize - SnapBuildOnDiskNotChecksummedSize);
+
+	/* read SnapBuild */
+	pgstat_report_wait_start(WAIT_EVENT_SNAPBUILD_READ);
+	readBytes = read(fd, &ondisk.builder, sizeof(SnapBuild));
+	pgstat_report_wait_end();
+	if (readBytes != sizeof(SnapBuild))
+	{
+		int			save_errno = errno;
+
+		CloseTransientFile(fd);
+
+		if (readBytes < 0)
+		{
+			errno = save_errno;
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not read file \"%s\": %m", path)));
+		}
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_DATA_CORRUPTED),
+					 errmsg("could not read file \"%s\": read %d of %zu",
+							path, readBytes, sizeof(SnapBuild))));
+	}
+	COMP_CRC32C(checksum, &ondisk.builder, sizeof(SnapBuild));
+
+	/* restore committed xacts information */
+	sz = sizeof(TransactionId) * ondisk.builder.committed.xcnt;
+	ondisk.builder.committed.xip = MemoryContextAllocZero(builder->context, sz);
+	pgstat_report_wait_start(WAIT_EVENT_SNAPBUILD_READ);
+	readBytes = read(fd, ondisk.builder.committed.xip, sz);
+	pgstat_report_wait_end();
+	if (readBytes != sz)
+	{
+		int			save_errno = errno;
+
+		CloseTransientFile(fd);
+
+		if (readBytes < 0)
+		{
+			errno = save_errno;
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not read file \"%s\": %m", path)));
+		}
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_DATA_CORRUPTED),
+					 errmsg("could not read file \"%s\": read %d of %zu",
+							path, readBytes, sz)));
+	}
+	COMP_CRC32C(checksum, ondisk.builder.committed.xip, sz);
+
+	if (CloseTransientFile(fd) != 0)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not close file \"%s\": %m", path)));
+
+	FIN_CRC32C(checksum);
+
+	/* verify checksum of what we've read */
+	if (!EQ_CRC32C(checksum, ondisk.checksum))
+		ereport(ERROR,
+				(errcode(ERRCODE_DATA_CORRUPTED),
+				 errmsg("checksum mismatch for snapbuild state file \"%s\": is %u, should be %u",
+						path, checksum, ondisk.checksum)));
+
+	/*
+	 * ok, we now have a sensible snapshot here, figure out if it has more
+	 * information than we have.
+	 */
+
+	/*
+	 * We are only interested in consistent snapshots for now, comparing
+	 * whether one incomplete snapshot is more "advanced" seems to be
+	 * unnecessarily complex.
+	 */
+	if (ondisk.builder.state < SNAPBUILD_CONSISTENT)
+		goto snapshot_not_interesting;
+
+	/*
+	 * Don't use a snapshot that requires an xmin that we cannot guarantee to
+	 * be available.
+	 */
+	if (TransactionIdPrecedes(ondisk.builder.xmin, builder->initial_xmin_horizon))
+		goto snapshot_not_interesting;
+
+	/* consistent snapshots have no next phase */
+	Assert(ondisk.builder.next_phase_at == InvalidTransactionId);
+
+	/* ok, we think the snapshot is sensible, copy over everything important */
+	builder->xmin = ondisk.builder.xmin;
+	builder->xmax = ondisk.builder.xmax;
+	builder->state = ondisk.builder.state;
+
+	builder->committed.xcnt = ondisk.builder.committed.xcnt;
+	/* We only allocated/stored xcnt, not xcnt_space xids ! */
+	/* don't overwrite preallocated xip, if we don't have anything here */
+	if (builder->committed.xcnt > 0)
+	{
+		pfree(builder->committed.xip);
+		builder->committed.xcnt_space = ondisk.builder.committed.xcnt;
+		builder->committed.xip = ondisk.builder.committed.xip;
+	}
+	ondisk.builder.committed.xip = NULL;
+
+	/* our snapshot is not interesting anymore, build a new one */
+	if (builder->snapshot != NULL)
+	{
+		SnapBuildSnapDecRefcount(builder->snapshot);
+	}
+	builder->snapshot = SnapBuildBuildSnapshot(builder);
+	SnapBuildSnapIncRefcount(builder->snapshot);
+
+	ReorderBufferSetRestartPoint(builder->reorder, lsn);
+
+	Assert(builder->state == SNAPBUILD_CONSISTENT);
+
+	ereport(LOG,
+			(errmsg("logical decoding found consistent point at %X/%X",
+					LSN_FORMAT_ARGS(lsn)),
+			 errdetail("Logical decoding will begin using saved snapshot.")));
+	return true;
+
+snapshot_not_interesting:
+	if (ondisk.builder.committed.xip != NULL)
+		pfree(ondisk.builder.committed.xip);
+	return false;
+}
+
+/*
+ * Remove all serialized snapshots that are not required anymore because no
+ * slot can need them. This doesn't actually have to run during a checkpoint,
+ * but it's a convenient point to schedule this.
+ *
+ * NB: We run this during checkpoints even if logical decoding is disabled so
+ * we cleanup old slots at some point after it got disabled.
+ */
+void
+CheckPointSnapBuild(void)
+{
+	XLogRecPtr	cutoff;
+	XLogRecPtr	redo;
+	DIR		   *snap_dir;
+	struct dirent *snap_de;
+	char		path[MAXPGPATH + 21];
+
+	/*
+	 * We start off with a minimum of the last redo pointer. No new
+	 * replication slot will start before that, so that's a safe upper bound
+	 * for removal.
+	 */
+	redo = GetRedoRecPtr();
+
+	/* now check for the restart ptrs from existing slots */
+	cutoff = ReplicationSlotsComputeLogicalRestartLSN();
+
+	/* don't start earlier than the restart lsn */
+	if (redo < cutoff)
+		cutoff = redo;
+
+	snap_dir = AllocateDir("pg_logical/snapshots");
+	while ((snap_de = ReadDir(snap_dir, "pg_logical/snapshots")) != NULL)
+	{
+		uint32		hi;
+		uint32		lo;
+		XLogRecPtr	lsn;
+		struct stat statbuf;
+
+		if (strcmp(snap_de->d_name, ".") == 0 ||
+			strcmp(snap_de->d_name, "..") == 0)
+			continue;
+
+		snprintf(path, sizeof(path), "pg_logical/snapshots/%s", snap_de->d_name);
+
+		if (lstat(path, &statbuf) == 0 && !S_ISREG(statbuf.st_mode))
+		{
+			elog(DEBUG1, "only regular files expected: %s", path);
+			continue;
+		}
+
+		/*
+		 * temporary filenames from SnapBuildSerialize() include the LSN and
+		 * everything but are postfixed by .$pid.tmp. We can just remove them
+		 * the same as other files because there can be none that are
+		 * currently being written that are older than cutoff.
+		 *
+		 * We just log a message if a file doesn't fit the pattern, it's
+		 * probably some editors lock/state file or similar...
+		 */
+		if (sscanf(snap_de->d_name, "%X-%X.snap", &hi, &lo) != 2)
+		{
+			ereport(LOG,
+					(errmsg("could not parse file name \"%s\"", path)));
+			continue;
+		}
+
+		lsn = ((uint64) hi) << 32 | lo;
+
+		/* check whether we still need it */
+		if (lsn < cutoff || cutoff == InvalidXLogRecPtr)
+		{
+			elog(DEBUG1, "removing snapbuild snapshot %s", path);
+
+			/*
+			 * It's not particularly harmful, though strange, if we can't
+			 * remove the file here. Don't prevent the checkpoint from
+			 * completing, that'd be a cure worse than the disease.
+			 */
+			if (unlink(path) < 0)
+			{
+				ereport(LOG,
+						(errcode_for_file_access(),
+						 errmsg("could not remove file \"%s\": %m",
+								path)));
+				continue;
+			}
+		}
+	}
+	FreeDir(snap_dir);
+}
diff --git a/src/backend/replication/logical/tablesync.c b/src/backend/replication/logical/tablesync.c
new file mode 100644
index 0000000..682c107
--- /dev/null
+++ b/src/backend/replication/logical/tablesync.c
@@ -0,0 +1,1160 @@
+/*-------------------------------------------------------------------------
+ * tablesync.c
+ *	  PostgreSQL logical replication: initial table data synchronization
+ *
+ * Copyright (c) 2012-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/tablesync.c
+ *
+ * NOTES
+ *	  This file contains code for initial table data synchronization for
+ *	  logical replication.
+ *
+ *	  The initial data synchronization is done separately for each table,
+ *	  in a separate apply worker that only fetches the initial snapshot data
+ *	  from the publisher and then synchronizes the position in the stream with
+ *	  the main apply worker.
+ *
+ *	  There are several reasons for doing the synchronization this way:
+ *	   - It allows us to parallelize the initial data synchronization
+ *		 which lowers the time needed for it to happen.
+ *	   - The initial synchronization does not have to hold the xid and LSN
+ *		 for the time it takes to copy data of all tables, causing less
+ *		 bloat and lower disk consumption compared to doing the
+ *		 synchronization in a single process for the whole database.
+ *	   - It allows us to synchronize any tables added after the initial
+ *		 synchronization has finished.
+ *
+ *	  The stream position synchronization works in multiple steps:
+ *	   - Apply worker requests a tablesync worker to start, setting the new
+ *		 table state to INIT.
+ *	   - Tablesync worker starts; changes table state from INIT to DATASYNC while
+ *		 copying.
+ *	   - Tablesync worker does initial table copy; there is a FINISHEDCOPY (sync
+ *		 worker specific) state to indicate when the copy phase has completed, so
+ *		 if the worker crashes with this (non-memory) state then the copy will not
+ *		 be re-attempted.
+ *	   - Tablesync worker then sets table state to SYNCWAIT; waits for state change.
+ *	   - Apply worker periodically checks for tables in SYNCWAIT state.  When
+ *		 any appear, it sets the table state to CATCHUP and starts loop-waiting
+ *		 until either the table state is set to SYNCDONE or the sync worker
+ *		 exits.
+ *	   - After the sync worker has seen the state change to CATCHUP, it will
+ *		 read the stream and apply changes (acting like an apply worker) until
+ *		 it catches up to the specified stream position.  Then it sets the
+ *		 state to SYNCDONE.  There might be zero changes applied between
+ *		 CATCHUP and SYNCDONE, because the sync worker might be ahead of the
+ *		 apply worker.
+ *	   - Once the state is set to SYNCDONE, the apply will continue tracking
+ *		 the table until it reaches the SYNCDONE stream position, at which
+ *		 point it sets state to READY and stops tracking.  Again, there might
+ *		 be zero changes in between.
+ *
+ *	  So the state progression is always: INIT -> DATASYNC -> FINISHEDCOPY
+ *	  -> SYNCWAIT -> CATCHUP -> SYNCDONE -> READY.
+ *
+ *	  The catalog pg_subscription_rel is used to keep information about
+ *	  subscribed tables and their state.  The catalog holds all states
+ *	  except SYNCWAIT and CATCHUP which are only in shared memory.
+ *
+ *	  Example flows look like this:
+ *	   - Apply is in front:
+ *		  sync:8
+ *			-> set in catalog FINISHEDCOPY
+ *			-> set in memory SYNCWAIT
+ *		  apply:10
+ *			-> set in memory CATCHUP
+ *			-> enter wait-loop
+ *		  sync:10
+ *			-> set in catalog SYNCDONE
+ *			-> exit
+ *		  apply:10
+ *			-> exit wait-loop
+ *			-> continue rep
+ *		  apply:11
+ *			-> set in catalog READY
+ *
+ *	   - Sync is in front:
+ *		  sync:10
+ *			-> set in catalog FINISHEDCOPY
+ *			-> set in memory SYNCWAIT
+ *		  apply:8
+ *			-> set in memory CATCHUP
+ *			-> continue per-table filtering
+ *		  sync:10
+ *			-> set in catalog SYNCDONE
+ *			-> exit
+ *		  apply:10
+ *			-> set in catalog READY
+ *			-> stop per-table filtering
+ *			-> continue rep
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/table.h"
+#include "access/xact.h"
+#include "catalog/pg_subscription_rel.h"
+#include "catalog/pg_type.h"
+#include "commands/copy.h"
+#include "miscadmin.h"
+#include "parser/parse_relation.h"
+#include "pgstat.h"
+#include "replication/logicallauncher.h"
+#include "replication/logicalrelation.h"
+#include "replication/walreceiver.h"
+#include "replication/worker_internal.h"
+#include "replication/slot.h"
+#include "replication/origin.h"
+#include "storage/ipc.h"
+#include "storage/lmgr.h"
+#include "utils/builtins.h"
+#include "utils/lsyscache.h"
+#include "utils/memutils.h"
+#include "utils/snapmgr.h"
+
+static bool table_states_valid = false;
+
+StringInfo	copybuf = NULL;
+
+/*
+ * Exit routine for synchronization worker.
+ */
+static void
+pg_attribute_noreturn()
+finish_sync_worker(void)
+{
+	/*
+	 * Commit any outstanding transaction. This is the usual case, unless
+	 * there was nothing to do for the table.
+	 */
+	if (IsTransactionState())
+	{
+		CommitTransactionCommand();
+		pgstat_report_stat(false);
+	}
+
+	/* And flush all writes. */
+	XLogFlush(GetXLogWriteRecPtr());
+
+	StartTransactionCommand();
+	ereport(LOG,
+			(errmsg("logical replication table synchronization worker for subscription \"%s\", table \"%s\" has finished",
+					MySubscription->name,
+					get_rel_name(MyLogicalRepWorker->relid))));
+	CommitTransactionCommand();
+
+	/* Find the main apply worker and signal it. */
+	logicalrep_worker_wakeup(MyLogicalRepWorker->subid, InvalidOid);
+
+	/* Stop gracefully */
+	proc_exit(0);
+}
+
+/*
+ * Wait until the relation sync state is set in the catalog to the expected
+ * one; return true when it happens.
+ *
+ * Returns false if the table sync worker or the table itself have
+ * disappeared, or the table state has been reset.
+ *
+ * Currently, this is used in the apply worker when transitioning from
+ * CATCHUP state to SYNCDONE.
+ */
+static bool
+wait_for_relation_state_change(Oid relid, char expected_state)
+{
+	char		state;
+
+	for (;;)
+	{
+		LogicalRepWorker *worker;
+		XLogRecPtr	statelsn;
+
+		CHECK_FOR_INTERRUPTS();
+
+		InvalidateCatalogSnapshot();
+		state = GetSubscriptionRelState(MyLogicalRepWorker->subid,
+										relid, &statelsn);
+
+		if (state == SUBREL_STATE_UNKNOWN)
+			break;
+
+		if (state == expected_state)
+			return true;
+
+		/* Check if the sync worker is still running and bail if not. */
+		LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
+		worker = logicalrep_worker_find(MyLogicalRepWorker->subid, relid,
+										false);
+		LWLockRelease(LogicalRepWorkerLock);
+		if (!worker)
+			break;
+
+		(void) WaitLatch(MyLatch,
+						 WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
+						 1000L, WAIT_EVENT_LOGICAL_SYNC_STATE_CHANGE);
+
+		ResetLatch(MyLatch);
+	}
+
+	return false;
+}
+
+/*
+ * Wait until the apply worker changes the state of our synchronization
+ * worker to the expected one.
+ *
+ * Used when transitioning from SYNCWAIT state to CATCHUP.
+ *
+ * Returns false if the apply worker has disappeared.
+ */
+static bool
+wait_for_worker_state_change(char expected_state)
+{
+	int			rc;
+
+	for (;;)
+	{
+		LogicalRepWorker *worker;
+
+		CHECK_FOR_INTERRUPTS();
+
+		/*
+		 * Done if already in correct state.  (We assume this fetch is atomic
+		 * enough to not give a misleading answer if we do it with no lock.)
+		 */
+		if (MyLogicalRepWorker->relstate == expected_state)
+			return true;
+
+		/*
+		 * Bail out if the apply worker has died, else signal it we're
+		 * waiting.
+		 */
+		LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
+		worker = logicalrep_worker_find(MyLogicalRepWorker->subid,
+										InvalidOid, false);
+		if (worker && worker->proc)
+			logicalrep_worker_wakeup_ptr(worker);
+		LWLockRelease(LogicalRepWorkerLock);
+		if (!worker)
+			break;
+
+		/*
+		 * Wait.  We expect to get a latch signal back from the apply worker,
+		 * but use a timeout in case it dies without sending one.
+		 */
+		rc = WaitLatch(MyLatch,
+					   WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
+					   1000L, WAIT_EVENT_LOGICAL_SYNC_STATE_CHANGE);
+
+		if (rc & WL_LATCH_SET)
+			ResetLatch(MyLatch);
+	}
+
+	return false;
+}
+
+/*
+ * Callback from syscache invalidation.
+ */
+void
+invalidate_syncing_table_states(Datum arg, int cacheid, uint32 hashvalue)
+{
+	table_states_valid = false;
+}
+
+/*
+ * Handle table synchronization cooperation from the synchronization
+ * worker.
+ *
+ * If the sync worker is in CATCHUP state and reached (or passed) the
+ * predetermined synchronization point in the WAL stream, mark the table as
+ * SYNCDONE and finish.
+ */
+static void
+process_syncing_tables_for_sync(XLogRecPtr current_lsn)
+{
+	SpinLockAcquire(&MyLogicalRepWorker->relmutex);
+
+	if (MyLogicalRepWorker->relstate == SUBREL_STATE_CATCHUP &&
+		current_lsn >= MyLogicalRepWorker->relstate_lsn)
+	{
+		TimeLineID	tli;
+		char		syncslotname[NAMEDATALEN] = {0};
+
+		MyLogicalRepWorker->relstate = SUBREL_STATE_SYNCDONE;
+		MyLogicalRepWorker->relstate_lsn = current_lsn;
+
+		SpinLockRelease(&MyLogicalRepWorker->relmutex);
+
+		/*
+		 * UpdateSubscriptionRelState must be called within a transaction.
+		 * That transaction will be ended within the finish_sync_worker().
+		 */
+		if (!IsTransactionState())
+			StartTransactionCommand();
+
+		UpdateSubscriptionRelState(MyLogicalRepWorker->subid,
+								   MyLogicalRepWorker->relid,
+								   MyLogicalRepWorker->relstate,
+								   MyLogicalRepWorker->relstate_lsn);
+
+		/*
+		 * End streaming so that LogRepWorkerWalRcvConn can be used to drop
+		 * the slot.
+		 */
+		walrcv_endstreaming(LogRepWorkerWalRcvConn, &tli);
+
+		/*
+		 * Cleanup the tablesync slot.
+		 *
+		 * This has to be done after updating the state because otherwise if
+		 * there is an error while doing the database operations we won't be
+		 * able to rollback dropped slot.
+		 */
+		ReplicationSlotNameForTablesync(MyLogicalRepWorker->subid,
+										MyLogicalRepWorker->relid,
+										syncslotname,
+										sizeof(syncslotname));
+
+		/*
+		 * It is important to give an error if we are unable to drop the slot,
+		 * otherwise, it won't be dropped till the corresponding subscription
+		 * is dropped. So passing missing_ok = false.
+		 */
+		ReplicationSlotDropAtPubNode(LogRepWorkerWalRcvConn, syncslotname, false);
+
+		finish_sync_worker();
+	}
+	else
+		SpinLockRelease(&MyLogicalRepWorker->relmutex);
+}
+
+/*
+ * Handle table synchronization cooperation from the apply worker.
+ *
+ * Walk over all subscription tables that are individually tracked by the
+ * apply process (currently, all that have state other than
+ * SUBREL_STATE_READY) and manage synchronization for them.
+ *
+ * If there are tables that need synchronizing and are not being synchronized
+ * yet, start sync workers for them (if there are free slots for sync
+ * workers).  To prevent starting the sync worker for the same relation at a
+ * high frequency after a failure, we store its last start time with each sync
+ * state info.  We start the sync worker for the same relation after waiting
+ * at least wal_retrieve_retry_interval.
+ *
+ * For tables that are being synchronized already, check if sync workers
+ * either need action from the apply worker or have finished.  This is the
+ * SYNCWAIT to CATCHUP transition.
+ *
+ * If the synchronization position is reached (SYNCDONE), then the table can
+ * be marked as READY and is no longer tracked.
+ */
+static void
+process_syncing_tables_for_apply(XLogRecPtr current_lsn)
+{
+	struct tablesync_start_time_mapping
+	{
+		Oid			relid;
+		TimestampTz last_start_time;
+	};
+	static List *table_states = NIL;
+	static HTAB *last_start_times = NULL;
+	ListCell   *lc;
+	bool		started_tx = false;
+
+	Assert(!IsTransactionState());
+
+	/* We need up-to-date sync state info for subscription tables here. */
+	if (!table_states_valid)
+	{
+		MemoryContext oldctx;
+		List	   *rstates;
+		ListCell   *lc;
+		SubscriptionRelState *rstate;
+
+		/* Clean the old list. */
+		list_free_deep(table_states);
+		table_states = NIL;
+
+		StartTransactionCommand();
+		started_tx = true;
+
+		/* Fetch all non-ready tables. */
+		rstates = GetSubscriptionNotReadyRelations(MySubscription->oid);
+
+		/* Allocate the tracking info in a permanent memory context. */
+		oldctx = MemoryContextSwitchTo(CacheMemoryContext);
+		foreach(lc, rstates)
+		{
+			rstate = palloc(sizeof(SubscriptionRelState));
+			memcpy(rstate, lfirst(lc), sizeof(SubscriptionRelState));
+			table_states = lappend(table_states, rstate);
+		}
+		MemoryContextSwitchTo(oldctx);
+
+		table_states_valid = true;
+	}
+
+	/*
+	 * Prepare a hash table for tracking last start times of workers, to avoid
+	 * immediate restarts.  We don't need it if there are no tables that need
+	 * syncing.
+	 */
+	if (table_states && !last_start_times)
+	{
+		HASHCTL		ctl;
+
+		ctl.keysize = sizeof(Oid);
+		ctl.entrysize = sizeof(struct tablesync_start_time_mapping);
+		last_start_times = hash_create("Logical replication table sync worker start times",
+									   256, &ctl, HASH_ELEM | HASH_BLOBS);
+	}
+
+	/*
+	 * Clean up the hash table when we're done with all tables (just to
+	 * release the bit of memory).
+	 */
+	else if (!table_states && last_start_times)
+	{
+		hash_destroy(last_start_times);
+		last_start_times = NULL;
+	}
+
+	/*
+	 * Process all tables that are being synchronized.
+	 */
+	foreach(lc, table_states)
+	{
+		SubscriptionRelState *rstate = (SubscriptionRelState *) lfirst(lc);
+
+		if (rstate->state == SUBREL_STATE_SYNCDONE)
+		{
+			/*
+			 * Apply has caught up to the position where the table sync has
+			 * finished.  Mark the table as ready so that the apply will just
+			 * continue to replicate it normally.
+			 */
+			if (current_lsn >= rstate->lsn)
+			{
+				char		originname[NAMEDATALEN];
+
+				rstate->state = SUBREL_STATE_READY;
+				rstate->lsn = current_lsn;
+				if (!started_tx)
+				{
+					StartTransactionCommand();
+					started_tx = true;
+				}
+
+				/*
+				 * Remove the tablesync origin tracking if exists.
+				 *
+				 * The normal case origin drop is done here instead of in the
+				 * process_syncing_tables_for_sync function because we don't
+				 * allow to drop the origin till the process owning the origin
+				 * is alive.
+				 *
+				 * There is a chance that the user is concurrently performing
+				 * refresh for the subscription where we remove the table
+				 * state and its origin and by this time the origin might be
+				 * already removed. So passing missing_ok = true.
+				 */
+				ReplicationOriginNameForTablesync(MyLogicalRepWorker->subid,
+												  rstate->relid,
+												  originname,
+												  sizeof(originname));
+				replorigin_drop_by_name(originname, true, false);
+
+				/*
+				 * Update the state to READY only after the origin cleanup.
+				 */
+				UpdateSubscriptionRelState(MyLogicalRepWorker->subid,
+										   rstate->relid, rstate->state,
+										   rstate->lsn);
+			}
+		}
+		else
+		{
+			LogicalRepWorker *syncworker;
+
+			/*
+			 * Look for a sync worker for this relation.
+			 */
+			LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
+
+			syncworker = logicalrep_worker_find(MyLogicalRepWorker->subid,
+												rstate->relid, false);
+
+			if (syncworker)
+			{
+				/* Found one, update our copy of its state */
+				SpinLockAcquire(&syncworker->relmutex);
+				rstate->state = syncworker->relstate;
+				rstate->lsn = syncworker->relstate_lsn;
+				if (rstate->state == SUBREL_STATE_SYNCWAIT)
+				{
+					/*
+					 * Sync worker is waiting for apply.  Tell sync worker it
+					 * can catchup now.
+					 */
+					syncworker->relstate = SUBREL_STATE_CATCHUP;
+					syncworker->relstate_lsn =
+						Max(syncworker->relstate_lsn, current_lsn);
+				}
+				SpinLockRelease(&syncworker->relmutex);
+
+				/* If we told worker to catch up, wait for it. */
+				if (rstate->state == SUBREL_STATE_SYNCWAIT)
+				{
+					/* Signal the sync worker, as it may be waiting for us. */
+					if (syncworker->proc)
+						logicalrep_worker_wakeup_ptr(syncworker);
+
+					/* Now safe to release the LWLock */
+					LWLockRelease(LogicalRepWorkerLock);
+
+					/*
+					 * Enter busy loop and wait for synchronization worker to
+					 * reach expected state (or die trying).
+					 */
+					if (!started_tx)
+					{
+						StartTransactionCommand();
+						started_tx = true;
+					}
+
+					wait_for_relation_state_change(rstate->relid,
+												   SUBREL_STATE_SYNCDONE);
+				}
+				else
+					LWLockRelease(LogicalRepWorkerLock);
+			}
+			else
+			{
+				/*
+				 * If there is no sync worker for this table yet, count
+				 * running sync workers for this subscription, while we have
+				 * the lock.
+				 */
+				int			nsyncworkers =
+				logicalrep_sync_worker_count(MyLogicalRepWorker->subid);
+
+				/* Now safe to release the LWLock */
+				LWLockRelease(LogicalRepWorkerLock);
+
+				/*
+				 * If there are free sync worker slot(s), start a new sync
+				 * worker for the table.
+				 */
+				if (nsyncworkers < max_sync_workers_per_subscription)
+				{
+					TimestampTz now = GetCurrentTimestamp();
+					struct tablesync_start_time_mapping *hentry;
+					bool		found;
+
+					hentry = hash_search(last_start_times, &rstate->relid,
+										 HASH_ENTER, &found);
+
+					if (!found ||
+						TimestampDifferenceExceeds(hentry->last_start_time, now,
+												   wal_retrieve_retry_interval))
+					{
+						logicalrep_worker_launch(MyLogicalRepWorker->dbid,
+												 MySubscription->oid,
+												 MySubscription->name,
+												 MyLogicalRepWorker->userid,
+												 rstate->relid);
+						hentry->last_start_time = now;
+					}
+				}
+			}
+		}
+	}
+
+	if (started_tx)
+	{
+		CommitTransactionCommand();
+		pgstat_report_stat(false);
+	}
+}
+
+/*
+ * Process possible state change(s) of tables that are being synchronized.
+ */
+void
+process_syncing_tables(XLogRecPtr current_lsn)
+{
+	if (am_tablesync_worker())
+		process_syncing_tables_for_sync(current_lsn);
+	else
+		process_syncing_tables_for_apply(current_lsn);
+}
+
+/*
+ * Create list of columns for COPY based on logical relation mapping.
+ */
+static List *
+make_copy_attnamelist(LogicalRepRelMapEntry *rel)
+{
+	List	   *attnamelist = NIL;
+	int			i;
+
+	for (i = 0; i < rel->remoterel.natts; i++)
+	{
+		attnamelist = lappend(attnamelist,
+							  makeString(rel->remoterel.attnames[i]));
+	}
+
+
+	return attnamelist;
+}
+
+/*
+ * Data source callback for the COPY FROM, which reads from the remote
+ * connection and passes the data back to our local COPY.
+ */
+static int
+copy_read_data(void *outbuf, int minread, int maxread)
+{
+	int			bytesread = 0;
+	int			avail;
+
+	/* If there are some leftover data from previous read, use it. */
+	avail = copybuf->len - copybuf->cursor;
+	if (avail)
+	{
+		if (avail > maxread)
+			avail = maxread;
+		memcpy(outbuf, &copybuf->data[copybuf->cursor], avail);
+		copybuf->cursor += avail;
+		maxread -= avail;
+		bytesread += avail;
+	}
+
+	while (maxread > 0 && bytesread < minread)
+	{
+		pgsocket	fd = PGINVALID_SOCKET;
+		int			len;
+		char	   *buf = NULL;
+
+		for (;;)
+		{
+			/* Try read the data. */
+			len = walrcv_receive(LogRepWorkerWalRcvConn, &buf, &fd);
+
+			CHECK_FOR_INTERRUPTS();
+
+			if (len == 0)
+				break;
+			else if (len < 0)
+				return bytesread;
+			else
+			{
+				/* Process the data */
+				copybuf->data = buf;
+				copybuf->len = len;
+				copybuf->cursor = 0;
+
+				avail = copybuf->len - copybuf->cursor;
+				if (avail > maxread)
+					avail = maxread;
+				memcpy(outbuf, &copybuf->data[copybuf->cursor], avail);
+				outbuf = (void *) ((char *) outbuf + avail);
+				copybuf->cursor += avail;
+				maxread -= avail;
+				bytesread += avail;
+			}
+
+			if (maxread <= 0 || bytesread >= minread)
+				return bytesread;
+		}
+
+		/*
+		 * Wait for more data or latch.
+		 */
+		(void) WaitLatchOrSocket(MyLatch,
+								 WL_SOCKET_READABLE | WL_LATCH_SET |
+								 WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
+								 fd, 1000L, WAIT_EVENT_LOGICAL_SYNC_DATA);
+
+		ResetLatch(MyLatch);
+	}
+
+	return bytesread;
+}
+
+
+/*
+ * Get information about remote relation in similar fashion the RELATION
+ * message provides during replication.
+ */
+static void
+fetch_remote_table_info(char *nspname, char *relname,
+						LogicalRepRelation *lrel)
+{
+	WalRcvExecResult *res;
+	StringInfoData cmd;
+	TupleTableSlot *slot;
+	Oid			tableRow[] = {OIDOID, CHAROID, CHAROID};
+	Oid			attrRow[] = {TEXTOID, OIDOID, BOOLOID};
+	bool		isnull;
+	int			natt;
+
+	lrel->nspname = nspname;
+	lrel->relname = relname;
+
+	/* First fetch Oid and replica identity. */
+	initStringInfo(&cmd);
+	appendStringInfo(&cmd, "SELECT c.oid, c.relreplident, c.relkind"
+					 "  FROM pg_catalog.pg_class c"
+					 "  INNER JOIN pg_catalog.pg_namespace n"
+					 "        ON (c.relnamespace = n.oid)"
+					 " WHERE n.nspname = %s"
+					 "   AND c.relname = %s",
+					 quote_literal_cstr(nspname),
+					 quote_literal_cstr(relname));
+	res = walrcv_exec(LogRepWorkerWalRcvConn, cmd.data,
+					  lengthof(tableRow), tableRow);
+
+	if (res->status != WALRCV_OK_TUPLES)
+		ereport(ERROR,
+				(errcode(ERRCODE_CONNECTION_FAILURE),
+				 errmsg("could not fetch table info for table \"%s.%s\" from publisher: %s",
+						nspname, relname, res->err)));
+
+	slot = MakeSingleTupleTableSlot(res->tupledesc, &TTSOpsMinimalTuple);
+	if (!tuplestore_gettupleslot(res->tuplestore, true, false, slot))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("table \"%s.%s\" not found on publisher",
+						nspname, relname)));
+
+	lrel->remoteid = DatumGetObjectId(slot_getattr(slot, 1, &isnull));
+	Assert(!isnull);
+	lrel->replident = DatumGetChar(slot_getattr(slot, 2, &isnull));
+	Assert(!isnull);
+	lrel->relkind = DatumGetChar(slot_getattr(slot, 3, &isnull));
+	Assert(!isnull);
+
+	ExecDropSingleTupleTableSlot(slot);
+	walrcv_clear_result(res);
+
+	/* Now fetch columns. */
+	resetStringInfo(&cmd);
+	appendStringInfo(&cmd,
+					 "SELECT a.attname,"
+					 "       a.atttypid,"
+					 "       a.attnum = ANY(i.indkey)"
+					 "  FROM pg_catalog.pg_attribute a"
+					 "  LEFT JOIN pg_catalog.pg_index i"
+					 "       ON (i.indexrelid = pg_get_replica_identity_index(%u))"
+					 " WHERE a.attnum > 0::pg_catalog.int2"
+					 "   AND NOT a.attisdropped %s"
+					 "   AND a.attrelid = %u"
+					 " ORDER BY a.attnum",
+					 lrel->remoteid,
+					 (walrcv_server_version(LogRepWorkerWalRcvConn) >= 120000 ?
+					  "AND a.attgenerated = ''" : ""),
+					 lrel->remoteid);
+	res = walrcv_exec(LogRepWorkerWalRcvConn, cmd.data,
+					  lengthof(attrRow), attrRow);
+
+	if (res->status != WALRCV_OK_TUPLES)
+		ereport(ERROR,
+				(errcode(ERRCODE_CONNECTION_FAILURE),
+				 errmsg("could not fetch table info for table \"%s.%s\" from publisher: %s",
+						nspname, relname, res->err)));
+
+	/* We don't know the number of rows coming, so allocate enough space. */
+	lrel->attnames = palloc0(MaxTupleAttributeNumber * sizeof(char *));
+	lrel->atttyps = palloc0(MaxTupleAttributeNumber * sizeof(Oid));
+	lrel->attkeys = NULL;
+
+	natt = 0;
+	slot = MakeSingleTupleTableSlot(res->tupledesc, &TTSOpsMinimalTuple);
+	while (tuplestore_gettupleslot(res->tuplestore, true, false, slot))
+	{
+		lrel->attnames[natt] =
+			TextDatumGetCString(slot_getattr(slot, 1, &isnull));
+		Assert(!isnull);
+		lrel->atttyps[natt] = DatumGetObjectId(slot_getattr(slot, 2, &isnull));
+		Assert(!isnull);
+		if (DatumGetBool(slot_getattr(slot, 3, &isnull)))
+			lrel->attkeys = bms_add_member(lrel->attkeys, natt);
+
+		/* Should never happen. */
+		if (++natt >= MaxTupleAttributeNumber)
+			elog(ERROR, "too many columns in remote table \"%s.%s\"",
+				 nspname, relname);
+
+		ExecClearTuple(slot);
+	}
+	ExecDropSingleTupleTableSlot(slot);
+
+	lrel->natts = natt;
+
+	walrcv_clear_result(res);
+	pfree(cmd.data);
+}
+
+/*
+ * Copy existing data of a table from publisher.
+ *
+ * Caller is responsible for locking the local relation.
+ */
+static void
+copy_table(Relation rel)
+{
+	LogicalRepRelMapEntry *relmapentry;
+	LogicalRepRelation lrel;
+	WalRcvExecResult *res;
+	StringInfoData cmd;
+	CopyFromState cstate;
+	List	   *attnamelist;
+	ParseState *pstate;
+
+	/* Get the publisher relation info. */
+	fetch_remote_table_info(get_namespace_name(RelationGetNamespace(rel)),
+							RelationGetRelationName(rel), &lrel);
+
+	/* Put the relation into relmap. */
+	logicalrep_relmap_update(&lrel);
+
+	/* Map the publisher relation to local one. */
+	relmapentry = logicalrep_rel_open(lrel.remoteid, NoLock);
+	Assert(rel == relmapentry->localrel);
+
+	/* Start copy on the publisher. */
+	initStringInfo(&cmd);
+	if (lrel.relkind == RELKIND_RELATION)
+		appendStringInfo(&cmd, "COPY %s TO STDOUT",
+						 quote_qualified_identifier(lrel.nspname, lrel.relname));
+	else
+	{
+		/*
+		 * For non-tables, we need to do COPY (SELECT ...), but we can't just
+		 * do SELECT * because we need to not copy generated columns.
+		 */
+		appendStringInfoString(&cmd, "COPY (SELECT ");
+		for (int i = 0; i < lrel.natts; i++)
+		{
+			appendStringInfoString(&cmd, quote_identifier(lrel.attnames[i]));
+			if (i < lrel.natts - 1)
+				appendStringInfoString(&cmd, ", ");
+		}
+		appendStringInfo(&cmd, " FROM %s) TO STDOUT",
+						 quote_qualified_identifier(lrel.nspname, lrel.relname));
+	}
+	res = walrcv_exec(LogRepWorkerWalRcvConn, cmd.data, 0, NULL);
+	pfree(cmd.data);
+	if (res->status != WALRCV_OK_COPY_OUT)
+		ereport(ERROR,
+				(errcode(ERRCODE_CONNECTION_FAILURE),
+				 errmsg("could not start initial contents copy for table \"%s.%s\": %s",
+						lrel.nspname, lrel.relname, res->err)));
+	walrcv_clear_result(res);
+
+	copybuf = makeStringInfo();
+
+	pstate = make_parsestate(NULL);
+	(void) addRangeTableEntryForRelation(pstate, rel, AccessShareLock,
+										 NULL, false, false);
+
+	attnamelist = make_copy_attnamelist(relmapentry);
+	cstate = BeginCopyFrom(pstate, rel, NULL, NULL, false, copy_read_data, attnamelist, NIL);
+
+	/* Do the copy */
+	(void) CopyFrom(cstate);
+
+	logicalrep_rel_close(relmapentry, NoLock);
+}
+
+/*
+ * Determine the tablesync slot name.
+ *
+ * The name must not exceed NAMEDATALEN - 1 because of remote node constraints
+ * on slot name length. We append system_identifier to avoid slot_name
+ * collision with subscriptions in other clusters. With the current scheme
+ * pg_%u_sync_%u_UINT64_FORMAT (3 + 10 + 6 + 10 + 20 + '\0'), the maximum
+ * length of slot_name will be 50.
+ *
+ * The returned slot name is stored in the supplied buffer (syncslotname) with
+ * the given size.
+ *
+ * Note: We don't use the subscription slot name as part of tablesync slot name
+ * because we are responsible for cleaning up these slots and it could become
+ * impossible to recalculate what name to cleanup if the subscription slot name
+ * had changed.
+ */
+void
+ReplicationSlotNameForTablesync(Oid suboid, Oid relid,
+								char *syncslotname, int szslot)
+{
+	snprintf(syncslotname, szslot, "pg_%u_sync_%u_" UINT64_FORMAT, suboid,
+			 relid, GetSystemIdentifier());
+}
+
+/*
+ * Form the origin name for tablesync.
+ *
+ * Return the name in the supplied buffer.
+ */
+void
+ReplicationOriginNameForTablesync(Oid suboid, Oid relid,
+								  char *originname, int szorgname)
+{
+	snprintf(originname, szorgname, "pg_%u_%u", suboid, relid);
+}
+
+/*
+ * Start syncing the table in the sync worker.
+ *
+ * If nothing needs to be done to sync the table, we exit the worker without
+ * any further action.
+ *
+ * The returned slot name is palloc'ed in current memory context.
+ */
+char *
+LogicalRepSyncTableStart(XLogRecPtr *origin_startpos)
+{
+	char	   *slotname;
+	char	   *err;
+	char		relstate;
+	XLogRecPtr	relstate_lsn;
+	Relation	rel;
+	WalRcvExecResult *res;
+	char		originname[NAMEDATALEN];
+	RepOriginId originid;
+
+	/* Check the state of the table synchronization. */
+	StartTransactionCommand();
+	relstate = GetSubscriptionRelState(MyLogicalRepWorker->subid,
+									   MyLogicalRepWorker->relid,
+									   &relstate_lsn);
+	CommitTransactionCommand();
+
+	SpinLockAcquire(&MyLogicalRepWorker->relmutex);
+	MyLogicalRepWorker->relstate = relstate;
+	MyLogicalRepWorker->relstate_lsn = relstate_lsn;
+	SpinLockRelease(&MyLogicalRepWorker->relmutex);
+
+	/*
+	 * If synchronization is already done or no longer necessary, exit now
+	 * that we've updated shared memory state.
+	 */
+	switch (relstate)
+	{
+		case SUBREL_STATE_SYNCDONE:
+		case SUBREL_STATE_READY:
+		case SUBREL_STATE_UNKNOWN:
+			finish_sync_worker();	/* doesn't return */
+	}
+
+	/* Calculate the name of the tablesync slot. */
+	slotname = (char *) palloc(NAMEDATALEN);
+	ReplicationSlotNameForTablesync(MySubscription->oid,
+									MyLogicalRepWorker->relid,
+									slotname,
+									NAMEDATALEN);
+
+	/*
+	 * Here we use the slot name instead of the subscription name as the
+	 * application_name, so that it is different from the main apply worker,
+	 * so that synchronous replication can distinguish them.
+	 */
+	LogRepWorkerWalRcvConn =
+		walrcv_connect(MySubscription->conninfo, true, slotname, &err);
+	if (LogRepWorkerWalRcvConn == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_CONNECTION_FAILURE),
+				 errmsg("could not connect to the publisher: %s", err)));
+
+	Assert(MyLogicalRepWorker->relstate == SUBREL_STATE_INIT ||
+		   MyLogicalRepWorker->relstate == SUBREL_STATE_DATASYNC ||
+		   MyLogicalRepWorker->relstate == SUBREL_STATE_FINISHEDCOPY);
+
+	/* Assign the origin tracking record name. */
+	ReplicationOriginNameForTablesync(MySubscription->oid,
+									  MyLogicalRepWorker->relid,
+									  originname,
+									  sizeof(originname));
+
+	if (MyLogicalRepWorker->relstate == SUBREL_STATE_DATASYNC)
+	{
+		/*
+		 * We have previously errored out before finishing the copy so the
+		 * replication slot might exist. We want to remove the slot if it
+		 * already exists and proceed.
+		 *
+		 * XXX We could also instead try to drop the slot, last time we failed
+		 * but for that, we might need to clean up the copy state as it might
+		 * be in the middle of fetching the rows. Also, if there is a network
+		 * breakdown then it wouldn't have succeeded so trying it next time
+		 * seems like a better bet.
+		 */
+		ReplicationSlotDropAtPubNode(LogRepWorkerWalRcvConn, slotname, true);
+	}
+	else if (MyLogicalRepWorker->relstate == SUBREL_STATE_FINISHEDCOPY)
+	{
+		/*
+		 * The COPY phase was previously done, but tablesync then crashed
+		 * before it was able to finish normally.
+		 */
+		StartTransactionCommand();
+
+		/*
+		 * The origin tracking name must already exist. It was created first
+		 * time this tablesync was launched.
+		 */
+		originid = replorigin_by_name(originname, false);
+		replorigin_session_setup(originid);
+		replorigin_session_origin = originid;
+		*origin_startpos = replorigin_session_get_progress(false);
+
+		CommitTransactionCommand();
+
+		goto copy_table_done;
+	}
+
+	SpinLockAcquire(&MyLogicalRepWorker->relmutex);
+	MyLogicalRepWorker->relstate = SUBREL_STATE_DATASYNC;
+	MyLogicalRepWorker->relstate_lsn = InvalidXLogRecPtr;
+	SpinLockRelease(&MyLogicalRepWorker->relmutex);
+
+	/* Update the state and make it visible to others. */
+	StartTransactionCommand();
+	UpdateSubscriptionRelState(MyLogicalRepWorker->subid,
+							   MyLogicalRepWorker->relid,
+							   MyLogicalRepWorker->relstate,
+							   MyLogicalRepWorker->relstate_lsn);
+	CommitTransactionCommand();
+	pgstat_report_stat(false);
+
+	StartTransactionCommand();
+
+	/*
+	 * Use a standard write lock here. It might be better to disallow access
+	 * to the table while it's being synchronized. But we don't want to block
+	 * the main apply process from working and it has to open the relation in
+	 * RowExclusiveLock when remapping remote relation id to local one.
+	 */
+	rel = table_open(MyLogicalRepWorker->relid, RowExclusiveLock);
+
+	/*
+	 * Start a transaction in the remote node in REPEATABLE READ mode.  This
+	 * ensures that both the replication slot we create (see below) and the
+	 * COPY are consistent with each other.
+	 */
+	res = walrcv_exec(LogRepWorkerWalRcvConn,
+					  "BEGIN READ ONLY ISOLATION LEVEL REPEATABLE READ",
+					  0, NULL);
+	if (res->status != WALRCV_OK_COMMAND)
+		ereport(ERROR,
+				(errcode(ERRCODE_CONNECTION_FAILURE),
+				 errmsg("table copy could not start transaction on publisher: %s",
+						res->err)));
+	walrcv_clear_result(res);
+
+	/*
+	 * Create a new permanent logical decoding slot. This slot will be used
+	 * for the catchup phase after COPY is done, so tell it to use the
+	 * snapshot to make the final data consistent.
+	 *
+	 * Prevent cancel/die interrupts while creating slot here because it is
+	 * possible that before the server finishes this command, a concurrent
+	 * drop subscription happens which would complete without removing this
+	 * slot leading to a dangling slot on the server.
+	 */
+	HOLD_INTERRUPTS();
+	walrcv_create_slot(LogRepWorkerWalRcvConn, slotname, false /* permanent */ ,
+					   CRS_USE_SNAPSHOT, origin_startpos);
+	RESUME_INTERRUPTS();
+
+	/*
+	 * Setup replication origin tracking. The purpose of doing this before the
+	 * copy is to avoid doing the copy again due to any error in setting up
+	 * origin tracking.
+	 */
+	originid = replorigin_by_name(originname, true);
+	if (!OidIsValid(originid))
+	{
+		/*
+		 * Origin tracking does not exist, so create it now.
+		 *
+		 * Then advance to the LSN got from walrcv_create_slot. This is WAL
+		 * logged for the purpose of recovery. Locks are to prevent the
+		 * replication origin from vanishing while advancing.
+		 */
+		originid = replorigin_create(originname);
+
+		LockRelationOid(ReplicationOriginRelationId, RowExclusiveLock);
+		replorigin_advance(originid, *origin_startpos, InvalidXLogRecPtr,
+						   true /* go backward */ , true /* WAL log */ );
+		UnlockRelationOid(ReplicationOriginRelationId, RowExclusiveLock);
+
+		replorigin_session_setup(originid);
+		replorigin_session_origin = originid;
+	}
+	else
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_DUPLICATE_OBJECT),
+				 errmsg("replication origin \"%s\" already exists",
+						originname)));
+	}
+
+	/* Now do the initial data copy */
+	PushActiveSnapshot(GetTransactionSnapshot());
+	copy_table(rel);
+	PopActiveSnapshot();
+
+	res = walrcv_exec(LogRepWorkerWalRcvConn, "COMMIT", 0, NULL);
+	if (res->status != WALRCV_OK_COMMAND)
+		ereport(ERROR,
+				(errcode(ERRCODE_CONNECTION_FAILURE),
+				 errmsg("table copy could not finish transaction on publisher: %s",
+						res->err)));
+	walrcv_clear_result(res);
+
+	table_close(rel, NoLock);
+
+	/* Make the copy visible. */
+	CommandCounterIncrement();
+
+	/*
+	 * Update the persisted state to indicate the COPY phase is done; make it
+	 * visible to others.
+	 */
+	UpdateSubscriptionRelState(MyLogicalRepWorker->subid,
+							   MyLogicalRepWorker->relid,
+							   SUBREL_STATE_FINISHEDCOPY,
+							   MyLogicalRepWorker->relstate_lsn);
+
+	CommitTransactionCommand();
+
+copy_table_done:
+
+	elog(DEBUG1,
+		 "LogicalRepSyncTableStart: '%s' origin_startpos lsn %X/%X",
+		 originname, LSN_FORMAT_ARGS(*origin_startpos));
+
+	/*
+	 * We are done with the initial data synchronization, update the state.
+	 */
+	SpinLockAcquire(&MyLogicalRepWorker->relmutex);
+	MyLogicalRepWorker->relstate = SUBREL_STATE_SYNCWAIT;
+	MyLogicalRepWorker->relstate_lsn = *origin_startpos;
+	SpinLockRelease(&MyLogicalRepWorker->relmutex);
+
+	/*
+	 * Finally, wait until the main apply worker tells us to catch up and then
+	 * return to let LogicalRepApplyLoop do it.
+	 */
+	wait_for_worker_state_change(SUBREL_STATE_CATCHUP);
+	return slotname;
+}
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
new file mode 100644
index 0000000..8c9a4b5
--- /dev/null
+++ b/src/backend/replication/logical/worker.c
@@ -0,0 +1,3254 @@
+/*-------------------------------------------------------------------------
+ * worker.c
+ *	   PostgreSQL logical replication worker (apply)
+ *
+ * Copyright (c) 2016-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/worker.c
+ *
+ * NOTES
+ *	  This file contains the worker which applies logical changes as they come
+ *	  from remote logical replication stream.
+ *
+ *	  The main worker (apply) is started by logical replication worker
+ *	  launcher for every enabled subscription in a database. It uses
+ *	  walsender protocol to communicate with publisher.
+ *
+ *	  This module includes server facing code and shares libpqwalreceiver
+ *	  module with walreceiver for providing the libpq specific functionality.
+ *
+ *
+ * STREAMED TRANSACTIONS
+ * ---------------------
+ * Streamed transactions (large transactions exceeding a memory limit on the
+ * upstream) are not applied immediately, but instead, the data is written
+ * to temporary files and then applied at once when the final commit arrives.
+ *
+ * Unlike the regular (non-streamed) case, handling streamed transactions has
+ * to handle aborts of both the toplevel transaction and subtransactions. This
+ * is achieved by tracking offsets for subtransactions, which is then used
+ * to truncate the file with serialized changes.
+ *
+ * The files are placed in tmp file directory by default, and the filenames
+ * include both the XID of the toplevel transaction and OID of the
+ * subscription. This is necessary so that different workers processing a
+ * remote transaction with the same XID doesn't interfere.
+ *
+ * We use BufFiles instead of using normal temporary files because (a) the
+ * BufFile infrastructure supports temporary files that exceed the OS file size
+ * limit, (b) provides a way for automatic clean up on the error and (c) provides
+ * a way to survive these files across local transactions and allow to open and
+ * close at stream start and close. We decided to use SharedFileSet
+ * infrastructure as without that it deletes the files on the closure of the
+ * file and if we decide to keep stream files open across the start/stop stream
+ * then it will consume a lot of memory (more than 8K for each BufFile and
+ * there could be multiple such BufFiles as the subscriber could receive
+ * multiple start/stop streams for different transactions before getting the
+ * commit). Moreover, if we don't use SharedFileSet then we also need to invent
+ * a new way to pass filenames to BufFile APIs so that we are allowed to open
+ * the file we desired across multiple stream-open calls for the same
+ * transaction.
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "access/table.h"
+#include "access/tableam.h"
+#include "access/xact.h"
+#include "access/xlog_internal.h"
+#include "catalog/catalog.h"
+#include "catalog/namespace.h"
+#include "catalog/partition.h"
+#include "catalog/pg_inherits.h"
+#include "catalog/pg_subscription.h"
+#include "catalog/pg_subscription_rel.h"
+#include "catalog/pg_tablespace.h"
+#include "commands/tablecmds.h"
+#include "commands/tablespace.h"
+#include "commands/trigger.h"
+#include "executor/executor.h"
+#include "executor/execPartition.h"
+#include "executor/nodeModifyTable.h"
+#include "funcapi.h"
+#include "libpq/pqformat.h"
+#include "libpq/pqsignal.h"
+#include "mb/pg_wchar.h"
+#include "miscadmin.h"
+#include "nodes/makefuncs.h"
+#include "optimizer/optimizer.h"
+#include "pgstat.h"
+#include "postmaster/bgworker.h"
+#include "postmaster/interrupt.h"
+#include "postmaster/postmaster.h"
+#include "postmaster/walwriter.h"
+#include "replication/decode.h"
+#include "replication/logical.h"
+#include "replication/logicalproto.h"
+#include "replication/logicalrelation.h"
+#include "replication/logicalworker.h"
+#include "replication/origin.h"
+#include "replication/reorderbuffer.h"
+#include "replication/snapbuild.h"
+#include "replication/walreceiver.h"
+#include "replication/worker_internal.h"
+#include "rewrite/rewriteHandler.h"
+#include "storage/buffile.h"
+#include "storage/bufmgr.h"
+#include "storage/fd.h"
+#include "storage/ipc.h"
+#include "storage/lmgr.h"
+#include "storage/proc.h"
+#include "storage/procarray.h"
+#include "tcop/tcopprot.h"
+#include "utils/builtins.h"
+#include "utils/catcache.h"
+#include "utils/dynahash.h"
+#include "utils/datum.h"
+#include "utils/fmgroids.h"
+#include "utils/guc.h"
+#include "utils/inval.h"
+#include "utils/lsyscache.h"
+#include "utils/memutils.h"
+#include "utils/rel.h"
+#include "utils/syscache.h"
+#include "utils/timeout.h"
+
+#define NAPTIME_PER_CYCLE 1000	/* max sleep time between cycles (1s) */
+
+typedef struct FlushPosition
+{
+	dlist_node	node;
+	XLogRecPtr	local_end;
+	XLogRecPtr	remote_end;
+} FlushPosition;
+
+static dlist_head lsn_mapping = DLIST_STATIC_INIT(lsn_mapping);
+
+typedef struct SlotErrCallbackArg
+{
+	LogicalRepRelMapEntry *rel;
+	int			remote_attnum;
+} SlotErrCallbackArg;
+
+typedef struct ApplyExecutionData
+{
+	EState	   *estate;			/* executor state, used to track resources */
+
+	LogicalRepRelMapEntry *targetRel;	/* replication target rel */
+	ResultRelInfo *targetRelInfo;	/* ResultRelInfo for same */
+
+	/* These fields are used when the target relation is partitioned: */
+	ModifyTableState *mtstate;	/* dummy ModifyTable state */
+	PartitionTupleRouting *proute;	/* partition routing info */
+} ApplyExecutionData;
+
+/*
+ * Stream xid hash entry. Whenever we see a new xid we create this entry in the
+ * xidhash and along with it create the streaming file and store the fileset handle.
+ * The subxact file is created iff there is any subxact info under this xid. This
+ * entry is used on the subsequent streams for the xid to get the corresponding
+ * fileset handles, so storing them in hash makes the search faster.
+ */
+typedef struct StreamXidHash
+{
+	TransactionId xid;			/* xid is the hash key and must be first */
+	SharedFileSet *stream_fileset;	/* shared file set for stream data */
+	SharedFileSet *subxact_fileset; /* shared file set for subxact info */
+} StreamXidHash;
+
+static MemoryContext ApplyMessageContext = NULL;
+MemoryContext ApplyContext = NULL;
+
+/* per stream context for streaming transactions */
+static MemoryContext LogicalStreamingContext = NULL;
+
+WalReceiverConn *LogRepWorkerWalRcvConn = NULL;
+
+Subscription *MySubscription = NULL;
+bool		MySubscriptionValid = false;
+
+bool		in_remote_transaction = false;
+static XLogRecPtr remote_final_lsn = InvalidXLogRecPtr;
+
+/* fields valid only when processing streamed transaction */
+static bool in_streamed_transaction = false;
+
+static TransactionId stream_xid = InvalidTransactionId;
+
+/*
+ * Hash table for storing the streaming xid information along with shared file
+ * set for streaming and subxact files.
+ */
+static HTAB *xidhash = NULL;
+
+/* BufFile handle of the current streaming file */
+static BufFile *stream_fd = NULL;
+
+typedef struct SubXactInfo
+{
+	TransactionId xid;			/* XID of the subxact */
+	int			fileno;			/* file number in the buffile */
+	off_t		offset;			/* offset in the file */
+} SubXactInfo;
+
+/* Sub-transaction data for the current streaming transaction */
+typedef struct ApplySubXactData
+{
+	uint32		nsubxacts;		/* number of sub-transactions */
+	uint32		nsubxacts_max;	/* current capacity of subxacts */
+	TransactionId subxact_last; /* xid of the last sub-transaction */
+	SubXactInfo *subxacts;		/* sub-xact offset in changes file */
+} ApplySubXactData;
+
+static ApplySubXactData subxact_data = {0, 0, InvalidTransactionId, NULL};
+
+static inline void subxact_filename(char *path, Oid subid, TransactionId xid);
+static inline void changes_filename(char *path, Oid subid, TransactionId xid);
+
+/*
+ * Information about subtransactions of a given toplevel transaction.
+ */
+static void subxact_info_write(Oid subid, TransactionId xid);
+static void subxact_info_read(Oid subid, TransactionId xid);
+static void subxact_info_add(TransactionId xid);
+static inline void cleanup_subxact_info(void);
+
+/*
+ * Serialize and deserialize changes for a toplevel transaction.
+ */
+static void stream_cleanup_files(Oid subid, TransactionId xid);
+static void stream_open_file(Oid subid, TransactionId xid, bool first);
+static void stream_write_change(char action, StringInfo s);
+static void stream_close_file(void);
+
+static void send_feedback(XLogRecPtr recvpos, bool force, bool requestReply);
+
+static void store_flush_position(XLogRecPtr remote_lsn);
+
+static void maybe_reread_subscription(void);
+
+/* prototype needed because of stream_commit */
+static void apply_dispatch(StringInfo s);
+
+static void apply_handle_commit_internal(LogicalRepCommitData *commit_data);
+static void apply_handle_insert_internal(ApplyExecutionData *edata,
+										 ResultRelInfo *relinfo,
+										 TupleTableSlot *remoteslot);
+static void apply_handle_update_internal(ApplyExecutionData *edata,
+										 ResultRelInfo *relinfo,
+										 TupleTableSlot *remoteslot,
+										 LogicalRepTupleData *newtup);
+static void apply_handle_delete_internal(ApplyExecutionData *edata,
+										 ResultRelInfo *relinfo,
+										 TupleTableSlot *remoteslot);
+static bool FindReplTupleInLocalRel(EState *estate, Relation localrel,
+									LogicalRepRelation *remoterel,
+									TupleTableSlot *remoteslot,
+									TupleTableSlot **localslot);
+static void apply_handle_tuple_routing(ApplyExecutionData *edata,
+									   TupleTableSlot *remoteslot,
+									   LogicalRepTupleData *newtup,
+									   CmdType operation);
+
+/*
+ * Should this worker apply changes for given relation.
+ *
+ * This is mainly needed for initial relation data sync as that runs in
+ * separate worker process running in parallel and we need some way to skip
+ * changes coming to the main apply worker during the sync of a table.
+ *
+ * Note we need to do smaller or equals comparison for SYNCDONE state because
+ * it might hold position of end of initial slot consistent point WAL
+ * record + 1 (ie start of next record) and next record can be COMMIT of
+ * transaction we are now processing (which is what we set remote_final_lsn
+ * to in apply_handle_begin).
+ */
+static bool
+should_apply_changes_for_rel(LogicalRepRelMapEntry *rel)
+{
+	if (am_tablesync_worker())
+		return MyLogicalRepWorker->relid == rel->localreloid;
+	else
+		return (rel->state == SUBREL_STATE_READY ||
+				(rel->state == SUBREL_STATE_SYNCDONE &&
+				 rel->statelsn <= remote_final_lsn));
+}
+
+/*
+ * Begin one step (one INSERT, UPDATE, etc) of a replication transaction.
+ *
+ * Start a transaction, if this is the first step (else we keep using the
+ * existing transaction).
+ * Also provide a global snapshot and ensure we run in ApplyMessageContext.
+ */
+static void
+begin_replication_step(void)
+{
+	SetCurrentStatementStartTimestamp();
+
+	if (!IsTransactionState())
+	{
+		StartTransactionCommand();
+		maybe_reread_subscription();
+	}
+
+	PushActiveSnapshot(GetTransactionSnapshot());
+
+	MemoryContextSwitchTo(ApplyMessageContext);
+}
+
+/*
+ * Finish up one step of a replication transaction.
+ * Callers of begin_replication_step() must also call this.
+ *
+ * We don't close out the transaction here, but we should increment
+ * the command counter to make the effects of this step visible.
+ */
+static void
+end_replication_step(void)
+{
+	PopActiveSnapshot();
+
+	CommandCounterIncrement();
+}
+
+/*
+ * Handle streamed transactions.
+ *
+ * If in streaming mode (receiving a block of streamed transaction), we
+ * simply redirect it to a file for the proper toplevel transaction.
+ *
+ * Returns true for streamed transactions, false otherwise (regular mode).
+ */
+static bool
+handle_streamed_transaction(LogicalRepMsgType action, StringInfo s)
+{
+	TransactionId xid;
+
+	/* not in streaming mode */
+	if (!in_streamed_transaction)
+		return false;
+
+	Assert(stream_fd != NULL);
+	Assert(TransactionIdIsValid(stream_xid));
+
+	/*
+	 * We should have received XID of the subxact as the first part of the
+	 * message, so extract it.
+	 */
+	xid = pq_getmsgint(s, 4);
+
+	if (!TransactionIdIsValid(xid))
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg_internal("invalid transaction ID in streamed replication transaction")));
+
+	/* Add the new subxact to the array (unless already there). */
+	subxact_info_add(xid);
+
+	/* write the change to the current file */
+	stream_write_change(action, s);
+
+	return true;
+}
+
+/*
+ * Executor state preparation for evaluation of constraint expressions,
+ * indexes and triggers for the specified relation.
+ *
+ * Note that the caller must open and close any indexes to be updated.
+ */
+static ApplyExecutionData *
+create_edata_for_relation(LogicalRepRelMapEntry *rel)
+{
+	ApplyExecutionData *edata;
+	EState	   *estate;
+	RangeTblEntry *rte;
+	ResultRelInfo *resultRelInfo;
+
+	edata = (ApplyExecutionData *) palloc0(sizeof(ApplyExecutionData));
+	edata->targetRel = rel;
+
+	edata->estate = estate = CreateExecutorState();
+
+	rte = makeNode(RangeTblEntry);
+	rte->rtekind = RTE_RELATION;
+	rte->relid = RelationGetRelid(rel->localrel);
+	rte->relkind = rel->localrel->rd_rel->relkind;
+	rte->rellockmode = AccessShareLock;
+	ExecInitRangeTable(estate, list_make1(rte));
+
+	edata->targetRelInfo = resultRelInfo = makeNode(ResultRelInfo);
+
+	/*
+	 * Use Relation opened by logicalrep_rel_open() instead of opening it
+	 * again.
+	 */
+	InitResultRelInfo(resultRelInfo, rel->localrel, 1, NULL, 0);
+
+	/*
+	 * We put the ResultRelInfo in the es_opened_result_relations list, even
+	 * though we don't populate the es_result_relations array.  That's a bit
+	 * bogus, but it's enough to make ExecGetTriggerResultRel() find them.
+	 *
+	 * ExecOpenIndices() is not called here either, each execution path doing
+	 * an apply operation being responsible for that.
+	 */
+	estate->es_opened_result_relations =
+		lappend(estate->es_opened_result_relations, resultRelInfo);
+
+	estate->es_output_cid = GetCurrentCommandId(true);
+
+	/* Prepare to catch AFTER triggers. */
+	AfterTriggerBeginQuery();
+
+	/* other fields of edata remain NULL for now */
+
+	return edata;
+}
+
+/*
+ * Finish any operations related to the executor state created by
+ * create_edata_for_relation().
+ */
+static void
+finish_edata(ApplyExecutionData *edata)
+{
+	EState	   *estate = edata->estate;
+
+	/* Handle any queued AFTER triggers. */
+	AfterTriggerEndQuery(estate);
+
+	/* Shut down tuple routing, if any was done. */
+	if (edata->proute)
+		ExecCleanupTupleRouting(edata->mtstate, edata->proute);
+
+	/*
+	 * Cleanup.  It might seem that we should call ExecCloseResultRelations()
+	 * here, but we intentionally don't.  It would close the rel we added to
+	 * es_opened_result_relations above, which is wrong because we took no
+	 * corresponding refcount.  We rely on ExecCleanupTupleRouting() to close
+	 * any other relations opened during execution.
+	 */
+	ExecResetTupleTable(estate->es_tupleTable, false);
+	FreeExecutorState(estate);
+	pfree(edata);
+}
+
+/*
+ * Executes default values for columns for which we can't map to remote
+ * relation columns.
+ *
+ * This allows us to support tables which have more columns on the downstream
+ * than on the upstream.
+ */
+static void
+slot_fill_defaults(LogicalRepRelMapEntry *rel, EState *estate,
+				   TupleTableSlot *slot)
+{
+	TupleDesc	desc = RelationGetDescr(rel->localrel);
+	int			num_phys_attrs = desc->natts;
+	int			i;
+	int			attnum,
+				num_defaults = 0;
+	int		   *defmap;
+	ExprState **defexprs;
+	ExprContext *econtext;
+
+	econtext = GetPerTupleExprContext(estate);
+
+	/* We got all the data via replication, no need to evaluate anything. */
+	if (num_phys_attrs == rel->remoterel.natts)
+		return;
+
+	defmap = (int *) palloc(num_phys_attrs * sizeof(int));
+	defexprs = (ExprState **) palloc(num_phys_attrs * sizeof(ExprState *));
+
+	Assert(rel->attrmap->maplen == num_phys_attrs);
+	for (attnum = 0; attnum < num_phys_attrs; attnum++)
+	{
+		Expr	   *defexpr;
+
+		if (TupleDescAttr(desc, attnum)->attisdropped || TupleDescAttr(desc, attnum)->attgenerated)
+			continue;
+
+		if (rel->attrmap->attnums[attnum] >= 0)
+			continue;
+
+		defexpr = (Expr *) build_column_default(rel->localrel, attnum + 1);
+
+		if (defexpr != NULL)
+		{
+			/* Run the expression through planner */
+			defexpr = expression_planner(defexpr);
+
+			/* Initialize executable expression in copycontext */
+			defexprs[num_defaults] = ExecInitExpr(defexpr, NULL);
+			defmap[num_defaults] = attnum;
+			num_defaults++;
+		}
+
+	}
+
+	for (i = 0; i < num_defaults; i++)
+		slot->tts_values[defmap[i]] =
+			ExecEvalExpr(defexprs[i], econtext, &slot->tts_isnull[defmap[i]]);
+}
+
+/*
+ * Error callback to give more context info about data conversion failures
+ * while reading data from the remote server.
+ */
+static void
+slot_store_error_callback(void *arg)
+{
+	SlotErrCallbackArg *errarg = (SlotErrCallbackArg *) arg;
+	LogicalRepRelMapEntry *rel;
+
+	/* Nothing to do if remote attribute number is not set */
+	if (errarg->remote_attnum < 0)
+		return;
+
+	rel = errarg->rel;
+	errcontext("processing remote data for replication target relation \"%s.%s\" column \"%s\"",
+			   rel->remoterel.nspname, rel->remoterel.relname,
+			   rel->remoterel.attnames[errarg->remote_attnum]);
+}
+
+/*
+ * Store tuple data into slot.
+ *
+ * Incoming data can be either text or binary format.
+ */
+static void
+slot_store_data(TupleTableSlot *slot, LogicalRepRelMapEntry *rel,
+				LogicalRepTupleData *tupleData)
+{
+	int			natts = slot->tts_tupleDescriptor->natts;
+	int			i;
+	SlotErrCallbackArg errarg;
+	ErrorContextCallback errcallback;
+
+	ExecClearTuple(slot);
+
+	/* Push callback + info on the error context stack */
+	errarg.rel = rel;
+	errarg.remote_attnum = -1;
+	errcallback.callback = slot_store_error_callback;
+	errcallback.arg = (void *) &errarg;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* Call the "in" function for each non-dropped, non-null attribute */
+	Assert(natts == rel->attrmap->maplen);
+	for (i = 0; i < natts; i++)
+	{
+		Form_pg_attribute att = TupleDescAttr(slot->tts_tupleDescriptor, i);
+		int			remoteattnum = rel->attrmap->attnums[i];
+
+		if (!att->attisdropped && remoteattnum >= 0)
+		{
+			StringInfo	colvalue = &tupleData->colvalues[remoteattnum];
+
+			Assert(remoteattnum < tupleData->ncols);
+
+			errarg.remote_attnum = remoteattnum;
+
+			if (tupleData->colstatus[remoteattnum] == LOGICALREP_COLUMN_TEXT)
+			{
+				Oid			typinput;
+				Oid			typioparam;
+
+				getTypeInputInfo(att->atttypid, &typinput, &typioparam);
+				slot->tts_values[i] =
+					OidInputFunctionCall(typinput, colvalue->data,
+										 typioparam, att->atttypmod);
+				slot->tts_isnull[i] = false;
+			}
+			else if (tupleData->colstatus[remoteattnum] == LOGICALREP_COLUMN_BINARY)
+			{
+				Oid			typreceive;
+				Oid			typioparam;
+
+				/*
+				 * In some code paths we may be asked to re-parse the same
+				 * tuple data.  Reset the StringInfo's cursor so that works.
+				 */
+				colvalue->cursor = 0;
+
+				getTypeBinaryInputInfo(att->atttypid, &typreceive, &typioparam);
+				slot->tts_values[i] =
+					OidReceiveFunctionCall(typreceive, colvalue,
+										   typioparam, att->atttypmod);
+
+				/* Trouble if it didn't eat the whole buffer */
+				if (colvalue->cursor != colvalue->len)
+					ereport(ERROR,
+							(errcode(ERRCODE_INVALID_BINARY_REPRESENTATION),
+							 errmsg("incorrect binary data format in logical replication column %d",
+									remoteattnum + 1)));
+				slot->tts_isnull[i] = false;
+			}
+			else
+			{
+				/*
+				 * NULL value from remote.  (We don't expect to see
+				 * LOGICALREP_COLUMN_UNCHANGED here, but if we do, treat it as
+				 * NULL.)
+				 */
+				slot->tts_values[i] = (Datum) 0;
+				slot->tts_isnull[i] = true;
+			}
+
+			errarg.remote_attnum = -1;
+		}
+		else
+		{
+			/*
+			 * We assign NULL to dropped attributes and missing values
+			 * (missing values should be later filled using
+			 * slot_fill_defaults).
+			 */
+			slot->tts_values[i] = (Datum) 0;
+			slot->tts_isnull[i] = true;
+		}
+	}
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+
+	ExecStoreVirtualTuple(slot);
+}
+
+/*
+ * Replace updated columns with data from the LogicalRepTupleData struct.
+ * This is somewhat similar to heap_modify_tuple but also calls the type
+ * input functions on the user data.
+ *
+ * "slot" is filled with a copy of the tuple in "srcslot", replacing
+ * columns provided in "tupleData" and leaving others as-is.
+ *
+ * Caution: unreplaced pass-by-ref columns in "slot" will point into the
+ * storage for "srcslot".  This is OK for current usage, but someday we may
+ * need to materialize "slot" at the end to make it independent of "srcslot".
+ */
+static void
+slot_modify_data(TupleTableSlot *slot, TupleTableSlot *srcslot,
+				 LogicalRepRelMapEntry *rel,
+				 LogicalRepTupleData *tupleData)
+{
+	int			natts = slot->tts_tupleDescriptor->natts;
+	int			i;
+	SlotErrCallbackArg errarg;
+	ErrorContextCallback errcallback;
+
+	/* We'll fill "slot" with a virtual tuple, so we must start with ... */
+	ExecClearTuple(slot);
+
+	/*
+	 * Copy all the column data from srcslot, so that we'll have valid values
+	 * for unreplaced columns.
+	 */
+	Assert(natts == srcslot->tts_tupleDescriptor->natts);
+	slot_getallattrs(srcslot);
+	memcpy(slot->tts_values, srcslot->tts_values, natts * sizeof(Datum));
+	memcpy(slot->tts_isnull, srcslot->tts_isnull, natts * sizeof(bool));
+
+	/* For error reporting, push callback + info on the error context stack */
+	errarg.rel = rel;
+	errarg.remote_attnum = -1;
+	errcallback.callback = slot_store_error_callback;
+	errcallback.arg = (void *) &errarg;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* Call the "in" function for each replaced attribute */
+	Assert(natts == rel->attrmap->maplen);
+	for (i = 0; i < natts; i++)
+	{
+		Form_pg_attribute att = TupleDescAttr(slot->tts_tupleDescriptor, i);
+		int			remoteattnum = rel->attrmap->attnums[i];
+
+		if (remoteattnum < 0)
+			continue;
+
+		Assert(remoteattnum < tupleData->ncols);
+
+		if (tupleData->colstatus[remoteattnum] != LOGICALREP_COLUMN_UNCHANGED)
+		{
+			StringInfo	colvalue = &tupleData->colvalues[remoteattnum];
+
+			errarg.remote_attnum = remoteattnum;
+
+			if (tupleData->colstatus[remoteattnum] == LOGICALREP_COLUMN_TEXT)
+			{
+				Oid			typinput;
+				Oid			typioparam;
+
+				getTypeInputInfo(att->atttypid, &typinput, &typioparam);
+				slot->tts_values[i] =
+					OidInputFunctionCall(typinput, colvalue->data,
+										 typioparam, att->atttypmod);
+				slot->tts_isnull[i] = false;
+			}
+			else if (tupleData->colstatus[remoteattnum] == LOGICALREP_COLUMN_BINARY)
+			{
+				Oid			typreceive;
+				Oid			typioparam;
+
+				/*
+				 * In some code paths we may be asked to re-parse the same
+				 * tuple data.  Reset the StringInfo's cursor so that works.
+				 */
+				colvalue->cursor = 0;
+
+				getTypeBinaryInputInfo(att->atttypid, &typreceive, &typioparam);
+				slot->tts_values[i] =
+					OidReceiveFunctionCall(typreceive, colvalue,
+										   typioparam, att->atttypmod);
+
+				/* Trouble if it didn't eat the whole buffer */
+				if (colvalue->cursor != colvalue->len)
+					ereport(ERROR,
+							(errcode(ERRCODE_INVALID_BINARY_REPRESENTATION),
+							 errmsg("incorrect binary data format in logical replication column %d",
+									remoteattnum + 1)));
+				slot->tts_isnull[i] = false;
+			}
+			else
+			{
+				/* must be LOGICALREP_COLUMN_NULL */
+				slot->tts_values[i] = (Datum) 0;
+				slot->tts_isnull[i] = true;
+			}
+
+			errarg.remote_attnum = -1;
+		}
+	}
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+
+	/* And finally, declare that "slot" contains a valid virtual tuple */
+	ExecStoreVirtualTuple(slot);
+}
+
+/*
+ * Handle BEGIN message.
+ */
+static void
+apply_handle_begin(StringInfo s)
+{
+	LogicalRepBeginData begin_data;
+
+	logicalrep_read_begin(s, &begin_data);
+
+	remote_final_lsn = begin_data.final_lsn;
+
+	in_remote_transaction = true;
+
+	pgstat_report_activity(STATE_RUNNING, NULL);
+}
+
+/*
+ * Handle COMMIT message.
+ *
+ * TODO, support tracking of multiple origins
+ */
+static void
+apply_handle_commit(StringInfo s)
+{
+	LogicalRepCommitData commit_data;
+
+	logicalrep_read_commit(s, &commit_data);
+
+	if (commit_data.commit_lsn != remote_final_lsn)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg_internal("incorrect commit LSN %X/%X in commit message (expected %X/%X)",
+								 LSN_FORMAT_ARGS(commit_data.commit_lsn),
+								 LSN_FORMAT_ARGS(remote_final_lsn))));
+
+	apply_handle_commit_internal(&commit_data);
+
+	/* Process any tables that are being synchronized in parallel. */
+	process_syncing_tables(commit_data.end_lsn);
+
+	pgstat_report_activity(STATE_IDLE, NULL);
+}
+
+/*
+ * Handle ORIGIN message.
+ *
+ * TODO, support tracking of multiple origins
+ */
+static void
+apply_handle_origin(StringInfo s)
+{
+	/*
+	 * ORIGIN message can only come inside streaming transaction or inside
+	 * remote transaction and before any actual writes.
+	 */
+	if (!in_streamed_transaction &&
+		(!in_remote_transaction ||
+		 (IsTransactionState() && !am_tablesync_worker())))
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg_internal("ORIGIN message sent out of order")));
+}
+
+/*
+ * Handle STREAM START message.
+ */
+static void
+apply_handle_stream_start(StringInfo s)
+{
+	bool		first_segment;
+	HASHCTL		hash_ctl;
+
+	if (in_streamed_transaction)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg_internal("duplicate STREAM START message")));
+
+	/*
+	 * Start a transaction on stream start, this transaction will be committed
+	 * on the stream stop unless it is a tablesync worker in which case it
+	 * will be committed after processing all the messages. We need the
+	 * transaction for handling the buffile, used for serializing the
+	 * streaming data and subxact info.
+	 */
+	begin_replication_step();
+
+	/* notify handle methods we're processing a remote transaction */
+	in_streamed_transaction = true;
+
+	/* extract XID of the top-level transaction */
+	stream_xid = logicalrep_read_stream_start(s, &first_segment);
+
+	if (!TransactionIdIsValid(stream_xid))
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg_internal("invalid transaction ID in streamed replication transaction")));
+
+	/*
+	 * Initialize the xidhash table if we haven't yet. This will be used for
+	 * the entire duration of the apply worker so create it in permanent
+	 * context.
+	 */
+	if (xidhash == NULL)
+	{
+		hash_ctl.keysize = sizeof(TransactionId);
+		hash_ctl.entrysize = sizeof(StreamXidHash);
+		hash_ctl.hcxt = ApplyContext;
+		xidhash = hash_create("StreamXidHash", 1024, &hash_ctl,
+							  HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
+	}
+
+	/* open the spool file for this transaction */
+	stream_open_file(MyLogicalRepWorker->subid, stream_xid, first_segment);
+
+	/* if this is not the first segment, open existing subxact file */
+	if (!first_segment)
+		subxact_info_read(MyLogicalRepWorker->subid, stream_xid);
+
+	pgstat_report_activity(STATE_RUNNING, NULL);
+
+	end_replication_step();
+}
+
+/*
+ * Handle STREAM STOP message.
+ */
+static void
+apply_handle_stream_stop(StringInfo s)
+{
+	if (!in_streamed_transaction)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg_internal("STREAM STOP message without STREAM START")));
+
+	/*
+	 * Close the file with serialized changes, and serialize information about
+	 * subxacts for the toplevel transaction.
+	 */
+	subxact_info_write(MyLogicalRepWorker->subid, stream_xid);
+	stream_close_file();
+
+	/* We must be in a valid transaction state */
+	Assert(IsTransactionState());
+
+	/* Commit the per-stream transaction */
+	CommitTransactionCommand();
+
+	in_streamed_transaction = false;
+
+	/* Reset per-stream context */
+	MemoryContextReset(LogicalStreamingContext);
+
+	pgstat_report_activity(STATE_IDLE, NULL);
+}
+
+/*
+ * Handle STREAM abort message.
+ */
+static void
+apply_handle_stream_abort(StringInfo s)
+{
+	TransactionId xid;
+	TransactionId subxid;
+
+	if (in_streamed_transaction)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg_internal("STREAM ABORT message without STREAM STOP")));
+
+	logicalrep_read_stream_abort(s, &xid, &subxid);
+
+	/*
+	 * If the two XIDs are the same, it's in fact abort of toplevel xact, so
+	 * just delete the files with serialized info.
+	 */
+	if (xid == subxid)
+		stream_cleanup_files(MyLogicalRepWorker->subid, xid);
+	else
+	{
+		/*
+		 * OK, so it's a subxact. We need to read the subxact file for the
+		 * toplevel transaction, determine the offset tracked for the subxact,
+		 * and truncate the file with changes. We also remove the subxacts
+		 * with higher offsets (or rather higher XIDs).
+		 *
+		 * We intentionally scan the array from the tail, because we're likely
+		 * aborting a change for the most recent subtransactions.
+		 *
+		 * We can't use the binary search here as subxact XIDs won't
+		 * necessarily arrive in sorted order, consider the case where we have
+		 * released the savepoint for multiple subtransactions and then
+		 * performed rollback to savepoint for one of the earlier
+		 * sub-transaction.
+		 */
+		int64		i;
+		int64		subidx;
+		BufFile    *fd;
+		bool		found = false;
+		char		path[MAXPGPATH];
+		StreamXidHash *ent;
+
+		subidx = -1;
+		begin_replication_step();
+		subxact_info_read(MyLogicalRepWorker->subid, xid);
+
+		for (i = subxact_data.nsubxacts; i > 0; i--)
+		{
+			if (subxact_data.subxacts[i - 1].xid == subxid)
+			{
+				subidx = (i - 1);
+				found = true;
+				break;
+			}
+		}
+
+		/*
+		 * If it's an empty sub-transaction then we will not find the subxid
+		 * here so just cleanup the subxact info and return.
+		 */
+		if (!found)
+		{
+			/* Cleanup the subxact info */
+			cleanup_subxact_info();
+			end_replication_step();
+			CommitTransactionCommand();
+			return;
+		}
+
+		ent = (StreamXidHash *) hash_search(xidhash,
+											(void *) &xid,
+											HASH_FIND,
+											NULL);
+		if (!ent)
+			ereport(ERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg_internal("transaction %u not found in stream XID hash table",
+									 xid)));
+
+		/* open the changes file */
+		changes_filename(path, MyLogicalRepWorker->subid, xid);
+		fd = BufFileOpenShared(ent->stream_fileset, path, O_RDWR);
+
+		/* OK, truncate the file at the right offset */
+		BufFileTruncateShared(fd, subxact_data.subxacts[subidx].fileno,
+							  subxact_data.subxacts[subidx].offset);
+		BufFileClose(fd);
+
+		/* discard the subxacts added later */
+		subxact_data.nsubxacts = subidx;
+
+		/* write the updated subxact list */
+		subxact_info_write(MyLogicalRepWorker->subid, xid);
+
+		end_replication_step();
+		CommitTransactionCommand();
+	}
+}
+
+/*
+ * Handle STREAM COMMIT message.
+ */
+static void
+apply_handle_stream_commit(StringInfo s)
+{
+	TransactionId xid;
+	StringInfoData s2;
+	int			nchanges;
+	char		path[MAXPGPATH];
+	char	   *buffer = NULL;
+	LogicalRepCommitData commit_data;
+	StreamXidHash *ent;
+	MemoryContext oldcxt;
+	BufFile    *fd;
+
+	if (in_streamed_transaction)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg_internal("STREAM COMMIT message without STREAM STOP")));
+
+	xid = logicalrep_read_stream_commit(s, &commit_data);
+
+	elog(DEBUG1, "received commit for streamed transaction %u", xid);
+
+	/* Make sure we have an open transaction */
+	begin_replication_step();
+
+	/*
+	 * Allocate file handle and memory required to process all the messages in
+	 * TopTransactionContext to avoid them getting reset after each message is
+	 * processed.
+	 */
+	oldcxt = MemoryContextSwitchTo(TopTransactionContext);
+
+	/* open the spool file for the committed transaction */
+	changes_filename(path, MyLogicalRepWorker->subid, xid);
+	elog(DEBUG1, "replaying changes from file \"%s\"", path);
+
+	ent = (StreamXidHash *) hash_search(xidhash,
+										(void *) &xid,
+										HASH_FIND,
+										NULL);
+	if (!ent)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg_internal("transaction %u not found in stream XID hash table",
+								 xid)));
+
+	fd = BufFileOpenShared(ent->stream_fileset, path, O_RDONLY);
+
+	buffer = palloc(BLCKSZ);
+	initStringInfo(&s2);
+
+	MemoryContextSwitchTo(oldcxt);
+
+	remote_final_lsn = commit_data.commit_lsn;
+
+	/*
+	 * Make sure the handle apply_dispatch methods are aware we're in a remote
+	 * transaction.
+	 */
+	in_remote_transaction = true;
+	pgstat_report_activity(STATE_RUNNING, NULL);
+
+	end_replication_step();
+
+	/*
+	 * Read the entries one by one and pass them through the same logic as in
+	 * apply_dispatch.
+	 */
+	nchanges = 0;
+	while (true)
+	{
+		int			nbytes;
+		int			len;
+
+		CHECK_FOR_INTERRUPTS();
+
+		/* read length of the on-disk record */
+		nbytes = BufFileRead(fd, &len, sizeof(len));
+
+		/* have we reached end of the file? */
+		if (nbytes == 0)
+			break;
+
+		/* do we have a correct length? */
+		if (nbytes != sizeof(len))
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not read from streaming transaction's changes file \"%s\": %m",
+							path)));
+
+		if (len <= 0)
+			elog(ERROR, "incorrect length %d in streaming transaction's changes file \"%s\"",
+				 len, path);
+
+		/* make sure we have sufficiently large buffer */
+		buffer = repalloc(buffer, len);
+
+		/* and finally read the data into the buffer */
+		if (BufFileRead(fd, buffer, len) != len)
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not read from streaming transaction's changes file \"%s\": %m",
+							path)));
+
+		/* copy the buffer to the stringinfo and call apply_dispatch */
+		resetStringInfo(&s2);
+		appendBinaryStringInfo(&s2, buffer, len);
+
+		/* Ensure we are reading the data into our memory context. */
+		oldcxt = MemoryContextSwitchTo(ApplyMessageContext);
+
+		apply_dispatch(&s2);
+
+		MemoryContextReset(ApplyMessageContext);
+
+		MemoryContextSwitchTo(oldcxt);
+
+		nchanges++;
+
+		if (nchanges % 1000 == 0)
+			elog(DEBUG1, "replayed %d changes from file \"%s\"",
+				 nchanges, path);
+	}
+
+	BufFileClose(fd);
+
+	pfree(buffer);
+	pfree(s2.data);
+
+	elog(DEBUG1, "replayed %d (all) changes from file \"%s\"",
+		 nchanges, path);
+
+	apply_handle_commit_internal(&commit_data);
+
+	/* unlink the files with serialized changes and subxact info */
+	stream_cleanup_files(MyLogicalRepWorker->subid, xid);
+
+	/* Process any tables that are being synchronized in parallel. */
+	process_syncing_tables(commit_data.end_lsn);
+
+	pgstat_report_activity(STATE_IDLE, NULL);
+}
+
+/*
+ * Helper function for apply_handle_commit and apply_handle_stream_commit.
+ */
+static void
+apply_handle_commit_internal(LogicalRepCommitData *commit_data)
+{
+	if (IsTransactionState())
+	{
+		/*
+		 * Update origin state so we can restart streaming from correct
+		 * position in case of crash.
+		 */
+		replorigin_session_origin_lsn = commit_data->end_lsn;
+		replorigin_session_origin_timestamp = commit_data->committime;
+
+		CommitTransactionCommand();
+		pgstat_report_stat(false);
+
+		store_flush_position(commit_data->end_lsn);
+	}
+	else
+	{
+		/* Process any invalidation messages that might have accumulated. */
+		AcceptInvalidationMessages();
+		maybe_reread_subscription();
+	}
+
+	in_remote_transaction = false;
+}
+
+/*
+ * Handle RELATION message.
+ *
+ * Note we don't do validation against local schema here. The validation
+ * against local schema is postponed until first change for given relation
+ * comes as we only care about it when applying changes for it anyway and we
+ * do less locking this way.
+ */
+static void
+apply_handle_relation(StringInfo s)
+{
+	LogicalRepRelation *rel;
+
+	if (handle_streamed_transaction(LOGICAL_REP_MSG_RELATION, s))
+		return;
+
+	rel = logicalrep_read_rel(s);
+	logicalrep_relmap_update(rel);
+
+	/* Also reset all entries in the partition map that refer to remoterel. */
+	logicalrep_partmap_reset_relmap(rel);
+}
+
+/*
+ * Handle TYPE message.
+ *
+ * This implementation pays no attention to TYPE messages; we expect the user
+ * to have set things up so that the incoming data is acceptable to the input
+ * functions for the locally subscribed tables.  Hence, we just read and
+ * discard the message.
+ */
+static void
+apply_handle_type(StringInfo s)
+{
+	LogicalRepTyp typ;
+
+	if (handle_streamed_transaction(LOGICAL_REP_MSG_TYPE, s))
+		return;
+
+	logicalrep_read_typ(s, &typ);
+}
+
+/*
+ * Get replica identity index or if it is not defined a primary key.
+ *
+ * If neither is defined, returns InvalidOid
+ */
+static Oid
+GetRelationIdentityOrPK(Relation rel)
+{
+	Oid			idxoid;
+
+	idxoid = RelationGetReplicaIndex(rel);
+
+	if (!OidIsValid(idxoid))
+		idxoid = RelationGetPrimaryKeyIndex(rel);
+
+	return idxoid;
+}
+
+/*
+ * Handle INSERT message.
+ */
+
+static void
+apply_handle_insert(StringInfo s)
+{
+	LogicalRepRelMapEntry *rel;
+	LogicalRepTupleData newtup;
+	LogicalRepRelId relid;
+	ApplyExecutionData *edata;
+	EState	   *estate;
+	TupleTableSlot *remoteslot;
+	MemoryContext oldctx;
+
+	if (handle_streamed_transaction(LOGICAL_REP_MSG_INSERT, s))
+		return;
+
+	begin_replication_step();
+
+	relid = logicalrep_read_insert(s, &newtup);
+	rel = logicalrep_rel_open(relid, RowExclusiveLock);
+	if (!should_apply_changes_for_rel(rel))
+	{
+		/*
+		 * The relation can't become interesting in the middle of the
+		 * transaction so it's safe to unlock it.
+		 */
+		logicalrep_rel_close(rel, RowExclusiveLock);
+		end_replication_step();
+		return;
+	}
+
+	/* Initialize the executor state. */
+	edata = create_edata_for_relation(rel);
+	estate = edata->estate;
+	remoteslot = ExecInitExtraTupleSlot(estate,
+										RelationGetDescr(rel->localrel),
+										&TTSOpsVirtual);
+
+	/* Process and store remote tuple in the slot */
+	oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
+	slot_store_data(remoteslot, rel, &newtup);
+	slot_fill_defaults(rel, estate, remoteslot);
+	MemoryContextSwitchTo(oldctx);
+
+	/* For a partitioned table, insert the tuple into a partition. */
+	if (rel->localrel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
+		apply_handle_tuple_routing(edata,
+								   remoteslot, NULL, CMD_INSERT);
+	else
+		apply_handle_insert_internal(edata, edata->targetRelInfo,
+									 remoteslot);
+
+	finish_edata(edata);
+
+	logicalrep_rel_close(rel, NoLock);
+
+	end_replication_step();
+}
+
+/*
+ * Workhorse for apply_handle_insert()
+ * relinfo is for the relation we're actually inserting into
+ * (could be a child partition of edata->targetRelInfo)
+ */
+static void
+apply_handle_insert_internal(ApplyExecutionData *edata,
+							 ResultRelInfo *relinfo,
+							 TupleTableSlot *remoteslot)
+{
+	EState	   *estate = edata->estate;
+
+	/* We must open indexes here. */
+	ExecOpenIndices(relinfo, false);
+
+	/* Do the insert. */
+	ExecSimpleRelationInsert(relinfo, estate, remoteslot);
+
+	/* Cleanup. */
+	ExecCloseIndices(relinfo);
+}
+
+/*
+ * Check if the logical replication relation is updatable and throw
+ * appropriate error if it isn't.
+ */
+static void
+check_relation_updatable(LogicalRepRelMapEntry *rel)
+{
+	/*
+	 * For partitioned tables, we only need to care if the target partition is
+	 * updatable (aka has PK or RI defined for it).
+	 */
+	if (rel->localrel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
+		return;
+
+	/* Updatable, no error. */
+	if (rel->updatable)
+		return;
+
+	/*
+	 * We are in error mode so it's fine this is somewhat slow. It's better to
+	 * give user correct error.
+	 */
+	if (OidIsValid(GetRelationIdentityOrPK(rel->localrel)))
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("publisher did not send replica identity column "
+						"expected by the logical replication target relation \"%s.%s\"",
+						rel->remoterel.nspname, rel->remoterel.relname)));
+	}
+
+	ereport(ERROR,
+			(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+			 errmsg("logical replication target relation \"%s.%s\" has "
+					"neither REPLICA IDENTITY index nor PRIMARY "
+					"KEY and published relation does not have "
+					"REPLICA IDENTITY FULL",
+					rel->remoterel.nspname, rel->remoterel.relname)));
+}
+
+/*
+ * Handle UPDATE message.
+ *
+ * TODO: FDW support
+ */
+static void
+apply_handle_update(StringInfo s)
+{
+	LogicalRepRelMapEntry *rel;
+	LogicalRepRelId relid;
+	ApplyExecutionData *edata;
+	EState	   *estate;
+	LogicalRepTupleData oldtup;
+	LogicalRepTupleData newtup;
+	bool		has_oldtup;
+	TupleTableSlot *remoteslot;
+	RangeTblEntry *target_rte;
+	MemoryContext oldctx;
+
+	if (handle_streamed_transaction(LOGICAL_REP_MSG_UPDATE, s))
+		return;
+
+	begin_replication_step();
+
+	relid = logicalrep_read_update(s, &has_oldtup, &oldtup,
+								   &newtup);
+	rel = logicalrep_rel_open(relid, RowExclusiveLock);
+	if (!should_apply_changes_for_rel(rel))
+	{
+		/*
+		 * The relation can't become interesting in the middle of the
+		 * transaction so it's safe to unlock it.
+		 */
+		logicalrep_rel_close(rel, RowExclusiveLock);
+		end_replication_step();
+		return;
+	}
+
+	/* Check if we can do the update. */
+	check_relation_updatable(rel);
+
+	/* Initialize the executor state. */
+	edata = create_edata_for_relation(rel);
+	estate = edata->estate;
+	remoteslot = ExecInitExtraTupleSlot(estate,
+										RelationGetDescr(rel->localrel),
+										&TTSOpsVirtual);
+
+	/*
+	 * Populate updatedCols so that per-column triggers can fire, and so
+	 * executor can correctly pass down indexUnchanged hint.  This could
+	 * include more columns than were actually changed on the publisher
+	 * because the logical replication protocol doesn't contain that
+	 * information.  But it would for example exclude columns that only exist
+	 * on the subscriber, since we are not touching those.
+	 */
+	target_rte = list_nth(estate->es_range_table, 0);
+	for (int i = 0; i < remoteslot->tts_tupleDescriptor->natts; i++)
+	{
+		Form_pg_attribute att = TupleDescAttr(remoteslot->tts_tupleDescriptor, i);
+		int			remoteattnum = rel->attrmap->attnums[i];
+
+		if (!att->attisdropped && remoteattnum >= 0)
+		{
+			Assert(remoteattnum < newtup.ncols);
+			if (newtup.colstatus[remoteattnum] != LOGICALREP_COLUMN_UNCHANGED)
+				target_rte->updatedCols =
+					bms_add_member(target_rte->updatedCols,
+								   i + 1 - FirstLowInvalidHeapAttributeNumber);
+		}
+	}
+
+	/* Also populate extraUpdatedCols, in case we have generated columns */
+	fill_extraUpdatedCols(target_rte, rel->localrel);
+
+	/* Build the search tuple. */
+	oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
+	slot_store_data(remoteslot, rel,
+					has_oldtup ? &oldtup : &newtup);
+	MemoryContextSwitchTo(oldctx);
+
+	/* For a partitioned table, apply update to correct partition. */
+	if (rel->localrel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
+		apply_handle_tuple_routing(edata,
+								   remoteslot, &newtup, CMD_UPDATE);
+	else
+		apply_handle_update_internal(edata, edata->targetRelInfo,
+									 remoteslot, &newtup);
+
+	finish_edata(edata);
+
+	logicalrep_rel_close(rel, NoLock);
+
+	end_replication_step();
+}
+
+/*
+ * Workhorse for apply_handle_update()
+ * relinfo is for the relation we're actually updating in
+ * (could be a child partition of edata->targetRelInfo)
+ */
+static void
+apply_handle_update_internal(ApplyExecutionData *edata,
+							 ResultRelInfo *relinfo,
+							 TupleTableSlot *remoteslot,
+							 LogicalRepTupleData *newtup)
+{
+	EState	   *estate = edata->estate;
+	LogicalRepRelMapEntry *relmapentry = edata->targetRel;
+	Relation	localrel = relinfo->ri_RelationDesc;
+	EPQState	epqstate;
+	TupleTableSlot *localslot;
+	bool		found;
+	MemoryContext oldctx;
+
+	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1);
+	ExecOpenIndices(relinfo, false);
+
+	found = FindReplTupleInLocalRel(estate, localrel,
+									&relmapentry->remoterel,
+									remoteslot, &localslot);
+	ExecClearTuple(remoteslot);
+
+	/*
+	 * Tuple found.
+	 *
+	 * Note this will fail if there are other conflicting unique indexes.
+	 */
+	if (found)
+	{
+		/* Process and store remote tuple in the slot */
+		oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
+		slot_modify_data(remoteslot, localslot, relmapentry, newtup);
+		MemoryContextSwitchTo(oldctx);
+
+		EvalPlanQualSetSlot(&epqstate, remoteslot);
+
+		/* Do the actual update. */
+		ExecSimpleRelationUpdate(relinfo, estate, &epqstate, localslot,
+								 remoteslot);
+	}
+	else
+	{
+		/*
+		 * The tuple to be updated could not be found.  Do nothing except for
+		 * emitting a log message.
+		 *
+		 * XXX should this be promoted to ereport(LOG) perhaps?
+		 */
+		elog(DEBUG1,
+			 "logical replication did not find row to be updated "
+			 "in replication target relation \"%s\"",
+			 RelationGetRelationName(localrel));
+	}
+
+	/* Cleanup. */
+	ExecCloseIndices(relinfo);
+	EvalPlanQualEnd(&epqstate);
+}
+
+/*
+ * Handle DELETE message.
+ *
+ * TODO: FDW support
+ */
+static void
+apply_handle_delete(StringInfo s)
+{
+	LogicalRepRelMapEntry *rel;
+	LogicalRepTupleData oldtup;
+	LogicalRepRelId relid;
+	ApplyExecutionData *edata;
+	EState	   *estate;
+	TupleTableSlot *remoteslot;
+	MemoryContext oldctx;
+
+	if (handle_streamed_transaction(LOGICAL_REP_MSG_DELETE, s))
+		return;
+
+	begin_replication_step();
+
+	relid = logicalrep_read_delete(s, &oldtup);
+	rel = logicalrep_rel_open(relid, RowExclusiveLock);
+	if (!should_apply_changes_for_rel(rel))
+	{
+		/*
+		 * The relation can't become interesting in the middle of the
+		 * transaction so it's safe to unlock it.
+		 */
+		logicalrep_rel_close(rel, RowExclusiveLock);
+		end_replication_step();
+		return;
+	}
+
+	/* Check if we can do the delete. */
+	check_relation_updatable(rel);
+
+	/* Initialize the executor state. */
+	edata = create_edata_for_relation(rel);
+	estate = edata->estate;
+	remoteslot = ExecInitExtraTupleSlot(estate,
+										RelationGetDescr(rel->localrel),
+										&TTSOpsVirtual);
+
+	/* Build the search tuple. */
+	oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
+	slot_store_data(remoteslot, rel, &oldtup);
+	MemoryContextSwitchTo(oldctx);
+
+	/* For a partitioned table, apply delete to correct partition. */
+	if (rel->localrel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
+		apply_handle_tuple_routing(edata,
+								   remoteslot, NULL, CMD_DELETE);
+	else
+		apply_handle_delete_internal(edata, edata->targetRelInfo,
+									 remoteslot);
+
+	finish_edata(edata);
+
+	logicalrep_rel_close(rel, NoLock);
+
+	end_replication_step();
+}
+
+/*
+ * Workhorse for apply_handle_delete()
+ * relinfo is for the relation we're actually deleting from
+ * (could be a child partition of edata->targetRelInfo)
+ */
+static void
+apply_handle_delete_internal(ApplyExecutionData *edata,
+							 ResultRelInfo *relinfo,
+							 TupleTableSlot *remoteslot)
+{
+	EState	   *estate = edata->estate;
+	Relation	localrel = relinfo->ri_RelationDesc;
+	LogicalRepRelation *remoterel = &edata->targetRel->remoterel;
+	EPQState	epqstate;
+	TupleTableSlot *localslot;
+	bool		found;
+
+	EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1);
+	ExecOpenIndices(relinfo, false);
+
+	found = FindReplTupleInLocalRel(estate, localrel, remoterel,
+									remoteslot, &localslot);
+
+	/* If found delete it. */
+	if (found)
+	{
+		EvalPlanQualSetSlot(&epqstate, localslot);
+
+		/* Do the actual delete. */
+		ExecSimpleRelationDelete(relinfo, estate, &epqstate, localslot);
+	}
+	else
+	{
+		/*
+		 * The tuple to be deleted could not be found.  Do nothing except for
+		 * emitting a log message.
+		 *
+		 * XXX should this be promoted to ereport(LOG) perhaps?
+		 */
+		elog(DEBUG1,
+			 "logical replication did not find row to be deleted "
+			 "in replication target relation \"%s\"",
+			 RelationGetRelationName(localrel));
+	}
+
+	/* Cleanup. */
+	ExecCloseIndices(relinfo);
+	EvalPlanQualEnd(&epqstate);
+}
+
+/*
+ * Try to find a tuple received from the publication side (in 'remoteslot') in
+ * the corresponding local relation using either replica identity index,
+ * primary key or if needed, sequential scan.
+ *
+ * Local tuple, if found, is returned in '*localslot'.
+ */
+static bool
+FindReplTupleInLocalRel(EState *estate, Relation localrel,
+						LogicalRepRelation *remoterel,
+						TupleTableSlot *remoteslot,
+						TupleTableSlot **localslot)
+{
+	Oid			idxoid;
+	bool		found;
+
+	*localslot = table_slot_create(localrel, &estate->es_tupleTable);
+
+	idxoid = GetRelationIdentityOrPK(localrel);
+	Assert(OidIsValid(idxoid) ||
+		   (remoterel->replident == REPLICA_IDENTITY_FULL));
+
+	if (OidIsValid(idxoid))
+		found = RelationFindReplTupleByIndex(localrel, idxoid,
+											 LockTupleExclusive,
+											 remoteslot, *localslot);
+	else
+		found = RelationFindReplTupleSeq(localrel, LockTupleExclusive,
+										 remoteslot, *localslot);
+
+	return found;
+}
+
+/*
+ * This handles insert, update, delete on a partitioned table.
+ */
+static void
+apply_handle_tuple_routing(ApplyExecutionData *edata,
+						   TupleTableSlot *remoteslot,
+						   LogicalRepTupleData *newtup,
+						   CmdType operation)
+{
+	EState	   *estate = edata->estate;
+	LogicalRepRelMapEntry *relmapentry = edata->targetRel;
+	ResultRelInfo *relinfo = edata->targetRelInfo;
+	Relation	parentrel = relinfo->ri_RelationDesc;
+	ModifyTableState *mtstate;
+	PartitionTupleRouting *proute;
+	ResultRelInfo *partrelinfo;
+	Relation	partrel;
+	TupleTableSlot *remoteslot_part;
+	TupleConversionMap *map;
+	MemoryContext oldctx;
+	LogicalRepRelMapEntry *part_entry = NULL;
+	AttrMap    *attrmap = NULL;
+
+	/* ModifyTableState is needed for ExecFindPartition(). */
+	edata->mtstate = mtstate = makeNode(ModifyTableState);
+	mtstate->ps.plan = NULL;
+	mtstate->ps.state = estate;
+	mtstate->operation = operation;
+	mtstate->resultRelInfo = relinfo;
+
+	/* ... as is PartitionTupleRouting. */
+	edata->proute = proute = ExecSetupPartitionTupleRouting(estate, parentrel);
+
+	/*
+	 * Find the partition to which the "search tuple" belongs.
+	 */
+	Assert(remoteslot != NULL);
+	oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
+	partrelinfo = ExecFindPartition(mtstate, relinfo, proute,
+									remoteslot, estate);
+	Assert(partrelinfo != NULL);
+	partrel = partrelinfo->ri_RelationDesc;
+
+	/*
+	 * To perform any of the operations below, the tuple must match the
+	 * partition's rowtype. Convert if needed or just copy, using a dedicated
+	 * slot to store the tuple in any case.
+	 */
+	remoteslot_part = partrelinfo->ri_PartitionTupleSlot;
+	if (remoteslot_part == NULL)
+		remoteslot_part = table_slot_create(partrel, &estate->es_tupleTable);
+	map = partrelinfo->ri_RootToPartitionMap;
+	if (map != NULL)
+	{
+		attrmap = map->attrMap;
+		remoteslot_part = execute_attr_map_slot(attrmap, remoteslot,
+												remoteslot_part);
+	}
+	else
+	{
+		remoteslot_part = ExecCopySlot(remoteslot_part, remoteslot);
+		slot_getallattrs(remoteslot_part);
+	}
+	MemoryContextSwitchTo(oldctx);
+
+	/* Check if we can do the update or delete on the leaf partition. */
+	if (operation == CMD_UPDATE || operation == CMD_DELETE)
+	{
+		part_entry = logicalrep_partition_open(relmapentry, partrel,
+											   attrmap);
+		check_relation_updatable(part_entry);
+	}
+
+	switch (operation)
+	{
+		case CMD_INSERT:
+			apply_handle_insert_internal(edata, partrelinfo,
+										 remoteslot_part);
+			break;
+
+		case CMD_DELETE:
+			apply_handle_delete_internal(edata, partrelinfo,
+										 remoteslot_part);
+			break;
+
+		case CMD_UPDATE:
+
+			/*
+			 * For UPDATE, depending on whether or not the updated tuple
+			 * satisfies the partition's constraint, perform a simple UPDATE
+			 * of the partition or move the updated tuple into a different
+			 * suitable partition.
+			 */
+			{
+				TupleTableSlot *localslot;
+				ResultRelInfo *partrelinfo_new;
+				bool		found;
+
+				/* Get the matching local tuple from the partition. */
+				found = FindReplTupleInLocalRel(estate, partrel,
+												&part_entry->remoterel,
+												remoteslot_part, &localslot);
+				if (!found)
+				{
+					/*
+					 * The tuple to be updated could not be found.  Do nothing
+					 * except for emitting a log message.
+					 *
+					 * XXX should this be promoted to ereport(LOG) perhaps?
+					 */
+					elog(DEBUG1,
+						 "logical replication did not find row to be updated "
+						 "in replication target relation's partition \"%s\"",
+						 RelationGetRelationName(partrel));
+					return;
+				}
+
+				/*
+				 * Apply the update to the local tuple, putting the result in
+				 * remoteslot_part.
+				 */
+				oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
+				slot_modify_data(remoteslot_part, localslot, part_entry,
+								 newtup);
+				MemoryContextSwitchTo(oldctx);
+
+				/*
+				 * Does the updated tuple still satisfy the current
+				 * partition's constraint?
+				 */
+				if (!partrel->rd_rel->relispartition ||
+					ExecPartitionCheck(partrelinfo, remoteslot_part, estate,
+									   false))
+				{
+					/*
+					 * Yes, so simply UPDATE the partition.  We don't call
+					 * apply_handle_update_internal() here, which would
+					 * normally do the following work, to avoid repeating some
+					 * work already done above to find the local tuple in the
+					 * partition.
+					 */
+					EPQState	epqstate;
+
+					EvalPlanQualInit(&epqstate, estate, NULL, NIL, -1);
+					ExecOpenIndices(partrelinfo, false);
+
+					EvalPlanQualSetSlot(&epqstate, remoteslot_part);
+					ExecSimpleRelationUpdate(partrelinfo, estate, &epqstate,
+											 localslot, remoteslot_part);
+					ExecCloseIndices(partrelinfo);
+					EvalPlanQualEnd(&epqstate);
+				}
+				else
+				{
+					/* Move the tuple into the new partition. */
+
+					/*
+					 * New partition will be found using tuple routing, which
+					 * can only occur via the parent table.  We might need to
+					 * convert the tuple to the parent's rowtype.  Note that
+					 * this is the tuple found in the partition, not the
+					 * original search tuple received by this function.
+					 */
+					if (map)
+					{
+						TupleConversionMap *PartitionToRootMap =
+						convert_tuples_by_name(RelationGetDescr(partrel),
+											   RelationGetDescr(parentrel));
+
+						remoteslot =
+							execute_attr_map_slot(PartitionToRootMap->attrMap,
+												  remoteslot_part, remoteslot);
+					}
+					else
+					{
+						remoteslot = ExecCopySlot(remoteslot, remoteslot_part);
+						slot_getallattrs(remoteslot);
+					}
+
+
+					/* Find the new partition. */
+					oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
+					partrelinfo_new = ExecFindPartition(mtstate, relinfo,
+														proute, remoteslot,
+														estate);
+					MemoryContextSwitchTo(oldctx);
+					Assert(partrelinfo_new != partrelinfo);
+
+					/* DELETE old tuple found in the old partition. */
+					apply_handle_delete_internal(edata, partrelinfo,
+												 localslot);
+
+					/* INSERT new tuple into the new partition. */
+
+					/*
+					 * Convert the replacement tuple to match the destination
+					 * partition rowtype.
+					 */
+					oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
+					partrel = partrelinfo_new->ri_RelationDesc;
+					remoteslot_part = partrelinfo_new->ri_PartitionTupleSlot;
+					if (remoteslot_part == NULL)
+						remoteslot_part = table_slot_create(partrel,
+															&estate->es_tupleTable);
+					map = partrelinfo_new->ri_RootToPartitionMap;
+					if (map != NULL)
+					{
+						remoteslot_part = execute_attr_map_slot(map->attrMap,
+																remoteslot,
+																remoteslot_part);
+					}
+					else
+					{
+						remoteslot_part = ExecCopySlot(remoteslot_part,
+													   remoteslot);
+						slot_getallattrs(remoteslot);
+					}
+					MemoryContextSwitchTo(oldctx);
+					apply_handle_insert_internal(edata, partrelinfo_new,
+												 remoteslot_part);
+				}
+			}
+			break;
+
+		default:
+			elog(ERROR, "unrecognized CmdType: %d", (int) operation);
+			break;
+	}
+}
+
+/*
+ * Handle TRUNCATE message.
+ *
+ * TODO: FDW support
+ */
+static void
+apply_handle_truncate(StringInfo s)
+{
+	bool		cascade = false;
+	bool		restart_seqs = false;
+	List	   *remote_relids = NIL;
+	List	   *remote_rels = NIL;
+	List	   *rels = NIL;
+	List	   *part_rels = NIL;
+	List	   *relids = NIL;
+	List	   *relids_logged = NIL;
+	ListCell   *lc;
+	LOCKMODE	lockmode = AccessExclusiveLock;
+
+	if (handle_streamed_transaction(LOGICAL_REP_MSG_TRUNCATE, s))
+		return;
+
+	begin_replication_step();
+
+	remote_relids = logicalrep_read_truncate(s, &cascade, &restart_seqs);
+
+	foreach(lc, remote_relids)
+	{
+		LogicalRepRelId relid = lfirst_oid(lc);
+		LogicalRepRelMapEntry *rel;
+
+		rel = logicalrep_rel_open(relid, lockmode);
+		if (!should_apply_changes_for_rel(rel))
+		{
+			/*
+			 * The relation can't become interesting in the middle of the
+			 * transaction so it's safe to unlock it.
+			 */
+			logicalrep_rel_close(rel, lockmode);
+			continue;
+		}
+
+		remote_rels = lappend(remote_rels, rel);
+		rels = lappend(rels, rel->localrel);
+		relids = lappend_oid(relids, rel->localreloid);
+		if (RelationIsLogicallyLogged(rel->localrel))
+			relids_logged = lappend_oid(relids_logged, rel->localreloid);
+
+		/*
+		 * Truncate partitions if we got a message to truncate a partitioned
+		 * table.
+		 */
+		if (rel->localrel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
+		{
+			ListCell   *child;
+			List	   *children = find_all_inheritors(rel->localreloid,
+													   lockmode,
+													   NULL);
+
+			foreach(child, children)
+			{
+				Oid			childrelid = lfirst_oid(child);
+				Relation	childrel;
+
+				if (list_member_oid(relids, childrelid))
+					continue;
+
+				/* find_all_inheritors already got lock */
+				childrel = table_open(childrelid, NoLock);
+
+				/*
+				 * Ignore temp tables of other backends.  See similar code in
+				 * ExecuteTruncate().
+				 */
+				if (RELATION_IS_OTHER_TEMP(childrel))
+				{
+					table_close(childrel, lockmode);
+					continue;
+				}
+
+				rels = lappend(rels, childrel);
+				part_rels = lappend(part_rels, childrel);
+				relids = lappend_oid(relids, childrelid);
+				/* Log this relation only if needed for logical decoding */
+				if (RelationIsLogicallyLogged(childrel))
+					relids_logged = lappend_oid(relids_logged, childrelid);
+			}
+		}
+	}
+
+	/*
+	 * Even if we used CASCADE on the upstream primary we explicitly default
+	 * to replaying changes without further cascading. This might be later
+	 * changeable with a user specified option.
+	 */
+	ExecuteTruncateGuts(rels,
+						relids,
+						relids_logged,
+						DROP_RESTRICT,
+						restart_seqs);
+	foreach(lc, remote_rels)
+	{
+		LogicalRepRelMapEntry *rel = lfirst(lc);
+
+		logicalrep_rel_close(rel, NoLock);
+	}
+	foreach(lc, part_rels)
+	{
+		Relation	rel = lfirst(lc);
+
+		table_close(rel, NoLock);
+	}
+
+	end_replication_step();
+}
+
+
+/*
+ * Logical replication protocol message dispatcher.
+ */
+static void
+apply_dispatch(StringInfo s)
+{
+	LogicalRepMsgType action = pq_getmsgbyte(s);
+
+	switch (action)
+	{
+		case LOGICAL_REP_MSG_BEGIN:
+			apply_handle_begin(s);
+			return;
+
+		case LOGICAL_REP_MSG_COMMIT:
+			apply_handle_commit(s);
+			return;
+
+		case LOGICAL_REP_MSG_INSERT:
+			apply_handle_insert(s);
+			return;
+
+		case LOGICAL_REP_MSG_UPDATE:
+			apply_handle_update(s);
+			return;
+
+		case LOGICAL_REP_MSG_DELETE:
+			apply_handle_delete(s);
+			return;
+
+		case LOGICAL_REP_MSG_TRUNCATE:
+			apply_handle_truncate(s);
+			return;
+
+		case LOGICAL_REP_MSG_RELATION:
+			apply_handle_relation(s);
+			return;
+
+		case LOGICAL_REP_MSG_TYPE:
+			apply_handle_type(s);
+			return;
+
+		case LOGICAL_REP_MSG_ORIGIN:
+			apply_handle_origin(s);
+			return;
+
+		case LOGICAL_REP_MSG_MESSAGE:
+
+			/*
+			 * Logical replication does not use generic logical messages yet.
+			 * Although, it could be used by other applications that use this
+			 * output plugin.
+			 */
+			return;
+
+		case LOGICAL_REP_MSG_STREAM_START:
+			apply_handle_stream_start(s);
+			return;
+
+		case LOGICAL_REP_MSG_STREAM_END:
+			apply_handle_stream_stop(s);
+			return;
+
+		case LOGICAL_REP_MSG_STREAM_ABORT:
+			apply_handle_stream_abort(s);
+			return;
+
+		case LOGICAL_REP_MSG_STREAM_COMMIT:
+			apply_handle_stream_commit(s);
+			return;
+	}
+
+	ereport(ERROR,
+			(errcode(ERRCODE_PROTOCOL_VIOLATION),
+			 errmsg_internal("invalid logical replication message type \"%c\"",
+							 action)));
+}
+
+/*
+ * Figure out which write/flush positions to report to the walsender process.
+ *
+ * We can't simply report back the last LSN the walsender sent us because the
+ * local transaction might not yet be flushed to disk locally. Instead we
+ * build a list that associates local with remote LSNs for every commit. When
+ * reporting back the flush position to the sender we iterate that list and
+ * check which entries on it are already locally flushed. Those we can report
+ * as having been flushed.
+ *
+ * The have_pending_txes is true if there are outstanding transactions that
+ * need to be flushed.
+ */
+static void
+get_flush_position(XLogRecPtr *write, XLogRecPtr *flush,
+				   bool *have_pending_txes)
+{
+	dlist_mutable_iter iter;
+	XLogRecPtr	local_flush = GetFlushRecPtr();
+
+	*write = InvalidXLogRecPtr;
+	*flush = InvalidXLogRecPtr;
+
+	dlist_foreach_modify(iter, &lsn_mapping)
+	{
+		FlushPosition *pos =
+		dlist_container(FlushPosition, node, iter.cur);
+
+		*write = pos->remote_end;
+
+		if (pos->local_end <= local_flush)
+		{
+			*flush = pos->remote_end;
+			dlist_delete(iter.cur);
+			pfree(pos);
+		}
+		else
+		{
+			/*
+			 * Don't want to uselessly iterate over the rest of the list which
+			 * could potentially be long. Instead get the last element and
+			 * grab the write position from there.
+			 */
+			pos = dlist_tail_element(FlushPosition, node,
+									 &lsn_mapping);
+			*write = pos->remote_end;
+			*have_pending_txes = true;
+			return;
+		}
+	}
+
+	*have_pending_txes = !dlist_is_empty(&lsn_mapping);
+}
+
+/*
+ * Store current remote/local lsn pair in the tracking list.
+ */
+static void
+store_flush_position(XLogRecPtr remote_lsn)
+{
+	FlushPosition *flushpos;
+
+	/* Need to do this in permanent context */
+	MemoryContextSwitchTo(ApplyContext);
+
+	/* Track commit lsn  */
+	flushpos = (FlushPosition *) palloc(sizeof(FlushPosition));
+	flushpos->local_end = XactLastCommitEnd;
+	flushpos->remote_end = remote_lsn;
+
+	dlist_push_tail(&lsn_mapping, &flushpos->node);
+	MemoryContextSwitchTo(ApplyMessageContext);
+}
+
+
+/* Update statistics of the worker. */
+static void
+UpdateWorkerStats(XLogRecPtr last_lsn, TimestampTz send_time, bool reply)
+{
+	MyLogicalRepWorker->last_lsn = last_lsn;
+	MyLogicalRepWorker->last_send_time = send_time;
+	MyLogicalRepWorker->last_recv_time = GetCurrentTimestamp();
+	if (reply)
+	{
+		MyLogicalRepWorker->reply_lsn = last_lsn;
+		MyLogicalRepWorker->reply_time = send_time;
+	}
+}
+
+/*
+ * Apply main loop.
+ */
+static void
+LogicalRepApplyLoop(XLogRecPtr last_received)
+{
+	TimestampTz last_recv_timestamp = GetCurrentTimestamp();
+	bool		ping_sent = false;
+	TimeLineID	tli;
+
+	/*
+	 * Init the ApplyMessageContext which we clean up after each replication
+	 * protocol message.
+	 */
+	ApplyMessageContext = AllocSetContextCreate(ApplyContext,
+												"ApplyMessageContext",
+												ALLOCSET_DEFAULT_SIZES);
+
+	/*
+	 * This memory context is used for per-stream data when the streaming mode
+	 * is enabled. This context is reset on each stream stop.
+	 */
+	LogicalStreamingContext = AllocSetContextCreate(ApplyContext,
+													"LogicalStreamingContext",
+													ALLOCSET_DEFAULT_SIZES);
+
+	/* mark as idle, before starting to loop */
+	pgstat_report_activity(STATE_IDLE, NULL);
+
+	/* This outer loop iterates once per wait. */
+	for (;;)
+	{
+		pgsocket	fd = PGINVALID_SOCKET;
+		int			rc;
+		int			len;
+		char	   *buf = NULL;
+		bool		endofstream = false;
+		long		wait_time;
+
+		CHECK_FOR_INTERRUPTS();
+
+		MemoryContextSwitchTo(ApplyMessageContext);
+
+		len = walrcv_receive(LogRepWorkerWalRcvConn, &buf, &fd);
+
+		if (len != 0)
+		{
+			/* Loop to process all available data (without blocking). */
+			for (;;)
+			{
+				CHECK_FOR_INTERRUPTS();
+
+				if (len == 0)
+				{
+					break;
+				}
+				else if (len < 0)
+				{
+					ereport(LOG,
+							(errmsg("data stream from publisher has ended")));
+					endofstream = true;
+					break;
+				}
+				else
+				{
+					int			c;
+					StringInfoData s;
+
+					/* Reset timeout. */
+					last_recv_timestamp = GetCurrentTimestamp();
+					ping_sent = false;
+
+					/* Ensure we are reading the data into our memory context. */
+					MemoryContextSwitchTo(ApplyMessageContext);
+
+					s.data = buf;
+					s.len = len;
+					s.cursor = 0;
+					s.maxlen = -1;
+
+					c = pq_getmsgbyte(&s);
+
+					if (c == 'w')
+					{
+						XLogRecPtr	start_lsn;
+						XLogRecPtr	end_lsn;
+						TimestampTz send_time;
+
+						start_lsn = pq_getmsgint64(&s);
+						end_lsn = pq_getmsgint64(&s);
+						send_time = pq_getmsgint64(&s);
+
+						if (last_received < start_lsn)
+							last_received = start_lsn;
+
+						if (last_received < end_lsn)
+							last_received = end_lsn;
+
+						UpdateWorkerStats(last_received, send_time, false);
+
+						apply_dispatch(&s);
+					}
+					else if (c == 'k')
+					{
+						XLogRecPtr	end_lsn;
+						TimestampTz timestamp;
+						bool		reply_requested;
+
+						end_lsn = pq_getmsgint64(&s);
+						timestamp = pq_getmsgint64(&s);
+						reply_requested = pq_getmsgbyte(&s);
+
+						if (last_received < end_lsn)
+							last_received = end_lsn;
+
+						send_feedback(last_received, reply_requested, false);
+						UpdateWorkerStats(last_received, timestamp, true);
+					}
+					/* other message types are purposefully ignored */
+
+					MemoryContextReset(ApplyMessageContext);
+				}
+
+				len = walrcv_receive(LogRepWorkerWalRcvConn, &buf, &fd);
+			}
+		}
+
+		/* confirm all writes so far */
+		send_feedback(last_received, false, false);
+
+		if (!in_remote_transaction && !in_streamed_transaction)
+		{
+			/*
+			 * If we didn't get any transactions for a while there might be
+			 * unconsumed invalidation messages in the queue, consume them
+			 * now.
+			 */
+			AcceptInvalidationMessages();
+			maybe_reread_subscription();
+
+			/* Process any table synchronization changes. */
+			process_syncing_tables(last_received);
+		}
+
+		/* Cleanup the memory. */
+		MemoryContextResetAndDeleteChildren(ApplyMessageContext);
+		MemoryContextSwitchTo(TopMemoryContext);
+
+		/* Check if we need to exit the streaming loop. */
+		if (endofstream)
+			break;
+
+		/*
+		 * Wait for more data or latch.  If we have unflushed transactions,
+		 * wake up after WalWriterDelay to see if they've been flushed yet (in
+		 * which case we should send a feedback message).  Otherwise, there's
+		 * no particular urgency about waking up unless we get data or a
+		 * signal.
+		 */
+		if (!dlist_is_empty(&lsn_mapping))
+			wait_time = WalWriterDelay;
+		else
+			wait_time = NAPTIME_PER_CYCLE;
+
+		rc = WaitLatchOrSocket(MyLatch,
+							   WL_SOCKET_READABLE | WL_LATCH_SET |
+							   WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
+							   fd, wait_time,
+							   WAIT_EVENT_LOGICAL_APPLY_MAIN);
+
+		if (rc & WL_LATCH_SET)
+		{
+			ResetLatch(MyLatch);
+			CHECK_FOR_INTERRUPTS();
+		}
+
+		if (ConfigReloadPending)
+		{
+			ConfigReloadPending = false;
+			ProcessConfigFile(PGC_SIGHUP);
+		}
+
+		if (rc & WL_TIMEOUT)
+		{
+			/*
+			 * We didn't receive anything new. If we haven't heard anything
+			 * from the server for more than wal_receiver_timeout / 2, ping
+			 * the server. Also, if it's been longer than
+			 * wal_receiver_status_interval since the last update we sent,
+			 * send a status update to the primary anyway, to report any
+			 * progress in applying WAL.
+			 */
+			bool		requestReply = false;
+
+			/*
+			 * Check if time since last receive from primary has reached the
+			 * configured limit.
+			 */
+			if (wal_receiver_timeout > 0)
+			{
+				TimestampTz now = GetCurrentTimestamp();
+				TimestampTz timeout;
+
+				timeout =
+					TimestampTzPlusMilliseconds(last_recv_timestamp,
+												wal_receiver_timeout);
+
+				if (now >= timeout)
+					ereport(ERROR,
+							(errcode(ERRCODE_CONNECTION_FAILURE),
+							 errmsg("terminating logical replication worker due to timeout")));
+
+				/* Check to see if it's time for a ping. */
+				if (!ping_sent)
+				{
+					timeout = TimestampTzPlusMilliseconds(last_recv_timestamp,
+														  (wal_receiver_timeout / 2));
+					if (now >= timeout)
+					{
+						requestReply = true;
+						ping_sent = true;
+					}
+				}
+			}
+
+			send_feedback(last_received, requestReply, requestReply);
+		}
+	}
+
+	/* All done */
+	walrcv_endstreaming(LogRepWorkerWalRcvConn, &tli);
+}
+
+/*
+ * Send a Standby Status Update message to server.
+ *
+ * 'recvpos' is the latest LSN we've received data to, force is set if we need
+ * to send a response to avoid timeouts.
+ */
+static void
+send_feedback(XLogRecPtr recvpos, bool force, bool requestReply)
+{
+	static StringInfo reply_message = NULL;
+	static TimestampTz send_time = 0;
+
+	static XLogRecPtr last_recvpos = InvalidXLogRecPtr;
+	static XLogRecPtr last_writepos = InvalidXLogRecPtr;
+	static XLogRecPtr last_flushpos = InvalidXLogRecPtr;
+
+	XLogRecPtr	writepos;
+	XLogRecPtr	flushpos;
+	TimestampTz now;
+	bool		have_pending_txes;
+
+	/*
+	 * If the user doesn't want status to be reported to the publisher, be
+	 * sure to exit before doing anything at all.
+	 */
+	if (!force && wal_receiver_status_interval <= 0)
+		return;
+
+	/* It's legal to not pass a recvpos */
+	if (recvpos < last_recvpos)
+		recvpos = last_recvpos;
+
+	get_flush_position(&writepos, &flushpos, &have_pending_txes);
+
+	/*
+	 * No outstanding transactions to flush, we can report the latest received
+	 * position. This is important for synchronous replication.
+	 */
+	if (!have_pending_txes)
+		flushpos = writepos = recvpos;
+
+	if (writepos < last_writepos)
+		writepos = last_writepos;
+
+	if (flushpos < last_flushpos)
+		flushpos = last_flushpos;
+
+	now = GetCurrentTimestamp();
+
+	/* if we've already reported everything we're good */
+	if (!force &&
+		writepos == last_writepos &&
+		flushpos == last_flushpos &&
+		!TimestampDifferenceExceeds(send_time, now,
+									wal_receiver_status_interval * 1000))
+		return;
+	send_time = now;
+
+	if (!reply_message)
+	{
+		MemoryContext oldctx = MemoryContextSwitchTo(ApplyContext);
+
+		reply_message = makeStringInfo();
+		MemoryContextSwitchTo(oldctx);
+	}
+	else
+		resetStringInfo(reply_message);
+
+	pq_sendbyte(reply_message, 'r');
+	pq_sendint64(reply_message, recvpos);	/* write */
+	pq_sendint64(reply_message, flushpos);	/* flush */
+	pq_sendint64(reply_message, writepos);	/* apply */
+	pq_sendint64(reply_message, now);	/* sendTime */
+	pq_sendbyte(reply_message, requestReply);	/* replyRequested */
+
+	elog(DEBUG2, "sending feedback (force %d) to recv %X/%X, write %X/%X, flush %X/%X",
+		 force,
+		 LSN_FORMAT_ARGS(recvpos),
+		 LSN_FORMAT_ARGS(writepos),
+		 LSN_FORMAT_ARGS(flushpos));
+
+	walrcv_send(LogRepWorkerWalRcvConn,
+				reply_message->data, reply_message->len);
+
+	if (recvpos > last_recvpos)
+		last_recvpos = recvpos;
+	if (writepos > last_writepos)
+		last_writepos = writepos;
+	if (flushpos > last_flushpos)
+		last_flushpos = flushpos;
+}
+
+/*
+ * Reread subscription info if needed. Most changes will be exit.
+ */
+static void
+maybe_reread_subscription(void)
+{
+	MemoryContext oldctx;
+	Subscription *newsub;
+	bool		started_tx = false;
+
+	/* When cache state is valid there is nothing to do here. */
+	if (MySubscriptionValid)
+		return;
+
+	/* This function might be called inside or outside of transaction. */
+	if (!IsTransactionState())
+	{
+		StartTransactionCommand();
+		started_tx = true;
+	}
+
+	/* Ensure allocations in permanent context. */
+	oldctx = MemoryContextSwitchTo(ApplyContext);
+
+	newsub = GetSubscription(MyLogicalRepWorker->subid, true);
+
+	/*
+	 * Exit if the subscription was removed. This normally should not happen
+	 * as the worker gets killed during DROP SUBSCRIPTION.
+	 */
+	if (!newsub)
+	{
+		ereport(LOG,
+				(errmsg("logical replication apply worker for subscription \"%s\" will "
+						"stop because the subscription was removed",
+						MySubscription->name)));
+
+		proc_exit(0);
+	}
+
+	/*
+	 * Exit if the subscription was disabled. This normally should not happen
+	 * as the worker gets killed during ALTER SUBSCRIPTION ... DISABLE.
+	 */
+	if (!newsub->enabled)
+	{
+		ereport(LOG,
+				(errmsg("logical replication apply worker for subscription \"%s\" will "
+						"stop because the subscription was disabled",
+						MySubscription->name)));
+
+		proc_exit(0);
+	}
+
+	/* !slotname should never happen when enabled is true. */
+	Assert(newsub->slotname);
+
+	/*
+	 * Exit if any parameter that affects the remote connection was changed.
+	 * The launcher will start a new worker.
+	 */
+	if (strcmp(newsub->conninfo, MySubscription->conninfo) != 0 ||
+		strcmp(newsub->name, MySubscription->name) != 0 ||
+		strcmp(newsub->slotname, MySubscription->slotname) != 0 ||
+		newsub->binary != MySubscription->binary ||
+		newsub->stream != MySubscription->stream ||
+		!equal(newsub->publications, MySubscription->publications))
+	{
+		ereport(LOG,
+				(errmsg("logical replication apply worker for subscription \"%s\" will restart because of a parameter change",
+						MySubscription->name)));
+
+		proc_exit(0);
+	}
+
+	/* Check for other changes that should never happen too. */
+	if (newsub->dbid != MySubscription->dbid)
+	{
+		elog(ERROR, "subscription %u changed unexpectedly",
+			 MyLogicalRepWorker->subid);
+	}
+
+	/* Clean old subscription info and switch to new one. */
+	FreeSubscription(MySubscription);
+	MySubscription = newsub;
+
+	MemoryContextSwitchTo(oldctx);
+
+	/* Change synchronous commit according to the user's wishes */
+	SetConfigOption("synchronous_commit", MySubscription->synccommit,
+					PGC_BACKEND, PGC_S_OVERRIDE);
+
+	if (started_tx)
+		CommitTransactionCommand();
+
+	MySubscriptionValid = true;
+}
+
+/*
+ * Callback from subscription syscache invalidation.
+ */
+static void
+subscription_change_cb(Datum arg, int cacheid, uint32 hashvalue)
+{
+	MySubscriptionValid = false;
+}
+
+/*
+ * subxact_info_write
+ *	  Store information about subxacts for a toplevel transaction.
+ *
+ * For each subxact we store offset of it's first change in the main file.
+ * The file is always over-written as a whole.
+ *
+ * XXX We should only store subxacts that were not aborted yet.
+ */
+static void
+subxact_info_write(Oid subid, TransactionId xid)
+{
+	char		path[MAXPGPATH];
+	Size		len;
+	StreamXidHash *ent;
+	BufFile    *fd;
+
+	Assert(TransactionIdIsValid(xid));
+
+	/* Find the xid entry in the xidhash */
+	ent = (StreamXidHash *) hash_search(xidhash,
+										(void *) &xid,
+										HASH_FIND,
+										NULL);
+	/* By this time we must have created the transaction entry */
+	Assert(ent);
+
+	/*
+	 * If there is no subtransaction then nothing to do, but if already have
+	 * subxact file then delete that.
+	 */
+	if (subxact_data.nsubxacts == 0)
+	{
+		if (ent->subxact_fileset)
+		{
+			cleanup_subxact_info();
+			SharedFileSetDeleteAll(ent->subxact_fileset);
+			pfree(ent->subxact_fileset);
+			ent->subxact_fileset = NULL;
+		}
+		return;
+	}
+
+	subxact_filename(path, subid, xid);
+
+	/*
+	 * Create the subxact file if it not already created, otherwise open the
+	 * existing file.
+	 */
+	if (ent->subxact_fileset == NULL)
+	{
+		MemoryContext oldctx;
+
+		/*
+		 * We need to maintain shared fileset across multiple stream
+		 * start/stop calls.  So, need to allocate it in a persistent context.
+		 */
+		oldctx = MemoryContextSwitchTo(ApplyContext);
+		ent->subxact_fileset = palloc(sizeof(SharedFileSet));
+		SharedFileSetInit(ent->subxact_fileset, NULL);
+		MemoryContextSwitchTo(oldctx);
+
+		fd = BufFileCreateShared(ent->subxact_fileset, path);
+	}
+	else
+		fd = BufFileOpenShared(ent->subxact_fileset, path, O_RDWR);
+
+	len = sizeof(SubXactInfo) * subxact_data.nsubxacts;
+
+	/* Write the subxact count and subxact info */
+	BufFileWrite(fd, &subxact_data.nsubxacts, sizeof(subxact_data.nsubxacts));
+	BufFileWrite(fd, subxact_data.subxacts, len);
+
+	BufFileClose(fd);
+
+	/* free the memory allocated for subxact info */
+	cleanup_subxact_info();
+}
+
+/*
+ * subxact_info_read
+ *	  Restore information about subxacts of a streamed transaction.
+ *
+ * Read information about subxacts into the structure subxact_data that can be
+ * used later.
+ */
+static void
+subxact_info_read(Oid subid, TransactionId xid)
+{
+	char		path[MAXPGPATH];
+	Size		len;
+	BufFile    *fd;
+	StreamXidHash *ent;
+	MemoryContext oldctx;
+
+	Assert(!subxact_data.subxacts);
+	Assert(subxact_data.nsubxacts == 0);
+	Assert(subxact_data.nsubxacts_max == 0);
+
+	/* Find the stream xid entry in the xidhash */
+	ent = (StreamXidHash *) hash_search(xidhash,
+										(void *) &xid,
+										HASH_FIND,
+										NULL);
+	if (!ent)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg_internal("transaction %u not found in stream XID hash table",
+								 xid)));
+
+	/*
+	 * If subxact_fileset is not valid that mean we don't have any subxact
+	 * info
+	 */
+	if (ent->subxact_fileset == NULL)
+		return;
+
+	subxact_filename(path, subid, xid);
+
+	fd = BufFileOpenShared(ent->subxact_fileset, path, O_RDONLY);
+
+	/* read number of subxact items */
+	if (BufFileRead(fd, &subxact_data.nsubxacts,
+					sizeof(subxact_data.nsubxacts)) !=
+		sizeof(subxact_data.nsubxacts))
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not read from streaming transaction's subxact file \"%s\": %m",
+						path)));
+
+	len = sizeof(SubXactInfo) * subxact_data.nsubxacts;
+
+	/* we keep the maximum as a power of 2 */
+	subxact_data.nsubxacts_max = 1 << my_log2(subxact_data.nsubxacts);
+
+	/*
+	 * Allocate subxact information in the logical streaming context. We need
+	 * this information during the complete stream so that we can add the sub
+	 * transaction info to this. On stream stop we will flush this information
+	 * to the subxact file and reset the logical streaming context.
+	 */
+	oldctx = MemoryContextSwitchTo(LogicalStreamingContext);
+	subxact_data.subxacts = palloc(subxact_data.nsubxacts_max *
+								   sizeof(SubXactInfo));
+	MemoryContextSwitchTo(oldctx);
+
+	if ((len > 0) && ((BufFileRead(fd, subxact_data.subxacts, len)) != len))
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not read from streaming transaction's subxact file \"%s\": %m",
+						path)));
+
+	BufFileClose(fd);
+}
+
+/*
+ * subxact_info_add
+ *	  Add information about a subxact (offset in the main file).
+ */
+static void
+subxact_info_add(TransactionId xid)
+{
+	SubXactInfo *subxacts = subxact_data.subxacts;
+	int64		i;
+
+	/* We must have a valid top level stream xid and a stream fd. */
+	Assert(TransactionIdIsValid(stream_xid));
+	Assert(stream_fd != NULL);
+
+	/*
+	 * If the XID matches the toplevel transaction, we don't want to add it.
+	 */
+	if (stream_xid == xid)
+		return;
+
+	/*
+	 * In most cases we're checking the same subxact as we've already seen in
+	 * the last call, so make sure to ignore it (this change comes later).
+	 */
+	if (subxact_data.subxact_last == xid)
+		return;
+
+	/* OK, remember we're processing this XID. */
+	subxact_data.subxact_last = xid;
+
+	/*
+	 * Check if the transaction is already present in the array of subxact. We
+	 * intentionally scan the array from the tail, because we're likely adding
+	 * a change for the most recent subtransactions.
+	 *
+	 * XXX Can we rely on the subxact XIDs arriving in sorted order? That
+	 * would allow us to use binary search here.
+	 */
+	for (i = subxact_data.nsubxacts; i > 0; i--)
+	{
+		/* found, so we're done */
+		if (subxacts[i - 1].xid == xid)
+			return;
+	}
+
+	/* This is a new subxact, so we need to add it to the array. */
+	if (subxact_data.nsubxacts == 0)
+	{
+		MemoryContext oldctx;
+
+		subxact_data.nsubxacts_max = 128;
+
+		/*
+		 * Allocate this memory for subxacts in per-stream context, see
+		 * subxact_info_read.
+		 */
+		oldctx = MemoryContextSwitchTo(LogicalStreamingContext);
+		subxacts = palloc(subxact_data.nsubxacts_max * sizeof(SubXactInfo));
+		MemoryContextSwitchTo(oldctx);
+	}
+	else if (subxact_data.nsubxacts == subxact_data.nsubxacts_max)
+	{
+		subxact_data.nsubxacts_max *= 2;
+		subxacts = repalloc(subxacts,
+							subxact_data.nsubxacts_max * sizeof(SubXactInfo));
+	}
+
+	subxacts[subxact_data.nsubxacts].xid = xid;
+
+	/*
+	 * Get the current offset of the stream file and store it as offset of
+	 * this subxact.
+	 */
+	BufFileTell(stream_fd,
+				&subxacts[subxact_data.nsubxacts].fileno,
+				&subxacts[subxact_data.nsubxacts].offset);
+
+	subxact_data.nsubxacts++;
+	subxact_data.subxacts = subxacts;
+}
+
+/* format filename for file containing the info about subxacts */
+static inline void
+subxact_filename(char *path, Oid subid, TransactionId xid)
+{
+	snprintf(path, MAXPGPATH, "%u-%u.subxacts", subid, xid);
+}
+
+/* format filename for file containing serialized changes */
+static inline void
+changes_filename(char *path, Oid subid, TransactionId xid)
+{
+	snprintf(path, MAXPGPATH, "%u-%u.changes", subid, xid);
+}
+
+/*
+ * stream_cleanup_files
+ *	  Cleanup files for a subscription / toplevel transaction.
+ *
+ * Remove files with serialized changes and subxact info for a particular
+ * toplevel transaction. Each subscription has a separate set of files.
+ */
+static void
+stream_cleanup_files(Oid subid, TransactionId xid)
+{
+	char		path[MAXPGPATH];
+	StreamXidHash *ent;
+
+	/* Find the xid entry in the xidhash */
+	ent = (StreamXidHash *) hash_search(xidhash,
+										(void *) &xid,
+										HASH_FIND,
+										NULL);
+	if (!ent)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg_internal("transaction %u not found in stream XID hash table",
+								 xid)));
+
+	/* Delete the change file and release the stream fileset memory */
+	changes_filename(path, subid, xid);
+	SharedFileSetDeleteAll(ent->stream_fileset);
+	pfree(ent->stream_fileset);
+	ent->stream_fileset = NULL;
+
+	/* Delete the subxact file and release the memory, if it exist */
+	if (ent->subxact_fileset)
+	{
+		subxact_filename(path, subid, xid);
+		SharedFileSetDeleteAll(ent->subxact_fileset);
+		pfree(ent->subxact_fileset);
+		ent->subxact_fileset = NULL;
+	}
+
+	/* Remove the xid entry from the stream xid hash */
+	hash_search(xidhash, (void *) &xid, HASH_REMOVE, NULL);
+}
+
+/*
+ * stream_open_file
+ *	  Open a file that we'll use to serialize changes for a toplevel
+ * transaction.
+ *
+ * Open a file for streamed changes from a toplevel transaction identified
+ * by stream_xid (global variable). If it's the first chunk of streamed
+ * changes for this transaction, initialize the shared fileset and create the
+ * buffile, otherwise open the previously created file.
+ *
+ * This can only be called at the beginning of a "streaming" block, i.e.
+ * between stream_start/stream_stop messages from the upstream.
+ */
+static void
+stream_open_file(Oid subid, TransactionId xid, bool first_segment)
+{
+	char		path[MAXPGPATH];
+	bool		found;
+	MemoryContext oldcxt;
+	StreamXidHash *ent;
+
+	Assert(in_streamed_transaction);
+	Assert(OidIsValid(subid));
+	Assert(TransactionIdIsValid(xid));
+	Assert(stream_fd == NULL);
+
+	/* create or find the xid entry in the xidhash */
+	ent = (StreamXidHash *) hash_search(xidhash,
+										(void *) &xid,
+										HASH_ENTER,
+										&found);
+
+	changes_filename(path, subid, xid);
+	elog(DEBUG1, "opening file \"%s\" for streamed changes", path);
+
+	/*
+	 * Create/open the buffiles under the logical streaming context so that we
+	 * have those files until stream stop.
+	 */
+	oldcxt = MemoryContextSwitchTo(LogicalStreamingContext);
+
+	/*
+	 * If this is the first streamed segment, the file must not exist, so make
+	 * sure we're the ones creating it. Otherwise just open the file for
+	 * writing, in append mode.
+	 */
+	if (first_segment)
+	{
+		MemoryContext savectx;
+		SharedFileSet *fileset;
+
+		if (found)
+			ereport(ERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg_internal("incorrect first-segment flag for streamed replication transaction")));
+
+		/*
+		 * We need to maintain shared fileset across multiple stream
+		 * start/stop calls. So, need to allocate it in a persistent context.
+		 */
+		savectx = MemoryContextSwitchTo(ApplyContext);
+		fileset = palloc(sizeof(SharedFileSet));
+
+		SharedFileSetInit(fileset, NULL);
+		MemoryContextSwitchTo(savectx);
+
+		stream_fd = BufFileCreateShared(fileset, path);
+
+		/* Remember the fileset for the next stream of the same transaction */
+		ent->xid = xid;
+		ent->stream_fileset = fileset;
+		ent->subxact_fileset = NULL;
+	}
+	else
+	{
+		if (!found)
+			ereport(ERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg_internal("incorrect first-segment flag for streamed replication transaction")));
+
+		/*
+		 * Open the file and seek to the end of the file because we always
+		 * append the changes file.
+		 */
+		stream_fd = BufFileOpenShared(ent->stream_fileset, path, O_RDWR);
+		BufFileSeek(stream_fd, 0, 0, SEEK_END);
+	}
+
+	MemoryContextSwitchTo(oldcxt);
+}
+
+/*
+ * stream_close_file
+ *	  Close the currently open file with streamed changes.
+ *
+ * This can only be called at the end of a streaming block, i.e. at stream_stop
+ * message from the upstream.
+ */
+static void
+stream_close_file(void)
+{
+	Assert(in_streamed_transaction);
+	Assert(TransactionIdIsValid(stream_xid));
+	Assert(stream_fd != NULL);
+
+	BufFileClose(stream_fd);
+
+	stream_xid = InvalidTransactionId;
+	stream_fd = NULL;
+}
+
+/*
+ * stream_write_change
+ *	  Serialize a change to a file for the current toplevel transaction.
+ *
+ * The change is serialized in a simple format, with length (not including
+ * the length), action code (identifying the message type) and message
+ * contents (without the subxact TransactionId value).
+ */
+static void
+stream_write_change(char action, StringInfo s)
+{
+	int			len;
+
+	Assert(in_streamed_transaction);
+	Assert(TransactionIdIsValid(stream_xid));
+	Assert(stream_fd != NULL);
+
+	/* total on-disk size, including the action type character */
+	len = (s->len - s->cursor) + sizeof(char);
+
+	/* first write the size */
+	BufFileWrite(stream_fd, &len, sizeof(len));
+
+	/* then the action */
+	BufFileWrite(stream_fd, &action, sizeof(action));
+
+	/* and finally the remaining part of the buffer (after the XID) */
+	len = (s->len - s->cursor);
+
+	BufFileWrite(stream_fd, &s->data[s->cursor], len);
+}
+
+/*
+ * Cleanup the memory for subxacts and reset the related variables.
+ */
+static inline void
+cleanup_subxact_info()
+{
+	if (subxact_data.subxacts)
+		pfree(subxact_data.subxacts);
+
+	subxact_data.subxacts = NULL;
+	subxact_data.subxact_last = InvalidTransactionId;
+	subxact_data.nsubxacts = 0;
+	subxact_data.nsubxacts_max = 0;
+}
+
+/* Logical Replication Apply worker entry point */
+void
+ApplyWorkerMain(Datum main_arg)
+{
+	int			worker_slot = DatumGetInt32(main_arg);
+	MemoryContext oldctx;
+	char		originname[NAMEDATALEN];
+	XLogRecPtr	origin_startpos;
+	char	   *myslotname;
+	WalRcvStreamOptions options;
+
+	/* Attach to slot */
+	logicalrep_worker_attach(worker_slot);
+
+	/* Setup signal handling */
+	pqsignal(SIGHUP, SignalHandlerForConfigReload);
+	pqsignal(SIGTERM, die);
+	BackgroundWorkerUnblockSignals();
+
+	/*
+	 * We don't currently need any ResourceOwner in a walreceiver process, but
+	 * if we did, we could call CreateAuxProcessResourceOwner here.
+	 */
+
+	/* Initialise stats to a sanish value */
+	MyLogicalRepWorker->last_send_time = MyLogicalRepWorker->last_recv_time =
+		MyLogicalRepWorker->reply_time = GetCurrentTimestamp();
+
+	/* Load the libpq-specific functions */
+	load_file("libpqwalreceiver", false);
+
+	/* Run as replica session replication role. */
+	SetConfigOption("session_replication_role", "replica",
+					PGC_SUSET, PGC_S_OVERRIDE);
+
+	/* Connect to our database. */
+	BackgroundWorkerInitializeConnectionByOid(MyLogicalRepWorker->dbid,
+											  MyLogicalRepWorker->userid,
+											  0);
+
+	/*
+	 * Set always-secure search path, so malicious users can't redirect user
+	 * code (e.g. pg_index.indexprs).
+	 */
+	SetConfigOption("search_path", "", PGC_SUSET, PGC_S_OVERRIDE);
+
+	/* Load the subscription into persistent memory context. */
+	ApplyContext = AllocSetContextCreate(TopMemoryContext,
+										 "ApplyContext",
+										 ALLOCSET_DEFAULT_SIZES);
+	StartTransactionCommand();
+	oldctx = MemoryContextSwitchTo(ApplyContext);
+
+	MySubscription = GetSubscription(MyLogicalRepWorker->subid, true);
+	if (!MySubscription)
+	{
+		ereport(LOG,
+				(errmsg("logical replication apply worker for subscription %u will not "
+						"start because the subscription was removed during startup",
+						MyLogicalRepWorker->subid)));
+		proc_exit(0);
+	}
+
+	MySubscriptionValid = true;
+	MemoryContextSwitchTo(oldctx);
+
+	if (!MySubscription->enabled)
+	{
+		ereport(LOG,
+				(errmsg("logical replication apply worker for subscription \"%s\" will not "
+						"start because the subscription was disabled during startup",
+						MySubscription->name)));
+
+		proc_exit(0);
+	}
+
+	/* Setup synchronous commit according to the user's wishes */
+	SetConfigOption("synchronous_commit", MySubscription->synccommit,
+					PGC_BACKEND, PGC_S_OVERRIDE);
+
+	/* Keep us informed about subscription changes. */
+	CacheRegisterSyscacheCallback(SUBSCRIPTIONOID,
+								  subscription_change_cb,
+								  (Datum) 0);
+
+	if (am_tablesync_worker())
+		ereport(LOG,
+				(errmsg("logical replication table synchronization worker for subscription \"%s\", table \"%s\" has started",
+						MySubscription->name, get_rel_name(MyLogicalRepWorker->relid))));
+	else
+		ereport(LOG,
+				(errmsg("logical replication apply worker for subscription \"%s\" has started",
+						MySubscription->name)));
+
+	CommitTransactionCommand();
+
+	/* Connect to the origin and start the replication. */
+	elog(DEBUG1, "connecting to publisher using connection string \"%s\"",
+		 MySubscription->conninfo);
+
+	if (am_tablesync_worker())
+	{
+		char	   *syncslotname;
+
+		/* This is table synchronization worker, call initial sync. */
+		syncslotname = LogicalRepSyncTableStart(&origin_startpos);
+
+		/* allocate slot name in long-lived context */
+		myslotname = MemoryContextStrdup(ApplyContext, syncslotname);
+
+		pfree(syncslotname);
+	}
+	else
+	{
+		/* This is main apply worker */
+		RepOriginId originid;
+		TimeLineID	startpointTLI;
+		char	   *err;
+
+		myslotname = MySubscription->slotname;
+
+		/*
+		 * This shouldn't happen if the subscription is enabled, but guard
+		 * against DDL bugs or manual catalog changes.  (libpqwalreceiver will
+		 * crash if slot is NULL.)
+		 */
+		if (!myslotname)
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					 errmsg("subscription has no replication slot set")));
+
+		/* Setup replication origin tracking. */
+		StartTransactionCommand();
+		snprintf(originname, sizeof(originname), "pg_%u", MySubscription->oid);
+		originid = replorigin_by_name(originname, true);
+		if (!OidIsValid(originid))
+			originid = replorigin_create(originname);
+		replorigin_session_setup(originid);
+		replorigin_session_origin = originid;
+		origin_startpos = replorigin_session_get_progress(false);
+		CommitTransactionCommand();
+
+		LogRepWorkerWalRcvConn = walrcv_connect(MySubscription->conninfo, true,
+												MySubscription->name, &err);
+		if (LogRepWorkerWalRcvConn == NULL)
+			ereport(ERROR,
+					(errcode(ERRCODE_CONNECTION_FAILURE),
+					 errmsg("could not connect to the publisher: %s", err)));
+
+		/*
+		 * We don't really use the output identify_system for anything but it
+		 * does some initializations on the upstream so let's still call it.
+		 */
+		(void) walrcv_identify_system(LogRepWorkerWalRcvConn, &startpointTLI);
+	}
+
+	/*
+	 * Setup callback for syscache so that we know when something changes in
+	 * the subscription relation state.
+	 */
+	CacheRegisterSyscacheCallback(SUBSCRIPTIONRELMAP,
+								  invalidate_syncing_table_states,
+								  (Datum) 0);
+
+	/* Build logical replication streaming options. */
+	options.logical = true;
+	options.startpoint = origin_startpos;
+	options.slotname = myslotname;
+	options.proto.logical.proto_version =
+		walrcv_server_version(LogRepWorkerWalRcvConn) >= 140000 ?
+		LOGICALREP_PROTO_STREAM_VERSION_NUM : LOGICALREP_PROTO_VERSION_NUM;
+	options.proto.logical.publication_names = MySubscription->publications;
+	options.proto.logical.binary = MySubscription->binary;
+	options.proto.logical.streaming = MySubscription->stream;
+
+	/* Start normal logical streaming replication. */
+	walrcv_startstreaming(LogRepWorkerWalRcvConn, &options);
+
+	/* Run the main loop. */
+	LogicalRepApplyLoop(origin_startpos);
+
+	proc_exit(0);
+}
+
+/*
+ * Is current process a logical replication worker?
+ */
+bool
+IsLogicalWorker(void)
+{
+	return MyLogicalRepWorker != NULL;
+}
diff --git a/src/backend/replication/pgoutput/Makefile b/src/backend/replication/pgoutput/Makefile
new file mode 100644
index 0000000..3b41fbc
--- /dev/null
+++ b/src/backend/replication/pgoutput/Makefile
@@ -0,0 +1,32 @@
+#-------------------------------------------------------------------------
+#
+# Makefile--
+#    Makefile for src/backend/replication/pgoutput
+#
+# IDENTIFICATION
+#    src/backend/replication/pgoutput
+#
+#-------------------------------------------------------------------------
+
+subdir = src/backend/replication/pgoutput
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+
+OBJS = \
+	$(WIN32RES) \
+	pgoutput.o
+PGFILEDESC = "pgoutput - standard logical replication output plugin"
+NAME = pgoutput
+
+all: all-shared-lib
+
+include $(top_srcdir)/src/Makefile.shlib
+
+install: all installdirs install-lib
+
+installdirs: installdirs-lib
+
+uninstall: uninstall-lib
+
+clean distclean maintainer-clean: clean-lib
+	rm -f $(OBJS)
diff --git a/src/backend/replication/pgoutput/pgoutput.c b/src/backend/replication/pgoutput/pgoutput.c
new file mode 100644
index 0000000..ff9cf5d
--- /dev/null
+++ b/src/backend/replication/pgoutput/pgoutput.c
@@ -0,0 +1,1346 @@
+/*-------------------------------------------------------------------------
+ *
+ * pgoutput.c
+ *		Logical Replication output plugin
+ *
+ * Copyright (c) 2012-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *		  src/backend/replication/pgoutput/pgoutput.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/tupconvert.h"
+#include "catalog/partition.h"
+#include "catalog/pg_publication.h"
+#include "commands/defrem.h"
+#include "fmgr.h"
+#include "replication/logical.h"
+#include "replication/logicalproto.h"
+#include "replication/origin.h"
+#include "replication/pgoutput.h"
+#include "utils/int8.h"
+#include "utils/inval.h"
+#include "utils/lsyscache.h"
+#include "utils/memutils.h"
+#include "utils/syscache.h"
+#include "utils/varlena.h"
+
+PG_MODULE_MAGIC;
+
+extern void _PG_output_plugin_init(OutputPluginCallbacks *cb);
+
+static void pgoutput_startup(LogicalDecodingContext *ctx,
+							 OutputPluginOptions *opt, bool is_init);
+static void pgoutput_shutdown(LogicalDecodingContext *ctx);
+static void pgoutput_begin_txn(LogicalDecodingContext *ctx,
+							   ReorderBufferTXN *txn);
+static void pgoutput_commit_txn(LogicalDecodingContext *ctx,
+								ReorderBufferTXN *txn, XLogRecPtr commit_lsn);
+static void pgoutput_change(LogicalDecodingContext *ctx,
+							ReorderBufferTXN *txn, Relation rel,
+							ReorderBufferChange *change);
+static void pgoutput_truncate(LogicalDecodingContext *ctx,
+							  ReorderBufferTXN *txn, int nrelations, Relation relations[],
+							  ReorderBufferChange *change);
+static void pgoutput_message(LogicalDecodingContext *ctx,
+							 ReorderBufferTXN *txn, XLogRecPtr message_lsn,
+							 bool transactional, const char *prefix,
+							 Size sz, const char *message);
+static bool pgoutput_origin_filter(LogicalDecodingContext *ctx,
+								   RepOriginId origin_id);
+static void pgoutput_stream_start(struct LogicalDecodingContext *ctx,
+								  ReorderBufferTXN *txn);
+static void pgoutput_stream_stop(struct LogicalDecodingContext *ctx,
+								 ReorderBufferTXN *txn);
+static void pgoutput_stream_abort(struct LogicalDecodingContext *ctx,
+								  ReorderBufferTXN *txn,
+								  XLogRecPtr abort_lsn);
+static void pgoutput_stream_commit(struct LogicalDecodingContext *ctx,
+								   ReorderBufferTXN *txn,
+								   XLogRecPtr commit_lsn);
+
+static bool publications_valid;
+static bool in_streaming;
+
+static List *LoadPublications(List *pubnames);
+static void publication_invalidation_cb(Datum arg, int cacheid,
+										uint32 hashvalue);
+static void send_relation_and_attrs(Relation relation, TransactionId xid,
+									LogicalDecodingContext *ctx);
+static void update_replication_progress(LogicalDecodingContext *ctx);
+
+/*
+ * Entry in the map used to remember which relation schemas we sent.
+ *
+ * The schema_sent flag determines if the current schema record for the
+ * relation (and for its ancestor if publish_as_relid is set) was already
+ * sent to the subscriber (in which case we don't need to send it again).
+ *
+ * The schema cache on downstream is however updated only at commit time,
+ * and with streamed transactions the commit order may be different from
+ * the order the transactions are sent in. Also, the (sub) transactions
+ * might get aborted so we need to send the schema for each (sub) transaction
+ * so that we don't lose the schema information on abort. For handling this,
+ * we maintain the list of xids (streamed_txns) for those we have already sent
+ * the schema.
+ *
+ * For partitions, 'pubactions' considers not only the table's own
+ * publications, but also those of all of its ancestors.
+ */
+typedef struct RelationSyncEntry
+{
+	Oid			relid;			/* relation oid */
+
+	bool		schema_sent;
+	List	   *streamed_txns;	/* streamed toplevel transactions with this
+								 * schema */
+
+	bool		replicate_valid;
+	PublicationActions pubactions;
+
+	/*
+	 * OID of the relation to publish changes as.  For a partition, this may
+	 * be set to one of its ancestors whose schema will be used when
+	 * replicating changes, if publish_via_partition_root is set for the
+	 * publication.
+	 */
+	Oid			publish_as_relid;
+
+	/*
+	 * Map used when replicating using an ancestor's schema to convert tuples
+	 * from partition's type to the ancestor's; NULL if publish_as_relid is
+	 * same as 'relid' or if unnecessary due to partition and the ancestor
+	 * having identical TupleDesc.
+	 */
+	TupleConversionMap *map;
+} RelationSyncEntry;
+
+/* Map used to remember which relation schemas we sent. */
+static HTAB *RelationSyncCache = NULL;
+
+static void init_rel_sync_cache(MemoryContext decoding_context);
+static void cleanup_rel_sync_cache(TransactionId xid, bool is_commit);
+static RelationSyncEntry *get_rel_sync_entry(PGOutputData *data, Oid relid);
+static void rel_sync_cache_relation_cb(Datum arg, Oid relid);
+static void rel_sync_cache_publication_cb(Datum arg, int cacheid,
+										  uint32 hashvalue);
+static void set_schema_sent_in_streamed_txn(RelationSyncEntry *entry,
+											TransactionId xid);
+static bool get_schema_sent_in_streamed_txn(RelationSyncEntry *entry,
+											TransactionId xid);
+
+/*
+ * Specify output plugin callbacks
+ */
+void
+_PG_output_plugin_init(OutputPluginCallbacks *cb)
+{
+	AssertVariableIsOfType(&_PG_output_plugin_init, LogicalOutputPluginInit);
+
+	cb->startup_cb = pgoutput_startup;
+	cb->begin_cb = pgoutput_begin_txn;
+	cb->change_cb = pgoutput_change;
+	cb->truncate_cb = pgoutput_truncate;
+	cb->message_cb = pgoutput_message;
+	cb->commit_cb = pgoutput_commit_txn;
+	cb->filter_by_origin_cb = pgoutput_origin_filter;
+	cb->shutdown_cb = pgoutput_shutdown;
+
+	/* transaction streaming */
+	cb->stream_start_cb = pgoutput_stream_start;
+	cb->stream_stop_cb = pgoutput_stream_stop;
+	cb->stream_abort_cb = pgoutput_stream_abort;
+	cb->stream_commit_cb = pgoutput_stream_commit;
+	cb->stream_change_cb = pgoutput_change;
+	cb->stream_message_cb = pgoutput_message;
+	cb->stream_truncate_cb = pgoutput_truncate;
+}
+
+static void
+parse_output_parameters(List *options, PGOutputData *data)
+{
+	ListCell   *lc;
+	bool		protocol_version_given = false;
+	bool		publication_names_given = false;
+	bool		binary_option_given = false;
+	bool		messages_option_given = false;
+	bool		streaming_given = false;
+
+	data->binary = false;
+	data->streaming = false;
+	data->messages = false;
+
+	foreach(lc, options)
+	{
+		DefElem    *defel = (DefElem *) lfirst(lc);
+
+		Assert(defel->arg == NULL || IsA(defel->arg, String));
+
+		/* Check each param, whether or not we recognize it */
+		if (strcmp(defel->defname, "proto_version") == 0)
+		{
+			int64		parsed;
+
+			if (protocol_version_given)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options")));
+			protocol_version_given = true;
+
+			if (!scanint8(strVal(defel->arg), true, &parsed))
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("invalid proto_version")));
+
+			if (parsed > PG_UINT32_MAX || parsed < 0)
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("proto_version \"%s\" out of range",
+								strVal(defel->arg))));
+
+			data->protocol_version = (uint32) parsed;
+		}
+		else if (strcmp(defel->defname, "publication_names") == 0)
+		{
+			if (publication_names_given)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options")));
+			publication_names_given = true;
+
+			if (!SplitIdentifierString(strVal(defel->arg), ',',
+									   &data->publication_names))
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_NAME),
+						 errmsg("invalid publication_names syntax")));
+		}
+		else if (strcmp(defel->defname, "binary") == 0)
+		{
+			if (binary_option_given)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options")));
+			binary_option_given = true;
+
+			data->binary = defGetBoolean(defel);
+		}
+		else if (strcmp(defel->defname, "messages") == 0)
+		{
+			if (messages_option_given)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options")));
+			messages_option_given = true;
+
+			data->messages = defGetBoolean(defel);
+		}
+		else if (strcmp(defel->defname, "streaming") == 0)
+		{
+			if (streaming_given)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options")));
+			streaming_given = true;
+
+			data->streaming = defGetBoolean(defel);
+		}
+		else
+			elog(ERROR, "unrecognized pgoutput option: %s", defel->defname);
+	}
+}
+
+/*
+ * Initialize this plugin
+ */
+static void
+pgoutput_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
+				 bool is_init)
+{
+	PGOutputData *data = palloc0(sizeof(PGOutputData));
+
+	/* Create our memory context for private allocations. */
+	data->context = AllocSetContextCreate(ctx->context,
+										  "logical replication output context",
+										  ALLOCSET_DEFAULT_SIZES);
+
+	ctx->output_plugin_private = data;
+
+	/* This plugin uses binary protocol. */
+	opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT;
+
+	/*
+	 * This is replication start and not slot initialization.
+	 *
+	 * Parse and validate options passed by the client.
+	 */
+	if (!is_init)
+	{
+		/* Parse the params and ERROR if we see any we don't recognize */
+		parse_output_parameters(ctx->output_plugin_options, data);
+
+		/* Check if we support requested protocol */
+		if (data->protocol_version > LOGICALREP_PROTO_MAX_VERSION_NUM)
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("client sent proto_version=%d but we only support protocol %d or lower",
+							data->protocol_version, LOGICALREP_PROTO_MAX_VERSION_NUM)));
+
+		if (data->protocol_version < LOGICALREP_PROTO_MIN_VERSION_NUM)
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("client sent proto_version=%d but we only support protocol %d or higher",
+							data->protocol_version, LOGICALREP_PROTO_MIN_VERSION_NUM)));
+
+		if (list_length(data->publication_names) < 1)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("publication_names parameter missing")));
+
+		/*
+		 * Decide whether to enable streaming. It is disabled by default, in
+		 * which case we just update the flag in decoding context. Otherwise
+		 * we only allow it with sufficient version of the protocol, and when
+		 * the output plugin supports it.
+		 */
+		if (!data->streaming)
+			ctx->streaming = false;
+		else if (data->protocol_version < LOGICALREP_PROTO_STREAM_VERSION_NUM)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("requested proto_version=%d does not support streaming, need %d or higher",
+							data->protocol_version, LOGICALREP_PROTO_STREAM_VERSION_NUM)));
+		else if (!ctx->streaming)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("streaming requested, but not supported by output plugin")));
+
+		/* Also remember we're currently not streaming any transaction. */
+		in_streaming = false;
+
+		/* Init publication state. */
+		data->publications = NIL;
+		publications_valid = false;
+		CacheRegisterSyscacheCallback(PUBLICATIONOID,
+									  publication_invalidation_cb,
+									  (Datum) 0);
+
+		/* Initialize relation schema cache. */
+		init_rel_sync_cache(CacheMemoryContext);
+	}
+	else
+	{
+		/* Disable the streaming during the slot initialization mode. */
+		ctx->streaming = false;
+	}
+}
+
+/*
+ * BEGIN callback
+ */
+static void
+pgoutput_begin_txn(LogicalDecodingContext *ctx, ReorderBufferTXN *txn)
+{
+	bool		send_replication_origin = txn->origin_id != InvalidRepOriginId;
+
+	OutputPluginPrepareWrite(ctx, !send_replication_origin);
+	logicalrep_write_begin(ctx->out, txn);
+
+	if (send_replication_origin)
+	{
+		char	   *origin;
+
+		/*----------
+		 * XXX: which behaviour do we want here?
+		 *
+		 * Alternatives:
+		 *	- don't send origin message if origin name not found
+		 *	  (that's what we do now)
+		 *	- throw error - that will break replication, not good
+		 *	- send some special "unknown" origin
+		 *----------
+		 */
+		if (replorigin_by_oid(txn->origin_id, true, &origin))
+		{
+			/* Message boundary */
+			OutputPluginWrite(ctx, false);
+			OutputPluginPrepareWrite(ctx, true);
+			logicalrep_write_origin(ctx->out, origin, txn->origin_lsn);
+		}
+
+	}
+
+	OutputPluginWrite(ctx, true);
+}
+
+/*
+ * COMMIT callback
+ */
+static void
+pgoutput_commit_txn(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
+					XLogRecPtr commit_lsn)
+{
+	update_replication_progress(ctx);
+
+	OutputPluginPrepareWrite(ctx, true);
+	logicalrep_write_commit(ctx->out, txn, commit_lsn);
+	OutputPluginWrite(ctx, true);
+}
+
+/*
+ * Write the current schema of the relation and its ancestor (if any) if not
+ * done yet.
+ */
+static void
+maybe_send_schema(LogicalDecodingContext *ctx,
+				  ReorderBufferTXN *txn, ReorderBufferChange *change,
+				  Relation relation, RelationSyncEntry *relentry)
+{
+	bool		schema_sent;
+	TransactionId xid = InvalidTransactionId;
+	TransactionId topxid = InvalidTransactionId;
+
+	/*
+	 * Remember XID of the (sub)transaction for the change. We don't care if
+	 * it's top-level transaction or not (we have already sent that XID in
+	 * start of the current streaming block).
+	 *
+	 * If we're not in a streaming block, just use InvalidTransactionId and
+	 * the write methods will not include it.
+	 */
+	if (in_streaming)
+		xid = change->txn->xid;
+
+	if (change->txn->toptxn)
+		topxid = change->txn->toptxn->xid;
+	else
+		topxid = xid;
+
+	/*
+	 * Do we need to send the schema? We do track streamed transactions
+	 * separately, because those may be applied later (and the regular
+	 * transactions won't see their effects until then) and in an order that
+	 * we don't know at this point.
+	 *
+	 * XXX There is a scope of optimization here. Currently, we always send
+	 * the schema first time in a streaming transaction but we can probably
+	 * avoid that by checking 'relentry->schema_sent' flag. However, before
+	 * doing that we need to study its impact on the case where we have a mix
+	 * of streaming and non-streaming transactions.
+	 */
+	if (in_streaming)
+		schema_sent = get_schema_sent_in_streamed_txn(relentry, topxid);
+	else
+		schema_sent = relentry->schema_sent;
+
+	/* Nothing to do if we already sent the schema. */
+	if (schema_sent)
+		return;
+
+	/*
+	 * Nope, so send the schema.  If the changes will be published using an
+	 * ancestor's schema, not the relation's own, send that ancestor's schema
+	 * before sending relation's own (XXX - maybe sending only the former
+	 * suffices?).  This is also a good place to set the map that will be used
+	 * to convert the relation's tuples into the ancestor's format, if needed.
+	 */
+	if (relentry->publish_as_relid != RelationGetRelid(relation))
+	{
+		Relation	ancestor = RelationIdGetRelation(relentry->publish_as_relid);
+		TupleDesc	indesc = RelationGetDescr(relation);
+		TupleDesc	outdesc = RelationGetDescr(ancestor);
+		MemoryContext oldctx;
+
+		/* Map must live as long as the session does. */
+		oldctx = MemoryContextSwitchTo(CacheMemoryContext);
+
+		/*
+		 * Make copies of the TupleDescs that will live as long as the map
+		 * does before putting into the map.
+		 */
+		indesc = CreateTupleDescCopy(indesc);
+		outdesc = CreateTupleDescCopy(outdesc);
+		relentry->map = convert_tuples_by_name(indesc, outdesc);
+		if (relentry->map == NULL)
+		{
+			/* Map not necessary, so free the TupleDescs too. */
+			FreeTupleDesc(indesc);
+			FreeTupleDesc(outdesc);
+		}
+
+		MemoryContextSwitchTo(oldctx);
+		send_relation_and_attrs(ancestor, xid, ctx);
+		RelationClose(ancestor);
+	}
+
+	send_relation_and_attrs(relation, xid, ctx);
+
+	if (in_streaming)
+		set_schema_sent_in_streamed_txn(relentry, topxid);
+	else
+		relentry->schema_sent = true;
+}
+
+/*
+ * Sends a relation
+ */
+static void
+send_relation_and_attrs(Relation relation, TransactionId xid,
+						LogicalDecodingContext *ctx)
+{
+	TupleDesc	desc = RelationGetDescr(relation);
+	int			i;
+
+	/*
+	 * Write out type info if needed.  We do that only for user-created types.
+	 * We use FirstGenbkiObjectId as the cutoff, so that we only consider
+	 * objects with hand-assigned OIDs to be "built in", not for instance any
+	 * function or type defined in the information_schema. This is important
+	 * because only hand-assigned OIDs can be expected to remain stable across
+	 * major versions.
+	 */
+	for (i = 0; i < desc->natts; i++)
+	{
+		Form_pg_attribute att = TupleDescAttr(desc, i);
+
+		if (att->attisdropped || att->attgenerated)
+			continue;
+
+		if (att->atttypid < FirstGenbkiObjectId)
+			continue;
+
+		OutputPluginPrepareWrite(ctx, false);
+		logicalrep_write_typ(ctx->out, xid, att->atttypid);
+		OutputPluginWrite(ctx, false);
+	}
+
+	OutputPluginPrepareWrite(ctx, false);
+	logicalrep_write_rel(ctx->out, xid, relation);
+	OutputPluginWrite(ctx, false);
+}
+
+/*
+ * Sends the decoded DML over wire.
+ *
+ * This is called both in streaming and non-streaming modes.
+ */
+static void
+pgoutput_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
+				Relation relation, ReorderBufferChange *change)
+{
+	PGOutputData *data = (PGOutputData *) ctx->output_plugin_private;
+	MemoryContext old;
+	RelationSyncEntry *relentry;
+	TransactionId xid = InvalidTransactionId;
+	Relation	ancestor = NULL;
+
+	update_replication_progress(ctx);
+
+	if (!is_publishable_relation(relation))
+		return;
+
+	/*
+	 * Remember the xid for the change in streaming mode. We need to send xid
+	 * with each change in the streaming mode so that subscriber can make
+	 * their association and on aborts, it can discard the corresponding
+	 * changes.
+	 */
+	if (in_streaming)
+		xid = change->txn->xid;
+
+	relentry = get_rel_sync_entry(data, RelationGetRelid(relation));
+
+	/* First check the table filter */
+	switch (change->action)
+	{
+		case REORDER_BUFFER_CHANGE_INSERT:
+			if (!relentry->pubactions.pubinsert)
+				return;
+			break;
+		case REORDER_BUFFER_CHANGE_UPDATE:
+			if (!relentry->pubactions.pubupdate)
+				return;
+			break;
+		case REORDER_BUFFER_CHANGE_DELETE:
+			if (!relentry->pubactions.pubdelete)
+				return;
+			break;
+		default:
+			Assert(false);
+	}
+
+	/* Avoid leaking memory by using and resetting our own context */
+	old = MemoryContextSwitchTo(data->context);
+
+	maybe_send_schema(ctx, txn, change, relation, relentry);
+
+	/* Send the data */
+	switch (change->action)
+	{
+		case REORDER_BUFFER_CHANGE_INSERT:
+			{
+				HeapTuple	tuple = &change->data.tp.newtuple->tuple;
+
+				/* Switch relation if publishing via root. */
+				if (relentry->publish_as_relid != RelationGetRelid(relation))
+				{
+					Assert(relation->rd_rel->relispartition);
+					ancestor = RelationIdGetRelation(relentry->publish_as_relid);
+					relation = ancestor;
+					/* Convert tuple if needed. */
+					if (relentry->map)
+						tuple = execute_attr_map_tuple(tuple, relentry->map);
+				}
+
+				OutputPluginPrepareWrite(ctx, true);
+				logicalrep_write_insert(ctx->out, xid, relation, tuple,
+										data->binary);
+				OutputPluginWrite(ctx, true);
+				break;
+			}
+		case REORDER_BUFFER_CHANGE_UPDATE:
+			{
+				HeapTuple	oldtuple = change->data.tp.oldtuple ?
+				&change->data.tp.oldtuple->tuple : NULL;
+				HeapTuple	newtuple = &change->data.tp.newtuple->tuple;
+
+				/* Switch relation if publishing via root. */
+				if (relentry->publish_as_relid != RelationGetRelid(relation))
+				{
+					Assert(relation->rd_rel->relispartition);
+					ancestor = RelationIdGetRelation(relentry->publish_as_relid);
+					relation = ancestor;
+					/* Convert tuples if needed. */
+					if (relentry->map)
+					{
+						if (oldtuple)
+							oldtuple = execute_attr_map_tuple(oldtuple,
+															  relentry->map);
+						newtuple = execute_attr_map_tuple(newtuple,
+														  relentry->map);
+					}
+				}
+
+				OutputPluginPrepareWrite(ctx, true);
+				logicalrep_write_update(ctx->out, xid, relation, oldtuple,
+										newtuple, data->binary);
+				OutputPluginWrite(ctx, true);
+				break;
+			}
+		case REORDER_BUFFER_CHANGE_DELETE:
+			if (change->data.tp.oldtuple)
+			{
+				HeapTuple	oldtuple = &change->data.tp.oldtuple->tuple;
+
+				/* Switch relation if publishing via root. */
+				if (relentry->publish_as_relid != RelationGetRelid(relation))
+				{
+					Assert(relation->rd_rel->relispartition);
+					ancestor = RelationIdGetRelation(relentry->publish_as_relid);
+					relation = ancestor;
+					/* Convert tuple if needed. */
+					if (relentry->map)
+						oldtuple = execute_attr_map_tuple(oldtuple, relentry->map);
+				}
+
+				OutputPluginPrepareWrite(ctx, true);
+				logicalrep_write_delete(ctx->out, xid, relation, oldtuple,
+										data->binary);
+				OutputPluginWrite(ctx, true);
+			}
+			else
+				elog(DEBUG1, "didn't send DELETE change because of missing oldtuple");
+			break;
+		default:
+			Assert(false);
+	}
+
+	if (RelationIsValid(ancestor))
+	{
+		RelationClose(ancestor);
+		ancestor = NULL;
+	}
+
+	/* Cleanup */
+	MemoryContextSwitchTo(old);
+	MemoryContextReset(data->context);
+}
+
+static void
+pgoutput_truncate(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
+				  int nrelations, Relation relations[], ReorderBufferChange *change)
+{
+	PGOutputData *data = (PGOutputData *) ctx->output_plugin_private;
+	MemoryContext old;
+	RelationSyncEntry *relentry;
+	int			i;
+	int			nrelids;
+	Oid		   *relids;
+	TransactionId xid = InvalidTransactionId;
+
+	update_replication_progress(ctx);
+
+	/* Remember the xid for the change in streaming mode. See pgoutput_change. */
+	if (in_streaming)
+		xid = change->txn->xid;
+
+	old = MemoryContextSwitchTo(data->context);
+
+	relids = palloc0(nrelations * sizeof(Oid));
+	nrelids = 0;
+
+	for (i = 0; i < nrelations; i++)
+	{
+		Relation	relation = relations[i];
+		Oid			relid = RelationGetRelid(relation);
+
+		if (!is_publishable_relation(relation))
+			continue;
+
+		relentry = get_rel_sync_entry(data, relid);
+
+		if (!relentry->pubactions.pubtruncate)
+			continue;
+
+		/*
+		 * Don't send partitions if the publication wants to send only the
+		 * root tables through it.
+		 */
+		if (relation->rd_rel->relispartition &&
+			relentry->publish_as_relid != relid)
+			continue;
+
+		relids[nrelids++] = relid;
+		maybe_send_schema(ctx, txn, change, relation, relentry);
+	}
+
+	if (nrelids > 0)
+	{
+		OutputPluginPrepareWrite(ctx, true);
+		logicalrep_write_truncate(ctx->out,
+								  xid,
+								  nrelids,
+								  relids,
+								  change->data.truncate.cascade,
+								  change->data.truncate.restart_seqs);
+		OutputPluginWrite(ctx, true);
+	}
+
+	MemoryContextSwitchTo(old);
+	MemoryContextReset(data->context);
+}
+
+static void
+pgoutput_message(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
+				 XLogRecPtr message_lsn, bool transactional, const char *prefix, Size sz,
+				 const char *message)
+{
+	PGOutputData *data = (PGOutputData *) ctx->output_plugin_private;
+	TransactionId xid = InvalidTransactionId;
+
+	update_replication_progress(ctx);
+
+	if (!data->messages)
+		return;
+
+	/*
+	 * Remember the xid for the message in streaming mode. See
+	 * pgoutput_change.
+	 */
+	if (in_streaming)
+		xid = txn->xid;
+
+	OutputPluginPrepareWrite(ctx, true);
+	logicalrep_write_message(ctx->out,
+							 xid,
+							 message_lsn,
+							 transactional,
+							 prefix,
+							 sz,
+							 message);
+	OutputPluginWrite(ctx, true);
+}
+
+/*
+ * Currently we always forward.
+ */
+static bool
+pgoutput_origin_filter(LogicalDecodingContext *ctx,
+					   RepOriginId origin_id)
+{
+	return false;
+}
+
+/*
+ * Shutdown the output plugin.
+ *
+ * Note, we don't need to clean the data->context as it's child context
+ * of the ctx->context so it will be cleaned up by logical decoding machinery.
+ */
+static void
+pgoutput_shutdown(LogicalDecodingContext *ctx)
+{
+	if (RelationSyncCache)
+	{
+		hash_destroy(RelationSyncCache);
+		RelationSyncCache = NULL;
+	}
+}
+
+/*
+ * Load publications from the list of publication names.
+ */
+static List *
+LoadPublications(List *pubnames)
+{
+	List	   *result = NIL;
+	ListCell   *lc;
+
+	foreach(lc, pubnames)
+	{
+		char	   *pubname = (char *) lfirst(lc);
+		Publication *pub = GetPublicationByName(pubname, false);
+
+		result = lappend(result, pub);
+	}
+
+	return result;
+}
+
+/*
+ * Publication cache invalidation callback.
+ */
+static void
+publication_invalidation_cb(Datum arg, int cacheid, uint32 hashvalue)
+{
+	publications_valid = false;
+
+	/*
+	 * Also invalidate per-relation cache so that next time the filtering info
+	 * is checked it will be updated with the new publication settings.
+	 */
+	rel_sync_cache_publication_cb(arg, cacheid, hashvalue);
+}
+
+/*
+ * START STREAM callback
+ */
+static void
+pgoutput_stream_start(struct LogicalDecodingContext *ctx,
+					  ReorderBufferTXN *txn)
+{
+	bool		send_replication_origin = txn->origin_id != InvalidRepOriginId;
+
+	/* we can't nest streaming of transactions */
+	Assert(!in_streaming);
+
+	/*
+	 * If we already sent the first stream for this transaction then don't
+	 * send the origin id in the subsequent streams.
+	 */
+	if (rbtxn_is_streamed(txn))
+		send_replication_origin = false;
+
+	OutputPluginPrepareWrite(ctx, !send_replication_origin);
+	logicalrep_write_stream_start(ctx->out, txn->xid, !rbtxn_is_streamed(txn));
+
+	if (send_replication_origin)
+	{
+		char	   *origin;
+
+		if (replorigin_by_oid(txn->origin_id, true, &origin))
+		{
+			/* Message boundary */
+			OutputPluginWrite(ctx, false);
+			OutputPluginPrepareWrite(ctx, true);
+			logicalrep_write_origin(ctx->out, origin, InvalidXLogRecPtr);
+		}
+	}
+
+	OutputPluginWrite(ctx, true);
+
+	/* we're streaming a chunk of transaction now */
+	in_streaming = true;
+}
+
+/*
+ * STOP STREAM callback
+ */
+static void
+pgoutput_stream_stop(struct LogicalDecodingContext *ctx,
+					 ReorderBufferTXN *txn)
+{
+	/* we should be streaming a trasanction */
+	Assert(in_streaming);
+
+	OutputPluginPrepareWrite(ctx, true);
+	logicalrep_write_stream_stop(ctx->out);
+	OutputPluginWrite(ctx, true);
+
+	/* we've stopped streaming a transaction */
+	in_streaming = false;
+}
+
+/*
+ * Notify downstream to discard the streamed transaction (along with all
+ * it's subtransactions, if it's a toplevel transaction).
+ */
+static void
+pgoutput_stream_abort(struct LogicalDecodingContext *ctx,
+					  ReorderBufferTXN *txn,
+					  XLogRecPtr abort_lsn)
+{
+	ReorderBufferTXN *toptxn;
+
+	/*
+	 * The abort should happen outside streaming block, even for streamed
+	 * transactions. The transaction has to be marked as streamed, though.
+	 */
+	Assert(!in_streaming);
+
+	/* determine the toplevel transaction */
+	toptxn = (txn->toptxn) ? txn->toptxn : txn;
+
+	Assert(rbtxn_is_streamed(toptxn));
+
+	OutputPluginPrepareWrite(ctx, true);
+	logicalrep_write_stream_abort(ctx->out, toptxn->xid, txn->xid);
+	OutputPluginWrite(ctx, true);
+
+	cleanup_rel_sync_cache(toptxn->xid, false);
+}
+
+/*
+ * Notify downstream to apply the streamed transaction (along with all
+ * it's subtransactions).
+ */
+static void
+pgoutput_stream_commit(struct LogicalDecodingContext *ctx,
+					   ReorderBufferTXN *txn,
+					   XLogRecPtr commit_lsn)
+{
+	/*
+	 * The commit should happen outside streaming block, even for streamed
+	 * transactions. The transaction has to be marked as streamed, though.
+	 */
+	Assert(!in_streaming);
+	Assert(rbtxn_is_streamed(txn));
+
+	update_replication_progress(ctx);
+
+	OutputPluginPrepareWrite(ctx, true);
+	logicalrep_write_stream_commit(ctx->out, txn, commit_lsn);
+	OutputPluginWrite(ctx, true);
+
+	cleanup_rel_sync_cache(txn->xid, true);
+}
+
+/*
+ * Initialize the relation schema sync cache for a decoding session.
+ *
+ * The hash table is destroyed at the end of a decoding session. While
+ * relcache invalidations still exist and will still be invoked, they
+ * will just see the null hash table global and take no action.
+ */
+static void
+init_rel_sync_cache(MemoryContext cachectx)
+{
+	HASHCTL		ctl;
+
+	if (RelationSyncCache != NULL)
+		return;
+
+	/* Make a new hash table for the cache */
+	ctl.keysize = sizeof(Oid);
+	ctl.entrysize = sizeof(RelationSyncEntry);
+	ctl.hcxt = cachectx;
+
+	RelationSyncCache = hash_create("logical replication output relation cache",
+									128, &ctl,
+									HASH_ELEM | HASH_CONTEXT | HASH_BLOBS);
+
+	Assert(RelationSyncCache != NULL);
+
+	CacheRegisterRelcacheCallback(rel_sync_cache_relation_cb, (Datum) 0);
+	CacheRegisterSyscacheCallback(PUBLICATIONRELMAP,
+								  rel_sync_cache_publication_cb,
+								  (Datum) 0);
+}
+
+/*
+ * We expect relatively small number of streamed transactions.
+ */
+static bool
+get_schema_sent_in_streamed_txn(RelationSyncEntry *entry, TransactionId xid)
+{
+	ListCell   *lc;
+
+	foreach(lc, entry->streamed_txns)
+	{
+		if (xid == (uint32) lfirst_int(lc))
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * Add the xid in the rel sync entry for which we have already sent the schema
+ * of the relation.
+ */
+static void
+set_schema_sent_in_streamed_txn(RelationSyncEntry *entry, TransactionId xid)
+{
+	MemoryContext oldctx;
+
+	oldctx = MemoryContextSwitchTo(CacheMemoryContext);
+
+	entry->streamed_txns = lappend_int(entry->streamed_txns, xid);
+
+	MemoryContextSwitchTo(oldctx);
+}
+
+/*
+ * Find or create entry in the relation schema cache.
+ *
+ * This looks up publications that the given relation is directly or
+ * indirectly part of (the latter if it's really the relation's ancestor that
+ * is part of a publication) and fills up the found entry with the information
+ * about which operations to publish and whether to use an ancestor's schema
+ * when publishing.
+ */
+static RelationSyncEntry *
+get_rel_sync_entry(PGOutputData *data, Oid relid)
+{
+	RelationSyncEntry *entry;
+	bool		found;
+	MemoryContext oldctx;
+
+	Assert(RelationSyncCache != NULL);
+
+	/* Find cached relation info, creating if not found */
+	entry = (RelationSyncEntry *) hash_search(RelationSyncCache,
+											  (void *) &relid,
+											  HASH_ENTER, &found);
+	Assert(entry != NULL);
+
+	/* Not found means schema wasn't sent */
+	if (!found)
+	{
+		/* immediately make a new entry valid enough to satisfy callbacks */
+		entry->schema_sent = false;
+		entry->streamed_txns = NIL;
+		entry->replicate_valid = false;
+		entry->pubactions.pubinsert = entry->pubactions.pubupdate =
+			entry->pubactions.pubdelete = entry->pubactions.pubtruncate = false;
+		entry->publish_as_relid = InvalidOid;
+		entry->map = NULL;		/* will be set by maybe_send_schema() if
+								 * needed */
+	}
+
+	/* Validate the entry */
+	if (!entry->replicate_valid)
+	{
+		List	   *pubids = GetRelationPublications(relid);
+		ListCell   *lc;
+		Oid			publish_as_relid = relid;
+		int			publish_ancestor_level = 0;
+		bool		am_partition = get_rel_relispartition(relid);
+		char		relkind = get_rel_relkind(relid);
+
+		/* Reload publications if needed before use. */
+		if (!publications_valid)
+		{
+			oldctx = MemoryContextSwitchTo(CacheMemoryContext);
+			if (data->publications)
+				list_free_deep(data->publications);
+
+			data->publications = LoadPublications(data->publication_names);
+			MemoryContextSwitchTo(oldctx);
+			publications_valid = true;
+		}
+
+		/*
+		 * Build publication cache. We can't use one provided by relcache as
+		 * relcache considers all publications given relation is in, but here
+		 * we only need to consider ones that the subscriber requested.
+		 */
+		foreach(lc, data->publications)
+		{
+			Publication *pub = lfirst(lc);
+			bool		publish = false;
+
+			/*
+			 * Under what relid should we publish changes in this publication?
+			 * We'll use the top-most relid across all publications. Also track
+			 * the ancestor level for this publication.
+			 */
+			Oid			pub_relid = relid;
+			int			ancestor_level = 0;
+
+			/*
+			 * If this is a FOR ALL TABLES publication, pick the partition root
+			 * and set the ancestor level accordingly.
+			 */
+			if (pub->alltables)
+			{
+				publish = true;
+				if (pub->pubviaroot && am_partition)
+				{
+					List	   *ancestors = get_partition_ancestors(relid);
+
+					pub_relid = llast_oid(ancestors);
+					ancestor_level = list_length(ancestors);
+				}
+			}
+
+			if (!publish)
+			{
+				bool		ancestor_published = false;
+
+				/*
+				 * For a partition, check if any of the ancestors are
+				 * published.  If so, note down the topmost ancestor that is
+				 * published via this publication, which will be used as the
+				 * relation via which to publish the partition's changes.
+				 */
+				if (am_partition)
+				{
+					List	   *ancestors = get_partition_ancestors(relid);
+					ListCell   *lc2;
+					int			level = 0;
+
+					/*
+					 * Find the "topmost" ancestor that is in this
+					 * publication.
+					 */
+					foreach(lc2, ancestors)
+					{
+						Oid			ancestor = lfirst_oid(lc2);
+
+						level++;
+
+						if (list_member_oid(GetRelationPublications(ancestor),
+											pub->oid))
+						{
+							ancestor_published = true;
+							if (pub->pubviaroot)
+							{
+								pub_relid = ancestor;
+								ancestor_level = level;
+							}
+						}
+					}
+				}
+
+				if (list_member_oid(pubids, pub->oid) || ancestor_published)
+					publish = true;
+			}
+
+			/*
+			 * Don't publish changes for partitioned tables, because
+			 * publishing those of its partitions suffices, unless partition
+			 * changes won't be published due to pubviaroot being set.
+			 */
+			if (publish &&
+				(relkind != RELKIND_PARTITIONED_TABLE || pub->pubviaroot))
+			{
+				entry->pubactions.pubinsert |= pub->pubactions.pubinsert;
+				entry->pubactions.pubupdate |= pub->pubactions.pubupdate;
+				entry->pubactions.pubdelete |= pub->pubactions.pubdelete;
+				entry->pubactions.pubtruncate |= pub->pubactions.pubtruncate;
+
+				/*
+				 * We want to publish the changes as the top-most ancestor
+				 * across all publications. So we need to check if the
+				 * already calculated level is higher than the new one. If
+				 * yes, we can ignore the new value (as it's a child).
+				 * Otherwise the new value is an ancestor, so we keep it.
+				 */
+				if (publish_ancestor_level > ancestor_level)
+					continue;
+
+				/* The new value is an ancestor, so let's keep it. */
+				publish_as_relid = pub_relid;
+				publish_ancestor_level = ancestor_level;
+			}
+		}
+
+		list_free(pubids);
+
+		entry->publish_as_relid = publish_as_relid;
+		entry->replicate_valid = true;
+	}
+
+	return entry;
+}
+
+/*
+ * Cleanup list of streamed transactions and update the schema_sent flag.
+ *
+ * When a streamed transaction commits or aborts, we need to remove the
+ * toplevel XID from the schema cache. If the transaction aborted, the
+ * subscriber will simply throw away the schema records we streamed, so
+ * we don't need to do anything else.
+ *
+ * If the transaction is committed, the subscriber will update the relation
+ * cache - so tweak the schema_sent flag accordingly.
+ */
+static void
+cleanup_rel_sync_cache(TransactionId xid, bool is_commit)
+{
+	HASH_SEQ_STATUS hash_seq;
+	RelationSyncEntry *entry;
+	ListCell   *lc;
+
+	Assert(RelationSyncCache != NULL);
+
+	hash_seq_init(&hash_seq, RelationSyncCache);
+	while ((entry = hash_seq_search(&hash_seq)) != NULL)
+	{
+		/*
+		 * We can set the schema_sent flag for an entry that has committed xid
+		 * in the list as that ensures that the subscriber would have the
+		 * corresponding schema and we don't need to send it unless there is
+		 * any invalidation for that relation.
+		 */
+		foreach(lc, entry->streamed_txns)
+		{
+			if (xid == (uint32) lfirst_int(lc))
+			{
+				if (is_commit)
+					entry->schema_sent = true;
+
+				entry->streamed_txns =
+					foreach_delete_current(entry->streamed_txns, lc);
+				break;
+			}
+		}
+	}
+}
+
+/*
+ * Relcache invalidation callback
+ */
+static void
+rel_sync_cache_relation_cb(Datum arg, Oid relid)
+{
+	RelationSyncEntry *entry;
+
+	/*
+	 * We can get here if the plugin was used in SQL interface as the
+	 * RelSchemaSyncCache is destroyed when the decoding finishes, but there
+	 * is no way to unregister the relcache invalidation callback.
+	 */
+	if (RelationSyncCache == NULL)
+		return;
+
+	/*
+	 * Nobody keeps pointers to entries in this hash table around outside
+	 * logical decoding callback calls - but invalidation events can come in
+	 * *during* a callback if we access the relcache in the callback. Because
+	 * of that we must mark the cache entry as invalid but not remove it from
+	 * the hash while it could still be referenced, then prune it at a later
+	 * safe point.
+	 *
+	 * Getting invalidations for relations that aren't in the table is
+	 * entirely normal, since there's no way to unregister for an invalidation
+	 * event. So we don't care if it's found or not.
+	 */
+	entry = (RelationSyncEntry *) hash_search(RelationSyncCache, &relid,
+											  HASH_FIND, NULL);
+
+	/*
+	 * Reset schema sent status as the relation definition may have changed.
+	 * Also free any objects that depended on the earlier definition.
+	 */
+	if (entry != NULL)
+	{
+		entry->schema_sent = false;
+		list_free(entry->streamed_txns);
+		entry->streamed_txns = NIL;
+		if (entry->map)
+		{
+			/*
+			 * Must free the TupleDescs contained in the map explicitly,
+			 * because free_conversion_map() doesn't.
+			 */
+			FreeTupleDesc(entry->map->indesc);
+			FreeTupleDesc(entry->map->outdesc);
+			free_conversion_map(entry->map);
+		}
+		entry->map = NULL;
+	}
+}
+
+/*
+ * Publication relation map syscache invalidation callback
+ */
+static void
+rel_sync_cache_publication_cb(Datum arg, int cacheid, uint32 hashvalue)
+{
+	HASH_SEQ_STATUS status;
+	RelationSyncEntry *entry;
+
+	/*
+	 * We can get here if the plugin was used in SQL interface as the
+	 * RelSchemaSyncCache is destroyed when the decoding finishes, but there
+	 * is no way to unregister the relcache invalidation callback.
+	 */
+	if (RelationSyncCache == NULL)
+		return;
+
+	/*
+	 * There is no way to find which entry in our cache the hash belongs to so
+	 * mark the whole cache as invalid.
+	 */
+	hash_seq_init(&status, RelationSyncCache);
+	while ((entry = (RelationSyncEntry *) hash_seq_search(&status)) != NULL)
+	{
+		entry->replicate_valid = false;
+
+		/*
+		 * There might be some relations dropped from the publication so we
+		 * don't need to publish the changes for them.
+		 */
+		entry->pubactions.pubinsert = false;
+		entry->pubactions.pubupdate = false;
+		entry->pubactions.pubdelete = false;
+		entry->pubactions.pubtruncate = false;
+	}
+}
+
+/*
+ * Try to update progress and send a keepalive message if too many changes were
+ * processed.
+ *
+ * For a large transaction, if we don't send any change to the downstream for a
+ * long time (exceeds the wal_receiver_timeout of standby) then it can timeout.
+ * This can happen when all or most of the changes are not published.
+ */
+static void
+update_replication_progress(LogicalDecodingContext *ctx)
+{
+	static int	changes_count = 0;
+
+	/*
+	 * We don't want to try sending a keepalive message after processing each
+	 * change as that can have overhead. Tests revealed that there is no
+	 * noticeable overhead in doing it after continuously processing 100 or so
+	 * changes.
+	 */
+#define CHANGES_THRESHOLD 100
+
+	/*
+	 * If we are at the end of transaction LSN, update progress tracking.
+	 * Otherwise, after continuously processing CHANGES_THRESHOLD changes, we
+	 * try to send a keepalive message if required.
+	 */
+	if (ctx->end_xact || ++changes_count >= CHANGES_THRESHOLD)
+	{
+		OutputPluginUpdateProgress(ctx);
+		changes_count = 0;
+	}
+}
diff --git a/src/backend/replication/repl_gram.c b/src/backend/replication/repl_gram.c
new file mode 100644
index 0000000..e8928c4
--- /dev/null
+++ b/src/backend/replication/repl_gram.c
@@ -0,0 +1,1895 @@
+/* A Bison parser, made by GNU Bison 3.7.5.  */
+
+/* Bison implementation for Yacc-like parsers in C
+
+   Copyright (C) 1984, 1989-1990, 2000-2015, 2018-2021 Free Software Foundation,
+   Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* As a special exception, you may create a larger work that contains
+   part or all of the Bison parser skeleton and distribute that work
+   under terms of your choice, so long as that work isn't itself a
+   parser generator using the skeleton or a modified version thereof
+   as a parser skeleton.  Alternatively, if you modify or redistribute
+   the parser skeleton itself, you may (at your option) remove this
+   special exception, which will cause the skeleton and the resulting
+   Bison output files to be licensed under the GNU General Public
+   License without this special exception.
+
+   This special exception was added by the Free Software Foundation in
+   version 2.2 of Bison.  */
+
+/* C LALR(1) parser skeleton written by Richard Stallman, by
+   simplifying the original so-called "semantic" parser.  */
+
+/* DO NOT RELY ON FEATURES THAT ARE NOT DOCUMENTED in the manual,
+   especially those whose name start with YY_ or yy_.  They are
+   private implementation details that can be changed or removed.  */
+
+/* All symbols defined below should begin with yy or YY, to avoid
+   infringing on user name space.  This should be done even for local
+   variables, as they might otherwise be expanded by user macros.
+   There are some unavoidable exceptions within include files to
+   define necessary library symbols; they are noted "INFRINGES ON
+   USER NAME SPACE" below.  */
+
+/* Identify Bison output, and Bison version.  */
+#define YYBISON 30705
+
+/* Bison version string.  */
+#define YYBISON_VERSION "3.7.5"
+
+/* Skeleton name.  */
+#define YYSKELETON_NAME "yacc.c"
+
+/* Pure parsers.  */
+#define YYPURE 0
+
+/* Push parsers.  */
+#define YYPUSH 0
+
+/* Pull parsers.  */
+#define YYPULL 1
+
+
+/* Substitute the variable and function names.  */
+#define yyparse         replication_yyparse
+#define yylex           replication_yylex
+#define yyerror         replication_yyerror
+#define yydebug         replication_yydebug
+#define yynerrs         replication_yynerrs
+#define yylval          replication_yylval
+#define yychar          replication_yychar
+
+/* First part of user prologue.  */
+#line 1 "repl_gram.y"
+
+/*-------------------------------------------------------------------------
+ *
+ * repl_gram.y				- Parser for the replication commands
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/repl_gram.y
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/xlogdefs.h"
+#include "nodes/makefuncs.h"
+#include "nodes/replnodes.h"
+#include "replication/walsender.h"
+#include "replication/walsender_private.h"
+
+
+/* Result of the parsing is returned here */
+Node *replication_parse_result;
+
+
+/*
+ * Bison doesn't allocate anything that needs to live across parser calls,
+ * so we can easily have it use palloc instead of malloc.  This prevents
+ * memory leaks if we error out during parsing.  Note this only works with
+ * bison >= 2.0.  However, in bison 1.875 the default is to use alloca()
+ * if possible, so there's not really much problem anyhow, at least if
+ * you're building with gcc.
+ */
+#define YYMALLOC palloc
+#define YYFREE   pfree
+
+
+#line 119 "repl_gram.c"
+
+# ifndef YY_CAST
+#  ifdef __cplusplus
+#   define YY_CAST(Type, Val) static_cast<Type> (Val)
+#   define YY_REINTERPRET_CAST(Type, Val) reinterpret_cast<Type> (Val)
+#  else
+#   define YY_CAST(Type, Val) ((Type) (Val))
+#   define YY_REINTERPRET_CAST(Type, Val) ((Type) (Val))
+#  endif
+# endif
+# ifndef YY_NULLPTR
+#  if defined __cplusplus
+#   if 201103L <= __cplusplus
+#    define YY_NULLPTR nullptr
+#   else
+#    define YY_NULLPTR 0
+#   endif
+#  else
+#   define YY_NULLPTR ((void*)0)
+#  endif
+# endif
+
+
+/* Debug traces.  */
+#ifndef YYDEBUG
+# define YYDEBUG 0
+#endif
+#if YYDEBUG
+extern int replication_yydebug;
+#endif
+
+/* Token kinds.  */
+#ifndef YYTOKENTYPE
+# define YYTOKENTYPE
+  enum yytokentype
+  {
+    YYEMPTY = -2,
+    YYEOF = 0,                     /* "end of file"  */
+    YYerror = 256,                 /* error  */
+    YYUNDEF = 257,                 /* "invalid token"  */
+    SCONST = 258,                  /* SCONST  */
+    IDENT = 259,                   /* IDENT  */
+    UCONST = 260,                  /* UCONST  */
+    RECPTR = 261,                  /* RECPTR  */
+    K_BASE_BACKUP = 262,           /* K_BASE_BACKUP  */
+    K_IDENTIFY_SYSTEM = 263,       /* K_IDENTIFY_SYSTEM  */
+    K_SHOW = 264,                  /* K_SHOW  */
+    K_START_REPLICATION = 265,     /* K_START_REPLICATION  */
+    K_CREATE_REPLICATION_SLOT = 266, /* K_CREATE_REPLICATION_SLOT  */
+    K_DROP_REPLICATION_SLOT = 267, /* K_DROP_REPLICATION_SLOT  */
+    K_TIMELINE_HISTORY = 268,      /* K_TIMELINE_HISTORY  */
+    K_LABEL = 269,                 /* K_LABEL  */
+    K_PROGRESS = 270,              /* K_PROGRESS  */
+    K_FAST = 271,                  /* K_FAST  */
+    K_WAIT = 272,                  /* K_WAIT  */
+    K_NOWAIT = 273,                /* K_NOWAIT  */
+    K_MAX_RATE = 274,              /* K_MAX_RATE  */
+    K_WAL = 275,                   /* K_WAL  */
+    K_TABLESPACE_MAP = 276,        /* K_TABLESPACE_MAP  */
+    K_NOVERIFY_CHECKSUMS = 277,    /* K_NOVERIFY_CHECKSUMS  */
+    K_TIMELINE = 278,              /* K_TIMELINE  */
+    K_PHYSICAL = 279,              /* K_PHYSICAL  */
+    K_LOGICAL = 280,               /* K_LOGICAL  */
+    K_SLOT = 281,                  /* K_SLOT  */
+    K_RESERVE_WAL = 282,           /* K_RESERVE_WAL  */
+    K_TEMPORARY = 283,             /* K_TEMPORARY  */
+    K_EXPORT_SNAPSHOT = 284,       /* K_EXPORT_SNAPSHOT  */
+    K_NOEXPORT_SNAPSHOT = 285,     /* K_NOEXPORT_SNAPSHOT  */
+    K_USE_SNAPSHOT = 286,          /* K_USE_SNAPSHOT  */
+    K_MANIFEST = 287,              /* K_MANIFEST  */
+    K_MANIFEST_CHECKSUMS = 288     /* K_MANIFEST_CHECKSUMS  */
+  };
+  typedef enum yytokentype yytoken_kind_t;
+#endif
+
+/* Value type.  */
+#if ! defined YYSTYPE && ! defined YYSTYPE_IS_DECLARED
+union YYSTYPE
+{
+#line 45 "repl_gram.y"
+
+		char					*str;
+		bool					boolval;
+		uint32					uintval;
+
+		XLogRecPtr				recptr;
+		Node					*node;
+		List					*list;
+		DefElem					*defelt;
+
+#line 210 "repl_gram.c"
+
+};
+typedef union YYSTYPE YYSTYPE;
+# define YYSTYPE_IS_TRIVIAL 1
+# define YYSTYPE_IS_DECLARED 1
+#endif
+
+
+extern YYSTYPE replication_yylval;
+
+int replication_yyparse (void);
+
+
+/* Symbol kind.  */
+enum yysymbol_kind_t
+{
+  YYSYMBOL_YYEMPTY = -2,
+  YYSYMBOL_YYEOF = 0,                      /* "end of file"  */
+  YYSYMBOL_YYerror = 1,                    /* error  */
+  YYSYMBOL_YYUNDEF = 2,                    /* "invalid token"  */
+  YYSYMBOL_SCONST = 3,                     /* SCONST  */
+  YYSYMBOL_IDENT = 4,                      /* IDENT  */
+  YYSYMBOL_UCONST = 5,                     /* UCONST  */
+  YYSYMBOL_RECPTR = 6,                     /* RECPTR  */
+  YYSYMBOL_K_BASE_BACKUP = 7,              /* K_BASE_BACKUP  */
+  YYSYMBOL_K_IDENTIFY_SYSTEM = 8,          /* K_IDENTIFY_SYSTEM  */
+  YYSYMBOL_K_SHOW = 9,                     /* K_SHOW  */
+  YYSYMBOL_K_START_REPLICATION = 10,       /* K_START_REPLICATION  */
+  YYSYMBOL_K_CREATE_REPLICATION_SLOT = 11, /* K_CREATE_REPLICATION_SLOT  */
+  YYSYMBOL_K_DROP_REPLICATION_SLOT = 12,   /* K_DROP_REPLICATION_SLOT  */
+  YYSYMBOL_K_TIMELINE_HISTORY = 13,        /* K_TIMELINE_HISTORY  */
+  YYSYMBOL_K_LABEL = 14,                   /* K_LABEL  */
+  YYSYMBOL_K_PROGRESS = 15,                /* K_PROGRESS  */
+  YYSYMBOL_K_FAST = 16,                    /* K_FAST  */
+  YYSYMBOL_K_WAIT = 17,                    /* K_WAIT  */
+  YYSYMBOL_K_NOWAIT = 18,                  /* K_NOWAIT  */
+  YYSYMBOL_K_MAX_RATE = 19,                /* K_MAX_RATE  */
+  YYSYMBOL_K_WAL = 20,                     /* K_WAL  */
+  YYSYMBOL_K_TABLESPACE_MAP = 21,          /* K_TABLESPACE_MAP  */
+  YYSYMBOL_K_NOVERIFY_CHECKSUMS = 22,      /* K_NOVERIFY_CHECKSUMS  */
+  YYSYMBOL_K_TIMELINE = 23,                /* K_TIMELINE  */
+  YYSYMBOL_K_PHYSICAL = 24,                /* K_PHYSICAL  */
+  YYSYMBOL_K_LOGICAL = 25,                 /* K_LOGICAL  */
+  YYSYMBOL_K_SLOT = 26,                    /* K_SLOT  */
+  YYSYMBOL_K_RESERVE_WAL = 27,             /* K_RESERVE_WAL  */
+  YYSYMBOL_K_TEMPORARY = 28,               /* K_TEMPORARY  */
+  YYSYMBOL_K_EXPORT_SNAPSHOT = 29,         /* K_EXPORT_SNAPSHOT  */
+  YYSYMBOL_K_NOEXPORT_SNAPSHOT = 30,       /* K_NOEXPORT_SNAPSHOT  */
+  YYSYMBOL_K_USE_SNAPSHOT = 31,            /* K_USE_SNAPSHOT  */
+  YYSYMBOL_K_MANIFEST = 32,                /* K_MANIFEST  */
+  YYSYMBOL_K_MANIFEST_CHECKSUMS = 33,      /* K_MANIFEST_CHECKSUMS  */
+  YYSYMBOL_34_ = 34,                       /* ';'  */
+  YYSYMBOL_35_ = 35,                       /* '.'  */
+  YYSYMBOL_36_ = 36,                       /* '('  */
+  YYSYMBOL_37_ = 37,                       /* ')'  */
+  YYSYMBOL_38_ = 38,                       /* ','  */
+  YYSYMBOL_YYACCEPT = 39,                  /* $accept  */
+  YYSYMBOL_firstcmd = 40,                  /* firstcmd  */
+  YYSYMBOL_opt_semicolon = 41,             /* opt_semicolon  */
+  YYSYMBOL_command = 42,                   /* command  */
+  YYSYMBOL_identify_system = 43,           /* identify_system  */
+  YYSYMBOL_show = 44,                      /* show  */
+  YYSYMBOL_var_name = 45,                  /* var_name  */
+  YYSYMBOL_base_backup = 46,               /* base_backup  */
+  YYSYMBOL_base_backup_opt_list = 47,      /* base_backup_opt_list  */
+  YYSYMBOL_base_backup_opt = 48,           /* base_backup_opt  */
+  YYSYMBOL_create_replication_slot = 49,   /* create_replication_slot  */
+  YYSYMBOL_create_slot_opt_list = 50,      /* create_slot_opt_list  */
+  YYSYMBOL_create_slot_opt = 51,           /* create_slot_opt  */
+  YYSYMBOL_drop_replication_slot = 52,     /* drop_replication_slot  */
+  YYSYMBOL_start_replication = 53,         /* start_replication  */
+  YYSYMBOL_start_logical_replication = 54, /* start_logical_replication  */
+  YYSYMBOL_timeline_history = 55,          /* timeline_history  */
+  YYSYMBOL_opt_physical = 56,              /* opt_physical  */
+  YYSYMBOL_opt_temporary = 57,             /* opt_temporary  */
+  YYSYMBOL_opt_slot = 58,                  /* opt_slot  */
+  YYSYMBOL_opt_timeline = 59,              /* opt_timeline  */
+  YYSYMBOL_plugin_options = 60,            /* plugin_options  */
+  YYSYMBOL_plugin_opt_list = 61,           /* plugin_opt_list  */
+  YYSYMBOL_plugin_opt_elem = 62,           /* plugin_opt_elem  */
+  YYSYMBOL_plugin_opt_arg = 63             /* plugin_opt_arg  */
+};
+typedef enum yysymbol_kind_t yysymbol_kind_t;
+
+
+
+
+#ifdef short
+# undef short
+#endif
+
+/* On compilers that do not define __PTRDIFF_MAX__ etc., make sure
+   <limits.h> and (if available) <stdint.h> are included
+   so that the code can choose integer types of a good width.  */
+
+#ifndef __PTRDIFF_MAX__
+# include <limits.h> /* INFRINGES ON USER NAME SPACE */
+# if defined __STDC_VERSION__ && 199901 <= __STDC_VERSION__
+#  include <stdint.h> /* INFRINGES ON USER NAME SPACE */
+#  define YY_STDINT_H
+# endif
+#endif
+
+/* Narrow types that promote to a signed type and that can represent a
+   signed or unsigned integer of at least N bits.  In tables they can
+   save space and decrease cache pressure.  Promoting to a signed type
+   helps avoid bugs in integer arithmetic.  */
+
+#ifdef __INT_LEAST8_MAX__
+typedef __INT_LEAST8_TYPE__ yytype_int8;
+#elif defined YY_STDINT_H
+typedef int_least8_t yytype_int8;
+#else
+typedef signed char yytype_int8;
+#endif
+
+#ifdef __INT_LEAST16_MAX__
+typedef __INT_LEAST16_TYPE__ yytype_int16;
+#elif defined YY_STDINT_H
+typedef int_least16_t yytype_int16;
+#else
+typedef short yytype_int16;
+#endif
+
+/* Work around bug in HP-UX 11.23, which defines these macros
+   incorrectly for preprocessor constants.  This workaround can likely
+   be removed in 2023, as HPE has promised support for HP-UX 11.23
+   (aka HP-UX 11i v2) only through the end of 2022; see Table 2 of
+   <https://h20195.www2.hpe.com/V2/getpdf.aspx/4AA4-7673ENW.pdf>.  */
+#ifdef __hpux
+# undef UINT_LEAST8_MAX
+# undef UINT_LEAST16_MAX
+# define UINT_LEAST8_MAX 255
+# define UINT_LEAST16_MAX 65535
+#endif
+
+#if defined __UINT_LEAST8_MAX__ && __UINT_LEAST8_MAX__ <= __INT_MAX__
+typedef __UINT_LEAST8_TYPE__ yytype_uint8;
+#elif (!defined __UINT_LEAST8_MAX__ && defined YY_STDINT_H \
+       && UINT_LEAST8_MAX <= INT_MAX)
+typedef uint_least8_t yytype_uint8;
+#elif !defined __UINT_LEAST8_MAX__ && UCHAR_MAX <= INT_MAX
+typedef unsigned char yytype_uint8;
+#else
+typedef short yytype_uint8;
+#endif
+
+#if defined __UINT_LEAST16_MAX__ && __UINT_LEAST16_MAX__ <= __INT_MAX__
+typedef __UINT_LEAST16_TYPE__ yytype_uint16;
+#elif (!defined __UINT_LEAST16_MAX__ && defined YY_STDINT_H \
+       && UINT_LEAST16_MAX <= INT_MAX)
+typedef uint_least16_t yytype_uint16;
+#elif !defined __UINT_LEAST16_MAX__ && USHRT_MAX <= INT_MAX
+typedef unsigned short yytype_uint16;
+#else
+typedef int yytype_uint16;
+#endif
+
+#ifndef YYPTRDIFF_T
+# if defined __PTRDIFF_TYPE__ && defined __PTRDIFF_MAX__
+#  define YYPTRDIFF_T __PTRDIFF_TYPE__
+#  define YYPTRDIFF_MAXIMUM __PTRDIFF_MAX__
+# elif defined PTRDIFF_MAX
+#  ifndef ptrdiff_t
+#   include <stddef.h> /* INFRINGES ON USER NAME SPACE */
+#  endif
+#  define YYPTRDIFF_T ptrdiff_t
+#  define YYPTRDIFF_MAXIMUM PTRDIFF_MAX
+# else
+#  define YYPTRDIFF_T long
+#  define YYPTRDIFF_MAXIMUM LONG_MAX
+# endif
+#endif
+
+#ifndef YYSIZE_T
+# ifdef __SIZE_TYPE__
+#  define YYSIZE_T __SIZE_TYPE__
+# elif defined size_t
+#  define YYSIZE_T size_t
+# elif defined __STDC_VERSION__ && 199901 <= __STDC_VERSION__
+#  include <stddef.h> /* INFRINGES ON USER NAME SPACE */
+#  define YYSIZE_T size_t
+# else
+#  define YYSIZE_T unsigned
+# endif
+#endif
+
+#define YYSIZE_MAXIMUM                                  \
+  YY_CAST (YYPTRDIFF_T,                                 \
+           (YYPTRDIFF_MAXIMUM < YY_CAST (YYSIZE_T, -1)  \
+            ? YYPTRDIFF_MAXIMUM                         \
+            : YY_CAST (YYSIZE_T, -1)))
+
+#define YYSIZEOF(X) YY_CAST (YYPTRDIFF_T, sizeof (X))
+
+
+/* Stored state numbers (used for stacks). */
+typedef yytype_int8 yy_state_t;
+
+/* State numbers in computations.  */
+typedef int yy_state_fast_t;
+
+#ifndef YY_
+# if defined YYENABLE_NLS && YYENABLE_NLS
+#  if ENABLE_NLS
+#   include <libintl.h> /* INFRINGES ON USER NAME SPACE */
+#   define YY_(Msgid) dgettext ("bison-runtime", Msgid)
+#  endif
+# endif
+# ifndef YY_
+#  define YY_(Msgid) Msgid
+# endif
+#endif
+
+
+#ifndef YY_ATTRIBUTE_PURE
+# if defined __GNUC__ && 2 < __GNUC__ + (96 <= __GNUC_MINOR__)
+#  define YY_ATTRIBUTE_PURE __attribute__ ((__pure__))
+# else
+#  define YY_ATTRIBUTE_PURE
+# endif
+#endif
+
+#ifndef YY_ATTRIBUTE_UNUSED
+# if defined __GNUC__ && 2 < __GNUC__ + (7 <= __GNUC_MINOR__)
+#  define YY_ATTRIBUTE_UNUSED __attribute__ ((__unused__))
+# else
+#  define YY_ATTRIBUTE_UNUSED
+# endif
+#endif
+
+/* Suppress unused-variable warnings by "using" E.  */
+#if ! defined lint || defined __GNUC__
+# define YY_USE(E) ((void) (E))
+#else
+# define YY_USE(E) /* empty */
+#endif
+
+#if defined __GNUC__ && ! defined __ICC && 407 <= __GNUC__ * 100 + __GNUC_MINOR__
+/* Suppress an incorrect diagnostic about yylval being uninitialized.  */
+# define YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN                            \
+    _Pragma ("GCC diagnostic push")                                     \
+    _Pragma ("GCC diagnostic ignored \"-Wuninitialized\"")              \
+    _Pragma ("GCC diagnostic ignored \"-Wmaybe-uninitialized\"")
+# define YY_IGNORE_MAYBE_UNINITIALIZED_END      \
+    _Pragma ("GCC diagnostic pop")
+#else
+# define YY_INITIAL_VALUE(Value) Value
+#endif
+#ifndef YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN
+# define YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN
+# define YY_IGNORE_MAYBE_UNINITIALIZED_END
+#endif
+#ifndef YY_INITIAL_VALUE
+# define YY_INITIAL_VALUE(Value) /* Nothing. */
+#endif
+
+#if defined __cplusplus && defined __GNUC__ && ! defined __ICC && 6 <= __GNUC__
+# define YY_IGNORE_USELESS_CAST_BEGIN                          \
+    _Pragma ("GCC diagnostic push")                            \
+    _Pragma ("GCC diagnostic ignored \"-Wuseless-cast\"")
+# define YY_IGNORE_USELESS_CAST_END            \
+    _Pragma ("GCC diagnostic pop")
+#endif
+#ifndef YY_IGNORE_USELESS_CAST_BEGIN
+# define YY_IGNORE_USELESS_CAST_BEGIN
+# define YY_IGNORE_USELESS_CAST_END
+#endif
+
+
+#define YY_ASSERT(E) ((void) (0 && (E)))
+
+#if !defined yyoverflow
+
+/* The parser invokes alloca or malloc; define the necessary symbols.  */
+
+# ifdef YYSTACK_USE_ALLOCA
+#  if YYSTACK_USE_ALLOCA
+#   ifdef __GNUC__
+#    define YYSTACK_ALLOC __builtin_alloca
+#   elif defined __BUILTIN_VA_ARG_INCR
+#    include <alloca.h> /* INFRINGES ON USER NAME SPACE */
+#   elif defined _AIX
+#    define YYSTACK_ALLOC __alloca
+#   elif defined _MSC_VER
+#    include <malloc.h> /* INFRINGES ON USER NAME SPACE */
+#    define alloca _alloca
+#   else
+#    define YYSTACK_ALLOC alloca
+#    if ! defined _ALLOCA_H && ! defined EXIT_SUCCESS
+#     include <stdlib.h> /* INFRINGES ON USER NAME SPACE */
+      /* Use EXIT_SUCCESS as a witness for stdlib.h.  */
+#     ifndef EXIT_SUCCESS
+#      define EXIT_SUCCESS 0
+#     endif
+#    endif
+#   endif
+#  endif
+# endif
+
+# ifdef YYSTACK_ALLOC
+   /* Pacify GCC's 'empty if-body' warning.  */
+#  define YYSTACK_FREE(Ptr) do { /* empty */; } while (0)
+#  ifndef YYSTACK_ALLOC_MAXIMUM
+    /* The OS might guarantee only one guard page at the bottom of the stack,
+       and a page size can be as small as 4096 bytes.  So we cannot safely
+       invoke alloca (N) if N exceeds 4096.  Use a slightly smaller number
+       to allow for a few compiler-allocated temporary stack slots.  */
+#   define YYSTACK_ALLOC_MAXIMUM 4032 /* reasonable circa 2006 */
+#  endif
+# else
+#  define YYSTACK_ALLOC YYMALLOC
+#  define YYSTACK_FREE YYFREE
+#  ifndef YYSTACK_ALLOC_MAXIMUM
+#   define YYSTACK_ALLOC_MAXIMUM YYSIZE_MAXIMUM
+#  endif
+#  if (defined __cplusplus && ! defined EXIT_SUCCESS \
+       && ! ((defined YYMALLOC || defined malloc) \
+             && (defined YYFREE || defined free)))
+#   include <stdlib.h> /* INFRINGES ON USER NAME SPACE */
+#   ifndef EXIT_SUCCESS
+#    define EXIT_SUCCESS 0
+#   endif
+#  endif
+#  ifndef YYMALLOC
+#   define YYMALLOC malloc
+#   if ! defined malloc && ! defined EXIT_SUCCESS
+void *malloc (YYSIZE_T); /* INFRINGES ON USER NAME SPACE */
+#   endif
+#  endif
+#  ifndef YYFREE
+#   define YYFREE free
+#   if ! defined free && ! defined EXIT_SUCCESS
+void free (void *); /* INFRINGES ON USER NAME SPACE */
+#   endif
+#  endif
+# endif
+#endif /* !defined yyoverflow */
+
+#if (! defined yyoverflow \
+     && (! defined __cplusplus \
+         || (defined YYSTYPE_IS_TRIVIAL && YYSTYPE_IS_TRIVIAL)))
+
+/* A type that is properly aligned for any stack member.  */
+union yyalloc
+{
+  yy_state_t yyss_alloc;
+  YYSTYPE yyvs_alloc;
+};
+
+/* The size of the maximum gap between one aligned stack and the next.  */
+# define YYSTACK_GAP_MAXIMUM (YYSIZEOF (union yyalloc) - 1)
+
+/* The size of an array large to enough to hold all stacks, each with
+   N elements.  */
+# define YYSTACK_BYTES(N) \
+     ((N) * (YYSIZEOF (yy_state_t) + YYSIZEOF (YYSTYPE)) \
+      + YYSTACK_GAP_MAXIMUM)
+
+# define YYCOPY_NEEDED 1
+
+/* Relocate STACK from its old location to the new one.  The
+   local variables YYSIZE and YYSTACKSIZE give the old and new number of
+   elements in the stack, and YYPTR gives the new location of the
+   stack.  Advance YYPTR to a properly aligned location for the next
+   stack.  */
+# define YYSTACK_RELOCATE(Stack_alloc, Stack)                           \
+    do                                                                  \
+      {                                                                 \
+        YYPTRDIFF_T yynewbytes;                                         \
+        YYCOPY (&yyptr->Stack_alloc, Stack, yysize);                    \
+        Stack = &yyptr->Stack_alloc;                                    \
+        yynewbytes = yystacksize * YYSIZEOF (*Stack) + YYSTACK_GAP_MAXIMUM; \
+        yyptr += yynewbytes / YYSIZEOF (*yyptr);                        \
+      }                                                                 \
+    while (0)
+
+#endif
+
+#if defined YYCOPY_NEEDED && YYCOPY_NEEDED
+/* Copy COUNT objects from SRC to DST.  The source and destination do
+   not overlap.  */
+# ifndef YYCOPY
+#  if defined __GNUC__ && 1 < __GNUC__
+#   define YYCOPY(Dst, Src, Count) \
+      __builtin_memcpy (Dst, Src, YY_CAST (YYSIZE_T, (Count)) * sizeof (*(Src)))
+#  else
+#   define YYCOPY(Dst, Src, Count)              \
+      do                                        \
+        {                                       \
+          YYPTRDIFF_T yyi;                      \
+          for (yyi = 0; yyi < (Count); yyi++)   \
+            (Dst)[yyi] = (Src)[yyi];            \
+        }                                       \
+      while (0)
+#  endif
+# endif
+#endif /* !YYCOPY_NEEDED */
+
+/* YYFINAL -- State number of the termination state.  */
+#define YYFINAL  26
+/* YYLAST -- Last index in YYTABLE.  */
+#define YYLAST   52
+
+/* YYNTOKENS -- Number of terminals.  */
+#define YYNTOKENS  39
+/* YYNNTS -- Number of nonterminals.  */
+#define YYNNTS  25
+/* YYNRULES -- Number of rules.  */
+#define YYNRULES  57
+/* YYNSTATES -- Number of states.  */
+#define YYNSTATES  78
+
+/* YYMAXUTOK -- Last valid token kind.  */
+#define YYMAXUTOK   288
+
+
+/* YYTRANSLATE(TOKEN-NUM) -- Symbol number corresponding to TOKEN-NUM
+   as returned by yylex, with out-of-bounds checking.  */
+#define YYTRANSLATE(YYX)                                \
+  (0 <= (YYX) && (YYX) <= YYMAXUTOK                     \
+   ? YY_CAST (yysymbol_kind_t, yytranslate[YYX])        \
+   : YYSYMBOL_YYUNDEF)
+
+/* YYTRANSLATE[TOKEN-NUM] -- Symbol number corresponding to TOKEN-NUM
+   as returned by yylex.  */
+static const yytype_int8 yytranslate[] =
+{
+       0,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+      36,    37,     2,     2,    38,     2,    35,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,    34,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     1,     2,     3,     4,
+       5,     6,     7,     8,     9,    10,    11,    12,    13,    14,
+      15,    16,    17,    18,    19,    20,    21,    22,    23,    24,
+      25,    26,    27,    28,    29,    30,    31,    32,    33
+};
+
+#if YYDEBUG
+  /* YYRLINE[YYN] -- Source line where rule number YYN was defined.  */
+static const yytype_int16 yyrline[] =
+{
+       0,   107,   107,   113,   114,   118,   119,   120,   121,   122,
+     123,   124,   125,   132,   142,   149,   150,   160,   169,   172,
+     176,   181,   186,   191,   196,   201,   206,   211,   216,   221,
+     230,   241,   255,   258,   262,   267,   272,   277,   286,   294,
+     308,   323,   338,   355,   356,   360,   361,   365,   368,   372,
+     380,   385,   386,   390,   394,   401,   408,   409
+};
+#endif
+
+/** Accessing symbol of state STATE.  */
+#define YY_ACCESSING_SYMBOL(State) YY_CAST (yysymbol_kind_t, yystos[State])
+
+#if YYDEBUG || 0
+/* The user-facing name of the symbol whose (internal) number is
+   YYSYMBOL.  No bounds checking.  */
+static const char *yysymbol_name (yysymbol_kind_t yysymbol) YY_ATTRIBUTE_UNUSED;
+
+/* YYTNAME[SYMBOL-NUM] -- String name of the symbol SYMBOL-NUM.
+   First, the terminals, then, starting at YYNTOKENS, nonterminals.  */
+static const char *const yytname[] =
+{
+  "\"end of file\"", "error", "\"invalid token\"", "SCONST", "IDENT",
+  "UCONST", "RECPTR", "K_BASE_BACKUP", "K_IDENTIFY_SYSTEM", "K_SHOW",
+  "K_START_REPLICATION", "K_CREATE_REPLICATION_SLOT",
+  "K_DROP_REPLICATION_SLOT", "K_TIMELINE_HISTORY", "K_LABEL", "K_PROGRESS",
+  "K_FAST", "K_WAIT", "K_NOWAIT", "K_MAX_RATE", "K_WAL",
+  "K_TABLESPACE_MAP", "K_NOVERIFY_CHECKSUMS", "K_TIMELINE", "K_PHYSICAL",
+  "K_LOGICAL", "K_SLOT", "K_RESERVE_WAL", "K_TEMPORARY",
+  "K_EXPORT_SNAPSHOT", "K_NOEXPORT_SNAPSHOT", "K_USE_SNAPSHOT",
+  "K_MANIFEST", "K_MANIFEST_CHECKSUMS", "';'", "'.'", "'('", "')'", "','",
+  "$accept", "firstcmd", "opt_semicolon", "command", "identify_system",
+  "show", "var_name", "base_backup", "base_backup_opt_list",
+  "base_backup_opt", "create_replication_slot", "create_slot_opt_list",
+  "create_slot_opt", "drop_replication_slot", "start_replication",
+  "start_logical_replication", "timeline_history", "opt_physical",
+  "opt_temporary", "opt_slot", "opt_timeline", "plugin_options",
+  "plugin_opt_list", "plugin_opt_elem", "plugin_opt_arg", YY_NULLPTR
+};
+
+static const char *
+yysymbol_name (yysymbol_kind_t yysymbol)
+{
+  return yytname[yysymbol];
+}
+#endif
+
+#ifdef YYPRINT
+/* YYTOKNUM[NUM] -- (External) token number corresponding to the
+   (internal) symbol number NUM (which must be that of a token).  */
+static const yytype_int16 yytoknum[] =
+{
+       0,   256,   257,   258,   259,   260,   261,   262,   263,   264,
+     265,   266,   267,   268,   269,   270,   271,   272,   273,   274,
+     275,   276,   277,   278,   279,   280,   281,   282,   283,   284,
+     285,   286,   287,   288,    59,    46,    40,    41,    44
+};
+#endif
+
+#define YYPACT_NINF (-25)
+
+#define yypact_value_is_default(Yyn) \
+  ((Yyn) == YYPACT_NINF)
+
+#define YYTABLE_NINF (-1)
+
+#define yytable_value_is_error(Yyn) \
+  0
+
+  /* YYPACT[STATE-NUM] -- Index in YYTABLE of the portion describing
+     STATE-NUM.  */
+static const yytype_int8 yypact[] =
+{
+       2,   -25,   -25,    -1,    -5,    23,    24,    25,    29,    -3,
+     -25,   -25,   -25,   -25,   -25,   -25,   -25,   -25,   -14,   -25,
+      -2,    28,    10,     7,    19,   -25,   -25,   -25,   -25,    34,
+     -25,   -25,   -25,    33,   -25,   -25,   -25,    36,    37,   -25,
+      38,    16,   -25,    39,   -25,    -8,   -25,   -25,   -25,   -25,
+     -25,   -25,    40,    20,   -25,    43,     8,    44,   -25,    -7,
+     -25,    46,   -25,   -25,   -25,   -25,   -25,   -25,   -25,    -7,
+      45,   -12,   -25,   -25,   -25,   -25,    46,   -25
+};
+
+  /* YYDEFACT[STATE-NUM] -- Default reduction number in state STATE-NUM.
+     Performed when YYTABLE does not specify something else to do.  Zero
+     means the default is an error.  */
+static const yytype_int8 yydefact[] =
+{
+       0,    19,    13,     0,    48,     0,     0,     0,     0,     4,
+       5,    12,     6,     9,    10,     7,     8,    11,    17,    15,
+      14,     0,    44,    46,    38,    42,     1,     3,     2,     0,
+      21,    22,    24,     0,    23,    26,    27,     0,     0,    18,
+       0,    47,    43,     0,    45,     0,    39,    20,    25,    28,
+      29,    16,     0,    50,    33,     0,    52,     0,    40,    30,
+      33,     0,    41,    49,    37,    34,    35,    36,    32,    31,
+      57,     0,    53,    56,    55,    51,     0,    54
+};
+
+  /* YYPGOTO[NTERM-NUM].  */
+static const yytype_int8 yypgoto[] =
+{
+     -25,   -25,   -25,   -25,   -25,   -25,   -25,   -25,   -25,   -25,
+     -25,    -9,   -25,   -25,   -25,   -25,   -25,   -25,   -25,   -25,
+     -25,   -25,   -25,   -24,   -25
+};
+
+  /* YYDEFGOTO[NTERM-NUM].  */
+static const yytype_int8 yydefgoto[] =
+{
+       0,     8,    28,     9,    10,    11,    20,    12,    18,    39,
+      13,    59,    68,    14,    15,    16,    17,    43,    45,    22,
+      58,    62,    71,    72,    74
+};
+
+  /* YYTABLE[YYPACT[STATE-NUM]] -- What to do in state STATE-NUM.  If
+     positive, shift that token.  If negative, reduce the rule whose
+     number is the opposite.  If YYTABLE_NINF, syntax error.  */
+static const yytype_int8 yytable[] =
+{
+      29,    30,    31,    19,    32,    33,    34,    35,    36,     1,
+       2,     3,     4,     5,     6,     7,    54,    55,    37,    38,
+      64,    21,    65,    66,    67,    75,    76,    23,    24,    26,
+      25,    27,    41,    40,    42,    44,    46,    47,    48,    49,
+      50,    52,    51,    57,    61,    53,    56,    60,    73,    63,
+      70,    69,    77
+};
+
+static const yytype_int8 yycheck[] =
+{
+      14,    15,    16,     4,    18,    19,    20,    21,    22,     7,
+       8,     9,    10,    11,    12,    13,    24,    25,    32,    33,
+      27,    26,    29,    30,    31,    37,    38,     4,     4,     0,
+       5,    34,     4,    35,    24,    28,    17,     3,     5,     3,
+       3,    25,     4,    23,    36,     6,     6,     4,     3,     5,
+       4,    60,    76
+};
+
+  /* YYSTOS[STATE-NUM] -- The (internal number of the) accessing
+     symbol of state STATE-NUM.  */
+static const yytype_int8 yystos[] =
+{
+       0,     7,     8,     9,    10,    11,    12,    13,    40,    42,
+      43,    44,    46,    49,    52,    53,    54,    55,    47,     4,
+      45,    26,    58,     4,     4,     5,     0,    34,    41,    14,
+      15,    16,    18,    19,    20,    21,    22,    32,    33,    48,
+      35,     4,    24,    56,    28,    57,    17,     3,     5,     3,
+       3,     4,    25,     6,    24,    25,     6,    23,    59,    50,
+       4,    36,    60,     5,    27,    29,    30,    31,    51,    50,
+       4,    61,    62,     3,    63,    37,    38,    62
+};
+
+  /* YYR1[YYN] -- Symbol number of symbol that rule YYN derives.  */
+static const yytype_int8 yyr1[] =
+{
+       0,    39,    40,    41,    41,    42,    42,    42,    42,    42,
+      42,    42,    42,    43,    44,    45,    45,    46,    47,    47,
+      48,    48,    48,    48,    48,    48,    48,    48,    48,    48,
+      49,    49,    50,    50,    51,    51,    51,    51,    52,    52,
+      53,    54,    55,    56,    56,    57,    57,    58,    58,    59,
+      59,    60,    60,    61,    61,    62,    63,    63
+};
+
+  /* YYR2[YYN] -- Number of symbols on the right hand side of rule YYN.  */
+static const yytype_int8 yyr2[] =
+{
+       0,     2,     2,     1,     0,     1,     1,     1,     1,     1,
+       1,     1,     1,     1,     2,     1,     3,     2,     2,     0,
+       2,     1,     1,     1,     1,     2,     1,     1,     2,     2,
+       5,     6,     2,     0,     1,     1,     1,     1,     2,     3,
+       5,     6,     2,     1,     0,     1,     0,     2,     0,     2,
+       0,     3,     0,     1,     3,     2,     1,     0
+};
+
+
+enum { YYENOMEM = -2 };
+
+#define yyerrok         (yyerrstatus = 0)
+#define yyclearin       (yychar = YYEMPTY)
+
+#define YYACCEPT        goto yyacceptlab
+#define YYABORT         goto yyabortlab
+#define YYERROR         goto yyerrorlab
+
+
+#define YYRECOVERING()  (!!yyerrstatus)
+
+#define YYBACKUP(Token, Value)                                    \
+  do                                                              \
+    if (yychar == YYEMPTY)                                        \
+      {                                                           \
+        yychar = (Token);                                         \
+        yylval = (Value);                                         \
+        YYPOPSTACK (yylen);                                       \
+        yystate = *yyssp;                                         \
+        goto yybackup;                                            \
+      }                                                           \
+    else                                                          \
+      {                                                           \
+        yyerror (YY_("syntax error: cannot back up")); \
+        YYERROR;                                                  \
+      }                                                           \
+  while (0)
+
+/* Backward compatibility with an undocumented macro.
+   Use YYerror or YYUNDEF. */
+#define YYERRCODE YYUNDEF
+
+
+/* Enable debugging if requested.  */
+#if YYDEBUG
+
+# ifndef YYFPRINTF
+#  include <stdio.h> /* INFRINGES ON USER NAME SPACE */
+#  define YYFPRINTF fprintf
+# endif
+
+# define YYDPRINTF(Args)                        \
+do {                                            \
+  if (yydebug)                                  \
+    YYFPRINTF Args;                             \
+} while (0)
+
+/* This macro is provided for backward compatibility. */
+# ifndef YY_LOCATION_PRINT
+#  define YY_LOCATION_PRINT(File, Loc) ((void) 0)
+# endif
+
+
+# define YY_SYMBOL_PRINT(Title, Kind, Value, Location)                    \
+do {                                                                      \
+  if (yydebug)                                                            \
+    {                                                                     \
+      YYFPRINTF (stderr, "%s ", Title);                                   \
+      yy_symbol_print (stderr,                                            \
+                  Kind, Value); \
+      YYFPRINTF (stderr, "\n");                                           \
+    }                                                                     \
+} while (0)
+
+
+/*-----------------------------------.
+| Print this symbol's value on YYO.  |
+`-----------------------------------*/
+
+static void
+yy_symbol_value_print (FILE *yyo,
+                       yysymbol_kind_t yykind, YYSTYPE const * const yyvaluep)
+{
+  FILE *yyoutput = yyo;
+  YY_USE (yyoutput);
+  if (!yyvaluep)
+    return;
+# ifdef YYPRINT
+  if (yykind < YYNTOKENS)
+    YYPRINT (yyo, yytoknum[yykind], *yyvaluep);
+# endif
+  YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN
+  YY_USE (yykind);
+  YY_IGNORE_MAYBE_UNINITIALIZED_END
+}
+
+
+/*---------------------------.
+| Print this symbol on YYO.  |
+`---------------------------*/
+
+static void
+yy_symbol_print (FILE *yyo,
+                 yysymbol_kind_t yykind, YYSTYPE const * const yyvaluep)
+{
+  YYFPRINTF (yyo, "%s %s (",
+             yykind < YYNTOKENS ? "token" : "nterm", yysymbol_name (yykind));
+
+  yy_symbol_value_print (yyo, yykind, yyvaluep);
+  YYFPRINTF (yyo, ")");
+}
+
+/*------------------------------------------------------------------.
+| yy_stack_print -- Print the state stack from its BOTTOM up to its |
+| TOP (included).                                                   |
+`------------------------------------------------------------------*/
+
+static void
+yy_stack_print (yy_state_t *yybottom, yy_state_t *yytop)
+{
+  YYFPRINTF (stderr, "Stack now");
+  for (; yybottom <= yytop; yybottom++)
+    {
+      int yybot = *yybottom;
+      YYFPRINTF (stderr, " %d", yybot);
+    }
+  YYFPRINTF (stderr, "\n");
+}
+
+# define YY_STACK_PRINT(Bottom, Top)                            \
+do {                                                            \
+  if (yydebug)                                                  \
+    yy_stack_print ((Bottom), (Top));                           \
+} while (0)
+
+
+/*------------------------------------------------.
+| Report that the YYRULE is going to be reduced.  |
+`------------------------------------------------*/
+
+static void
+yy_reduce_print (yy_state_t *yyssp, YYSTYPE *yyvsp,
+                 int yyrule)
+{
+  int yylno = yyrline[yyrule];
+  int yynrhs = yyr2[yyrule];
+  int yyi;
+  YYFPRINTF (stderr, "Reducing stack by rule %d (line %d):\n",
+             yyrule - 1, yylno);
+  /* The symbols being reduced.  */
+  for (yyi = 0; yyi < yynrhs; yyi++)
+    {
+      YYFPRINTF (stderr, "   $%d = ", yyi + 1);
+      yy_symbol_print (stderr,
+                       YY_ACCESSING_SYMBOL (+yyssp[yyi + 1 - yynrhs]),
+                       &yyvsp[(yyi + 1) - (yynrhs)]);
+      YYFPRINTF (stderr, "\n");
+    }
+}
+
+# define YY_REDUCE_PRINT(Rule)          \
+do {                                    \
+  if (yydebug)                          \
+    yy_reduce_print (yyssp, yyvsp, Rule); \
+} while (0)
+
+/* Nonzero means print parse trace.  It is left uninitialized so that
+   multiple parsers can coexist.  */
+int yydebug;
+#else /* !YYDEBUG */
+# define YYDPRINTF(Args) ((void) 0)
+# define YY_SYMBOL_PRINT(Title, Kind, Value, Location)
+# define YY_STACK_PRINT(Bottom, Top)
+# define YY_REDUCE_PRINT(Rule)
+#endif /* !YYDEBUG */
+
+
+/* YYINITDEPTH -- initial size of the parser's stacks.  */
+#ifndef YYINITDEPTH
+# define YYINITDEPTH 200
+#endif
+
+/* YYMAXDEPTH -- maximum size the stacks can grow to (effective only
+   if the built-in stack extension method is used).
+
+   Do not make this value too large; the results are undefined if
+   YYSTACK_ALLOC_MAXIMUM < YYSTACK_BYTES (YYMAXDEPTH)
+   evaluated with infinite-precision integer arithmetic.  */
+
+#ifndef YYMAXDEPTH
+# define YYMAXDEPTH 10000
+#endif
+
+
+
+
+
+
+/*-----------------------------------------------.
+| Release the memory associated to this symbol.  |
+`-----------------------------------------------*/
+
+static void
+yydestruct (const char *yymsg,
+            yysymbol_kind_t yykind, YYSTYPE *yyvaluep)
+{
+  YY_USE (yyvaluep);
+  if (!yymsg)
+    yymsg = "Deleting";
+  YY_SYMBOL_PRINT (yymsg, yykind, yyvaluep, yylocationp);
+
+  YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN
+  YY_USE (yykind);
+  YY_IGNORE_MAYBE_UNINITIALIZED_END
+}
+
+
+/* Lookahead token kind.  */
+int yychar;
+
+/* The semantic value of the lookahead symbol.  */
+YYSTYPE yylval;
+/* Number of syntax errors so far.  */
+int yynerrs;
+
+
+
+
+/*----------.
+| yyparse.  |
+`----------*/
+
+int
+yyparse (void)
+{
+    yy_state_fast_t yystate = 0;
+    /* Number of tokens to shift before error messages enabled.  */
+    int yyerrstatus = 0;
+
+    /* Refer to the stacks through separate pointers, to allow yyoverflow
+       to reallocate them elsewhere.  */
+
+    /* Their size.  */
+    YYPTRDIFF_T yystacksize = YYINITDEPTH;
+
+    /* The state stack: array, bottom, top.  */
+    yy_state_t yyssa[YYINITDEPTH];
+    yy_state_t *yyss = yyssa;
+    yy_state_t *yyssp = yyss;
+
+    /* The semantic value stack: array, bottom, top.  */
+    YYSTYPE yyvsa[YYINITDEPTH];
+    YYSTYPE *yyvs = yyvsa;
+    YYSTYPE *yyvsp = yyvs;
+
+  int yyn;
+  /* The return value of yyparse.  */
+  int yyresult;
+  /* Lookahead symbol kind.  */
+  yysymbol_kind_t yytoken = YYSYMBOL_YYEMPTY;
+  /* The variables used to return semantic value and location from the
+     action routines.  */
+  YYSTYPE yyval;
+
+
+
+#define YYPOPSTACK(N)   (yyvsp -= (N), yyssp -= (N))
+
+  /* The number of symbols on the RHS of the reduced rule.
+     Keep to zero when no symbol should be popped.  */
+  int yylen = 0;
+
+  YYDPRINTF ((stderr, "Starting parse\n"));
+
+  yychar = YYEMPTY; /* Cause a token to be read.  */
+  goto yysetstate;
+
+
+/*------------------------------------------------------------.
+| yynewstate -- push a new state, which is found in yystate.  |
+`------------------------------------------------------------*/
+yynewstate:
+  /* In all cases, when you get here, the value and location stacks
+     have just been pushed.  So pushing a state here evens the stacks.  */
+  yyssp++;
+
+
+/*--------------------------------------------------------------------.
+| yysetstate -- set current state (the top of the stack) to yystate.  |
+`--------------------------------------------------------------------*/
+yysetstate:
+  YYDPRINTF ((stderr, "Entering state %d\n", yystate));
+  YY_ASSERT (0 <= yystate && yystate < YYNSTATES);
+  YY_IGNORE_USELESS_CAST_BEGIN
+  *yyssp = YY_CAST (yy_state_t, yystate);
+  YY_IGNORE_USELESS_CAST_END
+  YY_STACK_PRINT (yyss, yyssp);
+
+  if (yyss + yystacksize - 1 <= yyssp)
+#if !defined yyoverflow && !defined YYSTACK_RELOCATE
+    goto yyexhaustedlab;
+#else
+    {
+      /* Get the current used size of the three stacks, in elements.  */
+      YYPTRDIFF_T yysize = yyssp - yyss + 1;
+
+# if defined yyoverflow
+      {
+        /* Give user a chance to reallocate the stack.  Use copies of
+           these so that the &'s don't force the real ones into
+           memory.  */
+        yy_state_t *yyss1 = yyss;
+        YYSTYPE *yyvs1 = yyvs;
+
+        /* Each stack pointer address is followed by the size of the
+           data in use in that stack, in bytes.  This used to be a
+           conditional around just the two extra args, but that might
+           be undefined if yyoverflow is a macro.  */
+        yyoverflow (YY_("memory exhausted"),
+                    &yyss1, yysize * YYSIZEOF (*yyssp),
+                    &yyvs1, yysize * YYSIZEOF (*yyvsp),
+                    &yystacksize);
+        yyss = yyss1;
+        yyvs = yyvs1;
+      }
+# else /* defined YYSTACK_RELOCATE */
+      /* Extend the stack our own way.  */
+      if (YYMAXDEPTH <= yystacksize)
+        goto yyexhaustedlab;
+      yystacksize *= 2;
+      if (YYMAXDEPTH < yystacksize)
+        yystacksize = YYMAXDEPTH;
+
+      {
+        yy_state_t *yyss1 = yyss;
+        union yyalloc *yyptr =
+          YY_CAST (union yyalloc *,
+                   YYSTACK_ALLOC (YY_CAST (YYSIZE_T, YYSTACK_BYTES (yystacksize))));
+        if (! yyptr)
+          goto yyexhaustedlab;
+        YYSTACK_RELOCATE (yyss_alloc, yyss);
+        YYSTACK_RELOCATE (yyvs_alloc, yyvs);
+#  undef YYSTACK_RELOCATE
+        if (yyss1 != yyssa)
+          YYSTACK_FREE (yyss1);
+      }
+# endif
+
+      yyssp = yyss + yysize - 1;
+      yyvsp = yyvs + yysize - 1;
+
+      YY_IGNORE_USELESS_CAST_BEGIN
+      YYDPRINTF ((stderr, "Stack size increased to %ld\n",
+                  YY_CAST (long, yystacksize)));
+      YY_IGNORE_USELESS_CAST_END
+
+      if (yyss + yystacksize - 1 <= yyssp)
+        YYABORT;
+    }
+#endif /* !defined yyoverflow && !defined YYSTACK_RELOCATE */
+
+  if (yystate == YYFINAL)
+    YYACCEPT;
+
+  goto yybackup;
+
+
+/*-----------.
+| yybackup.  |
+`-----------*/
+yybackup:
+  /* Do appropriate processing given the current state.  Read a
+     lookahead token if we need one and don't already have one.  */
+
+  /* First try to decide what to do without reference to lookahead token.  */
+  yyn = yypact[yystate];
+  if (yypact_value_is_default (yyn))
+    goto yydefault;
+
+  /* Not known => get a lookahead token if don't already have one.  */
+
+  /* YYCHAR is either empty, or end-of-input, or a valid lookahead.  */
+  if (yychar == YYEMPTY)
+    {
+      YYDPRINTF ((stderr, "Reading a token\n"));
+      yychar = yylex ();
+    }
+
+  if (yychar <= YYEOF)
+    {
+      yychar = YYEOF;
+      yytoken = YYSYMBOL_YYEOF;
+      YYDPRINTF ((stderr, "Now at end of input.\n"));
+    }
+  else if (yychar == YYerror)
+    {
+      /* The scanner already issued an error message, process directly
+         to error recovery.  But do not keep the error token as
+         lookahead, it is too special and may lead us to an endless
+         loop in error recovery. */
+      yychar = YYUNDEF;
+      yytoken = YYSYMBOL_YYerror;
+      goto yyerrlab1;
+    }
+  else
+    {
+      yytoken = YYTRANSLATE (yychar);
+      YY_SYMBOL_PRINT ("Next token is", yytoken, &yylval, &yylloc);
+    }
+
+  /* If the proper action on seeing token YYTOKEN is to reduce or to
+     detect an error, take that action.  */
+  yyn += yytoken;
+  if (yyn < 0 || YYLAST < yyn || yycheck[yyn] != yytoken)
+    goto yydefault;
+  yyn = yytable[yyn];
+  if (yyn <= 0)
+    {
+      if (yytable_value_is_error (yyn))
+        goto yyerrlab;
+      yyn = -yyn;
+      goto yyreduce;
+    }
+
+  /* Count tokens shifted since error; after three, turn off error
+     status.  */
+  if (yyerrstatus)
+    yyerrstatus--;
+
+  /* Shift the lookahead token.  */
+  YY_SYMBOL_PRINT ("Shifting", yytoken, &yylval, &yylloc);
+  yystate = yyn;
+  YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN
+  *++yyvsp = yylval;
+  YY_IGNORE_MAYBE_UNINITIALIZED_END
+
+  /* Discard the shifted token.  */
+  yychar = YYEMPTY;
+  goto yynewstate;
+
+
+/*-----------------------------------------------------------.
+| yydefault -- do the default action for the current state.  |
+`-----------------------------------------------------------*/
+yydefault:
+  yyn = yydefact[yystate];
+  if (yyn == 0)
+    goto yyerrlab;
+  goto yyreduce;
+
+
+/*-----------------------------.
+| yyreduce -- do a reduction.  |
+`-----------------------------*/
+yyreduce:
+  /* yyn is the number of a rule to reduce with.  */
+  yylen = yyr2[yyn];
+
+  /* If YYLEN is nonzero, implement the default value of the action:
+     '$$ = $1'.
+
+     Otherwise, the following line sets YYVAL to garbage.
+     This behavior is undocumented and Bison
+     users should not rely upon it.  Assigning to YYVAL
+     unconditionally makes the parser a bit smaller, and it avoids a
+     GCC warning that YYVAL may be used uninitialized.  */
+  yyval = yyvsp[1-yylen];
+
+
+  YY_REDUCE_PRINT (yyn);
+  switch (yyn)
+    {
+  case 2: /* firstcmd: command opt_semicolon  */
+#line 108 "repl_gram.y"
+                                {
+					replication_parse_result = (yyvsp[-1].node);
+				}
+#line 1315 "repl_gram.c"
+    break;
+
+  case 13: /* identify_system: K_IDENTIFY_SYSTEM  */
+#line 133 "repl_gram.y"
+                                {
+					(yyval.node) = (Node *) makeNode(IdentifySystemCmd);
+				}
+#line 1323 "repl_gram.c"
+    break;
+
+  case 14: /* show: K_SHOW var_name  */
+#line 143 "repl_gram.y"
+                                {
+					VariableShowStmt *n = makeNode(VariableShowStmt);
+					n->name = (yyvsp[0].str);
+					(yyval.node) = (Node *) n;
+				}
+#line 1333 "repl_gram.c"
+    break;
+
+  case 15: /* var_name: IDENT  */
+#line 149 "repl_gram.y"
+                        { (yyval.str) = (yyvsp[0].str); }
+#line 1339 "repl_gram.c"
+    break;
+
+  case 16: /* var_name: var_name '.' IDENT  */
+#line 151 "repl_gram.y"
+                                { (yyval.str) = psprintf("%s.%s", (yyvsp[-2].str), (yyvsp[0].str)); }
+#line 1345 "repl_gram.c"
+    break;
+
+  case 17: /* base_backup: K_BASE_BACKUP base_backup_opt_list  */
+#line 161 "repl_gram.y"
+                                {
+					BaseBackupCmd *cmd = makeNode(BaseBackupCmd);
+					cmd->options = (yyvsp[0].list);
+					(yyval.node) = (Node *) cmd;
+				}
+#line 1355 "repl_gram.c"
+    break;
+
+  case 18: /* base_backup_opt_list: base_backup_opt_list base_backup_opt  */
+#line 170 "repl_gram.y"
+                                { (yyval.list) = lappend((yyvsp[-1].list), (yyvsp[0].defelt)); }
+#line 1361 "repl_gram.c"
+    break;
+
+  case 19: /* base_backup_opt_list: %empty  */
+#line 172 "repl_gram.y"
+                                { (yyval.list) = NIL; }
+#line 1367 "repl_gram.c"
+    break;
+
+  case 20: /* base_backup_opt: K_LABEL SCONST  */
+#line 177 "repl_gram.y"
+                                {
+				  (yyval.defelt) = makeDefElem("label",
+								   (Node *)makeString((yyvsp[0].str)), -1);
+				}
+#line 1376 "repl_gram.c"
+    break;
+
+  case 21: /* base_backup_opt: K_PROGRESS  */
+#line 182 "repl_gram.y"
+                                {
+				  (yyval.defelt) = makeDefElem("progress",
+								   (Node *)makeInteger(true), -1);
+				}
+#line 1385 "repl_gram.c"
+    break;
+
+  case 22: /* base_backup_opt: K_FAST  */
+#line 187 "repl_gram.y"
+                                {
+				  (yyval.defelt) = makeDefElem("fast",
+								   (Node *)makeInteger(true), -1);
+				}
+#line 1394 "repl_gram.c"
+    break;
+
+  case 23: /* base_backup_opt: K_WAL  */
+#line 192 "repl_gram.y"
+                                {
+				  (yyval.defelt) = makeDefElem("wal",
+								   (Node *)makeInteger(true), -1);
+				}
+#line 1403 "repl_gram.c"
+    break;
+
+  case 24: /* base_backup_opt: K_NOWAIT  */
+#line 197 "repl_gram.y"
+                                {
+				  (yyval.defelt) = makeDefElem("nowait",
+								   (Node *)makeInteger(true), -1);
+				}
+#line 1412 "repl_gram.c"
+    break;
+
+  case 25: /* base_backup_opt: K_MAX_RATE UCONST  */
+#line 202 "repl_gram.y"
+                                {
+				  (yyval.defelt) = makeDefElem("max_rate",
+								   (Node *)makeInteger((yyvsp[0].uintval)), -1);
+				}
+#line 1421 "repl_gram.c"
+    break;
+
+  case 26: /* base_backup_opt: K_TABLESPACE_MAP  */
+#line 207 "repl_gram.y"
+                                {
+				  (yyval.defelt) = makeDefElem("tablespace_map",
+								   (Node *)makeInteger(true), -1);
+				}
+#line 1430 "repl_gram.c"
+    break;
+
+  case 27: /* base_backup_opt: K_NOVERIFY_CHECKSUMS  */
+#line 212 "repl_gram.y"
+                                {
+				  (yyval.defelt) = makeDefElem("noverify_checksums",
+								   (Node *)makeInteger(true), -1);
+				}
+#line 1439 "repl_gram.c"
+    break;
+
+  case 28: /* base_backup_opt: K_MANIFEST SCONST  */
+#line 217 "repl_gram.y"
+                                {
+				  (yyval.defelt) = makeDefElem("manifest",
+								   (Node *)makeString((yyvsp[0].str)), -1);
+				}
+#line 1448 "repl_gram.c"
+    break;
+
+  case 29: /* base_backup_opt: K_MANIFEST_CHECKSUMS SCONST  */
+#line 222 "repl_gram.y"
+                                {
+				  (yyval.defelt) = makeDefElem("manifest_checksums",
+								   (Node *)makeString((yyvsp[0].str)), -1);
+				}
+#line 1457 "repl_gram.c"
+    break;
+
+  case 30: /* create_replication_slot: K_CREATE_REPLICATION_SLOT IDENT opt_temporary K_PHYSICAL create_slot_opt_list  */
+#line 231 "repl_gram.y"
+                                {
+					CreateReplicationSlotCmd *cmd;
+					cmd = makeNode(CreateReplicationSlotCmd);
+					cmd->kind = REPLICATION_KIND_PHYSICAL;
+					cmd->slotname = (yyvsp[-3].str);
+					cmd->temporary = (yyvsp[-2].boolval);
+					cmd->options = (yyvsp[0].list);
+					(yyval.node) = (Node *) cmd;
+				}
+#line 1471 "repl_gram.c"
+    break;
+
+  case 31: /* create_replication_slot: K_CREATE_REPLICATION_SLOT IDENT opt_temporary K_LOGICAL IDENT create_slot_opt_list  */
+#line 242 "repl_gram.y"
+                                {
+					CreateReplicationSlotCmd *cmd;
+					cmd = makeNode(CreateReplicationSlotCmd);
+					cmd->kind = REPLICATION_KIND_LOGICAL;
+					cmd->slotname = (yyvsp[-4].str);
+					cmd->temporary = (yyvsp[-3].boolval);
+					cmd->plugin = (yyvsp[-1].str);
+					cmd->options = (yyvsp[0].list);
+					(yyval.node) = (Node *) cmd;
+				}
+#line 1486 "repl_gram.c"
+    break;
+
+  case 32: /* create_slot_opt_list: create_slot_opt_list create_slot_opt  */
+#line 256 "repl_gram.y"
+                                { (yyval.list) = lappend((yyvsp[-1].list), (yyvsp[0].defelt)); }
+#line 1492 "repl_gram.c"
+    break;
+
+  case 33: /* create_slot_opt_list: %empty  */
+#line 258 "repl_gram.y"
+                                { (yyval.list) = NIL; }
+#line 1498 "repl_gram.c"
+    break;
+
+  case 34: /* create_slot_opt: K_EXPORT_SNAPSHOT  */
+#line 263 "repl_gram.y"
+                                {
+				  (yyval.defelt) = makeDefElem("export_snapshot",
+								   (Node *)makeInteger(true), -1);
+				}
+#line 1507 "repl_gram.c"
+    break;
+
+  case 35: /* create_slot_opt: K_NOEXPORT_SNAPSHOT  */
+#line 268 "repl_gram.y"
+                                {
+				  (yyval.defelt) = makeDefElem("export_snapshot",
+								   (Node *)makeInteger(false), -1);
+				}
+#line 1516 "repl_gram.c"
+    break;
+
+  case 36: /* create_slot_opt: K_USE_SNAPSHOT  */
+#line 273 "repl_gram.y"
+                                {
+				  (yyval.defelt) = makeDefElem("use_snapshot",
+								   (Node *)makeInteger(true), -1);
+				}
+#line 1525 "repl_gram.c"
+    break;
+
+  case 37: /* create_slot_opt: K_RESERVE_WAL  */
+#line 278 "repl_gram.y"
+                                {
+				  (yyval.defelt) = makeDefElem("reserve_wal",
+								   (Node *)makeInteger(true), -1);
+				}
+#line 1534 "repl_gram.c"
+    break;
+
+  case 38: /* drop_replication_slot: K_DROP_REPLICATION_SLOT IDENT  */
+#line 287 "repl_gram.y"
+                                {
+					DropReplicationSlotCmd *cmd;
+					cmd = makeNode(DropReplicationSlotCmd);
+					cmd->slotname = (yyvsp[0].str);
+					cmd->wait = false;
+					(yyval.node) = (Node *) cmd;
+				}
+#line 1546 "repl_gram.c"
+    break;
+
+  case 39: /* drop_replication_slot: K_DROP_REPLICATION_SLOT IDENT K_WAIT  */
+#line 295 "repl_gram.y"
+                                {
+					DropReplicationSlotCmd *cmd;
+					cmd = makeNode(DropReplicationSlotCmd);
+					cmd->slotname = (yyvsp[-1].str);
+					cmd->wait = true;
+					(yyval.node) = (Node *) cmd;
+				}
+#line 1558 "repl_gram.c"
+    break;
+
+  case 40: /* start_replication: K_START_REPLICATION opt_slot opt_physical RECPTR opt_timeline  */
+#line 309 "repl_gram.y"
+                                {
+					StartReplicationCmd *cmd;
+
+					cmd = makeNode(StartReplicationCmd);
+					cmd->kind = REPLICATION_KIND_PHYSICAL;
+					cmd->slotname = (yyvsp[-3].str);
+					cmd->startpoint = (yyvsp[-1].recptr);
+					cmd->timeline = (yyvsp[0].uintval);
+					(yyval.node) = (Node *) cmd;
+				}
+#line 1573 "repl_gram.c"
+    break;
+
+  case 41: /* start_logical_replication: K_START_REPLICATION K_SLOT IDENT K_LOGICAL RECPTR plugin_options  */
+#line 324 "repl_gram.y"
+                                {
+					StartReplicationCmd *cmd;
+					cmd = makeNode(StartReplicationCmd);
+					cmd->kind = REPLICATION_KIND_LOGICAL;
+					cmd->slotname = (yyvsp[-3].str);
+					cmd->startpoint = (yyvsp[-1].recptr);
+					cmd->options = (yyvsp[0].list);
+					(yyval.node) = (Node *) cmd;
+				}
+#line 1587 "repl_gram.c"
+    break;
+
+  case 42: /* timeline_history: K_TIMELINE_HISTORY UCONST  */
+#line 339 "repl_gram.y"
+                                {
+					TimeLineHistoryCmd *cmd;
+
+					if ((yyvsp[0].uintval) <= 0)
+						ereport(ERROR,
+								(errcode(ERRCODE_SYNTAX_ERROR),
+								 errmsg("invalid timeline %u", (yyvsp[0].uintval))));
+
+					cmd = makeNode(TimeLineHistoryCmd);
+					cmd->timeline = (yyvsp[0].uintval);
+
+					(yyval.node) = (Node *) cmd;
+				}
+#line 1605 "repl_gram.c"
+    break;
+
+  case 45: /* opt_temporary: K_TEMPORARY  */
+#line 360 "repl_gram.y"
+                                                                                { (yyval.boolval) = true; }
+#line 1611 "repl_gram.c"
+    break;
+
+  case 46: /* opt_temporary: %empty  */
+#line 361 "repl_gram.y"
+                                                                        { (yyval.boolval) = false; }
+#line 1617 "repl_gram.c"
+    break;
+
+  case 47: /* opt_slot: K_SLOT IDENT  */
+#line 366 "repl_gram.y"
+                                { (yyval.str) = (yyvsp[0].str); }
+#line 1623 "repl_gram.c"
+    break;
+
+  case 48: /* opt_slot: %empty  */
+#line 368 "repl_gram.y"
+                                { (yyval.str) = NULL; }
+#line 1629 "repl_gram.c"
+    break;
+
+  case 49: /* opt_timeline: K_TIMELINE UCONST  */
+#line 373 "repl_gram.y"
+                                {
+					if ((yyvsp[0].uintval) <= 0)
+						ereport(ERROR,
+								(errcode(ERRCODE_SYNTAX_ERROR),
+								 errmsg("invalid timeline %u", (yyvsp[0].uintval))));
+					(yyval.uintval) = (yyvsp[0].uintval);
+				}
+#line 1641 "repl_gram.c"
+    break;
+
+  case 50: /* opt_timeline: %empty  */
+#line 380 "repl_gram.y"
+                                                                { (yyval.uintval) = 0; }
+#line 1647 "repl_gram.c"
+    break;
+
+  case 51: /* plugin_options: '(' plugin_opt_list ')'  */
+#line 385 "repl_gram.y"
+                                                                { (yyval.list) = (yyvsp[-1].list); }
+#line 1653 "repl_gram.c"
+    break;
+
+  case 52: /* plugin_options: %empty  */
+#line 386 "repl_gram.y"
+                                                                        { (yyval.list) = NIL; }
+#line 1659 "repl_gram.c"
+    break;
+
+  case 53: /* plugin_opt_list: plugin_opt_elem  */
+#line 391 "repl_gram.y"
+                                {
+					(yyval.list) = list_make1((yyvsp[0].defelt));
+				}
+#line 1667 "repl_gram.c"
+    break;
+
+  case 54: /* plugin_opt_list: plugin_opt_list ',' plugin_opt_elem  */
+#line 395 "repl_gram.y"
+                                {
+					(yyval.list) = lappend((yyvsp[-2].list), (yyvsp[0].defelt));
+				}
+#line 1675 "repl_gram.c"
+    break;
+
+  case 55: /* plugin_opt_elem: IDENT plugin_opt_arg  */
+#line 402 "repl_gram.y"
+                                {
+					(yyval.defelt) = makeDefElem((yyvsp[-1].str), (yyvsp[0].node), -1);
+				}
+#line 1683 "repl_gram.c"
+    break;
+
+  case 56: /* plugin_opt_arg: SCONST  */
+#line 408 "repl_gram.y"
+                                                                                { (yyval.node) = (Node *) makeString((yyvsp[0].str)); }
+#line 1689 "repl_gram.c"
+    break;
+
+  case 57: /* plugin_opt_arg: %empty  */
+#line 409 "repl_gram.y"
+                                                                        { (yyval.node) = NULL; }
+#line 1695 "repl_gram.c"
+    break;
+
+
+#line 1699 "repl_gram.c"
+
+      default: break;
+    }
+  /* User semantic actions sometimes alter yychar, and that requires
+     that yytoken be updated with the new translation.  We take the
+     approach of translating immediately before every use of yytoken.
+     One alternative is translating here after every semantic action,
+     but that translation would be missed if the semantic action invokes
+     YYABORT, YYACCEPT, or YYERROR immediately after altering yychar or
+     if it invokes YYBACKUP.  In the case of YYABORT or YYACCEPT, an
+     incorrect destructor might then be invoked immediately.  In the
+     case of YYERROR or YYBACKUP, subsequent parser actions might lead
+     to an incorrect destructor call or verbose syntax error message
+     before the lookahead is translated.  */
+  YY_SYMBOL_PRINT ("-> $$ =", YY_CAST (yysymbol_kind_t, yyr1[yyn]), &yyval, &yyloc);
+
+  YYPOPSTACK (yylen);
+  yylen = 0;
+
+  *++yyvsp = yyval;
+
+  /* Now 'shift' the result of the reduction.  Determine what state
+     that goes to, based on the state we popped back to and the rule
+     number reduced by.  */
+  {
+    const int yylhs = yyr1[yyn] - YYNTOKENS;
+    const int yyi = yypgoto[yylhs] + *yyssp;
+    yystate = (0 <= yyi && yyi <= YYLAST && yycheck[yyi] == *yyssp
+               ? yytable[yyi]
+               : yydefgoto[yylhs]);
+  }
+
+  goto yynewstate;
+
+
+/*--------------------------------------.
+| yyerrlab -- here on detecting error.  |
+`--------------------------------------*/
+yyerrlab:
+  /* Make sure we have latest lookahead translation.  See comments at
+     user semantic actions for why this is necessary.  */
+  yytoken = yychar == YYEMPTY ? YYSYMBOL_YYEMPTY : YYTRANSLATE (yychar);
+  /* If not already recovering from an error, report this error.  */
+  if (!yyerrstatus)
+    {
+      ++yynerrs;
+      yyerror (YY_("syntax error"));
+    }
+
+  if (yyerrstatus == 3)
+    {
+      /* If just tried and failed to reuse lookahead token after an
+         error, discard it.  */
+
+      if (yychar <= YYEOF)
+        {
+          /* Return failure if at end of input.  */
+          if (yychar == YYEOF)
+            YYABORT;
+        }
+      else
+        {
+          yydestruct ("Error: discarding",
+                      yytoken, &yylval);
+          yychar = YYEMPTY;
+        }
+    }
+
+  /* Else will try to reuse lookahead token after shifting the error
+     token.  */
+  goto yyerrlab1;
+
+
+/*---------------------------------------------------.
+| yyerrorlab -- error raised explicitly by YYERROR.  |
+`---------------------------------------------------*/
+yyerrorlab:
+  /* Pacify compilers when the user code never invokes YYERROR and the
+     label yyerrorlab therefore never appears in user code.  */
+  if (0)
+    YYERROR;
+
+  /* Do not reclaim the symbols of the rule whose action triggered
+     this YYERROR.  */
+  YYPOPSTACK (yylen);
+  yylen = 0;
+  YY_STACK_PRINT (yyss, yyssp);
+  yystate = *yyssp;
+  goto yyerrlab1;
+
+
+/*-------------------------------------------------------------.
+| yyerrlab1 -- common code for both syntax error and YYERROR.  |
+`-------------------------------------------------------------*/
+yyerrlab1:
+  yyerrstatus = 3;      /* Each real token shifted decrements this.  */
+
+  /* Pop stack until we find a state that shifts the error token.  */
+  for (;;)
+    {
+      yyn = yypact[yystate];
+      if (!yypact_value_is_default (yyn))
+        {
+          yyn += YYSYMBOL_YYerror;
+          if (0 <= yyn && yyn <= YYLAST && yycheck[yyn] == YYSYMBOL_YYerror)
+            {
+              yyn = yytable[yyn];
+              if (0 < yyn)
+                break;
+            }
+        }
+
+      /* Pop the current state because it cannot handle the error token.  */
+      if (yyssp == yyss)
+        YYABORT;
+
+
+      yydestruct ("Error: popping",
+                  YY_ACCESSING_SYMBOL (yystate), yyvsp);
+      YYPOPSTACK (1);
+      yystate = *yyssp;
+      YY_STACK_PRINT (yyss, yyssp);
+    }
+
+  YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN
+  *++yyvsp = yylval;
+  YY_IGNORE_MAYBE_UNINITIALIZED_END
+
+
+  /* Shift the error token.  */
+  YY_SYMBOL_PRINT ("Shifting", YY_ACCESSING_SYMBOL (yyn), yyvsp, yylsp);
+
+  yystate = yyn;
+  goto yynewstate;
+
+
+/*-------------------------------------.
+| yyacceptlab -- YYACCEPT comes here.  |
+`-------------------------------------*/
+yyacceptlab:
+  yyresult = 0;
+  goto yyreturn;
+
+
+/*-----------------------------------.
+| yyabortlab -- YYABORT comes here.  |
+`-----------------------------------*/
+yyabortlab:
+  yyresult = 1;
+  goto yyreturn;
+
+
+#if !defined yyoverflow
+/*-------------------------------------------------.
+| yyexhaustedlab -- memory exhaustion comes here.  |
+`-------------------------------------------------*/
+yyexhaustedlab:
+  yyerror (YY_("memory exhausted"));
+  yyresult = 2;
+  goto yyreturn;
+#endif
+
+
+/*-------------------------------------------------------.
+| yyreturn -- parsing is finished, clean up and return.  |
+`-------------------------------------------------------*/
+yyreturn:
+  if (yychar != YYEMPTY)
+    {
+      /* Make sure we have latest lookahead translation.  See comments at
+         user semantic actions for why this is necessary.  */
+      yytoken = YYTRANSLATE (yychar);
+      yydestruct ("Cleanup: discarding lookahead",
+                  yytoken, &yylval);
+    }
+  /* Do not reclaim the symbols of the rule whose action triggered
+     this YYABORT or YYACCEPT.  */
+  YYPOPSTACK (yylen);
+  YY_STACK_PRINT (yyss, yyssp);
+  while (yyssp != yyss)
+    {
+      yydestruct ("Cleanup: popping",
+                  YY_ACCESSING_SYMBOL (+*yyssp), yyvsp);
+      YYPOPSTACK (1);
+    }
+#ifndef yyoverflow
+  if (yyss != yyssa)
+    YYSTACK_FREE (yyss);
+#endif
+
+  return yyresult;
+}
+
+#line 412 "repl_gram.y"
+
+
+#include "repl_scanner.c"
diff --git a/src/backend/replication/repl_gram.y b/src/backend/replication/repl_gram.y
new file mode 100644
index 0000000..802c0ad
--- /dev/null
+++ b/src/backend/replication/repl_gram.y
@@ -0,0 +1,414 @@
+%{
+/*-------------------------------------------------------------------------
+ *
+ * repl_gram.y				- Parser for the replication commands
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/repl_gram.y
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/xlogdefs.h"
+#include "nodes/makefuncs.h"
+#include "nodes/replnodes.h"
+#include "replication/walsender.h"
+#include "replication/walsender_private.h"
+
+
+/* Result of the parsing is returned here */
+Node *replication_parse_result;
+
+
+/*
+ * Bison doesn't allocate anything that needs to live across parser calls,
+ * so we can easily have it use palloc instead of malloc.  This prevents
+ * memory leaks if we error out during parsing.  Note this only works with
+ * bison >= 2.0.  However, in bison 1.875 the default is to use alloca()
+ * if possible, so there's not really much problem anyhow, at least if
+ * you're building with gcc.
+ */
+#define YYMALLOC palloc
+#define YYFREE   pfree
+
+%}
+
+%expect 0
+%name-prefix="replication_yy"
+
+%union {
+		char					*str;
+		bool					boolval;
+		uint32					uintval;
+
+		XLogRecPtr				recptr;
+		Node					*node;
+		List					*list;
+		DefElem					*defelt;
+}
+
+/* Non-keyword tokens */
+%token <str> SCONST IDENT
+%token <uintval> UCONST
+%token <recptr> RECPTR
+
+/* Keyword tokens. */
+%token K_BASE_BACKUP
+%token K_IDENTIFY_SYSTEM
+%token K_SHOW
+%token K_START_REPLICATION
+%token K_CREATE_REPLICATION_SLOT
+%token K_DROP_REPLICATION_SLOT
+%token K_TIMELINE_HISTORY
+%token K_LABEL
+%token K_PROGRESS
+%token K_FAST
+%token K_WAIT
+%token K_NOWAIT
+%token K_MAX_RATE
+%token K_WAL
+%token K_TABLESPACE_MAP
+%token K_NOVERIFY_CHECKSUMS
+%token K_TIMELINE
+%token K_PHYSICAL
+%token K_LOGICAL
+%token K_SLOT
+%token K_RESERVE_WAL
+%token K_TEMPORARY
+%token K_EXPORT_SNAPSHOT
+%token K_NOEXPORT_SNAPSHOT
+%token K_USE_SNAPSHOT
+%token K_MANIFEST
+%token K_MANIFEST_CHECKSUMS
+
+%type <node>	command
+%type <node>	base_backup start_replication start_logical_replication
+				create_replication_slot drop_replication_slot identify_system
+				timeline_history show
+%type <list>	base_backup_opt_list
+%type <defelt>	base_backup_opt
+%type <uintval>	opt_timeline
+%type <list>	plugin_options plugin_opt_list
+%type <defelt>	plugin_opt_elem
+%type <node>	plugin_opt_arg
+%type <str>		opt_slot var_name
+%type <boolval>	opt_temporary
+%type <list>	create_slot_opt_list
+%type <defelt>	create_slot_opt
+
+%%
+
+firstcmd: command opt_semicolon
+				{
+					replication_parse_result = $1;
+				}
+			;
+
+opt_semicolon:	';'
+				| /* EMPTY */
+				;
+
+command:
+			identify_system
+			| base_backup
+			| start_replication
+			| start_logical_replication
+			| create_replication_slot
+			| drop_replication_slot
+			| timeline_history
+			| show
+			;
+
+/*
+ * IDENTIFY_SYSTEM
+ */
+identify_system:
+			K_IDENTIFY_SYSTEM
+				{
+					$$ = (Node *) makeNode(IdentifySystemCmd);
+				}
+			;
+
+/*
+ * SHOW setting
+ */
+show:
+			K_SHOW var_name
+				{
+					VariableShowStmt *n = makeNode(VariableShowStmt);
+					n->name = $2;
+					$$ = (Node *) n;
+				}
+
+var_name:	IDENT	{ $$ = $1; }
+			| var_name '.' IDENT
+				{ $$ = psprintf("%s.%s", $1, $3); }
+		;
+
+/*
+ * BASE_BACKUP [LABEL '<label>'] [PROGRESS] [FAST] [WAL] [NOWAIT]
+ * [MAX_RATE %d] [TABLESPACE_MAP] [NOVERIFY_CHECKSUMS]
+ * [MANIFEST %s] [MANIFEST_CHECKSUMS %s]
+ */
+base_backup:
+			K_BASE_BACKUP base_backup_opt_list
+				{
+					BaseBackupCmd *cmd = makeNode(BaseBackupCmd);
+					cmd->options = $2;
+					$$ = (Node *) cmd;
+				}
+			;
+
+base_backup_opt_list:
+			base_backup_opt_list base_backup_opt
+				{ $$ = lappend($1, $2); }
+			| /* EMPTY */
+				{ $$ = NIL; }
+			;
+
+base_backup_opt:
+			K_LABEL SCONST
+				{
+				  $$ = makeDefElem("label",
+								   (Node *)makeString($2), -1);
+				}
+			| K_PROGRESS
+				{
+				  $$ = makeDefElem("progress",
+								   (Node *)makeInteger(true), -1);
+				}
+			| K_FAST
+				{
+				  $$ = makeDefElem("fast",
+								   (Node *)makeInteger(true), -1);
+				}
+			| K_WAL
+				{
+				  $$ = makeDefElem("wal",
+								   (Node *)makeInteger(true), -1);
+				}
+			| K_NOWAIT
+				{
+				  $$ = makeDefElem("nowait",
+								   (Node *)makeInteger(true), -1);
+				}
+			| K_MAX_RATE UCONST
+				{
+				  $$ = makeDefElem("max_rate",
+								   (Node *)makeInteger($2), -1);
+				}
+			| K_TABLESPACE_MAP
+				{
+				  $$ = makeDefElem("tablespace_map",
+								   (Node *)makeInteger(true), -1);
+				}
+			| K_NOVERIFY_CHECKSUMS
+				{
+				  $$ = makeDefElem("noverify_checksums",
+								   (Node *)makeInteger(true), -1);
+				}
+			| K_MANIFEST SCONST
+				{
+				  $$ = makeDefElem("manifest",
+								   (Node *)makeString($2), -1);
+				}
+			| K_MANIFEST_CHECKSUMS SCONST
+				{
+				  $$ = makeDefElem("manifest_checksums",
+								   (Node *)makeString($2), -1);
+				}
+			;
+
+create_replication_slot:
+			/* CREATE_REPLICATION_SLOT slot TEMPORARY PHYSICAL RESERVE_WAL */
+			K_CREATE_REPLICATION_SLOT IDENT opt_temporary K_PHYSICAL create_slot_opt_list
+				{
+					CreateReplicationSlotCmd *cmd;
+					cmd = makeNode(CreateReplicationSlotCmd);
+					cmd->kind = REPLICATION_KIND_PHYSICAL;
+					cmd->slotname = $2;
+					cmd->temporary = $3;
+					cmd->options = $5;
+					$$ = (Node *) cmd;
+				}
+			/* CREATE_REPLICATION_SLOT slot TEMPORARY LOGICAL plugin */
+			| K_CREATE_REPLICATION_SLOT IDENT opt_temporary K_LOGICAL IDENT create_slot_opt_list
+				{
+					CreateReplicationSlotCmd *cmd;
+					cmd = makeNode(CreateReplicationSlotCmd);
+					cmd->kind = REPLICATION_KIND_LOGICAL;
+					cmd->slotname = $2;
+					cmd->temporary = $3;
+					cmd->plugin = $5;
+					cmd->options = $6;
+					$$ = (Node *) cmd;
+				}
+			;
+
+create_slot_opt_list:
+			create_slot_opt_list create_slot_opt
+				{ $$ = lappend($1, $2); }
+			| /* EMPTY */
+				{ $$ = NIL; }
+			;
+
+create_slot_opt:
+			K_EXPORT_SNAPSHOT
+				{
+				  $$ = makeDefElem("export_snapshot",
+								   (Node *)makeInteger(true), -1);
+				}
+			| K_NOEXPORT_SNAPSHOT
+				{
+				  $$ = makeDefElem("export_snapshot",
+								   (Node *)makeInteger(false), -1);
+				}
+			| K_USE_SNAPSHOT
+				{
+				  $$ = makeDefElem("use_snapshot",
+								   (Node *)makeInteger(true), -1);
+				}
+			| K_RESERVE_WAL
+				{
+				  $$ = makeDefElem("reserve_wal",
+								   (Node *)makeInteger(true), -1);
+				}
+			;
+
+/* DROP_REPLICATION_SLOT slot */
+drop_replication_slot:
+			K_DROP_REPLICATION_SLOT IDENT
+				{
+					DropReplicationSlotCmd *cmd;
+					cmd = makeNode(DropReplicationSlotCmd);
+					cmd->slotname = $2;
+					cmd->wait = false;
+					$$ = (Node *) cmd;
+				}
+			| K_DROP_REPLICATION_SLOT IDENT K_WAIT
+				{
+					DropReplicationSlotCmd *cmd;
+					cmd = makeNode(DropReplicationSlotCmd);
+					cmd->slotname = $2;
+					cmd->wait = true;
+					$$ = (Node *) cmd;
+				}
+			;
+
+/*
+ * START_REPLICATION [SLOT slot] [PHYSICAL] %X/%X [TIMELINE %d]
+ */
+start_replication:
+			K_START_REPLICATION opt_slot opt_physical RECPTR opt_timeline
+				{
+					StartReplicationCmd *cmd;
+
+					cmd = makeNode(StartReplicationCmd);
+					cmd->kind = REPLICATION_KIND_PHYSICAL;
+					cmd->slotname = $2;
+					cmd->startpoint = $4;
+					cmd->timeline = $5;
+					$$ = (Node *) cmd;
+				}
+			;
+
+/* START_REPLICATION SLOT slot LOGICAL %X/%X options */
+start_logical_replication:
+			K_START_REPLICATION K_SLOT IDENT K_LOGICAL RECPTR plugin_options
+				{
+					StartReplicationCmd *cmd;
+					cmd = makeNode(StartReplicationCmd);
+					cmd->kind = REPLICATION_KIND_LOGICAL;
+					cmd->slotname = $3;
+					cmd->startpoint = $5;
+					cmd->options = $6;
+					$$ = (Node *) cmd;
+				}
+			;
+/*
+ * TIMELINE_HISTORY %d
+ */
+timeline_history:
+			K_TIMELINE_HISTORY UCONST
+				{
+					TimeLineHistoryCmd *cmd;
+
+					if ($2 <= 0)
+						ereport(ERROR,
+								(errcode(ERRCODE_SYNTAX_ERROR),
+								 errmsg("invalid timeline %u", $2)));
+
+					cmd = makeNode(TimeLineHistoryCmd);
+					cmd->timeline = $2;
+
+					$$ = (Node *) cmd;
+				}
+			;
+
+opt_physical:
+			K_PHYSICAL
+			| /* EMPTY */
+			;
+
+opt_temporary:
+			K_TEMPORARY						{ $$ = true; }
+			| /* EMPTY */					{ $$ = false; }
+			;
+
+opt_slot:
+			K_SLOT IDENT
+				{ $$ = $2; }
+			| /* EMPTY */
+				{ $$ = NULL; }
+			;
+
+opt_timeline:
+			K_TIMELINE UCONST
+				{
+					if ($2 <= 0)
+						ereport(ERROR,
+								(errcode(ERRCODE_SYNTAX_ERROR),
+								 errmsg("invalid timeline %u", $2)));
+					$$ = $2;
+				}
+				| /* EMPTY */			{ $$ = 0; }
+			;
+
+
+plugin_options:
+			'(' plugin_opt_list ')'			{ $$ = $2; }
+			| /* EMPTY */					{ $$ = NIL; }
+		;
+
+plugin_opt_list:
+			plugin_opt_elem
+				{
+					$$ = list_make1($1);
+				}
+			| plugin_opt_list ',' plugin_opt_elem
+				{
+					$$ = lappend($1, $3);
+				}
+		;
+
+plugin_opt_elem:
+			IDENT plugin_opt_arg
+				{
+					$$ = makeDefElem($1, $2, -1);
+				}
+		;
+
+plugin_opt_arg:
+			SCONST							{ $$ = (Node *) makeString($1); }
+			| /* EMPTY */					{ $$ = NULL; }
+		;
+
+%%
+
+#include "repl_scanner.c"
diff --git a/src/backend/replication/repl_scanner.c b/src/backend/replication/repl_scanner.c
new file mode 100644
index 0000000..1139cec
--- /dev/null
+++ b/src/backend/replication/repl_scanner.c
@@ -0,0 +1,2615 @@
+#line 2 "repl_scanner.c"
+
+#line 4 "repl_scanner.c"
+
+#define  YY_INT_ALIGNED short int
+
+/* A lexical scanner generated by flex */
+
+#define yy_create_buffer replication_yy_create_buffer
+#define yy_delete_buffer replication_yy_delete_buffer
+#define yy_scan_buffer replication_yy_scan_buffer
+#define yy_scan_string replication_yy_scan_string
+#define yy_scan_bytes replication_yy_scan_bytes
+#define yy_init_buffer replication_yy_init_buffer
+#define yy_flush_buffer replication_yy_flush_buffer
+#define yy_load_buffer_state replication_yy_load_buffer_state
+#define yy_switch_to_buffer replication_yy_switch_to_buffer
+#define yypush_buffer_state replication_yypush_buffer_state
+#define yypop_buffer_state replication_yypop_buffer_state
+#define yyensure_buffer_stack replication_yyensure_buffer_stack
+#define yy_flex_debug replication_yy_flex_debug
+#define yyin replication_yyin
+#define yyleng replication_yyleng
+#define yylex replication_yylex
+#define yylineno replication_yylineno
+#define yyout replication_yyout
+#define yyrestart replication_yyrestart
+#define yytext replication_yytext
+#define yywrap replication_yywrap
+#define yyalloc replication_yyalloc
+#define yyrealloc replication_yyrealloc
+#define yyfree replication_yyfree
+
+#define FLEX_SCANNER
+#define YY_FLEX_MAJOR_VERSION 2
+#define YY_FLEX_MINOR_VERSION 6
+#define YY_FLEX_SUBMINOR_VERSION 4
+#if YY_FLEX_SUBMINOR_VERSION > 0
+#define FLEX_BETA
+#endif
+
+#ifdef yy_create_buffer
+#define replication_yy_create_buffer_ALREADY_DEFINED
+#else
+#define yy_create_buffer replication_yy_create_buffer
+#endif
+
+#ifdef yy_delete_buffer
+#define replication_yy_delete_buffer_ALREADY_DEFINED
+#else
+#define yy_delete_buffer replication_yy_delete_buffer
+#endif
+
+#ifdef yy_scan_buffer
+#define replication_yy_scan_buffer_ALREADY_DEFINED
+#else
+#define yy_scan_buffer replication_yy_scan_buffer
+#endif
+
+#ifdef yy_scan_string
+#define replication_yy_scan_string_ALREADY_DEFINED
+#else
+#define yy_scan_string replication_yy_scan_string
+#endif
+
+#ifdef yy_scan_bytes
+#define replication_yy_scan_bytes_ALREADY_DEFINED
+#else
+#define yy_scan_bytes replication_yy_scan_bytes
+#endif
+
+#ifdef yy_init_buffer
+#define replication_yy_init_buffer_ALREADY_DEFINED
+#else
+#define yy_init_buffer replication_yy_init_buffer
+#endif
+
+#ifdef yy_flush_buffer
+#define replication_yy_flush_buffer_ALREADY_DEFINED
+#else
+#define yy_flush_buffer replication_yy_flush_buffer
+#endif
+
+#ifdef yy_load_buffer_state
+#define replication_yy_load_buffer_state_ALREADY_DEFINED
+#else
+#define yy_load_buffer_state replication_yy_load_buffer_state
+#endif
+
+#ifdef yy_switch_to_buffer
+#define replication_yy_switch_to_buffer_ALREADY_DEFINED
+#else
+#define yy_switch_to_buffer replication_yy_switch_to_buffer
+#endif
+
+#ifdef yypush_buffer_state
+#define replication_yypush_buffer_state_ALREADY_DEFINED
+#else
+#define yypush_buffer_state replication_yypush_buffer_state
+#endif
+
+#ifdef yypop_buffer_state
+#define replication_yypop_buffer_state_ALREADY_DEFINED
+#else
+#define yypop_buffer_state replication_yypop_buffer_state
+#endif
+
+#ifdef yyensure_buffer_stack
+#define replication_yyensure_buffer_stack_ALREADY_DEFINED
+#else
+#define yyensure_buffer_stack replication_yyensure_buffer_stack
+#endif
+
+#ifdef yylex
+#define replication_yylex_ALREADY_DEFINED
+#else
+#define yylex replication_yylex
+#endif
+
+#ifdef yyrestart
+#define replication_yyrestart_ALREADY_DEFINED
+#else
+#define yyrestart replication_yyrestart
+#endif
+
+#ifdef yylex_init
+#define replication_yylex_init_ALREADY_DEFINED
+#else
+#define yylex_init replication_yylex_init
+#endif
+
+#ifdef yylex_init_extra
+#define replication_yylex_init_extra_ALREADY_DEFINED
+#else
+#define yylex_init_extra replication_yylex_init_extra
+#endif
+
+#ifdef yylex_destroy
+#define replication_yylex_destroy_ALREADY_DEFINED
+#else
+#define yylex_destroy replication_yylex_destroy
+#endif
+
+#ifdef yyget_debug
+#define replication_yyget_debug_ALREADY_DEFINED
+#else
+#define yyget_debug replication_yyget_debug
+#endif
+
+#ifdef yyset_debug
+#define replication_yyset_debug_ALREADY_DEFINED
+#else
+#define yyset_debug replication_yyset_debug
+#endif
+
+#ifdef yyget_extra
+#define replication_yyget_extra_ALREADY_DEFINED
+#else
+#define yyget_extra replication_yyget_extra
+#endif
+
+#ifdef yyset_extra
+#define replication_yyset_extra_ALREADY_DEFINED
+#else
+#define yyset_extra replication_yyset_extra
+#endif
+
+#ifdef yyget_in
+#define replication_yyget_in_ALREADY_DEFINED
+#else
+#define yyget_in replication_yyget_in
+#endif
+
+#ifdef yyset_in
+#define replication_yyset_in_ALREADY_DEFINED
+#else
+#define yyset_in replication_yyset_in
+#endif
+
+#ifdef yyget_out
+#define replication_yyget_out_ALREADY_DEFINED
+#else
+#define yyget_out replication_yyget_out
+#endif
+
+#ifdef yyset_out
+#define replication_yyset_out_ALREADY_DEFINED
+#else
+#define yyset_out replication_yyset_out
+#endif
+
+#ifdef yyget_leng
+#define replication_yyget_leng_ALREADY_DEFINED
+#else
+#define yyget_leng replication_yyget_leng
+#endif
+
+#ifdef yyget_text
+#define replication_yyget_text_ALREADY_DEFINED
+#else
+#define yyget_text replication_yyget_text
+#endif
+
+#ifdef yyget_lineno
+#define replication_yyget_lineno_ALREADY_DEFINED
+#else
+#define yyget_lineno replication_yyget_lineno
+#endif
+
+#ifdef yyset_lineno
+#define replication_yyset_lineno_ALREADY_DEFINED
+#else
+#define yyset_lineno replication_yyset_lineno
+#endif
+
+#ifdef yywrap
+#define replication_yywrap_ALREADY_DEFINED
+#else
+#define yywrap replication_yywrap
+#endif
+
+#ifdef yyalloc
+#define replication_yyalloc_ALREADY_DEFINED
+#else
+#define yyalloc replication_yyalloc
+#endif
+
+#ifdef yyrealloc
+#define replication_yyrealloc_ALREADY_DEFINED
+#else
+#define yyrealloc replication_yyrealloc
+#endif
+
+#ifdef yyfree
+#define replication_yyfree_ALREADY_DEFINED
+#else
+#define yyfree replication_yyfree
+#endif
+
+#ifdef yytext
+#define replication_yytext_ALREADY_DEFINED
+#else
+#define yytext replication_yytext
+#endif
+
+#ifdef yyleng
+#define replication_yyleng_ALREADY_DEFINED
+#else
+#define yyleng replication_yyleng
+#endif
+
+#ifdef yyin
+#define replication_yyin_ALREADY_DEFINED
+#else
+#define yyin replication_yyin
+#endif
+
+#ifdef yyout
+#define replication_yyout_ALREADY_DEFINED
+#else
+#define yyout replication_yyout
+#endif
+
+#ifdef yy_flex_debug
+#define replication_yy_flex_debug_ALREADY_DEFINED
+#else
+#define yy_flex_debug replication_yy_flex_debug
+#endif
+
+#ifdef yylineno
+#define replication_yylineno_ALREADY_DEFINED
+#else
+#define yylineno replication_yylineno
+#endif
+
+/* First, we deal with  platform-specific or compiler-specific issues. */
+
+/* begin standard C headers. */
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <stdlib.h>
+
+/* end standard C headers. */
+
+/* flex integer type definitions */
+
+#ifndef FLEXINT_H
+#define FLEXINT_H
+
+/* C99 systems have <inttypes.h>. Non-C99 systems may or may not. */
+
+#if defined (__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
+
+/* C99 says to define __STDC_LIMIT_MACROS before including stdint.h,
+ * if you want the limit (max/min) macros for int types. 
+ */
+#ifndef __STDC_LIMIT_MACROS
+#define __STDC_LIMIT_MACROS 1
+#endif
+
+#include <inttypes.h>
+typedef int8_t flex_int8_t;
+typedef uint8_t flex_uint8_t;
+typedef int16_t flex_int16_t;
+typedef uint16_t flex_uint16_t;
+typedef int32_t flex_int32_t;
+typedef uint32_t flex_uint32_t;
+#else
+typedef signed char flex_int8_t;
+typedef short int flex_int16_t;
+typedef int flex_int32_t;
+typedef unsigned char flex_uint8_t; 
+typedef unsigned short int flex_uint16_t;
+typedef unsigned int flex_uint32_t;
+
+/* Limits of integral types. */
+#ifndef INT8_MIN
+#define INT8_MIN               (-128)
+#endif
+#ifndef INT16_MIN
+#define INT16_MIN              (-32767-1)
+#endif
+#ifndef INT32_MIN
+#define INT32_MIN              (-2147483647-1)
+#endif
+#ifndef INT8_MAX
+#define INT8_MAX               (127)
+#endif
+#ifndef INT16_MAX
+#define INT16_MAX              (32767)
+#endif
+#ifndef INT32_MAX
+#define INT32_MAX              (2147483647)
+#endif
+#ifndef UINT8_MAX
+#define UINT8_MAX              (255U)
+#endif
+#ifndef UINT16_MAX
+#define UINT16_MAX             (65535U)
+#endif
+#ifndef UINT32_MAX
+#define UINT32_MAX             (4294967295U)
+#endif
+
+#ifndef SIZE_MAX
+#define SIZE_MAX               (~(size_t)0)
+#endif
+
+#endif /* ! C99 */
+
+#endif /* ! FLEXINT_H */
+
+/* begin standard C++ headers. */
+
+/* TODO: this is always defined, so inline it */
+#define yyconst const
+
+#if defined(__GNUC__) && __GNUC__ >= 3
+#define yynoreturn __attribute__((__noreturn__))
+#else
+#define yynoreturn
+#endif
+
+/* Returned upon end-of-file. */
+#define YY_NULL 0
+
+/* Promotes a possibly negative, possibly signed char to an
+ *   integer in range [0..255] for use as an array index.
+ */
+#define YY_SC_TO_UI(c) ((YY_CHAR) (c))
+
+/* Enter a start condition.  This macro really ought to take a parameter,
+ * but we do it the disgusting crufty way forced on us by the ()-less
+ * definition of BEGIN.
+ */
+#define BEGIN (yy_start) = 1 + 2 *
+/* Translate the current start state into a value that can be later handed
+ * to BEGIN to return to the state.  The YYSTATE alias is for lex
+ * compatibility.
+ */
+#define YY_START (((yy_start) - 1) / 2)
+#define YYSTATE YY_START
+/* Action number for EOF rule of a given start state. */
+#define YY_STATE_EOF(state) (YY_END_OF_BUFFER + state + 1)
+/* Special action meaning "start processing a new file". */
+#define YY_NEW_FILE yyrestart( yyin  )
+#define YY_END_OF_BUFFER_CHAR 0
+
+/* Size of default input buffer. */
+#ifndef YY_BUF_SIZE
+#ifdef __ia64__
+/* On IA-64, the buffer size is 16k, not 8k.
+ * Moreover, YY_BUF_SIZE is 2*YY_READ_BUF_SIZE in the general case.
+ * Ditto for the __ia64__ case accordingly.
+ */
+#define YY_BUF_SIZE 32768
+#else
+#define YY_BUF_SIZE 16384
+#endif /* __ia64__ */
+#endif
+
+/* The state buf must be large enough to hold one state per character in the main buffer.
+ */
+#define YY_STATE_BUF_SIZE   ((YY_BUF_SIZE + 2) * sizeof(yy_state_type))
+
+#ifndef YY_TYPEDEF_YY_BUFFER_STATE
+#define YY_TYPEDEF_YY_BUFFER_STATE
+typedef struct yy_buffer_state *YY_BUFFER_STATE;
+#endif
+
+#ifndef YY_TYPEDEF_YY_SIZE_T
+#define YY_TYPEDEF_YY_SIZE_T
+typedef size_t yy_size_t;
+#endif
+
+extern int yyleng;
+
+extern FILE *yyin, *yyout;
+
+#define EOB_ACT_CONTINUE_SCAN 0
+#define EOB_ACT_END_OF_FILE 1
+#define EOB_ACT_LAST_MATCH 2
+    
+    #define YY_LESS_LINENO(n)
+    #define YY_LINENO_REWIND_TO(ptr)
+    
+/* Return all but the first "n" matched characters back to the input stream. */
+#define yyless(n) \
+	do \
+		{ \
+		/* Undo effects of setting up yytext. */ \
+        int yyless_macro_arg = (n); \
+        YY_LESS_LINENO(yyless_macro_arg);\
+		*yy_cp = (yy_hold_char); \
+		YY_RESTORE_YY_MORE_OFFSET \
+		(yy_c_buf_p) = yy_cp = yy_bp + yyless_macro_arg - YY_MORE_ADJ; \
+		YY_DO_BEFORE_ACTION; /* set up yytext again */ \
+		} \
+	while ( 0 )
+#define unput(c) yyunput( c, (yytext_ptr)  )
+
+#ifndef YY_STRUCT_YY_BUFFER_STATE
+#define YY_STRUCT_YY_BUFFER_STATE
+struct yy_buffer_state
+	{
+	FILE *yy_input_file;
+
+	char *yy_ch_buf;		/* input buffer */
+	char *yy_buf_pos;		/* current position in input buffer */
+
+	/* Size of input buffer in bytes, not including room for EOB
+	 * characters.
+	 */
+	int yy_buf_size;
+
+	/* Number of characters read into yy_ch_buf, not including EOB
+	 * characters.
+	 */
+	int yy_n_chars;
+
+	/* Whether we "own" the buffer - i.e., we know we created it,
+	 * and can realloc() it to grow it, and should free() it to
+	 * delete it.
+	 */
+	int yy_is_our_buffer;
+
+	/* Whether this is an "interactive" input source; if so, and
+	 * if we're using stdio for input, then we want to use getc()
+	 * instead of fread(), to make sure we stop fetching input after
+	 * each newline.
+	 */
+	int yy_is_interactive;
+
+	/* Whether we're considered to be at the beginning of a line.
+	 * If so, '^' rules will be active on the next match, otherwise
+	 * not.
+	 */
+	int yy_at_bol;
+
+    int yy_bs_lineno; /**< The line count. */
+    int yy_bs_column; /**< The column count. */
+
+	/* Whether to try to fill the input buffer when we reach the
+	 * end of it.
+	 */
+	int yy_fill_buffer;
+
+	int yy_buffer_status;
+
+#define YY_BUFFER_NEW 0
+#define YY_BUFFER_NORMAL 1
+	/* When an EOF's been seen but there's still some text to process
+	 * then we mark the buffer as YY_EOF_PENDING, to indicate that we
+	 * shouldn't try reading from the input source any more.  We might
+	 * still have a bunch of tokens to match, though, because of
+	 * possible backing-up.
+	 *
+	 * When we actually see the EOF, we change the status to "new"
+	 * (via yyrestart()), so that the user can continue scanning by
+	 * just pointing yyin at a new input file.
+	 */
+#define YY_BUFFER_EOF_PENDING 2
+
+	};
+#endif /* !YY_STRUCT_YY_BUFFER_STATE */
+
+/* Stack of input buffers. */
+static size_t yy_buffer_stack_top = 0; /**< index of top of stack. */
+static size_t yy_buffer_stack_max = 0; /**< capacity of stack. */
+static YY_BUFFER_STATE * yy_buffer_stack = NULL; /**< Stack as an array. */
+
+/* We provide macros for accessing buffer states in case in the
+ * future we want to put the buffer states in a more general
+ * "scanner state".
+ *
+ * Returns the top of the stack, or NULL.
+ */
+#define YY_CURRENT_BUFFER ( (yy_buffer_stack) \
+                          ? (yy_buffer_stack)[(yy_buffer_stack_top)] \
+                          : NULL)
+/* Same as previous macro, but useful when we know that the buffer stack is not
+ * NULL or when we need an lvalue. For internal use only.
+ */
+#define YY_CURRENT_BUFFER_LVALUE (yy_buffer_stack)[(yy_buffer_stack_top)]
+
+/* yy_hold_char holds the character lost when yytext is formed. */
+static char yy_hold_char;
+static int yy_n_chars;		/* number of characters read into yy_ch_buf */
+int yyleng;
+
+/* Points to current character in buffer. */
+static char *yy_c_buf_p = NULL;
+static int yy_init = 0;		/* whether we need to initialize */
+static int yy_start = 0;	/* start state number */
+
+/* Flag which is used to allow yywrap()'s to do buffer switches
+ * instead of setting up a fresh yyin.  A bit of a hack ...
+ */
+static int yy_did_buffer_switch_on_eof;
+
+void yyrestart ( FILE *input_file  );
+void yy_switch_to_buffer ( YY_BUFFER_STATE new_buffer  );
+YY_BUFFER_STATE yy_create_buffer ( FILE *file, int size  );
+void yy_delete_buffer ( YY_BUFFER_STATE b  );
+void yy_flush_buffer ( YY_BUFFER_STATE b  );
+void yypush_buffer_state ( YY_BUFFER_STATE new_buffer  );
+void yypop_buffer_state ( void );
+
+static void yyensure_buffer_stack ( void );
+static void yy_load_buffer_state ( void );
+static void yy_init_buffer ( YY_BUFFER_STATE b, FILE *file  );
+#define YY_FLUSH_BUFFER yy_flush_buffer( YY_CURRENT_BUFFER )
+
+YY_BUFFER_STATE yy_scan_buffer ( char *base, yy_size_t size  );
+YY_BUFFER_STATE yy_scan_string ( const char *yy_str  );
+YY_BUFFER_STATE yy_scan_bytes ( const char *bytes, int len  );
+
+void *yyalloc ( yy_size_t  );
+void *yyrealloc ( void *, yy_size_t  );
+void yyfree ( void *  );
+
+#define yy_new_buffer yy_create_buffer
+#define yy_set_interactive(is_interactive) \
+	{ \
+	if ( ! YY_CURRENT_BUFFER ){ \
+        yyensure_buffer_stack (); \
+		YY_CURRENT_BUFFER_LVALUE =    \
+            yy_create_buffer( yyin, YY_BUF_SIZE ); \
+	} \
+	YY_CURRENT_BUFFER_LVALUE->yy_is_interactive = is_interactive; \
+	}
+#define yy_set_bol(at_bol) \
+	{ \
+	if ( ! YY_CURRENT_BUFFER ){\
+        yyensure_buffer_stack (); \
+		YY_CURRENT_BUFFER_LVALUE =    \
+            yy_create_buffer( yyin, YY_BUF_SIZE ); \
+	} \
+	YY_CURRENT_BUFFER_LVALUE->yy_at_bol = at_bol; \
+	}
+#define YY_AT_BOL() (YY_CURRENT_BUFFER_LVALUE->yy_at_bol)
+
+/* Begin user sect3 */
+
+#define replication_yywrap() (/*CONSTCOND*/1)
+#define YY_SKIP_YYWRAP
+typedef flex_uint8_t YY_CHAR;
+
+FILE *yyin = NULL, *yyout = NULL;
+
+typedef int yy_state_type;
+
+extern int yylineno;
+int yylineno = 1;
+
+extern char *yytext;
+#ifdef yytext_ptr
+#undef yytext_ptr
+#endif
+#define yytext_ptr yytext
+
+static yy_state_type yy_get_previous_state ( void );
+static yy_state_type yy_try_NUL_trans ( yy_state_type current_state  );
+static int yy_get_next_buffer ( void );
+static void yynoreturn yy_fatal_error ( const char* msg  );
+
+/* Done after the current pattern has been matched and before the
+ * corresponding action - sets up yytext.
+ */
+#define YY_DO_BEFORE_ACTION \
+	(yytext_ptr) = yy_bp; \
+	yyleng = (int) (yy_cp - yy_bp); \
+	(yy_hold_char) = *yy_cp; \
+	*yy_cp = '\0'; \
+	(yy_c_buf_p) = yy_cp;
+#define YY_NUM_RULES 40
+#define YY_END_OF_BUFFER 41
+/* This struct is not used in this scanner,
+   but its presence is necessary. */
+struct yy_trans_info
+	{
+	flex_int32_t yy_verify;
+	flex_int32_t yy_nxt;
+	};
+static const flex_int16_t yy_accept[295] =
+    {   0,
+        0,    0,    0,    0,    0,    0,   41,   39,   28,   28,
+       35,   31,   29,   38,   38,   38,   38,   38,   38,   38,
+       38,   38,   38,   38,   38,   38,   38,   38,   38,   38,
+       37,   36,   34,   32,   28,    0,   29,    0,   38,   38,
+       38,   38,   38,   38,   38,   38,   38,   38,   38,   38,
+       38,   38,   38,   38,   38,   38,   38,   38,   38,   38,
+       38,   37,   34,   33,   30,   38,   38,   38,   38,   38,
+       38,   38,   38,   38,   38,   38,   38,   38,   38,   38,
+       38,   38,   38,   38,   38,   38,   38,   38,   38,    9,
+       38,   38,   38,   38,    2,   38,   38,   38,   38,   38,
+
+       38,   38,   38,   38,   38,   38,    4,   20,   38,   38,
+       38,   38,   38,   25,   38,   38,   38,   38,   38,    5,
+       38,   38,   38,   38,   38,   38,   38,   38,   38,   38,
+       38,   38,   38,   38,   38,   38,   38,   38,   38,   38,
+       38,   38,   38,   38,    6,   38,   38,   38,   38,   38,
+       38,   38,   38,   38,   38,   38,   38,   38,   19,   38,
+       38,   38,   38,   38,   38,   38,   38,   38,   38,   38,
+       38,   38,   38,   38,   38,   38,   26,    8,   38,   38,
+       17,    7,   38,   38,   38,   38,   12,   38,   38,   38,
+       38,   38,   38,   38,   38,   38,   38,   38,   38,   21,
+
+       38,   38,   38,   38,   38,   38,   38,   38,   38,   38,
+       38,   38,   38,   38,   38,    1,   38,   38,   38,   38,
+       38,   38,   38,   18,   38,   38,   38,   38,   38,   38,
+       38,   38,   38,   38,   38,   38,   38,   38,   24,   38,
+       38,   38,   38,   38,   38,   38,   38,   38,   38,   38,
+       38,   38,   38,   38,   38,   38,   38,   10,   38,   38,
+       38,   22,    3,   38,   38,   38,   38,   38,   38,   38,
+       38,   38,   38,   38,   16,   38,   38,   38,   23,   38,
+       13,   38,   38,   27,   11,   38,   38,   38,   38,   38,
+       15,   38,   14,    0
+
+    } ;
+
+static const YY_CHAR yy_ec[256] =
+    {   0,
+        1,    1,    1,    1,    1,    1,    1,    1,    2,    3,
+        1,    2,    2,    1,    1,    1,    1,    1,    1,    1,
+        1,    1,    1,    1,    1,    1,    1,    1,    1,    1,
+        1,    2,    1,    4,    1,    5,    1,    1,    6,    1,
+        1,    1,    1,    1,    1,    1,    7,    8,    8,    8,
+        8,    8,    8,    8,    8,    8,    8,    1,    1,    1,
+        1,    1,    1,    1,    9,   10,   11,   12,   13,   14,
+       15,   16,   17,   18,   19,   20,   21,   22,   23,   24,
+       18,   25,   26,   27,   28,   29,   30,   31,   32,   18,
+        1,    1,    1,    1,   33,    1,   34,   34,   34,   34,
+
+       34,   34,   18,   18,   18,   18,   18,   18,   18,   18,
+       18,   18,   18,   18,   18,   18,   18,   18,   18,   18,
+       18,   18,    1,    1,    1,    1,    1,   18,   18,   18,
+       18,   18,   18,   18,   18,   18,   18,   18,   18,   18,
+       18,   18,   18,   18,   18,   18,   18,   18,   18,   18,
+       18,   18,   18,   18,   18,   18,   18,   18,   18,   18,
+       18,   18,   18,   18,   18,   18,   18,   18,   18,   18,
+       18,   18,   18,   18,   18,   18,   18,   18,   18,   18,
+       18,   18,   18,   18,   18,   18,   18,   18,   18,   18,
+       18,   18,   18,   18,   18,   18,   18,   18,   18,   18,
+
+       18,   18,   18,   18,   18,   18,   18,   18,   18,   18,
+       18,   18,   18,   18,   18,   18,   18,   18,   18,   18,
+       18,   18,   18,   18,   18,   18,   18,   18,   18,   18,
+       18,   18,   18,   18,   18,   18,   18,   18,   18,   18,
+       18,   18,   18,   18,   18,   18,   18,   18,   18,   18,
+       18,   18,   18,   18,   18
+    } ;
+
+static const YY_CHAR yy_meta[35] =
+    {   0,
+        1,    1,    1,    2,    3,    4,    5,    6,    6,    6,
+        6,    6,    6,    6,    3,    3,    3,    3,    3,    3,
+        3,    3,    3,    3,    3,    3,    3,    3,    3,    3,
+        3,    3,    3,    6
+    } ;
+
+static const flex_int16_t yy_base[302] =
+    {   0,
+        0,    0,  606,  605,  602,  601,  606,  611,   33,   35,
+      611,  611,   32,   34,   62,   40,   41,   46,  596,  597,
+       44,   55,   45,   56,   73,   46,   74,   75,   60,   51,
+        0,  611,    0,  597,   97,    0,   95,  595,  594,  591,
+       78,   78,   86,   88,   88,   98,  100,  101,   99,  106,
+      108,  110,  111,  115,  116,  117,  118,  113,  120,  135,
+      136,    0,    0,  611,    0,  137,  122,  125,  138,  139,
+      140,  144,  147,  148,   50,  145,  156,  151,  152,  160,
+      161,  163,  164,  165,  166,  170,  172,  173,  174,  592,
+      175,  176,  177,  180,  591,  182,  191,  181,  188,  189,
+
+      192,  190,  200,  205,  193,  206,  590,  589,  197,  212,
+      213,  214,  216,  588,  219,  220,  221,  223,  228,  587,
+      230,  225,  234,  233,  237,  240,  241,  242,  244,  246,
+      250,  252,  251,  253,  254,  255,  257,  258,  264,  262,
+      259,  265,  273,  267,  586,  277,  276,  280,  282,  287,
+      288,  283,  292,  289,  296,  299,  301,  297,  585,  303,
+      302,  305,  306,  311,  307,  309,  312,  313,  310,  321,
+      317,  329,  330,  319,  333,  337,  338,  584,  339,  340,
+      583,  582,  344,  342,  343,  345,  346,  349,  350,  352,
+      351,  353,  354,  356,  357,  358,  375,  374,  378,  579,
+
+      379,  380,  381,  382,  386,  383,  385,  392,  391,  393,
+      394,  399,  396,  403,  404,  571,  405,  412,  397,  408,
+      411,  419,  418,  567,  425,  423,  426,  428,  430,  431,
+      432,  433,  435,  438,  436,  442,  447,  443,  550,  450,
+      446,  454,  458,  457,  459,  460,  461,  462,  466,  465,
+      467,  468,  473,  471,  475,  474,  476,  549,  477,  489,
+      491,  548,  546,  480,  492,  494,  496,  497,  498,  500,
+      502,  503,  504,  505,  545,  509,  510,  511,  543,  513,
+      542,  507,  521,  541,  540,  517,  519,  525,  527,  528,
+      539,  531,  537,  611,  558,  564,  566,  570,  576,  582,
+
+       55
+    } ;
+
+static const flex_int16_t yy_def[302] =
+    {   0,
+      294,    1,  295,  295,  296,  296,  294,  294,  294,  294,
+      294,  294,  297,  298,  298,   15,   15,   15,   15,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      299,  294,  300,  294,  294,  301,  297,  297,  298,   15,
+       15,  298,  298,  298,   15,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  299,  300,  294,  301,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  298,  298,  298,  298,  298,  298,  298,  298,  298,
+      298,  298,  298,    0,  294,  294,  294,  294,  294,  294,
+
+      294
+    } ;
+
+static const flex_int16_t yy_nxt[646] =
+    {   0,
+        8,    9,   10,   11,    8,   12,    8,   13,   14,   15,
+       16,   17,   18,   19,   20,   20,   21,   20,   20,   22,
+       23,   24,   20,   25,   26,   27,   28,   29,   20,   30,
+       20,   20,   20,   14,   35,   35,   35,   35,   36,   37,
+       36,   40,   40,   40,   40,   40,   40,   40,   40,   40,
+      294,  294,  294,   49,   40,   46,  294,  294,   53,   61,
+       65,  294,  294,   47,   42,   43,  294,   40,   36,   40,
+       41,   40,   40,   40,   40,   40,   44,   48,   50,  294,
+      294,  294,  100,   57,  294,   60,   40,   58,   51,   54,
+       67,   59,  294,   55,  294,   40,   40,   52,   35,   35,
+
+       56,   36,   37,   66,  294,  294,  294,  294,   68,   72,
+       71,   69,  294,   70,  294,   73,  294,  294,   76,  294,
+       74,  294,  294,  294,  294,   84,  294,   85,  294,   75,
+       92,  294,   80,   86,   77,   78,   81,   82,   83,   79,
+       87,  294,  294,  294,  294,  294,  294,   88,   93,   91,
+      294,  294,   89,  294,  294,   90,   97,  294,  294,  103,
+       94,   96,  294,   98,   99,   95,  294,  294,  102,  294,
+      294,  294,  294,  106,  105,  101,  294,  104,  294,  294,
+      294,  294,  294,  294,  112,  110,  294,  294,  294,  109,
+      108,  121,  107,  111,  294,  294,  294,  294,  294,  294,
+
+      114,  122,  116,  294,  118,  113,  294,  115,  119,  117,
+      120,  294,  294,  123,  125,  124,  126,  128,  294,  294,
+      294,  127,  294,  130,  131,  294,  294,  294,  135,  294,
+      129,  294,  136,  133,  294,  132,  294,  141,  140,  294,
+      294,  134,  142,  294,  139,  137,  294,  294,  294,  138,
+      294,  146,  294,  144,  147,  143,  294,  294,  294,  294,
+      294,  294,  154,  294,  294,  294,  145,  152,  294,  156,
+      294,  294,  148,  294,  153,  150,  151,  158,  149,  294,
+      163,  159,  294,  294,  160,  164,  294,  155,  294,  294,
+      157,  161,  166,  294,  294,  294,  169,  162,  294,  172,
+
+      171,  165,  294,  294,  170,  294,  167,  294,  294,  294,
+      168,  294,  294,  294,  178,  294,  294,  294,  294,  294,
+      173,  185,  174,  294,  184,  294,  175,  294,  176,  177,
+      181,  179,  182,  187,  186,  294,  294,  180,  191,  294,
+      188,  183,  190,  294,  294,  294,  294,  189,  294,  294,
+      294,  294,  294,  199,  192,  294,  294,  294,  294,  294,
+      294,  206,  294,  294,  294,  198,  208,  205,  210,  193,
+      194,  195,  196,  197,  202,  204,  200,  203,  201,  207,
+      294,  294,  209,  211,  294,  294,  294,  294,  294,  294,
+      213,  294,  294,  212,  214,  215,  218,  294,  294,  294,
+
+      294,  217,  294,  294,  216,  294,  219,  221,  223,  294,
+      294,  294,  222,  224,  294,  225,  220,  294,  294,  227,
+      230,  229,  231,  233,  294,  294,  228,  234,  226,  294,
+      235,  294,  294,  232,  294,  236,  294,  294,  294,  294,
+      240,  294,  294,  237,  294,  244,  246,  242,  294,  294,
+      247,  238,  294,  294,  239,  248,  294,  241,  250,  243,
+      294,  245,  251,  294,  294,  294,  294,  294,  294,  249,
+      253,  294,  294,  294,  294,  254,  252,  294,  256,  294,
+      294,  294,  294,  294,  255,  258,  294,  257,  259,  261,
+      265,  260,  267,  263,  262,  294,  264,  294,  294,  266,
+
+      294,  268,  294,  294,  294,  269,  294,  271,  294,  294,
+      294,  294,  270,  294,  272,  294,  294,  294,  274,  294,
+      276,  273,  278,  294,  280,  294,  281,  294,  275,  279,
+      282,  294,  277,  294,  294,  283,  284,  294,  285,  286,
+      287,  289,  288,  294,  290,  294,  294,  294,  294,  294,
+      292,  294,  294,  291,  294,  294,  294,  293,   31,   31,
+       31,   31,   31,   31,   33,   33,   33,   33,   33,   33,
+       38,   38,   39,  294,   39,   39,   62,  294,   62,   62,
+       62,   62,   63,   63,   63,  294,   63,   63,  294,  294,
+      294,  294,  294,  294,  294,  294,  294,  294,  294,   40,
+
+      294,   36,   64,  294,   45,  294,   34,   34,   32,   32,
+        7,  294,  294,  294,  294,  294,  294,  294,  294,  294,
+      294,  294,  294,  294,  294,  294,  294,  294,  294,  294,
+      294,  294,  294,  294,  294,  294,  294,  294,  294,  294,
+      294,  294,  294,  294,  294
+    } ;
+
+static const flex_int16_t yy_chk[646] =
+    {   0,
+        1,    1,    1,    1,    1,    1,    1,    1,    1,    1,
+        1,    1,    1,    1,    1,    1,    1,    1,    1,    1,
+        1,    1,    1,    1,    1,    1,    1,    1,    1,    1,
+        1,    1,    1,    1,    9,    9,   10,   10,   13,   13,
+       14,   14,   14,   14,   14,   14,   14,   14,   16,   17,
+       21,   23,   26,   23,   18,   21,   75,   30,   26,   30,
+      301,   22,   24,   22,   16,   17,   29,   14,   15,   15,
+       15,   15,   15,   15,   15,   15,   18,   22,   24,   25,
+       27,   28,   75,   28,   42,   29,   41,   28,   25,   27,
+       42,   28,   43,   27,   44,   15,   45,   25,   35,   35,
+
+       27,   37,   37,   41,   46,   49,   47,   48,   43,   47,
+       46,   44,   50,   45,   51,   48,   52,   53,   50,   58,
+       49,   54,   55,   56,   57,   56,   59,   57,   67,   49,
+       67,   68,   52,   58,   50,   50,   53,   54,   55,   51,
+       59,   60,   61,   66,   69,   70,   71,   60,   68,   66,
+       72,   76,   61,   73,   74,   61,   72,   78,   79,   78,
+       69,   71,   77,   73,   74,   70,   80,   81,   77,   82,
+       83,   84,   85,   81,   80,   76,   86,   79,   87,   88,
+       89,   91,   92,   93,   87,   85,   94,   98,   96,   84,
+       83,   98,   82,   86,   99,  100,  102,   97,  101,  105,
+
+       89,   99,   92,  109,   94,   88,  103,   91,   96,   93,
+       97,  104,  106,  100,  102,  101,  103,  105,  110,  111,
+      112,  104,  113,  109,  110,  115,  116,  117,  115,  118,
+      106,  122,  116,  112,  119,  111,  121,  122,  121,  124,
+      123,  113,  123,  125,  119,  117,  126,  127,  128,  118,
+      129,  127,  130,  125,  128,  124,  131,  133,  132,  134,
+      135,  136,  135,  137,  138,  141,  126,  133,  140,  137,
+      139,  142,  129,  144,  134,  131,  132,  139,  130,  143,
+      144,  140,  147,  146,  141,  146,  148,  136,  149,  152,
+      138,  142,  148,  150,  151,  154,  151,  143,  153,  154,
+
+      153,  147,  155,  158,  152,  156,  149,  157,  161,  160,
+      150,  162,  163,  165,  161,  166,  169,  164,  167,  168,
+      155,  168,  156,  171,  167,  174,  157,  170,  158,  160,
+      164,  162,  165,  170,  169,  172,  173,  163,  174,  175,
+      171,  166,  173,  176,  177,  179,  180,  172,  184,  185,
+      183,  186,  187,  185,  175,  188,  189,  191,  190,  192,
+      193,  192,  194,  195,  196,  184,  194,  191,  196,  176,
+      177,  179,  180,  183,  188,  190,  186,  189,  187,  193,
+      198,  197,  195,  197,  199,  201,  202,  203,  204,  206,
+      199,  207,  205,  198,  201,  202,  205,  209,  208,  210,
+
+      211,  204,  213,  219,  203,  212,  206,  208,  210,  214,
+      215,  217,  209,  211,  220,  212,  207,  221,  218,  214,
+      218,  217,  219,  221,  223,  222,  215,  222,  213,  226,
+      223,  225,  227,  220,  228,  225,  229,  230,  231,  232,
+      229,  233,  235,  226,  234,  233,  235,  231,  236,  238,
+      236,  227,  241,  237,  228,  237,  240,  230,  240,  232,
+      242,  234,  241,  244,  243,  245,  246,  247,  248,  238,
+      243,  250,  249,  251,  252,  244,  242,  254,  246,  253,
+      256,  255,  257,  259,  245,  248,  264,  247,  249,  251,
+      255,  250,  257,  253,  252,  260,  254,  261,  265,  256,
+
+      266,  259,  267,  268,  269,  260,  270,  264,  271,  272,
+      273,  274,  261,  282,  265,  276,  277,  278,  267,  280,
+      269,  266,  271,  286,  273,  287,  274,  283,  268,  272,
+      276,  288,  270,  289,  290,  277,  278,  292,  280,  282,
+      283,  287,  286,  293,  288,  291,  285,  284,  281,  279,
+      290,  275,  263,  289,  262,  258,  239,  292,  295,  295,
+      295,  295,  295,  295,  296,  296,  296,  296,  296,  296,
+      297,  297,  298,  224,  298,  298,  299,  216,  299,  299,
+      299,  299,  300,  300,  300,  200,  300,  300,  182,  181,
+      178,  159,  145,  120,  114,  108,  107,   95,   90,   40,
+
+       39,   38,   34,   20,   19,    7,    6,    5,    4,    3,
+      294,  294,  294,  294,  294,  294,  294,  294,  294,  294,
+      294,  294,  294,  294,  294,  294,  294,  294,  294,  294,
+      294,  294,  294,  294,  294,  294,  294,  294,  294,  294,
+      294,  294,  294,  294,  294
+    } ;
+
+static yy_state_type yy_last_accepting_state;
+static char *yy_last_accepting_cpos;
+
+extern int yy_flex_debug;
+int yy_flex_debug = 0;
+
+/* The intent behind this definition is that it'll catch
+ * any uses of REJECT which flex missed.
+ */
+#define REJECT reject_used_but_not_detected
+#define yymore() yymore_used_but_not_detected
+#define YY_MORE_ADJ 0
+#define YY_RESTORE_YY_MORE_OFFSET
+char *yytext;
+#line 1 "repl_scanner.l"
+#line 2 "repl_scanner.l"
+/*-------------------------------------------------------------------------
+ *
+ * repl_scanner.l
+ *	  a lexical scanner for the replication commands
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/repl_scanner.l
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "utils/builtins.h"
+#include "parser/scansup.h"
+
+/* Avoid exit() on fatal scanner errors (a bit ugly -- see yy_fatal_error) */
+#undef fprintf
+#define fprintf(file, fmt, msg)  fprintf_to_ereport(fmt, msg)
+
+static void
+fprintf_to_ereport(const char *fmt, const char *msg)
+{
+	ereport(ERROR, (errmsg_internal("%s", msg)));
+}
+
+/* Handle to the buffer that the lexer uses internally */
+static YY_BUFFER_STATE scanbufhandle;
+
+/* Pushed-back token (we only handle one) */
+static int	repl_pushed_back_token;
+
+/* Work area for collecting literals */
+static StringInfoData litbuf;
+
+static void startlit(void);
+static char *litbufdup(void);
+static void addlit(char *ytext, int yleng);
+static void addlitchar(unsigned char ychar);
+
+/* LCOV_EXCL_START */
+
+#line 991 "repl_scanner.c"
+#define YY_NO_INPUT 1
+/*
+ * Exclusive states:
+ *  <xd> delimited identifiers (double-quoted identifiers)
+ *  <xq> standard single-quoted strings
+ */
+
+/* Extended quote
+ * xqdouble implements embedded quote, ''''
+ */
+/* Double quote
+ * Allows embedded spaces and other special characters into identifiers.
+ */
+#line 1005 "repl_scanner.c"
+
+#define INITIAL 0
+#define xd 1
+#define xq 2
+
+#ifndef YY_NO_UNISTD_H
+/* Special case for "unistd.h", since it is non-ANSI. We include it way
+ * down here because we want the user's section 1 to have been scanned first.
+ * The user has a chance to override it with an option.
+ */
+#include <unistd.h>
+#endif
+
+#ifndef YY_EXTRA_TYPE
+#define YY_EXTRA_TYPE void *
+#endif
+
+static int yy_init_globals ( void );
+
+/* Accessor methods to globals.
+   These are made visible to non-reentrant scanners for convenience. */
+
+int yylex_destroy ( void );
+
+int yyget_debug ( void );
+
+void yyset_debug ( int debug_flag  );
+
+YY_EXTRA_TYPE yyget_extra ( void );
+
+void yyset_extra ( YY_EXTRA_TYPE user_defined  );
+
+FILE *yyget_in ( void );
+
+void yyset_in  ( FILE * _in_str  );
+
+FILE *yyget_out ( void );
+
+void yyset_out  ( FILE * _out_str  );
+
+			int yyget_leng ( void );
+
+char *yyget_text ( void );
+
+int yyget_lineno ( void );
+
+void yyset_lineno ( int _line_number  );
+
+/* Macros after this point can all be overridden by user definitions in
+ * section 1.
+ */
+
+#ifndef YY_SKIP_YYWRAP
+#ifdef __cplusplus
+extern "C" int yywrap ( void );
+#else
+extern int yywrap ( void );
+#endif
+#endif
+
+#ifndef YY_NO_UNPUT
+    
+#endif
+
+#ifndef yytext_ptr
+static void yy_flex_strncpy ( char *, const char *, int );
+#endif
+
+#ifdef YY_NEED_STRLEN
+static int yy_flex_strlen ( const char * );
+#endif
+
+#ifndef YY_NO_INPUT
+#ifdef __cplusplus
+static int yyinput ( void );
+#else
+static int input ( void );
+#endif
+
+#endif
+
+/* Amount of stuff to slurp up with each read. */
+#ifndef YY_READ_BUF_SIZE
+#ifdef __ia64__
+/* On IA-64, the buffer size is 16k, not 8k */
+#define YY_READ_BUF_SIZE 16384
+#else
+#define YY_READ_BUF_SIZE 8192
+#endif /* __ia64__ */
+#endif
+
+/* Copy whatever the last rule matched to the standard output. */
+#ifndef ECHO
+/* This used to be an fputs(), but since the string might contain NUL's,
+ * we now use fwrite().
+ */
+#define ECHO do { if (fwrite( yytext, (size_t) yyleng, 1, yyout )) {} } while (0)
+#endif
+
+/* Gets input and stuffs it into "buf".  number of characters read, or YY_NULL,
+ * is returned in "result".
+ */
+#ifndef YY_INPUT
+#define YY_INPUT(buf,result,max_size) \
+	if ( YY_CURRENT_BUFFER_LVALUE->yy_is_interactive ) \
+		{ \
+		int c = '*'; \
+		int n; \
+		for ( n = 0; n < max_size && \
+			     (c = getc( yyin )) != EOF && c != '\n'; ++n ) \
+			buf[n] = (char) c; \
+		if ( c == '\n' ) \
+			buf[n++] = (char) c; \
+		if ( c == EOF && ferror( yyin ) ) \
+			YY_FATAL_ERROR( "input in flex scanner failed" ); \
+		result = n; \
+		} \
+	else \
+		{ \
+		errno=0; \
+		while ( (result = (int) fread(buf, 1, (yy_size_t) max_size, yyin)) == 0 && ferror(yyin)) \
+			{ \
+			if( errno != EINTR) \
+				{ \
+				YY_FATAL_ERROR( "input in flex scanner failed" ); \
+				break; \
+				} \
+			errno=0; \
+			clearerr(yyin); \
+			} \
+		}\
+\
+
+#endif
+
+/* No semi-colon after return; correct usage is to write "yyterminate();" -
+ * we don't want an extra ';' after the "return" because that will cause
+ * some compilers to complain about unreachable statements.
+ */
+#ifndef yyterminate
+#define yyterminate() return YY_NULL
+#endif
+
+/* Number of entries by which start-condition stack grows. */
+#ifndef YY_START_STACK_INCR
+#define YY_START_STACK_INCR 25
+#endif
+
+/* Report a fatal error. */
+#ifndef YY_FATAL_ERROR
+#define YY_FATAL_ERROR(msg) yy_fatal_error( msg )
+#endif
+
+/* end tables serialization structures and prototypes */
+
+/* Default declaration of generated scanner - a define so the user can
+ * easily add parameters.
+ */
+#ifndef YY_DECL
+#define YY_DECL_IS_OURS 1
+
+extern int yylex (void);
+
+#define YY_DECL int yylex (void)
+#endif /* !YY_DECL */
+
+/* Code executed at the beginning of each rule, after yytext and yyleng
+ * have been set up.
+ */
+#ifndef YY_USER_ACTION
+#define YY_USER_ACTION
+#endif
+
+/* Code executed at the end of each rule. */
+#ifndef YY_BREAK
+#define YY_BREAK /*LINTED*/break;
+#endif
+
+#define YY_RULE_SETUP \
+	YY_USER_ACTION
+
+/** The main scanner function which does all the work.
+ */
+YY_DECL
+{
+	yy_state_type yy_current_state;
+	char *yy_cp, *yy_bp;
+	int yy_act;
+    
+	if ( !(yy_init) )
+		{
+		(yy_init) = 1;
+
+#ifdef YY_USER_INIT
+		YY_USER_INIT;
+#endif
+
+		if ( ! (yy_start) )
+			(yy_start) = 1;	/* first start state */
+
+		if ( ! yyin )
+			yyin = stdin;
+
+		if ( ! yyout )
+			yyout = stdout;
+
+		if ( ! YY_CURRENT_BUFFER ) {
+			yyensure_buffer_stack ();
+			YY_CURRENT_BUFFER_LVALUE =
+				yy_create_buffer( yyin, YY_BUF_SIZE );
+		}
+
+		yy_load_buffer_state(  );
+		}
+
+	{
+#line 95 "repl_scanner.l"
+
+
+
+#line 99 "repl_scanner.l"
+	/* This code is inserted at the start of replication_yylex() */
+
+	/* If we have a pushed-back token, return that. */
+	if (repl_pushed_back_token)
+	{
+		int			result = repl_pushed_back_token;
+
+		repl_pushed_back_token = 0;
+		return result;
+	}
+
+
+#line 1239 "repl_scanner.c"
+
+	while ( /*CONSTCOND*/1 )		/* loops until end-of-file is reached */
+		{
+		yy_cp = (yy_c_buf_p);
+
+		/* Support of yytext. */
+		*yy_cp = (yy_hold_char);
+
+		/* yy_bp points to the position in yy_ch_buf of the start of
+		 * the current run.
+		 */
+		yy_bp = yy_cp;
+
+		yy_current_state = (yy_start);
+yy_match:
+		do
+			{
+			YY_CHAR yy_c = yy_ec[YY_SC_TO_UI(*yy_cp)] ;
+			if ( yy_accept[yy_current_state] )
+				{
+				(yy_last_accepting_state) = yy_current_state;
+				(yy_last_accepting_cpos) = yy_cp;
+				}
+			while ( yy_chk[yy_base[yy_current_state] + yy_c] != yy_current_state )
+				{
+				yy_current_state = (int) yy_def[yy_current_state];
+				if ( yy_current_state >= 295 )
+					yy_c = yy_meta[yy_c];
+				}
+			yy_current_state = yy_nxt[yy_base[yy_current_state] + yy_c];
+			++yy_cp;
+			}
+		while ( yy_current_state != 294 );
+		yy_cp = (yy_last_accepting_cpos);
+		yy_current_state = (yy_last_accepting_state);
+
+yy_find_action:
+		yy_act = yy_accept[yy_current_state];
+
+		YY_DO_BEFORE_ACTION;
+
+do_action:	/* This label is used only to access EOF actions. */
+
+		switch ( yy_act )
+	{ /* beginning of action switch */
+			case 0: /* must back up */
+			/* undo the effects of YY_DO_BEFORE_ACTION */
+			*yy_cp = (yy_hold_char);
+			yy_cp = (yy_last_accepting_cpos);
+			yy_current_state = (yy_last_accepting_state);
+			goto yy_find_action;
+
+case 1:
+YY_RULE_SETUP
+#line 111 "repl_scanner.l"
+{ return K_BASE_BACKUP; }
+	YY_BREAK
+case 2:
+YY_RULE_SETUP
+#line 112 "repl_scanner.l"
+{ return K_FAST; }
+	YY_BREAK
+case 3:
+YY_RULE_SETUP
+#line 113 "repl_scanner.l"
+{ return K_IDENTIFY_SYSTEM; }
+	YY_BREAK
+case 4:
+YY_RULE_SETUP
+#line 114 "repl_scanner.l"
+{ return K_SHOW; }
+	YY_BREAK
+case 5:
+YY_RULE_SETUP
+#line 115 "repl_scanner.l"
+{ return K_LABEL; }
+	YY_BREAK
+case 6:
+YY_RULE_SETUP
+#line 116 "repl_scanner.l"
+{ return K_NOWAIT; }
+	YY_BREAK
+case 7:
+YY_RULE_SETUP
+#line 117 "repl_scanner.l"
+{ return K_PROGRESS; }
+	YY_BREAK
+case 8:
+YY_RULE_SETUP
+#line 118 "repl_scanner.l"
+{ return K_MAX_RATE; }
+	YY_BREAK
+case 9:
+YY_RULE_SETUP
+#line 119 "repl_scanner.l"
+{ return K_WAL; }
+	YY_BREAK
+case 10:
+YY_RULE_SETUP
+#line 120 "repl_scanner.l"
+{ return K_TABLESPACE_MAP; }
+	YY_BREAK
+case 11:
+YY_RULE_SETUP
+#line 121 "repl_scanner.l"
+{ return K_NOVERIFY_CHECKSUMS; }
+	YY_BREAK
+case 12:
+YY_RULE_SETUP
+#line 122 "repl_scanner.l"
+{ return K_TIMELINE; }
+	YY_BREAK
+case 13:
+YY_RULE_SETUP
+#line 123 "repl_scanner.l"
+{ return K_START_REPLICATION; }
+	YY_BREAK
+case 14:
+YY_RULE_SETUP
+#line 124 "repl_scanner.l"
+{ return K_CREATE_REPLICATION_SLOT; }
+	YY_BREAK
+case 15:
+YY_RULE_SETUP
+#line 125 "repl_scanner.l"
+{ return K_DROP_REPLICATION_SLOT; }
+	YY_BREAK
+case 16:
+YY_RULE_SETUP
+#line 126 "repl_scanner.l"
+{ return K_TIMELINE_HISTORY; }
+	YY_BREAK
+case 17:
+YY_RULE_SETUP
+#line 127 "repl_scanner.l"
+{ return K_PHYSICAL; }
+	YY_BREAK
+case 18:
+YY_RULE_SETUP
+#line 128 "repl_scanner.l"
+{ return K_RESERVE_WAL; }
+	YY_BREAK
+case 19:
+YY_RULE_SETUP
+#line 129 "repl_scanner.l"
+{ return K_LOGICAL; }
+	YY_BREAK
+case 20:
+YY_RULE_SETUP
+#line 130 "repl_scanner.l"
+{ return K_SLOT; }
+	YY_BREAK
+case 21:
+YY_RULE_SETUP
+#line 131 "repl_scanner.l"
+{ return K_TEMPORARY; }
+	YY_BREAK
+case 22:
+YY_RULE_SETUP
+#line 132 "repl_scanner.l"
+{ return K_EXPORT_SNAPSHOT; }
+	YY_BREAK
+case 23:
+YY_RULE_SETUP
+#line 133 "repl_scanner.l"
+{ return K_NOEXPORT_SNAPSHOT; }
+	YY_BREAK
+case 24:
+YY_RULE_SETUP
+#line 134 "repl_scanner.l"
+{ return K_USE_SNAPSHOT; }
+	YY_BREAK
+case 25:
+YY_RULE_SETUP
+#line 135 "repl_scanner.l"
+{ return K_WAIT; }
+	YY_BREAK
+case 26:
+YY_RULE_SETUP
+#line 136 "repl_scanner.l"
+{ return K_MANIFEST; }
+	YY_BREAK
+case 27:
+YY_RULE_SETUP
+#line 137 "repl_scanner.l"
+{ return K_MANIFEST_CHECKSUMS; }
+	YY_BREAK
+case 28:
+/* rule 28 can match eol */
+YY_RULE_SETUP
+#line 139 "repl_scanner.l"
+{ /* do nothing */ }
+	YY_BREAK
+case 29:
+YY_RULE_SETUP
+#line 141 "repl_scanner.l"
+{
+					yylval.uintval = strtoul(yytext, NULL, 10);
+					return UCONST;
+				}
+	YY_BREAK
+case 30:
+YY_RULE_SETUP
+#line 146 "repl_scanner.l"
+{
+					uint32	hi,
+							lo;
+					if (sscanf(yytext, "%X/%X", &hi, &lo) != 2)
+						yyerror("invalid streaming start location");
+					yylval.recptr = ((uint64) hi) << 32 | lo;
+					return RECPTR;
+				}
+	YY_BREAK
+case 31:
+YY_RULE_SETUP
+#line 155 "repl_scanner.l"
+{
+					BEGIN(xq);
+					startlit();
+				}
+	YY_BREAK
+case 32:
+YY_RULE_SETUP
+#line 160 "repl_scanner.l"
+{
+					yyless(1);
+					BEGIN(INITIAL);
+					yylval.str = litbufdup();
+					return SCONST;
+				}
+	YY_BREAK
+case 33:
+YY_RULE_SETUP
+#line 167 "repl_scanner.l"
+{
+					addlitchar('\'');
+				}
+	YY_BREAK
+case 34:
+/* rule 34 can match eol */
+YY_RULE_SETUP
+#line 171 "repl_scanner.l"
+{
+					addlit(yytext, yyleng);
+				}
+	YY_BREAK
+case 35:
+YY_RULE_SETUP
+#line 175 "repl_scanner.l"
+{
+					BEGIN(xd);
+					startlit();
+				}
+	YY_BREAK
+case 36:
+YY_RULE_SETUP
+#line 180 "repl_scanner.l"
+{
+					int len;
+					yyless(1);
+					BEGIN(INITIAL);
+					yylval.str = litbufdup();
+					len = strlen(yylval.str);
+					truncate_identifier(yylval.str, len, true);
+					return IDENT;
+				}
+	YY_BREAK
+case 37:
+/* rule 37 can match eol */
+YY_RULE_SETUP
+#line 190 "repl_scanner.l"
+{
+					addlit(yytext, yyleng);
+				}
+	YY_BREAK
+case 38:
+YY_RULE_SETUP
+#line 194 "repl_scanner.l"
+{
+					int len = strlen(yytext);
+
+					yylval.str = downcase_truncate_identifier(yytext, len, true);
+					return IDENT;
+				}
+	YY_BREAK
+case 39:
+YY_RULE_SETUP
+#line 201 "repl_scanner.l"
+{
+					/* Any char not recognized above is returned as itself */
+					return yytext[0];
+				}
+	YY_BREAK
+case YY_STATE_EOF(xq):
+case YY_STATE_EOF(xd):
+#line 206 "repl_scanner.l"
+{ yyerror("unterminated quoted string"); }
+	YY_BREAK
+case YY_STATE_EOF(INITIAL):
+#line 209 "repl_scanner.l"
+{
+					yyterminate();
+				}
+	YY_BREAK
+case 40:
+YY_RULE_SETUP
+#line 213 "repl_scanner.l"
+YY_FATAL_ERROR( "flex scanner jammed" );
+	YY_BREAK
+#line 1549 "repl_scanner.c"
+
+	case YY_END_OF_BUFFER:
+		{
+		/* Amount of text matched not including the EOB char. */
+		int yy_amount_of_matched_text = (int) (yy_cp - (yytext_ptr)) - 1;
+
+		/* Undo the effects of YY_DO_BEFORE_ACTION. */
+		*yy_cp = (yy_hold_char);
+		YY_RESTORE_YY_MORE_OFFSET
+
+		if ( YY_CURRENT_BUFFER_LVALUE->yy_buffer_status == YY_BUFFER_NEW )
+			{
+			/* We're scanning a new file or input source.  It's
+			 * possible that this happened because the user
+			 * just pointed yyin at a new source and called
+			 * yylex().  If so, then we have to assure
+			 * consistency between YY_CURRENT_BUFFER and our
+			 * globals.  Here is the right place to do so, because
+			 * this is the first action (other than possibly a
+			 * back-up) that will match for the new input source.
+			 */
+			(yy_n_chars) = YY_CURRENT_BUFFER_LVALUE->yy_n_chars;
+			YY_CURRENT_BUFFER_LVALUE->yy_input_file = yyin;
+			YY_CURRENT_BUFFER_LVALUE->yy_buffer_status = YY_BUFFER_NORMAL;
+			}
+
+		/* Note that here we test for yy_c_buf_p "<=" to the position
+		 * of the first EOB in the buffer, since yy_c_buf_p will
+		 * already have been incremented past the NUL character
+		 * (since all states make transitions on EOB to the
+		 * end-of-buffer state).  Contrast this with the test
+		 * in input().
+		 */
+		if ( (yy_c_buf_p) <= &YY_CURRENT_BUFFER_LVALUE->yy_ch_buf[(yy_n_chars)] )
+			{ /* This was really a NUL. */
+			yy_state_type yy_next_state;
+
+			(yy_c_buf_p) = (yytext_ptr) + yy_amount_of_matched_text;
+
+			yy_current_state = yy_get_previous_state(  );
+
+			/* Okay, we're now positioned to make the NUL
+			 * transition.  We couldn't have
+			 * yy_get_previous_state() go ahead and do it
+			 * for us because it doesn't know how to deal
+			 * with the possibility of jamming (and we don't
+			 * want to build jamming into it because then it
+			 * will run more slowly).
+			 */
+
+			yy_next_state = yy_try_NUL_trans( yy_current_state );
+
+			yy_bp = (yytext_ptr) + YY_MORE_ADJ;
+
+			if ( yy_next_state )
+				{
+				/* Consume the NUL. */
+				yy_cp = ++(yy_c_buf_p);
+				yy_current_state = yy_next_state;
+				goto yy_match;
+				}
+
+			else
+				{
+				yy_cp = (yy_last_accepting_cpos);
+				yy_current_state = (yy_last_accepting_state);
+				goto yy_find_action;
+				}
+			}
+
+		else switch ( yy_get_next_buffer(  ) )
+			{
+			case EOB_ACT_END_OF_FILE:
+				{
+				(yy_did_buffer_switch_on_eof) = 0;
+
+				if ( yywrap(  ) )
+					{
+					/* Note: because we've taken care in
+					 * yy_get_next_buffer() to have set up
+					 * yytext, we can now set up
+					 * yy_c_buf_p so that if some total
+					 * hoser (like flex itself) wants to
+					 * call the scanner after we return the
+					 * YY_NULL, it'll still work - another
+					 * YY_NULL will get returned.
+					 */
+					(yy_c_buf_p) = (yytext_ptr) + YY_MORE_ADJ;
+
+					yy_act = YY_STATE_EOF(YY_START);
+					goto do_action;
+					}
+
+				else
+					{
+					if ( ! (yy_did_buffer_switch_on_eof) )
+						YY_NEW_FILE;
+					}
+				break;
+				}
+
+			case EOB_ACT_CONTINUE_SCAN:
+				(yy_c_buf_p) =
+					(yytext_ptr) + yy_amount_of_matched_text;
+
+				yy_current_state = yy_get_previous_state(  );
+
+				yy_cp = (yy_c_buf_p);
+				yy_bp = (yytext_ptr) + YY_MORE_ADJ;
+				goto yy_match;
+
+			case EOB_ACT_LAST_MATCH:
+				(yy_c_buf_p) =
+				&YY_CURRENT_BUFFER_LVALUE->yy_ch_buf[(yy_n_chars)];
+
+				yy_current_state = yy_get_previous_state(  );
+
+				yy_cp = (yy_c_buf_p);
+				yy_bp = (yytext_ptr) + YY_MORE_ADJ;
+				goto yy_find_action;
+			}
+		break;
+		}
+
+	default:
+		YY_FATAL_ERROR(
+			"fatal flex scanner internal error--no action found" );
+	} /* end of action switch */
+		} /* end of scanning one token */
+	} /* end of user's declarations */
+} /* end of yylex */
+
+/* yy_get_next_buffer - try to read in a new buffer
+ *
+ * Returns a code representing an action:
+ *	EOB_ACT_LAST_MATCH -
+ *	EOB_ACT_CONTINUE_SCAN - continue scanning from current position
+ *	EOB_ACT_END_OF_FILE - end of file
+ */
+static int yy_get_next_buffer (void)
+{
+    	char *dest = YY_CURRENT_BUFFER_LVALUE->yy_ch_buf;
+	char *source = (yytext_ptr);
+	int number_to_move, i;
+	int ret_val;
+
+	if ( (yy_c_buf_p) > &YY_CURRENT_BUFFER_LVALUE->yy_ch_buf[(yy_n_chars) + 1] )
+		YY_FATAL_ERROR(
+		"fatal flex scanner internal error--end of buffer missed" );
+
+	if ( YY_CURRENT_BUFFER_LVALUE->yy_fill_buffer == 0 )
+		{ /* Don't try to fill the buffer, so this is an EOF. */
+		if ( (yy_c_buf_p) - (yytext_ptr) - YY_MORE_ADJ == 1 )
+			{
+			/* We matched a single character, the EOB, so
+			 * treat this as a final EOF.
+			 */
+			return EOB_ACT_END_OF_FILE;
+			}
+
+		else
+			{
+			/* We matched some text prior to the EOB, first
+			 * process it.
+			 */
+			return EOB_ACT_LAST_MATCH;
+			}
+		}
+
+	/* Try to read more data. */
+
+	/* First move last chars to start of buffer. */
+	number_to_move = (int) ((yy_c_buf_p) - (yytext_ptr) - 1);
+
+	for ( i = 0; i < number_to_move; ++i )
+		*(dest++) = *(source++);
+
+	if ( YY_CURRENT_BUFFER_LVALUE->yy_buffer_status == YY_BUFFER_EOF_PENDING )
+		/* don't do the read, it's not guaranteed to return an EOF,
+		 * just force an EOF
+		 */
+		YY_CURRENT_BUFFER_LVALUE->yy_n_chars = (yy_n_chars) = 0;
+
+	else
+		{
+			int num_to_read =
+			YY_CURRENT_BUFFER_LVALUE->yy_buf_size - number_to_move - 1;
+
+		while ( num_to_read <= 0 )
+			{ /* Not enough room in the buffer - grow it. */
+
+			/* just a shorter name for the current buffer */
+			YY_BUFFER_STATE b = YY_CURRENT_BUFFER_LVALUE;
+
+			int yy_c_buf_p_offset =
+				(int) ((yy_c_buf_p) - b->yy_ch_buf);
+
+			if ( b->yy_is_our_buffer )
+				{
+				int new_size = b->yy_buf_size * 2;
+
+				if ( new_size <= 0 )
+					b->yy_buf_size += b->yy_buf_size / 8;
+				else
+					b->yy_buf_size *= 2;
+
+				b->yy_ch_buf = (char *)
+					/* Include room in for 2 EOB chars. */
+					yyrealloc( (void *) b->yy_ch_buf,
+							 (yy_size_t) (b->yy_buf_size + 2)  );
+				}
+			else
+				/* Can't grow it, we don't own it. */
+				b->yy_ch_buf = NULL;
+
+			if ( ! b->yy_ch_buf )
+				YY_FATAL_ERROR(
+				"fatal error - scanner input buffer overflow" );
+
+			(yy_c_buf_p) = &b->yy_ch_buf[yy_c_buf_p_offset];
+
+			num_to_read = YY_CURRENT_BUFFER_LVALUE->yy_buf_size -
+						number_to_move - 1;
+
+			}
+
+		if ( num_to_read > YY_READ_BUF_SIZE )
+			num_to_read = YY_READ_BUF_SIZE;
+
+		/* Read in more data. */
+		YY_INPUT( (&YY_CURRENT_BUFFER_LVALUE->yy_ch_buf[number_to_move]),
+			(yy_n_chars), num_to_read );
+
+		YY_CURRENT_BUFFER_LVALUE->yy_n_chars = (yy_n_chars);
+		}
+
+	if ( (yy_n_chars) == 0 )
+		{
+		if ( number_to_move == YY_MORE_ADJ )
+			{
+			ret_val = EOB_ACT_END_OF_FILE;
+			yyrestart( yyin  );
+			}
+
+		else
+			{
+			ret_val = EOB_ACT_LAST_MATCH;
+			YY_CURRENT_BUFFER_LVALUE->yy_buffer_status =
+				YY_BUFFER_EOF_PENDING;
+			}
+		}
+
+	else
+		ret_val = EOB_ACT_CONTINUE_SCAN;
+
+	if (((yy_n_chars) + number_to_move) > YY_CURRENT_BUFFER_LVALUE->yy_buf_size) {
+		/* Extend the array by 50%, plus the number we really need. */
+		int new_size = (yy_n_chars) + number_to_move + ((yy_n_chars) >> 1);
+		YY_CURRENT_BUFFER_LVALUE->yy_ch_buf = (char *) yyrealloc(
+			(void *) YY_CURRENT_BUFFER_LVALUE->yy_ch_buf, (yy_size_t) new_size  );
+		if ( ! YY_CURRENT_BUFFER_LVALUE->yy_ch_buf )
+			YY_FATAL_ERROR( "out of dynamic memory in yy_get_next_buffer()" );
+		/* "- 2" to take care of EOB's */
+		YY_CURRENT_BUFFER_LVALUE->yy_buf_size = (int) (new_size - 2);
+	}
+
+	(yy_n_chars) += number_to_move;
+	YY_CURRENT_BUFFER_LVALUE->yy_ch_buf[(yy_n_chars)] = YY_END_OF_BUFFER_CHAR;
+	YY_CURRENT_BUFFER_LVALUE->yy_ch_buf[(yy_n_chars) + 1] = YY_END_OF_BUFFER_CHAR;
+
+	(yytext_ptr) = &YY_CURRENT_BUFFER_LVALUE->yy_ch_buf[0];
+
+	return ret_val;
+}
+
+/* yy_get_previous_state - get the state just before the EOB char was reached */
+
+    static yy_state_type yy_get_previous_state (void)
+{
+	yy_state_type yy_current_state;
+	char *yy_cp;
+    
+	yy_current_state = (yy_start);
+
+	for ( yy_cp = (yytext_ptr) + YY_MORE_ADJ; yy_cp < (yy_c_buf_p); ++yy_cp )
+		{
+		YY_CHAR yy_c = (*yy_cp ? yy_ec[YY_SC_TO_UI(*yy_cp)] : 1);
+		if ( yy_accept[yy_current_state] )
+			{
+			(yy_last_accepting_state) = yy_current_state;
+			(yy_last_accepting_cpos) = yy_cp;
+			}
+		while ( yy_chk[yy_base[yy_current_state] + yy_c] != yy_current_state )
+			{
+			yy_current_state = (int) yy_def[yy_current_state];
+			if ( yy_current_state >= 295 )
+				yy_c = yy_meta[yy_c];
+			}
+		yy_current_state = yy_nxt[yy_base[yy_current_state] + yy_c];
+		}
+
+	return yy_current_state;
+}
+
+/* yy_try_NUL_trans - try to make a transition on the NUL character
+ *
+ * synopsis
+ *	next_state = yy_try_NUL_trans( current_state );
+ */
+    static yy_state_type yy_try_NUL_trans  (yy_state_type yy_current_state )
+{
+	int yy_is_jam;
+    	char *yy_cp = (yy_c_buf_p);
+
+	YY_CHAR yy_c = 1;
+	if ( yy_accept[yy_current_state] )
+		{
+		(yy_last_accepting_state) = yy_current_state;
+		(yy_last_accepting_cpos) = yy_cp;
+		}
+	while ( yy_chk[yy_base[yy_current_state] + yy_c] != yy_current_state )
+		{
+		yy_current_state = (int) yy_def[yy_current_state];
+		if ( yy_current_state >= 295 )
+			yy_c = yy_meta[yy_c];
+		}
+	yy_current_state = yy_nxt[yy_base[yy_current_state] + yy_c];
+	yy_is_jam = (yy_current_state == 294);
+
+		return yy_is_jam ? 0 : yy_current_state;
+}
+
+#ifndef YY_NO_UNPUT
+
+#endif
+
+#ifndef YY_NO_INPUT
+#ifdef __cplusplus
+    static int yyinput (void)
+#else
+    static int input  (void)
+#endif
+
+{
+	int c;
+    
+	*(yy_c_buf_p) = (yy_hold_char);
+
+	if ( *(yy_c_buf_p) == YY_END_OF_BUFFER_CHAR )
+		{
+		/* yy_c_buf_p now points to the character we want to return.
+		 * If this occurs *before* the EOB characters, then it's a
+		 * valid NUL; if not, then we've hit the end of the buffer.
+		 */
+		if ( (yy_c_buf_p) < &YY_CURRENT_BUFFER_LVALUE->yy_ch_buf[(yy_n_chars)] )
+			/* This was really a NUL. */
+			*(yy_c_buf_p) = '\0';
+
+		else
+			{ /* need more input */
+			int offset = (int) ((yy_c_buf_p) - (yytext_ptr));
+			++(yy_c_buf_p);
+
+			switch ( yy_get_next_buffer(  ) )
+				{
+				case EOB_ACT_LAST_MATCH:
+					/* This happens because yy_g_n_b()
+					 * sees that we've accumulated a
+					 * token and flags that we need to
+					 * try matching the token before
+					 * proceeding.  But for input(),
+					 * there's no matching to consider.
+					 * So convert the EOB_ACT_LAST_MATCH
+					 * to EOB_ACT_END_OF_FILE.
+					 */
+
+					/* Reset buffer status. */
+					yyrestart( yyin );
+
+					/*FALLTHROUGH*/
+
+				case EOB_ACT_END_OF_FILE:
+					{
+					if ( yywrap(  ) )
+						return 0;
+
+					if ( ! (yy_did_buffer_switch_on_eof) )
+						YY_NEW_FILE;
+#ifdef __cplusplus
+					return yyinput();
+#else
+					return input();
+#endif
+					}
+
+				case EOB_ACT_CONTINUE_SCAN:
+					(yy_c_buf_p) = (yytext_ptr) + offset;
+					break;
+				}
+			}
+		}
+
+	c = *(unsigned char *) (yy_c_buf_p);	/* cast for 8-bit char's */
+	*(yy_c_buf_p) = '\0';	/* preserve yytext */
+	(yy_hold_char) = *++(yy_c_buf_p);
+
+	return c;
+}
+#endif	/* ifndef YY_NO_INPUT */
+
+/** Immediately switch to a different input stream.
+ * @param input_file A readable stream.
+ * 
+ * @note This function does not reset the start condition to @c INITIAL .
+ */
+    void yyrestart  (FILE * input_file )
+{
+    
+	if ( ! YY_CURRENT_BUFFER ){
+        yyensure_buffer_stack ();
+		YY_CURRENT_BUFFER_LVALUE =
+            yy_create_buffer( yyin, YY_BUF_SIZE );
+	}
+
+	yy_init_buffer( YY_CURRENT_BUFFER, input_file );
+	yy_load_buffer_state(  );
+}
+
+/** Switch to a different input buffer.
+ * @param new_buffer The new input buffer.
+ * 
+ */
+    void yy_switch_to_buffer  (YY_BUFFER_STATE  new_buffer )
+{
+    
+	/* TODO. We should be able to replace this entire function body
+	 * with
+	 *		yypop_buffer_state();
+	 *		yypush_buffer_state(new_buffer);
+     */
+	yyensure_buffer_stack ();
+	if ( YY_CURRENT_BUFFER == new_buffer )
+		return;
+
+	if ( YY_CURRENT_BUFFER )
+		{
+		/* Flush out information for old buffer. */
+		*(yy_c_buf_p) = (yy_hold_char);
+		YY_CURRENT_BUFFER_LVALUE->yy_buf_pos = (yy_c_buf_p);
+		YY_CURRENT_BUFFER_LVALUE->yy_n_chars = (yy_n_chars);
+		}
+
+	YY_CURRENT_BUFFER_LVALUE = new_buffer;
+	yy_load_buffer_state(  );
+
+	/* We don't actually know whether we did this switch during
+	 * EOF (yywrap()) processing, but the only time this flag
+	 * is looked at is after yywrap() is called, so it's safe
+	 * to go ahead and always set it.
+	 */
+	(yy_did_buffer_switch_on_eof) = 1;
+}
+
+static void yy_load_buffer_state  (void)
+{
+    	(yy_n_chars) = YY_CURRENT_BUFFER_LVALUE->yy_n_chars;
+	(yytext_ptr) = (yy_c_buf_p) = YY_CURRENT_BUFFER_LVALUE->yy_buf_pos;
+	yyin = YY_CURRENT_BUFFER_LVALUE->yy_input_file;
+	(yy_hold_char) = *(yy_c_buf_p);
+}
+
+/** Allocate and initialize an input buffer state.
+ * @param file A readable stream.
+ * @param size The character buffer size in bytes. When in doubt, use @c YY_BUF_SIZE.
+ * 
+ * @return the allocated buffer state.
+ */
+    YY_BUFFER_STATE yy_create_buffer  (FILE * file, int  size )
+{
+	YY_BUFFER_STATE b;
+    
+	b = (YY_BUFFER_STATE) yyalloc( sizeof( struct yy_buffer_state )  );
+	if ( ! b )
+		YY_FATAL_ERROR( "out of dynamic memory in yy_create_buffer()" );
+
+	b->yy_buf_size = size;
+
+	/* yy_ch_buf has to be 2 characters longer than the size given because
+	 * we need to put in 2 end-of-buffer characters.
+	 */
+	b->yy_ch_buf = (char *) yyalloc( (yy_size_t) (b->yy_buf_size + 2)  );
+	if ( ! b->yy_ch_buf )
+		YY_FATAL_ERROR( "out of dynamic memory in yy_create_buffer()" );
+
+	b->yy_is_our_buffer = 1;
+
+	yy_init_buffer( b, file );
+
+	return b;
+}
+
+/** Destroy the buffer.
+ * @param b a buffer created with yy_create_buffer()
+ * 
+ */
+    void yy_delete_buffer (YY_BUFFER_STATE  b )
+{
+    
+	if ( ! b )
+		return;
+
+	if ( b == YY_CURRENT_BUFFER ) /* Not sure if we should pop here. */
+		YY_CURRENT_BUFFER_LVALUE = (YY_BUFFER_STATE) 0;
+
+	if ( b->yy_is_our_buffer )
+		yyfree( (void *) b->yy_ch_buf  );
+
+	yyfree( (void *) b  );
+}
+
+/* Initializes or reinitializes a buffer.
+ * This function is sometimes called more than once on the same buffer,
+ * such as during a yyrestart() or at EOF.
+ */
+    static void yy_init_buffer  (YY_BUFFER_STATE  b, FILE * file )
+
+{
+	int oerrno = errno;
+    
+	yy_flush_buffer( b );
+
+	b->yy_input_file = file;
+	b->yy_fill_buffer = 1;
+
+    /* If b is the current buffer, then yy_init_buffer was _probably_
+     * called from yyrestart() or through yy_get_next_buffer.
+     * In that case, we don't want to reset the lineno or column.
+     */
+    if (b != YY_CURRENT_BUFFER){
+        b->yy_bs_lineno = 1;
+        b->yy_bs_column = 0;
+    }
+
+        b->yy_is_interactive = 0;
+    
+	errno = oerrno;
+}
+
+/** Discard all buffered characters. On the next scan, YY_INPUT will be called.
+ * @param b the buffer state to be flushed, usually @c YY_CURRENT_BUFFER.
+ * 
+ */
+    void yy_flush_buffer (YY_BUFFER_STATE  b )
+{
+    	if ( ! b )
+		return;
+
+	b->yy_n_chars = 0;
+
+	/* We always need two end-of-buffer characters.  The first causes
+	 * a transition to the end-of-buffer state.  The second causes
+	 * a jam in that state.
+	 */
+	b->yy_ch_buf[0] = YY_END_OF_BUFFER_CHAR;
+	b->yy_ch_buf[1] = YY_END_OF_BUFFER_CHAR;
+
+	b->yy_buf_pos = &b->yy_ch_buf[0];
+
+	b->yy_at_bol = 1;
+	b->yy_buffer_status = YY_BUFFER_NEW;
+
+	if ( b == YY_CURRENT_BUFFER )
+		yy_load_buffer_state(  );
+}
+
+/** Pushes the new state onto the stack. The new state becomes
+ *  the current state. This function will allocate the stack
+ *  if necessary.
+ *  @param new_buffer The new state.
+ *  
+ */
+void yypush_buffer_state (YY_BUFFER_STATE new_buffer )
+{
+    	if (new_buffer == NULL)
+		return;
+
+	yyensure_buffer_stack();
+
+	/* This block is copied from yy_switch_to_buffer. */
+	if ( YY_CURRENT_BUFFER )
+		{
+		/* Flush out information for old buffer. */
+		*(yy_c_buf_p) = (yy_hold_char);
+		YY_CURRENT_BUFFER_LVALUE->yy_buf_pos = (yy_c_buf_p);
+		YY_CURRENT_BUFFER_LVALUE->yy_n_chars = (yy_n_chars);
+		}
+
+	/* Only push if top exists. Otherwise, replace top. */
+	if (YY_CURRENT_BUFFER)
+		(yy_buffer_stack_top)++;
+	YY_CURRENT_BUFFER_LVALUE = new_buffer;
+
+	/* copied from yy_switch_to_buffer. */
+	yy_load_buffer_state(  );
+	(yy_did_buffer_switch_on_eof) = 1;
+}
+
+/** Removes and deletes the top of the stack, if present.
+ *  The next element becomes the new top.
+ *  
+ */
+void yypop_buffer_state (void)
+{
+    	if (!YY_CURRENT_BUFFER)
+		return;
+
+	yy_delete_buffer(YY_CURRENT_BUFFER );
+	YY_CURRENT_BUFFER_LVALUE = NULL;
+	if ((yy_buffer_stack_top) > 0)
+		--(yy_buffer_stack_top);
+
+	if (YY_CURRENT_BUFFER) {
+		yy_load_buffer_state(  );
+		(yy_did_buffer_switch_on_eof) = 1;
+	}
+}
+
+/* Allocates the stack if it does not exist.
+ *  Guarantees space for at least one push.
+ */
+static void yyensure_buffer_stack (void)
+{
+	yy_size_t num_to_alloc;
+    
+	if (!(yy_buffer_stack)) {
+
+		/* First allocation is just for 2 elements, since we don't know if this
+		 * scanner will even need a stack. We use 2 instead of 1 to avoid an
+		 * immediate realloc on the next call.
+         */
+      num_to_alloc = 1; /* After all that talk, this was set to 1 anyways... */
+		(yy_buffer_stack) = (struct yy_buffer_state**)yyalloc
+								(num_to_alloc * sizeof(struct yy_buffer_state*)
+								);
+		if ( ! (yy_buffer_stack) )
+			YY_FATAL_ERROR( "out of dynamic memory in yyensure_buffer_stack()" );
+
+		memset((yy_buffer_stack), 0, num_to_alloc * sizeof(struct yy_buffer_state*));
+
+		(yy_buffer_stack_max) = num_to_alloc;
+		(yy_buffer_stack_top) = 0;
+		return;
+	}
+
+	if ((yy_buffer_stack_top) >= ((yy_buffer_stack_max)) - 1){
+
+		/* Increase the buffer to prepare for a possible push. */
+		yy_size_t grow_size = 8 /* arbitrary grow size */;
+
+		num_to_alloc = (yy_buffer_stack_max) + grow_size;
+		(yy_buffer_stack) = (struct yy_buffer_state**)yyrealloc
+								((yy_buffer_stack),
+								num_to_alloc * sizeof(struct yy_buffer_state*)
+								);
+		if ( ! (yy_buffer_stack) )
+			YY_FATAL_ERROR( "out of dynamic memory in yyensure_buffer_stack()" );
+
+		/* zero only the new slots.*/
+		memset((yy_buffer_stack) + (yy_buffer_stack_max), 0, grow_size * sizeof(struct yy_buffer_state*));
+		(yy_buffer_stack_max) = num_to_alloc;
+	}
+}
+
+/** Setup the input buffer state to scan directly from a user-specified character buffer.
+ * @param base the character buffer
+ * @param size the size in bytes of the character buffer
+ * 
+ * @return the newly allocated buffer state object.
+ */
+YY_BUFFER_STATE yy_scan_buffer  (char * base, yy_size_t  size )
+{
+	YY_BUFFER_STATE b;
+    
+	if ( size < 2 ||
+	     base[size-2] != YY_END_OF_BUFFER_CHAR ||
+	     base[size-1] != YY_END_OF_BUFFER_CHAR )
+		/* They forgot to leave room for the EOB's. */
+		return NULL;
+
+	b = (YY_BUFFER_STATE) yyalloc( sizeof( struct yy_buffer_state )  );
+	if ( ! b )
+		YY_FATAL_ERROR( "out of dynamic memory in yy_scan_buffer()" );
+
+	b->yy_buf_size = (int) (size - 2);	/* "- 2" to take care of EOB's */
+	b->yy_buf_pos = b->yy_ch_buf = base;
+	b->yy_is_our_buffer = 0;
+	b->yy_input_file = NULL;
+	b->yy_n_chars = b->yy_buf_size;
+	b->yy_is_interactive = 0;
+	b->yy_at_bol = 1;
+	b->yy_fill_buffer = 0;
+	b->yy_buffer_status = YY_BUFFER_NEW;
+
+	yy_switch_to_buffer( b  );
+
+	return b;
+}
+
+/** Setup the input buffer state to scan a string. The next call to yylex() will
+ * scan from a @e copy of @a str.
+ * @param yystr a NUL-terminated string to scan
+ * 
+ * @return the newly allocated buffer state object.
+ * @note If you want to scan bytes that may contain NUL values, then use
+ *       yy_scan_bytes() instead.
+ */
+YY_BUFFER_STATE yy_scan_string (const char * yystr )
+{
+    
+	return yy_scan_bytes( yystr, (int) strlen(yystr) );
+}
+
+/** Setup the input buffer state to scan the given bytes. The next call to yylex() will
+ * scan from a @e copy of @a bytes.
+ * @param yybytes the byte buffer to scan
+ * @param _yybytes_len the number of bytes in the buffer pointed to by @a bytes.
+ * 
+ * @return the newly allocated buffer state object.
+ */
+YY_BUFFER_STATE yy_scan_bytes  (const char * yybytes, int  _yybytes_len )
+{
+	YY_BUFFER_STATE b;
+	char *buf;
+	yy_size_t n;
+	int i;
+    
+	/* Get memory for full buffer, including space for trailing EOB's. */
+	n = (yy_size_t) (_yybytes_len + 2);
+	buf = (char *) yyalloc( n  );
+	if ( ! buf )
+		YY_FATAL_ERROR( "out of dynamic memory in yy_scan_bytes()" );
+
+	for ( i = 0; i < _yybytes_len; ++i )
+		buf[i] = yybytes[i];
+
+	buf[_yybytes_len] = buf[_yybytes_len+1] = YY_END_OF_BUFFER_CHAR;
+
+	b = yy_scan_buffer( buf, n );
+	if ( ! b )
+		YY_FATAL_ERROR( "bad buffer in yy_scan_bytes()" );
+
+	/* It's okay to grow etc. this buffer, and we should throw it
+	 * away when we're done.
+	 */
+	b->yy_is_our_buffer = 1;
+
+	return b;
+}
+
+#ifndef YY_EXIT_FAILURE
+#define YY_EXIT_FAILURE 2
+#endif
+
+static void yynoreturn yy_fatal_error (const char* msg )
+{
+			fprintf( stderr, "%s\n", msg );
+	exit( YY_EXIT_FAILURE );
+}
+
+/* Redefine yyless() so it works in section 3 code. */
+
+#undef yyless
+#define yyless(n) \
+	do \
+		{ \
+		/* Undo effects of setting up yytext. */ \
+        int yyless_macro_arg = (n); \
+        YY_LESS_LINENO(yyless_macro_arg);\
+		yytext[yyleng] = (yy_hold_char); \
+		(yy_c_buf_p) = yytext + yyless_macro_arg; \
+		(yy_hold_char) = *(yy_c_buf_p); \
+		*(yy_c_buf_p) = '\0'; \
+		yyleng = yyless_macro_arg; \
+		} \
+	while ( 0 )
+
+/* Accessor  methods (get/set functions) to struct members. */
+
+/** Get the current line number.
+ * 
+ */
+int yyget_lineno  (void)
+{
+    
+    return yylineno;
+}
+
+/** Get the input stream.
+ * 
+ */
+FILE *yyget_in  (void)
+{
+        return yyin;
+}
+
+/** Get the output stream.
+ * 
+ */
+FILE *yyget_out  (void)
+{
+        return yyout;
+}
+
+/** Get the length of the current token.
+ * 
+ */
+int yyget_leng  (void)
+{
+        return yyleng;
+}
+
+/** Get the current token.
+ * 
+ */
+
+char *yyget_text  (void)
+{
+        return yytext;
+}
+
+/** Set the current line number.
+ * @param _line_number line number
+ * 
+ */
+void yyset_lineno (int  _line_number )
+{
+    
+    yylineno = _line_number;
+}
+
+/** Set the input stream. This does not discard the current
+ * input buffer.
+ * @param _in_str A readable stream.
+ * 
+ * @see yy_switch_to_buffer
+ */
+void yyset_in (FILE *  _in_str )
+{
+        yyin = _in_str ;
+}
+
+void yyset_out (FILE *  _out_str )
+{
+        yyout = _out_str ;
+}
+
+int yyget_debug  (void)
+{
+        return yy_flex_debug;
+}
+
+void yyset_debug (int  _bdebug )
+{
+        yy_flex_debug = _bdebug ;
+}
+
+static int yy_init_globals (void)
+{
+        /* Initialization is the same as for the non-reentrant scanner.
+     * This function is called from yylex_destroy(), so don't allocate here.
+     */
+
+    (yy_buffer_stack) = NULL;
+    (yy_buffer_stack_top) = 0;
+    (yy_buffer_stack_max) = 0;
+    (yy_c_buf_p) = NULL;
+    (yy_init) = 0;
+    (yy_start) = 0;
+
+/* Defined in main.c */
+#ifdef YY_STDINIT
+    yyin = stdin;
+    yyout = stdout;
+#else
+    yyin = NULL;
+    yyout = NULL;
+#endif
+
+    /* For future reference: Set errno on error, since we are called by
+     * yylex_init()
+     */
+    return 0;
+}
+
+/* yylex_destroy is for both reentrant and non-reentrant scanners. */
+int yylex_destroy  (void)
+{
+    
+    /* Pop the buffer stack, destroying each element. */
+	while(YY_CURRENT_BUFFER){
+		yy_delete_buffer( YY_CURRENT_BUFFER  );
+		YY_CURRENT_BUFFER_LVALUE = NULL;
+		yypop_buffer_state();
+	}
+
+	/* Destroy the stack itself. */
+	yyfree((yy_buffer_stack) );
+	(yy_buffer_stack) = NULL;
+
+    /* Reset the globals. This is important in a non-reentrant scanner so the next time
+     * yylex() is called, initialization will occur. */
+    yy_init_globals( );
+
+    return 0;
+}
+
+/*
+ * Internal utility routines.
+ */
+
+#ifndef yytext_ptr
+static void yy_flex_strncpy (char* s1, const char * s2, int n )
+{
+		
+	int i;
+	for ( i = 0; i < n; ++i )
+		s1[i] = s2[i];
+}
+#endif
+
+#ifdef YY_NEED_STRLEN
+static int yy_flex_strlen (const char * s )
+{
+	int n;
+	for ( n = 0; s[n]; ++n )
+		;
+
+	return n;
+}
+#endif
+
+void *yyalloc (yy_size_t  size )
+{
+			return malloc(size);
+}
+
+void *yyrealloc  (void * ptr, yy_size_t  size )
+{
+		
+	/* The cast to (char *) in the following accommodates both
+	 * implementations that use char* generic pointers, and those
+	 * that use void* generic pointers.  It works with the latter
+	 * because both ANSI C and C++ allow castless assignment from
+	 * any pointer type to void*, and deal with argument conversions
+	 * as though doing an assignment.
+	 */
+	return realloc(ptr, size);
+}
+
+void yyfree (void * ptr )
+{
+			free( (char *) ptr );	/* see yyrealloc() for (char *) cast */
+}
+
+#define YYTABLES_NAME "yytables"
+
+#line 213 "repl_scanner.l"
+
+
+/* LCOV_EXCL_STOP */
+
+static void
+startlit(void)
+{
+	initStringInfo(&litbuf);
+}
+
+static char *
+litbufdup(void)
+{
+	return litbuf.data;
+}
+
+static void
+addlit(char *ytext, int yleng)
+{
+	appendBinaryStringInfo(&litbuf, ytext, yleng);
+}
+
+static void
+addlitchar(unsigned char ychar)
+{
+	appendStringInfoChar(&litbuf, ychar);
+}
+
+void
+yyerror(const char *message)
+{
+	ereport(ERROR,
+			(errcode(ERRCODE_SYNTAX_ERROR),
+			 errmsg_internal("%s", message)));
+}
+
+
+void
+replication_scanner_init(const char *str)
+{
+	Size		slen = strlen(str);
+	char	   *scanbuf;
+
+	/*
+	 * Might be left over after ereport()
+	 */
+	if (YY_CURRENT_BUFFER)
+		yy_delete_buffer(YY_CURRENT_BUFFER);
+
+	/*
+	 * Make a scan buffer with special termination needed by flex.
+	 */
+	scanbuf = (char *) palloc(slen + 2);
+	memcpy(scanbuf, str, slen);
+	scanbuf[slen] = scanbuf[slen + 1] = YY_END_OF_BUFFER_CHAR;
+	scanbufhandle = yy_scan_buffer(scanbuf, slen + 2);
+
+	/* Make sure we start in proper state */
+	BEGIN(INITIAL);
+	repl_pushed_back_token = 0;
+}
+
+void
+replication_scanner_finish(void)
+{
+	yy_delete_buffer(scanbufhandle);
+	scanbufhandle = NULL;
+}
+
+/*
+ * Check to see if the first token of a command is a WalSender keyword.
+ *
+ * To keep repl_scanner.l minimal, we don't ask it to know every construct
+ * that the core lexer knows.  Therefore, we daren't lex more than the
+ * first token of a general SQL command.  That will usually look like an
+ * IDENT token here, although some other cases are possible.
+ */
+bool
+replication_scanner_is_replication_command(void)
+{
+	int			first_token = replication_yylex();
+
+	switch (first_token)
+	{
+		case K_IDENTIFY_SYSTEM:
+		case K_BASE_BACKUP:
+		case K_START_REPLICATION:
+		case K_CREATE_REPLICATION_SLOT:
+		case K_DROP_REPLICATION_SLOT:
+		case K_TIMELINE_HISTORY:
+		case K_SHOW:
+			/* Yes; push back the first token so we can parse later. */
+			repl_pushed_back_token = first_token;
+			return true;
+		default:
+			/* Nope; we don't bother to push back the token. */
+			return false;
+	}
+}
+
diff --git a/src/backend/replication/repl_scanner.l b/src/backend/replication/repl_scanner.l
new file mode 100644
index 0000000..8a075e2
--- /dev/null
+++ b/src/backend/replication/repl_scanner.l
@@ -0,0 +1,310 @@
+%{
+/*-------------------------------------------------------------------------
+ *
+ * repl_scanner.l
+ *	  a lexical scanner for the replication commands
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/repl_scanner.l
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "utils/builtins.h"
+#include "parser/scansup.h"
+
+/* Avoid exit() on fatal scanner errors (a bit ugly -- see yy_fatal_error) */
+#undef fprintf
+#define fprintf(file, fmt, msg)  fprintf_to_ereport(fmt, msg)
+
+static void
+fprintf_to_ereport(const char *fmt, const char *msg)
+{
+	ereport(ERROR, (errmsg_internal("%s", msg)));
+}
+
+/* Handle to the buffer that the lexer uses internally */
+static YY_BUFFER_STATE scanbufhandle;
+
+/* Pushed-back token (we only handle one) */
+static int	repl_pushed_back_token;
+
+/* Work area for collecting literals */
+static StringInfoData litbuf;
+
+static void startlit(void);
+static char *litbufdup(void);
+static void addlit(char *ytext, int yleng);
+static void addlitchar(unsigned char ychar);
+
+/* LCOV_EXCL_START */
+
+%}
+
+%option 8bit
+%option never-interactive
+%option nodefault
+%option noinput
+%option nounput
+%option noyywrap
+%option warn
+%option prefix="replication_yy"
+
+/*
+ * Exclusive states:
+ *  <xd> delimited identifiers (double-quoted identifiers)
+ *  <xq> standard single-quoted strings
+ */
+%x xd
+%x xq
+
+space			[ \t\n\r\f]
+
+quote			'
+quotestop		{quote}
+
+/* Extended quote
+ * xqdouble implements embedded quote, ''''
+ */
+xqstart			{quote}
+xqdouble		{quote}{quote}
+xqinside		[^']+
+
+/* Double quote
+ * Allows embedded spaces and other special characters into identifiers.
+ */
+dquote			\"
+xdstart			{dquote}
+xdstop			{dquote}
+xddouble		{dquote}{dquote}
+xdinside		[^"]+
+
+digit			[0-9]
+hexdigit		[0-9A-Fa-f]
+
+ident_start		[A-Za-z\200-\377_]
+ident_cont		[A-Za-z\200-\377_0-9\$]
+
+identifier		{ident_start}{ident_cont}*
+
+%%
+
+%{
+	/* This code is inserted at the start of replication_yylex() */
+
+	/* If we have a pushed-back token, return that. */
+	if (repl_pushed_back_token)
+	{
+		int			result = repl_pushed_back_token;
+
+		repl_pushed_back_token = 0;
+		return result;
+	}
+%}
+
+BASE_BACKUP			{ return K_BASE_BACKUP; }
+FAST			{ return K_FAST; }
+IDENTIFY_SYSTEM		{ return K_IDENTIFY_SYSTEM; }
+SHOW		{ return K_SHOW; }
+LABEL			{ return K_LABEL; }
+NOWAIT			{ return K_NOWAIT; }
+PROGRESS			{ return K_PROGRESS; }
+MAX_RATE		{ return K_MAX_RATE; }
+WAL			{ return K_WAL; }
+TABLESPACE_MAP			{ return K_TABLESPACE_MAP; }
+NOVERIFY_CHECKSUMS	{ return K_NOVERIFY_CHECKSUMS; }
+TIMELINE			{ return K_TIMELINE; }
+START_REPLICATION	{ return K_START_REPLICATION; }
+CREATE_REPLICATION_SLOT		{ return K_CREATE_REPLICATION_SLOT; }
+DROP_REPLICATION_SLOT		{ return K_DROP_REPLICATION_SLOT; }
+TIMELINE_HISTORY	{ return K_TIMELINE_HISTORY; }
+PHYSICAL			{ return K_PHYSICAL; }
+RESERVE_WAL			{ return K_RESERVE_WAL; }
+LOGICAL				{ return K_LOGICAL; }
+SLOT				{ return K_SLOT; }
+TEMPORARY			{ return K_TEMPORARY; }
+EXPORT_SNAPSHOT		{ return K_EXPORT_SNAPSHOT; }
+NOEXPORT_SNAPSHOT	{ return K_NOEXPORT_SNAPSHOT; }
+USE_SNAPSHOT		{ return K_USE_SNAPSHOT; }
+WAIT				{ return K_WAIT; }
+MANIFEST			{ return K_MANIFEST; }
+MANIFEST_CHECKSUMS	{ return K_MANIFEST_CHECKSUMS; }
+
+{space}+		{ /* do nothing */ }
+
+{digit}+		{
+					yylval.uintval = strtoul(yytext, NULL, 10);
+					return UCONST;
+				}
+
+{hexdigit}+\/{hexdigit}+		{
+					uint32	hi,
+							lo;
+					if (sscanf(yytext, "%X/%X", &hi, &lo) != 2)
+						yyerror("invalid streaming start location");
+					yylval.recptr = ((uint64) hi) << 32 | lo;
+					return RECPTR;
+				}
+
+{xqstart}		{
+					BEGIN(xq);
+					startlit();
+				}
+
+<xq>{quotestop}	{
+					yyless(1);
+					BEGIN(INITIAL);
+					yylval.str = litbufdup();
+					return SCONST;
+				}
+
+<xq>{xqdouble}	{
+					addlitchar('\'');
+				}
+
+<xq>{xqinside}  {
+					addlit(yytext, yyleng);
+				}
+
+{xdstart}		{
+					BEGIN(xd);
+					startlit();
+				}
+
+<xd>{xdstop}	{
+					int len;
+					yyless(1);
+					BEGIN(INITIAL);
+					yylval.str = litbufdup();
+					len = strlen(yylval.str);
+					truncate_identifier(yylval.str, len, true);
+					return IDENT;
+				}
+
+<xd>{xdinside}  {
+					addlit(yytext, yyleng);
+				}
+
+{identifier}	{
+					int len = strlen(yytext);
+
+					yylval.str = downcase_truncate_identifier(yytext, len, true);
+					return IDENT;
+				}
+
+.				{
+					/* Any char not recognized above is returned as itself */
+					return yytext[0];
+				}
+
+<xq,xd><<EOF>>	{ yyerror("unterminated quoted string"); }
+
+
+<<EOF>>			{
+					yyterminate();
+				}
+
+%%
+
+/* LCOV_EXCL_STOP */
+
+static void
+startlit(void)
+{
+	initStringInfo(&litbuf);
+}
+
+static char *
+litbufdup(void)
+{
+	return litbuf.data;
+}
+
+static void
+addlit(char *ytext, int yleng)
+{
+	appendBinaryStringInfo(&litbuf, ytext, yleng);
+}
+
+static void
+addlitchar(unsigned char ychar)
+{
+	appendStringInfoChar(&litbuf, ychar);
+}
+
+void
+yyerror(const char *message)
+{
+	ereport(ERROR,
+			(errcode(ERRCODE_SYNTAX_ERROR),
+			 errmsg_internal("%s", message)));
+}
+
+
+void
+replication_scanner_init(const char *str)
+{
+	Size		slen = strlen(str);
+	char	   *scanbuf;
+
+	/*
+	 * Might be left over after ereport()
+	 */
+	if (YY_CURRENT_BUFFER)
+		yy_delete_buffer(YY_CURRENT_BUFFER);
+
+	/*
+	 * Make a scan buffer with special termination needed by flex.
+	 */
+	scanbuf = (char *) palloc(slen + 2);
+	memcpy(scanbuf, str, slen);
+	scanbuf[slen] = scanbuf[slen + 1] = YY_END_OF_BUFFER_CHAR;
+	scanbufhandle = yy_scan_buffer(scanbuf, slen + 2);
+
+	/* Make sure we start in proper state */
+	BEGIN(INITIAL);
+	repl_pushed_back_token = 0;
+}
+
+void
+replication_scanner_finish(void)
+{
+	yy_delete_buffer(scanbufhandle);
+	scanbufhandle = NULL;
+}
+
+/*
+ * Check to see if the first token of a command is a WalSender keyword.
+ *
+ * To keep repl_scanner.l minimal, we don't ask it to know every construct
+ * that the core lexer knows.  Therefore, we daren't lex more than the
+ * first token of a general SQL command.  That will usually look like an
+ * IDENT token here, although some other cases are possible.
+ */
+bool
+replication_scanner_is_replication_command(void)
+{
+	int			first_token = replication_yylex();
+
+	switch (first_token)
+	{
+		case K_IDENTIFY_SYSTEM:
+		case K_BASE_BACKUP:
+		case K_START_REPLICATION:
+		case K_CREATE_REPLICATION_SLOT:
+		case K_DROP_REPLICATION_SLOT:
+		case K_TIMELINE_HISTORY:
+		case K_SHOW:
+			/* Yes; push back the first token so we can parse later. */
+			repl_pushed_back_token = first_token;
+			return true;
+		default:
+			/* Nope; we don't bother to push back the token. */
+			return false;
+	}
+}
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
new file mode 100644
index 0000000..3f34832
--- /dev/null
+++ b/src/backend/replication/slot.c
@@ -0,0 +1,1861 @@
+/*-------------------------------------------------------------------------
+ *
+ * slot.c
+ *	   Replication slot management.
+ *
+ *
+ * Copyright (c) 2012-2021, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/slot.c
+ *
+ * NOTES
+ *
+ * Replication slots are used to keep state about replication streams
+ * originating from this cluster.  Their primary purpose is to prevent the
+ * premature removal of WAL or of old tuple versions in a manner that would
+ * interfere with replication; they are also useful for monitoring purposes.
+ * Slots need to be permanent (to allow restarts), crash-safe, and allocatable
+ * on standbys (to support cascading setups).  The requirement that slots be
+ * usable on standbys precludes storing them in the system catalogs.
+ *
+ * Each replication slot gets its own directory inside the $PGDATA/pg_replslot
+ * directory. Inside that directory the state file will contain the slot's
+ * own data. Additional data can be stored alongside that file if required.
+ * While the server is running, the state data is also cached in memory for
+ * efficiency.
+ *
+ * ReplicationSlotAllocationLock must be taken in exclusive mode to allocate
+ * or free a slot. ReplicationSlotControlLock must be taken in shared mode
+ * to iterate over the slots, and in exclusive mode to change the in_use flag
+ * of a slot.  The remaining data in each slot is protected by its mutex.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <unistd.h>
+#include <sys/stat.h>
+
+#include "access/transam.h"
+#include "access/xlog_internal.h"
+#include "common/string.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "replication/slot.h"
+#include "storage/fd.h"
+#include "storage/proc.h"
+#include "storage/procarray.h"
+#include "utils/builtins.h"
+
+/*
+ * Replication slot on-disk data structure.
+ */
+typedef struct ReplicationSlotOnDisk
+{
+	/* first part of this struct needs to be version independent */
+
+	/* data not covered by checksum */
+	uint32		magic;
+	pg_crc32c	checksum;
+
+	/* data covered by checksum */
+	uint32		version;
+	uint32		length;
+
+	/*
+	 * The actual data in the slot that follows can differ based on the above
+	 * 'version'.
+	 */
+
+	ReplicationSlotPersistentData slotdata;
+} ReplicationSlotOnDisk;
+
+/* size of version independent data */
+#define ReplicationSlotOnDiskConstantSize \
+	offsetof(ReplicationSlotOnDisk, slotdata)
+/* size of the part of the slot not covered by the checksum */
+#define SnapBuildOnDiskNotChecksummedSize \
+	offsetof(ReplicationSlotOnDisk, version)
+/* size of the part covered by the checksum */
+#define SnapBuildOnDiskChecksummedSize \
+	sizeof(ReplicationSlotOnDisk) - SnapBuildOnDiskNotChecksummedSize
+/* size of the slot data that is version dependent */
+#define ReplicationSlotOnDiskV2Size \
+	sizeof(ReplicationSlotOnDisk) - ReplicationSlotOnDiskConstantSize
+
+#define SLOT_MAGIC		0x1051CA1	/* format identifier */
+#define SLOT_VERSION	2		/* version for new files */
+
+/* Control array for replication slot management */
+ReplicationSlotCtlData *ReplicationSlotCtl = NULL;
+
+/* My backend's replication slot in the shared memory array */
+ReplicationSlot *MyReplicationSlot = NULL;
+
+/* GUCs */
+int			max_replication_slots = 0;	/* the maximum number of replication
+										 * slots */
+
+static void ReplicationSlotDropAcquired(void);
+static void ReplicationSlotDropPtr(ReplicationSlot *slot);
+
+/* internal persistency functions */
+static void RestoreSlotFromDisk(const char *name);
+static void CreateSlotOnDisk(ReplicationSlot *slot);
+static void SaveSlotToPath(ReplicationSlot *slot, const char *path, int elevel);
+
+/*
+ * Report shared-memory space needed by ReplicationSlotsShmemInit.
+ */
+Size
+ReplicationSlotsShmemSize(void)
+{
+	Size		size = 0;
+
+	if (max_replication_slots == 0)
+		return size;
+
+	size = offsetof(ReplicationSlotCtlData, replication_slots);
+	size = add_size(size,
+					mul_size(max_replication_slots, sizeof(ReplicationSlot)));
+
+	return size;
+}
+
+/*
+ * Allocate and initialize shared memory for replication slots.
+ */
+void
+ReplicationSlotsShmemInit(void)
+{
+	bool		found;
+
+	if (max_replication_slots == 0)
+		return;
+
+	ReplicationSlotCtl = (ReplicationSlotCtlData *)
+		ShmemInitStruct("ReplicationSlot Ctl", ReplicationSlotsShmemSize(),
+						&found);
+
+	if (!found)
+	{
+		int			i;
+
+		/* First time through, so initialize */
+		MemSet(ReplicationSlotCtl, 0, ReplicationSlotsShmemSize());
+
+		for (i = 0; i < max_replication_slots; i++)
+		{
+			ReplicationSlot *slot = &ReplicationSlotCtl->replication_slots[i];
+
+			/* everything else is zeroed by the memset above */
+			SpinLockInit(&slot->mutex);
+			LWLockInitialize(&slot->io_in_progress_lock,
+							 LWTRANCHE_REPLICATION_SLOT_IO);
+			ConditionVariableInit(&slot->active_cv);
+		}
+	}
+}
+
+/*
+ * Check whether the passed slot name is valid and report errors at elevel.
+ *
+ * Slot names may consist out of [a-z0-9_]{1,NAMEDATALEN-1} which should allow
+ * the name to be used as a directory name on every supported OS.
+ *
+ * Returns whether the directory name is valid or not if elevel < ERROR.
+ */
+bool
+ReplicationSlotValidateName(const char *name, int elevel)
+{
+	const char *cp;
+
+	if (strlen(name) == 0)
+	{
+		ereport(elevel,
+				(errcode(ERRCODE_INVALID_NAME),
+				 errmsg("replication slot name \"%s\" is too short",
+						name)));
+		return false;
+	}
+
+	if (strlen(name) >= NAMEDATALEN)
+	{
+		ereport(elevel,
+				(errcode(ERRCODE_NAME_TOO_LONG),
+				 errmsg("replication slot name \"%s\" is too long",
+						name)));
+		return false;
+	}
+
+	for (cp = name; *cp; cp++)
+	{
+		if (!((*cp >= 'a' && *cp <= 'z')
+			  || (*cp >= '0' && *cp <= '9')
+			  || (*cp == '_')))
+		{
+			ereport(elevel,
+					(errcode(ERRCODE_INVALID_NAME),
+					 errmsg("replication slot name \"%s\" contains invalid character",
+							name),
+					 errhint("Replication slot names may only contain lower case letters, numbers, and the underscore character.")));
+			return false;
+		}
+	}
+	return true;
+}
+
+/*
+ * Create a new replication slot and mark it as used by this backend.
+ *
+ * name: Name of the slot
+ * db_specific: logical decoding is db specific; if the slot is going to
+ *	   be used for that pass true, otherwise false.
+ * two_phase: Allows decoding of prepared transactions. We allow this option
+ *     to be enabled only at the slot creation time. If we allow this option
+ *     to be changed during decoding then it is quite possible that we skip
+ *     prepare first time because this option was not enabled. Now next time
+ *     during getting changes, if the two_phase  option is enabled it can skip
+ *     prepare because by that time start decoding point has been moved. So the
+ *     user will only get commit prepared.
+ */
+void
+ReplicationSlotCreate(const char *name, bool db_specific,
+					  ReplicationSlotPersistency persistency, bool two_phase)
+{
+	ReplicationSlot *slot = NULL;
+	int			i;
+
+	Assert(MyReplicationSlot == NULL);
+
+	ReplicationSlotValidateName(name, ERROR);
+
+	/*
+	 * If some other backend ran this code concurrently with us, we'd likely
+	 * both allocate the same slot, and that would be bad.  We'd also be at
+	 * risk of missing a name collision.  Also, we don't want to try to create
+	 * a new slot while somebody's busy cleaning up an old one, because we
+	 * might both be monkeying with the same directory.
+	 */
+	LWLockAcquire(ReplicationSlotAllocationLock, LW_EXCLUSIVE);
+
+	/*
+	 * Check for name collision, and identify an allocatable slot.  We need to
+	 * hold ReplicationSlotControlLock in shared mode for this, so that nobody
+	 * else can change the in_use flags while we're looking at them.
+	 */
+	LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
+	for (i = 0; i < max_replication_slots; i++)
+	{
+		ReplicationSlot *s = &ReplicationSlotCtl->replication_slots[i];
+
+		if (s->in_use && strcmp(name, NameStr(s->data.name)) == 0)
+			ereport(ERROR,
+					(errcode(ERRCODE_DUPLICATE_OBJECT),
+					 errmsg("replication slot \"%s\" already exists", name)));
+		if (!s->in_use && slot == NULL)
+			slot = s;
+	}
+	LWLockRelease(ReplicationSlotControlLock);
+
+	/* If all slots are in use, we're out of luck. */
+	if (slot == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
+				 errmsg("all replication slots are in use"),
+				 errhint("Free one or increase max_replication_slots.")));
+
+	/*
+	 * Since this slot is not in use, nobody should be looking at any part of
+	 * it other than the in_use field unless they're trying to allocate it.
+	 * And since we hold ReplicationSlotAllocationLock, nobody except us can
+	 * be doing that.  So it's safe to initialize the slot.
+	 */
+	Assert(!slot->in_use);
+	Assert(slot->active_pid == 0);
+
+	/* first initialize persistent data */
+	memset(&slot->data, 0, sizeof(ReplicationSlotPersistentData));
+	namestrcpy(&slot->data.name, name);
+	slot->data.database = db_specific ? MyDatabaseId : InvalidOid;
+	slot->data.persistency = persistency;
+	slot->data.two_phase = two_phase;
+
+	/* and then data only present in shared memory */
+	slot->just_dirtied = false;
+	slot->dirty = false;
+	slot->effective_xmin = InvalidTransactionId;
+	slot->effective_catalog_xmin = InvalidTransactionId;
+	slot->candidate_catalog_xmin = InvalidTransactionId;
+	slot->candidate_xmin_lsn = InvalidXLogRecPtr;
+	slot->candidate_restart_valid = InvalidXLogRecPtr;
+	slot->candidate_restart_lsn = InvalidXLogRecPtr;
+
+	/*
+	 * Create the slot on disk.  We haven't actually marked the slot allocated
+	 * yet, so no special cleanup is required if this errors out.
+	 */
+	CreateSlotOnDisk(slot);
+
+	/*
+	 * We need to briefly prevent any other backend from iterating over the
+	 * slots while we flip the in_use flag. We also need to set the active
+	 * flag while holding the ControlLock as otherwise a concurrent
+	 * ReplicationSlotAcquire() could acquire the slot as well.
+	 */
+	LWLockAcquire(ReplicationSlotControlLock, LW_EXCLUSIVE);
+
+	slot->in_use = true;
+
+	/* We can now mark the slot active, and that makes it our slot. */
+	SpinLockAcquire(&slot->mutex);
+	Assert(slot->active_pid == 0);
+	slot->active_pid = MyProcPid;
+	SpinLockRelease(&slot->mutex);
+	MyReplicationSlot = slot;
+
+	LWLockRelease(ReplicationSlotControlLock);
+
+	/*
+	 * Create statistics entry for the new logical slot. We don't collect any
+	 * stats for physical slots, so no need to create an entry for the same.
+	 * See ReplicationSlotDropPtr for why we need to do this before releasing
+	 * ReplicationSlotAllocationLock.
+	 */
+	if (SlotIsLogical(slot))
+		pgstat_report_replslot_create(NameStr(slot->data.name));
+
+	/*
+	 * Now that the slot has been marked as in_use and active, it's safe to
+	 * let somebody else try to allocate a slot.
+	 */
+	LWLockRelease(ReplicationSlotAllocationLock);
+
+	/* Let everybody know we've modified this slot */
+	ConditionVariableBroadcast(&slot->active_cv);
+}
+
+/*
+ * Search for the named replication slot.
+ *
+ * Return the replication slot if found, otherwise NULL.
+ */
+ReplicationSlot *
+SearchNamedReplicationSlot(const char *name, bool need_lock)
+{
+	int			i;
+	ReplicationSlot *slot = NULL;
+
+	if (need_lock)
+		LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
+
+	for (i = 0; i < max_replication_slots; i++)
+	{
+		ReplicationSlot *s = &ReplicationSlotCtl->replication_slots[i];
+
+		if (s->in_use && strcmp(name, NameStr(s->data.name)) == 0)
+		{
+			slot = s;
+			break;
+		}
+	}
+
+	if (need_lock)
+		LWLockRelease(ReplicationSlotControlLock);
+
+	return slot;
+}
+
+/*
+ * Find a previously created slot and mark it as used by this process.
+ *
+ * An error is raised if nowait is true and the slot is currently in use. If
+ * nowait is false, we sleep until the slot is released by the owning process.
+ */
+void
+ReplicationSlotAcquire(const char *name, bool nowait)
+{
+	ReplicationSlot *s;
+	int			active_pid;
+
+	AssertArg(name != NULL);
+
+retry:
+	Assert(MyReplicationSlot == NULL);
+
+	LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
+
+	/*
+	 * Search for the slot with the specified name if the slot to acquire is
+	 * not given. If the slot is not found, we either return -1 or error out.
+	 */
+	s = SearchNamedReplicationSlot(name, false);
+	if (s == NULL || !s->in_use)
+	{
+		LWLockRelease(ReplicationSlotControlLock);
+
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("replication slot \"%s\" does not exist",
+						name)));
+	}
+
+	/*
+	 * This is the slot we want; check if it's active under some other
+	 * process.  In single user mode, we don't need this check.
+	 */
+	if (IsUnderPostmaster)
+	{
+		/*
+		 * Get ready to sleep on the slot in case it is active.  (We may end
+		 * up not sleeping, but we don't want to do this while holding the
+		 * spinlock.)
+		 */
+		if (!nowait)
+			ConditionVariablePrepareToSleep(&s->active_cv);
+
+		SpinLockAcquire(&s->mutex);
+		if (s->active_pid == 0)
+			s->active_pid = MyProcPid;
+		active_pid = s->active_pid;
+		SpinLockRelease(&s->mutex);
+	}
+	else
+		active_pid = MyProcPid;
+	LWLockRelease(ReplicationSlotControlLock);
+
+	/*
+	 * If we found the slot but it's already active in another process, we
+	 * wait until the owning process signals us that it's been released, or
+	 * error out.
+	 */
+	if (active_pid != MyProcPid)
+	{
+		if (!nowait)
+		{
+			/* Wait here until we get signaled, and then restart */
+			ConditionVariableSleep(&s->active_cv,
+								   WAIT_EVENT_REPLICATION_SLOT_DROP);
+			ConditionVariableCancelSleep();
+			goto retry;
+		}
+
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_IN_USE),
+				 errmsg("replication slot \"%s\" is active for PID %d",
+						NameStr(s->data.name), active_pid)));
+	}
+	else if (!nowait)
+		ConditionVariableCancelSleep(); /* no sleep needed after all */
+
+	/* Let everybody know we've modified this slot */
+	ConditionVariableBroadcast(&s->active_cv);
+
+	/* We made this slot active, so it's ours now. */
+	MyReplicationSlot = s;
+}
+
+/*
+ * Release the replication slot that this backend considers to own.
+ *
+ * This or another backend can re-acquire the slot later.
+ * Resources this slot requires will be preserved.
+ */
+void
+ReplicationSlotRelease(void)
+{
+	ReplicationSlot *slot = MyReplicationSlot;
+
+	Assert(slot != NULL && slot->active_pid != 0);
+
+	if (slot->data.persistency == RS_EPHEMERAL)
+	{
+		/*
+		 * Delete the slot. There is no !PANIC case where this is allowed to
+		 * fail, all that may happen is an incomplete cleanup of the on-disk
+		 * data.
+		 */
+		ReplicationSlotDropAcquired();
+	}
+
+	/*
+	 * If slot needed to temporarily restrain both data and catalog xmin to
+	 * create the catalog snapshot, remove that temporary constraint.
+	 * Snapshots can only be exported while the initial snapshot is still
+	 * acquired.
+	 */
+	if (!TransactionIdIsValid(slot->data.xmin) &&
+		TransactionIdIsValid(slot->effective_xmin))
+	{
+		SpinLockAcquire(&slot->mutex);
+		slot->effective_xmin = InvalidTransactionId;
+		SpinLockRelease(&slot->mutex);
+		ReplicationSlotsComputeRequiredXmin(false);
+	}
+
+	if (slot->data.persistency == RS_PERSISTENT)
+	{
+		/*
+		 * Mark persistent slot inactive.  We're not freeing it, just
+		 * disconnecting, but wake up others that may be waiting for it.
+		 */
+		SpinLockAcquire(&slot->mutex);
+		slot->active_pid = 0;
+		SpinLockRelease(&slot->mutex);
+		ConditionVariableBroadcast(&slot->active_cv);
+	}
+
+	MyReplicationSlot = NULL;
+
+	/* might not have been set when we've been a plain slot */
+	LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
+	MyProc->statusFlags &= ~PROC_IN_LOGICAL_DECODING;
+	ProcGlobal->statusFlags[MyProc->pgxactoff] = MyProc->statusFlags;
+	LWLockRelease(ProcArrayLock);
+}
+
+/*
+ * Cleanup all temporary slots created in current session.
+ */
+void
+ReplicationSlotCleanup(void)
+{
+	int			i;
+
+	Assert(MyReplicationSlot == NULL);
+
+restart:
+	LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
+	for (i = 0; i < max_replication_slots; i++)
+	{
+		ReplicationSlot *s = &ReplicationSlotCtl->replication_slots[i];
+
+		if (!s->in_use)
+			continue;
+
+		SpinLockAcquire(&s->mutex);
+		if (s->active_pid == MyProcPid)
+		{
+			Assert(s->data.persistency == RS_TEMPORARY);
+			SpinLockRelease(&s->mutex);
+			LWLockRelease(ReplicationSlotControlLock);	/* avoid deadlock */
+
+			ReplicationSlotDropPtr(s);
+
+			ConditionVariableBroadcast(&s->active_cv);
+			goto restart;
+		}
+		else
+			SpinLockRelease(&s->mutex);
+	}
+
+	LWLockRelease(ReplicationSlotControlLock);
+}
+
+/*
+ * Permanently drop replication slot identified by the passed in name.
+ */
+void
+ReplicationSlotDrop(const char *name, bool nowait)
+{
+	Assert(MyReplicationSlot == NULL);
+
+	ReplicationSlotAcquire(name, nowait);
+
+	ReplicationSlotDropAcquired();
+}
+
+/*
+ * Permanently drop the currently acquired replication slot.
+ */
+static void
+ReplicationSlotDropAcquired(void)
+{
+	ReplicationSlot *slot = MyReplicationSlot;
+
+	Assert(MyReplicationSlot != NULL);
+
+	/* slot isn't acquired anymore */
+	MyReplicationSlot = NULL;
+
+	ReplicationSlotDropPtr(slot);
+}
+
+/*
+ * Permanently drop the replication slot which will be released by the point
+ * this function returns.
+ */
+static void
+ReplicationSlotDropPtr(ReplicationSlot *slot)
+{
+	char		path[MAXPGPATH];
+	char		tmppath[MAXPGPATH];
+
+	/*
+	 * If some other backend ran this code concurrently with us, we might try
+	 * to delete a slot with a certain name while someone else was trying to
+	 * create a slot with the same name.
+	 */
+	LWLockAcquire(ReplicationSlotAllocationLock, LW_EXCLUSIVE);
+
+	/* Generate pathnames. */
+	sprintf(path, "pg_replslot/%s", NameStr(slot->data.name));
+	sprintf(tmppath, "pg_replslot/%s.tmp", NameStr(slot->data.name));
+
+	/*
+	 * Rename the slot directory on disk, so that we'll no longer recognize
+	 * this as a valid slot.  Note that if this fails, we've got to mark the
+	 * slot inactive before bailing out.  If we're dropping an ephemeral or a
+	 * temporary slot, we better never fail hard as the caller won't expect
+	 * the slot to survive and this might get called during error handling.
+	 */
+	if (rename(path, tmppath) == 0)
+	{
+		/*
+		 * We need to fsync() the directory we just renamed and its parent to
+		 * make sure that our changes are on disk in a crash-safe fashion.  If
+		 * fsync() fails, we can't be sure whether the changes are on disk or
+		 * not.  For now, we handle that by panicking;
+		 * StartupReplicationSlots() will try to straighten it out after
+		 * restart.
+		 */
+		START_CRIT_SECTION();
+		fsync_fname(tmppath, true);
+		fsync_fname("pg_replslot", true);
+		END_CRIT_SECTION();
+	}
+	else
+	{
+		bool		fail_softly = slot->data.persistency != RS_PERSISTENT;
+
+		SpinLockAcquire(&slot->mutex);
+		slot->active_pid = 0;
+		SpinLockRelease(&slot->mutex);
+
+		/* wake up anyone waiting on this slot */
+		ConditionVariableBroadcast(&slot->active_cv);
+
+		ereport(fail_softly ? WARNING : ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not rename file \"%s\" to \"%s\": %m",
+						path, tmppath)));
+	}
+
+	/*
+	 * The slot is definitely gone.  Lock out concurrent scans of the array
+	 * long enough to kill it.  It's OK to clear the active PID here without
+	 * grabbing the mutex because nobody else can be scanning the array here,
+	 * and nobody can be attached to this slot and thus access it without
+	 * scanning the array.
+	 *
+	 * Also wake up processes waiting for it.
+	 */
+	LWLockAcquire(ReplicationSlotControlLock, LW_EXCLUSIVE);
+	slot->active_pid = 0;
+	slot->in_use = false;
+	LWLockRelease(ReplicationSlotControlLock);
+	ConditionVariableBroadcast(&slot->active_cv);
+
+	/*
+	 * Slot is dead and doesn't prevent resource removal anymore, recompute
+	 * limits.
+	 */
+	ReplicationSlotsComputeRequiredXmin(false);
+	ReplicationSlotsComputeRequiredLSN();
+
+	/*
+	 * If removing the directory fails, the worst thing that will happen is
+	 * that the user won't be able to create a new slot with the same name
+	 * until the next server restart.  We warn about it, but that's all.
+	 */
+	if (!rmtree(tmppath, true))
+		ereport(WARNING,
+				(errmsg("could not remove directory \"%s\"", tmppath)));
+
+	/*
+	 * Send a message to drop the replication slot to the stats collector.
+	 * Since there is no guarantee of the order of message transfer on a UDP
+	 * connection, it's possible that a message for creating a new slot
+	 * reaches before a message for removing the old slot. We send the drop
+	 * and create messages while holding ReplicationSlotAllocationLock to
+	 * reduce that possibility. If the messages reached in reverse, we would
+	 * lose one statistics update message. But the next update message will
+	 * create the statistics for the replication slot.
+	 *
+	 * XXX In case, the messages for creation and drop slot of the same name
+	 * get lost and create happens before (auto)vacuum cleans up the dead
+	 * slot, the stats will be accumulated into the old slot. One can imagine
+	 * having OIDs for each slot to avoid the accumulation of stats but that
+	 * doesn't seem worth doing as in practice this won't happen frequently.
+	 */
+	if (SlotIsLogical(slot))
+		pgstat_report_replslot_drop(NameStr(slot->data.name));
+
+	/*
+	 * We release this at the very end, so that nobody starts trying to create
+	 * a slot while we're still cleaning up the detritus of the old one.
+	 */
+	LWLockRelease(ReplicationSlotAllocationLock);
+}
+
+/*
+ * Serialize the currently acquired slot's state from memory to disk, thereby
+ * guaranteeing the current state will survive a crash.
+ */
+void
+ReplicationSlotSave(void)
+{
+	char		path[MAXPGPATH];
+
+	Assert(MyReplicationSlot != NULL);
+
+	sprintf(path, "pg_replslot/%s", NameStr(MyReplicationSlot->data.name));
+	SaveSlotToPath(MyReplicationSlot, path, ERROR);
+}
+
+/*
+ * Signal that it would be useful if the currently acquired slot would be
+ * flushed out to disk.
+ *
+ * Note that the actual flush to disk can be delayed for a long time, if
+ * required for correctness explicitly do a ReplicationSlotSave().
+ */
+void
+ReplicationSlotMarkDirty(void)
+{
+	ReplicationSlot *slot = MyReplicationSlot;
+
+	Assert(MyReplicationSlot != NULL);
+
+	SpinLockAcquire(&slot->mutex);
+	MyReplicationSlot->just_dirtied = true;
+	MyReplicationSlot->dirty = true;
+	SpinLockRelease(&slot->mutex);
+}
+
+/*
+ * Convert a slot that's marked as RS_EPHEMERAL to a RS_PERSISTENT slot,
+ * guaranteeing it will be there after an eventual crash.
+ */
+void
+ReplicationSlotPersist(void)
+{
+	ReplicationSlot *slot = MyReplicationSlot;
+
+	Assert(slot != NULL);
+	Assert(slot->data.persistency != RS_PERSISTENT);
+
+	SpinLockAcquire(&slot->mutex);
+	slot->data.persistency = RS_PERSISTENT;
+	SpinLockRelease(&slot->mutex);
+
+	ReplicationSlotMarkDirty();
+	ReplicationSlotSave();
+}
+
+/*
+ * Compute the oldest xmin across all slots and store it in the ProcArray.
+ *
+ * If already_locked is true, ProcArrayLock has already been acquired
+ * exclusively.
+ */
+void
+ReplicationSlotsComputeRequiredXmin(bool already_locked)
+{
+	int			i;
+	TransactionId agg_xmin = InvalidTransactionId;
+	TransactionId agg_catalog_xmin = InvalidTransactionId;
+
+	Assert(ReplicationSlotCtl != NULL);
+
+	LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
+
+	for (i = 0; i < max_replication_slots; i++)
+	{
+		ReplicationSlot *s = &ReplicationSlotCtl->replication_slots[i];
+		TransactionId effective_xmin;
+		TransactionId effective_catalog_xmin;
+
+		if (!s->in_use)
+			continue;
+
+		SpinLockAcquire(&s->mutex);
+		effective_xmin = s->effective_xmin;
+		effective_catalog_xmin = s->effective_catalog_xmin;
+		SpinLockRelease(&s->mutex);
+
+		/* check the data xmin */
+		if (TransactionIdIsValid(effective_xmin) &&
+			(!TransactionIdIsValid(agg_xmin) ||
+			 TransactionIdPrecedes(effective_xmin, agg_xmin)))
+			agg_xmin = effective_xmin;
+
+		/* check the catalog xmin */
+		if (TransactionIdIsValid(effective_catalog_xmin) &&
+			(!TransactionIdIsValid(agg_catalog_xmin) ||
+			 TransactionIdPrecedes(effective_catalog_xmin, agg_catalog_xmin)))
+			agg_catalog_xmin = effective_catalog_xmin;
+	}
+
+	LWLockRelease(ReplicationSlotControlLock);
+
+	ProcArraySetReplicationSlotXmin(agg_xmin, agg_catalog_xmin, already_locked);
+}
+
+/*
+ * Compute the oldest restart LSN across all slots and inform xlog module.
+ *
+ * Note: while max_slot_wal_keep_size is theoretically relevant for this
+ * purpose, we don't try to account for that, because this module doesn't
+ * know what to compare against.
+ */
+void
+ReplicationSlotsComputeRequiredLSN(void)
+{
+	int			i;
+	XLogRecPtr	min_required = InvalidXLogRecPtr;
+
+	Assert(ReplicationSlotCtl != NULL);
+
+	LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
+	for (i = 0; i < max_replication_slots; i++)
+	{
+		ReplicationSlot *s = &ReplicationSlotCtl->replication_slots[i];
+		XLogRecPtr	restart_lsn;
+
+		if (!s->in_use)
+			continue;
+
+		SpinLockAcquire(&s->mutex);
+		restart_lsn = s->data.restart_lsn;
+		SpinLockRelease(&s->mutex);
+
+		if (restart_lsn != InvalidXLogRecPtr &&
+			(min_required == InvalidXLogRecPtr ||
+			 restart_lsn < min_required))
+			min_required = restart_lsn;
+	}
+	LWLockRelease(ReplicationSlotControlLock);
+
+	XLogSetReplicationSlotMinimumLSN(min_required);
+}
+
+/*
+ * Compute the oldest WAL LSN required by *logical* decoding slots..
+ *
+ * Returns InvalidXLogRecPtr if logical decoding is disabled or no logical
+ * slots exist.
+ *
+ * NB: this returns a value >= ReplicationSlotsComputeRequiredLSN(), since it
+ * ignores physical replication slots.
+ *
+ * The results aren't required frequently, so we don't maintain a precomputed
+ * value like we do for ComputeRequiredLSN() and ComputeRequiredXmin().
+ */
+XLogRecPtr
+ReplicationSlotsComputeLogicalRestartLSN(void)
+{
+	XLogRecPtr	result = InvalidXLogRecPtr;
+	int			i;
+
+	if (max_replication_slots <= 0)
+		return InvalidXLogRecPtr;
+
+	LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
+
+	for (i = 0; i < max_replication_slots; i++)
+	{
+		ReplicationSlot *s;
+		XLogRecPtr	restart_lsn;
+
+		s = &ReplicationSlotCtl->replication_slots[i];
+
+		/* cannot change while ReplicationSlotCtlLock is held */
+		if (!s->in_use)
+			continue;
+
+		/* we're only interested in logical slots */
+		if (!SlotIsLogical(s))
+			continue;
+
+		/* read once, it's ok if it increases while we're checking */
+		SpinLockAcquire(&s->mutex);
+		restart_lsn = s->data.restart_lsn;
+		SpinLockRelease(&s->mutex);
+
+		if (restart_lsn == InvalidXLogRecPtr)
+			continue;
+
+		if (result == InvalidXLogRecPtr ||
+			restart_lsn < result)
+			result = restart_lsn;
+	}
+
+	LWLockRelease(ReplicationSlotControlLock);
+
+	return result;
+}
+
+/*
+ * ReplicationSlotsCountDBSlots -- count the number of slots that refer to the
+ * passed database oid.
+ *
+ * Returns true if there are any slots referencing the database. *nslots will
+ * be set to the absolute number of slots in the database, *nactive to ones
+ * currently active.
+ */
+bool
+ReplicationSlotsCountDBSlots(Oid dboid, int *nslots, int *nactive)
+{
+	int			i;
+
+	*nslots = *nactive = 0;
+
+	if (max_replication_slots <= 0)
+		return false;
+
+	LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
+	for (i = 0; i < max_replication_slots; i++)
+	{
+		ReplicationSlot *s;
+
+		s = &ReplicationSlotCtl->replication_slots[i];
+
+		/* cannot change while ReplicationSlotCtlLock is held */
+		if (!s->in_use)
+			continue;
+
+		/* only logical slots are database specific, skip */
+		if (!SlotIsLogical(s))
+			continue;
+
+		/* not our database, skip */
+		if (s->data.database != dboid)
+			continue;
+
+		/* count slots with spinlock held */
+		SpinLockAcquire(&s->mutex);
+		(*nslots)++;
+		if (s->active_pid != 0)
+			(*nactive)++;
+		SpinLockRelease(&s->mutex);
+	}
+	LWLockRelease(ReplicationSlotControlLock);
+
+	if (*nslots > 0)
+		return true;
+	return false;
+}
+
+/*
+ * ReplicationSlotsDropDBSlots -- Drop all db-specific slots relating to the
+ * passed database oid. The caller should hold an exclusive lock on the
+ * pg_database oid for the database to prevent creation of new slots on the db
+ * or replay from existing slots.
+ *
+ * Another session that concurrently acquires an existing slot on the target DB
+ * (most likely to drop it) may cause this function to ERROR. If that happens
+ * it may have dropped some but not all slots.
+ *
+ * This routine isn't as efficient as it could be - but we don't drop
+ * databases often, especially databases with lots of slots.
+ */
+void
+ReplicationSlotsDropDBSlots(Oid dboid)
+{
+	int			i;
+
+	if (max_replication_slots <= 0)
+		return;
+
+restart:
+	LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
+	for (i = 0; i < max_replication_slots; i++)
+	{
+		ReplicationSlot *s;
+		char	   *slotname;
+		int			active_pid;
+
+		s = &ReplicationSlotCtl->replication_slots[i];
+
+		/* cannot change while ReplicationSlotCtlLock is held */
+		if (!s->in_use)
+			continue;
+
+		/* only logical slots are database specific, skip */
+		if (!SlotIsLogical(s))
+			continue;
+
+		/* not our database, skip */
+		if (s->data.database != dboid)
+			continue;
+
+		/* acquire slot, so ReplicationSlotDropAcquired can be reused  */
+		SpinLockAcquire(&s->mutex);
+		/* can't change while ReplicationSlotControlLock is held */
+		slotname = NameStr(s->data.name);
+		active_pid = s->active_pid;
+		if (active_pid == 0)
+		{
+			MyReplicationSlot = s;
+			s->active_pid = MyProcPid;
+		}
+		SpinLockRelease(&s->mutex);
+
+		/*
+		 * Even though we hold an exclusive lock on the database object a
+		 * logical slot for that DB can still be active, e.g. if it's
+		 * concurrently being dropped by a backend connected to another DB.
+		 *
+		 * That's fairly unlikely in practice, so we'll just bail out.
+		 */
+		if (active_pid)
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_IN_USE),
+					 errmsg("replication slot \"%s\" is active for PID %d",
+							slotname, active_pid)));
+
+		/*
+		 * To avoid duplicating ReplicationSlotDropAcquired() and to avoid
+		 * holding ReplicationSlotControlLock over filesystem operations,
+		 * release ReplicationSlotControlLock and use
+		 * ReplicationSlotDropAcquired.
+		 *
+		 * As that means the set of slots could change, restart scan from the
+		 * beginning each time we release the lock.
+		 */
+		LWLockRelease(ReplicationSlotControlLock);
+		ReplicationSlotDropAcquired();
+		goto restart;
+	}
+	LWLockRelease(ReplicationSlotControlLock);
+}
+
+
+/*
+ * Check whether the server's configuration supports using replication
+ * slots.
+ */
+void
+CheckSlotRequirements(void)
+{
+	/*
+	 * NB: Adding a new requirement likely means that RestoreSlotFromDisk()
+	 * needs the same check.
+	 */
+
+	if (max_replication_slots == 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("replication slots can only be used if max_replication_slots > 0")));
+
+	if (wal_level < WAL_LEVEL_REPLICA)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("replication slots can only be used if wal_level >= replica")));
+}
+
+/*
+ * Reserve WAL for the currently active slot.
+ *
+ * Compute and set restart_lsn in a manner that's appropriate for the type of
+ * the slot and concurrency safe.
+ */
+void
+ReplicationSlotReserveWal(void)
+{
+	ReplicationSlot *slot = MyReplicationSlot;
+
+	Assert(slot != NULL);
+	Assert(slot->data.restart_lsn == InvalidXLogRecPtr);
+
+	/*
+	 * The replication slot mechanism is used to prevent removal of required
+	 * WAL. As there is no interlock between this routine and checkpoints, WAL
+	 * segments could concurrently be removed when a now stale return value of
+	 * ReplicationSlotsComputeRequiredLSN() is used. In the unlikely case that
+	 * this happens we'll just retry.
+	 */
+	while (true)
+	{
+		XLogSegNo	segno;
+		XLogRecPtr	restart_lsn;
+
+		/*
+		 * For logical slots log a standby snapshot and start logical decoding
+		 * at exactly that position. That allows the slot to start up more
+		 * quickly.
+		 *
+		 * That's not needed (or indeed helpful) for physical slots as they'll
+		 * start replay at the last logged checkpoint anyway. Instead return
+		 * the location of the last redo LSN. While that slightly increases
+		 * the chance that we have to retry, it's where a base backup has to
+		 * start replay at.
+		 */
+		if (!RecoveryInProgress() && SlotIsLogical(slot))
+		{
+			XLogRecPtr	flushptr;
+
+			/* start at current insert position */
+			restart_lsn = GetXLogInsertRecPtr();
+			SpinLockAcquire(&slot->mutex);
+			slot->data.restart_lsn = restart_lsn;
+			SpinLockRelease(&slot->mutex);
+
+			/* make sure we have enough information to start */
+			flushptr = LogStandbySnapshot();
+
+			/* and make sure it's fsynced to disk */
+			XLogFlush(flushptr);
+		}
+		else
+		{
+			restart_lsn = GetRedoRecPtr();
+			SpinLockAcquire(&slot->mutex);
+			slot->data.restart_lsn = restart_lsn;
+			SpinLockRelease(&slot->mutex);
+		}
+
+		/* prevent WAL removal as fast as possible */
+		ReplicationSlotsComputeRequiredLSN();
+
+		/*
+		 * If all required WAL is still there, great, otherwise retry. The
+		 * slot should prevent further removal of WAL, unless there's a
+		 * concurrent ReplicationSlotsComputeRequiredLSN() after we've written
+		 * the new restart_lsn above, so normally we should never need to loop
+		 * more than twice.
+		 */
+		XLByteToSeg(slot->data.restart_lsn, segno, wal_segment_size);
+		if (XLogGetLastRemovedSegno() < segno)
+			break;
+	}
+}
+
+/*
+ * Helper for InvalidateObsoleteReplicationSlots -- acquires the given slot
+ * and mark it invalid, if necessary and possible.
+ *
+ * Returns whether ReplicationSlotControlLock was released in the interim (and
+ * in that case we're not holding the lock at return, otherwise we are).
+ *
+ * Sets *invalidated true if the slot was invalidated. (Untouched otherwise.)
+ *
+ * This is inherently racy, because we release the LWLock
+ * for syscalls, so caller must restart if we return true.
+ */
+static bool
+InvalidatePossiblyObsoleteSlot(ReplicationSlot *s, XLogRecPtr oldestLSN,
+							   bool *invalidated)
+{
+	int			last_signaled_pid = 0;
+	bool		released_lock = false;
+
+	for (;;)
+	{
+		XLogRecPtr	restart_lsn;
+		NameData	slotname;
+		int			active_pid = 0;
+
+		Assert(LWLockHeldByMeInMode(ReplicationSlotControlLock, LW_SHARED));
+
+		if (!s->in_use)
+		{
+			if (released_lock)
+				LWLockRelease(ReplicationSlotControlLock);
+			break;
+		}
+
+		/*
+		 * Check if the slot needs to be invalidated. If it needs to be
+		 * invalidated, and is not currently acquired, acquire it and mark it
+		 * as having been invalidated.  We do this with the spinlock held to
+		 * avoid race conditions -- for example the restart_lsn could move
+		 * forward, or the slot could be dropped.
+		 */
+		SpinLockAcquire(&s->mutex);
+
+		restart_lsn = s->data.restart_lsn;
+
+		/*
+		 * If the slot is already invalid or is fresh enough, we don't need to
+		 * do anything.
+		 */
+		if (XLogRecPtrIsInvalid(restart_lsn) || restart_lsn >= oldestLSN)
+		{
+			SpinLockRelease(&s->mutex);
+			if (released_lock)
+				LWLockRelease(ReplicationSlotControlLock);
+			break;
+		}
+
+		slotname = s->data.name;
+		active_pid = s->active_pid;
+
+		/*
+		 * If the slot can be acquired, do so and mark it invalidated
+		 * immediately.  Otherwise we'll signal the owning process, below, and
+		 * retry.
+		 */
+		if (active_pid == 0)
+		{
+			MyReplicationSlot = s;
+			s->active_pid = MyProcPid;
+			s->data.invalidated_at = restart_lsn;
+			s->data.restart_lsn = InvalidXLogRecPtr;
+
+			/* Let caller know */
+			*invalidated = true;
+		}
+
+		SpinLockRelease(&s->mutex);
+
+		if (active_pid != 0)
+		{
+			/*
+			 * Prepare the sleep on the slot's condition variable before
+			 * releasing the lock, to close a possible race condition if the
+			 * slot is released before the sleep below.
+			 */
+			ConditionVariablePrepareToSleep(&s->active_cv);
+
+			LWLockRelease(ReplicationSlotControlLock);
+			released_lock = true;
+
+			/*
+			 * Signal to terminate the process that owns the slot, if we
+			 * haven't already signalled it.  (Avoidance of repeated
+			 * signalling is the only reason for there to be a loop in this
+			 * routine; otherwise we could rely on caller's restart loop.)
+			 *
+			 * There is the race condition that other process may own the slot
+			 * after its current owner process is terminated and before this
+			 * process owns it. To handle that, we signal only if the PID of
+			 * the owning process has changed from the previous time. (This
+			 * logic assumes that the same PID is not reused very quickly.)
+			 */
+			if (last_signaled_pid != active_pid)
+			{
+				ereport(LOG,
+						(errmsg("terminating process %d to release replication slot \"%s\"",
+								active_pid, NameStr(slotname))));
+
+				(void) kill(active_pid, SIGTERM);
+				last_signaled_pid = active_pid;
+			}
+
+			/* Wait until the slot is released. */
+			ConditionVariableSleep(&s->active_cv,
+								   WAIT_EVENT_REPLICATION_SLOT_DROP);
+
+			/*
+			 * Re-acquire lock and start over; we expect to invalidate the
+			 * slot next time (unless another process acquires the slot in the
+			 * meantime).
+			 */
+			LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
+			continue;
+		}
+		else
+		{
+			/*
+			 * We hold the slot now and have already invalidated it; flush it
+			 * to ensure that state persists.
+			 *
+			 * Don't want to hold ReplicationSlotControlLock across file
+			 * system operations, so release it now but be sure to tell caller
+			 * to restart from scratch.
+			 */
+			LWLockRelease(ReplicationSlotControlLock);
+			released_lock = true;
+
+			/* Make sure the invalidated state persists across server restart */
+			ReplicationSlotMarkDirty();
+			ReplicationSlotSave();
+			ReplicationSlotRelease();
+
+			ereport(LOG,
+					(errmsg("invalidating slot \"%s\" because its restart_lsn %X/%X exceeds max_slot_wal_keep_size",
+							NameStr(slotname),
+							LSN_FORMAT_ARGS(restart_lsn))));
+
+			/* done with this slot for now */
+			break;
+		}
+	}
+
+	Assert(released_lock == !LWLockHeldByMe(ReplicationSlotControlLock));
+
+	return released_lock;
+}
+
+/*
+ * Mark any slot that points to an LSN older than the given segment
+ * as invalid; it requires WAL that's about to be removed.
+ *
+ * Returns true when any slot have got invalidated.
+ *
+ * NB - this runs as part of checkpoint, so avoid raising errors if possible.
+ */
+bool
+InvalidateObsoleteReplicationSlots(XLogSegNo oldestSegno)
+{
+	XLogRecPtr	oldestLSN;
+	bool		invalidated = false;
+
+	XLogSegNoOffsetToRecPtr(oldestSegno, 0, wal_segment_size, oldestLSN);
+
+restart:
+	LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
+	for (int i = 0; i < max_replication_slots; i++)
+	{
+		ReplicationSlot *s = &ReplicationSlotCtl->replication_slots[i];
+
+		if (!s->in_use)
+			continue;
+
+		if (InvalidatePossiblyObsoleteSlot(s, oldestLSN, &invalidated))
+		{
+			/* if the lock was released, start from scratch */
+			goto restart;
+		}
+	}
+	LWLockRelease(ReplicationSlotControlLock);
+
+	/*
+	 * If any slots have been invalidated, recalculate the resource limits.
+	 */
+	if (invalidated)
+	{
+		ReplicationSlotsComputeRequiredXmin(false);
+		ReplicationSlotsComputeRequiredLSN();
+	}
+
+	return invalidated;
+}
+
+/*
+ * Flush all replication slots to disk.
+ *
+ * This needn't actually be part of a checkpoint, but it's a convenient
+ * location.
+ */
+void
+CheckPointReplicationSlots(void)
+{
+	int			i;
+
+	elog(DEBUG1, "performing replication slot checkpoint");
+
+	/*
+	 * Prevent any slot from being created/dropped while we're active. As we
+	 * explicitly do *not* want to block iterating over replication_slots or
+	 * acquiring a slot we cannot take the control lock - but that's OK,
+	 * because holding ReplicationSlotAllocationLock is strictly stronger, and
+	 * enough to guarantee that nobody can change the in_use bits on us.
+	 */
+	LWLockAcquire(ReplicationSlotAllocationLock, LW_SHARED);
+
+	for (i = 0; i < max_replication_slots; i++)
+	{
+		ReplicationSlot *s = &ReplicationSlotCtl->replication_slots[i];
+		char		path[MAXPGPATH];
+
+		if (!s->in_use)
+			continue;
+
+		/* save the slot to disk, locking is handled in SaveSlotToPath() */
+		sprintf(path, "pg_replslot/%s", NameStr(s->data.name));
+		SaveSlotToPath(s, path, LOG);
+	}
+	LWLockRelease(ReplicationSlotAllocationLock);
+}
+
+/*
+ * Load all replication slots from disk into memory at server startup. This
+ * needs to be run before we start crash recovery.
+ */
+void
+StartupReplicationSlots(void)
+{
+	DIR		   *replication_dir;
+	struct dirent *replication_de;
+
+	elog(DEBUG1, "starting up replication slots");
+
+	/* restore all slots by iterating over all on-disk entries */
+	replication_dir = AllocateDir("pg_replslot");
+	while ((replication_de = ReadDir(replication_dir, "pg_replslot")) != NULL)
+	{
+		struct stat statbuf;
+		char		path[MAXPGPATH + 12];
+
+		if (strcmp(replication_de->d_name, ".") == 0 ||
+			strcmp(replication_de->d_name, "..") == 0)
+			continue;
+
+		snprintf(path, sizeof(path), "pg_replslot/%s", replication_de->d_name);
+
+		/* we're only creating directories here, skip if it's not our's */
+		if (lstat(path, &statbuf) == 0 && !S_ISDIR(statbuf.st_mode))
+			continue;
+
+		/* we crashed while a slot was being setup or deleted, clean up */
+		if (pg_str_endswith(replication_de->d_name, ".tmp"))
+		{
+			if (!rmtree(path, true))
+			{
+				ereport(WARNING,
+						(errmsg("could not remove directory \"%s\"",
+								path)));
+				continue;
+			}
+			fsync_fname("pg_replslot", true);
+			continue;
+		}
+
+		/* looks like a slot in a normal state, restore */
+		RestoreSlotFromDisk(replication_de->d_name);
+	}
+	FreeDir(replication_dir);
+
+	/* currently no slots exist, we're done. */
+	if (max_replication_slots <= 0)
+		return;
+
+	/* Now that we have recovered all the data, compute replication xmin */
+	ReplicationSlotsComputeRequiredXmin(false);
+	ReplicationSlotsComputeRequiredLSN();
+}
+
+/* ----
+ * Manipulation of on-disk state of replication slots
+ *
+ * NB: none of the routines below should take any notice whether a slot is the
+ * current one or not, that's all handled a layer above.
+ * ----
+ */
+static void
+CreateSlotOnDisk(ReplicationSlot *slot)
+{
+	char		tmppath[MAXPGPATH];
+	char		path[MAXPGPATH];
+	struct stat st;
+
+	/*
+	 * No need to take out the io_in_progress_lock, nobody else can see this
+	 * slot yet, so nobody else will write. We're reusing SaveSlotToPath which
+	 * takes out the lock, if we'd take the lock here, we'd deadlock.
+	 */
+
+	sprintf(path, "pg_replslot/%s", NameStr(slot->data.name));
+	sprintf(tmppath, "pg_replslot/%s.tmp", NameStr(slot->data.name));
+
+	/*
+	 * It's just barely possible that some previous effort to create or drop a
+	 * slot with this name left a temp directory lying around. If that seems
+	 * to be the case, try to remove it.  If the rmtree() fails, we'll error
+	 * out at the MakePGDirectory() below, so we don't bother checking
+	 * success.
+	 */
+	if (stat(tmppath, &st) == 0 && S_ISDIR(st.st_mode))
+		rmtree(tmppath, true);
+
+	/* Create and fsync the temporary slot directory. */
+	if (MakePGDirectory(tmppath) < 0)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not create directory \"%s\": %m",
+						tmppath)));
+	fsync_fname(tmppath, true);
+
+	/* Write the actual state file. */
+	slot->dirty = true;			/* signal that we really need to write */
+	SaveSlotToPath(slot, tmppath, ERROR);
+
+	/* Rename the directory into place. */
+	if (rename(tmppath, path) != 0)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not rename file \"%s\" to \"%s\": %m",
+						tmppath, path)));
+
+	/*
+	 * If we'd now fail - really unlikely - we wouldn't know whether this slot
+	 * would persist after an OS crash or not - so, force a restart. The
+	 * restart would try to fsync this again till it works.
+	 */
+	START_CRIT_SECTION();
+
+	fsync_fname(path, true);
+	fsync_fname("pg_replslot", true);
+
+	END_CRIT_SECTION();
+}
+
+/*
+ * Shared functionality between saving and creating a replication slot.
+ */
+static void
+SaveSlotToPath(ReplicationSlot *slot, const char *dir, int elevel)
+{
+	char		tmppath[MAXPGPATH];
+	char		path[MAXPGPATH];
+	int			fd;
+	ReplicationSlotOnDisk cp;
+	bool		was_dirty;
+
+	/* first check whether there's something to write out */
+	SpinLockAcquire(&slot->mutex);
+	was_dirty = slot->dirty;
+	slot->just_dirtied = false;
+	SpinLockRelease(&slot->mutex);
+
+	/* and don't do anything if there's nothing to write */
+	if (!was_dirty)
+		return;
+
+	LWLockAcquire(&slot->io_in_progress_lock, LW_EXCLUSIVE);
+
+	/* silence valgrind :( */
+	memset(&cp, 0, sizeof(ReplicationSlotOnDisk));
+
+	sprintf(tmppath, "%s/state.tmp", dir);
+	sprintf(path, "%s/state", dir);
+
+	fd = OpenTransientFile(tmppath, O_CREAT | O_EXCL | O_WRONLY | PG_BINARY);
+	if (fd < 0)
+	{
+		/*
+		 * If not an ERROR, then release the lock before returning.  In case
+		 * of an ERROR, the error recovery path automatically releases the
+		 * lock, but no harm in explicitly releasing even in that case.  Note
+		 * that LWLockRelease() could affect errno.
+		 */
+		int			save_errno = errno;
+
+		LWLockRelease(&slot->io_in_progress_lock);
+		errno = save_errno;
+		ereport(elevel,
+				(errcode_for_file_access(),
+				 errmsg("could not create file \"%s\": %m",
+						tmppath)));
+		return;
+	}
+
+	cp.magic = SLOT_MAGIC;
+	INIT_CRC32C(cp.checksum);
+	cp.version = SLOT_VERSION;
+	cp.length = ReplicationSlotOnDiskV2Size;
+
+	SpinLockAcquire(&slot->mutex);
+
+	memcpy(&cp.slotdata, &slot->data, sizeof(ReplicationSlotPersistentData));
+
+	SpinLockRelease(&slot->mutex);
+
+	COMP_CRC32C(cp.checksum,
+				(char *) (&cp) + SnapBuildOnDiskNotChecksummedSize,
+				SnapBuildOnDiskChecksummedSize);
+	FIN_CRC32C(cp.checksum);
+
+	errno = 0;
+	pgstat_report_wait_start(WAIT_EVENT_REPLICATION_SLOT_WRITE);
+	if ((write(fd, &cp, sizeof(cp))) != sizeof(cp))
+	{
+		int			save_errno = errno;
+
+		pgstat_report_wait_end();
+		CloseTransientFile(fd);
+		LWLockRelease(&slot->io_in_progress_lock);
+
+		/* if write didn't set errno, assume problem is no disk space */
+		errno = save_errno ? save_errno : ENOSPC;
+		ereport(elevel,
+				(errcode_for_file_access(),
+				 errmsg("could not write to file \"%s\": %m",
+						tmppath)));
+		return;
+	}
+	pgstat_report_wait_end();
+
+	/* fsync the temporary file */
+	pgstat_report_wait_start(WAIT_EVENT_REPLICATION_SLOT_SYNC);
+	if (pg_fsync(fd) != 0)
+	{
+		int			save_errno = errno;
+
+		pgstat_report_wait_end();
+		CloseTransientFile(fd);
+		LWLockRelease(&slot->io_in_progress_lock);
+		errno = save_errno;
+		ereport(elevel,
+				(errcode_for_file_access(),
+				 errmsg("could not fsync file \"%s\": %m",
+						tmppath)));
+		return;
+	}
+	pgstat_report_wait_end();
+
+	if (CloseTransientFile(fd) != 0)
+	{
+		int			save_errno = errno;
+
+		LWLockRelease(&slot->io_in_progress_lock);
+		errno = save_errno;
+		ereport(elevel,
+				(errcode_for_file_access(),
+				 errmsg("could not close file \"%s\": %m",
+						tmppath)));
+		return;
+	}
+
+	/* rename to permanent file, fsync file and directory */
+	if (rename(tmppath, path) != 0)
+	{
+		int			save_errno = errno;
+
+		LWLockRelease(&slot->io_in_progress_lock);
+		errno = save_errno;
+		ereport(elevel,
+				(errcode_for_file_access(),
+				 errmsg("could not rename file \"%s\" to \"%s\": %m",
+						tmppath, path)));
+		return;
+	}
+
+	/*
+	 * Check CreateSlotOnDisk() for the reasoning of using a critical section.
+	 */
+	START_CRIT_SECTION();
+
+	fsync_fname(path, false);
+	fsync_fname(dir, true);
+	fsync_fname("pg_replslot", true);
+
+	END_CRIT_SECTION();
+
+	/*
+	 * Successfully wrote, unset dirty bit, unless somebody dirtied again
+	 * already.
+	 */
+	SpinLockAcquire(&slot->mutex);
+	if (!slot->just_dirtied)
+		slot->dirty = false;
+	SpinLockRelease(&slot->mutex);
+
+	LWLockRelease(&slot->io_in_progress_lock);
+}
+
+/*
+ * Load a single slot from disk into memory.
+ */
+static void
+RestoreSlotFromDisk(const char *name)
+{
+	ReplicationSlotOnDisk cp;
+	int			i;
+	char		slotdir[MAXPGPATH + 12];
+	char		path[MAXPGPATH + 22];
+	int			fd;
+	bool		restored = false;
+	int			readBytes;
+	pg_crc32c	checksum;
+
+	/* no need to lock here, no concurrent access allowed yet */
+
+	/* delete temp file if it exists */
+	sprintf(slotdir, "pg_replslot/%s", name);
+	sprintf(path, "%s/state.tmp", slotdir);
+	if (unlink(path) < 0 && errno != ENOENT)
+		ereport(PANIC,
+				(errcode_for_file_access(),
+				 errmsg("could not remove file \"%s\": %m", path)));
+
+	sprintf(path, "%s/state", slotdir);
+
+	elog(DEBUG1, "restoring replication slot from \"%s\"", path);
+
+	/* on some operating systems fsyncing a file requires O_RDWR */
+	fd = OpenTransientFile(path, O_RDWR | PG_BINARY);
+
+	/*
+	 * We do not need to handle this as we are rename()ing the directory into
+	 * place only after we fsync()ed the state file.
+	 */
+	if (fd < 0)
+		ereport(PANIC,
+				(errcode_for_file_access(),
+				 errmsg("could not open file \"%s\": %m", path)));
+
+	/*
+	 * Sync state file before we're reading from it. We might have crashed
+	 * while it wasn't synced yet and we shouldn't continue on that basis.
+	 */
+	pgstat_report_wait_start(WAIT_EVENT_REPLICATION_SLOT_RESTORE_SYNC);
+	if (pg_fsync(fd) != 0)
+		ereport(PANIC,
+				(errcode_for_file_access(),
+				 errmsg("could not fsync file \"%s\": %m",
+						path)));
+	pgstat_report_wait_end();
+
+	/* Also sync the parent directory */
+	START_CRIT_SECTION();
+	fsync_fname(slotdir, true);
+	END_CRIT_SECTION();
+
+	/* read part of statefile that's guaranteed to be version independent */
+	pgstat_report_wait_start(WAIT_EVENT_REPLICATION_SLOT_READ);
+	readBytes = read(fd, &cp, ReplicationSlotOnDiskConstantSize);
+	pgstat_report_wait_end();
+	if (readBytes != ReplicationSlotOnDiskConstantSize)
+	{
+		if (readBytes < 0)
+			ereport(PANIC,
+					(errcode_for_file_access(),
+					 errmsg("could not read file \"%s\": %m", path)));
+		else
+			ereport(PANIC,
+					(errcode(ERRCODE_DATA_CORRUPTED),
+					 errmsg("could not read file \"%s\": read %d of %zu",
+							path, readBytes,
+							(Size) ReplicationSlotOnDiskConstantSize)));
+	}
+
+	/* verify magic */
+	if (cp.magic != SLOT_MAGIC)
+		ereport(PANIC,
+				(errcode(ERRCODE_DATA_CORRUPTED),
+				 errmsg("replication slot file \"%s\" has wrong magic number: %u instead of %u",
+						path, cp.magic, SLOT_MAGIC)));
+
+	/* verify version */
+	if (cp.version != SLOT_VERSION)
+		ereport(PANIC,
+				(errcode(ERRCODE_DATA_CORRUPTED),
+				 errmsg("replication slot file \"%s\" has unsupported version %u",
+						path, cp.version)));
+
+	/* boundary check on length */
+	if (cp.length != ReplicationSlotOnDiskV2Size)
+		ereport(PANIC,
+				(errcode(ERRCODE_DATA_CORRUPTED),
+				 errmsg("replication slot file \"%s\" has corrupted length %u",
+						path, cp.length)));
+
+	/* Now that we know the size, read the entire file */
+	pgstat_report_wait_start(WAIT_EVENT_REPLICATION_SLOT_READ);
+	readBytes = read(fd,
+					 (char *) &cp + ReplicationSlotOnDiskConstantSize,
+					 cp.length);
+	pgstat_report_wait_end();
+	if (readBytes != cp.length)
+	{
+		if (readBytes < 0)
+			ereport(PANIC,
+					(errcode_for_file_access(),
+					 errmsg("could not read file \"%s\": %m", path)));
+		else
+			ereport(PANIC,
+					(errcode(ERRCODE_DATA_CORRUPTED),
+					 errmsg("could not read file \"%s\": read %d of %zu",
+							path, readBytes, (Size) cp.length)));
+	}
+
+	if (CloseTransientFile(fd) != 0)
+		ereport(PANIC,
+				(errcode_for_file_access(),
+				 errmsg("could not close file \"%s\": %m", path)));
+
+	/* now verify the CRC */
+	INIT_CRC32C(checksum);
+	COMP_CRC32C(checksum,
+				(char *) &cp + SnapBuildOnDiskNotChecksummedSize,
+				SnapBuildOnDiskChecksummedSize);
+	FIN_CRC32C(checksum);
+
+	if (!EQ_CRC32C(checksum, cp.checksum))
+		ereport(PANIC,
+				(errmsg("checksum mismatch for replication slot file \"%s\": is %u, should be %u",
+						path, checksum, cp.checksum)));
+
+	/*
+	 * If we crashed with an ephemeral slot active, don't restore but delete
+	 * it.
+	 */
+	if (cp.slotdata.persistency != RS_PERSISTENT)
+	{
+		if (!rmtree(slotdir, true))
+		{
+			ereport(WARNING,
+					(errmsg("could not remove directory \"%s\"",
+							slotdir)));
+		}
+		fsync_fname("pg_replslot", true);
+		return;
+	}
+
+	/*
+	 * Verify that requirements for the specific slot type are met. That's
+	 * important because if these aren't met we're not guaranteed to retain
+	 * all the necessary resources for the slot.
+	 *
+	 * NB: We have to do so *after* the above checks for ephemeral slots,
+	 * because otherwise a slot that shouldn't exist anymore could prevent
+	 * restarts.
+	 *
+	 * NB: Changing the requirements here also requires adapting
+	 * CheckSlotRequirements() and CheckLogicalDecodingRequirements().
+	 */
+	if (cp.slotdata.database != InvalidOid && wal_level < WAL_LEVEL_LOGICAL)
+		ereport(FATAL,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("logical replication slot \"%s\" exists, but wal_level < logical",
+						NameStr(cp.slotdata.name)),
+				 errhint("Change wal_level to be logical or higher.")));
+	else if (wal_level < WAL_LEVEL_REPLICA)
+		ereport(FATAL,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("physical replication slot \"%s\" exists, but wal_level < replica",
+						NameStr(cp.slotdata.name)),
+				 errhint("Change wal_level to be replica or higher.")));
+
+	/* nothing can be active yet, don't lock anything */
+	for (i = 0; i < max_replication_slots; i++)
+	{
+		ReplicationSlot *slot;
+
+		slot = &ReplicationSlotCtl->replication_slots[i];
+
+		if (slot->in_use)
+			continue;
+
+		/* restore the entire set of persistent data */
+		memcpy(&slot->data, &cp.slotdata,
+			   sizeof(ReplicationSlotPersistentData));
+
+		/* initialize in memory state */
+		slot->effective_xmin = cp.slotdata.xmin;
+		slot->effective_catalog_xmin = cp.slotdata.catalog_xmin;
+
+		slot->candidate_catalog_xmin = InvalidTransactionId;
+		slot->candidate_xmin_lsn = InvalidXLogRecPtr;
+		slot->candidate_restart_lsn = InvalidXLogRecPtr;
+		slot->candidate_restart_valid = InvalidXLogRecPtr;
+
+		slot->in_use = true;
+		slot->active_pid = 0;
+
+		restored = true;
+		break;
+	}
+
+	if (!restored)
+		ereport(FATAL,
+				(errmsg("too many replication slots active before shutdown"),
+				 errhint("Increase max_replication_slots and try again.")));
+}
diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
new file mode 100644
index 0000000..31e74d3
--- /dev/null
+++ b/src/backend/replication/slotfuncs.c
@@ -0,0 +1,950 @@
+/*-------------------------------------------------------------------------
+ *
+ * slotfuncs.c
+ *	   Support functions for replication slots
+ *
+ * Copyright (c) 2012-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/slotfuncs.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/htup_details.h"
+#include "access/xlog_internal.h"
+#include "access/xlogutils.h"
+#include "funcapi.h"
+#include "miscadmin.h"
+#include "replication/decode.h"
+#include "replication/logical.h"
+#include "replication/slot.h"
+#include "utils/builtins.h"
+#include "utils/inval.h"
+#include "utils/pg_lsn.h"
+#include "utils/resowner.h"
+
+static void
+check_permissions(void)
+{
+	if (!superuser() && !has_rolreplication(GetUserId()))
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("must be superuser or replication role to use replication slots")));
+}
+
+/*
+ * Helper function for creating a new physical replication slot with
+ * given arguments. Note that this function doesn't release the created
+ * slot.
+ *
+ * If restart_lsn is a valid value, we use it without WAL reservation
+ * routine. So the caller must guarantee that WAL is available.
+ */
+static void
+create_physical_replication_slot(char *name, bool immediately_reserve,
+								 bool temporary, XLogRecPtr restart_lsn)
+{
+	Assert(!MyReplicationSlot);
+
+	/* acquire replication slot, this will check for conflicting names */
+	ReplicationSlotCreate(name, false,
+						  temporary ? RS_TEMPORARY : RS_PERSISTENT, false);
+
+	if (immediately_reserve)
+	{
+		/* Reserve WAL as the user asked for it */
+		if (XLogRecPtrIsInvalid(restart_lsn))
+			ReplicationSlotReserveWal();
+		else
+			MyReplicationSlot->data.restart_lsn = restart_lsn;
+
+		/* Write this slot to disk */
+		ReplicationSlotMarkDirty();
+		ReplicationSlotSave();
+	}
+}
+
+/*
+ * SQL function for creating a new physical (streaming replication)
+ * replication slot.
+ */
+Datum
+pg_create_physical_replication_slot(PG_FUNCTION_ARGS)
+{
+	Name		name = PG_GETARG_NAME(0);
+	bool		immediately_reserve = PG_GETARG_BOOL(1);
+	bool		temporary = PG_GETARG_BOOL(2);
+	Datum		values[2];
+	bool		nulls[2];
+	TupleDesc	tupdesc;
+	HeapTuple	tuple;
+	Datum		result;
+
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+		elog(ERROR, "return type must be a row type");
+
+	check_permissions();
+
+	CheckSlotRequirements();
+
+	create_physical_replication_slot(NameStr(*name),
+									 immediately_reserve,
+									 temporary,
+									 InvalidXLogRecPtr);
+
+	values[0] = NameGetDatum(&MyReplicationSlot->data.name);
+	nulls[0] = false;
+
+	if (immediately_reserve)
+	{
+		values[1] = LSNGetDatum(MyReplicationSlot->data.restart_lsn);
+		nulls[1] = false;
+	}
+	else
+		nulls[1] = true;
+
+	tuple = heap_form_tuple(tupdesc, values, nulls);
+	result = HeapTupleGetDatum(tuple);
+
+	ReplicationSlotRelease();
+
+	PG_RETURN_DATUM(result);
+}
+
+
+/*
+ * Helper function for creating a new logical replication slot with
+ * given arguments. Note that this function doesn't release the created
+ * slot.
+ *
+ * When find_startpoint is false, the slot's confirmed_flush is not set; it's
+ * caller's responsibility to ensure it's set to something sensible.
+ */
+static void
+create_logical_replication_slot(char *name, char *plugin,
+								bool temporary, bool two_phase,
+								XLogRecPtr restart_lsn,
+								bool find_startpoint)
+{
+	LogicalDecodingContext *ctx = NULL;
+
+	Assert(!MyReplicationSlot);
+
+	/*
+	 * Acquire a logical decoding slot, this will check for conflicting names.
+	 * Initially create persistent slot as ephemeral - that allows us to
+	 * nicely handle errors during initialization because it'll get dropped if
+	 * this transaction fails. We'll make it persistent at the end. Temporary
+	 * slots can be created as temporary from beginning as they get dropped on
+	 * error as well.
+	 */
+	ReplicationSlotCreate(name, true,
+						  temporary ? RS_TEMPORARY : RS_EPHEMERAL, two_phase);
+
+	/*
+	 * Create logical decoding context to find start point or, if we don't
+	 * need it, to 1) bump slot's restart_lsn and xmin 2) check plugin sanity.
+	 *
+	 * Note: when !find_startpoint this is still important, because it's at
+	 * this point that the output plugin is validated.
+	 */
+	ctx = CreateInitDecodingContext(plugin, NIL,
+									false,	/* just catalogs is OK */
+									restart_lsn,
+									XL_ROUTINE(.page_read = read_local_xlog_page,
+											   .segment_open = wal_segment_open,
+											   .segment_close = wal_segment_close),
+									NULL, NULL, NULL);
+
+	/*
+	 * If caller needs us to determine the decoding start point, do so now.
+	 * This might take a while.
+	 */
+	if (find_startpoint)
+		DecodingContextFindStartpoint(ctx);
+
+	/* don't need the decoding context anymore */
+	FreeDecodingContext(ctx);
+}
+
+/*
+ * SQL function for creating a new logical replication slot.
+ */
+Datum
+pg_create_logical_replication_slot(PG_FUNCTION_ARGS)
+{
+	Name		name = PG_GETARG_NAME(0);
+	Name		plugin = PG_GETARG_NAME(1);
+	bool		temporary = PG_GETARG_BOOL(2);
+	bool		two_phase = PG_GETARG_BOOL(3);
+	Datum		result;
+	TupleDesc	tupdesc;
+	HeapTuple	tuple;
+	Datum		values[2];
+	bool		nulls[2];
+
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+		elog(ERROR, "return type must be a row type");
+
+	check_permissions();
+
+	CheckLogicalDecodingRequirements();
+
+	create_logical_replication_slot(NameStr(*name),
+									NameStr(*plugin),
+									temporary,
+									two_phase,
+									InvalidXLogRecPtr,
+									true);
+
+	values[0] = NameGetDatum(&MyReplicationSlot->data.name);
+	values[1] = LSNGetDatum(MyReplicationSlot->data.confirmed_flush);
+
+	memset(nulls, 0, sizeof(nulls));
+
+	tuple = heap_form_tuple(tupdesc, values, nulls);
+	result = HeapTupleGetDatum(tuple);
+
+	/* ok, slot is now fully created, mark it as persistent if needed */
+	if (!temporary)
+		ReplicationSlotPersist();
+	ReplicationSlotRelease();
+
+	PG_RETURN_DATUM(result);
+}
+
+
+/*
+ * SQL function for dropping a replication slot.
+ */
+Datum
+pg_drop_replication_slot(PG_FUNCTION_ARGS)
+{
+	Name		name = PG_GETARG_NAME(0);
+
+	check_permissions();
+
+	CheckSlotRequirements();
+
+	ReplicationSlotDrop(NameStr(*name), true);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * pg_get_replication_slots - SQL SRF showing active replication slots.
+ */
+Datum
+pg_get_replication_slots(PG_FUNCTION_ARGS)
+{
+#define PG_GET_REPLICATION_SLOTS_COLS 14
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+	TupleDesc	tupdesc;
+	Tuplestorestate *tupstore;
+	MemoryContext per_query_ctx;
+	MemoryContext oldcontext;
+	XLogRecPtr	currlsn;
+	int			slotno;
+
+	/* check to see if caller supports us returning a tuplestore */
+	if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("set-valued function called in context that cannot accept a set")));
+	if (!(rsinfo->allowedModes & SFRM_Materialize))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("materialize mode required, but it is not allowed in this context")));
+
+	/* Build a tuple descriptor for our result type */
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+		elog(ERROR, "return type must be a row type");
+
+	/*
+	 * We don't require any special permission to see this function's data
+	 * because nothing should be sensitive. The most critical being the slot
+	 * name, which shouldn't contain anything particularly sensitive.
+	 */
+
+	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
+	oldcontext = MemoryContextSwitchTo(per_query_ctx);
+
+	tupstore = tuplestore_begin_heap(true, false, work_mem);
+	rsinfo->returnMode = SFRM_Materialize;
+	rsinfo->setResult = tupstore;
+	rsinfo->setDesc = tupdesc;
+
+	MemoryContextSwitchTo(oldcontext);
+
+	currlsn = GetXLogWriteRecPtr();
+
+	LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
+	for (slotno = 0; slotno < max_replication_slots; slotno++)
+	{
+		ReplicationSlot *slot = &ReplicationSlotCtl->replication_slots[slotno];
+		ReplicationSlot slot_contents;
+		Datum		values[PG_GET_REPLICATION_SLOTS_COLS];
+		bool		nulls[PG_GET_REPLICATION_SLOTS_COLS];
+		WALAvailability walstate;
+		int			i;
+
+		if (!slot->in_use)
+			continue;
+
+		/* Copy slot contents while holding spinlock, then examine at leisure */
+		SpinLockAcquire(&slot->mutex);
+		slot_contents = *slot;
+		SpinLockRelease(&slot->mutex);
+
+		memset(values, 0, sizeof(values));
+		memset(nulls, 0, sizeof(nulls));
+
+		i = 0;
+		values[i++] = NameGetDatum(&slot_contents.data.name);
+
+		if (slot_contents.data.database == InvalidOid)
+			nulls[i++] = true;
+		else
+			values[i++] = NameGetDatum(&slot_contents.data.plugin);
+
+		if (slot_contents.data.database == InvalidOid)
+			values[i++] = CStringGetTextDatum("physical");
+		else
+			values[i++] = CStringGetTextDatum("logical");
+
+		if (slot_contents.data.database == InvalidOid)
+			nulls[i++] = true;
+		else
+			values[i++] = ObjectIdGetDatum(slot_contents.data.database);
+
+		values[i++] = BoolGetDatum(slot_contents.data.persistency == RS_TEMPORARY);
+		values[i++] = BoolGetDatum(slot_contents.active_pid != 0);
+
+		if (slot_contents.active_pid != 0)
+			values[i++] = Int32GetDatum(slot_contents.active_pid);
+		else
+			nulls[i++] = true;
+
+		if (slot_contents.data.xmin != InvalidTransactionId)
+			values[i++] = TransactionIdGetDatum(slot_contents.data.xmin);
+		else
+			nulls[i++] = true;
+
+		if (slot_contents.data.catalog_xmin != InvalidTransactionId)
+			values[i++] = TransactionIdGetDatum(slot_contents.data.catalog_xmin);
+		else
+			nulls[i++] = true;
+
+		if (slot_contents.data.restart_lsn != InvalidXLogRecPtr)
+			values[i++] = LSNGetDatum(slot_contents.data.restart_lsn);
+		else
+			nulls[i++] = true;
+
+		if (slot_contents.data.confirmed_flush != InvalidXLogRecPtr)
+			values[i++] = LSNGetDatum(slot_contents.data.confirmed_flush);
+		else
+			nulls[i++] = true;
+
+		/*
+		 * If invalidated_at is valid and restart_lsn is invalid, we know for
+		 * certain that the slot has been invalidated.  Otherwise, test
+		 * availability from restart_lsn.
+		 */
+		if (XLogRecPtrIsInvalid(slot_contents.data.restart_lsn) &&
+			!XLogRecPtrIsInvalid(slot_contents.data.invalidated_at))
+			walstate = WALAVAIL_REMOVED;
+		else
+			walstate = GetWALAvailability(slot_contents.data.restart_lsn);
+
+		switch (walstate)
+		{
+			case WALAVAIL_INVALID_LSN:
+				nulls[i++] = true;
+				break;
+
+			case WALAVAIL_RESERVED:
+				values[i++] = CStringGetTextDatum("reserved");
+				break;
+
+			case WALAVAIL_EXTENDED:
+				values[i++] = CStringGetTextDatum("extended");
+				break;
+
+			case WALAVAIL_UNRESERVED:
+				values[i++] = CStringGetTextDatum("unreserved");
+				break;
+
+			case WALAVAIL_REMOVED:
+
+				/*
+				 * If we read the restart_lsn long enough ago, maybe that file
+				 * has been removed by now.  However, the walsender could have
+				 * moved forward enough that it jumped to another file after
+				 * we looked.  If checkpointer signalled the process to
+				 * termination, then it's definitely lost; but if a process is
+				 * still alive, then "unreserved" seems more appropriate.
+				 *
+				 * If we do change it, save the state for safe_wal_size below.
+				 */
+				if (!XLogRecPtrIsInvalid(slot_contents.data.restart_lsn))
+				{
+					int			pid;
+
+					SpinLockAcquire(&slot->mutex);
+					pid = slot->active_pid;
+					slot_contents.data.restart_lsn = slot->data.restart_lsn;
+					SpinLockRelease(&slot->mutex);
+					if (pid != 0)
+					{
+						values[i++] = CStringGetTextDatum("unreserved");
+						walstate = WALAVAIL_UNRESERVED;
+						break;
+					}
+				}
+				values[i++] = CStringGetTextDatum("lost");
+				break;
+		}
+
+		/*
+		 * safe_wal_size is only computed for slots that have not been lost,
+		 * and only if there's a configured maximum size.
+		 */
+		if (walstate == WALAVAIL_REMOVED || max_slot_wal_keep_size_mb < 0)
+			nulls[i++] = true;
+		else
+		{
+			XLogSegNo	targetSeg;
+			uint64		slotKeepSegs;
+			uint64		keepSegs;
+			XLogSegNo	failSeg;
+			XLogRecPtr	failLSN;
+
+			XLByteToSeg(slot_contents.data.restart_lsn, targetSeg, wal_segment_size);
+
+			/* determine how many segments slots can be kept by slots */
+			slotKeepSegs = XLogMBVarToSegs(max_slot_wal_keep_size_mb, wal_segment_size);
+			/* ditto for wal_keep_size */
+			keepSegs = XLogMBVarToSegs(wal_keep_size_mb, wal_segment_size);
+
+			/* if currpos reaches failLSN, we lose our segment */
+			failSeg = targetSeg + Max(slotKeepSegs, keepSegs) + 1;
+			XLogSegNoOffsetToRecPtr(failSeg, 0, wal_segment_size, failLSN);
+
+			values[i++] = Int64GetDatum(failLSN - currlsn);
+		}
+
+		values[i++] = BoolGetDatum(slot_contents.data.two_phase);
+
+		Assert(i == PG_GET_REPLICATION_SLOTS_COLS);
+
+		tuplestore_putvalues(tupstore, tupdesc, values, nulls);
+	}
+
+	LWLockRelease(ReplicationSlotControlLock);
+
+	tuplestore_donestoring(tupstore);
+
+	return (Datum) 0;
+}
+
+/*
+ * Helper function for advancing our physical replication slot forward.
+ *
+ * The LSN position to move to is compared simply to the slot's restart_lsn,
+ * knowing that any position older than that would be removed by successive
+ * checkpoints.
+ */
+static XLogRecPtr
+pg_physical_replication_slot_advance(XLogRecPtr moveto)
+{
+	XLogRecPtr	startlsn = MyReplicationSlot->data.restart_lsn;
+	XLogRecPtr	retlsn = startlsn;
+
+	Assert(moveto != InvalidXLogRecPtr);
+
+	if (startlsn < moveto)
+	{
+		SpinLockAcquire(&MyReplicationSlot->mutex);
+		MyReplicationSlot->data.restart_lsn = moveto;
+		SpinLockRelease(&MyReplicationSlot->mutex);
+		retlsn = moveto;
+
+		/*
+		 * Dirty the slot so as it is written out at the next checkpoint. Note
+		 * that the LSN position advanced may still be lost in the event of a
+		 * crash, but this makes the data consistent after a clean shutdown.
+		 */
+		ReplicationSlotMarkDirty();
+	}
+
+	return retlsn;
+}
+
+/*
+ * Helper function for advancing our logical replication slot forward.
+ *
+ * The slot's restart_lsn is used as start point for reading records, while
+ * confirmed_flush is used as base point for the decoding context.
+ *
+ * We cannot just do LogicalConfirmReceivedLocation to update confirmed_flush,
+ * because we need to digest WAL to advance restart_lsn allowing to recycle
+ * WAL and removal of old catalog tuples.  As decoding is done in fast_forward
+ * mode, no changes are generated anyway.
+ */
+static XLogRecPtr
+pg_logical_replication_slot_advance(XLogRecPtr moveto)
+{
+	LogicalDecodingContext *ctx;
+	ResourceOwner old_resowner = CurrentResourceOwner;
+	XLogRecPtr	retlsn;
+
+	Assert(moveto != InvalidXLogRecPtr);
+
+	PG_TRY();
+	{
+		/*
+		 * Create our decoding context in fast_forward mode, passing start_lsn
+		 * as InvalidXLogRecPtr, so that we start processing from my slot's
+		 * confirmed_flush.
+		 */
+		ctx = CreateDecodingContext(InvalidXLogRecPtr,
+									NIL,
+									true,	/* fast_forward */
+									XL_ROUTINE(.page_read = read_local_xlog_page,
+											   .segment_open = wal_segment_open,
+											   .segment_close = wal_segment_close),
+									NULL, NULL, NULL);
+
+		/*
+		 * Start reading at the slot's restart_lsn, which we know to point to
+		 * a valid record.
+		 */
+		XLogBeginRead(ctx->reader, MyReplicationSlot->data.restart_lsn);
+
+		/* invalidate non-timetravel entries */
+		InvalidateSystemCaches();
+
+		/* Decode at least one record, until we run out of records */
+		while (ctx->reader->EndRecPtr < moveto)
+		{
+			char	   *errm = NULL;
+			XLogRecord *record;
+
+			/*
+			 * Read records.  No changes are generated in fast_forward mode,
+			 * but snapbuilder/slot statuses are updated properly.
+			 */
+			record = XLogReadRecord(ctx->reader, &errm);
+			if (errm)
+				elog(ERROR, "%s", errm);
+
+			/*
+			 * Process the record.  Storage-level changes are ignored in
+			 * fast_forward mode, but other modules (such as snapbuilder)
+			 * might still have critical updates to do.
+			 */
+			if (record)
+				LogicalDecodingProcessRecord(ctx, ctx->reader);
+
+			/* Stop once the requested target has been reached */
+			if (moveto <= ctx->reader->EndRecPtr)
+				break;
+
+			CHECK_FOR_INTERRUPTS();
+		}
+
+		/*
+		 * Logical decoding could have clobbered CurrentResourceOwner during
+		 * transaction management, so restore the executor's value.  (This is
+		 * a kluge, but it's not worth cleaning up right now.)
+		 */
+		CurrentResourceOwner = old_resowner;
+
+		if (ctx->reader->EndRecPtr != InvalidXLogRecPtr)
+		{
+			LogicalConfirmReceivedLocation(moveto);
+
+			/*
+			 * If only the confirmed_flush LSN has changed the slot won't get
+			 * marked as dirty by the above. Callers on the walsender
+			 * interface are expected to keep track of their own progress and
+			 * don't need it written out. But SQL-interface users cannot
+			 * specify their own start positions and it's harder for them to
+			 * keep track of their progress, so we should make more of an
+			 * effort to save it for them.
+			 *
+			 * Dirty the slot so it is written out at the next checkpoint. The
+			 * LSN position advanced to may still be lost on a crash but this
+			 * makes the data consistent after a clean shutdown.
+			 */
+			ReplicationSlotMarkDirty();
+		}
+
+		retlsn = MyReplicationSlot->data.confirmed_flush;
+
+		/* free context, call shutdown callback */
+		FreeDecodingContext(ctx);
+
+		InvalidateSystemCaches();
+	}
+	PG_CATCH();
+	{
+		/* clear all timetravel entries */
+		InvalidateSystemCaches();
+
+		PG_RE_THROW();
+	}
+	PG_END_TRY();
+
+	return retlsn;
+}
+
+/*
+ * SQL function for moving the position in a replication slot.
+ */
+Datum
+pg_replication_slot_advance(PG_FUNCTION_ARGS)
+{
+	Name		slotname = PG_GETARG_NAME(0);
+	XLogRecPtr	moveto = PG_GETARG_LSN(1);
+	XLogRecPtr	endlsn;
+	XLogRecPtr	minlsn;
+	TupleDesc	tupdesc;
+	Datum		values[2];
+	bool		nulls[2];
+	HeapTuple	tuple;
+	Datum		result;
+
+	Assert(!MyReplicationSlot);
+
+	check_permissions();
+
+	if (XLogRecPtrIsInvalid(moveto))
+		ereport(ERROR,
+				(errmsg("invalid target WAL LSN")));
+
+	/* Build a tuple descriptor for our result type */
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+		elog(ERROR, "return type must be a row type");
+
+	/*
+	 * We can't move slot past what's been flushed/replayed so clamp the
+	 * target position accordingly.
+	 */
+	if (!RecoveryInProgress())
+		moveto = Min(moveto, GetFlushRecPtr());
+	else
+		moveto = Min(moveto, GetXLogReplayRecPtr(&ThisTimeLineID));
+
+	/* Acquire the slot so we "own" it */
+	ReplicationSlotAcquire(NameStr(*slotname), true);
+
+	/* A slot whose restart_lsn has never been reserved cannot be advanced */
+	if (XLogRecPtrIsInvalid(MyReplicationSlot->data.restart_lsn))
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("replication slot \"%s\" cannot be advanced",
+						NameStr(*slotname)),
+				 errdetail("This slot has never previously reserved WAL, or it has been invalidated.")));
+
+	/*
+	 * Check if the slot is not moving backwards.  Physical slots rely simply
+	 * on restart_lsn as a minimum point, while logical slots have confirmed
+	 * consumption up to confirmed_flush, meaning that in both cases data
+	 * older than that is not available anymore.
+	 */
+	if (OidIsValid(MyReplicationSlot->data.database))
+		minlsn = MyReplicationSlot->data.confirmed_flush;
+	else
+		minlsn = MyReplicationSlot->data.restart_lsn;
+
+	if (moveto < minlsn)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("cannot advance replication slot to %X/%X, minimum is %X/%X",
+						LSN_FORMAT_ARGS(moveto), LSN_FORMAT_ARGS(minlsn))));
+
+	/* Do the actual slot update, depending on the slot type */
+	if (OidIsValid(MyReplicationSlot->data.database))
+		endlsn = pg_logical_replication_slot_advance(moveto);
+	else
+		endlsn = pg_physical_replication_slot_advance(moveto);
+
+	values[0] = NameGetDatum(&MyReplicationSlot->data.name);
+	nulls[0] = false;
+
+	/*
+	 * Recompute the minimum LSN and xmin across all slots to adjust with the
+	 * advancing potentially done.
+	 */
+	ReplicationSlotsComputeRequiredXmin(false);
+	ReplicationSlotsComputeRequiredLSN();
+
+	ReplicationSlotRelease();
+
+	/* Return the reached position. */
+	values[1] = LSNGetDatum(endlsn);
+	nulls[1] = false;
+
+	tuple = heap_form_tuple(tupdesc, values, nulls);
+	result = HeapTupleGetDatum(tuple);
+
+	PG_RETURN_DATUM(result);
+}
+
+/*
+ * Helper function of copying a replication slot.
+ */
+static Datum
+copy_replication_slot(FunctionCallInfo fcinfo, bool logical_slot)
+{
+	Name		src_name = PG_GETARG_NAME(0);
+	Name		dst_name = PG_GETARG_NAME(1);
+	ReplicationSlot *src = NULL;
+	ReplicationSlot first_slot_contents;
+	ReplicationSlot second_slot_contents;
+	XLogRecPtr	src_restart_lsn;
+	bool		src_islogical;
+	bool		temporary;
+	char	   *plugin;
+	Datum		values[2];
+	bool		nulls[2];
+	Datum		result;
+	TupleDesc	tupdesc;
+	HeapTuple	tuple;
+
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+		elog(ERROR, "return type must be a row type");
+
+	check_permissions();
+
+	if (logical_slot)
+		CheckLogicalDecodingRequirements();
+	else
+		CheckSlotRequirements();
+
+	LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
+
+	/*
+	 * We need to prevent the source slot's reserved WAL from being removed,
+	 * but we don't want to lock that slot for very long, and it can advance
+	 * in the meantime.  So obtain the source slot's data, and create a new
+	 * slot using its restart_lsn.  Afterwards we lock the source slot again
+	 * and verify that the data we copied (name, type) has not changed
+	 * incompatibly.  No inconvenient WAL removal can occur once the new slot
+	 * is created -- but since WAL removal could have occurred before we
+	 * managed to create the new slot, we advance the new slot's restart_lsn
+	 * to the source slot's updated restart_lsn the second time we lock it.
+	 */
+	for (int i = 0; i < max_replication_slots; i++)
+	{
+		ReplicationSlot *s = &ReplicationSlotCtl->replication_slots[i];
+
+		if (s->in_use && strcmp(NameStr(s->data.name), NameStr(*src_name)) == 0)
+		{
+			/* Copy the slot contents while holding spinlock */
+			SpinLockAcquire(&s->mutex);
+			first_slot_contents = *s;
+			SpinLockRelease(&s->mutex);
+			src = s;
+			break;
+		}
+	}
+
+	LWLockRelease(ReplicationSlotControlLock);
+
+	if (src == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("replication slot \"%s\" does not exist", NameStr(*src_name))));
+
+	src_islogical = SlotIsLogical(&first_slot_contents);
+	src_restart_lsn = first_slot_contents.data.restart_lsn;
+	temporary = (first_slot_contents.data.persistency == RS_TEMPORARY);
+	plugin = logical_slot ? NameStr(first_slot_contents.data.plugin) : NULL;
+
+	/* Check type of replication slot */
+	if (src_islogical != logical_slot)
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 src_islogical ?
+				 errmsg("cannot copy physical replication slot \"%s\" as a logical replication slot",
+						NameStr(*src_name)) :
+				 errmsg("cannot copy logical replication slot \"%s\" as a physical replication slot",
+						NameStr(*src_name))));
+
+	/* Copying non-reserved slot doesn't make sense */
+	if (XLogRecPtrIsInvalid(src_restart_lsn))
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("cannot copy a replication slot that doesn't reserve WAL")));
+
+	/* Overwrite params from optional arguments */
+	if (PG_NARGS() >= 3)
+		temporary = PG_GETARG_BOOL(2);
+	if (PG_NARGS() >= 4)
+	{
+		Assert(logical_slot);
+		plugin = NameStr(*(PG_GETARG_NAME(3)));
+	}
+
+	/* Create new slot and acquire it */
+	if (logical_slot)
+	{
+		/*
+		 * We must not try to read WAL, since we haven't reserved it yet --
+		 * hence pass find_startpoint false.  confirmed_flush will be set
+		 * below, by copying from the source slot.
+		 */
+		create_logical_replication_slot(NameStr(*dst_name),
+										plugin,
+										temporary,
+										false,
+										src_restart_lsn,
+										false);
+	}
+	else
+		create_physical_replication_slot(NameStr(*dst_name),
+										 true,
+										 temporary,
+										 src_restart_lsn);
+
+	/*
+	 * Update the destination slot to current values of the source slot;
+	 * recheck that the source slot is still the one we saw previously.
+	 */
+	{
+		TransactionId copy_effective_xmin;
+		TransactionId copy_effective_catalog_xmin;
+		TransactionId copy_xmin;
+		TransactionId copy_catalog_xmin;
+		XLogRecPtr	copy_restart_lsn;
+		XLogRecPtr	copy_confirmed_flush;
+		bool		copy_islogical;
+		char	   *copy_name;
+
+		/* Copy data of source slot again */
+		SpinLockAcquire(&src->mutex);
+		second_slot_contents = *src;
+		SpinLockRelease(&src->mutex);
+
+		copy_effective_xmin = second_slot_contents.effective_xmin;
+		copy_effective_catalog_xmin = second_slot_contents.effective_catalog_xmin;
+
+		copy_xmin = second_slot_contents.data.xmin;
+		copy_catalog_xmin = second_slot_contents.data.catalog_xmin;
+		copy_restart_lsn = second_slot_contents.data.restart_lsn;
+		copy_confirmed_flush = second_slot_contents.data.confirmed_flush;
+
+		/* for existence check */
+		copy_name = NameStr(second_slot_contents.data.name);
+		copy_islogical = SlotIsLogical(&second_slot_contents);
+
+		/*
+		 * Check if the source slot still exists and is valid. We regard it as
+		 * invalid if the type of replication slot or name has been changed,
+		 * or the restart_lsn either is invalid or has gone backward. (The
+		 * restart_lsn could go backwards if the source slot is dropped and
+		 * copied from an older slot during installation.)
+		 *
+		 * Since erroring out will release and drop the destination slot we
+		 * don't need to release it here.
+		 */
+		if (copy_restart_lsn < src_restart_lsn ||
+			src_islogical != copy_islogical ||
+			strcmp(copy_name, NameStr(*src_name)) != 0)
+			ereport(ERROR,
+					(errmsg("could not copy replication slot \"%s\"",
+							NameStr(*src_name)),
+					 errdetail("The source replication slot was modified incompatibly during the copy operation.")));
+
+		/* The source slot must have a consistent snapshot */
+		if (src_islogical && XLogRecPtrIsInvalid(copy_confirmed_flush))
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("cannot copy unfinished logical replication slot \"%s\"",
+							NameStr(*src_name)),
+					 errhint("Retry when the source replication slot's confirmed_flush_lsn is valid.")));
+
+		/* Install copied values again */
+		SpinLockAcquire(&MyReplicationSlot->mutex);
+		MyReplicationSlot->effective_xmin = copy_effective_xmin;
+		MyReplicationSlot->effective_catalog_xmin = copy_effective_catalog_xmin;
+
+		MyReplicationSlot->data.xmin = copy_xmin;
+		MyReplicationSlot->data.catalog_xmin = copy_catalog_xmin;
+		MyReplicationSlot->data.restart_lsn = copy_restart_lsn;
+		MyReplicationSlot->data.confirmed_flush = copy_confirmed_flush;
+		SpinLockRelease(&MyReplicationSlot->mutex);
+
+		ReplicationSlotMarkDirty();
+		ReplicationSlotsComputeRequiredXmin(false);
+		ReplicationSlotsComputeRequiredLSN();
+		ReplicationSlotSave();
+
+#ifdef USE_ASSERT_CHECKING
+		/* Check that the restart_lsn is available */
+		{
+			XLogSegNo	segno;
+
+			XLByteToSeg(copy_restart_lsn, segno, wal_segment_size);
+			Assert(XLogGetLastRemovedSegno() < segno);
+		}
+#endif
+	}
+
+	/* target slot fully created, mark as persistent if needed */
+	if (logical_slot && !temporary)
+		ReplicationSlotPersist();
+
+	/* All done.  Set up the return values */
+	values[0] = NameGetDatum(dst_name);
+	nulls[0] = false;
+	if (!XLogRecPtrIsInvalid(MyReplicationSlot->data.confirmed_flush))
+	{
+		values[1] = LSNGetDatum(MyReplicationSlot->data.confirmed_flush);
+		nulls[1] = false;
+	}
+	else
+		nulls[1] = true;
+
+	tuple = heap_form_tuple(tupdesc, values, nulls);
+	result = HeapTupleGetDatum(tuple);
+
+	ReplicationSlotRelease();
+
+	PG_RETURN_DATUM(result);
+}
+
+/* The wrappers below are all to appease opr_sanity */
+Datum
+pg_copy_logical_replication_slot_a(PG_FUNCTION_ARGS)
+{
+	return copy_replication_slot(fcinfo, true);
+}
+
+Datum
+pg_copy_logical_replication_slot_b(PG_FUNCTION_ARGS)
+{
+	return copy_replication_slot(fcinfo, true);
+}
+
+Datum
+pg_copy_logical_replication_slot_c(PG_FUNCTION_ARGS)
+{
+	return copy_replication_slot(fcinfo, true);
+}
+
+Datum
+pg_copy_physical_replication_slot_a(PG_FUNCTION_ARGS)
+{
+	return copy_replication_slot(fcinfo, false);
+}
+
+Datum
+pg_copy_physical_replication_slot_b(PG_FUNCTION_ARGS)
+{
+	return copy_replication_slot(fcinfo, false);
+}
diff --git a/src/backend/replication/syncrep.c b/src/backend/replication/syncrep.c
new file mode 100644
index 0000000..bdbc9ef
--- /dev/null
+++ b/src/backend/replication/syncrep.c
@@ -0,0 +1,1103 @@
+/*-------------------------------------------------------------------------
+ *
+ * syncrep.c
+ *
+ * Synchronous replication is new as of PostgreSQL 9.1.
+ *
+ * If requested, transaction commits wait until their commit LSN are
+ * acknowledged by the synchronous standbys.
+ *
+ * This module contains the code for waiting and release of backends.
+ * All code in this module executes on the primary. The core streaming
+ * replication transport remains within WALreceiver/WALsender modules.
+ *
+ * The essence of this design is that it isolates all logic about
+ * waiting/releasing onto the primary. The primary defines which standbys
+ * it wishes to wait for. The standbys are completely unaware of the
+ * durability requirements of transactions on the primary, reducing the
+ * complexity of the code and streamlining both standby operations and
+ * network bandwidth because there is no requirement to ship
+ * per-transaction state information.
+ *
+ * Replication is either synchronous or not synchronous (async). If it is
+ * async, we just fastpath out of here. If it is sync, then we wait for
+ * the write, flush or apply location on the standby before releasing
+ * the waiting backend. Further complexity in that interaction is
+ * expected in later releases.
+ *
+ * The best performing way to manage the waiting backends is to have a
+ * single ordered queue of waiting backends, so that we can avoid
+ * searching the through all waiters each time we receive a reply.
+ *
+ * In 9.5 or before only a single standby could be considered as
+ * synchronous. In 9.6 we support a priority-based multiple synchronous
+ * standbys. In 10.0 a quorum-based multiple synchronous standbys is also
+ * supported. The number of synchronous standbys that transactions
+ * must wait for replies from is specified in synchronous_standby_names.
+ * This parameter also specifies a list of standby names and the method
+ * (FIRST and ANY) to choose synchronous standbys from the listed ones.
+ *
+ * The method FIRST specifies a priority-based synchronous replication
+ * and makes transaction commits wait until their WAL records are
+ * replicated to the requested number of synchronous standbys chosen based
+ * on their priorities. The standbys whose names appear earlier in the list
+ * are given higher priority and will be considered as synchronous.
+ * Other standby servers appearing later in this list represent potential
+ * synchronous standbys. If any of the current synchronous standbys
+ * disconnects for whatever reason, it will be replaced immediately with
+ * the next-highest-priority standby.
+ *
+ * The method ANY specifies a quorum-based synchronous replication
+ * and makes transaction commits wait until their WAL records are
+ * replicated to at least the requested number of synchronous standbys
+ * in the list. All the standbys appearing in the list are considered as
+ * candidates for quorum synchronous standbys.
+ *
+ * If neither FIRST nor ANY is specified, FIRST is used as the method.
+ * This is for backward compatibility with 9.6 or before where only a
+ * priority-based sync replication was supported.
+ *
+ * Before the standbys chosen from synchronous_standby_names can
+ * become the synchronous standbys they must have caught up with
+ * the primary; that may take some time. Once caught up,
+ * the standbys which are considered as synchronous at that moment
+ * will release waiters from the queue.
+ *
+ * Portions Copyright (c) 2010-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/syncrep.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <unistd.h>
+
+#include "access/xact.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "replication/syncrep.h"
+#include "replication/walsender.h"
+#include "replication/walsender_private.h"
+#include "storage/pmsignal.h"
+#include "storage/proc.h"
+#include "tcop/tcopprot.h"
+#include "utils/builtins.h"
+#include "utils/ps_status.h"
+
+/* User-settable parameters for sync rep */
+char	   *SyncRepStandbyNames;
+
+#define SyncStandbysDefined() \
+	(SyncRepStandbyNames != NULL && SyncRepStandbyNames[0] != '\0')
+
+static bool announce_next_takeover = true;
+
+SyncRepConfigData *SyncRepConfig = NULL;
+static int	SyncRepWaitMode = SYNC_REP_NO_WAIT;
+
+static void SyncRepQueueInsert(int mode);
+static void SyncRepCancelWait(void);
+static int	SyncRepWakeQueue(bool all, int mode);
+
+static bool SyncRepGetSyncRecPtr(XLogRecPtr *writePtr,
+								 XLogRecPtr *flushPtr,
+								 XLogRecPtr *applyPtr,
+								 bool *am_sync);
+static void SyncRepGetOldestSyncRecPtr(XLogRecPtr *writePtr,
+									   XLogRecPtr *flushPtr,
+									   XLogRecPtr *applyPtr,
+									   SyncRepStandbyData *sync_standbys,
+									   int num_standbys);
+static void SyncRepGetNthLatestSyncRecPtr(XLogRecPtr *writePtr,
+										  XLogRecPtr *flushPtr,
+										  XLogRecPtr *applyPtr,
+										  SyncRepStandbyData *sync_standbys,
+										  int num_standbys,
+										  uint8 nth);
+static int	SyncRepGetStandbyPriority(void);
+static int	standby_priority_comparator(const void *a, const void *b);
+static int	cmp_lsn(const void *a, const void *b);
+
+#ifdef USE_ASSERT_CHECKING
+static bool SyncRepQueueIsOrderedByLSN(int mode);
+#endif
+
+/*
+ * ===========================================================
+ * Synchronous Replication functions for normal user backends
+ * ===========================================================
+ */
+
+/*
+ * Wait for synchronous replication, if requested by user.
+ *
+ * Initially backends start in state SYNC_REP_NOT_WAITING and then
+ * change that state to SYNC_REP_WAITING before adding ourselves
+ * to the wait queue. During SyncRepWakeQueue() a WALSender changes
+ * the state to SYNC_REP_WAIT_COMPLETE once replication is confirmed.
+ * This backend then resets its state to SYNC_REP_NOT_WAITING.
+ *
+ * 'lsn' represents the LSN to wait for.  'commit' indicates whether this LSN
+ * represents a commit record.  If it doesn't, then we wait only for the WAL
+ * to be flushed if synchronous_commit is set to the higher level of
+ * remote_apply, because only commit records provide apply feedback.
+ */
+void
+SyncRepWaitForLSN(XLogRecPtr lsn, bool commit)
+{
+	char	   *new_status = NULL;
+	const char *old_status;
+	int			mode;
+
+	/*
+	 * This should be called while holding interrupts during a transaction
+	 * commit to prevent the follow-up shared memory queue cleanups to be
+	 * influenced by external interruptions.
+	 */
+	Assert(InterruptHoldoffCount > 0);
+
+	/*
+	 * Fast exit if user has not requested sync replication, or there are no
+	 * sync replication standby names defined.
+	 *
+	 * Since this routine gets called every commit time, it's important to
+	 * exit quickly if sync replication is not requested. So we check
+	 * WalSndCtl->sync_standbys_defined flag without the lock and exit
+	 * immediately if it's false. If it's true, we need to check it again
+	 * later while holding the lock, to check the flag and operate the sync
+	 * rep queue atomically. This is necessary to avoid the race condition
+	 * described in SyncRepUpdateSyncStandbysDefined(). On the other hand, if
+	 * it's false, the lock is not necessary because we don't touch the queue.
+	 */
+	if (!SyncRepRequested() ||
+		!((volatile WalSndCtlData *) WalSndCtl)->sync_standbys_defined)
+		return;
+
+	/* Cap the level for anything other than commit to remote flush only. */
+	if (commit)
+		mode = SyncRepWaitMode;
+	else
+		mode = Min(SyncRepWaitMode, SYNC_REP_WAIT_FLUSH);
+
+	Assert(SHMQueueIsDetached(&(MyProc->syncRepLinks)));
+	Assert(WalSndCtl != NULL);
+
+	LWLockAcquire(SyncRepLock, LW_EXCLUSIVE);
+	Assert(MyProc->syncRepState == SYNC_REP_NOT_WAITING);
+
+	/*
+	 * We don't wait for sync rep if WalSndCtl->sync_standbys_defined is not
+	 * set.  See SyncRepUpdateSyncStandbysDefined.
+	 *
+	 * Also check that the standby hasn't already replied. Unlikely race
+	 * condition but we'll be fetching that cache line anyway so it's likely
+	 * to be a low cost check.
+	 */
+	if (!WalSndCtl->sync_standbys_defined ||
+		lsn <= WalSndCtl->lsn[mode])
+	{
+		LWLockRelease(SyncRepLock);
+		return;
+	}
+
+	/*
+	 * Set our waitLSN so WALSender will know when to wake us, and add
+	 * ourselves to the queue.
+	 */
+	MyProc->waitLSN = lsn;
+	MyProc->syncRepState = SYNC_REP_WAITING;
+	SyncRepQueueInsert(mode);
+	Assert(SyncRepQueueIsOrderedByLSN(mode));
+	LWLockRelease(SyncRepLock);
+
+	/* Alter ps display to show waiting for sync rep. */
+	if (update_process_title)
+	{
+		int			len;
+
+		old_status = get_ps_display(&len);
+		new_status = (char *) palloc(len + 32 + 1);
+		memcpy(new_status, old_status, len);
+		sprintf(new_status + len, " waiting for %X/%X",
+				LSN_FORMAT_ARGS(lsn));
+		set_ps_display(new_status);
+		new_status[len] = '\0'; /* truncate off " waiting ..." */
+	}
+
+	/*
+	 * Wait for specified LSN to be confirmed.
+	 *
+	 * Each proc has its own wait latch, so we perform a normal latch
+	 * check/wait loop here.
+	 */
+	for (;;)
+	{
+		int			rc;
+
+		/* Must reset the latch before testing state. */
+		ResetLatch(MyLatch);
+
+		/*
+		 * Acquiring the lock is not needed, the latch ensures proper
+		 * barriers. If it looks like we're done, we must really be done,
+		 * because once walsender changes the state to SYNC_REP_WAIT_COMPLETE,
+		 * it will never update it again, so we can't be seeing a stale value
+		 * in that case.
+		 */
+		if (MyProc->syncRepState == SYNC_REP_WAIT_COMPLETE)
+			break;
+
+		/*
+		 * If a wait for synchronous replication is pending, we can neither
+		 * acknowledge the commit nor raise ERROR or FATAL.  The latter would
+		 * lead the client to believe that the transaction aborted, which is
+		 * not true: it's already committed locally. The former is no good
+		 * either: the client has requested synchronous replication, and is
+		 * entitled to assume that an acknowledged commit is also replicated,
+		 * which might not be true. So in this case we issue a WARNING (which
+		 * some clients may be able to interpret) and shut off further output.
+		 * We do NOT reset ProcDiePending, so that the process will die after
+		 * the commit is cleaned up.
+		 */
+		if (ProcDiePending)
+		{
+			ereport(WARNING,
+					(errcode(ERRCODE_ADMIN_SHUTDOWN),
+					 errmsg("canceling the wait for synchronous replication and terminating connection due to administrator command"),
+					 errdetail("The transaction has already committed locally, but might not have been replicated to the standby.")));
+			whereToSendOutput = DestNone;
+			SyncRepCancelWait();
+			break;
+		}
+
+		/*
+		 * It's unclear what to do if a query cancel interrupt arrives.  We
+		 * can't actually abort at this point, but ignoring the interrupt
+		 * altogether is not helpful, so we just terminate the wait with a
+		 * suitable warning.
+		 */
+		if (QueryCancelPending)
+		{
+			QueryCancelPending = false;
+			ereport(WARNING,
+					(errmsg("canceling wait for synchronous replication due to user request"),
+					 errdetail("The transaction has already committed locally, but might not have been replicated to the standby.")));
+			SyncRepCancelWait();
+			break;
+		}
+
+		/*
+		 * Wait on latch.  Any condition that should wake us up will set the
+		 * latch, so no need for timeout.
+		 */
+		rc = WaitLatch(MyLatch, WL_LATCH_SET | WL_POSTMASTER_DEATH, -1,
+					   WAIT_EVENT_SYNC_REP);
+
+		/*
+		 * If the postmaster dies, we'll probably never get an acknowledgment,
+		 * because all the wal sender processes will exit. So just bail out.
+		 */
+		if (rc & WL_POSTMASTER_DEATH)
+		{
+			ProcDiePending = true;
+			whereToSendOutput = DestNone;
+			SyncRepCancelWait();
+			break;
+		}
+	}
+
+	/*
+	 * WalSender has checked our LSN and has removed us from queue. Clean up
+	 * state and leave.  It's OK to reset these shared memory fields without
+	 * holding SyncRepLock, because any walsenders will ignore us anyway when
+	 * we're not on the queue.  We need a read barrier to make sure we see the
+	 * changes to the queue link (this might be unnecessary without
+	 * assertions, but better safe than sorry).
+	 */
+	pg_read_barrier();
+	Assert(SHMQueueIsDetached(&(MyProc->syncRepLinks)));
+	MyProc->syncRepState = SYNC_REP_NOT_WAITING;
+	MyProc->waitLSN = 0;
+
+	if (new_status)
+	{
+		/* Reset ps display */
+		set_ps_display(new_status);
+		pfree(new_status);
+	}
+}
+
+/*
+ * Insert MyProc into the specified SyncRepQueue, maintaining sorted invariant.
+ *
+ * Usually we will go at tail of queue, though it's possible that we arrive
+ * here out of order, so start at tail and work back to insertion point.
+ */
+static void
+SyncRepQueueInsert(int mode)
+{
+	PGPROC	   *proc;
+
+	Assert(mode >= 0 && mode < NUM_SYNC_REP_WAIT_MODE);
+	proc = (PGPROC *) SHMQueuePrev(&(WalSndCtl->SyncRepQueue[mode]),
+								   &(WalSndCtl->SyncRepQueue[mode]),
+								   offsetof(PGPROC, syncRepLinks));
+
+	while (proc)
+	{
+		/*
+		 * Stop at the queue element that we should after to ensure the queue
+		 * is ordered by LSN.
+		 */
+		if (proc->waitLSN < MyProc->waitLSN)
+			break;
+
+		proc = (PGPROC *) SHMQueuePrev(&(WalSndCtl->SyncRepQueue[mode]),
+									   &(proc->syncRepLinks),
+									   offsetof(PGPROC, syncRepLinks));
+	}
+
+	if (proc)
+		SHMQueueInsertAfter(&(proc->syncRepLinks), &(MyProc->syncRepLinks));
+	else
+		SHMQueueInsertAfter(&(WalSndCtl->SyncRepQueue[mode]), &(MyProc->syncRepLinks));
+}
+
+/*
+ * Acquire SyncRepLock and cancel any wait currently in progress.
+ */
+static void
+SyncRepCancelWait(void)
+{
+	LWLockAcquire(SyncRepLock, LW_EXCLUSIVE);
+	if (!SHMQueueIsDetached(&(MyProc->syncRepLinks)))
+		SHMQueueDelete(&(MyProc->syncRepLinks));
+	MyProc->syncRepState = SYNC_REP_NOT_WAITING;
+	LWLockRelease(SyncRepLock);
+}
+
+void
+SyncRepCleanupAtProcExit(void)
+{
+	/*
+	 * First check if we are removed from the queue without the lock to not
+	 * slow down backend exit.
+	 */
+	if (!SHMQueueIsDetached(&(MyProc->syncRepLinks)))
+	{
+		LWLockAcquire(SyncRepLock, LW_EXCLUSIVE);
+
+		/* maybe we have just been removed, so recheck */
+		if (!SHMQueueIsDetached(&(MyProc->syncRepLinks)))
+			SHMQueueDelete(&(MyProc->syncRepLinks));
+
+		LWLockRelease(SyncRepLock);
+	}
+}
+
+/*
+ * ===========================================================
+ * Synchronous Replication functions for wal sender processes
+ * ===========================================================
+ */
+
+/*
+ * Take any action required to initialise sync rep state from config
+ * data. Called at WALSender startup and after each SIGHUP.
+ */
+void
+SyncRepInitConfig(void)
+{
+	int			priority;
+
+	/*
+	 * Determine if we are a potential sync standby and remember the result
+	 * for handling replies from standby.
+	 */
+	priority = SyncRepGetStandbyPriority();
+	if (MyWalSnd->sync_standby_priority != priority)
+	{
+		SpinLockAcquire(&MyWalSnd->mutex);
+		MyWalSnd->sync_standby_priority = priority;
+		SpinLockRelease(&MyWalSnd->mutex);
+
+		ereport(DEBUG1,
+				(errmsg_internal("standby \"%s\" now has synchronous standby priority %u",
+								 application_name, priority)));
+	}
+}
+
+/*
+ * Update the LSNs on each queue based upon our latest state. This
+ * implements a simple policy of first-valid-sync-standby-releases-waiter.
+ *
+ * Other policies are possible, which would change what we do here and
+ * perhaps also which information we store as well.
+ */
+void
+SyncRepReleaseWaiters(void)
+{
+	volatile WalSndCtlData *walsndctl = WalSndCtl;
+	XLogRecPtr	writePtr;
+	XLogRecPtr	flushPtr;
+	XLogRecPtr	applyPtr;
+	bool		got_recptr;
+	bool		am_sync;
+	int			numwrite = 0;
+	int			numflush = 0;
+	int			numapply = 0;
+
+	/*
+	 * If this WALSender is serving a standby that is not on the list of
+	 * potential sync standbys then we have nothing to do. If we are still
+	 * starting up, still running base backup or the current flush position is
+	 * still invalid, then leave quickly also.  Streaming or stopping WAL
+	 * senders are allowed to release waiters.
+	 */
+	if (MyWalSnd->sync_standby_priority == 0 ||
+		(MyWalSnd->state != WALSNDSTATE_STREAMING &&
+		 MyWalSnd->state != WALSNDSTATE_STOPPING) ||
+		XLogRecPtrIsInvalid(MyWalSnd->flush))
+	{
+		announce_next_takeover = true;
+		return;
+	}
+
+	/*
+	 * We're a potential sync standby. Release waiters if there are enough
+	 * sync standbys and we are considered as sync.
+	 */
+	LWLockAcquire(SyncRepLock, LW_EXCLUSIVE);
+
+	/*
+	 * Check whether we are a sync standby or not, and calculate the synced
+	 * positions among all sync standbys.  (Note: although this step does not
+	 * of itself require holding SyncRepLock, it seems like a good idea to do
+	 * it after acquiring the lock.  This ensures that the WAL pointers we use
+	 * to release waiters are newer than any previous execution of this
+	 * routine used.)
+	 */
+	got_recptr = SyncRepGetSyncRecPtr(&writePtr, &flushPtr, &applyPtr, &am_sync);
+
+	/*
+	 * If we are managing a sync standby, though we weren't prior to this,
+	 * then announce we are now a sync standby.
+	 */
+	if (announce_next_takeover && am_sync)
+	{
+		announce_next_takeover = false;
+
+		if (SyncRepConfig->syncrep_method == SYNC_REP_PRIORITY)
+			ereport(LOG,
+					(errmsg("standby \"%s\" is now a synchronous standby with priority %u",
+							application_name, MyWalSnd->sync_standby_priority)));
+		else
+			ereport(LOG,
+					(errmsg("standby \"%s\" is now a candidate for quorum synchronous standby",
+							application_name)));
+	}
+
+	/*
+	 * If the number of sync standbys is less than requested or we aren't
+	 * managing a sync standby then just leave.
+	 */
+	if (!got_recptr || !am_sync)
+	{
+		LWLockRelease(SyncRepLock);
+		announce_next_takeover = !am_sync;
+		return;
+	}
+
+	/*
+	 * Set the lsn first so that when we wake backends they will release up to
+	 * this location.
+	 */
+	if (walsndctl->lsn[SYNC_REP_WAIT_WRITE] < writePtr)
+	{
+		walsndctl->lsn[SYNC_REP_WAIT_WRITE] = writePtr;
+		numwrite = SyncRepWakeQueue(false, SYNC_REP_WAIT_WRITE);
+	}
+	if (walsndctl->lsn[SYNC_REP_WAIT_FLUSH] < flushPtr)
+	{
+		walsndctl->lsn[SYNC_REP_WAIT_FLUSH] = flushPtr;
+		numflush = SyncRepWakeQueue(false, SYNC_REP_WAIT_FLUSH);
+	}
+	if (walsndctl->lsn[SYNC_REP_WAIT_APPLY] < applyPtr)
+	{
+		walsndctl->lsn[SYNC_REP_WAIT_APPLY] = applyPtr;
+		numapply = SyncRepWakeQueue(false, SYNC_REP_WAIT_APPLY);
+	}
+
+	LWLockRelease(SyncRepLock);
+
+	elog(DEBUG3, "released %d procs up to write %X/%X, %d procs up to flush %X/%X, %d procs up to apply %X/%X",
+		 numwrite, LSN_FORMAT_ARGS(writePtr),
+		 numflush, LSN_FORMAT_ARGS(flushPtr),
+		 numapply, LSN_FORMAT_ARGS(applyPtr));
+}
+
+/*
+ * Calculate the synced Write, Flush and Apply positions among sync standbys.
+ *
+ * Return false if the number of sync standbys is less than
+ * synchronous_standby_names specifies. Otherwise return true and
+ * store the positions into *writePtr, *flushPtr and *applyPtr.
+ *
+ * On return, *am_sync is set to true if this walsender is connecting to
+ * sync standby. Otherwise it's set to false.
+ */
+static bool
+SyncRepGetSyncRecPtr(XLogRecPtr *writePtr, XLogRecPtr *flushPtr,
+					 XLogRecPtr *applyPtr, bool *am_sync)
+{
+	SyncRepStandbyData *sync_standbys;
+	int			num_standbys;
+	int			i;
+
+	/* Initialize default results */
+	*writePtr = InvalidXLogRecPtr;
+	*flushPtr = InvalidXLogRecPtr;
+	*applyPtr = InvalidXLogRecPtr;
+	*am_sync = false;
+
+	/* Quick out if not even configured to be synchronous */
+	if (SyncRepConfig == NULL)
+		return false;
+
+	/* Get standbys that are considered as synchronous at this moment */
+	num_standbys = SyncRepGetCandidateStandbys(&sync_standbys);
+
+	/* Am I among the candidate sync standbys? */
+	for (i = 0; i < num_standbys; i++)
+	{
+		if (sync_standbys[i].is_me)
+		{
+			*am_sync = true;
+			break;
+		}
+	}
+
+	/*
+	 * Nothing more to do if we are not managing a sync standby or there are
+	 * not enough synchronous standbys.
+	 */
+	if (!(*am_sync) ||
+		num_standbys < SyncRepConfig->num_sync)
+	{
+		pfree(sync_standbys);
+		return false;
+	}
+
+	/*
+	 * In a priority-based sync replication, the synced positions are the
+	 * oldest ones among sync standbys. In a quorum-based, they are the Nth
+	 * latest ones.
+	 *
+	 * SyncRepGetNthLatestSyncRecPtr() also can calculate the oldest
+	 * positions. But we use SyncRepGetOldestSyncRecPtr() for that calculation
+	 * because it's a bit more efficient.
+	 *
+	 * XXX If the numbers of current and requested sync standbys are the same,
+	 * we can use SyncRepGetOldestSyncRecPtr() to calculate the synced
+	 * positions even in a quorum-based sync replication.
+	 */
+	if (SyncRepConfig->syncrep_method == SYNC_REP_PRIORITY)
+	{
+		SyncRepGetOldestSyncRecPtr(writePtr, flushPtr, applyPtr,
+								   sync_standbys, num_standbys);
+	}
+	else
+	{
+		SyncRepGetNthLatestSyncRecPtr(writePtr, flushPtr, applyPtr,
+									  sync_standbys, num_standbys,
+									  SyncRepConfig->num_sync);
+	}
+
+	pfree(sync_standbys);
+	return true;
+}
+
+/*
+ * Calculate the oldest Write, Flush and Apply positions among sync standbys.
+ */
+static void
+SyncRepGetOldestSyncRecPtr(XLogRecPtr *writePtr,
+						   XLogRecPtr *flushPtr,
+						   XLogRecPtr *applyPtr,
+						   SyncRepStandbyData *sync_standbys,
+						   int num_standbys)
+{
+	int			i;
+
+	/*
+	 * Scan through all sync standbys and calculate the oldest Write, Flush
+	 * and Apply positions.  We assume *writePtr et al were initialized to
+	 * InvalidXLogRecPtr.
+	 */
+	for (i = 0; i < num_standbys; i++)
+	{
+		XLogRecPtr	write = sync_standbys[i].write;
+		XLogRecPtr	flush = sync_standbys[i].flush;
+		XLogRecPtr	apply = sync_standbys[i].apply;
+
+		if (XLogRecPtrIsInvalid(*writePtr) || *writePtr > write)
+			*writePtr = write;
+		if (XLogRecPtrIsInvalid(*flushPtr) || *flushPtr > flush)
+			*flushPtr = flush;
+		if (XLogRecPtrIsInvalid(*applyPtr) || *applyPtr > apply)
+			*applyPtr = apply;
+	}
+}
+
+/*
+ * Calculate the Nth latest Write, Flush and Apply positions among sync
+ * standbys.
+ */
+static void
+SyncRepGetNthLatestSyncRecPtr(XLogRecPtr *writePtr,
+							  XLogRecPtr *flushPtr,
+							  XLogRecPtr *applyPtr,
+							  SyncRepStandbyData *sync_standbys,
+							  int num_standbys,
+							  uint8 nth)
+{
+	XLogRecPtr *write_array;
+	XLogRecPtr *flush_array;
+	XLogRecPtr *apply_array;
+	int			i;
+
+	/* Should have enough candidates, or somebody messed up */
+	Assert(nth > 0 && nth <= num_standbys);
+
+	write_array = (XLogRecPtr *) palloc(sizeof(XLogRecPtr) * num_standbys);
+	flush_array = (XLogRecPtr *) palloc(sizeof(XLogRecPtr) * num_standbys);
+	apply_array = (XLogRecPtr *) palloc(sizeof(XLogRecPtr) * num_standbys);
+
+	for (i = 0; i < num_standbys; i++)
+	{
+		write_array[i] = sync_standbys[i].write;
+		flush_array[i] = sync_standbys[i].flush;
+		apply_array[i] = sync_standbys[i].apply;
+	}
+
+	/* Sort each array in descending order */
+	qsort(write_array, num_standbys, sizeof(XLogRecPtr), cmp_lsn);
+	qsort(flush_array, num_standbys, sizeof(XLogRecPtr), cmp_lsn);
+	qsort(apply_array, num_standbys, sizeof(XLogRecPtr), cmp_lsn);
+
+	/* Get Nth latest Write, Flush, Apply positions */
+	*writePtr = write_array[nth - 1];
+	*flushPtr = flush_array[nth - 1];
+	*applyPtr = apply_array[nth - 1];
+
+	pfree(write_array);
+	pfree(flush_array);
+	pfree(apply_array);
+}
+
+/*
+ * Compare lsn in order to sort array in descending order.
+ */
+static int
+cmp_lsn(const void *a, const void *b)
+{
+	XLogRecPtr	lsn1 = *((const XLogRecPtr *) a);
+	XLogRecPtr	lsn2 = *((const XLogRecPtr *) b);
+
+	if (lsn1 > lsn2)
+		return -1;
+	else if (lsn1 == lsn2)
+		return 0;
+	else
+		return 1;
+}
+
+/*
+ * Return data about walsenders that are candidates to be sync standbys.
+ *
+ * *standbys is set to a palloc'd array of structs of per-walsender data,
+ * and the number of valid entries (candidate sync senders) is returned.
+ * (This might be more or fewer than num_sync; caller must check.)
+ */
+int
+SyncRepGetCandidateStandbys(SyncRepStandbyData **standbys)
+{
+	int			i;
+	int			n;
+
+	/* Create result array */
+	*standbys = (SyncRepStandbyData *)
+		palloc(max_wal_senders * sizeof(SyncRepStandbyData));
+
+	/* Quick exit if sync replication is not requested */
+	if (SyncRepConfig == NULL)
+		return 0;
+
+	/* Collect raw data from shared memory */
+	n = 0;
+	for (i = 0; i < max_wal_senders; i++)
+	{
+		volatile WalSnd *walsnd;	/* Use volatile pointer to prevent code
+									 * rearrangement */
+		SyncRepStandbyData *stby;
+		WalSndState state;		/* not included in SyncRepStandbyData */
+
+		walsnd = &WalSndCtl->walsnds[i];
+		stby = *standbys + n;
+
+		SpinLockAcquire(&walsnd->mutex);
+		stby->pid = walsnd->pid;
+		state = walsnd->state;
+		stby->write = walsnd->write;
+		stby->flush = walsnd->flush;
+		stby->apply = walsnd->apply;
+		stby->sync_standby_priority = walsnd->sync_standby_priority;
+		SpinLockRelease(&walsnd->mutex);
+
+		/* Must be active */
+		if (stby->pid == 0)
+			continue;
+
+		/* Must be streaming or stopping */
+		if (state != WALSNDSTATE_STREAMING &&
+			state != WALSNDSTATE_STOPPING)
+			continue;
+
+		/* Must be synchronous */
+		if (stby->sync_standby_priority == 0)
+			continue;
+
+		/* Must have a valid flush position */
+		if (XLogRecPtrIsInvalid(stby->flush))
+			continue;
+
+		/* OK, it's a candidate */
+		stby->walsnd_index = i;
+		stby->is_me = (walsnd == MyWalSnd);
+		n++;
+	}
+
+	/*
+	 * In quorum mode, we return all the candidates.  In priority mode, if we
+	 * have too many candidates then return only the num_sync ones of highest
+	 * priority.
+	 */
+	if (SyncRepConfig->syncrep_method == SYNC_REP_PRIORITY &&
+		n > SyncRepConfig->num_sync)
+	{
+		/* Sort by priority ... */
+		qsort(*standbys, n, sizeof(SyncRepStandbyData),
+			  standby_priority_comparator);
+		/* ... then report just the first num_sync ones */
+		n = SyncRepConfig->num_sync;
+	}
+
+	return n;
+}
+
+/*
+ * qsort comparator to sort SyncRepStandbyData entries by priority
+ */
+static int
+standby_priority_comparator(const void *a, const void *b)
+{
+	const SyncRepStandbyData *sa = (const SyncRepStandbyData *) a;
+	const SyncRepStandbyData *sb = (const SyncRepStandbyData *) b;
+
+	/* First, sort by increasing priority value */
+	if (sa->sync_standby_priority != sb->sync_standby_priority)
+		return sa->sync_standby_priority - sb->sync_standby_priority;
+
+	/*
+	 * We might have equal priority values; arbitrarily break ties by position
+	 * in the WALSnd array.  (This is utterly bogus, since that is arrival
+	 * order dependent, but there are regression tests that rely on it.)
+	 */
+	return sa->walsnd_index - sb->walsnd_index;
+}
+
+
+/*
+ * Check if we are in the list of sync standbys, and if so, determine
+ * priority sequence. Return priority if set, or zero to indicate that
+ * we are not a potential sync standby.
+ *
+ * Compare the parameter SyncRepStandbyNames against the application_name
+ * for this WALSender, or allow any name if we find a wildcard "*".
+ */
+static int
+SyncRepGetStandbyPriority(void)
+{
+	const char *standby_name;
+	int			priority;
+	bool		found = false;
+
+	/*
+	 * Since synchronous cascade replication is not allowed, we always set the
+	 * priority of cascading walsender to zero.
+	 */
+	if (am_cascading_walsender)
+		return 0;
+
+	if (!SyncStandbysDefined() || SyncRepConfig == NULL)
+		return 0;
+
+	standby_name = SyncRepConfig->member_names;
+	for (priority = 1; priority <= SyncRepConfig->nmembers; priority++)
+	{
+		if (pg_strcasecmp(standby_name, application_name) == 0 ||
+			strcmp(standby_name, "*") == 0)
+		{
+			found = true;
+			break;
+		}
+		standby_name += strlen(standby_name) + 1;
+	}
+
+	if (!found)
+		return 0;
+
+	/*
+	 * In quorum-based sync replication, all the standbys in the list have the
+	 * same priority, one.
+	 */
+	return (SyncRepConfig->syncrep_method == SYNC_REP_PRIORITY) ? priority : 1;
+}
+
+/*
+ * Walk the specified queue from head.  Set the state of any backends that
+ * need to be woken, remove them from the queue, and then wake them.
+ * Pass all = true to wake whole queue; otherwise, just wake up to
+ * the walsender's LSN.
+ *
+ * The caller must hold SyncRepLock in exclusive mode.
+ */
+static int
+SyncRepWakeQueue(bool all, int mode)
+{
+	volatile WalSndCtlData *walsndctl = WalSndCtl;
+	PGPROC	   *proc = NULL;
+	PGPROC	   *thisproc = NULL;
+	int			numprocs = 0;
+
+	Assert(mode >= 0 && mode < NUM_SYNC_REP_WAIT_MODE);
+	Assert(LWLockHeldByMeInMode(SyncRepLock, LW_EXCLUSIVE));
+	Assert(SyncRepQueueIsOrderedByLSN(mode));
+
+	proc = (PGPROC *) SHMQueueNext(&(WalSndCtl->SyncRepQueue[mode]),
+								   &(WalSndCtl->SyncRepQueue[mode]),
+								   offsetof(PGPROC, syncRepLinks));
+
+	while (proc)
+	{
+		/*
+		 * Assume the queue is ordered by LSN
+		 */
+		if (!all && walsndctl->lsn[mode] < proc->waitLSN)
+			return numprocs;
+
+		/*
+		 * Move to next proc, so we can delete thisproc from the queue.
+		 * thisproc is valid, proc may be NULL after this.
+		 */
+		thisproc = proc;
+		proc = (PGPROC *) SHMQueueNext(&(WalSndCtl->SyncRepQueue[mode]),
+									   &(proc->syncRepLinks),
+									   offsetof(PGPROC, syncRepLinks));
+
+		/*
+		 * Remove thisproc from queue.
+		 */
+		SHMQueueDelete(&(thisproc->syncRepLinks));
+
+		/*
+		 * SyncRepWaitForLSN() reads syncRepState without holding the lock, so
+		 * make sure that it sees the queue link being removed before the
+		 * syncRepState change.
+		 */
+		pg_write_barrier();
+
+		/*
+		 * Set state to complete; see SyncRepWaitForLSN() for discussion of
+		 * the various states.
+		 */
+		thisproc->syncRepState = SYNC_REP_WAIT_COMPLETE;
+
+		/*
+		 * Wake only when we have set state and removed from queue.
+		 */
+		SetLatch(&(thisproc->procLatch));
+
+		numprocs++;
+	}
+
+	return numprocs;
+}
+
+/*
+ * The checkpointer calls this as needed to update the shared
+ * sync_standbys_defined flag, so that backends don't remain permanently wedged
+ * if synchronous_standby_names is unset.  It's safe to check the current value
+ * without the lock, because it's only ever updated by one process.  But we
+ * must take the lock to change it.
+ */
+void
+SyncRepUpdateSyncStandbysDefined(void)
+{
+	bool		sync_standbys_defined = SyncStandbysDefined();
+
+	if (sync_standbys_defined != WalSndCtl->sync_standbys_defined)
+	{
+		LWLockAcquire(SyncRepLock, LW_EXCLUSIVE);
+
+		/*
+		 * If synchronous_standby_names has been reset to empty, it's futile
+		 * for backends to continue waiting.  Since the user no longer wants
+		 * synchronous replication, we'd better wake them up.
+		 */
+		if (!sync_standbys_defined)
+		{
+			int			i;
+
+			for (i = 0; i < NUM_SYNC_REP_WAIT_MODE; i++)
+				SyncRepWakeQueue(true, i);
+		}
+
+		/*
+		 * Only allow people to join the queue when there are synchronous
+		 * standbys defined.  Without this interlock, there's a race
+		 * condition: we might wake up all the current waiters; then, some
+		 * backend that hasn't yet reloaded its config might go to sleep on
+		 * the queue (and never wake up).  This prevents that.
+		 */
+		WalSndCtl->sync_standbys_defined = sync_standbys_defined;
+
+		LWLockRelease(SyncRepLock);
+	}
+}
+
+#ifdef USE_ASSERT_CHECKING
+static bool
+SyncRepQueueIsOrderedByLSN(int mode)
+{
+	PGPROC	   *proc = NULL;
+	XLogRecPtr	lastLSN;
+
+	Assert(mode >= 0 && mode < NUM_SYNC_REP_WAIT_MODE);
+
+	lastLSN = 0;
+
+	proc = (PGPROC *) SHMQueueNext(&(WalSndCtl->SyncRepQueue[mode]),
+								   &(WalSndCtl->SyncRepQueue[mode]),
+								   offsetof(PGPROC, syncRepLinks));
+
+	while (proc)
+	{
+		/*
+		 * Check the queue is ordered by LSN and that multiple procs don't
+		 * have matching LSNs
+		 */
+		if (proc->waitLSN <= lastLSN)
+			return false;
+
+		lastLSN = proc->waitLSN;
+
+		proc = (PGPROC *) SHMQueueNext(&(WalSndCtl->SyncRepQueue[mode]),
+									   &(proc->syncRepLinks),
+									   offsetof(PGPROC, syncRepLinks));
+	}
+
+	return true;
+}
+#endif
+
+/*
+ * ===========================================================
+ * Synchronous Replication functions executed by any process
+ * ===========================================================
+ */
+
+bool
+check_synchronous_standby_names(char **newval, void **extra, GucSource source)
+{
+	if (*newval != NULL && (*newval)[0] != '\0')
+	{
+		int			parse_rc;
+		SyncRepConfigData *pconf;
+
+		/* Reset communication variables to ensure a fresh start */
+		syncrep_parse_result = NULL;
+		syncrep_parse_error_msg = NULL;
+
+		/* Parse the synchronous_standby_names string */
+		syncrep_scanner_init(*newval);
+		parse_rc = syncrep_yyparse();
+		syncrep_scanner_finish();
+
+		if (parse_rc != 0 || syncrep_parse_result == NULL)
+		{
+			GUC_check_errcode(ERRCODE_SYNTAX_ERROR);
+			if (syncrep_parse_error_msg)
+				GUC_check_errdetail("%s", syncrep_parse_error_msg);
+			else
+				GUC_check_errdetail("synchronous_standby_names parser failed");
+			return false;
+		}
+
+		if (syncrep_parse_result->num_sync <= 0)
+		{
+			GUC_check_errmsg("number of synchronous standbys (%d) must be greater than zero",
+							 syncrep_parse_result->num_sync);
+			return false;
+		}
+
+		/* GUC extra value must be malloc'd, not palloc'd */
+		pconf = (SyncRepConfigData *)
+			malloc(syncrep_parse_result->config_size);
+		if (pconf == NULL)
+			return false;
+		memcpy(pconf, syncrep_parse_result, syncrep_parse_result->config_size);
+
+		*extra = (void *) pconf;
+
+		/*
+		 * We need not explicitly clean up syncrep_parse_result.  It, and any
+		 * other cruft generated during parsing, will be freed when the
+		 * current memory context is deleted.  (This code is generally run in
+		 * a short-lived context used for config file processing, so that will
+		 * not be very long.)
+		 */
+	}
+	else
+		*extra = NULL;
+
+	return true;
+}
+
+void
+assign_synchronous_standby_names(const char *newval, void *extra)
+{
+	SyncRepConfig = (SyncRepConfigData *) extra;
+}
+
+void
+assign_synchronous_commit(int newval, void *extra)
+{
+	switch (newval)
+	{
+		case SYNCHRONOUS_COMMIT_REMOTE_WRITE:
+			SyncRepWaitMode = SYNC_REP_WAIT_WRITE;
+			break;
+		case SYNCHRONOUS_COMMIT_REMOTE_FLUSH:
+			SyncRepWaitMode = SYNC_REP_WAIT_FLUSH;
+			break;
+		case SYNCHRONOUS_COMMIT_REMOTE_APPLY:
+			SyncRepWaitMode = SYNC_REP_WAIT_APPLY;
+			break;
+		default:
+			SyncRepWaitMode = SYNC_REP_NO_WAIT;
+			break;
+	}
+}
diff --git a/src/backend/replication/syncrep_gram.c b/src/backend/replication/syncrep_gram.c
new file mode 100644
index 0000000..0359e7c
--- /dev/null
+++ b/src/backend/replication/syncrep_gram.c
@@ -0,0 +1,1461 @@
+/* A Bison parser, made by GNU Bison 3.7.5.  */
+
+/* Bison implementation for Yacc-like parsers in C
+
+   Copyright (C) 1984, 1989-1990, 2000-2015, 2018-2021 Free Software Foundation,
+   Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* As a special exception, you may create a larger work that contains
+   part or all of the Bison parser skeleton and distribute that work
+   under terms of your choice, so long as that work isn't itself a
+   parser generator using the skeleton or a modified version thereof
+   as a parser skeleton.  Alternatively, if you modify or redistribute
+   the parser skeleton itself, you may (at your option) remove this
+   special exception, which will cause the skeleton and the resulting
+   Bison output files to be licensed under the GNU General Public
+   License without this special exception.
+
+   This special exception was added by the Free Software Foundation in
+   version 2.2 of Bison.  */
+
+/* C LALR(1) parser skeleton written by Richard Stallman, by
+   simplifying the original so-called "semantic" parser.  */
+
+/* DO NOT RELY ON FEATURES THAT ARE NOT DOCUMENTED in the manual,
+   especially those whose name start with YY_ or yy_.  They are
+   private implementation details that can be changed or removed.  */
+
+/* All symbols defined below should begin with yy or YY, to avoid
+   infringing on user name space.  This should be done even for local
+   variables, as they might otherwise be expanded by user macros.
+   There are some unavoidable exceptions within include files to
+   define necessary library symbols; they are noted "INFRINGES ON
+   USER NAME SPACE" below.  */
+
+/* Identify Bison output, and Bison version.  */
+#define YYBISON 30705
+
+/* Bison version string.  */
+#define YYBISON_VERSION "3.7.5"
+
+/* Skeleton name.  */
+#define YYSKELETON_NAME "yacc.c"
+
+/* Pure parsers.  */
+#define YYPURE 0
+
+/* Push parsers.  */
+#define YYPUSH 0
+
+/* Pull parsers.  */
+#define YYPULL 1
+
+
+/* Substitute the variable and function names.  */
+#define yyparse         syncrep_yyparse
+#define yylex           syncrep_yylex
+#define yyerror         syncrep_yyerror
+#define yydebug         syncrep_yydebug
+#define yynerrs         syncrep_yynerrs
+#define yylval          syncrep_yylval
+#define yychar          syncrep_yychar
+
+/* First part of user prologue.  */
+#line 1 "syncrep_gram.y"
+
+/*-------------------------------------------------------------------------
+ *
+ * syncrep_gram.y				- Parser for synchronous_standby_names
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/syncrep_gram.y
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "replication/syncrep.h"
+
+/* Result of parsing is returned in one of these two variables */
+SyncRepConfigData *syncrep_parse_result;
+char	   *syncrep_parse_error_msg;
+
+static SyncRepConfigData *create_syncrep_config(const char *num_sync,
+					List *members, uint8 syncrep_method);
+
+/*
+ * Bison doesn't allocate anything that needs to live across parser calls,
+ * so we can easily have it use palloc instead of malloc.  This prevents
+ * memory leaks if we error out during parsing.  Note this only works with
+ * bison >= 2.0.  However, in bison 1.875 the default is to use alloca()
+ * if possible, so there's not really much problem anyhow, at least if
+ * you're building with gcc.
+ */
+#define YYMALLOC palloc
+#define YYFREE   pfree
+
+
+#line 116 "syncrep_gram.c"
+
+# ifndef YY_CAST
+#  ifdef __cplusplus
+#   define YY_CAST(Type, Val) static_cast<Type> (Val)
+#   define YY_REINTERPRET_CAST(Type, Val) reinterpret_cast<Type> (Val)
+#  else
+#   define YY_CAST(Type, Val) ((Type) (Val))
+#   define YY_REINTERPRET_CAST(Type, Val) ((Type) (Val))
+#  endif
+# endif
+# ifndef YY_NULLPTR
+#  if defined __cplusplus
+#   if 201103L <= __cplusplus
+#    define YY_NULLPTR nullptr
+#   else
+#    define YY_NULLPTR 0
+#   endif
+#  else
+#   define YY_NULLPTR ((void*)0)
+#  endif
+# endif
+
+
+/* Debug traces.  */
+#ifndef YYDEBUG
+# define YYDEBUG 0
+#endif
+#if YYDEBUG
+extern int syncrep_yydebug;
+#endif
+
+/* Token kinds.  */
+#ifndef YYTOKENTYPE
+# define YYTOKENTYPE
+  enum yytokentype
+  {
+    YYEMPTY = -2,
+    YYEOF = 0,                     /* "end of file"  */
+    YYerror = 256,                 /* error  */
+    YYUNDEF = 257,                 /* "invalid token"  */
+    NAME = 258,                    /* NAME  */
+    NUM = 259,                     /* NUM  */
+    JUNK = 260,                    /* JUNK  */
+    ANY = 261,                     /* ANY  */
+    FIRST = 262                    /* FIRST  */
+  };
+  typedef enum yytokentype yytoken_kind_t;
+#endif
+
+/* Value type.  */
+#if ! defined YYSTYPE && ! defined YYSTYPE_IS_DECLARED
+union YYSTYPE
+{
+#line 43 "syncrep_gram.y"
+
+	char	   *str;
+	List	   *list;
+	SyncRepConfigData *config;
+
+#line 176 "syncrep_gram.c"
+
+};
+typedef union YYSTYPE YYSTYPE;
+# define YYSTYPE_IS_TRIVIAL 1
+# define YYSTYPE_IS_DECLARED 1
+#endif
+
+
+extern YYSTYPE syncrep_yylval;
+
+int syncrep_yyparse (void);
+
+
+/* Symbol kind.  */
+enum yysymbol_kind_t
+{
+  YYSYMBOL_YYEMPTY = -2,
+  YYSYMBOL_YYEOF = 0,                      /* "end of file"  */
+  YYSYMBOL_YYerror = 1,                    /* error  */
+  YYSYMBOL_YYUNDEF = 2,                    /* "invalid token"  */
+  YYSYMBOL_NAME = 3,                       /* NAME  */
+  YYSYMBOL_NUM = 4,                        /* NUM  */
+  YYSYMBOL_JUNK = 5,                       /* JUNK  */
+  YYSYMBOL_ANY = 6,                        /* ANY  */
+  YYSYMBOL_FIRST = 7,                      /* FIRST  */
+  YYSYMBOL_8_ = 8,                         /* '('  */
+  YYSYMBOL_9_ = 9,                         /* ')'  */
+  YYSYMBOL_10_ = 10,                       /* ','  */
+  YYSYMBOL_YYACCEPT = 11,                  /* $accept  */
+  YYSYMBOL_result = 12,                    /* result  */
+  YYSYMBOL_standby_config = 13,            /* standby_config  */
+  YYSYMBOL_standby_list = 14,              /* standby_list  */
+  YYSYMBOL_standby_name = 15               /* standby_name  */
+};
+typedef enum yysymbol_kind_t yysymbol_kind_t;
+
+
+
+
+#ifdef short
+# undef short
+#endif
+
+/* On compilers that do not define __PTRDIFF_MAX__ etc., make sure
+   <limits.h> and (if available) <stdint.h> are included
+   so that the code can choose integer types of a good width.  */
+
+#ifndef __PTRDIFF_MAX__
+# include <limits.h> /* INFRINGES ON USER NAME SPACE */
+# if defined __STDC_VERSION__ && 199901 <= __STDC_VERSION__
+#  include <stdint.h> /* INFRINGES ON USER NAME SPACE */
+#  define YY_STDINT_H
+# endif
+#endif
+
+/* Narrow types that promote to a signed type and that can represent a
+   signed or unsigned integer of at least N bits.  In tables they can
+   save space and decrease cache pressure.  Promoting to a signed type
+   helps avoid bugs in integer arithmetic.  */
+
+#ifdef __INT_LEAST8_MAX__
+typedef __INT_LEAST8_TYPE__ yytype_int8;
+#elif defined YY_STDINT_H
+typedef int_least8_t yytype_int8;
+#else
+typedef signed char yytype_int8;
+#endif
+
+#ifdef __INT_LEAST16_MAX__
+typedef __INT_LEAST16_TYPE__ yytype_int16;
+#elif defined YY_STDINT_H
+typedef int_least16_t yytype_int16;
+#else
+typedef short yytype_int16;
+#endif
+
+/* Work around bug in HP-UX 11.23, which defines these macros
+   incorrectly for preprocessor constants.  This workaround can likely
+   be removed in 2023, as HPE has promised support for HP-UX 11.23
+   (aka HP-UX 11i v2) only through the end of 2022; see Table 2 of
+   <https://h20195.www2.hpe.com/V2/getpdf.aspx/4AA4-7673ENW.pdf>.  */
+#ifdef __hpux
+# undef UINT_LEAST8_MAX
+# undef UINT_LEAST16_MAX
+# define UINT_LEAST8_MAX 255
+# define UINT_LEAST16_MAX 65535
+#endif
+
+#if defined __UINT_LEAST8_MAX__ && __UINT_LEAST8_MAX__ <= __INT_MAX__
+typedef __UINT_LEAST8_TYPE__ yytype_uint8;
+#elif (!defined __UINT_LEAST8_MAX__ && defined YY_STDINT_H \
+       && UINT_LEAST8_MAX <= INT_MAX)
+typedef uint_least8_t yytype_uint8;
+#elif !defined __UINT_LEAST8_MAX__ && UCHAR_MAX <= INT_MAX
+typedef unsigned char yytype_uint8;
+#else
+typedef short yytype_uint8;
+#endif
+
+#if defined __UINT_LEAST16_MAX__ && __UINT_LEAST16_MAX__ <= __INT_MAX__
+typedef __UINT_LEAST16_TYPE__ yytype_uint16;
+#elif (!defined __UINT_LEAST16_MAX__ && defined YY_STDINT_H \
+       && UINT_LEAST16_MAX <= INT_MAX)
+typedef uint_least16_t yytype_uint16;
+#elif !defined __UINT_LEAST16_MAX__ && USHRT_MAX <= INT_MAX
+typedef unsigned short yytype_uint16;
+#else
+typedef int yytype_uint16;
+#endif
+
+#ifndef YYPTRDIFF_T
+# if defined __PTRDIFF_TYPE__ && defined __PTRDIFF_MAX__
+#  define YYPTRDIFF_T __PTRDIFF_TYPE__
+#  define YYPTRDIFF_MAXIMUM __PTRDIFF_MAX__
+# elif defined PTRDIFF_MAX
+#  ifndef ptrdiff_t
+#   include <stddef.h> /* INFRINGES ON USER NAME SPACE */
+#  endif
+#  define YYPTRDIFF_T ptrdiff_t
+#  define YYPTRDIFF_MAXIMUM PTRDIFF_MAX
+# else
+#  define YYPTRDIFF_T long
+#  define YYPTRDIFF_MAXIMUM LONG_MAX
+# endif
+#endif
+
+#ifndef YYSIZE_T
+# ifdef __SIZE_TYPE__
+#  define YYSIZE_T __SIZE_TYPE__
+# elif defined size_t
+#  define YYSIZE_T size_t
+# elif defined __STDC_VERSION__ && 199901 <= __STDC_VERSION__
+#  include <stddef.h> /* INFRINGES ON USER NAME SPACE */
+#  define YYSIZE_T size_t
+# else
+#  define YYSIZE_T unsigned
+# endif
+#endif
+
+#define YYSIZE_MAXIMUM                                  \
+  YY_CAST (YYPTRDIFF_T,                                 \
+           (YYPTRDIFF_MAXIMUM < YY_CAST (YYSIZE_T, -1)  \
+            ? YYPTRDIFF_MAXIMUM                         \
+            : YY_CAST (YYSIZE_T, -1)))
+
+#define YYSIZEOF(X) YY_CAST (YYPTRDIFF_T, sizeof (X))
+
+
+/* Stored state numbers (used for stacks). */
+typedef yytype_int8 yy_state_t;
+
+/* State numbers in computations.  */
+typedef int yy_state_fast_t;
+
+#ifndef YY_
+# if defined YYENABLE_NLS && YYENABLE_NLS
+#  if ENABLE_NLS
+#   include <libintl.h> /* INFRINGES ON USER NAME SPACE */
+#   define YY_(Msgid) dgettext ("bison-runtime", Msgid)
+#  endif
+# endif
+# ifndef YY_
+#  define YY_(Msgid) Msgid
+# endif
+#endif
+
+
+#ifndef YY_ATTRIBUTE_PURE
+# if defined __GNUC__ && 2 < __GNUC__ + (96 <= __GNUC_MINOR__)
+#  define YY_ATTRIBUTE_PURE __attribute__ ((__pure__))
+# else
+#  define YY_ATTRIBUTE_PURE
+# endif
+#endif
+
+#ifndef YY_ATTRIBUTE_UNUSED
+# if defined __GNUC__ && 2 < __GNUC__ + (7 <= __GNUC_MINOR__)
+#  define YY_ATTRIBUTE_UNUSED __attribute__ ((__unused__))
+# else
+#  define YY_ATTRIBUTE_UNUSED
+# endif
+#endif
+
+/* Suppress unused-variable warnings by "using" E.  */
+#if ! defined lint || defined __GNUC__
+# define YY_USE(E) ((void) (E))
+#else
+# define YY_USE(E) /* empty */
+#endif
+
+#if defined __GNUC__ && ! defined __ICC && 407 <= __GNUC__ * 100 + __GNUC_MINOR__
+/* Suppress an incorrect diagnostic about yylval being uninitialized.  */
+# define YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN                            \
+    _Pragma ("GCC diagnostic push")                                     \
+    _Pragma ("GCC diagnostic ignored \"-Wuninitialized\"")              \
+    _Pragma ("GCC diagnostic ignored \"-Wmaybe-uninitialized\"")
+# define YY_IGNORE_MAYBE_UNINITIALIZED_END      \
+    _Pragma ("GCC diagnostic pop")
+#else
+# define YY_INITIAL_VALUE(Value) Value
+#endif
+#ifndef YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN
+# define YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN
+# define YY_IGNORE_MAYBE_UNINITIALIZED_END
+#endif
+#ifndef YY_INITIAL_VALUE
+# define YY_INITIAL_VALUE(Value) /* Nothing. */
+#endif
+
+#if defined __cplusplus && defined __GNUC__ && ! defined __ICC && 6 <= __GNUC__
+# define YY_IGNORE_USELESS_CAST_BEGIN                          \
+    _Pragma ("GCC diagnostic push")                            \
+    _Pragma ("GCC diagnostic ignored \"-Wuseless-cast\"")
+# define YY_IGNORE_USELESS_CAST_END            \
+    _Pragma ("GCC diagnostic pop")
+#endif
+#ifndef YY_IGNORE_USELESS_CAST_BEGIN
+# define YY_IGNORE_USELESS_CAST_BEGIN
+# define YY_IGNORE_USELESS_CAST_END
+#endif
+
+
+#define YY_ASSERT(E) ((void) (0 && (E)))
+
+#if !defined yyoverflow
+
+/* The parser invokes alloca or malloc; define the necessary symbols.  */
+
+# ifdef YYSTACK_USE_ALLOCA
+#  if YYSTACK_USE_ALLOCA
+#   ifdef __GNUC__
+#    define YYSTACK_ALLOC __builtin_alloca
+#   elif defined __BUILTIN_VA_ARG_INCR
+#    include <alloca.h> /* INFRINGES ON USER NAME SPACE */
+#   elif defined _AIX
+#    define YYSTACK_ALLOC __alloca
+#   elif defined _MSC_VER
+#    include <malloc.h> /* INFRINGES ON USER NAME SPACE */
+#    define alloca _alloca
+#   else
+#    define YYSTACK_ALLOC alloca
+#    if ! defined _ALLOCA_H && ! defined EXIT_SUCCESS
+#     include <stdlib.h> /* INFRINGES ON USER NAME SPACE */
+      /* Use EXIT_SUCCESS as a witness for stdlib.h.  */
+#     ifndef EXIT_SUCCESS
+#      define EXIT_SUCCESS 0
+#     endif
+#    endif
+#   endif
+#  endif
+# endif
+
+# ifdef YYSTACK_ALLOC
+   /* Pacify GCC's 'empty if-body' warning.  */
+#  define YYSTACK_FREE(Ptr) do { /* empty */; } while (0)
+#  ifndef YYSTACK_ALLOC_MAXIMUM
+    /* The OS might guarantee only one guard page at the bottom of the stack,
+       and a page size can be as small as 4096 bytes.  So we cannot safely
+       invoke alloca (N) if N exceeds 4096.  Use a slightly smaller number
+       to allow for a few compiler-allocated temporary stack slots.  */
+#   define YYSTACK_ALLOC_MAXIMUM 4032 /* reasonable circa 2006 */
+#  endif
+# else
+#  define YYSTACK_ALLOC YYMALLOC
+#  define YYSTACK_FREE YYFREE
+#  ifndef YYSTACK_ALLOC_MAXIMUM
+#   define YYSTACK_ALLOC_MAXIMUM YYSIZE_MAXIMUM
+#  endif
+#  if (defined __cplusplus && ! defined EXIT_SUCCESS \
+       && ! ((defined YYMALLOC || defined malloc) \
+             && (defined YYFREE || defined free)))
+#   include <stdlib.h> /* INFRINGES ON USER NAME SPACE */
+#   ifndef EXIT_SUCCESS
+#    define EXIT_SUCCESS 0
+#   endif
+#  endif
+#  ifndef YYMALLOC
+#   define YYMALLOC malloc
+#   if ! defined malloc && ! defined EXIT_SUCCESS
+void *malloc (YYSIZE_T); /* INFRINGES ON USER NAME SPACE */
+#   endif
+#  endif
+#  ifndef YYFREE
+#   define YYFREE free
+#   if ! defined free && ! defined EXIT_SUCCESS
+void free (void *); /* INFRINGES ON USER NAME SPACE */
+#   endif
+#  endif
+# endif
+#endif /* !defined yyoverflow */
+
+#if (! defined yyoverflow \
+     && (! defined __cplusplus \
+         || (defined YYSTYPE_IS_TRIVIAL && YYSTYPE_IS_TRIVIAL)))
+
+/* A type that is properly aligned for any stack member.  */
+union yyalloc
+{
+  yy_state_t yyss_alloc;
+  YYSTYPE yyvs_alloc;
+};
+
+/* The size of the maximum gap between one aligned stack and the next.  */
+# define YYSTACK_GAP_MAXIMUM (YYSIZEOF (union yyalloc) - 1)
+
+/* The size of an array large to enough to hold all stacks, each with
+   N elements.  */
+# define YYSTACK_BYTES(N) \
+     ((N) * (YYSIZEOF (yy_state_t) + YYSIZEOF (YYSTYPE)) \
+      + YYSTACK_GAP_MAXIMUM)
+
+# define YYCOPY_NEEDED 1
+
+/* Relocate STACK from its old location to the new one.  The
+   local variables YYSIZE and YYSTACKSIZE give the old and new number of
+   elements in the stack, and YYPTR gives the new location of the
+   stack.  Advance YYPTR to a properly aligned location for the next
+   stack.  */
+# define YYSTACK_RELOCATE(Stack_alloc, Stack)                           \
+    do                                                                  \
+      {                                                                 \
+        YYPTRDIFF_T yynewbytes;                                         \
+        YYCOPY (&yyptr->Stack_alloc, Stack, yysize);                    \
+        Stack = &yyptr->Stack_alloc;                                    \
+        yynewbytes = yystacksize * YYSIZEOF (*Stack) + YYSTACK_GAP_MAXIMUM; \
+        yyptr += yynewbytes / YYSIZEOF (*yyptr);                        \
+      }                                                                 \
+    while (0)
+
+#endif
+
+#if defined YYCOPY_NEEDED && YYCOPY_NEEDED
+/* Copy COUNT objects from SRC to DST.  The source and destination do
+   not overlap.  */
+# ifndef YYCOPY
+#  if defined __GNUC__ && 1 < __GNUC__
+#   define YYCOPY(Dst, Src, Count) \
+      __builtin_memcpy (Dst, Src, YY_CAST (YYSIZE_T, (Count)) * sizeof (*(Src)))
+#  else
+#   define YYCOPY(Dst, Src, Count)              \
+      do                                        \
+        {                                       \
+          YYPTRDIFF_T yyi;                      \
+          for (yyi = 0; yyi < (Count); yyi++)   \
+            (Dst)[yyi] = (Src)[yyi];            \
+        }                                       \
+      while (0)
+#  endif
+# endif
+#endif /* !YYCOPY_NEEDED */
+
+/* YYFINAL -- State number of the termination state.  */
+#define YYFINAL  12
+/* YYLAST -- Last index in YYTABLE.  */
+#define YYLAST   22
+
+/* YYNTOKENS -- Number of terminals.  */
+#define YYNTOKENS  11
+/* YYNNTS -- Number of nonterminals.  */
+#define YYNNTS  5
+/* YYNRULES -- Number of rules.  */
+#define YYNRULES  10
+/* YYNSTATES -- Number of states.  */
+#define YYNSTATES  24
+
+/* YYMAXUTOK -- Last valid token kind.  */
+#define YYMAXUTOK   262
+
+
+/* YYTRANSLATE(TOKEN-NUM) -- Symbol number corresponding to TOKEN-NUM
+   as returned by yylex, with out-of-bounds checking.  */
+#define YYTRANSLATE(YYX)                                \
+  (0 <= (YYX) && (YYX) <= YYMAXUTOK                     \
+   ? YY_CAST (yysymbol_kind_t, yytranslate[YYX])        \
+   : YYSYMBOL_YYUNDEF)
+
+/* YYTRANSLATE[TOKEN-NUM] -- Symbol number corresponding to TOKEN-NUM
+   as returned by yylex.  */
+static const yytype_int8 yytranslate[] =
+{
+       0,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       8,     9,     2,     2,    10,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     1,     2,     3,     4,
+       5,     6,     7
+};
+
+#if YYDEBUG
+  /* YYRLINE[YYN] -- Source line where rule number YYN was defined.  */
+static const yytype_int8 yyrline[] =
+{
+       0,    59,    59,    63,    64,    65,    66,    70,    71,    75,
+      76
+};
+#endif
+
+/** Accessing symbol of state STATE.  */
+#define YY_ACCESSING_SYMBOL(State) YY_CAST (yysymbol_kind_t, yystos[State])
+
+#if YYDEBUG || 0
+/* The user-facing name of the symbol whose (internal) number is
+   YYSYMBOL.  No bounds checking.  */
+static const char *yysymbol_name (yysymbol_kind_t yysymbol) YY_ATTRIBUTE_UNUSED;
+
+/* YYTNAME[SYMBOL-NUM] -- String name of the symbol SYMBOL-NUM.
+   First, the terminals, then, starting at YYNTOKENS, nonterminals.  */
+static const char *const yytname[] =
+{
+  "\"end of file\"", "error", "\"invalid token\"", "NAME", "NUM", "JUNK",
+  "ANY", "FIRST", "'('", "')'", "','", "$accept", "result",
+  "standby_config", "standby_list", "standby_name", YY_NULLPTR
+};
+
+static const char *
+yysymbol_name (yysymbol_kind_t yysymbol)
+{
+  return yytname[yysymbol];
+}
+#endif
+
+#ifdef YYPRINT
+/* YYTOKNUM[NUM] -- (External) token number corresponding to the
+   (internal) symbol number NUM (which must be that of a token).  */
+static const yytype_int16 yytoknum[] =
+{
+       0,   256,   257,   258,   259,   260,   261,   262,    40,    41,
+      44
+};
+#endif
+
+#define YYPACT_NINF (-10)
+
+#define yypact_value_is_default(Yyn) \
+  ((Yyn) == YYPACT_NINF)
+
+#define YYTABLE_NINF (-1)
+
+#define yytable_value_is_error(Yyn) \
+  0
+
+  /* YYPACT[STATE-NUM] -- Index in YYTABLE of the portion describing
+     STATE-NUM.  */
+static const yytype_int8 yypact[] =
+{
+      -2,   -10,    -5,    11,    14,    19,   -10,    -4,   -10,     6,
+      12,    13,   -10,     6,   -10,     2,     6,     6,   -10,   -10,
+       4,     7,   -10,   -10
+};
+
+  /* YYDEFACT[STATE-NUM] -- Default reduction number in state STATE-NUM.
+     Performed when YYTABLE does not specify something else to do.  Zero
+     means the default is an error.  */
+static const yytype_int8 yydefact[] =
+{
+       0,     9,    10,     0,     0,     0,     2,     3,     7,     0,
+       0,     0,     1,     0,    10,     0,     0,     0,     8,     4,
+       0,     0,     5,     6
+};
+
+  /* YYPGOTO[NTERM-NUM].  */
+static const yytype_int8 yypgoto[] =
+{
+     -10,   -10,   -10,    -9,     9
+};
+
+  /* YYDEFGOTO[NTERM-NUM].  */
+static const yytype_int8 yydefgoto[] =
+{
+       0,     5,     6,     7,     8
+};
+
+  /* YYTABLE[YYPACT[STATE-NUM]] -- What to do in state STATE-NUM.  If
+     positive, shift that token.  If negative, reduce the rule whose
+     number is the opposite.  If YYTABLE_NINF, syntax error.  */
+static const yytype_int8 yytable[] =
+{
+      15,     1,     2,     9,     3,     4,    13,    20,    21,     1,
+      14,    19,    13,    22,    13,    10,    23,    13,    11,    12,
+      16,    17,    18
+};
+
+static const yytype_int8 yycheck[] =
+{
+       9,     3,     4,     8,     6,     7,    10,    16,    17,     3,
+       4,     9,    10,     9,    10,     4,     9,    10,     4,     0,
+       8,     8,    13
+};
+
+  /* YYSTOS[STATE-NUM] -- The (internal number of the) accessing
+     symbol of state STATE-NUM.  */
+static const yytype_int8 yystos[] =
+{
+       0,     3,     4,     6,     7,    12,    13,    14,    15,     8,
+       4,     4,     0,    10,     4,    14,     8,     8,    15,     9,
+      14,    14,     9,     9
+};
+
+  /* YYR1[YYN] -- Symbol number of symbol that rule YYN derives.  */
+static const yytype_int8 yyr1[] =
+{
+       0,    11,    12,    13,    13,    13,    13,    14,    14,    15,
+      15
+};
+
+  /* YYR2[YYN] -- Number of symbols on the right hand side of rule YYN.  */
+static const yytype_int8 yyr2[] =
+{
+       0,     2,     1,     1,     4,     5,     5,     1,     3,     1,
+       1
+};
+
+
+enum { YYENOMEM = -2 };
+
+#define yyerrok         (yyerrstatus = 0)
+#define yyclearin       (yychar = YYEMPTY)
+
+#define YYACCEPT        goto yyacceptlab
+#define YYABORT         goto yyabortlab
+#define YYERROR         goto yyerrorlab
+
+
+#define YYRECOVERING()  (!!yyerrstatus)
+
+#define YYBACKUP(Token, Value)                                    \
+  do                                                              \
+    if (yychar == YYEMPTY)                                        \
+      {                                                           \
+        yychar = (Token);                                         \
+        yylval = (Value);                                         \
+        YYPOPSTACK (yylen);                                       \
+        yystate = *yyssp;                                         \
+        goto yybackup;                                            \
+      }                                                           \
+    else                                                          \
+      {                                                           \
+        yyerror (YY_("syntax error: cannot back up")); \
+        YYERROR;                                                  \
+      }                                                           \
+  while (0)
+
+/* Backward compatibility with an undocumented macro.
+   Use YYerror or YYUNDEF. */
+#define YYERRCODE YYUNDEF
+
+
+/* Enable debugging if requested.  */
+#if YYDEBUG
+
+# ifndef YYFPRINTF
+#  include <stdio.h> /* INFRINGES ON USER NAME SPACE */
+#  define YYFPRINTF fprintf
+# endif
+
+# define YYDPRINTF(Args)                        \
+do {                                            \
+  if (yydebug)                                  \
+    YYFPRINTF Args;                             \
+} while (0)
+
+/* This macro is provided for backward compatibility. */
+# ifndef YY_LOCATION_PRINT
+#  define YY_LOCATION_PRINT(File, Loc) ((void) 0)
+# endif
+
+
+# define YY_SYMBOL_PRINT(Title, Kind, Value, Location)                    \
+do {                                                                      \
+  if (yydebug)                                                            \
+    {                                                                     \
+      YYFPRINTF (stderr, "%s ", Title);                                   \
+      yy_symbol_print (stderr,                                            \
+                  Kind, Value); \
+      YYFPRINTF (stderr, "\n");                                           \
+    }                                                                     \
+} while (0)
+
+
+/*-----------------------------------.
+| Print this symbol's value on YYO.  |
+`-----------------------------------*/
+
+static void
+yy_symbol_value_print (FILE *yyo,
+                       yysymbol_kind_t yykind, YYSTYPE const * const yyvaluep)
+{
+  FILE *yyoutput = yyo;
+  YY_USE (yyoutput);
+  if (!yyvaluep)
+    return;
+# ifdef YYPRINT
+  if (yykind < YYNTOKENS)
+    YYPRINT (yyo, yytoknum[yykind], *yyvaluep);
+# endif
+  YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN
+  YY_USE (yykind);
+  YY_IGNORE_MAYBE_UNINITIALIZED_END
+}
+
+
+/*---------------------------.
+| Print this symbol on YYO.  |
+`---------------------------*/
+
+static void
+yy_symbol_print (FILE *yyo,
+                 yysymbol_kind_t yykind, YYSTYPE const * const yyvaluep)
+{
+  YYFPRINTF (yyo, "%s %s (",
+             yykind < YYNTOKENS ? "token" : "nterm", yysymbol_name (yykind));
+
+  yy_symbol_value_print (yyo, yykind, yyvaluep);
+  YYFPRINTF (yyo, ")");
+}
+
+/*------------------------------------------------------------------.
+| yy_stack_print -- Print the state stack from its BOTTOM up to its |
+| TOP (included).                                                   |
+`------------------------------------------------------------------*/
+
+static void
+yy_stack_print (yy_state_t *yybottom, yy_state_t *yytop)
+{
+  YYFPRINTF (stderr, "Stack now");
+  for (; yybottom <= yytop; yybottom++)
+    {
+      int yybot = *yybottom;
+      YYFPRINTF (stderr, " %d", yybot);
+    }
+  YYFPRINTF (stderr, "\n");
+}
+
+# define YY_STACK_PRINT(Bottom, Top)                            \
+do {                                                            \
+  if (yydebug)                                                  \
+    yy_stack_print ((Bottom), (Top));                           \
+} while (0)
+
+
+/*------------------------------------------------.
+| Report that the YYRULE is going to be reduced.  |
+`------------------------------------------------*/
+
+static void
+yy_reduce_print (yy_state_t *yyssp, YYSTYPE *yyvsp,
+                 int yyrule)
+{
+  int yylno = yyrline[yyrule];
+  int yynrhs = yyr2[yyrule];
+  int yyi;
+  YYFPRINTF (stderr, "Reducing stack by rule %d (line %d):\n",
+             yyrule - 1, yylno);
+  /* The symbols being reduced.  */
+  for (yyi = 0; yyi < yynrhs; yyi++)
+    {
+      YYFPRINTF (stderr, "   $%d = ", yyi + 1);
+      yy_symbol_print (stderr,
+                       YY_ACCESSING_SYMBOL (+yyssp[yyi + 1 - yynrhs]),
+                       &yyvsp[(yyi + 1) - (yynrhs)]);
+      YYFPRINTF (stderr, "\n");
+    }
+}
+
+# define YY_REDUCE_PRINT(Rule)          \
+do {                                    \
+  if (yydebug)                          \
+    yy_reduce_print (yyssp, yyvsp, Rule); \
+} while (0)
+
+/* Nonzero means print parse trace.  It is left uninitialized so that
+   multiple parsers can coexist.  */
+int yydebug;
+#else /* !YYDEBUG */
+# define YYDPRINTF(Args) ((void) 0)
+# define YY_SYMBOL_PRINT(Title, Kind, Value, Location)
+# define YY_STACK_PRINT(Bottom, Top)
+# define YY_REDUCE_PRINT(Rule)
+#endif /* !YYDEBUG */
+
+
+/* YYINITDEPTH -- initial size of the parser's stacks.  */
+#ifndef YYINITDEPTH
+# define YYINITDEPTH 200
+#endif
+
+/* YYMAXDEPTH -- maximum size the stacks can grow to (effective only
+   if the built-in stack extension method is used).
+
+   Do not make this value too large; the results are undefined if
+   YYSTACK_ALLOC_MAXIMUM < YYSTACK_BYTES (YYMAXDEPTH)
+   evaluated with infinite-precision integer arithmetic.  */
+
+#ifndef YYMAXDEPTH
+# define YYMAXDEPTH 10000
+#endif
+
+
+
+
+
+
+/*-----------------------------------------------.
+| Release the memory associated to this symbol.  |
+`-----------------------------------------------*/
+
+static void
+yydestruct (const char *yymsg,
+            yysymbol_kind_t yykind, YYSTYPE *yyvaluep)
+{
+  YY_USE (yyvaluep);
+  if (!yymsg)
+    yymsg = "Deleting";
+  YY_SYMBOL_PRINT (yymsg, yykind, yyvaluep, yylocationp);
+
+  YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN
+  YY_USE (yykind);
+  YY_IGNORE_MAYBE_UNINITIALIZED_END
+}
+
+
+/* Lookahead token kind.  */
+int yychar;
+
+/* The semantic value of the lookahead symbol.  */
+YYSTYPE yylval;
+/* Number of syntax errors so far.  */
+int yynerrs;
+
+
+
+
+/*----------.
+| yyparse.  |
+`----------*/
+
+int
+yyparse (void)
+{
+    yy_state_fast_t yystate = 0;
+    /* Number of tokens to shift before error messages enabled.  */
+    int yyerrstatus = 0;
+
+    /* Refer to the stacks through separate pointers, to allow yyoverflow
+       to reallocate them elsewhere.  */
+
+    /* Their size.  */
+    YYPTRDIFF_T yystacksize = YYINITDEPTH;
+
+    /* The state stack: array, bottom, top.  */
+    yy_state_t yyssa[YYINITDEPTH];
+    yy_state_t *yyss = yyssa;
+    yy_state_t *yyssp = yyss;
+
+    /* The semantic value stack: array, bottom, top.  */
+    YYSTYPE yyvsa[YYINITDEPTH];
+    YYSTYPE *yyvs = yyvsa;
+    YYSTYPE *yyvsp = yyvs;
+
+  int yyn;
+  /* The return value of yyparse.  */
+  int yyresult;
+  /* Lookahead symbol kind.  */
+  yysymbol_kind_t yytoken = YYSYMBOL_YYEMPTY;
+  /* The variables used to return semantic value and location from the
+     action routines.  */
+  YYSTYPE yyval;
+
+
+
+#define YYPOPSTACK(N)   (yyvsp -= (N), yyssp -= (N))
+
+  /* The number of symbols on the RHS of the reduced rule.
+     Keep to zero when no symbol should be popped.  */
+  int yylen = 0;
+
+  YYDPRINTF ((stderr, "Starting parse\n"));
+
+  yychar = YYEMPTY; /* Cause a token to be read.  */
+  goto yysetstate;
+
+
+/*------------------------------------------------------------.
+| yynewstate -- push a new state, which is found in yystate.  |
+`------------------------------------------------------------*/
+yynewstate:
+  /* In all cases, when you get here, the value and location stacks
+     have just been pushed.  So pushing a state here evens the stacks.  */
+  yyssp++;
+
+
+/*--------------------------------------------------------------------.
+| yysetstate -- set current state (the top of the stack) to yystate.  |
+`--------------------------------------------------------------------*/
+yysetstate:
+  YYDPRINTF ((stderr, "Entering state %d\n", yystate));
+  YY_ASSERT (0 <= yystate && yystate < YYNSTATES);
+  YY_IGNORE_USELESS_CAST_BEGIN
+  *yyssp = YY_CAST (yy_state_t, yystate);
+  YY_IGNORE_USELESS_CAST_END
+  YY_STACK_PRINT (yyss, yyssp);
+
+  if (yyss + yystacksize - 1 <= yyssp)
+#if !defined yyoverflow && !defined YYSTACK_RELOCATE
+    goto yyexhaustedlab;
+#else
+    {
+      /* Get the current used size of the three stacks, in elements.  */
+      YYPTRDIFF_T yysize = yyssp - yyss + 1;
+
+# if defined yyoverflow
+      {
+        /* Give user a chance to reallocate the stack.  Use copies of
+           these so that the &'s don't force the real ones into
+           memory.  */
+        yy_state_t *yyss1 = yyss;
+        YYSTYPE *yyvs1 = yyvs;
+
+        /* Each stack pointer address is followed by the size of the
+           data in use in that stack, in bytes.  This used to be a
+           conditional around just the two extra args, but that might
+           be undefined if yyoverflow is a macro.  */
+        yyoverflow (YY_("memory exhausted"),
+                    &yyss1, yysize * YYSIZEOF (*yyssp),
+                    &yyvs1, yysize * YYSIZEOF (*yyvsp),
+                    &yystacksize);
+        yyss = yyss1;
+        yyvs = yyvs1;
+      }
+# else /* defined YYSTACK_RELOCATE */
+      /* Extend the stack our own way.  */
+      if (YYMAXDEPTH <= yystacksize)
+        goto yyexhaustedlab;
+      yystacksize *= 2;
+      if (YYMAXDEPTH < yystacksize)
+        yystacksize = YYMAXDEPTH;
+
+      {
+        yy_state_t *yyss1 = yyss;
+        union yyalloc *yyptr =
+          YY_CAST (union yyalloc *,
+                   YYSTACK_ALLOC (YY_CAST (YYSIZE_T, YYSTACK_BYTES (yystacksize))));
+        if (! yyptr)
+          goto yyexhaustedlab;
+        YYSTACK_RELOCATE (yyss_alloc, yyss);
+        YYSTACK_RELOCATE (yyvs_alloc, yyvs);
+#  undef YYSTACK_RELOCATE
+        if (yyss1 != yyssa)
+          YYSTACK_FREE (yyss1);
+      }
+# endif
+
+      yyssp = yyss + yysize - 1;
+      yyvsp = yyvs + yysize - 1;
+
+      YY_IGNORE_USELESS_CAST_BEGIN
+      YYDPRINTF ((stderr, "Stack size increased to %ld\n",
+                  YY_CAST (long, yystacksize)));
+      YY_IGNORE_USELESS_CAST_END
+
+      if (yyss + yystacksize - 1 <= yyssp)
+        YYABORT;
+    }
+#endif /* !defined yyoverflow && !defined YYSTACK_RELOCATE */
+
+  if (yystate == YYFINAL)
+    YYACCEPT;
+
+  goto yybackup;
+
+
+/*-----------.
+| yybackup.  |
+`-----------*/
+yybackup:
+  /* Do appropriate processing given the current state.  Read a
+     lookahead token if we need one and don't already have one.  */
+
+  /* First try to decide what to do without reference to lookahead token.  */
+  yyn = yypact[yystate];
+  if (yypact_value_is_default (yyn))
+    goto yydefault;
+
+  /* Not known => get a lookahead token if don't already have one.  */
+
+  /* YYCHAR is either empty, or end-of-input, or a valid lookahead.  */
+  if (yychar == YYEMPTY)
+    {
+      YYDPRINTF ((stderr, "Reading a token\n"));
+      yychar = yylex ();
+    }
+
+  if (yychar <= YYEOF)
+    {
+      yychar = YYEOF;
+      yytoken = YYSYMBOL_YYEOF;
+      YYDPRINTF ((stderr, "Now at end of input.\n"));
+    }
+  else if (yychar == YYerror)
+    {
+      /* The scanner already issued an error message, process directly
+         to error recovery.  But do not keep the error token as
+         lookahead, it is too special and may lead us to an endless
+         loop in error recovery. */
+      yychar = YYUNDEF;
+      yytoken = YYSYMBOL_YYerror;
+      goto yyerrlab1;
+    }
+  else
+    {
+      yytoken = YYTRANSLATE (yychar);
+      YY_SYMBOL_PRINT ("Next token is", yytoken, &yylval, &yylloc);
+    }
+
+  /* If the proper action on seeing token YYTOKEN is to reduce or to
+     detect an error, take that action.  */
+  yyn += yytoken;
+  if (yyn < 0 || YYLAST < yyn || yycheck[yyn] != yytoken)
+    goto yydefault;
+  yyn = yytable[yyn];
+  if (yyn <= 0)
+    {
+      if (yytable_value_is_error (yyn))
+        goto yyerrlab;
+      yyn = -yyn;
+      goto yyreduce;
+    }
+
+  /* Count tokens shifted since error; after three, turn off error
+     status.  */
+  if (yyerrstatus)
+    yyerrstatus--;
+
+  /* Shift the lookahead token.  */
+  YY_SYMBOL_PRINT ("Shifting", yytoken, &yylval, &yylloc);
+  yystate = yyn;
+  YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN
+  *++yyvsp = yylval;
+  YY_IGNORE_MAYBE_UNINITIALIZED_END
+
+  /* Discard the shifted token.  */
+  yychar = YYEMPTY;
+  goto yynewstate;
+
+
+/*-----------------------------------------------------------.
+| yydefault -- do the default action for the current state.  |
+`-----------------------------------------------------------*/
+yydefault:
+  yyn = yydefact[yystate];
+  if (yyn == 0)
+    goto yyerrlab;
+  goto yyreduce;
+
+
+/*-----------------------------.
+| yyreduce -- do a reduction.  |
+`-----------------------------*/
+yyreduce:
+  /* yyn is the number of a rule to reduce with.  */
+  yylen = yyr2[yyn];
+
+  /* If YYLEN is nonzero, implement the default value of the action:
+     '$$ = $1'.
+
+     Otherwise, the following line sets YYVAL to garbage.
+     This behavior is undocumented and Bison
+     users should not rely upon it.  Assigning to YYVAL
+     unconditionally makes the parser a bit smaller, and it avoids a
+     GCC warning that YYVAL may be used uninitialized.  */
+  yyval = yyvsp[1-yylen];
+
+
+  YY_REDUCE_PRINT (yyn);
+  switch (yyn)
+    {
+  case 2: /* result: standby_config  */
+#line 59 "syncrep_gram.y"
+                                                        { syncrep_parse_result = (yyvsp[0].config); }
+#line 1177 "syncrep_gram.c"
+    break;
+
+  case 3: /* standby_config: standby_list  */
+#line 63 "syncrep_gram.y"
+                                                        { (yyval.config) = create_syncrep_config("1", (yyvsp[0].list), SYNC_REP_PRIORITY); }
+#line 1183 "syncrep_gram.c"
+    break;
+
+  case 4: /* standby_config: NUM '(' standby_list ')'  */
+#line 64 "syncrep_gram.y"
+                                                        { (yyval.config) = create_syncrep_config((yyvsp[-3].str), (yyvsp[-1].list), SYNC_REP_PRIORITY); }
+#line 1189 "syncrep_gram.c"
+    break;
+
+  case 5: /* standby_config: ANY NUM '(' standby_list ')'  */
+#line 65 "syncrep_gram.y"
+                                                        { (yyval.config) = create_syncrep_config((yyvsp[-3].str), (yyvsp[-1].list), SYNC_REP_QUORUM); }
+#line 1195 "syncrep_gram.c"
+    break;
+
+  case 6: /* standby_config: FIRST NUM '(' standby_list ')'  */
+#line 66 "syncrep_gram.y"
+                                                                { (yyval.config) = create_syncrep_config((yyvsp[-3].str), (yyvsp[-1].list), SYNC_REP_PRIORITY); }
+#line 1201 "syncrep_gram.c"
+    break;
+
+  case 7: /* standby_list: standby_name  */
+#line 70 "syncrep_gram.y"
+                                                                        { (yyval.list) = list_make1((yyvsp[0].str)); }
+#line 1207 "syncrep_gram.c"
+    break;
+
+  case 8: /* standby_list: standby_list ',' standby_name  */
+#line 71 "syncrep_gram.y"
+                                                        { (yyval.list) = lappend((yyvsp[-2].list), (yyvsp[0].str)); }
+#line 1213 "syncrep_gram.c"
+    break;
+
+  case 9: /* standby_name: NAME  */
+#line 75 "syncrep_gram.y"
+                                                                { (yyval.str) = (yyvsp[0].str); }
+#line 1219 "syncrep_gram.c"
+    break;
+
+  case 10: /* standby_name: NUM  */
+#line 76 "syncrep_gram.y"
+                                                                { (yyval.str) = (yyvsp[0].str); }
+#line 1225 "syncrep_gram.c"
+    break;
+
+
+#line 1229 "syncrep_gram.c"
+
+      default: break;
+    }
+  /* User semantic actions sometimes alter yychar, and that requires
+     that yytoken be updated with the new translation.  We take the
+     approach of translating immediately before every use of yytoken.
+     One alternative is translating here after every semantic action,
+     but that translation would be missed if the semantic action invokes
+     YYABORT, YYACCEPT, or YYERROR immediately after altering yychar or
+     if it invokes YYBACKUP.  In the case of YYABORT or YYACCEPT, an
+     incorrect destructor might then be invoked immediately.  In the
+     case of YYERROR or YYBACKUP, subsequent parser actions might lead
+     to an incorrect destructor call or verbose syntax error message
+     before the lookahead is translated.  */
+  YY_SYMBOL_PRINT ("-> $$ =", YY_CAST (yysymbol_kind_t, yyr1[yyn]), &yyval, &yyloc);
+
+  YYPOPSTACK (yylen);
+  yylen = 0;
+
+  *++yyvsp = yyval;
+
+  /* Now 'shift' the result of the reduction.  Determine what state
+     that goes to, based on the state we popped back to and the rule
+     number reduced by.  */
+  {
+    const int yylhs = yyr1[yyn] - YYNTOKENS;
+    const int yyi = yypgoto[yylhs] + *yyssp;
+    yystate = (0 <= yyi && yyi <= YYLAST && yycheck[yyi] == *yyssp
+               ? yytable[yyi]
+               : yydefgoto[yylhs]);
+  }
+
+  goto yynewstate;
+
+
+/*--------------------------------------.
+| yyerrlab -- here on detecting error.  |
+`--------------------------------------*/
+yyerrlab:
+  /* Make sure we have latest lookahead translation.  See comments at
+     user semantic actions for why this is necessary.  */
+  yytoken = yychar == YYEMPTY ? YYSYMBOL_YYEMPTY : YYTRANSLATE (yychar);
+  /* If not already recovering from an error, report this error.  */
+  if (!yyerrstatus)
+    {
+      ++yynerrs;
+      yyerror (YY_("syntax error"));
+    }
+
+  if (yyerrstatus == 3)
+    {
+      /* If just tried and failed to reuse lookahead token after an
+         error, discard it.  */
+
+      if (yychar <= YYEOF)
+        {
+          /* Return failure if at end of input.  */
+          if (yychar == YYEOF)
+            YYABORT;
+        }
+      else
+        {
+          yydestruct ("Error: discarding",
+                      yytoken, &yylval);
+          yychar = YYEMPTY;
+        }
+    }
+
+  /* Else will try to reuse lookahead token after shifting the error
+     token.  */
+  goto yyerrlab1;
+
+
+/*---------------------------------------------------.
+| yyerrorlab -- error raised explicitly by YYERROR.  |
+`---------------------------------------------------*/
+yyerrorlab:
+  /* Pacify compilers when the user code never invokes YYERROR and the
+     label yyerrorlab therefore never appears in user code.  */
+  if (0)
+    YYERROR;
+
+  /* Do not reclaim the symbols of the rule whose action triggered
+     this YYERROR.  */
+  YYPOPSTACK (yylen);
+  yylen = 0;
+  YY_STACK_PRINT (yyss, yyssp);
+  yystate = *yyssp;
+  goto yyerrlab1;
+
+
+/*-------------------------------------------------------------.
+| yyerrlab1 -- common code for both syntax error and YYERROR.  |
+`-------------------------------------------------------------*/
+yyerrlab1:
+  yyerrstatus = 3;      /* Each real token shifted decrements this.  */
+
+  /* Pop stack until we find a state that shifts the error token.  */
+  for (;;)
+    {
+      yyn = yypact[yystate];
+      if (!yypact_value_is_default (yyn))
+        {
+          yyn += YYSYMBOL_YYerror;
+          if (0 <= yyn && yyn <= YYLAST && yycheck[yyn] == YYSYMBOL_YYerror)
+            {
+              yyn = yytable[yyn];
+              if (0 < yyn)
+                break;
+            }
+        }
+
+      /* Pop the current state because it cannot handle the error token.  */
+      if (yyssp == yyss)
+        YYABORT;
+
+
+      yydestruct ("Error: popping",
+                  YY_ACCESSING_SYMBOL (yystate), yyvsp);
+      YYPOPSTACK (1);
+      yystate = *yyssp;
+      YY_STACK_PRINT (yyss, yyssp);
+    }
+
+  YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN
+  *++yyvsp = yylval;
+  YY_IGNORE_MAYBE_UNINITIALIZED_END
+
+
+  /* Shift the error token.  */
+  YY_SYMBOL_PRINT ("Shifting", YY_ACCESSING_SYMBOL (yyn), yyvsp, yylsp);
+
+  yystate = yyn;
+  goto yynewstate;
+
+
+/*-------------------------------------.
+| yyacceptlab -- YYACCEPT comes here.  |
+`-------------------------------------*/
+yyacceptlab:
+  yyresult = 0;
+  goto yyreturn;
+
+
+/*-----------------------------------.
+| yyabortlab -- YYABORT comes here.  |
+`-----------------------------------*/
+yyabortlab:
+  yyresult = 1;
+  goto yyreturn;
+
+
+#if !defined yyoverflow
+/*-------------------------------------------------.
+| yyexhaustedlab -- memory exhaustion comes here.  |
+`-------------------------------------------------*/
+yyexhaustedlab:
+  yyerror (YY_("memory exhausted"));
+  yyresult = 2;
+  goto yyreturn;
+#endif
+
+
+/*-------------------------------------------------------.
+| yyreturn -- parsing is finished, clean up and return.  |
+`-------------------------------------------------------*/
+yyreturn:
+  if (yychar != YYEMPTY)
+    {
+      /* Make sure we have latest lookahead translation.  See comments at
+         user semantic actions for why this is necessary.  */
+      yytoken = YYTRANSLATE (yychar);
+      yydestruct ("Cleanup: discarding lookahead",
+                  yytoken, &yylval);
+    }
+  /* Do not reclaim the symbols of the rule whose action triggered
+     this YYABORT or YYACCEPT.  */
+  YYPOPSTACK (yylen);
+  YY_STACK_PRINT (yyss, yyssp);
+  while (yyssp != yyss)
+    {
+      yydestruct ("Cleanup: popping",
+                  YY_ACCESSING_SYMBOL (+*yyssp), yyvsp);
+      YYPOPSTACK (1);
+    }
+#ifndef yyoverflow
+  if (yyss != yyssa)
+    YYSTACK_FREE (yyss);
+#endif
+
+  return yyresult;
+}
+
+#line 78 "syncrep_gram.y"
+
+
+static SyncRepConfigData *
+create_syncrep_config(const char *num_sync, List *members, uint8 syncrep_method)
+{
+	SyncRepConfigData *config;
+	int			size;
+	ListCell   *lc;
+	char	   *ptr;
+
+	/* Compute space needed for flat representation */
+	size = offsetof(SyncRepConfigData, member_names);
+	foreach(lc, members)
+	{
+		char	   *standby_name = (char *) lfirst(lc);
+
+		size += strlen(standby_name) + 1;
+	}
+
+	/* And transform the data into flat representation */
+	config = (SyncRepConfigData *) palloc(size);
+
+	config->config_size = size;
+	config->num_sync = atoi(num_sync);
+	config->syncrep_method = syncrep_method;
+	config->nmembers = list_length(members);
+	ptr = config->member_names;
+	foreach(lc, members)
+	{
+		char	   *standby_name = (char *) lfirst(lc);
+
+		strcpy(ptr, standby_name);
+		ptr += strlen(standby_name) + 1;
+	}
+
+	return config;
+}
+
+#include "syncrep_scanner.c"
diff --git a/src/backend/replication/syncrep_gram.y b/src/backend/replication/syncrep_gram.y
new file mode 100644
index 0000000..88d95f2
--- /dev/null
+++ b/src/backend/replication/syncrep_gram.y
@@ -0,0 +1,116 @@
+%{
+/*-------------------------------------------------------------------------
+ *
+ * syncrep_gram.y				- Parser for synchronous_standby_names
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/syncrep_gram.y
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "replication/syncrep.h"
+
+/* Result of parsing is returned in one of these two variables */
+SyncRepConfigData *syncrep_parse_result;
+char	   *syncrep_parse_error_msg;
+
+static SyncRepConfigData *create_syncrep_config(const char *num_sync,
+					List *members, uint8 syncrep_method);
+
+/*
+ * Bison doesn't allocate anything that needs to live across parser calls,
+ * so we can easily have it use palloc instead of malloc.  This prevents
+ * memory leaks if we error out during parsing.  Note this only works with
+ * bison >= 2.0.  However, in bison 1.875 the default is to use alloca()
+ * if possible, so there's not really much problem anyhow, at least if
+ * you're building with gcc.
+ */
+#define YYMALLOC palloc
+#define YYFREE   pfree
+
+%}
+
+%expect 0
+%name-prefix="syncrep_yy"
+
+%union
+{
+	char	   *str;
+	List	   *list;
+	SyncRepConfigData *config;
+}
+
+%token <str> NAME NUM JUNK ANY FIRST
+
+%type <config> result standby_config
+%type <list> standby_list
+%type <str> standby_name
+
+%start result
+
+%%
+result:
+		standby_config				{ syncrep_parse_result = $1; }
+	;
+
+standby_config:
+		standby_list				{ $$ = create_syncrep_config("1", $1, SYNC_REP_PRIORITY); }
+		| NUM '(' standby_list ')'		{ $$ = create_syncrep_config($1, $3, SYNC_REP_PRIORITY); }
+		| ANY NUM '(' standby_list ')'		{ $$ = create_syncrep_config($2, $4, SYNC_REP_QUORUM); }
+		| FIRST NUM '(' standby_list ')'		{ $$ = create_syncrep_config($2, $4, SYNC_REP_PRIORITY); }
+	;
+
+standby_list:
+		standby_name						{ $$ = list_make1($1); }
+		| standby_list ',' standby_name		{ $$ = lappend($1, $3); }
+	;
+
+standby_name:
+		NAME						{ $$ = $1; }
+		| NUM						{ $$ = $1; }
+	;
+%%
+
+static SyncRepConfigData *
+create_syncrep_config(const char *num_sync, List *members, uint8 syncrep_method)
+{
+	SyncRepConfigData *config;
+	int			size;
+	ListCell   *lc;
+	char	   *ptr;
+
+	/* Compute space needed for flat representation */
+	size = offsetof(SyncRepConfigData, member_names);
+	foreach(lc, members)
+	{
+		char	   *standby_name = (char *) lfirst(lc);
+
+		size += strlen(standby_name) + 1;
+	}
+
+	/* And transform the data into flat representation */
+	config = (SyncRepConfigData *) palloc(size);
+
+	config->config_size = size;
+	config->num_sync = atoi(num_sync);
+	config->syncrep_method = syncrep_method;
+	config->nmembers = list_length(members);
+	ptr = config->member_names;
+	foreach(lc, members)
+	{
+		char	   *standby_name = (char *) lfirst(lc);
+
+		strcpy(ptr, standby_name);
+		ptr += strlen(standby_name) + 1;
+	}
+
+	return config;
+}
+
+#include "syncrep_scanner.c"
diff --git a/src/backend/replication/syncrep_scanner.c b/src/backend/replication/syncrep_scanner.c
new file mode 100644
index 0000000..0577883
--- /dev/null
+++ b/src/backend/replication/syncrep_scanner.c
@@ -0,0 +1,2163 @@
+#line 2 "syncrep_scanner.c"
+
+#line 4 "syncrep_scanner.c"
+
+#define  YY_INT_ALIGNED short int
+
+/* A lexical scanner generated by flex */
+
+#define yy_create_buffer syncrep_yy_create_buffer
+#define yy_delete_buffer syncrep_yy_delete_buffer
+#define yy_scan_buffer syncrep_yy_scan_buffer
+#define yy_scan_string syncrep_yy_scan_string
+#define yy_scan_bytes syncrep_yy_scan_bytes
+#define yy_init_buffer syncrep_yy_init_buffer
+#define yy_flush_buffer syncrep_yy_flush_buffer
+#define yy_load_buffer_state syncrep_yy_load_buffer_state
+#define yy_switch_to_buffer syncrep_yy_switch_to_buffer
+#define yypush_buffer_state syncrep_yypush_buffer_state
+#define yypop_buffer_state syncrep_yypop_buffer_state
+#define yyensure_buffer_stack syncrep_yyensure_buffer_stack
+#define yy_flex_debug syncrep_yy_flex_debug
+#define yyin syncrep_yyin
+#define yyleng syncrep_yyleng
+#define yylex syncrep_yylex
+#define yylineno syncrep_yylineno
+#define yyout syncrep_yyout
+#define yyrestart syncrep_yyrestart
+#define yytext syncrep_yytext
+#define yywrap syncrep_yywrap
+#define yyalloc syncrep_yyalloc
+#define yyrealloc syncrep_yyrealloc
+#define yyfree syncrep_yyfree
+
+#define FLEX_SCANNER
+#define YY_FLEX_MAJOR_VERSION 2
+#define YY_FLEX_MINOR_VERSION 6
+#define YY_FLEX_SUBMINOR_VERSION 4
+#if YY_FLEX_SUBMINOR_VERSION > 0
+#define FLEX_BETA
+#endif
+
+#ifdef yy_create_buffer
+#define syncrep_yy_create_buffer_ALREADY_DEFINED
+#else
+#define yy_create_buffer syncrep_yy_create_buffer
+#endif
+
+#ifdef yy_delete_buffer
+#define syncrep_yy_delete_buffer_ALREADY_DEFINED
+#else
+#define yy_delete_buffer syncrep_yy_delete_buffer
+#endif
+
+#ifdef yy_scan_buffer
+#define syncrep_yy_scan_buffer_ALREADY_DEFINED
+#else
+#define yy_scan_buffer syncrep_yy_scan_buffer
+#endif
+
+#ifdef yy_scan_string
+#define syncrep_yy_scan_string_ALREADY_DEFINED
+#else
+#define yy_scan_string syncrep_yy_scan_string
+#endif
+
+#ifdef yy_scan_bytes
+#define syncrep_yy_scan_bytes_ALREADY_DEFINED
+#else
+#define yy_scan_bytes syncrep_yy_scan_bytes
+#endif
+
+#ifdef yy_init_buffer
+#define syncrep_yy_init_buffer_ALREADY_DEFINED
+#else
+#define yy_init_buffer syncrep_yy_init_buffer
+#endif
+
+#ifdef yy_flush_buffer
+#define syncrep_yy_flush_buffer_ALREADY_DEFINED
+#else
+#define yy_flush_buffer syncrep_yy_flush_buffer
+#endif
+
+#ifdef yy_load_buffer_state
+#define syncrep_yy_load_buffer_state_ALREADY_DEFINED
+#else
+#define yy_load_buffer_state syncrep_yy_load_buffer_state
+#endif
+
+#ifdef yy_switch_to_buffer
+#define syncrep_yy_switch_to_buffer_ALREADY_DEFINED
+#else
+#define yy_switch_to_buffer syncrep_yy_switch_to_buffer
+#endif
+
+#ifdef yypush_buffer_state
+#define syncrep_yypush_buffer_state_ALREADY_DEFINED
+#else
+#define yypush_buffer_state syncrep_yypush_buffer_state
+#endif
+
+#ifdef yypop_buffer_state
+#define syncrep_yypop_buffer_state_ALREADY_DEFINED
+#else
+#define yypop_buffer_state syncrep_yypop_buffer_state
+#endif
+
+#ifdef yyensure_buffer_stack
+#define syncrep_yyensure_buffer_stack_ALREADY_DEFINED
+#else
+#define yyensure_buffer_stack syncrep_yyensure_buffer_stack
+#endif
+
+#ifdef yylex
+#define syncrep_yylex_ALREADY_DEFINED
+#else
+#define yylex syncrep_yylex
+#endif
+
+#ifdef yyrestart
+#define syncrep_yyrestart_ALREADY_DEFINED
+#else
+#define yyrestart syncrep_yyrestart
+#endif
+
+#ifdef yylex_init
+#define syncrep_yylex_init_ALREADY_DEFINED
+#else
+#define yylex_init syncrep_yylex_init
+#endif
+
+#ifdef yylex_init_extra
+#define syncrep_yylex_init_extra_ALREADY_DEFINED
+#else
+#define yylex_init_extra syncrep_yylex_init_extra
+#endif
+
+#ifdef yylex_destroy
+#define syncrep_yylex_destroy_ALREADY_DEFINED
+#else
+#define yylex_destroy syncrep_yylex_destroy
+#endif
+
+#ifdef yyget_debug
+#define syncrep_yyget_debug_ALREADY_DEFINED
+#else
+#define yyget_debug syncrep_yyget_debug
+#endif
+
+#ifdef yyset_debug
+#define syncrep_yyset_debug_ALREADY_DEFINED
+#else
+#define yyset_debug syncrep_yyset_debug
+#endif
+
+#ifdef yyget_extra
+#define syncrep_yyget_extra_ALREADY_DEFINED
+#else
+#define yyget_extra syncrep_yyget_extra
+#endif
+
+#ifdef yyset_extra
+#define syncrep_yyset_extra_ALREADY_DEFINED
+#else
+#define yyset_extra syncrep_yyset_extra
+#endif
+
+#ifdef yyget_in
+#define syncrep_yyget_in_ALREADY_DEFINED
+#else
+#define yyget_in syncrep_yyget_in
+#endif
+
+#ifdef yyset_in
+#define syncrep_yyset_in_ALREADY_DEFINED
+#else
+#define yyset_in syncrep_yyset_in
+#endif
+
+#ifdef yyget_out
+#define syncrep_yyget_out_ALREADY_DEFINED
+#else
+#define yyget_out syncrep_yyget_out
+#endif
+
+#ifdef yyset_out
+#define syncrep_yyset_out_ALREADY_DEFINED
+#else
+#define yyset_out syncrep_yyset_out
+#endif
+
+#ifdef yyget_leng
+#define syncrep_yyget_leng_ALREADY_DEFINED
+#else
+#define yyget_leng syncrep_yyget_leng
+#endif
+
+#ifdef yyget_text
+#define syncrep_yyget_text_ALREADY_DEFINED
+#else
+#define yyget_text syncrep_yyget_text
+#endif
+
+#ifdef yyget_lineno
+#define syncrep_yyget_lineno_ALREADY_DEFINED
+#else
+#define yyget_lineno syncrep_yyget_lineno
+#endif
+
+#ifdef yyset_lineno
+#define syncrep_yyset_lineno_ALREADY_DEFINED
+#else
+#define yyset_lineno syncrep_yyset_lineno
+#endif
+
+#ifdef yywrap
+#define syncrep_yywrap_ALREADY_DEFINED
+#else
+#define yywrap syncrep_yywrap
+#endif
+
+#ifdef yyalloc
+#define syncrep_yyalloc_ALREADY_DEFINED
+#else
+#define yyalloc syncrep_yyalloc
+#endif
+
+#ifdef yyrealloc
+#define syncrep_yyrealloc_ALREADY_DEFINED
+#else
+#define yyrealloc syncrep_yyrealloc
+#endif
+
+#ifdef yyfree
+#define syncrep_yyfree_ALREADY_DEFINED
+#else
+#define yyfree syncrep_yyfree
+#endif
+
+#ifdef yytext
+#define syncrep_yytext_ALREADY_DEFINED
+#else
+#define yytext syncrep_yytext
+#endif
+
+#ifdef yyleng
+#define syncrep_yyleng_ALREADY_DEFINED
+#else
+#define yyleng syncrep_yyleng
+#endif
+
+#ifdef yyin
+#define syncrep_yyin_ALREADY_DEFINED
+#else
+#define yyin syncrep_yyin
+#endif
+
+#ifdef yyout
+#define syncrep_yyout_ALREADY_DEFINED
+#else
+#define yyout syncrep_yyout
+#endif
+
+#ifdef yy_flex_debug
+#define syncrep_yy_flex_debug_ALREADY_DEFINED
+#else
+#define yy_flex_debug syncrep_yy_flex_debug
+#endif
+
+#ifdef yylineno
+#define syncrep_yylineno_ALREADY_DEFINED
+#else
+#define yylineno syncrep_yylineno
+#endif
+
+/* First, we deal with  platform-specific or compiler-specific issues. */
+
+/* begin standard C headers. */
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <stdlib.h>
+
+/* end standard C headers. */
+
+/* flex integer type definitions */
+
+#ifndef FLEXINT_H
+#define FLEXINT_H
+
+/* C99 systems have <inttypes.h>. Non-C99 systems may or may not. */
+
+#if defined (__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
+
+/* C99 says to define __STDC_LIMIT_MACROS before including stdint.h,
+ * if you want the limit (max/min) macros for int types. 
+ */
+#ifndef __STDC_LIMIT_MACROS
+#define __STDC_LIMIT_MACROS 1
+#endif
+
+#include <inttypes.h>
+typedef int8_t flex_int8_t;
+typedef uint8_t flex_uint8_t;
+typedef int16_t flex_int16_t;
+typedef uint16_t flex_uint16_t;
+typedef int32_t flex_int32_t;
+typedef uint32_t flex_uint32_t;
+#else
+typedef signed char flex_int8_t;
+typedef short int flex_int16_t;
+typedef int flex_int32_t;
+typedef unsigned char flex_uint8_t; 
+typedef unsigned short int flex_uint16_t;
+typedef unsigned int flex_uint32_t;
+
+/* Limits of integral types. */
+#ifndef INT8_MIN
+#define INT8_MIN               (-128)
+#endif
+#ifndef INT16_MIN
+#define INT16_MIN              (-32767-1)
+#endif
+#ifndef INT32_MIN
+#define INT32_MIN              (-2147483647-1)
+#endif
+#ifndef INT8_MAX
+#define INT8_MAX               (127)
+#endif
+#ifndef INT16_MAX
+#define INT16_MAX              (32767)
+#endif
+#ifndef INT32_MAX
+#define INT32_MAX              (2147483647)
+#endif
+#ifndef UINT8_MAX
+#define UINT8_MAX              (255U)
+#endif
+#ifndef UINT16_MAX
+#define UINT16_MAX             (65535U)
+#endif
+#ifndef UINT32_MAX
+#define UINT32_MAX             (4294967295U)
+#endif
+
+#ifndef SIZE_MAX
+#define SIZE_MAX               (~(size_t)0)
+#endif
+
+#endif /* ! C99 */
+
+#endif /* ! FLEXINT_H */
+
+/* begin standard C++ headers. */
+
+/* TODO: this is always defined, so inline it */
+#define yyconst const
+
+#if defined(__GNUC__) && __GNUC__ >= 3
+#define yynoreturn __attribute__((__noreturn__))
+#else
+#define yynoreturn
+#endif
+
+/* Returned upon end-of-file. */
+#define YY_NULL 0
+
+/* Promotes a possibly negative, possibly signed char to an
+ *   integer in range [0..255] for use as an array index.
+ */
+#define YY_SC_TO_UI(c) ((YY_CHAR) (c))
+
+/* Enter a start condition.  This macro really ought to take a parameter,
+ * but we do it the disgusting crufty way forced on us by the ()-less
+ * definition of BEGIN.
+ */
+#define BEGIN (yy_start) = 1 + 2 *
+/* Translate the current start state into a value that can be later handed
+ * to BEGIN to return to the state.  The YYSTATE alias is for lex
+ * compatibility.
+ */
+#define YY_START (((yy_start) - 1) / 2)
+#define YYSTATE YY_START
+/* Action number for EOF rule of a given start state. */
+#define YY_STATE_EOF(state) (YY_END_OF_BUFFER + state + 1)
+/* Special action meaning "start processing a new file". */
+#define YY_NEW_FILE yyrestart( yyin  )
+#define YY_END_OF_BUFFER_CHAR 0
+
+/* Size of default input buffer. */
+#ifndef YY_BUF_SIZE
+#ifdef __ia64__
+/* On IA-64, the buffer size is 16k, not 8k.
+ * Moreover, YY_BUF_SIZE is 2*YY_READ_BUF_SIZE in the general case.
+ * Ditto for the __ia64__ case accordingly.
+ */
+#define YY_BUF_SIZE 32768
+#else
+#define YY_BUF_SIZE 16384
+#endif /* __ia64__ */
+#endif
+
+/* The state buf must be large enough to hold one state per character in the main buffer.
+ */
+#define YY_STATE_BUF_SIZE   ((YY_BUF_SIZE + 2) * sizeof(yy_state_type))
+
+#ifndef YY_TYPEDEF_YY_BUFFER_STATE
+#define YY_TYPEDEF_YY_BUFFER_STATE
+typedef struct yy_buffer_state *YY_BUFFER_STATE;
+#endif
+
+#ifndef YY_TYPEDEF_YY_SIZE_T
+#define YY_TYPEDEF_YY_SIZE_T
+typedef size_t yy_size_t;
+#endif
+
+extern int yyleng;
+
+extern FILE *yyin, *yyout;
+
+#define EOB_ACT_CONTINUE_SCAN 0
+#define EOB_ACT_END_OF_FILE 1
+#define EOB_ACT_LAST_MATCH 2
+    
+    #define YY_LESS_LINENO(n)
+    #define YY_LINENO_REWIND_TO(ptr)
+    
+/* Return all but the first "n" matched characters back to the input stream. */
+#define yyless(n) \
+	do \
+		{ \
+		/* Undo effects of setting up yytext. */ \
+        int yyless_macro_arg = (n); \
+        YY_LESS_LINENO(yyless_macro_arg);\
+		*yy_cp = (yy_hold_char); \
+		YY_RESTORE_YY_MORE_OFFSET \
+		(yy_c_buf_p) = yy_cp = yy_bp + yyless_macro_arg - YY_MORE_ADJ; \
+		YY_DO_BEFORE_ACTION; /* set up yytext again */ \
+		} \
+	while ( 0 )
+#define unput(c) yyunput( c, (yytext_ptr)  )
+
+#ifndef YY_STRUCT_YY_BUFFER_STATE
+#define YY_STRUCT_YY_BUFFER_STATE
+struct yy_buffer_state
+	{
+	FILE *yy_input_file;
+
+	char *yy_ch_buf;		/* input buffer */
+	char *yy_buf_pos;		/* current position in input buffer */
+
+	/* Size of input buffer in bytes, not including room for EOB
+	 * characters.
+	 */
+	int yy_buf_size;
+
+	/* Number of characters read into yy_ch_buf, not including EOB
+	 * characters.
+	 */
+	int yy_n_chars;
+
+	/* Whether we "own" the buffer - i.e., we know we created it,
+	 * and can realloc() it to grow it, and should free() it to
+	 * delete it.
+	 */
+	int yy_is_our_buffer;
+
+	/* Whether this is an "interactive" input source; if so, and
+	 * if we're using stdio for input, then we want to use getc()
+	 * instead of fread(), to make sure we stop fetching input after
+	 * each newline.
+	 */
+	int yy_is_interactive;
+
+	/* Whether we're considered to be at the beginning of a line.
+	 * If so, '^' rules will be active on the next match, otherwise
+	 * not.
+	 */
+	int yy_at_bol;
+
+    int yy_bs_lineno; /**< The line count. */
+    int yy_bs_column; /**< The column count. */
+
+	/* Whether to try to fill the input buffer when we reach the
+	 * end of it.
+	 */
+	int yy_fill_buffer;
+
+	int yy_buffer_status;
+
+#define YY_BUFFER_NEW 0
+#define YY_BUFFER_NORMAL 1
+	/* When an EOF's been seen but there's still some text to process
+	 * then we mark the buffer as YY_EOF_PENDING, to indicate that we
+	 * shouldn't try reading from the input source any more.  We might
+	 * still have a bunch of tokens to match, though, because of
+	 * possible backing-up.
+	 *
+	 * When we actually see the EOF, we change the status to "new"
+	 * (via yyrestart()), so that the user can continue scanning by
+	 * just pointing yyin at a new input file.
+	 */
+#define YY_BUFFER_EOF_PENDING 2
+
+	};
+#endif /* !YY_STRUCT_YY_BUFFER_STATE */
+
+/* Stack of input buffers. */
+static size_t yy_buffer_stack_top = 0; /**< index of top of stack. */
+static size_t yy_buffer_stack_max = 0; /**< capacity of stack. */
+static YY_BUFFER_STATE * yy_buffer_stack = NULL; /**< Stack as an array. */
+
+/* We provide macros for accessing buffer states in case in the
+ * future we want to put the buffer states in a more general
+ * "scanner state".
+ *
+ * Returns the top of the stack, or NULL.
+ */
+#define YY_CURRENT_BUFFER ( (yy_buffer_stack) \
+                          ? (yy_buffer_stack)[(yy_buffer_stack_top)] \
+                          : NULL)
+/* Same as previous macro, but useful when we know that the buffer stack is not
+ * NULL or when we need an lvalue. For internal use only.
+ */
+#define YY_CURRENT_BUFFER_LVALUE (yy_buffer_stack)[(yy_buffer_stack_top)]
+
+/* yy_hold_char holds the character lost when yytext is formed. */
+static char yy_hold_char;
+static int yy_n_chars;		/* number of characters read into yy_ch_buf */
+int yyleng;
+
+/* Points to current character in buffer. */
+static char *yy_c_buf_p = NULL;
+static int yy_init = 0;		/* whether we need to initialize */
+static int yy_start = 0;	/* start state number */
+
+/* Flag which is used to allow yywrap()'s to do buffer switches
+ * instead of setting up a fresh yyin.  A bit of a hack ...
+ */
+static int yy_did_buffer_switch_on_eof;
+
+void yyrestart ( FILE *input_file  );
+void yy_switch_to_buffer ( YY_BUFFER_STATE new_buffer  );
+YY_BUFFER_STATE yy_create_buffer ( FILE *file, int size  );
+void yy_delete_buffer ( YY_BUFFER_STATE b  );
+void yy_flush_buffer ( YY_BUFFER_STATE b  );
+void yypush_buffer_state ( YY_BUFFER_STATE new_buffer  );
+void yypop_buffer_state ( void );
+
+static void yyensure_buffer_stack ( void );
+static void yy_load_buffer_state ( void );
+static void yy_init_buffer ( YY_BUFFER_STATE b, FILE *file  );
+#define YY_FLUSH_BUFFER yy_flush_buffer( YY_CURRENT_BUFFER )
+
+YY_BUFFER_STATE yy_scan_buffer ( char *base, yy_size_t size  );
+YY_BUFFER_STATE yy_scan_string ( const char *yy_str  );
+YY_BUFFER_STATE yy_scan_bytes ( const char *bytes, int len  );
+
+void *yyalloc ( yy_size_t  );
+void *yyrealloc ( void *, yy_size_t  );
+void yyfree ( void *  );
+
+#define yy_new_buffer yy_create_buffer
+#define yy_set_interactive(is_interactive) \
+	{ \
+	if ( ! YY_CURRENT_BUFFER ){ \
+        yyensure_buffer_stack (); \
+		YY_CURRENT_BUFFER_LVALUE =    \
+            yy_create_buffer( yyin, YY_BUF_SIZE ); \
+	} \
+	YY_CURRENT_BUFFER_LVALUE->yy_is_interactive = is_interactive; \
+	}
+#define yy_set_bol(at_bol) \
+	{ \
+	if ( ! YY_CURRENT_BUFFER ){\
+        yyensure_buffer_stack (); \
+		YY_CURRENT_BUFFER_LVALUE =    \
+            yy_create_buffer( yyin, YY_BUF_SIZE ); \
+	} \
+	YY_CURRENT_BUFFER_LVALUE->yy_at_bol = at_bol; \
+	}
+#define YY_AT_BOL() (YY_CURRENT_BUFFER_LVALUE->yy_at_bol)
+
+/* Begin user sect3 */
+
+#define syncrep_yywrap() (/*CONSTCOND*/1)
+#define YY_SKIP_YYWRAP
+typedef flex_uint8_t YY_CHAR;
+
+FILE *yyin = NULL, *yyout = NULL;
+
+typedef int yy_state_type;
+
+extern int yylineno;
+int yylineno = 1;
+
+extern char *yytext;
+#ifdef yytext_ptr
+#undef yytext_ptr
+#endif
+#define yytext_ptr yytext
+
+static yy_state_type yy_get_previous_state ( void );
+static yy_state_type yy_try_NUL_trans ( yy_state_type current_state  );
+static int yy_get_next_buffer ( void );
+static void yynoreturn yy_fatal_error ( const char* msg  );
+
+/* Done after the current pattern has been matched and before the
+ * corresponding action - sets up yytext.
+ */
+#define YY_DO_BEFORE_ACTION \
+	(yytext_ptr) = yy_bp; \
+	yyleng = (int) (yy_cp - yy_bp); \
+	(yy_hold_char) = *yy_cp; \
+	*yy_cp = '\0'; \
+	(yy_c_buf_p) = yy_cp;
+#define YY_NUM_RULES 15
+#define YY_END_OF_BUFFER 16
+/* This struct is not used in this scanner,
+   but its presence is necessary. */
+struct yy_trans_info
+	{
+	flex_int32_t yy_verify;
+	flex_int32_t yy_nxt;
+	};
+static const flex_int16_t yy_accept[32] =
+    {   0,
+        0,    0,    0,    0,   16,   14,    1,    1,    4,   12,
+       13,   10,   11,    9,    8,    8,    8,    6,    7,    1,
+        9,    8,    8,    8,    6,    5,    2,    8,    8,    3,
+        0
+    } ;
+
+static const YY_CHAR yy_ec[256] =
+    {   0,
+        1,    1,    1,    1,    1,    1,    1,    1,    2,    3,
+        2,    2,    2,    1,    1,    1,    1,    1,    1,    1,
+        1,    1,    1,    1,    1,    1,    1,    1,    1,    1,
+        1,    2,    1,    4,    1,    5,    1,    1,    1,    6,
+        7,    8,    1,    9,    1,    1,    1,   10,   10,   10,
+       10,   10,   10,   10,   10,   10,   10,    1,    1,    1,
+        1,    1,    1,    1,   11,   12,   12,   12,   12,   13,
+       12,   12,   14,   12,   12,   12,   12,   15,   12,   12,
+       12,   16,   17,   18,   12,   12,   12,   12,   19,   12,
+        1,    1,    1,    1,   12,    1,   11,   12,   12,   12,
+
+       12,   13,   12,   12,   14,   12,   12,   12,   12,   15,
+       12,   12,   12,   16,   17,   18,   12,   12,   12,   12,
+       19,   12,    1,    1,    1,    1,    1,   12,   12,   12,
+       12,   12,   12,   12,   12,   12,   12,   12,   12,   12,
+       12,   12,   12,   12,   12,   12,   12,   12,   12,   12,
+       12,   12,   12,   12,   12,   12,   12,   12,   12,   12,
+       12,   12,   12,   12,   12,   12,   12,   12,   12,   12,
+       12,   12,   12,   12,   12,   12,   12,   12,   12,   12,
+       12,   12,   12,   12,   12,   12,   12,   12,   12,   12,
+       12,   12,   12,   12,   12,   12,   12,   12,   12,   12,
+
+       12,   12,   12,   12,   12,   12,   12,   12,   12,   12,
+       12,   12,   12,   12,   12,   12,   12,   12,   12,   12,
+       12,   12,   12,   12,   12,   12,   12,   12,   12,   12,
+       12,   12,   12,   12,   12,   12,   12,   12,   12,   12,
+       12,   12,   12,   12,   12,   12,   12,   12,   12,   12,
+       12,   12,   12,   12,   12
+    } ;
+
+static const YY_CHAR yy_meta[20] =
+    {   0,
+        1,    1,    1,    2,    3,    1,    1,    1,    1,    3,
+        3,    3,    3,    3,    3,    3,    3,    3,    3
+    } ;
+
+static const flex_int16_t yy_base[35] =
+    {   0,
+        0,    0,   39,   38,   41,   44,   18,   20,   44,   44,
+       44,   44,   44,   30,   24,    0,   24,    0,   33,   22,
+       26,    0,   16,   18,    0,   44,    0,   16,   14,    0,
+       44,   25,   27,   28
+    } ;
+
+static const flex_int16_t yy_def[35] =
+    {   0,
+       31,    1,   32,   32,   31,   31,   31,   31,   31,   31,
+       31,   31,   31,   31,   33,   33,   33,   34,   31,   31,
+       31,   33,   33,   33,   34,   31,   33,   33,   33,   33,
+        0,   31,   31,   31
+    } ;
+
+static const flex_int16_t yy_nxt[64] =
+    {   0,
+        6,    7,    8,    9,    6,   10,   11,   12,   13,   14,
+       15,   16,   17,   16,   16,   16,   16,   16,   16,   20,
+       20,   20,   20,   20,   20,   18,   18,   18,   25,   22,
+       25,   30,   29,   28,   27,   21,   26,   24,   23,   21,
+       31,   19,   19,    5,   31,   31,   31,   31,   31,   31,
+       31,   31,   31,   31,   31,   31,   31,   31,   31,   31,
+       31,   31,   31
+    } ;
+
+static const flex_int16_t yy_chk[64] =
+    {   0,
+        1,    1,    1,    1,    1,    1,    1,    1,    1,    1,
+        1,    1,    1,    1,    1,    1,    1,    1,    1,    7,
+        7,    8,    8,   20,   20,   32,   32,   32,   34,   33,
+       34,   29,   28,   24,   23,   21,   19,   17,   15,   14,
+        5,    4,    3,   31,   31,   31,   31,   31,   31,   31,
+       31,   31,   31,   31,   31,   31,   31,   31,   31,   31,
+       31,   31,   31
+    } ;
+
+static yy_state_type yy_last_accepting_state;
+static char *yy_last_accepting_cpos;
+
+extern int yy_flex_debug;
+int yy_flex_debug = 0;
+
+/* The intent behind this definition is that it'll catch
+ * any uses of REJECT which flex missed.
+ */
+#define REJECT reject_used_but_not_detected
+#define yymore() yymore_used_but_not_detected
+#define YY_MORE_ADJ 0
+#define YY_RESTORE_YY_MORE_OFFSET
+char *yytext;
+#line 1 "syncrep_scanner.l"
+#line 2 "syncrep_scanner.l"
+/*-------------------------------------------------------------------------
+ *
+ * syncrep_scanner.l
+ *	  a lexical scanner for synchronous_standby_names
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/syncrep_scanner.l
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "lib/stringinfo.h"
+
+/* Avoid exit() on fatal scanner errors (a bit ugly -- see yy_fatal_error) */
+#undef fprintf
+#define fprintf(file, fmt, msg)  fprintf_to_ereport(fmt, msg)
+
+static void
+fprintf_to_ereport(const char *fmt, const char *msg)
+{
+	ereport(ERROR, (errmsg_internal("%s", msg)));
+}
+
+/* Handles to the buffer that the lexer uses internally */
+static YY_BUFFER_STATE scanbufhandle;
+
+static StringInfoData xdbuf;
+
+/* LCOV_EXCL_START */
+
+#line 762 "syncrep_scanner.c"
+#define YY_NO_INPUT 1
+/*
+ * <xd> delimited identifiers (double-quoted identifiers)
+ */
+
+#line 768 "syncrep_scanner.c"
+
+#define INITIAL 0
+#define xd 1
+
+#ifndef YY_NO_UNISTD_H
+/* Special case for "unistd.h", since it is non-ANSI. We include it way
+ * down here because we want the user's section 1 to have been scanned first.
+ * The user has a chance to override it with an option.
+ */
+#include <unistd.h>
+#endif
+
+#ifndef YY_EXTRA_TYPE
+#define YY_EXTRA_TYPE void *
+#endif
+
+static int yy_init_globals ( void );
+
+/* Accessor methods to globals.
+   These are made visible to non-reentrant scanners for convenience. */
+
+int yylex_destroy ( void );
+
+int yyget_debug ( void );
+
+void yyset_debug ( int debug_flag  );
+
+YY_EXTRA_TYPE yyget_extra ( void );
+
+void yyset_extra ( YY_EXTRA_TYPE user_defined  );
+
+FILE *yyget_in ( void );
+
+void yyset_in  ( FILE * _in_str  );
+
+FILE *yyget_out ( void );
+
+void yyset_out  ( FILE * _out_str  );
+
+			int yyget_leng ( void );
+
+char *yyget_text ( void );
+
+int yyget_lineno ( void );
+
+void yyset_lineno ( int _line_number  );
+
+/* Macros after this point can all be overridden by user definitions in
+ * section 1.
+ */
+
+#ifndef YY_SKIP_YYWRAP
+#ifdef __cplusplus
+extern "C" int yywrap ( void );
+#else
+extern int yywrap ( void );
+#endif
+#endif
+
+#ifndef YY_NO_UNPUT
+    
+#endif
+
+#ifndef yytext_ptr
+static void yy_flex_strncpy ( char *, const char *, int );
+#endif
+
+#ifdef YY_NEED_STRLEN
+static int yy_flex_strlen ( const char * );
+#endif
+
+#ifndef YY_NO_INPUT
+#ifdef __cplusplus
+static int yyinput ( void );
+#else
+static int input ( void );
+#endif
+
+#endif
+
+/* Amount of stuff to slurp up with each read. */
+#ifndef YY_READ_BUF_SIZE
+#ifdef __ia64__
+/* On IA-64, the buffer size is 16k, not 8k */
+#define YY_READ_BUF_SIZE 16384
+#else
+#define YY_READ_BUF_SIZE 8192
+#endif /* __ia64__ */
+#endif
+
+/* Copy whatever the last rule matched to the standard output. */
+#ifndef ECHO
+/* This used to be an fputs(), but since the string might contain NUL's,
+ * we now use fwrite().
+ */
+#define ECHO do { if (fwrite( yytext, (size_t) yyleng, 1, yyout )) {} } while (0)
+#endif
+
+/* Gets input and stuffs it into "buf".  number of characters read, or YY_NULL,
+ * is returned in "result".
+ */
+#ifndef YY_INPUT
+#define YY_INPUT(buf,result,max_size) \
+	if ( YY_CURRENT_BUFFER_LVALUE->yy_is_interactive ) \
+		{ \
+		int c = '*'; \
+		int n; \
+		for ( n = 0; n < max_size && \
+			     (c = getc( yyin )) != EOF && c != '\n'; ++n ) \
+			buf[n] = (char) c; \
+		if ( c == '\n' ) \
+			buf[n++] = (char) c; \
+		if ( c == EOF && ferror( yyin ) ) \
+			YY_FATAL_ERROR( "input in flex scanner failed" ); \
+		result = n; \
+		} \
+	else \
+		{ \
+		errno=0; \
+		while ( (result = (int) fread(buf, 1, (yy_size_t) max_size, yyin)) == 0 && ferror(yyin)) \
+			{ \
+			if( errno != EINTR) \
+				{ \
+				YY_FATAL_ERROR( "input in flex scanner failed" ); \
+				break; \
+				} \
+			errno=0; \
+			clearerr(yyin); \
+			} \
+		}\
+\
+
+#endif
+
+/* No semi-colon after return; correct usage is to write "yyterminate();" -
+ * we don't want an extra ';' after the "return" because that will cause
+ * some compilers to complain about unreachable statements.
+ */
+#ifndef yyterminate
+#define yyterminate() return YY_NULL
+#endif
+
+/* Number of entries by which start-condition stack grows. */
+#ifndef YY_START_STACK_INCR
+#define YY_START_STACK_INCR 25
+#endif
+
+/* Report a fatal error. */
+#ifndef YY_FATAL_ERROR
+#define YY_FATAL_ERROR(msg) yy_fatal_error( msg )
+#endif
+
+/* end tables serialization structures and prototypes */
+
+/* Default declaration of generated scanner - a define so the user can
+ * easily add parameters.
+ */
+#ifndef YY_DECL
+#define YY_DECL_IS_OURS 1
+
+extern int yylex (void);
+
+#define YY_DECL int yylex (void)
+#endif /* !YY_DECL */
+
+/* Code executed at the beginning of each rule, after yytext and yyleng
+ * have been set up.
+ */
+#ifndef YY_USER_ACTION
+#define YY_USER_ACTION
+#endif
+
+/* Code executed at the end of each rule. */
+#ifndef YY_BREAK
+#define YY_BREAK /*LINTED*/break;
+#endif
+
+#define YY_RULE_SETUP \
+	YY_USER_ACTION
+
+/** The main scanner function which does all the work.
+ */
+YY_DECL
+{
+	yy_state_type yy_current_state;
+	char *yy_cp, *yy_bp;
+	int yy_act;
+    
+	if ( !(yy_init) )
+		{
+		(yy_init) = 1;
+
+#ifdef YY_USER_INIT
+		YY_USER_INIT;
+#endif
+
+		if ( ! (yy_start) )
+			(yy_start) = 1;	/* first start state */
+
+		if ( ! yyin )
+			yyin = stdin;
+
+		if ( ! yyout )
+			yyout = stdout;
+
+		if ( ! YY_CURRENT_BUFFER ) {
+			yyensure_buffer_stack ();
+			YY_CURRENT_BUFFER_LVALUE =
+				yy_create_buffer( yyin, YY_BUF_SIZE );
+		}
+
+		yy_load_buffer_state(  );
+		}
+
+	{
+#line 66 "syncrep_scanner.l"
+
+#line 986 "syncrep_scanner.c"
+
+	while ( /*CONSTCOND*/1 )		/* loops until end-of-file is reached */
+		{
+		yy_cp = (yy_c_buf_p);
+
+		/* Support of yytext. */
+		*yy_cp = (yy_hold_char);
+
+		/* yy_bp points to the position in yy_ch_buf of the start of
+		 * the current run.
+		 */
+		yy_bp = yy_cp;
+
+		yy_current_state = (yy_start);
+yy_match:
+		do
+			{
+			YY_CHAR yy_c = yy_ec[YY_SC_TO_UI(*yy_cp)] ;
+			if ( yy_accept[yy_current_state] )
+				{
+				(yy_last_accepting_state) = yy_current_state;
+				(yy_last_accepting_cpos) = yy_cp;
+				}
+			while ( yy_chk[yy_base[yy_current_state] + yy_c] != yy_current_state )
+				{
+				yy_current_state = (int) yy_def[yy_current_state];
+				if ( yy_current_state >= 32 )
+					yy_c = yy_meta[yy_c];
+				}
+			yy_current_state = yy_nxt[yy_base[yy_current_state] + yy_c];
+			++yy_cp;
+			}
+		while ( yy_current_state != 31 );
+		yy_cp = (yy_last_accepting_cpos);
+		yy_current_state = (yy_last_accepting_state);
+
+yy_find_action:
+		yy_act = yy_accept[yy_current_state];
+
+		YY_DO_BEFORE_ACTION;
+
+do_action:	/* This label is used only to access EOF actions. */
+
+		switch ( yy_act )
+	{ /* beginning of action switch */
+			case 0: /* must back up */
+			/* undo the effects of YY_DO_BEFORE_ACTION */
+			*yy_cp = (yy_hold_char);
+			yy_cp = (yy_last_accepting_cpos);
+			yy_current_state = (yy_last_accepting_state);
+			goto yy_find_action;
+
+case 1:
+/* rule 1 can match eol */
+YY_RULE_SETUP
+#line 67 "syncrep_scanner.l"
+{ /* ignore */ }
+	YY_BREAK
+/* brute-force case insensitivity is safer than relying on flex -i */
+case 2:
+YY_RULE_SETUP
+#line 71 "syncrep_scanner.l"
+{ return ANY; }
+	YY_BREAK
+case 3:
+YY_RULE_SETUP
+#line 72 "syncrep_scanner.l"
+{ return FIRST; }
+	YY_BREAK
+case 4:
+YY_RULE_SETUP
+#line 74 "syncrep_scanner.l"
+{
+				initStringInfo(&xdbuf);
+				BEGIN(xd);
+		}
+	YY_BREAK
+case 5:
+YY_RULE_SETUP
+#line 78 "syncrep_scanner.l"
+{
+				appendStringInfoChar(&xdbuf, '"');
+		}
+	YY_BREAK
+case 6:
+/* rule 6 can match eol */
+YY_RULE_SETUP
+#line 81 "syncrep_scanner.l"
+{
+				appendStringInfoString(&xdbuf, yytext);
+		}
+	YY_BREAK
+case 7:
+YY_RULE_SETUP
+#line 84 "syncrep_scanner.l"
+{
+				yylval.str = xdbuf.data;
+				xdbuf.data = NULL;
+				BEGIN(INITIAL);
+				return NAME;
+		}
+	YY_BREAK
+case YY_STATE_EOF(xd):
+#line 90 "syncrep_scanner.l"
+{
+				yyerror("unterminated quoted identifier");
+				return JUNK;
+		}
+	YY_BREAK
+case 8:
+YY_RULE_SETUP
+#line 95 "syncrep_scanner.l"
+{
+				yylval.str = pstrdup(yytext);
+				return NAME;
+		}
+	YY_BREAK
+case 9:
+YY_RULE_SETUP
+#line 100 "syncrep_scanner.l"
+{
+				yylval.str = pstrdup(yytext);
+				return NUM;
+		}
+	YY_BREAK
+case 10:
+YY_RULE_SETUP
+#line 105 "syncrep_scanner.l"
+{
+				yylval.str = "*";
+				return NAME;
+		}
+	YY_BREAK
+case 11:
+YY_RULE_SETUP
+#line 110 "syncrep_scanner.l"
+{ return ','; }
+	YY_BREAK
+case 12:
+YY_RULE_SETUP
+#line 111 "syncrep_scanner.l"
+{ return '('; }
+	YY_BREAK
+case 13:
+YY_RULE_SETUP
+#line 112 "syncrep_scanner.l"
+{ return ')'; }
+	YY_BREAK
+case 14:
+YY_RULE_SETUP
+#line 114 "syncrep_scanner.l"
+{ return JUNK; }
+	YY_BREAK
+case 15:
+YY_RULE_SETUP
+#line 115 "syncrep_scanner.l"
+YY_FATAL_ERROR( "flex scanner jammed" );
+	YY_BREAK
+#line 1145 "syncrep_scanner.c"
+case YY_STATE_EOF(INITIAL):
+	yyterminate();
+
+	case YY_END_OF_BUFFER:
+		{
+		/* Amount of text matched not including the EOB char. */
+		int yy_amount_of_matched_text = (int) (yy_cp - (yytext_ptr)) - 1;
+
+		/* Undo the effects of YY_DO_BEFORE_ACTION. */
+		*yy_cp = (yy_hold_char);
+		YY_RESTORE_YY_MORE_OFFSET
+
+		if ( YY_CURRENT_BUFFER_LVALUE->yy_buffer_status == YY_BUFFER_NEW )
+			{
+			/* We're scanning a new file or input source.  It's
+			 * possible that this happened because the user
+			 * just pointed yyin at a new source and called
+			 * yylex().  If so, then we have to assure
+			 * consistency between YY_CURRENT_BUFFER and our
+			 * globals.  Here is the right place to do so, because
+			 * this is the first action (other than possibly a
+			 * back-up) that will match for the new input source.
+			 */
+			(yy_n_chars) = YY_CURRENT_BUFFER_LVALUE->yy_n_chars;
+			YY_CURRENT_BUFFER_LVALUE->yy_input_file = yyin;
+			YY_CURRENT_BUFFER_LVALUE->yy_buffer_status = YY_BUFFER_NORMAL;
+			}
+
+		/* Note that here we test for yy_c_buf_p "<=" to the position
+		 * of the first EOB in the buffer, since yy_c_buf_p will
+		 * already have been incremented past the NUL character
+		 * (since all states make transitions on EOB to the
+		 * end-of-buffer state).  Contrast this with the test
+		 * in input().
+		 */
+		if ( (yy_c_buf_p) <= &YY_CURRENT_BUFFER_LVALUE->yy_ch_buf[(yy_n_chars)] )
+			{ /* This was really a NUL. */
+			yy_state_type yy_next_state;
+
+			(yy_c_buf_p) = (yytext_ptr) + yy_amount_of_matched_text;
+
+			yy_current_state = yy_get_previous_state(  );
+
+			/* Okay, we're now positioned to make the NUL
+			 * transition.  We couldn't have
+			 * yy_get_previous_state() go ahead and do it
+			 * for us because it doesn't know how to deal
+			 * with the possibility of jamming (and we don't
+			 * want to build jamming into it because then it
+			 * will run more slowly).
+			 */
+
+			yy_next_state = yy_try_NUL_trans( yy_current_state );
+
+			yy_bp = (yytext_ptr) + YY_MORE_ADJ;
+
+			if ( yy_next_state )
+				{
+				/* Consume the NUL. */
+				yy_cp = ++(yy_c_buf_p);
+				yy_current_state = yy_next_state;
+				goto yy_match;
+				}
+
+			else
+				{
+				yy_cp = (yy_last_accepting_cpos);
+				yy_current_state = (yy_last_accepting_state);
+				goto yy_find_action;
+				}
+			}
+
+		else switch ( yy_get_next_buffer(  ) )
+			{
+			case EOB_ACT_END_OF_FILE:
+				{
+				(yy_did_buffer_switch_on_eof) = 0;
+
+				if ( yywrap(  ) )
+					{
+					/* Note: because we've taken care in
+					 * yy_get_next_buffer() to have set up
+					 * yytext, we can now set up
+					 * yy_c_buf_p so that if some total
+					 * hoser (like flex itself) wants to
+					 * call the scanner after we return the
+					 * YY_NULL, it'll still work - another
+					 * YY_NULL will get returned.
+					 */
+					(yy_c_buf_p) = (yytext_ptr) + YY_MORE_ADJ;
+
+					yy_act = YY_STATE_EOF(YY_START);
+					goto do_action;
+					}
+
+				else
+					{
+					if ( ! (yy_did_buffer_switch_on_eof) )
+						YY_NEW_FILE;
+					}
+				break;
+				}
+
+			case EOB_ACT_CONTINUE_SCAN:
+				(yy_c_buf_p) =
+					(yytext_ptr) + yy_amount_of_matched_text;
+
+				yy_current_state = yy_get_previous_state(  );
+
+				yy_cp = (yy_c_buf_p);
+				yy_bp = (yytext_ptr) + YY_MORE_ADJ;
+				goto yy_match;
+
+			case EOB_ACT_LAST_MATCH:
+				(yy_c_buf_p) =
+				&YY_CURRENT_BUFFER_LVALUE->yy_ch_buf[(yy_n_chars)];
+
+				yy_current_state = yy_get_previous_state(  );
+
+				yy_cp = (yy_c_buf_p);
+				yy_bp = (yytext_ptr) + YY_MORE_ADJ;
+				goto yy_find_action;
+			}
+		break;
+		}
+
+	default:
+		YY_FATAL_ERROR(
+			"fatal flex scanner internal error--no action found" );
+	} /* end of action switch */
+		} /* end of scanning one token */
+	} /* end of user's declarations */
+} /* end of yylex */
+
+/* yy_get_next_buffer - try to read in a new buffer
+ *
+ * Returns a code representing an action:
+ *	EOB_ACT_LAST_MATCH -
+ *	EOB_ACT_CONTINUE_SCAN - continue scanning from current position
+ *	EOB_ACT_END_OF_FILE - end of file
+ */
+static int yy_get_next_buffer (void)
+{
+    	char *dest = YY_CURRENT_BUFFER_LVALUE->yy_ch_buf;
+	char *source = (yytext_ptr);
+	int number_to_move, i;
+	int ret_val;
+
+	if ( (yy_c_buf_p) > &YY_CURRENT_BUFFER_LVALUE->yy_ch_buf[(yy_n_chars) + 1] )
+		YY_FATAL_ERROR(
+		"fatal flex scanner internal error--end of buffer missed" );
+
+	if ( YY_CURRENT_BUFFER_LVALUE->yy_fill_buffer == 0 )
+		{ /* Don't try to fill the buffer, so this is an EOF. */
+		if ( (yy_c_buf_p) - (yytext_ptr) - YY_MORE_ADJ == 1 )
+			{
+			/* We matched a single character, the EOB, so
+			 * treat this as a final EOF.
+			 */
+			return EOB_ACT_END_OF_FILE;
+			}
+
+		else
+			{
+			/* We matched some text prior to the EOB, first
+			 * process it.
+			 */
+			return EOB_ACT_LAST_MATCH;
+			}
+		}
+
+	/* Try to read more data. */
+
+	/* First move last chars to start of buffer. */
+	number_to_move = (int) ((yy_c_buf_p) - (yytext_ptr) - 1);
+
+	for ( i = 0; i < number_to_move; ++i )
+		*(dest++) = *(source++);
+
+	if ( YY_CURRENT_BUFFER_LVALUE->yy_buffer_status == YY_BUFFER_EOF_PENDING )
+		/* don't do the read, it's not guaranteed to return an EOF,
+		 * just force an EOF
+		 */
+		YY_CURRENT_BUFFER_LVALUE->yy_n_chars = (yy_n_chars) = 0;
+
+	else
+		{
+			int num_to_read =
+			YY_CURRENT_BUFFER_LVALUE->yy_buf_size - number_to_move - 1;
+
+		while ( num_to_read <= 0 )
+			{ /* Not enough room in the buffer - grow it. */
+
+			/* just a shorter name for the current buffer */
+			YY_BUFFER_STATE b = YY_CURRENT_BUFFER_LVALUE;
+
+			int yy_c_buf_p_offset =
+				(int) ((yy_c_buf_p) - b->yy_ch_buf);
+
+			if ( b->yy_is_our_buffer )
+				{
+				int new_size = b->yy_buf_size * 2;
+
+				if ( new_size <= 0 )
+					b->yy_buf_size += b->yy_buf_size / 8;
+				else
+					b->yy_buf_size *= 2;
+
+				b->yy_ch_buf = (char *)
+					/* Include room in for 2 EOB chars. */
+					yyrealloc( (void *) b->yy_ch_buf,
+							 (yy_size_t) (b->yy_buf_size + 2)  );
+				}
+			else
+				/* Can't grow it, we don't own it. */
+				b->yy_ch_buf = NULL;
+
+			if ( ! b->yy_ch_buf )
+				YY_FATAL_ERROR(
+				"fatal error - scanner input buffer overflow" );
+
+			(yy_c_buf_p) = &b->yy_ch_buf[yy_c_buf_p_offset];
+
+			num_to_read = YY_CURRENT_BUFFER_LVALUE->yy_buf_size -
+						number_to_move - 1;
+
+			}
+
+		if ( num_to_read > YY_READ_BUF_SIZE )
+			num_to_read = YY_READ_BUF_SIZE;
+
+		/* Read in more data. */
+		YY_INPUT( (&YY_CURRENT_BUFFER_LVALUE->yy_ch_buf[number_to_move]),
+			(yy_n_chars), num_to_read );
+
+		YY_CURRENT_BUFFER_LVALUE->yy_n_chars = (yy_n_chars);
+		}
+
+	if ( (yy_n_chars) == 0 )
+		{
+		if ( number_to_move == YY_MORE_ADJ )
+			{
+			ret_val = EOB_ACT_END_OF_FILE;
+			yyrestart( yyin  );
+			}
+
+		else
+			{
+			ret_val = EOB_ACT_LAST_MATCH;
+			YY_CURRENT_BUFFER_LVALUE->yy_buffer_status =
+				YY_BUFFER_EOF_PENDING;
+			}
+		}
+
+	else
+		ret_val = EOB_ACT_CONTINUE_SCAN;
+
+	if (((yy_n_chars) + number_to_move) > YY_CURRENT_BUFFER_LVALUE->yy_buf_size) {
+		/* Extend the array by 50%, plus the number we really need. */
+		int new_size = (yy_n_chars) + number_to_move + ((yy_n_chars) >> 1);
+		YY_CURRENT_BUFFER_LVALUE->yy_ch_buf = (char *) yyrealloc(
+			(void *) YY_CURRENT_BUFFER_LVALUE->yy_ch_buf, (yy_size_t) new_size  );
+		if ( ! YY_CURRENT_BUFFER_LVALUE->yy_ch_buf )
+			YY_FATAL_ERROR( "out of dynamic memory in yy_get_next_buffer()" );
+		/* "- 2" to take care of EOB's */
+		YY_CURRENT_BUFFER_LVALUE->yy_buf_size = (int) (new_size - 2);
+	}
+
+	(yy_n_chars) += number_to_move;
+	YY_CURRENT_BUFFER_LVALUE->yy_ch_buf[(yy_n_chars)] = YY_END_OF_BUFFER_CHAR;
+	YY_CURRENT_BUFFER_LVALUE->yy_ch_buf[(yy_n_chars) + 1] = YY_END_OF_BUFFER_CHAR;
+
+	(yytext_ptr) = &YY_CURRENT_BUFFER_LVALUE->yy_ch_buf[0];
+
+	return ret_val;
+}
+
+/* yy_get_previous_state - get the state just before the EOB char was reached */
+
+    static yy_state_type yy_get_previous_state (void)
+{
+	yy_state_type yy_current_state;
+	char *yy_cp;
+    
+	yy_current_state = (yy_start);
+
+	for ( yy_cp = (yytext_ptr) + YY_MORE_ADJ; yy_cp < (yy_c_buf_p); ++yy_cp )
+		{
+		YY_CHAR yy_c = (*yy_cp ? yy_ec[YY_SC_TO_UI(*yy_cp)] : 1);
+		if ( yy_accept[yy_current_state] )
+			{
+			(yy_last_accepting_state) = yy_current_state;
+			(yy_last_accepting_cpos) = yy_cp;
+			}
+		while ( yy_chk[yy_base[yy_current_state] + yy_c] != yy_current_state )
+			{
+			yy_current_state = (int) yy_def[yy_current_state];
+			if ( yy_current_state >= 32 )
+				yy_c = yy_meta[yy_c];
+			}
+		yy_current_state = yy_nxt[yy_base[yy_current_state] + yy_c];
+		}
+
+	return yy_current_state;
+}
+
+/* yy_try_NUL_trans - try to make a transition on the NUL character
+ *
+ * synopsis
+ *	next_state = yy_try_NUL_trans( current_state );
+ */
+    static yy_state_type yy_try_NUL_trans  (yy_state_type yy_current_state )
+{
+	int yy_is_jam;
+    	char *yy_cp = (yy_c_buf_p);
+
+	YY_CHAR yy_c = 1;
+	if ( yy_accept[yy_current_state] )
+		{
+		(yy_last_accepting_state) = yy_current_state;
+		(yy_last_accepting_cpos) = yy_cp;
+		}
+	while ( yy_chk[yy_base[yy_current_state] + yy_c] != yy_current_state )
+		{
+		yy_current_state = (int) yy_def[yy_current_state];
+		if ( yy_current_state >= 32 )
+			yy_c = yy_meta[yy_c];
+		}
+	yy_current_state = yy_nxt[yy_base[yy_current_state] + yy_c];
+	yy_is_jam = (yy_current_state == 31);
+
+		return yy_is_jam ? 0 : yy_current_state;
+}
+
+#ifndef YY_NO_UNPUT
+
+#endif
+
+#ifndef YY_NO_INPUT
+#ifdef __cplusplus
+    static int yyinput (void)
+#else
+    static int input  (void)
+#endif
+
+{
+	int c;
+    
+	*(yy_c_buf_p) = (yy_hold_char);
+
+	if ( *(yy_c_buf_p) == YY_END_OF_BUFFER_CHAR )
+		{
+		/* yy_c_buf_p now points to the character we want to return.
+		 * If this occurs *before* the EOB characters, then it's a
+		 * valid NUL; if not, then we've hit the end of the buffer.
+		 */
+		if ( (yy_c_buf_p) < &YY_CURRENT_BUFFER_LVALUE->yy_ch_buf[(yy_n_chars)] )
+			/* This was really a NUL. */
+			*(yy_c_buf_p) = '\0';
+
+		else
+			{ /* need more input */
+			int offset = (int) ((yy_c_buf_p) - (yytext_ptr));
+			++(yy_c_buf_p);
+
+			switch ( yy_get_next_buffer(  ) )
+				{
+				case EOB_ACT_LAST_MATCH:
+					/* This happens because yy_g_n_b()
+					 * sees that we've accumulated a
+					 * token and flags that we need to
+					 * try matching the token before
+					 * proceeding.  But for input(),
+					 * there's no matching to consider.
+					 * So convert the EOB_ACT_LAST_MATCH
+					 * to EOB_ACT_END_OF_FILE.
+					 */
+
+					/* Reset buffer status. */
+					yyrestart( yyin );
+
+					/*FALLTHROUGH*/
+
+				case EOB_ACT_END_OF_FILE:
+					{
+					if ( yywrap(  ) )
+						return 0;
+
+					if ( ! (yy_did_buffer_switch_on_eof) )
+						YY_NEW_FILE;
+#ifdef __cplusplus
+					return yyinput();
+#else
+					return input();
+#endif
+					}
+
+				case EOB_ACT_CONTINUE_SCAN:
+					(yy_c_buf_p) = (yytext_ptr) + offset;
+					break;
+				}
+			}
+		}
+
+	c = *(unsigned char *) (yy_c_buf_p);	/* cast for 8-bit char's */
+	*(yy_c_buf_p) = '\0';	/* preserve yytext */
+	(yy_hold_char) = *++(yy_c_buf_p);
+
+	return c;
+}
+#endif	/* ifndef YY_NO_INPUT */
+
+/** Immediately switch to a different input stream.
+ * @param input_file A readable stream.
+ * 
+ * @note This function does not reset the start condition to @c INITIAL .
+ */
+    void yyrestart  (FILE * input_file )
+{
+    
+	if ( ! YY_CURRENT_BUFFER ){
+        yyensure_buffer_stack ();
+		YY_CURRENT_BUFFER_LVALUE =
+            yy_create_buffer( yyin, YY_BUF_SIZE );
+	}
+
+	yy_init_buffer( YY_CURRENT_BUFFER, input_file );
+	yy_load_buffer_state(  );
+}
+
+/** Switch to a different input buffer.
+ * @param new_buffer The new input buffer.
+ * 
+ */
+    void yy_switch_to_buffer  (YY_BUFFER_STATE  new_buffer )
+{
+    
+	/* TODO. We should be able to replace this entire function body
+	 * with
+	 *		yypop_buffer_state();
+	 *		yypush_buffer_state(new_buffer);
+     */
+	yyensure_buffer_stack ();
+	if ( YY_CURRENT_BUFFER == new_buffer )
+		return;
+
+	if ( YY_CURRENT_BUFFER )
+		{
+		/* Flush out information for old buffer. */
+		*(yy_c_buf_p) = (yy_hold_char);
+		YY_CURRENT_BUFFER_LVALUE->yy_buf_pos = (yy_c_buf_p);
+		YY_CURRENT_BUFFER_LVALUE->yy_n_chars = (yy_n_chars);
+		}
+
+	YY_CURRENT_BUFFER_LVALUE = new_buffer;
+	yy_load_buffer_state(  );
+
+	/* We don't actually know whether we did this switch during
+	 * EOF (yywrap()) processing, but the only time this flag
+	 * is looked at is after yywrap() is called, so it's safe
+	 * to go ahead and always set it.
+	 */
+	(yy_did_buffer_switch_on_eof) = 1;
+}
+
+static void yy_load_buffer_state  (void)
+{
+    	(yy_n_chars) = YY_CURRENT_BUFFER_LVALUE->yy_n_chars;
+	(yytext_ptr) = (yy_c_buf_p) = YY_CURRENT_BUFFER_LVALUE->yy_buf_pos;
+	yyin = YY_CURRENT_BUFFER_LVALUE->yy_input_file;
+	(yy_hold_char) = *(yy_c_buf_p);
+}
+
+/** Allocate and initialize an input buffer state.
+ * @param file A readable stream.
+ * @param size The character buffer size in bytes. When in doubt, use @c YY_BUF_SIZE.
+ * 
+ * @return the allocated buffer state.
+ */
+    YY_BUFFER_STATE yy_create_buffer  (FILE * file, int  size )
+{
+	YY_BUFFER_STATE b;
+    
+	b = (YY_BUFFER_STATE) yyalloc( sizeof( struct yy_buffer_state )  );
+	if ( ! b )
+		YY_FATAL_ERROR( "out of dynamic memory in yy_create_buffer()" );
+
+	b->yy_buf_size = size;
+
+	/* yy_ch_buf has to be 2 characters longer than the size given because
+	 * we need to put in 2 end-of-buffer characters.
+	 */
+	b->yy_ch_buf = (char *) yyalloc( (yy_size_t) (b->yy_buf_size + 2)  );
+	if ( ! b->yy_ch_buf )
+		YY_FATAL_ERROR( "out of dynamic memory in yy_create_buffer()" );
+
+	b->yy_is_our_buffer = 1;
+
+	yy_init_buffer( b, file );
+
+	return b;
+}
+
+/** Destroy the buffer.
+ * @param b a buffer created with yy_create_buffer()
+ * 
+ */
+    void yy_delete_buffer (YY_BUFFER_STATE  b )
+{
+    
+	if ( ! b )
+		return;
+
+	if ( b == YY_CURRENT_BUFFER ) /* Not sure if we should pop here. */
+		YY_CURRENT_BUFFER_LVALUE = (YY_BUFFER_STATE) 0;
+
+	if ( b->yy_is_our_buffer )
+		yyfree( (void *) b->yy_ch_buf  );
+
+	yyfree( (void *) b  );
+}
+
+/* Initializes or reinitializes a buffer.
+ * This function is sometimes called more than once on the same buffer,
+ * such as during a yyrestart() or at EOF.
+ */
+    static void yy_init_buffer  (YY_BUFFER_STATE  b, FILE * file )
+
+{
+	int oerrno = errno;
+    
+	yy_flush_buffer( b );
+
+	b->yy_input_file = file;
+	b->yy_fill_buffer = 1;
+
+    /* If b is the current buffer, then yy_init_buffer was _probably_
+     * called from yyrestart() or through yy_get_next_buffer.
+     * In that case, we don't want to reset the lineno or column.
+     */
+    if (b != YY_CURRENT_BUFFER){
+        b->yy_bs_lineno = 1;
+        b->yy_bs_column = 0;
+    }
+
+        b->yy_is_interactive = 0;
+    
+	errno = oerrno;
+}
+
+/** Discard all buffered characters. On the next scan, YY_INPUT will be called.
+ * @param b the buffer state to be flushed, usually @c YY_CURRENT_BUFFER.
+ * 
+ */
+    void yy_flush_buffer (YY_BUFFER_STATE  b )
+{
+    	if ( ! b )
+		return;
+
+	b->yy_n_chars = 0;
+
+	/* We always need two end-of-buffer characters.  The first causes
+	 * a transition to the end-of-buffer state.  The second causes
+	 * a jam in that state.
+	 */
+	b->yy_ch_buf[0] = YY_END_OF_BUFFER_CHAR;
+	b->yy_ch_buf[1] = YY_END_OF_BUFFER_CHAR;
+
+	b->yy_buf_pos = &b->yy_ch_buf[0];
+
+	b->yy_at_bol = 1;
+	b->yy_buffer_status = YY_BUFFER_NEW;
+
+	if ( b == YY_CURRENT_BUFFER )
+		yy_load_buffer_state(  );
+}
+
+/** Pushes the new state onto the stack. The new state becomes
+ *  the current state. This function will allocate the stack
+ *  if necessary.
+ *  @param new_buffer The new state.
+ *  
+ */
+void yypush_buffer_state (YY_BUFFER_STATE new_buffer )
+{
+    	if (new_buffer == NULL)
+		return;
+
+	yyensure_buffer_stack();
+
+	/* This block is copied from yy_switch_to_buffer. */
+	if ( YY_CURRENT_BUFFER )
+		{
+		/* Flush out information for old buffer. */
+		*(yy_c_buf_p) = (yy_hold_char);
+		YY_CURRENT_BUFFER_LVALUE->yy_buf_pos = (yy_c_buf_p);
+		YY_CURRENT_BUFFER_LVALUE->yy_n_chars = (yy_n_chars);
+		}
+
+	/* Only push if top exists. Otherwise, replace top. */
+	if (YY_CURRENT_BUFFER)
+		(yy_buffer_stack_top)++;
+	YY_CURRENT_BUFFER_LVALUE = new_buffer;
+
+	/* copied from yy_switch_to_buffer. */
+	yy_load_buffer_state(  );
+	(yy_did_buffer_switch_on_eof) = 1;
+}
+
+/** Removes and deletes the top of the stack, if present.
+ *  The next element becomes the new top.
+ *  
+ */
+void yypop_buffer_state (void)
+{
+    	if (!YY_CURRENT_BUFFER)
+		return;
+
+	yy_delete_buffer(YY_CURRENT_BUFFER );
+	YY_CURRENT_BUFFER_LVALUE = NULL;
+	if ((yy_buffer_stack_top) > 0)
+		--(yy_buffer_stack_top);
+
+	if (YY_CURRENT_BUFFER) {
+		yy_load_buffer_state(  );
+		(yy_did_buffer_switch_on_eof) = 1;
+	}
+}
+
+/* Allocates the stack if it does not exist.
+ *  Guarantees space for at least one push.
+ */
+static void yyensure_buffer_stack (void)
+{
+	yy_size_t num_to_alloc;
+    
+	if (!(yy_buffer_stack)) {
+
+		/* First allocation is just for 2 elements, since we don't know if this
+		 * scanner will even need a stack. We use 2 instead of 1 to avoid an
+		 * immediate realloc on the next call.
+         */
+      num_to_alloc = 1; /* After all that talk, this was set to 1 anyways... */
+		(yy_buffer_stack) = (struct yy_buffer_state**)yyalloc
+								(num_to_alloc * sizeof(struct yy_buffer_state*)
+								);
+		if ( ! (yy_buffer_stack) )
+			YY_FATAL_ERROR( "out of dynamic memory in yyensure_buffer_stack()" );
+
+		memset((yy_buffer_stack), 0, num_to_alloc * sizeof(struct yy_buffer_state*));
+
+		(yy_buffer_stack_max) = num_to_alloc;
+		(yy_buffer_stack_top) = 0;
+		return;
+	}
+
+	if ((yy_buffer_stack_top) >= ((yy_buffer_stack_max)) - 1){
+
+		/* Increase the buffer to prepare for a possible push. */
+		yy_size_t grow_size = 8 /* arbitrary grow size */;
+
+		num_to_alloc = (yy_buffer_stack_max) + grow_size;
+		(yy_buffer_stack) = (struct yy_buffer_state**)yyrealloc
+								((yy_buffer_stack),
+								num_to_alloc * sizeof(struct yy_buffer_state*)
+								);
+		if ( ! (yy_buffer_stack) )
+			YY_FATAL_ERROR( "out of dynamic memory in yyensure_buffer_stack()" );
+
+		/* zero only the new slots.*/
+		memset((yy_buffer_stack) + (yy_buffer_stack_max), 0, grow_size * sizeof(struct yy_buffer_state*));
+		(yy_buffer_stack_max) = num_to_alloc;
+	}
+}
+
+/** Setup the input buffer state to scan directly from a user-specified character buffer.
+ * @param base the character buffer
+ * @param size the size in bytes of the character buffer
+ * 
+ * @return the newly allocated buffer state object.
+ */
+YY_BUFFER_STATE yy_scan_buffer  (char * base, yy_size_t  size )
+{
+	YY_BUFFER_STATE b;
+    
+	if ( size < 2 ||
+	     base[size-2] != YY_END_OF_BUFFER_CHAR ||
+	     base[size-1] != YY_END_OF_BUFFER_CHAR )
+		/* They forgot to leave room for the EOB's. */
+		return NULL;
+
+	b = (YY_BUFFER_STATE) yyalloc( sizeof( struct yy_buffer_state )  );
+	if ( ! b )
+		YY_FATAL_ERROR( "out of dynamic memory in yy_scan_buffer()" );
+
+	b->yy_buf_size = (int) (size - 2);	/* "- 2" to take care of EOB's */
+	b->yy_buf_pos = b->yy_ch_buf = base;
+	b->yy_is_our_buffer = 0;
+	b->yy_input_file = NULL;
+	b->yy_n_chars = b->yy_buf_size;
+	b->yy_is_interactive = 0;
+	b->yy_at_bol = 1;
+	b->yy_fill_buffer = 0;
+	b->yy_buffer_status = YY_BUFFER_NEW;
+
+	yy_switch_to_buffer( b  );
+
+	return b;
+}
+
+/** Setup the input buffer state to scan a string. The next call to yylex() will
+ * scan from a @e copy of @a str.
+ * @param yystr a NUL-terminated string to scan
+ * 
+ * @return the newly allocated buffer state object.
+ * @note If you want to scan bytes that may contain NUL values, then use
+ *       yy_scan_bytes() instead.
+ */
+YY_BUFFER_STATE yy_scan_string (const char * yystr )
+{
+    
+	return yy_scan_bytes( yystr, (int) strlen(yystr) );
+}
+
+/** Setup the input buffer state to scan the given bytes. The next call to yylex() will
+ * scan from a @e copy of @a bytes.
+ * @param yybytes the byte buffer to scan
+ * @param _yybytes_len the number of bytes in the buffer pointed to by @a bytes.
+ * 
+ * @return the newly allocated buffer state object.
+ */
+YY_BUFFER_STATE yy_scan_bytes  (const char * yybytes, int  _yybytes_len )
+{
+	YY_BUFFER_STATE b;
+	char *buf;
+	yy_size_t n;
+	int i;
+    
+	/* Get memory for full buffer, including space for trailing EOB's. */
+	n = (yy_size_t) (_yybytes_len + 2);
+	buf = (char *) yyalloc( n  );
+	if ( ! buf )
+		YY_FATAL_ERROR( "out of dynamic memory in yy_scan_bytes()" );
+
+	for ( i = 0; i < _yybytes_len; ++i )
+		buf[i] = yybytes[i];
+
+	buf[_yybytes_len] = buf[_yybytes_len+1] = YY_END_OF_BUFFER_CHAR;
+
+	b = yy_scan_buffer( buf, n );
+	if ( ! b )
+		YY_FATAL_ERROR( "bad buffer in yy_scan_bytes()" );
+
+	/* It's okay to grow etc. this buffer, and we should throw it
+	 * away when we're done.
+	 */
+	b->yy_is_our_buffer = 1;
+
+	return b;
+}
+
+#ifndef YY_EXIT_FAILURE
+#define YY_EXIT_FAILURE 2
+#endif
+
+static void yynoreturn yy_fatal_error (const char* msg )
+{
+			fprintf( stderr, "%s\n", msg );
+	exit( YY_EXIT_FAILURE );
+}
+
+/* Redefine yyless() so it works in section 3 code. */
+
+#undef yyless
+#define yyless(n) \
+	do \
+		{ \
+		/* Undo effects of setting up yytext. */ \
+        int yyless_macro_arg = (n); \
+        YY_LESS_LINENO(yyless_macro_arg);\
+		yytext[yyleng] = (yy_hold_char); \
+		(yy_c_buf_p) = yytext + yyless_macro_arg; \
+		(yy_hold_char) = *(yy_c_buf_p); \
+		*(yy_c_buf_p) = '\0'; \
+		yyleng = yyless_macro_arg; \
+		} \
+	while ( 0 )
+
+/* Accessor  methods (get/set functions) to struct members. */
+
+/** Get the current line number.
+ * 
+ */
+int yyget_lineno  (void)
+{
+    
+    return yylineno;
+}
+
+/** Get the input stream.
+ * 
+ */
+FILE *yyget_in  (void)
+{
+        return yyin;
+}
+
+/** Get the output stream.
+ * 
+ */
+FILE *yyget_out  (void)
+{
+        return yyout;
+}
+
+/** Get the length of the current token.
+ * 
+ */
+int yyget_leng  (void)
+{
+        return yyleng;
+}
+
+/** Get the current token.
+ * 
+ */
+
+char *yyget_text  (void)
+{
+        return yytext;
+}
+
+/** Set the current line number.
+ * @param _line_number line number
+ * 
+ */
+void yyset_lineno (int  _line_number )
+{
+    
+    yylineno = _line_number;
+}
+
+/** Set the input stream. This does not discard the current
+ * input buffer.
+ * @param _in_str A readable stream.
+ * 
+ * @see yy_switch_to_buffer
+ */
+void yyset_in (FILE *  _in_str )
+{
+        yyin = _in_str ;
+}
+
+void yyset_out (FILE *  _out_str )
+{
+        yyout = _out_str ;
+}
+
+int yyget_debug  (void)
+{
+        return yy_flex_debug;
+}
+
+void yyset_debug (int  _bdebug )
+{
+        yy_flex_debug = _bdebug ;
+}
+
+static int yy_init_globals (void)
+{
+        /* Initialization is the same as for the non-reentrant scanner.
+     * This function is called from yylex_destroy(), so don't allocate here.
+     */
+
+    (yy_buffer_stack) = NULL;
+    (yy_buffer_stack_top) = 0;
+    (yy_buffer_stack_max) = 0;
+    (yy_c_buf_p) = NULL;
+    (yy_init) = 0;
+    (yy_start) = 0;
+
+/* Defined in main.c */
+#ifdef YY_STDINIT
+    yyin = stdin;
+    yyout = stdout;
+#else
+    yyin = NULL;
+    yyout = NULL;
+#endif
+
+    /* For future reference: Set errno on error, since we are called by
+     * yylex_init()
+     */
+    return 0;
+}
+
+/* yylex_destroy is for both reentrant and non-reentrant scanners. */
+int yylex_destroy  (void)
+{
+    
+    /* Pop the buffer stack, destroying each element. */
+	while(YY_CURRENT_BUFFER){
+		yy_delete_buffer( YY_CURRENT_BUFFER  );
+		YY_CURRENT_BUFFER_LVALUE = NULL;
+		yypop_buffer_state();
+	}
+
+	/* Destroy the stack itself. */
+	yyfree((yy_buffer_stack) );
+	(yy_buffer_stack) = NULL;
+
+    /* Reset the globals. This is important in a non-reentrant scanner so the next time
+     * yylex() is called, initialization will occur. */
+    yy_init_globals( );
+
+    return 0;
+}
+
+/*
+ * Internal utility routines.
+ */
+
+#ifndef yytext_ptr
+static void yy_flex_strncpy (char* s1, const char * s2, int n )
+{
+		
+	int i;
+	for ( i = 0; i < n; ++i )
+		s1[i] = s2[i];
+}
+#endif
+
+#ifdef YY_NEED_STRLEN
+static int yy_flex_strlen (const char * s )
+{
+	int n;
+	for ( n = 0; s[n]; ++n )
+		;
+
+	return n;
+}
+#endif
+
+void *yyalloc (yy_size_t  size )
+{
+			return malloc(size);
+}
+
+void *yyrealloc  (void * ptr, yy_size_t  size )
+{
+		
+	/* The cast to (char *) in the following accommodates both
+	 * implementations that use char* generic pointers, and those
+	 * that use void* generic pointers.  It works with the latter
+	 * because both ANSI C and C++ allow castless assignment from
+	 * any pointer type to void*, and deal with argument conversions
+	 * as though doing an assignment.
+	 */
+	return realloc(ptr, size);
+}
+
+void yyfree (void * ptr )
+{
+			free( (char *) ptr );	/* see yyrealloc() for (char *) cast */
+}
+
+#define YYTABLES_NAME "yytables"
+
+#line 115 "syncrep_scanner.l"
+
+
+/* LCOV_EXCL_STOP */
+
+/* Needs to be here for access to yytext */
+void
+syncrep_yyerror(const char *message)
+{
+	/* report only the first error in a parse operation */
+	if (syncrep_parse_error_msg)
+		return;
+	if (yytext[0])
+		syncrep_parse_error_msg = psprintf("%s at or near \"%s\"",
+										   message, yytext);
+	else
+		syncrep_parse_error_msg = psprintf("%s at end of input",
+										   message);
+}
+
+void
+syncrep_scanner_init(const char *str)
+{
+	Size		slen = strlen(str);
+	char	   *scanbuf;
+
+	/*
+	 * Might be left over after ereport()
+	 */
+	if (YY_CURRENT_BUFFER)
+		yy_delete_buffer(YY_CURRENT_BUFFER);
+
+	/*
+	 * Make a scan buffer with special termination needed by flex.
+	 */
+	scanbuf = (char *) palloc(slen + 2);
+	memcpy(scanbuf, str, slen);
+	scanbuf[slen] = scanbuf[slen + 1] = YY_END_OF_BUFFER_CHAR;
+	scanbufhandle = yy_scan_buffer(scanbuf, slen + 2);
+
+	/* Make sure we start in proper state */
+	BEGIN(INITIAL);
+}
+
+void
+syncrep_scanner_finish(void)
+{
+	yy_delete_buffer(scanbufhandle);
+	scanbufhandle = NULL;
+}
+
diff --git a/src/backend/replication/syncrep_scanner.l b/src/backend/replication/syncrep_scanner.l
new file mode 100644
index 0000000..0491590
--- /dev/null
+++ b/src/backend/replication/syncrep_scanner.l
@@ -0,0 +1,163 @@
+%{
+/*-------------------------------------------------------------------------
+ *
+ * syncrep_scanner.l
+ *	  a lexical scanner for synchronous_standby_names
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/syncrep_scanner.l
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "lib/stringinfo.h"
+
+/* Avoid exit() on fatal scanner errors (a bit ugly -- see yy_fatal_error) */
+#undef fprintf
+#define fprintf(file, fmt, msg)  fprintf_to_ereport(fmt, msg)
+
+static void
+fprintf_to_ereport(const char *fmt, const char *msg)
+{
+	ereport(ERROR, (errmsg_internal("%s", msg)));
+}
+
+/* Handles to the buffer that the lexer uses internally */
+static YY_BUFFER_STATE scanbufhandle;
+
+static StringInfoData xdbuf;
+
+/* LCOV_EXCL_START */
+
+%}
+
+%option 8bit
+%option never-interactive
+%option nodefault
+%option noinput
+%option nounput
+%option noyywrap
+%option warn
+%option prefix="syncrep_yy"
+
+/*
+ * <xd> delimited identifiers (double-quoted identifiers)
+ */
+%x xd
+
+space			[ \t\n\r\f\v]
+
+digit			[0-9]
+ident_start		[A-Za-z\200-\377_]
+ident_cont		[A-Za-z\200-\377_0-9\$]
+identifier		{ident_start}{ident_cont}*
+
+dquote			\"
+xdstart			{dquote}
+xdstop			{dquote}
+xddouble		{dquote}{dquote}
+xdinside		[^"]+
+
+%%
+{space}+	{ /* ignore */ }
+
+	/* brute-force case insensitivity is safer than relying on flex -i */
+
+[Aa][Nn][Yy]			{ return ANY; }
+[Ff][Ii][Rr][Ss][Tt]	{ return FIRST; }
+
+{xdstart}	{
+				initStringInfo(&xdbuf);
+				BEGIN(xd);
+		}
+<xd>{xddouble} {
+				appendStringInfoChar(&xdbuf, '"');
+		}
+<xd>{xdinside} {
+				appendStringInfoString(&xdbuf, yytext);
+		}
+<xd>{xdstop} {
+				yylval.str = xdbuf.data;
+				xdbuf.data = NULL;
+				BEGIN(INITIAL);
+				return NAME;
+		}
+<xd><<EOF>> {
+				yyerror("unterminated quoted identifier");
+				return JUNK;
+		}
+
+{identifier} {
+				yylval.str = pstrdup(yytext);
+				return NAME;
+		}
+
+{digit}+	{
+				yylval.str = pstrdup(yytext);
+				return NUM;
+		}
+
+"*"		{
+				yylval.str = "*";
+				return NAME;
+		}
+
+","			{ return ','; }
+"("			{ return '('; }
+")"			{ return ')'; }
+
+.			{ return JUNK; }
+%%
+
+/* LCOV_EXCL_STOP */
+
+/* Needs to be here for access to yytext */
+void
+syncrep_yyerror(const char *message)
+{
+	/* report only the first error in a parse operation */
+	if (syncrep_parse_error_msg)
+		return;
+	if (yytext[0])
+		syncrep_parse_error_msg = psprintf("%s at or near \"%s\"",
+										   message, yytext);
+	else
+		syncrep_parse_error_msg = psprintf("%s at end of input",
+										   message);
+}
+
+void
+syncrep_scanner_init(const char *str)
+{
+	Size		slen = strlen(str);
+	char	   *scanbuf;
+
+	/*
+	 * Might be left over after ereport()
+	 */
+	if (YY_CURRENT_BUFFER)
+		yy_delete_buffer(YY_CURRENT_BUFFER);
+
+	/*
+	 * Make a scan buffer with special termination needed by flex.
+	 */
+	scanbuf = (char *) palloc(slen + 2);
+	memcpy(scanbuf, str, slen);
+	scanbuf[slen] = scanbuf[slen + 1] = YY_END_OF_BUFFER_CHAR;
+	scanbufhandle = yy_scan_buffer(scanbuf, slen + 2);
+
+	/* Make sure we start in proper state */
+	BEGIN(INITIAL);
+}
+
+void
+syncrep_scanner_finish(void)
+{
+	yy_delete_buffer(scanbufhandle);
+	scanbufhandle = NULL;
+}
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
new file mode 100644
index 0000000..4831a25
--- /dev/null
+++ b/src/backend/replication/walreceiver.c
@@ -0,0 +1,1460 @@
+/*-------------------------------------------------------------------------
+ *
+ * walreceiver.c
+ *
+ * The WAL receiver process (walreceiver) is new as of Postgres 9.0. It
+ * is the process in the standby server that takes charge of receiving
+ * XLOG records from a primary server during streaming replication.
+ *
+ * When the startup process determines that it's time to start streaming,
+ * it instructs postmaster to start walreceiver. Walreceiver first connects
+ * to the primary server (it will be served by a walsender process
+ * in the primary server), and then keeps receiving XLOG records and
+ * writing them to the disk as long as the connection is alive. As XLOG
+ * records are received and flushed to disk, it updates the
+ * WalRcv->flushedUpto variable in shared memory, to inform the startup
+ * process of how far it can proceed with XLOG replay.
+ *
+ * A WAL receiver cannot directly load GUC parameters used when establishing
+ * its connection to the primary. Instead it relies on parameter values
+ * that are passed down by the startup process when streaming is requested.
+ * This applies, for example, to the replication slot and the connection
+ * string to be used for the connection with the primary.
+ *
+ * If the primary server ends streaming, but doesn't disconnect, walreceiver
+ * goes into "waiting" mode, and waits for the startup process to give new
+ * instructions. The startup process will treat that the same as
+ * disconnection, and will rescan the archive/pg_wal directory. But when the
+ * startup process wants to try streaming replication again, it will just
+ * nudge the existing walreceiver process that's waiting, instead of launching
+ * a new one.
+ *
+ * Normal termination is by SIGTERM, which instructs the walreceiver to
+ * exit(0). Emergency termination is by SIGQUIT; like any postmaster child
+ * process, the walreceiver will simply abort and exit on SIGQUIT. A close
+ * of the connection and a FATAL error are treated not as a crash but as
+ * normal operation.
+ *
+ * This file contains the server-facing parts of walreceiver. The libpq-
+ * specific parts are in the libpqwalreceiver module. It's loaded
+ * dynamically to avoid linking the server with libpq.
+ *
+ * Portions Copyright (c) 2010-2021, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/walreceiver.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <unistd.h>
+
+#include "access/htup_details.h"
+#include "access/timeline.h"
+#include "access/transam.h"
+#include "access/xlog_internal.h"
+#include "access/xlogarchive.h"
+#include "catalog/pg_authid.h"
+#include "catalog/pg_type.h"
+#include "common/ip.h"
+#include "funcapi.h"
+#include "libpq/pqformat.h"
+#include "libpq/pqsignal.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "postmaster/interrupt.h"
+#include "replication/walreceiver.h"
+#include "replication/walsender.h"
+#include "storage/ipc.h"
+#include "storage/pmsignal.h"
+#include "storage/proc.h"
+#include "storage/procarray.h"
+#include "storage/procsignal.h"
+#include "utils/acl.h"
+#include "utils/builtins.h"
+#include "utils/guc.h"
+#include "utils/pg_lsn.h"
+#include "utils/ps_status.h"
+#include "utils/resowner.h"
+#include "utils/timestamp.h"
+
+
+/*
+ * GUC variables.  (Other variables that affect walreceiver are in xlog.c
+ * because they're passed down from the startup process, for better
+ * synchronization.)
+ */
+int			wal_receiver_status_interval;
+int			wal_receiver_timeout;
+bool		hot_standby_feedback;
+
+/* libpqwalreceiver connection */
+static WalReceiverConn *wrconn = NULL;
+WalReceiverFunctionsType *WalReceiverFunctions = NULL;
+
+#define NAPTIME_PER_CYCLE 100	/* max sleep time between cycles (100ms) */
+
+/*
+ * These variables are used similarly to openLogFile/SegNo,
+ * but for walreceiver to write the XLOG. recvFileTLI is the TimeLineID
+ * corresponding the filename of recvFile.
+ */
+static int	recvFile = -1;
+static TimeLineID recvFileTLI = 0;
+static XLogSegNo recvSegNo = 0;
+
+/*
+ * LogstreamResult indicates the byte positions that we have already
+ * written/fsynced.
+ */
+static struct
+{
+	XLogRecPtr	Write;			/* last byte + 1 written out in the standby */
+	XLogRecPtr	Flush;			/* last byte + 1 flushed in the standby */
+}			LogstreamResult;
+
+static StringInfoData reply_message;
+static StringInfoData incoming_message;
+
+/* Prototypes for private functions */
+static void WalRcvFetchTimeLineHistoryFiles(TimeLineID first, TimeLineID last);
+static void WalRcvWaitForStartPosition(XLogRecPtr *startpoint, TimeLineID *startpointTLI);
+static void WalRcvDie(int code, Datum arg);
+static void XLogWalRcvProcessMsg(unsigned char type, char *buf, Size len);
+static void XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr);
+static void XLogWalRcvFlush(bool dying);
+static void XLogWalRcvClose(XLogRecPtr recptr);
+static void XLogWalRcvSendReply(bool force, bool requestReply);
+static void XLogWalRcvSendHSFeedback(bool immed);
+static void ProcessWalSndrMessage(XLogRecPtr walEnd, TimestampTz sendTime);
+
+/*
+ * Process any interrupts the walreceiver process may have received.
+ * This should be called any time the process's latch has become set.
+ *
+ * Currently, only SIGTERM is of interest.  We can't just exit(1) within the
+ * SIGTERM signal handler, because the signal might arrive in the middle of
+ * some critical operation, like while we're holding a spinlock.  Instead, the
+ * signal handler sets a flag variable as well as setting the process's latch.
+ * We must check the flag (by calling ProcessWalRcvInterrupts) anytime the
+ * latch has become set.  Operations that could block for a long time, such as
+ * reading from a remote server, must pay attention to the latch too; see
+ * libpqrcv_PQgetResult for example.
+ */
+void
+ProcessWalRcvInterrupts(void)
+{
+	/*
+	 * Although walreceiver interrupt handling doesn't use the same scheme as
+	 * regular backends, call CHECK_FOR_INTERRUPTS() to make sure we receive
+	 * any incoming signals on Win32, and also to make sure we process any
+	 * barrier events.
+	 */
+	CHECK_FOR_INTERRUPTS();
+
+	if (ShutdownRequestPending)
+	{
+		ereport(FATAL,
+				(errcode(ERRCODE_ADMIN_SHUTDOWN),
+				 errmsg("terminating walreceiver process due to administrator command")));
+	}
+}
+
+
+/* Main entry point for walreceiver process */
+void
+WalReceiverMain(void)
+{
+	char		conninfo[MAXCONNINFO];
+	char	   *tmp_conninfo;
+	char		slotname[NAMEDATALEN];
+	bool		is_temp_slot;
+	XLogRecPtr	startpoint;
+	TimeLineID	startpointTLI;
+	TimeLineID	primaryTLI;
+	bool		first_stream;
+	WalRcvData *walrcv = WalRcv;
+	TimestampTz last_recv_timestamp;
+	TimestampTz now;
+	bool		ping_sent;
+	char	   *err;
+	char	   *sender_host = NULL;
+	int			sender_port = 0;
+
+	/*
+	 * WalRcv should be set up already (if we are a backend, we inherit this
+	 * by fork() or EXEC_BACKEND mechanism from the postmaster).
+	 */
+	Assert(walrcv != NULL);
+
+	now = GetCurrentTimestamp();
+
+	/*
+	 * Mark walreceiver as running in shared memory.
+	 *
+	 * Do this as early as possible, so that if we fail later on, we'll set
+	 * state to STOPPED. If we die before this, the startup process will keep
+	 * waiting for us to start up, until it times out.
+	 */
+	SpinLockAcquire(&walrcv->mutex);
+	Assert(walrcv->pid == 0);
+	switch (walrcv->walRcvState)
+	{
+		case WALRCV_STOPPING:
+			/* If we've already been requested to stop, don't start up. */
+			walrcv->walRcvState = WALRCV_STOPPED;
+			/* fall through */
+
+		case WALRCV_STOPPED:
+			SpinLockRelease(&walrcv->mutex);
+			ConditionVariableBroadcast(&walrcv->walRcvStoppedCV);
+			proc_exit(1);
+			break;
+
+		case WALRCV_STARTING:
+			/* The usual case */
+			break;
+
+		case WALRCV_WAITING:
+		case WALRCV_STREAMING:
+		case WALRCV_RESTARTING:
+		default:
+			/* Shouldn't happen */
+			SpinLockRelease(&walrcv->mutex);
+			elog(PANIC, "walreceiver still running according to shared memory state");
+	}
+	/* Advertise our PID so that the startup process can kill us */
+	walrcv->pid = MyProcPid;
+	walrcv->walRcvState = WALRCV_STREAMING;
+
+	/* Fetch information required to start streaming */
+	walrcv->ready_to_display = false;
+	strlcpy(conninfo, (char *) walrcv->conninfo, MAXCONNINFO);
+	strlcpy(slotname, (char *) walrcv->slotname, NAMEDATALEN);
+	is_temp_slot = walrcv->is_temp_slot;
+	startpoint = walrcv->receiveStart;
+	startpointTLI = walrcv->receiveStartTLI;
+
+	/*
+	 * At most one of is_temp_slot and slotname can be set; otherwise,
+	 * RequestXLogStreaming messed up.
+	 */
+	Assert(!is_temp_slot || (slotname[0] == '\0'));
+
+	/* Initialise to a sanish value */
+	walrcv->lastMsgSendTime =
+		walrcv->lastMsgReceiptTime = walrcv->latestWalEndTime = now;
+
+	/* Report the latch to use to awaken this process */
+	walrcv->latch = &MyProc->procLatch;
+
+	SpinLockRelease(&walrcv->mutex);
+
+	pg_atomic_write_u64(&WalRcv->writtenUpto, 0);
+
+	/* Arrange to clean up at walreceiver exit */
+	on_shmem_exit(WalRcvDie, 0);
+
+	/* Properly accept or ignore signals the postmaster might send us */
+	pqsignal(SIGHUP, SignalHandlerForConfigReload); /* set flag to read config
+													 * file */
+	pqsignal(SIGINT, SIG_IGN);
+	pqsignal(SIGTERM, SignalHandlerForShutdownRequest); /* request shutdown */
+	/* SIGQUIT handler was already set up by InitPostmasterChild */
+	pqsignal(SIGALRM, SIG_IGN);
+	pqsignal(SIGPIPE, SIG_IGN);
+	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
+	pqsignal(SIGUSR2, SIG_IGN);
+
+	/* Reset some signals that are accepted by postmaster but not here */
+	pqsignal(SIGCHLD, SIG_DFL);
+
+	/* Load the libpq-specific functions */
+	load_file("libpqwalreceiver", false);
+	if (WalReceiverFunctions == NULL)
+		elog(ERROR, "libpqwalreceiver didn't initialize correctly");
+
+	/* Unblock signals (they were blocked when the postmaster forked us) */
+	PG_SETMASK(&UnBlockSig);
+
+	/* Establish the connection to the primary for XLOG streaming */
+	wrconn = walrcv_connect(conninfo, false,
+							cluster_name[0] ? cluster_name : "walreceiver",
+							&err);
+	if (!wrconn)
+		ereport(ERROR,
+				(errcode(ERRCODE_CONNECTION_FAILURE),
+				 errmsg("could not connect to the primary server: %s", err)));
+
+	/*
+	 * Save user-visible connection string.  This clobbers the original
+	 * conninfo, for security. Also save host and port of the sender server
+	 * this walreceiver is connected to.
+	 */
+	tmp_conninfo = walrcv_get_conninfo(wrconn);
+	walrcv_get_senderinfo(wrconn, &sender_host, &sender_port);
+	SpinLockAcquire(&walrcv->mutex);
+	memset(walrcv->conninfo, 0, MAXCONNINFO);
+	if (tmp_conninfo)
+		strlcpy((char *) walrcv->conninfo, tmp_conninfo, MAXCONNINFO);
+
+	memset(walrcv->sender_host, 0, NI_MAXHOST);
+	if (sender_host)
+		strlcpy((char *) walrcv->sender_host, sender_host, NI_MAXHOST);
+
+	walrcv->sender_port = sender_port;
+	walrcv->ready_to_display = true;
+	SpinLockRelease(&walrcv->mutex);
+
+	if (tmp_conninfo)
+		pfree(tmp_conninfo);
+
+	if (sender_host)
+		pfree(sender_host);
+
+	first_stream = true;
+	for (;;)
+	{
+		char	   *primary_sysid;
+		char		standby_sysid[32];
+		WalRcvStreamOptions options;
+
+		/*
+		 * Check that we're connected to a valid server using the
+		 * IDENTIFY_SYSTEM replication command.
+		 */
+		primary_sysid = walrcv_identify_system(wrconn, &primaryTLI);
+
+		snprintf(standby_sysid, sizeof(standby_sysid), UINT64_FORMAT,
+				 GetSystemIdentifier());
+		if (strcmp(primary_sysid, standby_sysid) != 0)
+		{
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					 errmsg("database system identifier differs between the primary and standby"),
+					 errdetail("The primary's identifier is %s, the standby's identifier is %s.",
+							   primary_sysid, standby_sysid)));
+		}
+
+		/*
+		 * Confirm that the current timeline of the primary is the same or
+		 * ahead of ours.
+		 */
+		if (primaryTLI < startpointTLI)
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					 errmsg("highest timeline %u of the primary is behind recovery timeline %u",
+							primaryTLI, startpointTLI)));
+
+		/*
+		 * Get any missing history files. We do this always, even when we're
+		 * not interested in that timeline, so that if we're promoted to
+		 * become the primary later on, we don't select the same timeline that
+		 * was already used in the current primary. This isn't bullet-proof -
+		 * you'll need some external software to manage your cluster if you
+		 * need to ensure that a unique timeline id is chosen in every case,
+		 * but let's avoid the confusion of timeline id collisions where we
+		 * can.
+		 */
+		WalRcvFetchTimeLineHistoryFiles(startpointTLI, primaryTLI);
+
+		/*
+		 * Create temporary replication slot if requested, and update slot
+		 * name in shared memory.  (Note the slot name cannot already be set
+		 * in this case.)
+		 */
+		if (is_temp_slot)
+		{
+			snprintf(slotname, sizeof(slotname),
+					 "pg_walreceiver_%lld",
+					 (long long int) walrcv_get_backend_pid(wrconn));
+
+			walrcv_create_slot(wrconn, slotname, true, 0, NULL);
+
+			SpinLockAcquire(&walrcv->mutex);
+			strlcpy(walrcv->slotname, slotname, NAMEDATALEN);
+			SpinLockRelease(&walrcv->mutex);
+		}
+
+		/*
+		 * Start streaming.
+		 *
+		 * We'll try to start at the requested starting point and timeline,
+		 * even if it's different from the server's latest timeline. In case
+		 * we've already reached the end of the old timeline, the server will
+		 * finish the streaming immediately, and we will go back to await
+		 * orders from the startup process. If recovery_target_timeline is
+		 * 'latest', the startup process will scan pg_wal and find the new
+		 * history file, bump recovery target timeline, and ask us to restart
+		 * on the new timeline.
+		 */
+		options.logical = false;
+		options.startpoint = startpoint;
+		options.slotname = slotname[0] != '\0' ? slotname : NULL;
+		options.proto.physical.startpointTLI = startpointTLI;
+		ThisTimeLineID = startpointTLI;
+		if (walrcv_startstreaming(wrconn, &options))
+		{
+			if (first_stream)
+				ereport(LOG,
+						(errmsg("started streaming WAL from primary at %X/%X on timeline %u",
+								LSN_FORMAT_ARGS(startpoint), startpointTLI)));
+			else
+				ereport(LOG,
+						(errmsg("restarted WAL streaming at %X/%X on timeline %u",
+								LSN_FORMAT_ARGS(startpoint), startpointTLI)));
+			first_stream = false;
+
+			/* Initialize LogstreamResult and buffers for processing messages */
+			LogstreamResult.Write = LogstreamResult.Flush = GetXLogReplayRecPtr(NULL);
+			initStringInfo(&reply_message);
+			initStringInfo(&incoming_message);
+
+			/* Initialize the last recv timestamp */
+			last_recv_timestamp = GetCurrentTimestamp();
+			ping_sent = false;
+
+			/* Loop until end-of-streaming or error */
+			for (;;)
+			{
+				char	   *buf;
+				int			len;
+				bool		endofwal = false;
+				pgsocket	wait_fd = PGINVALID_SOCKET;
+				int			rc;
+
+				/*
+				 * Exit walreceiver if we're not in recovery. This should not
+				 * happen, but cross-check the status here.
+				 */
+				if (!RecoveryInProgress())
+					ereport(FATAL,
+							(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+							 errmsg("cannot continue WAL streaming, recovery has already ended")));
+
+				/* Process any requests or signals received recently */
+				ProcessWalRcvInterrupts();
+
+				if (ConfigReloadPending)
+				{
+					ConfigReloadPending = false;
+					ProcessConfigFile(PGC_SIGHUP);
+					XLogWalRcvSendHSFeedback(true);
+				}
+
+				/* See if we can read data immediately */
+				len = walrcv_receive(wrconn, &buf, &wait_fd);
+				if (len != 0)
+				{
+					/*
+					 * Process the received data, and any subsequent data we
+					 * can read without blocking.
+					 */
+					for (;;)
+					{
+						if (len > 0)
+						{
+							/*
+							 * Something was received from primary, so reset
+							 * timeout
+							 */
+							last_recv_timestamp = GetCurrentTimestamp();
+							ping_sent = false;
+							XLogWalRcvProcessMsg(buf[0], &buf[1], len - 1);
+						}
+						else if (len == 0)
+							break;
+						else if (len < 0)
+						{
+							ereport(LOG,
+									(errmsg("replication terminated by primary server"),
+									 errdetail("End of WAL reached on timeline %u at %X/%X.",
+											   startpointTLI,
+											   LSN_FORMAT_ARGS(LogstreamResult.Write))));
+							endofwal = true;
+							break;
+						}
+						len = walrcv_receive(wrconn, &buf, &wait_fd);
+					}
+
+					/* Let the primary know that we received some data. */
+					XLogWalRcvSendReply(false, false);
+
+					/*
+					 * If we've written some records, flush them to disk and
+					 * let the startup process and primary server know about
+					 * them.
+					 */
+					XLogWalRcvFlush(false);
+				}
+
+				/* Check if we need to exit the streaming loop. */
+				if (endofwal)
+					break;
+
+				/*
+				 * Ideally we would reuse a WaitEventSet object repeatedly
+				 * here to avoid the overheads of WaitLatchOrSocket on epoll
+				 * systems, but we can't be sure that libpq (or any other
+				 * walreceiver implementation) has the same socket (even if
+				 * the fd is the same number, it may have been closed and
+				 * reopened since the last time).  In future, if there is a
+				 * function for removing sockets from WaitEventSet, then we
+				 * could add and remove just the socket each time, potentially
+				 * avoiding some system calls.
+				 */
+				Assert(wait_fd != PGINVALID_SOCKET);
+				rc = WaitLatchOrSocket(MyLatch,
+									   WL_EXIT_ON_PM_DEATH | WL_SOCKET_READABLE |
+									   WL_TIMEOUT | WL_LATCH_SET,
+									   wait_fd,
+									   NAPTIME_PER_CYCLE,
+									   WAIT_EVENT_WAL_RECEIVER_MAIN);
+				if (rc & WL_LATCH_SET)
+				{
+					ResetLatch(MyLatch);
+					ProcessWalRcvInterrupts();
+
+					if (walrcv->force_reply)
+					{
+						/*
+						 * The recovery process has asked us to send apply
+						 * feedback now.  Make sure the flag is really set to
+						 * false in shared memory before sending the reply, so
+						 * we don't miss a new request for a reply.
+						 */
+						walrcv->force_reply = false;
+						pg_memory_barrier();
+						XLogWalRcvSendReply(true, false);
+					}
+				}
+				if (rc & WL_TIMEOUT)
+				{
+					/*
+					 * We didn't receive anything new. If we haven't heard
+					 * anything from the server for more than
+					 * wal_receiver_timeout / 2, ping the server. Also, if
+					 * it's been longer than wal_receiver_status_interval
+					 * since the last update we sent, send a status update to
+					 * the primary anyway, to report any progress in applying
+					 * WAL.
+					 */
+					bool		requestReply = false;
+
+					/*
+					 * Check if time since last receive from primary has
+					 * reached the configured limit.
+					 */
+					if (wal_receiver_timeout > 0)
+					{
+						TimestampTz now = GetCurrentTimestamp();
+						TimestampTz timeout;
+
+						timeout =
+							TimestampTzPlusMilliseconds(last_recv_timestamp,
+														wal_receiver_timeout);
+
+						if (now >= timeout)
+							ereport(ERROR,
+									(errcode(ERRCODE_CONNECTION_FAILURE),
+									 errmsg("terminating walreceiver due to timeout")));
+
+						/*
+						 * We didn't receive anything new, for half of
+						 * receiver replication timeout. Ping the server.
+						 */
+						if (!ping_sent)
+						{
+							timeout = TimestampTzPlusMilliseconds(last_recv_timestamp,
+																  (wal_receiver_timeout / 2));
+							if (now >= timeout)
+							{
+								requestReply = true;
+								ping_sent = true;
+							}
+						}
+					}
+
+					XLogWalRcvSendReply(requestReply, requestReply);
+					XLogWalRcvSendHSFeedback(false);
+				}
+			}
+
+			/*
+			 * The backend finished streaming. Exit streaming COPY-mode from
+			 * our side, too.
+			 */
+			walrcv_endstreaming(wrconn, &primaryTLI);
+
+			/*
+			 * If the server had switched to a new timeline that we didn't
+			 * know about when we began streaming, fetch its timeline history
+			 * file now.
+			 */
+			WalRcvFetchTimeLineHistoryFiles(startpointTLI, primaryTLI);
+		}
+		else
+			ereport(LOG,
+					(errmsg("primary server contains no more WAL on requested timeline %u",
+							startpointTLI)));
+
+		/*
+		 * End of WAL reached on the requested timeline. Close the last
+		 * segment, and await for new orders from the startup process.
+		 */
+		if (recvFile >= 0)
+		{
+			char		xlogfname[MAXFNAMELEN];
+
+			XLogWalRcvFlush(false);
+			XLogFileName(xlogfname, recvFileTLI, recvSegNo, wal_segment_size);
+			if (close(recvFile) != 0)
+				ereport(PANIC,
+						(errcode_for_file_access(),
+						 errmsg("could not close log segment %s: %m",
+								xlogfname)));
+
+			/*
+			 * Create .done file forcibly to prevent the streamed segment from
+			 * being archived later.
+			 */
+			if (XLogArchiveMode != ARCHIVE_MODE_ALWAYS)
+				XLogArchiveForceDone(xlogfname);
+			else
+				XLogArchiveNotify(xlogfname);
+		}
+		recvFile = -1;
+
+		elog(DEBUG1, "walreceiver ended streaming and awaits new instructions");
+		WalRcvWaitForStartPosition(&startpoint, &startpointTLI);
+	}
+	/* not reached */
+}
+
+/*
+ * Wait for startup process to set receiveStart and receiveStartTLI.
+ */
+static void
+WalRcvWaitForStartPosition(XLogRecPtr *startpoint, TimeLineID *startpointTLI)
+{
+	WalRcvData *walrcv = WalRcv;
+	int			state;
+
+	SpinLockAcquire(&walrcv->mutex);
+	state = walrcv->walRcvState;
+	if (state != WALRCV_STREAMING)
+	{
+		SpinLockRelease(&walrcv->mutex);
+		if (state == WALRCV_STOPPING)
+			proc_exit(0);
+		else
+			elog(FATAL, "unexpected walreceiver state");
+	}
+	walrcv->walRcvState = WALRCV_WAITING;
+	walrcv->receiveStart = InvalidXLogRecPtr;
+	walrcv->receiveStartTLI = 0;
+	SpinLockRelease(&walrcv->mutex);
+
+	set_ps_display("idle");
+
+	/*
+	 * nudge startup process to notice that we've stopped streaming and are
+	 * now waiting for instructions.
+	 */
+	WakeupRecovery();
+	for (;;)
+	{
+		ResetLatch(MyLatch);
+
+		ProcessWalRcvInterrupts();
+
+		SpinLockAcquire(&walrcv->mutex);
+		Assert(walrcv->walRcvState == WALRCV_RESTARTING ||
+			   walrcv->walRcvState == WALRCV_WAITING ||
+			   walrcv->walRcvState == WALRCV_STOPPING);
+		if (walrcv->walRcvState == WALRCV_RESTARTING)
+		{
+			/*
+			 * No need to handle changes in primary_conninfo or
+			 * primary_slotname here. Startup process will signal us to
+			 * terminate in case those change.
+			 */
+			*startpoint = walrcv->receiveStart;
+			*startpointTLI = walrcv->receiveStartTLI;
+			walrcv->walRcvState = WALRCV_STREAMING;
+			SpinLockRelease(&walrcv->mutex);
+			break;
+		}
+		if (walrcv->walRcvState == WALRCV_STOPPING)
+		{
+			/*
+			 * We should've received SIGTERM if the startup process wants us
+			 * to die, but might as well check it here too.
+			 */
+			SpinLockRelease(&walrcv->mutex);
+			exit(1);
+		}
+		SpinLockRelease(&walrcv->mutex);
+
+		(void) WaitLatch(MyLatch, WL_LATCH_SET | WL_EXIT_ON_PM_DEATH, 0,
+						 WAIT_EVENT_WAL_RECEIVER_WAIT_START);
+	}
+
+	if (update_process_title)
+	{
+		char		activitymsg[50];
+
+		snprintf(activitymsg, sizeof(activitymsg), "restarting at %X/%X",
+				 LSN_FORMAT_ARGS(*startpoint));
+		set_ps_display(activitymsg);
+	}
+}
+
+/*
+ * Fetch any missing timeline history files between 'first' and 'last'
+ * (inclusive) from the server.
+ */
+static void
+WalRcvFetchTimeLineHistoryFiles(TimeLineID first, TimeLineID last)
+{
+	TimeLineID	tli;
+
+	for (tli = first; tli <= last; tli++)
+	{
+		/* there's no history file for timeline 1 */
+		if (tli != 1 && !existsTimeLineHistory(tli))
+		{
+			char	   *fname;
+			char	   *content;
+			int			len;
+			char		expectedfname[MAXFNAMELEN];
+
+			ereport(LOG,
+					(errmsg("fetching timeline history file for timeline %u from primary server",
+							tli)));
+
+			walrcv_readtimelinehistoryfile(wrconn, tli, &fname, &content, &len);
+
+			/*
+			 * Check that the filename on the primary matches what we
+			 * calculated ourselves. This is just a sanity check, it should
+			 * always match.
+			 */
+			TLHistoryFileName(expectedfname, tli);
+			if (strcmp(fname, expectedfname) != 0)
+				ereport(ERROR,
+						(errcode(ERRCODE_PROTOCOL_VIOLATION),
+						 errmsg_internal("primary reported unexpected file name for timeline history file of timeline %u",
+										 tli)));
+
+			/*
+			 * Write the file to pg_wal.
+			 */
+			writeTimeLineHistoryFile(tli, content, len);
+
+			/*
+			 * Mark the streamed history file as ready for archiving if
+			 * archive_mode is always.
+			 */
+			if (XLogArchiveMode != ARCHIVE_MODE_ALWAYS)
+				XLogArchiveForceDone(fname);
+			else
+				XLogArchiveNotify(fname);
+
+			pfree(fname);
+			pfree(content);
+		}
+	}
+}
+
+/*
+ * Mark us as STOPPED in shared memory at exit.
+ */
+static void
+WalRcvDie(int code, Datum arg)
+{
+	WalRcvData *walrcv = WalRcv;
+
+	/* Ensure that all WAL records received are flushed to disk */
+	XLogWalRcvFlush(true);
+
+	/* Mark ourselves inactive in shared memory */
+	SpinLockAcquire(&walrcv->mutex);
+	Assert(walrcv->walRcvState == WALRCV_STREAMING ||
+		   walrcv->walRcvState == WALRCV_RESTARTING ||
+		   walrcv->walRcvState == WALRCV_STARTING ||
+		   walrcv->walRcvState == WALRCV_WAITING ||
+		   walrcv->walRcvState == WALRCV_STOPPING);
+	Assert(walrcv->pid == MyProcPid);
+	walrcv->walRcvState = WALRCV_STOPPED;
+	walrcv->pid = 0;
+	walrcv->ready_to_display = false;
+	walrcv->latch = NULL;
+	SpinLockRelease(&walrcv->mutex);
+
+	ConditionVariableBroadcast(&walrcv->walRcvStoppedCV);
+
+	/* Terminate the connection gracefully. */
+	if (wrconn != NULL)
+		walrcv_disconnect(wrconn);
+
+	/* Wake up the startup process to notice promptly that we're gone */
+	WakeupRecovery();
+}
+
+/*
+ * Accept the message from XLOG stream, and process it.
+ */
+static void
+XLogWalRcvProcessMsg(unsigned char type, char *buf, Size len)
+{
+	int			hdrlen;
+	XLogRecPtr	dataStart;
+	XLogRecPtr	walEnd;
+	TimestampTz sendTime;
+	bool		replyRequested;
+
+	resetStringInfo(&incoming_message);
+
+	switch (type)
+	{
+		case 'w':				/* WAL records */
+			{
+				/* copy message to StringInfo */
+				hdrlen = sizeof(int64) + sizeof(int64) + sizeof(int64);
+				if (len < hdrlen)
+					ereport(ERROR,
+							(errcode(ERRCODE_PROTOCOL_VIOLATION),
+							 errmsg_internal("invalid WAL message received from primary")));
+				appendBinaryStringInfo(&incoming_message, buf, hdrlen);
+
+				/* read the fields */
+				dataStart = pq_getmsgint64(&incoming_message);
+				walEnd = pq_getmsgint64(&incoming_message);
+				sendTime = pq_getmsgint64(&incoming_message);
+				ProcessWalSndrMessage(walEnd, sendTime);
+
+				buf += hdrlen;
+				len -= hdrlen;
+				XLogWalRcvWrite(buf, len, dataStart);
+				break;
+			}
+		case 'k':				/* Keepalive */
+			{
+				/* copy message to StringInfo */
+				hdrlen = sizeof(int64) + sizeof(int64) + sizeof(char);
+				if (len != hdrlen)
+					ereport(ERROR,
+							(errcode(ERRCODE_PROTOCOL_VIOLATION),
+							 errmsg_internal("invalid keepalive message received from primary")));
+				appendBinaryStringInfo(&incoming_message, buf, hdrlen);
+
+				/* read the fields */
+				walEnd = pq_getmsgint64(&incoming_message);
+				sendTime = pq_getmsgint64(&incoming_message);
+				replyRequested = pq_getmsgbyte(&incoming_message);
+
+				ProcessWalSndrMessage(walEnd, sendTime);
+
+				/* If the primary requested a reply, send one immediately */
+				if (replyRequested)
+					XLogWalRcvSendReply(true, false);
+				break;
+			}
+		default:
+			ereport(ERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg_internal("invalid replication message type %d",
+									 type)));
+	}
+}
+
+/*
+ * Write XLOG data to disk.
+ */
+static void
+XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr)
+{
+	int			startoff;
+	int			byteswritten;
+
+	while (nbytes > 0)
+	{
+		int			segbytes;
+
+		/* Close the current segment if it's completed */
+		if (recvFile >= 0 && !XLByteInSeg(recptr, recvSegNo, wal_segment_size))
+			XLogWalRcvClose(recptr);
+
+		if (recvFile < 0)
+		{
+			bool		use_existent = true;
+
+			/* Create/use new log file */
+			XLByteToSeg(recptr, recvSegNo, wal_segment_size);
+			recvFile = XLogFileInit(recvSegNo, &use_existent, true);
+			recvFileTLI = ThisTimeLineID;
+		}
+
+		/* Calculate the start offset of the received logs */
+		startoff = XLogSegmentOffset(recptr, wal_segment_size);
+
+		if (startoff + nbytes > wal_segment_size)
+			segbytes = wal_segment_size - startoff;
+		else
+			segbytes = nbytes;
+
+		/* OK to write the logs */
+		errno = 0;
+
+		byteswritten = pg_pwrite(recvFile, buf, segbytes, (off_t) startoff);
+		if (byteswritten <= 0)
+		{
+			char		xlogfname[MAXFNAMELEN];
+			int			save_errno;
+
+			/* if write didn't set errno, assume no disk space */
+			if (errno == 0)
+				errno = ENOSPC;
+
+			save_errno = errno;
+			XLogFileName(xlogfname, recvFileTLI, recvSegNo, wal_segment_size);
+			errno = save_errno;
+			ereport(PANIC,
+					(errcode_for_file_access(),
+					 errmsg("could not write to log segment %s "
+							"at offset %u, length %lu: %m",
+							xlogfname, startoff, (unsigned long) segbytes)));
+		}
+
+		/* Update state for write */
+		recptr += byteswritten;
+
+		nbytes -= byteswritten;
+		buf += byteswritten;
+
+		LogstreamResult.Write = recptr;
+	}
+
+	/* Update shared-memory status */
+	pg_atomic_write_u64(&WalRcv->writtenUpto, LogstreamResult.Write);
+
+	/*
+	 * Close the current segment if it's fully written up in the last cycle of
+	 * the loop, to create its archive notification file soon. Otherwise WAL
+	 * archiving of the segment will be delayed until any data in the next
+	 * segment is received and written.
+	 */
+	if (recvFile >= 0 && !XLByteInSeg(recptr, recvSegNo, wal_segment_size))
+		XLogWalRcvClose(recptr);
+}
+
+/*
+ * Flush the log to disk.
+ *
+ * If we're in the midst of dying, it's unwise to do anything that might throw
+ * an error, so we skip sending a reply in that case.
+ */
+static void
+XLogWalRcvFlush(bool dying)
+{
+	if (LogstreamResult.Flush < LogstreamResult.Write)
+	{
+		WalRcvData *walrcv = WalRcv;
+
+		issue_xlog_fsync(recvFile, recvSegNo);
+
+		LogstreamResult.Flush = LogstreamResult.Write;
+
+		/* Update shared-memory status */
+		SpinLockAcquire(&walrcv->mutex);
+		if (walrcv->flushedUpto < LogstreamResult.Flush)
+		{
+			walrcv->latestChunkStart = walrcv->flushedUpto;
+			walrcv->flushedUpto = LogstreamResult.Flush;
+			walrcv->receivedTLI = ThisTimeLineID;
+		}
+		SpinLockRelease(&walrcv->mutex);
+
+		/* Signal the startup process and walsender that new WAL has arrived */
+		WakeupRecovery();
+		if (AllowCascadeReplication())
+			WalSndWakeup();
+
+		/* Report XLOG streaming progress in PS display */
+		if (update_process_title)
+		{
+			char		activitymsg[50];
+
+			snprintf(activitymsg, sizeof(activitymsg), "streaming %X/%X",
+					 LSN_FORMAT_ARGS(LogstreamResult.Write));
+			set_ps_display(activitymsg);
+		}
+
+		/* Also let the primary know that we made some progress */
+		if (!dying)
+		{
+			XLogWalRcvSendReply(false, false);
+			XLogWalRcvSendHSFeedback(false);
+		}
+	}
+}
+
+/*
+ * Close the current segment.
+ *
+ * Flush the segment to disk before closing it. Otherwise we have to
+ * reopen and fsync it later.
+ *
+ * Create an archive notification file since the segment is known completed.
+ */
+static void
+XLogWalRcvClose(XLogRecPtr recptr)
+{
+	char		xlogfname[MAXFNAMELEN];
+
+	Assert(recvFile >= 0 && !XLByteInSeg(recptr, recvSegNo, wal_segment_size));
+
+	/*
+	 * fsync() and close current file before we switch to next one. We would
+	 * otherwise have to reopen this file to fsync it later
+	 */
+	XLogWalRcvFlush(false);
+
+	XLogFileName(xlogfname, recvFileTLI, recvSegNo, wal_segment_size);
+
+	/*
+	 * XLOG segment files will be re-read by recovery in startup process soon,
+	 * so we don't advise the OS to release cache pages associated with the
+	 * file like XLogFileClose() does.
+	 */
+	if (close(recvFile) != 0)
+		ereport(PANIC,
+				(errcode_for_file_access(),
+				 errmsg("could not close log segment %s: %m",
+						xlogfname)));
+
+	/*
+	 * Create .done file forcibly to prevent the streamed segment from being
+	 * archived later.
+	 */
+	if (XLogArchiveMode != ARCHIVE_MODE_ALWAYS)
+		XLogArchiveForceDone(xlogfname);
+	else
+		XLogArchiveNotify(xlogfname);
+
+	recvFile = -1;
+}
+
+/*
+ * Send reply message to primary, indicating our current WAL locations, oldest
+ * xmin and the current time.
+ *
+ * If 'force' is not set, the message is only sent if enough time has
+ * passed since last status update to reach wal_receiver_status_interval.
+ * If wal_receiver_status_interval is disabled altogether and 'force' is
+ * false, this is a no-op.
+ *
+ * If 'requestReply' is true, requests the server to reply immediately upon
+ * receiving this message. This is used for heartbeats, when approaching
+ * wal_receiver_timeout.
+ */
+static void
+XLogWalRcvSendReply(bool force, bool requestReply)
+{
+	static XLogRecPtr writePtr = 0;
+	static XLogRecPtr flushPtr = 0;
+	XLogRecPtr	applyPtr;
+	static TimestampTz sendTime = 0;
+	TimestampTz now;
+
+	/*
+	 * If the user doesn't want status to be reported to the primary, be sure
+	 * to exit before doing anything at all.
+	 */
+	if (!force && wal_receiver_status_interval <= 0)
+		return;
+
+	/* Get current timestamp. */
+	now = GetCurrentTimestamp();
+
+	/*
+	 * We can compare the write and flush positions to the last message we
+	 * sent without taking any lock, but the apply position requires a spin
+	 * lock, so we don't check that unless something else has changed or 10
+	 * seconds have passed.  This means that the apply WAL location will
+	 * appear, from the primary's point of view, to lag slightly, but since
+	 * this is only for reporting purposes and only on idle systems, that's
+	 * probably OK.
+	 */
+	if (!force
+		&& writePtr == LogstreamResult.Write
+		&& flushPtr == LogstreamResult.Flush
+		&& !TimestampDifferenceExceeds(sendTime, now,
+									   wal_receiver_status_interval * 1000))
+		return;
+	sendTime = now;
+
+	/* Construct a new message */
+	writePtr = LogstreamResult.Write;
+	flushPtr = LogstreamResult.Flush;
+	applyPtr = GetXLogReplayRecPtr(NULL);
+
+	resetStringInfo(&reply_message);
+	pq_sendbyte(&reply_message, 'r');
+	pq_sendint64(&reply_message, writePtr);
+	pq_sendint64(&reply_message, flushPtr);
+	pq_sendint64(&reply_message, applyPtr);
+	pq_sendint64(&reply_message, GetCurrentTimestamp());
+	pq_sendbyte(&reply_message, requestReply ? 1 : 0);
+
+	/* Send it */
+	elog(DEBUG2, "sending write %X/%X flush %X/%X apply %X/%X%s",
+		 LSN_FORMAT_ARGS(writePtr),
+		 LSN_FORMAT_ARGS(flushPtr),
+		 LSN_FORMAT_ARGS(applyPtr),
+		 requestReply ? " (reply requested)" : "");
+
+	walrcv_send(wrconn, reply_message.data, reply_message.len);
+}
+
+/*
+ * Send hot standby feedback message to primary, plus the current time,
+ * in case they don't have a watch.
+ *
+ * If the user disables feedback, send one final message to tell sender
+ * to forget about the xmin on this standby. We also send this message
+ * on first connect because a previous connection might have set xmin
+ * on a replication slot. (If we're not using a slot it's harmless to
+ * send a feedback message explicitly setting InvalidTransactionId).
+ */
+static void
+XLogWalRcvSendHSFeedback(bool immed)
+{
+	TimestampTz now;
+	FullTransactionId nextFullXid;
+	TransactionId nextXid;
+	uint32		xmin_epoch,
+				catalog_xmin_epoch;
+	TransactionId xmin,
+				catalog_xmin;
+	static TimestampTz sendTime = 0;
+
+	/* initially true so we always send at least one feedback message */
+	static bool primary_has_standby_xmin = true;
+
+	/*
+	 * If the user doesn't want status to be reported to the primary, be sure
+	 * to exit before doing anything at all.
+	 */
+	if ((wal_receiver_status_interval <= 0 || !hot_standby_feedback) &&
+		!primary_has_standby_xmin)
+		return;
+
+	/* Get current timestamp. */
+	now = GetCurrentTimestamp();
+
+	if (!immed)
+	{
+		/*
+		 * Send feedback at most once per wal_receiver_status_interval.
+		 */
+		if (!TimestampDifferenceExceeds(sendTime, now,
+										wal_receiver_status_interval * 1000))
+			return;
+		sendTime = now;
+	}
+
+	/*
+	 * If Hot Standby is not yet accepting connections there is nothing to
+	 * send. Check this after the interval has expired to reduce number of
+	 * calls.
+	 *
+	 * Bailing out here also ensures that we don't send feedback until we've
+	 * read our own replication slot state, so we don't tell the primary to
+	 * discard needed xmin or catalog_xmin from any slots that may exist on
+	 * this replica.
+	 */
+	if (!HotStandbyActive())
+		return;
+
+	/*
+	 * Make the expensive call to get the oldest xmin once we are certain
+	 * everything else has been checked.
+	 */
+	if (hot_standby_feedback)
+	{
+		GetReplicationHorizons(&xmin, &catalog_xmin);
+	}
+	else
+	{
+		xmin = InvalidTransactionId;
+		catalog_xmin = InvalidTransactionId;
+	}
+
+	/*
+	 * Get epoch and adjust if nextXid and oldestXmin are different sides of
+	 * the epoch boundary.
+	 */
+	nextFullXid = ReadNextFullTransactionId();
+	nextXid = XidFromFullTransactionId(nextFullXid);
+	xmin_epoch = EpochFromFullTransactionId(nextFullXid);
+	catalog_xmin_epoch = xmin_epoch;
+	if (nextXid < xmin)
+		xmin_epoch--;
+	if (nextXid < catalog_xmin)
+		catalog_xmin_epoch--;
+
+	elog(DEBUG2, "sending hot standby feedback xmin %u epoch %u catalog_xmin %u catalog_xmin_epoch %u",
+		 xmin, xmin_epoch, catalog_xmin, catalog_xmin_epoch);
+
+	/* Construct the message and send it. */
+	resetStringInfo(&reply_message);
+	pq_sendbyte(&reply_message, 'h');
+	pq_sendint64(&reply_message, GetCurrentTimestamp());
+	pq_sendint32(&reply_message, xmin);
+	pq_sendint32(&reply_message, xmin_epoch);
+	pq_sendint32(&reply_message, catalog_xmin);
+	pq_sendint32(&reply_message, catalog_xmin_epoch);
+	walrcv_send(wrconn, reply_message.data, reply_message.len);
+	if (TransactionIdIsValid(xmin) || TransactionIdIsValid(catalog_xmin))
+		primary_has_standby_xmin = true;
+	else
+		primary_has_standby_xmin = false;
+}
+
+/*
+ * Update shared memory status upon receiving a message from primary.
+ *
+ * 'walEnd' and 'sendTime' are the end-of-WAL and timestamp of the latest
+ * message, reported by primary.
+ */
+static void
+ProcessWalSndrMessage(XLogRecPtr walEnd, TimestampTz sendTime)
+{
+	WalRcvData *walrcv = WalRcv;
+
+	TimestampTz lastMsgReceiptTime = GetCurrentTimestamp();
+
+	/* Update shared-memory status */
+	SpinLockAcquire(&walrcv->mutex);
+	if (walrcv->latestWalEnd < walEnd)
+		walrcv->latestWalEndTime = sendTime;
+	walrcv->latestWalEnd = walEnd;
+	walrcv->lastMsgSendTime = sendTime;
+	walrcv->lastMsgReceiptTime = lastMsgReceiptTime;
+	SpinLockRelease(&walrcv->mutex);
+
+	if (message_level_is_interesting(DEBUG2))
+	{
+		char	   *sendtime;
+		char	   *receipttime;
+		int			applyDelay;
+
+		/* Copy because timestamptz_to_str returns a static buffer */
+		sendtime = pstrdup(timestamptz_to_str(sendTime));
+		receipttime = pstrdup(timestamptz_to_str(lastMsgReceiptTime));
+		applyDelay = GetReplicationApplyDelay();
+
+		/* apply delay is not available */
+		if (applyDelay == -1)
+			elog(DEBUG2, "sendtime %s receipttime %s replication apply delay (N/A) transfer latency %d ms",
+				 sendtime,
+				 receipttime,
+				 GetReplicationTransferLatency());
+		else
+			elog(DEBUG2, "sendtime %s receipttime %s replication apply delay %d ms transfer latency %d ms",
+				 sendtime,
+				 receipttime,
+				 applyDelay,
+				 GetReplicationTransferLatency());
+
+		pfree(sendtime);
+		pfree(receipttime);
+	}
+}
+
+/*
+ * Wake up the walreceiver main loop.
+ *
+ * This is called by the startup process whenever interesting xlog records
+ * are applied, so that walreceiver can check if it needs to send an apply
+ * notification back to the primary which may be waiting in a COMMIT with
+ * synchronous_commit = remote_apply.
+ */
+void
+WalRcvForceReply(void)
+{
+	Latch	   *latch;
+
+	WalRcv->force_reply = true;
+	/* fetching the latch pointer might not be atomic, so use spinlock */
+	SpinLockAcquire(&WalRcv->mutex);
+	latch = WalRcv->latch;
+	SpinLockRelease(&WalRcv->mutex);
+	if (latch)
+		SetLatch(latch);
+}
+
+/*
+ * Return a string constant representing the state. This is used
+ * in system functions and views, and should *not* be translated.
+ */
+static const char *
+WalRcvGetStateString(WalRcvState state)
+{
+	switch (state)
+	{
+		case WALRCV_STOPPED:
+			return "stopped";
+		case WALRCV_STARTING:
+			return "starting";
+		case WALRCV_STREAMING:
+			return "streaming";
+		case WALRCV_WAITING:
+			return "waiting";
+		case WALRCV_RESTARTING:
+			return "restarting";
+		case WALRCV_STOPPING:
+			return "stopping";
+	}
+	return "UNKNOWN";
+}
+
+/*
+ * Returns activity of WAL receiver, including pid, state and xlog locations
+ * received from the WAL sender of another server.
+ */
+Datum
+pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
+{
+	TupleDesc	tupdesc;
+	Datum	   *values;
+	bool	   *nulls;
+	int			pid;
+	bool		ready_to_display;
+	WalRcvState state;
+	XLogRecPtr	receive_start_lsn;
+	TimeLineID	receive_start_tli;
+	XLogRecPtr	written_lsn;
+	XLogRecPtr	flushed_lsn;
+	TimeLineID	received_tli;
+	TimestampTz last_send_time;
+	TimestampTz last_receipt_time;
+	XLogRecPtr	latest_end_lsn;
+	TimestampTz latest_end_time;
+	char		sender_host[NI_MAXHOST];
+	int			sender_port = 0;
+	char		slotname[NAMEDATALEN];
+	char		conninfo[MAXCONNINFO];
+
+	/* Take a lock to ensure value consistency */
+	SpinLockAcquire(&WalRcv->mutex);
+	pid = (int) WalRcv->pid;
+	ready_to_display = WalRcv->ready_to_display;
+	state = WalRcv->walRcvState;
+	receive_start_lsn = WalRcv->receiveStart;
+	receive_start_tli = WalRcv->receiveStartTLI;
+	flushed_lsn = WalRcv->flushedUpto;
+	received_tli = WalRcv->receivedTLI;
+	last_send_time = WalRcv->lastMsgSendTime;
+	last_receipt_time = WalRcv->lastMsgReceiptTime;
+	latest_end_lsn = WalRcv->latestWalEnd;
+	latest_end_time = WalRcv->latestWalEndTime;
+	strlcpy(slotname, (char *) WalRcv->slotname, sizeof(slotname));
+	strlcpy(sender_host, (char *) WalRcv->sender_host, sizeof(sender_host));
+	sender_port = WalRcv->sender_port;
+	strlcpy(conninfo, (char *) WalRcv->conninfo, sizeof(conninfo));
+	SpinLockRelease(&WalRcv->mutex);
+
+	/*
+	 * No WAL receiver (or not ready yet), just return a tuple with NULL
+	 * values
+	 */
+	if (pid == 0 || !ready_to_display)
+		PG_RETURN_NULL();
+
+	/*
+	 * Read "writtenUpto" without holding a spinlock.  Note that it may not be
+	 * consistent with the other shared variables of the WAL receiver
+	 * protected by a spinlock, but this should not be used for data integrity
+	 * checks.
+	 */
+	written_lsn = pg_atomic_read_u64(&WalRcv->writtenUpto);
+
+	/* determine result type */
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+		elog(ERROR, "return type must be a row type");
+
+	values = palloc0(sizeof(Datum) * tupdesc->natts);
+	nulls = palloc0(sizeof(bool) * tupdesc->natts);
+
+	/* Fetch values */
+	values[0] = Int32GetDatum(pid);
+
+	if (!is_member_of_role(GetUserId(), ROLE_PG_READ_ALL_STATS))
+	{
+		/*
+		 * Only superusers and members of pg_read_all_stats can see details.
+		 * Other users only get the pid value to know whether it is a WAL
+		 * receiver, but no details.
+		 */
+		MemSet(&nulls[1], true, sizeof(bool) * (tupdesc->natts - 1));
+	}
+	else
+	{
+		values[1] = CStringGetTextDatum(WalRcvGetStateString(state));
+
+		if (XLogRecPtrIsInvalid(receive_start_lsn))
+			nulls[2] = true;
+		else
+			values[2] = LSNGetDatum(receive_start_lsn);
+		values[3] = Int32GetDatum(receive_start_tli);
+		if (XLogRecPtrIsInvalid(written_lsn))
+			nulls[4] = true;
+		else
+			values[4] = LSNGetDatum(written_lsn);
+		if (XLogRecPtrIsInvalid(flushed_lsn))
+			nulls[5] = true;
+		else
+			values[5] = LSNGetDatum(flushed_lsn);
+		values[6] = Int32GetDatum(received_tli);
+		if (last_send_time == 0)
+			nulls[7] = true;
+		else
+			values[7] = TimestampTzGetDatum(last_send_time);
+		if (last_receipt_time == 0)
+			nulls[8] = true;
+		else
+			values[8] = TimestampTzGetDatum(last_receipt_time);
+		if (XLogRecPtrIsInvalid(latest_end_lsn))
+			nulls[9] = true;
+		else
+			values[9] = LSNGetDatum(latest_end_lsn);
+		if (latest_end_time == 0)
+			nulls[10] = true;
+		else
+			values[10] = TimestampTzGetDatum(latest_end_time);
+		if (*slotname == '\0')
+			nulls[11] = true;
+		else
+			values[11] = CStringGetTextDatum(slotname);
+		if (*sender_host == '\0')
+			nulls[12] = true;
+		else
+			values[12] = CStringGetTextDatum(sender_host);
+		if (sender_port == 0)
+			nulls[13] = true;
+		else
+			values[13] = Int32GetDatum(sender_port);
+		if (*conninfo == '\0')
+			nulls[14] = true;
+		else
+			values[14] = CStringGetTextDatum(conninfo);
+	}
+
+	/* Returns the record as Datum */
+	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
diff --git a/src/backend/replication/walreceiverfuncs.c b/src/backend/replication/walreceiverfuncs.c
new file mode 100644
index 0000000..6f0acbf
--- /dev/null
+++ b/src/backend/replication/walreceiverfuncs.c
@@ -0,0 +1,407 @@
+/*-------------------------------------------------------------------------
+ *
+ * walreceiverfuncs.c
+ *
+ * This file contains functions used by the startup process to communicate
+ * with the walreceiver process. Functions implementing walreceiver itself
+ * are in walreceiver.c.
+ *
+ * Portions Copyright (c) 2010-2021, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/walreceiverfuncs.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <time.h>
+#include <unistd.h>
+#include <signal.h>
+
+#include "access/xlog_internal.h"
+#include "pgstat.h"
+#include "postmaster/startup.h"
+#include "replication/walreceiver.h"
+#include "storage/pmsignal.h"
+#include "storage/shmem.h"
+#include "utils/timestamp.h"
+
+WalRcvData *WalRcv = NULL;
+
+/*
+ * How long to wait for walreceiver to start up after requesting
+ * postmaster to launch it. In seconds.
+ */
+#define WALRCV_STARTUP_TIMEOUT 10
+
+/* Report shared memory space needed by WalRcvShmemInit */
+Size
+WalRcvShmemSize(void)
+{
+	Size		size = 0;
+
+	size = add_size(size, sizeof(WalRcvData));
+
+	return size;
+}
+
+/* Allocate and initialize walreceiver-related shared memory */
+void
+WalRcvShmemInit(void)
+{
+	bool		found;
+
+	WalRcv = (WalRcvData *)
+		ShmemInitStruct("Wal Receiver Ctl", WalRcvShmemSize(), &found);
+
+	if (!found)
+	{
+		/* First time through, so initialize */
+		MemSet(WalRcv, 0, WalRcvShmemSize());
+		WalRcv->walRcvState = WALRCV_STOPPED;
+		ConditionVariableInit(&WalRcv->walRcvStoppedCV);
+		SpinLockInit(&WalRcv->mutex);
+		pg_atomic_init_u64(&WalRcv->writtenUpto, 0);
+		WalRcv->latch = NULL;
+	}
+}
+
+/* Is walreceiver running (or starting up)? */
+bool
+WalRcvRunning(void)
+{
+	WalRcvData *walrcv = WalRcv;
+	WalRcvState state;
+	pg_time_t	startTime;
+
+	SpinLockAcquire(&walrcv->mutex);
+
+	state = walrcv->walRcvState;
+	startTime = walrcv->startTime;
+
+	SpinLockRelease(&walrcv->mutex);
+
+	/*
+	 * If it has taken too long for walreceiver to start up, give up. Setting
+	 * the state to STOPPED ensures that if walreceiver later does start up
+	 * after all, it will see that it's not supposed to be running and die
+	 * without doing anything.
+	 */
+	if (state == WALRCV_STARTING)
+	{
+		pg_time_t	now = (pg_time_t) time(NULL);
+
+		if ((now - startTime) > WALRCV_STARTUP_TIMEOUT)
+		{
+			bool		stopped = false;
+
+			SpinLockAcquire(&walrcv->mutex);
+			if (walrcv->walRcvState == WALRCV_STARTING)
+			{
+				state = walrcv->walRcvState = WALRCV_STOPPED;
+				stopped = true;
+			}
+			SpinLockRelease(&walrcv->mutex);
+
+			if (stopped)
+				ConditionVariableBroadcast(&walrcv->walRcvStoppedCV);
+		}
+	}
+
+	if (state != WALRCV_STOPPED)
+		return true;
+	else
+		return false;
+}
+
+/*
+ * Is walreceiver running and streaming (or at least attempting to connect,
+ * or starting up)?
+ */
+bool
+WalRcvStreaming(void)
+{
+	WalRcvData *walrcv = WalRcv;
+	WalRcvState state;
+	pg_time_t	startTime;
+
+	SpinLockAcquire(&walrcv->mutex);
+
+	state = walrcv->walRcvState;
+	startTime = walrcv->startTime;
+
+	SpinLockRelease(&walrcv->mutex);
+
+	/*
+	 * If it has taken too long for walreceiver to start up, give up. Setting
+	 * the state to STOPPED ensures that if walreceiver later does start up
+	 * after all, it will see that it's not supposed to be running and die
+	 * without doing anything.
+	 */
+	if (state == WALRCV_STARTING)
+	{
+		pg_time_t	now = (pg_time_t) time(NULL);
+
+		if ((now - startTime) > WALRCV_STARTUP_TIMEOUT)
+		{
+			bool		stopped = false;
+
+			SpinLockAcquire(&walrcv->mutex);
+			if (walrcv->walRcvState == WALRCV_STARTING)
+			{
+				state = walrcv->walRcvState = WALRCV_STOPPED;
+				stopped = true;
+			}
+			SpinLockRelease(&walrcv->mutex);
+
+			if (stopped)
+				ConditionVariableBroadcast(&walrcv->walRcvStoppedCV);
+		}
+	}
+
+	if (state == WALRCV_STREAMING || state == WALRCV_STARTING ||
+		state == WALRCV_RESTARTING)
+		return true;
+	else
+		return false;
+}
+
+/*
+ * Stop walreceiver (if running) and wait for it to die.
+ * Executed by the Startup process.
+ */
+void
+ShutdownWalRcv(void)
+{
+	WalRcvData *walrcv = WalRcv;
+	pid_t		walrcvpid = 0;
+	bool		stopped = false;
+
+	/*
+	 * Request walreceiver to stop. Walreceiver will switch to WALRCV_STOPPED
+	 * mode once it's finished, and will also request postmaster to not
+	 * restart itself.
+	 */
+	SpinLockAcquire(&walrcv->mutex);
+	switch (walrcv->walRcvState)
+	{
+		case WALRCV_STOPPED:
+			break;
+		case WALRCV_STARTING:
+			walrcv->walRcvState = WALRCV_STOPPED;
+			stopped = true;
+			break;
+
+		case WALRCV_STREAMING:
+		case WALRCV_WAITING:
+		case WALRCV_RESTARTING:
+			walrcv->walRcvState = WALRCV_STOPPING;
+			/* fall through */
+		case WALRCV_STOPPING:
+			walrcvpid = walrcv->pid;
+			break;
+	}
+	SpinLockRelease(&walrcv->mutex);
+
+	/* Unnecessary but consistent. */
+	if (stopped)
+		ConditionVariableBroadcast(&walrcv->walRcvStoppedCV);
+
+	/*
+	 * Signal walreceiver process if it was still running.
+	 */
+	if (walrcvpid != 0)
+		kill(walrcvpid, SIGTERM);
+
+	/*
+	 * Wait for walreceiver to acknowledge its death by setting state to
+	 * WALRCV_STOPPED.
+	 */
+	ConditionVariablePrepareToSleep(&walrcv->walRcvStoppedCV);
+	while (WalRcvRunning())
+		ConditionVariableSleep(&walrcv->walRcvStoppedCV,
+							   WAIT_EVENT_WAL_RECEIVER_EXIT);
+	ConditionVariableCancelSleep();
+}
+
+/*
+ * Request postmaster to start walreceiver.
+ *
+ * "recptr" indicates the position where streaming should begin.  "conninfo"
+ * is a libpq connection string to use.  "slotname" is, optionally, the name
+ * of a replication slot to acquire.  "create_temp_slot" indicates to create
+ * a temporary slot when no "slotname" is given.
+ *
+ * WAL receivers do not directly load GUC parameters used for the connection
+ * to the primary, and rely on the values passed down by the caller of this
+ * routine instead.  Hence, the addition of any new parameters should happen
+ * through this code path.
+ */
+void
+RequestXLogStreaming(TimeLineID tli, XLogRecPtr recptr, const char *conninfo,
+					 const char *slotname, bool create_temp_slot)
+{
+	WalRcvData *walrcv = WalRcv;
+	bool		launch = false;
+	pg_time_t	now = (pg_time_t) time(NULL);
+	Latch	   *latch;
+
+	/*
+	 * We always start at the beginning of the segment. That prevents a broken
+	 * segment (i.e., with no records in the first half of a segment) from
+	 * being created by XLOG streaming, which might cause trouble later on if
+	 * the segment is e.g archived.
+	 */
+	if (XLogSegmentOffset(recptr, wal_segment_size) != 0)
+		recptr -= XLogSegmentOffset(recptr, wal_segment_size);
+
+	SpinLockAcquire(&walrcv->mutex);
+
+	/* It better be stopped if we try to restart it */
+	Assert(walrcv->walRcvState == WALRCV_STOPPED ||
+		   walrcv->walRcvState == WALRCV_WAITING);
+
+	if (conninfo != NULL)
+		strlcpy((char *) walrcv->conninfo, conninfo, MAXCONNINFO);
+	else
+		walrcv->conninfo[0] = '\0';
+
+	/*
+	 * Use configured replication slot if present, and ignore the value of
+	 * create_temp_slot as the slot name should be persistent.  Otherwise, use
+	 * create_temp_slot to determine whether this WAL receiver should create a
+	 * temporary slot by itself and use it, or not.
+	 */
+	if (slotname != NULL && slotname[0] != '\0')
+	{
+		strlcpy((char *) walrcv->slotname, slotname, NAMEDATALEN);
+		walrcv->is_temp_slot = false;
+	}
+	else
+	{
+		walrcv->slotname[0] = '\0';
+		walrcv->is_temp_slot = create_temp_slot;
+	}
+
+	if (walrcv->walRcvState == WALRCV_STOPPED)
+	{
+		launch = true;
+		walrcv->walRcvState = WALRCV_STARTING;
+	}
+	else
+		walrcv->walRcvState = WALRCV_RESTARTING;
+	walrcv->startTime = now;
+
+	/*
+	 * If this is the first startup of walreceiver (on this timeline),
+	 * initialize flushedUpto and latestChunkStart to the starting point.
+	 */
+	if (walrcv->receiveStart == 0 || walrcv->receivedTLI != tli)
+	{
+		walrcv->flushedUpto = recptr;
+		walrcv->receivedTLI = tli;
+		walrcv->latestChunkStart = recptr;
+	}
+	walrcv->receiveStart = recptr;
+	walrcv->receiveStartTLI = tli;
+
+	latch = walrcv->latch;
+
+	SpinLockRelease(&walrcv->mutex);
+
+	if (launch)
+		SendPostmasterSignal(PMSIGNAL_START_WALRECEIVER);
+	else if (latch)
+		SetLatch(latch);
+}
+
+/*
+ * Returns the last+1 byte position that walreceiver has flushed.
+ *
+ * Optionally, returns the previous chunk start, that is the first byte
+ * written in the most recent walreceiver flush cycle.  Callers not
+ * interested in that value may pass NULL for latestChunkStart. Same for
+ * receiveTLI.
+ */
+XLogRecPtr
+GetWalRcvFlushRecPtr(XLogRecPtr *latestChunkStart, TimeLineID *receiveTLI)
+{
+	WalRcvData *walrcv = WalRcv;
+	XLogRecPtr	recptr;
+
+	SpinLockAcquire(&walrcv->mutex);
+	recptr = walrcv->flushedUpto;
+	if (latestChunkStart)
+		*latestChunkStart = walrcv->latestChunkStart;
+	if (receiveTLI)
+		*receiveTLI = walrcv->receivedTLI;
+	SpinLockRelease(&walrcv->mutex);
+
+	return recptr;
+}
+
+/*
+ * Returns the last+1 byte position that walreceiver has written.
+ * This returns a recently written value without taking a lock.
+ */
+XLogRecPtr
+GetWalRcvWriteRecPtr(void)
+{
+	WalRcvData *walrcv = WalRcv;
+
+	return pg_atomic_read_u64(&walrcv->writtenUpto);
+}
+
+/*
+ * Returns the replication apply delay in ms or -1
+ * if the apply delay info is not available
+ */
+int
+GetReplicationApplyDelay(void)
+{
+	WalRcvData *walrcv = WalRcv;
+	XLogRecPtr	receivePtr;
+	XLogRecPtr	replayPtr;
+	TimestampTz chunkReplayStartTime;
+
+	SpinLockAcquire(&walrcv->mutex);
+	receivePtr = walrcv->flushedUpto;
+	SpinLockRelease(&walrcv->mutex);
+
+	replayPtr = GetXLogReplayRecPtr(NULL);
+
+	if (receivePtr == replayPtr)
+		return 0;
+
+	chunkReplayStartTime = GetCurrentChunkReplayStartTime();
+
+	if (chunkReplayStartTime == 0)
+		return -1;
+
+	return TimestampDifferenceMilliseconds(chunkReplayStartTime,
+										   GetCurrentTimestamp());
+}
+
+/*
+ * Returns the network latency in ms, note that this includes any
+ * difference in clock settings between the servers, as well as timezone.
+ */
+int
+GetReplicationTransferLatency(void)
+{
+	WalRcvData *walrcv = WalRcv;
+	TimestampTz lastMsgSendTime;
+	TimestampTz lastMsgReceiptTime;
+
+	SpinLockAcquire(&walrcv->mutex);
+	lastMsgSendTime = walrcv->lastMsgSendTime;
+	lastMsgReceiptTime = walrcv->lastMsgReceiptTime;
+	SpinLockRelease(&walrcv->mutex);
+
+	return TimestampDifferenceMilliseconds(lastMsgSendTime,
+										   lastMsgReceiptTime);
+}
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
new file mode 100644
index 0000000..28f0a29
--- /dev/null
+++ b/src/backend/replication/walsender.c
@@ -0,0 +1,3729 @@
+/*-------------------------------------------------------------------------
+ *
+ * walsender.c
+ *
+ * The WAL sender process (walsender) is new as of Postgres 9.0. It takes
+ * care of sending XLOG from the primary server to a single recipient.
+ * (Note that there can be more than one walsender process concurrently.)
+ * It is started by the postmaster when the walreceiver of a standby server
+ * connects to the primary server and requests XLOG streaming replication.
+ *
+ * A walsender is similar to a regular backend, ie. there is a one-to-one
+ * relationship between a connection and a walsender process, but instead
+ * of processing SQL queries, it understands a small set of special
+ * replication-mode commands. The START_REPLICATION command begins streaming
+ * WAL to the client. While streaming, the walsender keeps reading XLOG
+ * records from the disk and sends them to the standby server over the
+ * COPY protocol, until either side ends the replication by exiting COPY
+ * mode (or until the connection is closed).
+ *
+ * Normal termination is by SIGTERM, which instructs the walsender to
+ * close the connection and exit(0) at the next convenient moment. Emergency
+ * termination is by SIGQUIT; like any backend, the walsender will simply
+ * abort and exit on SIGQUIT. A close of the connection and a FATAL error
+ * are treated as not a crash but approximately normal termination;
+ * the walsender will exit quickly without sending any more XLOG records.
+ *
+ * If the server is shut down, checkpointer sends us
+ * PROCSIG_WALSND_INIT_STOPPING after all regular backends have exited.  If
+ * the backend is idle or runs an SQL query this causes the backend to
+ * shutdown, if logical replication is in progress all existing WAL records
+ * are processed followed by a shutdown.  Otherwise this causes the walsender
+ * to switch to the "stopping" state. In this state, the walsender will reject
+ * any further replication commands. The checkpointer begins the shutdown
+ * checkpoint once all walsenders are confirmed as stopping. When the shutdown
+ * checkpoint finishes, the postmaster sends us SIGUSR2. This instructs
+ * walsender to send any outstanding WAL, including the shutdown checkpoint
+ * record, wait for it to be replicated to the standby, and then exit.
+ *
+ *
+ * Portions Copyright (c) 2010-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/walsender.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <signal.h>
+#include <unistd.h>
+
+#include "access/printtup.h"
+#include "access/timeline.h"
+#include "access/transam.h"
+#include "access/xact.h"
+#include "access/xlog_internal.h"
+#include "access/xlogreader.h"
+#include "access/xlogutils.h"
+#include "catalog/pg_authid.h"
+#include "catalog/pg_type.h"
+#include "commands/dbcommands.h"
+#include "commands/defrem.h"
+#include "funcapi.h"
+#include "libpq/libpq.h"
+#include "libpq/pqformat.h"
+#include "miscadmin.h"
+#include "nodes/replnodes.h"
+#include "pgstat.h"
+#include "postmaster/interrupt.h"
+#include "replication/basebackup.h"
+#include "replication/decode.h"
+#include "replication/logical.h"
+#include "replication/slot.h"
+#include "replication/snapbuild.h"
+#include "replication/syncrep.h"
+#include "replication/walreceiver.h"
+#include "replication/walsender.h"
+#include "replication/walsender_private.h"
+#include "storage/condition_variable.h"
+#include "storage/fd.h"
+#include "storage/ipc.h"
+#include "storage/pmsignal.h"
+#include "storage/proc.h"
+#include "storage/procarray.h"
+#include "tcop/dest.h"
+#include "tcop/tcopprot.h"
+#include "utils/acl.h"
+#include "utils/builtins.h"
+#include "utils/guc.h"
+#include "utils/memutils.h"
+#include "utils/pg_lsn.h"
+#include "utils/portal.h"
+#include "utils/ps_status.h"
+#include "utils/timeout.h"
+#include "utils/timestamp.h"
+
+/*
+ * Maximum data payload in a WAL data message.  Must be >= XLOG_BLCKSZ.
+ *
+ * We don't have a good idea of what a good value would be; there's some
+ * overhead per message in both walsender and walreceiver, but on the other
+ * hand sending large batches makes walsender less responsive to signals
+ * because signals are checked only between messages.  128kB (with
+ * default 8k blocks) seems like a reasonable guess for now.
+ */
+#define MAX_SEND_SIZE (XLOG_BLCKSZ * 16)
+
+/* Array of WalSnds in shared memory */
+WalSndCtlData *WalSndCtl = NULL;
+
+/* My slot in the shared memory array */
+WalSnd	   *MyWalSnd = NULL;
+
+/* Global state */
+bool		am_walsender = false;	/* Am I a walsender process? */
+bool		am_cascading_walsender = false; /* Am I cascading WAL to another
+											 * standby? */
+bool		am_db_walsender = false;	/* Connected to a database? */
+
+/* User-settable parameters for walsender */
+int			max_wal_senders = 0;	/* the maximum number of concurrent
+									 * walsenders */
+int			wal_sender_timeout = 60 * 1000; /* maximum time to send one WAL
+											 * data message */
+bool		log_replication_commands = false;
+
+/*
+ * State for WalSndWakeupRequest
+ */
+bool		wake_wal_senders = false;
+
+/*
+ * xlogreader used for replication.  Note that a WAL sender doing physical
+ * replication does not need xlogreader to read WAL, but it needs one to
+ * keep a state of its work.
+ */
+static XLogReaderState *xlogreader = NULL;
+
+/*
+ * These variables keep track of the state of the timeline we're currently
+ * sending. sendTimeLine identifies the timeline. If sendTimeLineIsHistoric,
+ * the timeline is not the latest timeline on this server, and the server's
+ * history forked off from that timeline at sendTimeLineValidUpto.
+ */
+static TimeLineID sendTimeLine = 0;
+static TimeLineID sendTimeLineNextTLI = 0;
+static bool sendTimeLineIsHistoric = false;
+static XLogRecPtr sendTimeLineValidUpto = InvalidXLogRecPtr;
+
+/*
+ * How far have we sent WAL already? This is also advertised in
+ * MyWalSnd->sentPtr.  (Actually, this is the next WAL location to send.)
+ */
+static XLogRecPtr sentPtr = InvalidXLogRecPtr;
+
+/* Buffers for constructing outgoing messages and processing reply messages. */
+static StringInfoData output_message;
+static StringInfoData reply_message;
+static StringInfoData tmpbuf;
+
+/* Timestamp of last ProcessRepliesIfAny(). */
+static TimestampTz last_processing = 0;
+
+/*
+ * Timestamp of last ProcessRepliesIfAny() that saw a reply from the
+ * standby. Set to 0 if wal_sender_timeout doesn't need to be active.
+ */
+static TimestampTz last_reply_timestamp = 0;
+
+/* Have we sent a heartbeat message asking for reply, since last reply? */
+static bool waiting_for_ping_response = false;
+
+/*
+ * While streaming WAL in Copy mode, streamingDoneSending is set to true
+ * after we have sent CopyDone. We should not send any more CopyData messages
+ * after that. streamingDoneReceiving is set to true when we receive CopyDone
+ * from the other end. When both become true, it's time to exit Copy mode.
+ */
+static bool streamingDoneSending;
+static bool streamingDoneReceiving;
+
+/* Are we there yet? */
+static bool WalSndCaughtUp = false;
+
+/* Flags set by signal handlers for later service in main loop */
+static volatile sig_atomic_t got_SIGUSR2 = false;
+static volatile sig_atomic_t got_STOPPING = false;
+
+/*
+ * This is set while we are streaming. When not set
+ * PROCSIG_WALSND_INIT_STOPPING signal will be handled like SIGTERM. When set,
+ * the main loop is responsible for checking got_STOPPING and terminating when
+ * it's set (after streaming any remaining WAL).
+ */
+static volatile sig_atomic_t replication_active = false;
+
+static LogicalDecodingContext *logical_decoding_ctx = NULL;
+
+/* A sample associating a WAL location with the time it was written. */
+typedef struct
+{
+	XLogRecPtr	lsn;
+	TimestampTz time;
+} WalTimeSample;
+
+/* The size of our buffer of time samples. */
+#define LAG_TRACKER_BUFFER_SIZE 8192
+
+/* A mechanism for tracking replication lag. */
+typedef struct
+{
+	XLogRecPtr	last_lsn;
+	WalTimeSample buffer[LAG_TRACKER_BUFFER_SIZE];
+	int			write_head;
+	int			read_heads[NUM_SYNC_REP_WAIT_MODE];
+	WalTimeSample last_read[NUM_SYNC_REP_WAIT_MODE];
+} LagTracker;
+
+static LagTracker *lag_tracker;
+
+/* Signal handlers */
+static void WalSndLastCycleHandler(SIGNAL_ARGS);
+
+/* Prototypes for private functions */
+typedef void (*WalSndSendDataCallback) (void);
+static void WalSndLoop(WalSndSendDataCallback send_data);
+static void InitWalSenderSlot(void);
+static void WalSndKill(int code, Datum arg);
+static void WalSndShutdown(void) pg_attribute_noreturn();
+static void XLogSendPhysical(void);
+static void XLogSendLogical(void);
+static void WalSndDone(WalSndSendDataCallback send_data);
+static XLogRecPtr GetStandbyFlushRecPtr(void);
+static void IdentifySystem(void);
+static void CreateReplicationSlot(CreateReplicationSlotCmd *cmd);
+static void DropReplicationSlot(DropReplicationSlotCmd *cmd);
+static void StartReplication(StartReplicationCmd *cmd);
+static void StartLogicalReplication(StartReplicationCmd *cmd);
+static void ProcessStandbyMessage(void);
+static void ProcessStandbyReplyMessage(void);
+static void ProcessStandbyHSFeedbackMessage(void);
+static void ProcessRepliesIfAny(void);
+static void ProcessPendingWrites(void);
+static void WalSndKeepalive(bool requestReply);
+static void WalSndKeepaliveIfNecessary(void);
+static void WalSndCheckTimeOut(void);
+static long WalSndComputeSleeptime(TimestampTz now);
+static void WalSndWait(uint32 socket_events, long timeout, uint32 wait_event);
+static void WalSndPrepareWrite(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid, bool last_write);
+static void WalSndWriteData(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid, bool last_write);
+static void WalSndUpdateProgress(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid);
+static XLogRecPtr WalSndWaitForWal(XLogRecPtr loc);
+static void LagTrackerWrite(XLogRecPtr lsn, TimestampTz local_flush_time);
+static TimeOffset LagTrackerRead(int head, XLogRecPtr lsn, TimestampTz now);
+static bool TransactionIdInRecentPast(TransactionId xid, uint32 epoch);
+
+static void WalSndSegmentOpen(XLogReaderState *state, XLogSegNo nextSegNo,
+							  TimeLineID *tli_p);
+
+
+/* Initialize walsender process before entering the main command loop */
+void
+InitWalSender(void)
+{
+	am_cascading_walsender = RecoveryInProgress();
+
+	/* Create a per-walsender data structure in shared memory */
+	InitWalSenderSlot();
+
+	/*
+	 * We don't currently need any ResourceOwner in a walsender process, but
+	 * if we did, we could call CreateAuxProcessResourceOwner here.
+	 */
+
+	/*
+	 * Let postmaster know that we're a WAL sender. Once we've declared us as
+	 * a WAL sender process, postmaster will let us outlive the bgwriter and
+	 * kill us last in the shutdown sequence, so we get a chance to stream all
+	 * remaining WAL at shutdown, including the shutdown checkpoint. Note that
+	 * there's no going back, and we mustn't write any WAL records after this.
+	 */
+	MarkPostmasterChildWalSender();
+	SendPostmasterSignal(PMSIGNAL_ADVANCE_STATE_MACHINE);
+
+	/* Initialize empty timestamp buffer for lag tracking. */
+	lag_tracker = MemoryContextAllocZero(TopMemoryContext, sizeof(LagTracker));
+}
+
+/*
+ * Clean up after an error.
+ *
+ * WAL sender processes don't use transactions like regular backends do.
+ * This function does any cleanup required after an error in a WAL sender
+ * process, similar to what transaction abort does in a regular backend.
+ */
+void
+WalSndErrorCleanup(void)
+{
+	LWLockReleaseAll();
+	ConditionVariableCancelSleep();
+	pgstat_report_wait_end();
+
+	if (xlogreader != NULL && xlogreader->seg.ws_file >= 0)
+		wal_segment_close(xlogreader);
+
+	if (MyReplicationSlot != NULL)
+		ReplicationSlotRelease();
+
+	ReplicationSlotCleanup();
+
+	replication_active = false;
+
+	/*
+	 * If there is a transaction in progress, it will clean up our
+	 * ResourceOwner, but if a replication command set up a resource owner
+	 * without a transaction, we've got to clean that up now.
+	 */
+	if (!IsTransactionOrTransactionBlock())
+		WalSndResourceCleanup(false);
+
+	if (got_STOPPING || got_SIGUSR2)
+		proc_exit(0);
+
+	/* Revert back to startup state */
+	WalSndSetState(WALSNDSTATE_STARTUP);
+}
+
+/*
+ * Clean up any ResourceOwner we created.
+ */
+void
+WalSndResourceCleanup(bool isCommit)
+{
+	ResourceOwner resowner;
+
+	if (CurrentResourceOwner == NULL)
+		return;
+
+	/*
+	 * Deleting CurrentResourceOwner is not allowed, so we must save a pointer
+	 * in a local variable and clear it first.
+	 */
+	resowner = CurrentResourceOwner;
+	CurrentResourceOwner = NULL;
+
+	/* Now we can release resources and delete it. */
+	ResourceOwnerRelease(resowner,
+						 RESOURCE_RELEASE_BEFORE_LOCKS, isCommit, true);
+	ResourceOwnerRelease(resowner,
+						 RESOURCE_RELEASE_LOCKS, isCommit, true);
+	ResourceOwnerRelease(resowner,
+						 RESOURCE_RELEASE_AFTER_LOCKS, isCommit, true);
+	ResourceOwnerDelete(resowner);
+}
+
+/*
+ * Handle a client's connection abort in an orderly manner.
+ */
+static void
+WalSndShutdown(void)
+{
+	/*
+	 * Reset whereToSendOutput to prevent ereport from attempting to send any
+	 * more messages to the standby.
+	 */
+	if (whereToSendOutput == DestRemote)
+		whereToSendOutput = DestNone;
+
+	proc_exit(0);
+	abort();					/* keep the compiler quiet */
+}
+
+/*
+ * Handle the IDENTIFY_SYSTEM command.
+ */
+static void
+IdentifySystem(void)
+{
+	char		sysid[32];
+	char		xloc[MAXFNAMELEN];
+	XLogRecPtr	logptr;
+	char	   *dbname = NULL;
+	DestReceiver *dest;
+	TupOutputState *tstate;
+	TupleDesc	tupdesc;
+	Datum		values[4];
+	bool		nulls[4];
+
+	/*
+	 * Reply with a result set with one row, four columns. First col is system
+	 * ID, second is timeline ID, third is current xlog location and the
+	 * fourth contains the database name if we are connected to one.
+	 */
+
+	snprintf(sysid, sizeof(sysid), UINT64_FORMAT,
+			 GetSystemIdentifier());
+
+	am_cascading_walsender = RecoveryInProgress();
+	if (am_cascading_walsender)
+	{
+		/* this also updates ThisTimeLineID */
+		logptr = GetStandbyFlushRecPtr();
+	}
+	else
+		logptr = GetFlushRecPtr();
+
+	snprintf(xloc, sizeof(xloc), "%X/%X", LSN_FORMAT_ARGS(logptr));
+
+	if (MyDatabaseId != InvalidOid)
+	{
+		MemoryContext cur = CurrentMemoryContext;
+
+		/* syscache access needs a transaction env. */
+		StartTransactionCommand();
+		/* make dbname live outside TX context */
+		MemoryContextSwitchTo(cur);
+		dbname = get_database_name(MyDatabaseId);
+		CommitTransactionCommand();
+		/* CommitTransactionCommand switches to TopMemoryContext */
+		MemoryContextSwitchTo(cur);
+	}
+
+	dest = CreateDestReceiver(DestRemoteSimple);
+	MemSet(nulls, false, sizeof(nulls));
+
+	/* need a tuple descriptor representing four columns */
+	tupdesc = CreateTemplateTupleDesc(4);
+	TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 1, "systemid",
+							  TEXTOID, -1, 0);
+	TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 2, "timeline",
+							  INT4OID, -1, 0);
+	TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 3, "xlogpos",
+							  TEXTOID, -1, 0);
+	TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 4, "dbname",
+							  TEXTOID, -1, 0);
+
+	/* prepare for projection of tuples */
+	tstate = begin_tup_output_tupdesc(dest, tupdesc, &TTSOpsVirtual);
+
+	/* column 1: system identifier */
+	values[0] = CStringGetTextDatum(sysid);
+
+	/* column 2: timeline */
+	values[1] = Int32GetDatum(ThisTimeLineID);
+
+	/* column 3: wal location */
+	values[2] = CStringGetTextDatum(xloc);
+
+	/* column 4: database name, or NULL if none */
+	if (dbname)
+		values[3] = CStringGetTextDatum(dbname);
+	else
+		nulls[3] = true;
+
+	/* send it to dest */
+	do_tup_output(tstate, values, nulls);
+
+	end_tup_output(tstate);
+}
+
+
+/*
+ * Handle TIMELINE_HISTORY command.
+ */
+static void
+SendTimeLineHistory(TimeLineHistoryCmd *cmd)
+{
+	StringInfoData buf;
+	char		histfname[MAXFNAMELEN];
+	char		path[MAXPGPATH];
+	int			fd;
+	off_t		histfilelen;
+	off_t		bytesleft;
+	Size		len;
+
+	/*
+	 * Reply with a result set with one row, and two columns. The first col is
+	 * the name of the history file, 2nd is the contents.
+	 */
+
+	TLHistoryFileName(histfname, cmd->timeline);
+	TLHistoryFilePath(path, cmd->timeline);
+
+	/* Send a RowDescription message */
+	pq_beginmessage(&buf, 'T');
+	pq_sendint16(&buf, 2);		/* 2 fields */
+
+	/* first field */
+	pq_sendstring(&buf, "filename");	/* col name */
+	pq_sendint32(&buf, 0);		/* table oid */
+	pq_sendint16(&buf, 0);		/* attnum */
+	pq_sendint32(&buf, TEXTOID);	/* type oid */
+	pq_sendint16(&buf, -1);		/* typlen */
+	pq_sendint32(&buf, 0);		/* typmod */
+	pq_sendint16(&buf, 0);		/* format code */
+
+	/* second field */
+	pq_sendstring(&buf, "content"); /* col name */
+	pq_sendint32(&buf, 0);		/* table oid */
+	pq_sendint16(&buf, 0);		/* attnum */
+	pq_sendint32(&buf, TEXTOID);	/* type oid */
+	pq_sendint16(&buf, -1);		/* typlen */
+	pq_sendint32(&buf, 0);		/* typmod */
+	pq_sendint16(&buf, 0);		/* format code */
+	pq_endmessage(&buf);
+
+	/* Send a DataRow message */
+	pq_beginmessage(&buf, 'D');
+	pq_sendint16(&buf, 2);		/* # of columns */
+	len = strlen(histfname);
+	pq_sendint32(&buf, len);	/* col1 len */
+	pq_sendbytes(&buf, histfname, len);
+
+	fd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
+	if (fd < 0)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not open file \"%s\": %m", path)));
+
+	/* Determine file length and send it to client */
+	histfilelen = lseek(fd, 0, SEEK_END);
+	if (histfilelen < 0)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not seek to end of file \"%s\": %m", path)));
+	if (lseek(fd, 0, SEEK_SET) != 0)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not seek to beginning of file \"%s\": %m", path)));
+
+	pq_sendint32(&buf, histfilelen);	/* col2 len */
+
+	bytesleft = histfilelen;
+	while (bytesleft > 0)
+	{
+		PGAlignedBlock rbuf;
+		int			nread;
+
+		pgstat_report_wait_start(WAIT_EVENT_WALSENDER_TIMELINE_HISTORY_READ);
+		nread = read(fd, rbuf.data, sizeof(rbuf));
+		pgstat_report_wait_end();
+		if (nread < 0)
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not read file \"%s\": %m",
+							path)));
+		else if (nread == 0)
+			ereport(ERROR,
+					(errcode(ERRCODE_DATA_CORRUPTED),
+					 errmsg("could not read file \"%s\": read %d of %zu",
+							path, nread, (Size) bytesleft)));
+
+		pq_sendbytes(&buf, rbuf.data, nread);
+		bytesleft -= nread;
+	}
+
+	if (CloseTransientFile(fd) != 0)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not close file \"%s\": %m", path)));
+
+	pq_endmessage(&buf);
+}
+
+/*
+ * Handle START_REPLICATION command.
+ *
+ * At the moment, this never returns, but an ereport(ERROR) will take us back
+ * to the main loop.
+ */
+static void
+StartReplication(StartReplicationCmd *cmd)
+{
+	StringInfoData buf;
+	XLogRecPtr	FlushPtr;
+
+	if (ThisTimeLineID == 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("IDENTIFY_SYSTEM has not been run before START_REPLICATION")));
+
+	/* create xlogreader for physical replication */
+	xlogreader =
+		XLogReaderAllocate(wal_segment_size, NULL,
+						   XL_ROUTINE(.segment_open = WalSndSegmentOpen,
+									  .segment_close = wal_segment_close),
+						   NULL);
+
+	if (!xlogreader)
+		ereport(ERROR,
+				(errcode(ERRCODE_OUT_OF_MEMORY),
+				 errmsg("out of memory")));
+
+	/*
+	 * We assume here that we're logging enough information in the WAL for
+	 * log-shipping, since this is checked in PostmasterMain().
+	 *
+	 * NOTE: wal_level can only change at shutdown, so in most cases it is
+	 * difficult for there to be WAL data that we can still see that was
+	 * written at wal_level='minimal'.
+	 */
+
+	if (cmd->slotname)
+	{
+		ReplicationSlotAcquire(cmd->slotname, true);
+		if (SlotIsLogical(MyReplicationSlot))
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					 errmsg("cannot use a logical replication slot for physical replication")));
+
+		/*
+		 * We don't need to verify the slot's restart_lsn here; instead we
+		 * rely on the caller requesting the starting point to use.  If the
+		 * WAL segment doesn't exist, we'll fail later.
+		 */
+	}
+
+	/*
+	 * Select the timeline. If it was given explicitly by the client, use
+	 * that. Otherwise use the timeline of the last replayed record, which is
+	 * kept in ThisTimeLineID.
+	 */
+	if (am_cascading_walsender)
+	{
+		/* this also updates ThisTimeLineID */
+		FlushPtr = GetStandbyFlushRecPtr();
+	}
+	else
+		FlushPtr = GetFlushRecPtr();
+
+	if (cmd->timeline != 0)
+	{
+		XLogRecPtr	switchpoint;
+
+		sendTimeLine = cmd->timeline;
+		if (sendTimeLine == ThisTimeLineID)
+		{
+			sendTimeLineIsHistoric = false;
+			sendTimeLineValidUpto = InvalidXLogRecPtr;
+		}
+		else
+		{
+			List	   *timeLineHistory;
+
+			sendTimeLineIsHistoric = true;
+
+			/*
+			 * Check that the timeline the client requested exists, and the
+			 * requested start location is on that timeline.
+			 */
+			timeLineHistory = readTimeLineHistory(ThisTimeLineID);
+			switchpoint = tliSwitchPoint(cmd->timeline, timeLineHistory,
+										 &sendTimeLineNextTLI);
+			list_free_deep(timeLineHistory);
+
+			/*
+			 * Found the requested timeline in the history. Check that
+			 * requested startpoint is on that timeline in our history.
+			 *
+			 * This is quite loose on purpose. We only check that we didn't
+			 * fork off the requested timeline before the switchpoint. We
+			 * don't check that we switched *to* it before the requested
+			 * starting point. This is because the client can legitimately
+			 * request to start replication from the beginning of the WAL
+			 * segment that contains switchpoint, but on the new timeline, so
+			 * that it doesn't end up with a partial segment. If you ask for
+			 * too old a starting point, you'll get an error later when we
+			 * fail to find the requested WAL segment in pg_wal.
+			 *
+			 * XXX: we could be more strict here and only allow a startpoint
+			 * that's older than the switchpoint, if it's still in the same
+			 * WAL segment.
+			 */
+			if (!XLogRecPtrIsInvalid(switchpoint) &&
+				switchpoint < cmd->startpoint)
+			{
+				ereport(ERROR,
+						(errmsg("requested starting point %X/%X on timeline %u is not in this server's history",
+								LSN_FORMAT_ARGS(cmd->startpoint),
+								cmd->timeline),
+						 errdetail("This server's history forked from timeline %u at %X/%X.",
+								   cmd->timeline,
+								   LSN_FORMAT_ARGS(switchpoint))));
+			}
+			sendTimeLineValidUpto = switchpoint;
+		}
+	}
+	else
+	{
+		sendTimeLine = ThisTimeLineID;
+		sendTimeLineValidUpto = InvalidXLogRecPtr;
+		sendTimeLineIsHistoric = false;
+	}
+
+	streamingDoneSending = streamingDoneReceiving = false;
+
+	/* If there is nothing to stream, don't even enter COPY mode */
+	if (!sendTimeLineIsHistoric || cmd->startpoint < sendTimeLineValidUpto)
+	{
+		/*
+		 * When we first start replication the standby will be behind the
+		 * primary. For some applications, for example synchronous
+		 * replication, it is important to have a clear state for this initial
+		 * catchup mode, so we can trigger actions when we change streaming
+		 * state later. We may stay in this state for a long time, which is
+		 * exactly why we want to be able to monitor whether or not we are
+		 * still here.
+		 */
+		WalSndSetState(WALSNDSTATE_CATCHUP);
+
+		/* Send a CopyBothResponse message, and start streaming */
+		pq_beginmessage(&buf, 'W');
+		pq_sendbyte(&buf, 0);
+		pq_sendint16(&buf, 0);
+		pq_endmessage(&buf);
+		pq_flush();
+
+		/*
+		 * Don't allow a request to stream from a future point in WAL that
+		 * hasn't been flushed to disk in this server yet.
+		 */
+		if (FlushPtr < cmd->startpoint)
+		{
+			ereport(ERROR,
+					(errmsg("requested starting point %X/%X is ahead of the WAL flush position of this server %X/%X",
+							LSN_FORMAT_ARGS(cmd->startpoint),
+							LSN_FORMAT_ARGS(FlushPtr))));
+		}
+
+		/* Start streaming from the requested point */
+		sentPtr = cmd->startpoint;
+
+		/* Initialize shared memory status, too */
+		SpinLockAcquire(&MyWalSnd->mutex);
+		MyWalSnd->sentPtr = sentPtr;
+		SpinLockRelease(&MyWalSnd->mutex);
+
+		SyncRepInitConfig();
+
+		/* Main loop of walsender */
+		replication_active = true;
+
+		WalSndLoop(XLogSendPhysical);
+
+		replication_active = false;
+		if (got_STOPPING)
+			proc_exit(0);
+		WalSndSetState(WALSNDSTATE_STARTUP);
+
+		Assert(streamingDoneSending && streamingDoneReceiving);
+	}
+
+	if (cmd->slotname)
+		ReplicationSlotRelease();
+
+	/*
+	 * Copy is finished now. Send a single-row result set indicating the next
+	 * timeline.
+	 */
+	if (sendTimeLineIsHistoric)
+	{
+		char		startpos_str[8 + 1 + 8 + 1];
+		DestReceiver *dest;
+		TupOutputState *tstate;
+		TupleDesc	tupdesc;
+		Datum		values[2];
+		bool		nulls[2];
+
+		snprintf(startpos_str, sizeof(startpos_str), "%X/%X",
+				 LSN_FORMAT_ARGS(sendTimeLineValidUpto));
+
+		dest = CreateDestReceiver(DestRemoteSimple);
+		MemSet(nulls, false, sizeof(nulls));
+
+		/*
+		 * Need a tuple descriptor representing two columns. int8 may seem
+		 * like a surprising data type for this, but in theory int4 would not
+		 * be wide enough for this, as TimeLineID is unsigned.
+		 */
+		tupdesc = CreateTemplateTupleDesc(2);
+		TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 1, "next_tli",
+								  INT8OID, -1, 0);
+		TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 2, "next_tli_startpos",
+								  TEXTOID, -1, 0);
+
+		/* prepare for projection of tuple */
+		tstate = begin_tup_output_tupdesc(dest, tupdesc, &TTSOpsVirtual);
+
+		values[0] = Int64GetDatum((int64) sendTimeLineNextTLI);
+		values[1] = CStringGetTextDatum(startpos_str);
+
+		/* send it to dest */
+		do_tup_output(tstate, values, nulls);
+
+		end_tup_output(tstate);
+	}
+
+	/* Send CommandComplete message */
+	EndReplicationCommand("START_STREAMING");
+}
+
+/*
+ * XLogReaderRoutine->page_read callback for logical decoding contexts, as a
+ * walsender process.
+ *
+ * Inside the walsender we can do better than read_local_xlog_page,
+ * which has to do a plain sleep/busy loop, because the walsender's latch gets
+ * set every time WAL is flushed.
+ */
+static int
+logical_read_xlog_page(XLogReaderState *state, XLogRecPtr targetPagePtr, int reqLen,
+					   XLogRecPtr targetRecPtr, char *cur_page)
+{
+	XLogRecPtr	flushptr;
+	int			count;
+	WALReadError errinfo;
+	XLogSegNo	segno;
+
+	XLogReadDetermineTimeline(state, targetPagePtr, reqLen);
+	sendTimeLineIsHistoric = (state->currTLI != ThisTimeLineID);
+	sendTimeLine = state->currTLI;
+	sendTimeLineValidUpto = state->currTLIValidUntil;
+	sendTimeLineNextTLI = state->nextTLI;
+
+	/* make sure we have enough WAL available */
+	flushptr = WalSndWaitForWal(targetPagePtr + reqLen);
+
+	/* fail if not (implies we are going to shut down) */
+	if (flushptr < targetPagePtr + reqLen)
+		return -1;
+
+	if (targetPagePtr + XLOG_BLCKSZ <= flushptr)
+		count = XLOG_BLCKSZ;	/* more than one block available */
+	else
+		count = flushptr - targetPagePtr;	/* part of the page available */
+
+	/* now actually read the data, we know it's there */
+	if (!WALRead(state,
+				 cur_page,
+				 targetPagePtr,
+				 XLOG_BLCKSZ,
+				 state->seg.ws_tli, /* Pass the current TLI because only
+									 * WalSndSegmentOpen controls whether new
+									 * TLI is needed. */
+				 &errinfo))
+		WALReadRaiseError(&errinfo);
+
+	/*
+	 * After reading into the buffer, check that what we read was valid. We do
+	 * this after reading, because even though the segment was present when we
+	 * opened it, it might get recycled or removed while we read it. The
+	 * read() succeeds in that case, but the data we tried to read might
+	 * already have been overwritten with new WAL records.
+	 */
+	XLByteToSeg(targetPagePtr, segno, state->segcxt.ws_segsize);
+	CheckXLogRemoved(segno, state->seg.ws_tli);
+
+	return count;
+}
+
+/*
+ * Process extra options given to CREATE_REPLICATION_SLOT.
+ */
+static void
+parseCreateReplSlotOptions(CreateReplicationSlotCmd *cmd,
+						   bool *reserve_wal,
+						   CRSSnapshotAction *snapshot_action)
+{
+	ListCell   *lc;
+	bool		snapshot_action_given = false;
+	bool		reserve_wal_given = false;
+
+	/* Parse options */
+	foreach(lc, cmd->options)
+	{
+		DefElem    *defel = (DefElem *) lfirst(lc);
+
+		if (strcmp(defel->defname, "export_snapshot") == 0)
+		{
+			if (snapshot_action_given || cmd->kind != REPLICATION_KIND_LOGICAL)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options")));
+
+			snapshot_action_given = true;
+			*snapshot_action = defGetBoolean(defel) ? CRS_EXPORT_SNAPSHOT :
+				CRS_NOEXPORT_SNAPSHOT;
+		}
+		else if (strcmp(defel->defname, "use_snapshot") == 0)
+		{
+			if (snapshot_action_given || cmd->kind != REPLICATION_KIND_LOGICAL)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options")));
+
+			snapshot_action_given = true;
+			*snapshot_action = CRS_USE_SNAPSHOT;
+		}
+		else if (strcmp(defel->defname, "reserve_wal") == 0)
+		{
+			if (reserve_wal_given || cmd->kind != REPLICATION_KIND_PHYSICAL)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options")));
+
+			reserve_wal_given = true;
+			*reserve_wal = true;
+		}
+		else
+			elog(ERROR, "unrecognized option: %s", defel->defname);
+	}
+}
+
+/*
+ * Create a new replication slot.
+ */
+static void
+CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
+{
+	const char *snapshot_name = NULL;
+	char		xloc[MAXFNAMELEN];
+	char	   *slot_name;
+	bool		reserve_wal = false;
+	CRSSnapshotAction snapshot_action = CRS_EXPORT_SNAPSHOT;
+	DestReceiver *dest;
+	TupOutputState *tstate;
+	TupleDesc	tupdesc;
+	Datum		values[4];
+	bool		nulls[4];
+
+	Assert(!MyReplicationSlot);
+
+	parseCreateReplSlotOptions(cmd, &reserve_wal, &snapshot_action);
+
+	/* setup state for WalSndSegmentOpen */
+	sendTimeLineIsHistoric = false;
+	sendTimeLine = ThisTimeLineID;
+
+	if (cmd->kind == REPLICATION_KIND_PHYSICAL)
+	{
+		ReplicationSlotCreate(cmd->slotname, false,
+							  cmd->temporary ? RS_TEMPORARY : RS_PERSISTENT,
+							  false);
+	}
+	else
+	{
+		CheckLogicalDecodingRequirements();
+
+		/*
+		 * Initially create persistent slot as ephemeral - that allows us to
+		 * nicely handle errors during initialization because it'll get
+		 * dropped if this transaction fails. We'll make it persistent at the
+		 * end. Temporary slots can be created as temporary from beginning as
+		 * they get dropped on error as well.
+		 */
+		ReplicationSlotCreate(cmd->slotname, true,
+							  cmd->temporary ? RS_TEMPORARY : RS_EPHEMERAL,
+							  false);
+	}
+
+	if (cmd->kind == REPLICATION_KIND_LOGICAL)
+	{
+		LogicalDecodingContext *ctx;
+		bool		need_full_snapshot = false;
+
+		/*
+		 * Do options check early so that we can bail before calling the
+		 * DecodingContextFindStartpoint which can take long time.
+		 */
+		if (snapshot_action == CRS_EXPORT_SNAPSHOT)
+		{
+			if (IsTransactionBlock())
+				ereport(ERROR,
+				/*- translator: %s is a CREATE_REPLICATION_SLOT statement */
+						(errmsg("%s must not be called inside a transaction",
+								"CREATE_REPLICATION_SLOT ... EXPORT_SNAPSHOT")));
+
+			need_full_snapshot = true;
+		}
+		else if (snapshot_action == CRS_USE_SNAPSHOT)
+		{
+			if (!IsTransactionBlock())
+				ereport(ERROR,
+				/*- translator: %s is a CREATE_REPLICATION_SLOT statement */
+						(errmsg("%s must be called inside a transaction",
+								"CREATE_REPLICATION_SLOT ... USE_SNAPSHOT")));
+
+			if (XactIsoLevel != XACT_REPEATABLE_READ)
+				ereport(ERROR,
+				/*- translator: %s is a CREATE_REPLICATION_SLOT statement */
+						(errmsg("%s must be called in REPEATABLE READ isolation mode transaction",
+								"CREATE_REPLICATION_SLOT ... USE_SNAPSHOT")));
+
+			if (FirstSnapshotSet)
+				ereport(ERROR,
+				/*- translator: %s is a CREATE_REPLICATION_SLOT statement */
+						(errmsg("%s must be called before any query",
+								"CREATE_REPLICATION_SLOT ... USE_SNAPSHOT")));
+
+			if (IsSubTransaction())
+				ereport(ERROR,
+				/*- translator: %s is a CREATE_REPLICATION_SLOT statement */
+						(errmsg("%s must not be called in a subtransaction",
+								"CREATE_REPLICATION_SLOT ... USE_SNAPSHOT")));
+
+			need_full_snapshot = true;
+		}
+
+		ctx = CreateInitDecodingContext(cmd->plugin, NIL, need_full_snapshot,
+										InvalidXLogRecPtr,
+										XL_ROUTINE(.page_read = logical_read_xlog_page,
+												   .segment_open = WalSndSegmentOpen,
+												   .segment_close = wal_segment_close),
+										WalSndPrepareWrite, WalSndWriteData,
+										WalSndUpdateProgress);
+
+		/*
+		 * Signal that we don't need the timeout mechanism. We're just
+		 * creating the replication slot and don't yet accept feedback
+		 * messages or send keepalives. As we possibly need to wait for
+		 * further WAL the walsender would otherwise possibly be killed too
+		 * soon.
+		 */
+		last_reply_timestamp = 0;
+
+		/* build initial snapshot, might take a while */
+		DecodingContextFindStartpoint(ctx);
+
+		/*
+		 * Export or use the snapshot if we've been asked to do so.
+		 *
+		 * NB. We will convert the snapbuild.c kind of snapshot to normal
+		 * snapshot when doing this.
+		 */
+		if (snapshot_action == CRS_EXPORT_SNAPSHOT)
+		{
+			snapshot_name = SnapBuildExportSnapshot(ctx->snapshot_builder);
+		}
+		else if (snapshot_action == CRS_USE_SNAPSHOT)
+		{
+			Snapshot	snap;
+
+			snap = SnapBuildInitialSnapshot(ctx->snapshot_builder);
+			RestoreTransactionSnapshot(snap, MyProc);
+		}
+
+		/* don't need the decoding context anymore */
+		FreeDecodingContext(ctx);
+
+		if (!cmd->temporary)
+			ReplicationSlotPersist();
+	}
+	else if (cmd->kind == REPLICATION_KIND_PHYSICAL && reserve_wal)
+	{
+		ReplicationSlotReserveWal();
+
+		ReplicationSlotMarkDirty();
+
+		/* Write this slot to disk if it's a permanent one. */
+		if (!cmd->temporary)
+			ReplicationSlotSave();
+	}
+
+	snprintf(xloc, sizeof(xloc), "%X/%X",
+			 LSN_FORMAT_ARGS(MyReplicationSlot->data.confirmed_flush));
+
+	dest = CreateDestReceiver(DestRemoteSimple);
+	MemSet(nulls, false, sizeof(nulls));
+
+	/*----------
+	 * Need a tuple descriptor representing four columns:
+	 * - first field: the slot name
+	 * - second field: LSN at which we became consistent
+	 * - third field: exported snapshot's name
+	 * - fourth field: output plugin
+	 *----------
+	 */
+	tupdesc = CreateTemplateTupleDesc(4);
+	TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 1, "slot_name",
+							  TEXTOID, -1, 0);
+	TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 2, "consistent_point",
+							  TEXTOID, -1, 0);
+	TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 3, "snapshot_name",
+							  TEXTOID, -1, 0);
+	TupleDescInitBuiltinEntry(tupdesc, (AttrNumber) 4, "output_plugin",
+							  TEXTOID, -1, 0);
+
+	/* prepare for projection of tuples */
+	tstate = begin_tup_output_tupdesc(dest, tupdesc, &TTSOpsVirtual);
+
+	/* slot_name */
+	slot_name = NameStr(MyReplicationSlot->data.name);
+	values[0] = CStringGetTextDatum(slot_name);
+
+	/* consistent wal location */
+	values[1] = CStringGetTextDatum(xloc);
+
+	/* snapshot name, or NULL if none */
+	if (snapshot_name != NULL)
+		values[2] = CStringGetTextDatum(snapshot_name);
+	else
+		nulls[2] = true;
+
+	/* plugin, or NULL if none */
+	if (cmd->plugin != NULL)
+		values[3] = CStringGetTextDatum(cmd->plugin);
+	else
+		nulls[3] = true;
+
+	/* send it to dest */
+	do_tup_output(tstate, values, nulls);
+	end_tup_output(tstate);
+
+	ReplicationSlotRelease();
+}
+
+/*
+ * Get rid of a replication slot that is no longer wanted.
+ */
+static void
+DropReplicationSlot(DropReplicationSlotCmd *cmd)
+{
+	ReplicationSlotDrop(cmd->slotname, !cmd->wait);
+}
+
+/*
+ * Load previously initiated logical slot and prepare for sending data (via
+ * WalSndLoop).
+ */
+static void
+StartLogicalReplication(StartReplicationCmd *cmd)
+{
+	StringInfoData buf;
+	QueryCompletion qc;
+
+	/* make sure that our requirements are still fulfilled */
+	CheckLogicalDecodingRequirements();
+
+	Assert(!MyReplicationSlot);
+
+	ReplicationSlotAcquire(cmd->slotname, true);
+
+	if (XLogRecPtrIsInvalid(MyReplicationSlot->data.restart_lsn))
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("cannot read from logical replication slot \"%s\"",
+						cmd->slotname),
+				 errdetail("This slot has been invalidated because it exceeded the maximum reserved size.")));
+
+	/*
+	 * Force a disconnect, so that the decoding code doesn't need to care
+	 * about an eventual switch from running in recovery, to running in a
+	 * normal environment. Client code is expected to handle reconnects.
+	 */
+	if (am_cascading_walsender && !RecoveryInProgress())
+	{
+		ereport(LOG,
+				(errmsg("terminating walsender process after promotion")));
+		got_STOPPING = true;
+	}
+
+	/*
+	 * Create our decoding context, making it start at the previously ack'ed
+	 * position.
+	 *
+	 * Do this before sending a CopyBothResponse message, so that any errors
+	 * are reported early.
+	 */
+	logical_decoding_ctx =
+		CreateDecodingContext(cmd->startpoint, cmd->options, false,
+							  XL_ROUTINE(.page_read = logical_read_xlog_page,
+										 .segment_open = WalSndSegmentOpen,
+										 .segment_close = wal_segment_close),
+							  WalSndPrepareWrite, WalSndWriteData,
+							  WalSndUpdateProgress);
+	xlogreader = logical_decoding_ctx->reader;
+
+	WalSndSetState(WALSNDSTATE_CATCHUP);
+
+	/* Send a CopyBothResponse message, and start streaming */
+	pq_beginmessage(&buf, 'W');
+	pq_sendbyte(&buf, 0);
+	pq_sendint16(&buf, 0);
+	pq_endmessage(&buf);
+	pq_flush();
+
+	/* Start reading WAL from the oldest required WAL. */
+	XLogBeginRead(logical_decoding_ctx->reader,
+				  MyReplicationSlot->data.restart_lsn);
+
+	/*
+	 * Report the location after which we'll send out further commits as the
+	 * current sentPtr.
+	 */
+	sentPtr = MyReplicationSlot->data.confirmed_flush;
+
+	/* Also update the sent position status in shared memory */
+	SpinLockAcquire(&MyWalSnd->mutex);
+	MyWalSnd->sentPtr = MyReplicationSlot->data.restart_lsn;
+	SpinLockRelease(&MyWalSnd->mutex);
+
+	replication_active = true;
+
+	SyncRepInitConfig();
+
+	/* Main loop of walsender */
+	WalSndLoop(XLogSendLogical);
+
+	FreeDecodingContext(logical_decoding_ctx);
+	ReplicationSlotRelease();
+
+	replication_active = false;
+	if (got_STOPPING)
+		proc_exit(0);
+	WalSndSetState(WALSNDSTATE_STARTUP);
+
+	/* Get out of COPY mode (CommandComplete). */
+	SetQueryCompletion(&qc, CMDTAG_COPY, 0);
+	EndCommand(&qc, DestRemote, false);
+}
+
+/*
+ * LogicalDecodingContext 'prepare_write' callback.
+ *
+ * Prepare a write into a StringInfo.
+ *
+ * Don't do anything lasting in here, it's quite possible that nothing will be done
+ * with the data.
+ */
+static void
+WalSndPrepareWrite(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid, bool last_write)
+{
+	/* can't have sync rep confused by sending the same LSN several times */
+	if (!last_write)
+		lsn = InvalidXLogRecPtr;
+
+	resetStringInfo(ctx->out);
+
+	pq_sendbyte(ctx->out, 'w');
+	pq_sendint64(ctx->out, lsn);	/* dataStart */
+	pq_sendint64(ctx->out, lsn);	/* walEnd */
+
+	/*
+	 * Fill out the sendtime later, just as it's done in XLogSendPhysical, but
+	 * reserve space here.
+	 */
+	pq_sendint64(ctx->out, 0);	/* sendtime */
+}
+
+/*
+ * LogicalDecodingContext 'write' callback.
+ *
+ * Actually write out data previously prepared by WalSndPrepareWrite out to
+ * the network. Take as long as needed, but process replies from the other
+ * side and check timeouts during that.
+ */
+static void
+WalSndWriteData(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid,
+				bool last_write)
+{
+	TimestampTz now;
+
+	/*
+	 * Fill the send timestamp last, so that it is taken as late as possible.
+	 * This is somewhat ugly, but the protocol is set as it's already used for
+	 * several releases by streaming physical replication.
+	 */
+	resetStringInfo(&tmpbuf);
+	now = GetCurrentTimestamp();
+	pq_sendint64(&tmpbuf, now);
+	memcpy(&ctx->out->data[1 + sizeof(int64) + sizeof(int64)],
+		   tmpbuf.data, sizeof(int64));
+
+	/* output previously gathered data in a CopyData packet */
+	pq_putmessage_noblock('d', ctx->out->data, ctx->out->len);
+
+	CHECK_FOR_INTERRUPTS();
+
+	/* Try to flush pending output to the client */
+	if (pq_flush_if_writable() != 0)
+		WalSndShutdown();
+
+	/* Try taking fast path unless we get too close to walsender timeout. */
+	if (now < TimestampTzPlusMilliseconds(last_reply_timestamp,
+										  wal_sender_timeout / 2) &&
+		!pq_is_send_pending())
+	{
+		return;
+	}
+
+	/* If we have pending write here, go to slow path */
+	ProcessPendingWrites();
+}
+
+/*
+ * Wait until there is no pending write. Also process replies from the other
+ * side and check timeouts during that.
+ */
+static void
+ProcessPendingWrites(void)
+{
+	for (;;)
+	{
+		long		sleeptime;
+
+		/* Check for input from the client */
+		ProcessRepliesIfAny();
+
+		/* die if timeout was reached */
+		WalSndCheckTimeOut();
+
+		/* Send keepalive if the time has come */
+		WalSndKeepaliveIfNecessary();
+
+		if (!pq_is_send_pending())
+			break;
+
+		sleeptime = WalSndComputeSleeptime(GetCurrentTimestamp());
+
+		/* Sleep until something happens or we time out */
+		WalSndWait(WL_SOCKET_WRITEABLE | WL_SOCKET_READABLE, sleeptime,
+				   WAIT_EVENT_WAL_SENDER_WRITE_DATA);
+
+		/* Clear any already-pending wakeups */
+		ResetLatch(MyLatch);
+
+		CHECK_FOR_INTERRUPTS();
+
+		/* Process any requests or signals received recently */
+		if (ConfigReloadPending)
+		{
+			ConfigReloadPending = false;
+			ProcessConfigFile(PGC_SIGHUP);
+			SyncRepInitConfig();
+		}
+
+		/* Try to flush pending output to the client */
+		if (pq_flush_if_writable() != 0)
+			WalSndShutdown();
+	}
+
+	/* reactivate latch so WalSndLoop knows to continue */
+	SetLatch(MyLatch);
+}
+
+/*
+ * LogicalDecodingContext 'update_progress' callback.
+ *
+ * Write the current position to the lag tracker (see XLogSendPhysical).
+ */
+static void
+WalSndUpdateProgress(LogicalDecodingContext *ctx, XLogRecPtr lsn, TransactionId xid)
+{
+	static TimestampTz sendTime = 0;
+	TimestampTz now = GetCurrentTimestamp();
+	bool		end_xact = ctx->end_xact;
+
+	/*
+	 * Track lag no more than once per WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS to
+	 * avoid flooding the lag tracker when we commit frequently.
+	 *
+	 * We don't have a mechanism to get the ack for any LSN other than end
+	 * xact LSN from the downstream. So, we track lag only for end of
+	 * transaction LSN.
+	 */
+#define WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS	1000
+	if (end_xact && TimestampDifferenceExceeds(sendTime, now,
+											   WALSND_LOGICAL_LAG_TRACK_INTERVAL_MS))
+	{
+		LagTrackerWrite(lsn, now);
+		sendTime = now;
+	}
+
+	/*
+	 * Try to send a keepalive if required. We don't need to try sending keep
+	 * alive messages at the transaction end as that will be done at a later
+	 * point in time. This is required only for large transactions where we
+	 * don't send any changes to the downstream and the receiver can timeout
+	 * due to that.
+	 */
+	if (!end_xact &&
+		now >= TimestampTzPlusMilliseconds(last_reply_timestamp,
+										   wal_sender_timeout / 2))
+		ProcessPendingWrites();
+}
+
+/*
+ * Wait till WAL < loc is flushed to disk so it can be safely sent to client.
+ *
+ * Returns end LSN of flushed WAL.  Normally this will be >= loc, but
+ * if we detect a shutdown request (either from postmaster or client)
+ * we will return early, so caller must always check.
+ */
+static XLogRecPtr
+WalSndWaitForWal(XLogRecPtr loc)
+{
+	int			wakeEvents;
+	static XLogRecPtr RecentFlushPtr = InvalidXLogRecPtr;
+
+	/*
+	 * Fast path to avoid acquiring the spinlock in case we already know we
+	 * have enough WAL available. This is particularly interesting if we're
+	 * far behind.
+	 */
+	if (RecentFlushPtr != InvalidXLogRecPtr &&
+		loc <= RecentFlushPtr)
+		return RecentFlushPtr;
+
+	/* Get a more recent flush pointer. */
+	if (!RecoveryInProgress())
+		RecentFlushPtr = GetFlushRecPtr();
+	else
+		RecentFlushPtr = GetXLogReplayRecPtr(NULL);
+
+	for (;;)
+	{
+		long		sleeptime;
+
+		/* Clear any already-pending wakeups */
+		ResetLatch(MyLatch);
+
+		CHECK_FOR_INTERRUPTS();
+
+		/* Process any requests or signals received recently */
+		if (ConfigReloadPending)
+		{
+			ConfigReloadPending = false;
+			ProcessConfigFile(PGC_SIGHUP);
+			SyncRepInitConfig();
+		}
+
+		/* Check for input from the client */
+		ProcessRepliesIfAny();
+
+		/*
+		 * If we're shutting down, trigger pending WAL to be written out,
+		 * otherwise we'd possibly end up waiting for WAL that never gets
+		 * written, because walwriter has shut down already.
+		 */
+		if (got_STOPPING)
+			XLogBackgroundFlush();
+
+		/* Update our idea of the currently flushed position. */
+		if (!RecoveryInProgress())
+			RecentFlushPtr = GetFlushRecPtr();
+		else
+			RecentFlushPtr = GetXLogReplayRecPtr(NULL);
+
+		/*
+		 * If postmaster asked us to stop, don't wait anymore.
+		 *
+		 * It's important to do this check after the recomputation of
+		 * RecentFlushPtr, so we can send all remaining data before shutting
+		 * down.
+		 */
+		if (got_STOPPING)
+			break;
+
+		/*
+		 * We only send regular messages to the client for full decoded
+		 * transactions, but a synchronous replication and walsender shutdown
+		 * possibly are waiting for a later location. So, before sleeping, we
+		 * send a ping containing the flush location. If the receiver is
+		 * otherwise idle, this keepalive will trigger a reply. Processing the
+		 * reply will update these MyWalSnd locations.
+		 */
+		if (MyWalSnd->flush < sentPtr &&
+			MyWalSnd->write < sentPtr &&
+			!waiting_for_ping_response)
+			WalSndKeepalive(false);
+
+		/* check whether we're done */
+		if (loc <= RecentFlushPtr)
+			break;
+
+		/* Waiting for new WAL. Since we need to wait, we're now caught up. */
+		WalSndCaughtUp = true;
+
+		/*
+		 * Try to flush any pending output to the client.
+		 */
+		if (pq_flush_if_writable() != 0)
+			WalSndShutdown();
+
+		/*
+		 * If we have received CopyDone from the client, sent CopyDone
+		 * ourselves, and the output buffer is empty, it's time to exit
+		 * streaming, so fail the current WAL fetch request.
+		 */
+		if (streamingDoneReceiving && streamingDoneSending &&
+			!pq_is_send_pending())
+			break;
+
+		/* die if timeout was reached */
+		WalSndCheckTimeOut();
+
+		/* Send keepalive if the time has come */
+		WalSndKeepaliveIfNecessary();
+
+		/*
+		 * Sleep until something happens or we time out.  Also wait for the
+		 * socket becoming writable, if there's still pending output.
+		 * Otherwise we might sit on sendable output data while waiting for
+		 * new WAL to be generated.  (But if we have nothing to send, we don't
+		 * want to wake on socket-writable.)
+		 */
+		sleeptime = WalSndComputeSleeptime(GetCurrentTimestamp());
+
+		wakeEvents = WL_SOCKET_READABLE;
+
+		if (pq_is_send_pending())
+			wakeEvents |= WL_SOCKET_WRITEABLE;
+
+		WalSndWait(wakeEvents, sleeptime, WAIT_EVENT_WAL_SENDER_WAIT_WAL);
+	}
+
+	/* reactivate latch so WalSndLoop knows to continue */
+	SetLatch(MyLatch);
+	return RecentFlushPtr;
+}
+
+/*
+ * Execute an incoming replication command.
+ *
+ * Returns true if the cmd_string was recognized as WalSender command, false
+ * if not.
+ */
+bool
+exec_replication_command(const char *cmd_string)
+{
+	int			parse_rc;
+	Node	   *cmd_node;
+	const char *cmdtag;
+	MemoryContext cmd_context;
+	MemoryContext old_context;
+
+	/*
+	 * If WAL sender has been told that shutdown is getting close, switch its
+	 * status accordingly to handle the next replication commands correctly.
+	 */
+	if (got_STOPPING)
+		WalSndSetState(WALSNDSTATE_STOPPING);
+
+	/*
+	 * Throw error if in stopping mode.  We need prevent commands that could
+	 * generate WAL while the shutdown checkpoint is being written.  To be
+	 * safe, we just prohibit all new commands.
+	 */
+	if (MyWalSnd->state == WALSNDSTATE_STOPPING)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("cannot execute new commands while WAL sender is in stopping mode")));
+
+	/*
+	 * CREATE_REPLICATION_SLOT ... LOGICAL exports a snapshot until the next
+	 * command arrives. Clean up the old stuff if there's anything.
+	 */
+	SnapBuildClearExportedSnapshot();
+
+	CHECK_FOR_INTERRUPTS();
+
+	/*
+	 * Prepare to parse and execute the command.
+	 */
+	cmd_context = AllocSetContextCreate(CurrentMemoryContext,
+										"Replication command context",
+										ALLOCSET_DEFAULT_SIZES);
+	old_context = MemoryContextSwitchTo(cmd_context);
+
+	replication_scanner_init(cmd_string);
+
+	/*
+	 * Is it a WalSender command?
+	 */
+	if (!replication_scanner_is_replication_command())
+	{
+		/* Nope; clean up and get out. */
+		replication_scanner_finish();
+
+		MemoryContextSwitchTo(old_context);
+		MemoryContextDelete(cmd_context);
+
+		/* XXX this is a pretty random place to make this check */
+		if (MyDatabaseId == InvalidOid)
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("cannot execute SQL commands in WAL sender for physical replication")));
+
+		/* Tell the caller that this wasn't a WalSender command. */
+		return false;
+	}
+
+	/*
+	 * Looks like a WalSender command, so parse it.
+	 */
+	parse_rc = replication_yyparse();
+	if (parse_rc != 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg_internal("replication command parser returned %d",
+								 parse_rc)));
+	replication_scanner_finish();
+
+	cmd_node = replication_parse_result;
+
+	/*
+	 * Report query to various monitoring facilities.  For this purpose, we
+	 * report replication commands just like SQL commands.
+	 */
+	debug_query_string = cmd_string;
+
+	pgstat_report_activity(STATE_RUNNING, cmd_string);
+
+	/*
+	 * Log replication command if log_replication_commands is enabled. Even
+	 * when it's disabled, log the command with DEBUG1 level for backward
+	 * compatibility.
+	 */
+	ereport(log_replication_commands ? LOG : DEBUG1,
+			(errmsg("received replication command: %s", cmd_string)));
+
+	/*
+	 * Disallow replication commands in aborted transaction blocks.
+	 */
+	if (IsAbortedTransactionBlockState())
+		ereport(ERROR,
+				(errcode(ERRCODE_IN_FAILED_SQL_TRANSACTION),
+				 errmsg("current transaction is aborted, "
+						"commands ignored until end of transaction block")));
+
+	CHECK_FOR_INTERRUPTS();
+
+	/*
+	 * Allocate buffers that will be used for each outgoing and incoming
+	 * message.  We do this just once per command to reduce palloc overhead.
+	 */
+	initStringInfo(&output_message);
+	initStringInfo(&reply_message);
+	initStringInfo(&tmpbuf);
+
+	switch (cmd_node->type)
+	{
+		case T_IdentifySystemCmd:
+			cmdtag = "IDENTIFY_SYSTEM";
+			set_ps_display(cmdtag);
+			IdentifySystem();
+			EndReplicationCommand(cmdtag);
+			break;
+
+		case T_BaseBackupCmd:
+			cmdtag = "BASE_BACKUP";
+			set_ps_display(cmdtag);
+			PreventInTransactionBlock(true, cmdtag);
+			SendBaseBackup((BaseBackupCmd *) cmd_node);
+			EndReplicationCommand(cmdtag);
+			break;
+
+		case T_CreateReplicationSlotCmd:
+			cmdtag = "CREATE_REPLICATION_SLOT";
+			set_ps_display(cmdtag);
+			CreateReplicationSlot((CreateReplicationSlotCmd *) cmd_node);
+			EndReplicationCommand(cmdtag);
+			break;
+
+		case T_DropReplicationSlotCmd:
+			cmdtag = "DROP_REPLICATION_SLOT";
+			set_ps_display(cmdtag);
+			DropReplicationSlot((DropReplicationSlotCmd *) cmd_node);
+			EndReplicationCommand(cmdtag);
+			break;
+
+		case T_StartReplicationCmd:
+			{
+				StartReplicationCmd *cmd = (StartReplicationCmd *) cmd_node;
+
+				cmdtag = "START_REPLICATION";
+				set_ps_display(cmdtag);
+				PreventInTransactionBlock(true, cmdtag);
+
+				if (cmd->kind == REPLICATION_KIND_PHYSICAL)
+					StartReplication(cmd);
+				else
+					StartLogicalReplication(cmd);
+
+				/* dupe, but necessary per libpqrcv_endstreaming */
+				EndReplicationCommand(cmdtag);
+
+				Assert(xlogreader != NULL);
+				break;
+			}
+
+		case T_TimeLineHistoryCmd:
+			cmdtag = "TIMELINE_HISTORY";
+			set_ps_display(cmdtag);
+			PreventInTransactionBlock(true, cmdtag);
+			SendTimeLineHistory((TimeLineHistoryCmd *) cmd_node);
+			EndReplicationCommand(cmdtag);
+			break;
+
+		case T_VariableShowStmt:
+			{
+				DestReceiver *dest = CreateDestReceiver(DestRemoteSimple);
+				VariableShowStmt *n = (VariableShowStmt *) cmd_node;
+
+				cmdtag = "SHOW";
+				set_ps_display(cmdtag);
+
+				/* syscache access needs a transaction environment */
+				StartTransactionCommand();
+				GetPGVariable(n->name, dest);
+				CommitTransactionCommand();
+				EndReplicationCommand(cmdtag);
+			}
+			break;
+
+		default:
+			elog(ERROR, "unrecognized replication command node tag: %u",
+				 cmd_node->type);
+	}
+
+	/* done */
+	MemoryContextSwitchTo(old_context);
+	MemoryContextDelete(cmd_context);
+
+	/*
+	 * We need not update ps display or pg_stat_activity, because PostgresMain
+	 * will reset those to "idle".  But we must reset debug_query_string to
+	 * ensure it doesn't become a dangling pointer.
+	 */
+	debug_query_string = NULL;
+
+	return true;
+}
+
+/*
+ * Process any incoming messages while streaming. Also checks if the remote
+ * end has closed the connection.
+ */
+static void
+ProcessRepliesIfAny(void)
+{
+	unsigned char firstchar;
+	int			maxmsglen;
+	int			r;
+	bool		received = false;
+
+	last_processing = GetCurrentTimestamp();
+
+	/*
+	 * If we already received a CopyDone from the frontend, any subsequent
+	 * message is the beginning of a new command, and should be processed in
+	 * the main processing loop.
+	 */
+	while (!streamingDoneReceiving)
+	{
+		pq_startmsgread();
+		r = pq_getbyte_if_available(&firstchar);
+		if (r < 0)
+		{
+			/* unexpected error or EOF */
+			ereport(COMMERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("unexpected EOF on standby connection")));
+			proc_exit(0);
+		}
+		if (r == 0)
+		{
+			/* no data available without blocking */
+			pq_endmsgread();
+			break;
+		}
+
+		/* Validate message type and set packet size limit */
+		switch (firstchar)
+		{
+			case 'd':
+				maxmsglen = PQ_LARGE_MESSAGE_LIMIT;
+				break;
+			case 'c':
+			case 'X':
+				maxmsglen = PQ_SMALL_MESSAGE_LIMIT;
+				break;
+			default:
+				ereport(FATAL,
+						(errcode(ERRCODE_PROTOCOL_VIOLATION),
+						 errmsg("invalid standby message type \"%c\"",
+								firstchar)));
+				maxmsglen = 0;	/* keep compiler quiet */
+				break;
+		}
+
+		/* Read the message contents */
+		resetStringInfo(&reply_message);
+		if (pq_getmessage(&reply_message, maxmsglen))
+		{
+			ereport(COMMERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("unexpected EOF on standby connection")));
+			proc_exit(0);
+		}
+
+		/* ... and process it */
+		switch (firstchar)
+		{
+				/*
+				 * 'd' means a standby reply wrapped in a CopyData packet.
+				 */
+			case 'd':
+				ProcessStandbyMessage();
+				received = true;
+				break;
+
+				/*
+				 * CopyDone means the standby requested to finish streaming.
+				 * Reply with CopyDone, if we had not sent that already.
+				 */
+			case 'c':
+				if (!streamingDoneSending)
+				{
+					pq_putmessage_noblock('c', NULL, 0);
+					streamingDoneSending = true;
+				}
+
+				streamingDoneReceiving = true;
+				received = true;
+				break;
+
+				/*
+				 * 'X' means that the standby is closing down the socket.
+				 */
+			case 'X':
+				proc_exit(0);
+
+			default:
+				Assert(false);	/* NOT REACHED */
+		}
+	}
+
+	/*
+	 * Save the last reply timestamp if we've received at least one reply.
+	 */
+	if (received)
+	{
+		last_reply_timestamp = last_processing;
+		waiting_for_ping_response = false;
+	}
+}
+
+/*
+ * Process a status update message received from standby.
+ */
+static void
+ProcessStandbyMessage(void)
+{
+	char		msgtype;
+
+	/*
+	 * Check message type from the first byte.
+	 */
+	msgtype = pq_getmsgbyte(&reply_message);
+
+	switch (msgtype)
+	{
+		case 'r':
+			ProcessStandbyReplyMessage();
+			break;
+
+		case 'h':
+			ProcessStandbyHSFeedbackMessage();
+			break;
+
+		default:
+			ereport(COMMERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("unexpected message type \"%c\"", msgtype)));
+			proc_exit(0);
+	}
+}
+
+/*
+ * Remember that a walreceiver just confirmed receipt of lsn `lsn`.
+ */
+static void
+PhysicalConfirmReceivedLocation(XLogRecPtr lsn)
+{
+	bool		changed = false;
+	ReplicationSlot *slot = MyReplicationSlot;
+
+	Assert(lsn != InvalidXLogRecPtr);
+	SpinLockAcquire(&slot->mutex);
+	if (slot->data.restart_lsn != lsn)
+	{
+		changed = true;
+		slot->data.restart_lsn = lsn;
+	}
+	SpinLockRelease(&slot->mutex);
+
+	if (changed)
+	{
+		ReplicationSlotMarkDirty();
+		ReplicationSlotsComputeRequiredLSN();
+	}
+
+	/*
+	 * One could argue that the slot should be saved to disk now, but that'd
+	 * be energy wasted - the worst lost information can do here is give us
+	 * wrong information in a statistics view - we'll just potentially be more
+	 * conservative in removing files.
+	 */
+}
+
+/*
+ * Regular reply from standby advising of WAL locations on standby server.
+ */
+static void
+ProcessStandbyReplyMessage(void)
+{
+	XLogRecPtr	writePtr,
+				flushPtr,
+				applyPtr;
+	bool		replyRequested;
+	TimeOffset	writeLag,
+				flushLag,
+				applyLag;
+	bool		clearLagTimes;
+	TimestampTz now;
+	TimestampTz replyTime;
+
+	static bool fullyAppliedLastTime = false;
+
+	/* the caller already consumed the msgtype byte */
+	writePtr = pq_getmsgint64(&reply_message);
+	flushPtr = pq_getmsgint64(&reply_message);
+	applyPtr = pq_getmsgint64(&reply_message);
+	replyTime = pq_getmsgint64(&reply_message);
+	replyRequested = pq_getmsgbyte(&reply_message);
+
+	if (message_level_is_interesting(DEBUG2))
+	{
+		char	   *replyTimeStr;
+
+		/* Copy because timestamptz_to_str returns a static buffer */
+		replyTimeStr = pstrdup(timestamptz_to_str(replyTime));
+
+		elog(DEBUG2, "write %X/%X flush %X/%X apply %X/%X%s reply_time %s",
+			 LSN_FORMAT_ARGS(writePtr),
+			 LSN_FORMAT_ARGS(flushPtr),
+			 LSN_FORMAT_ARGS(applyPtr),
+			 replyRequested ? " (reply requested)" : "",
+			 replyTimeStr);
+
+		pfree(replyTimeStr);
+	}
+
+	/* See if we can compute the round-trip lag for these positions. */
+	now = GetCurrentTimestamp();
+	writeLag = LagTrackerRead(SYNC_REP_WAIT_WRITE, writePtr, now);
+	flushLag = LagTrackerRead(SYNC_REP_WAIT_FLUSH, flushPtr, now);
+	applyLag = LagTrackerRead(SYNC_REP_WAIT_APPLY, applyPtr, now);
+
+	/*
+	 * If the standby reports that it has fully replayed the WAL in two
+	 * consecutive reply messages, then the second such message must result
+	 * from wal_receiver_status_interval expiring on the standby.  This is a
+	 * convenient time to forget the lag times measured when it last
+	 * wrote/flushed/applied a WAL record, to avoid displaying stale lag data
+	 * until more WAL traffic arrives.
+	 */
+	clearLagTimes = false;
+	if (applyPtr == sentPtr)
+	{
+		if (fullyAppliedLastTime)
+			clearLagTimes = true;
+		fullyAppliedLastTime = true;
+	}
+	else
+		fullyAppliedLastTime = false;
+
+	/* Send a reply if the standby requested one. */
+	if (replyRequested)
+		WalSndKeepalive(false);
+
+	/*
+	 * Update shared state for this WalSender process based on reply data from
+	 * standby.
+	 */
+	{
+		WalSnd	   *walsnd = MyWalSnd;
+
+		SpinLockAcquire(&walsnd->mutex);
+		walsnd->write = writePtr;
+		walsnd->flush = flushPtr;
+		walsnd->apply = applyPtr;
+		if (writeLag != -1 || clearLagTimes)
+			walsnd->writeLag = writeLag;
+		if (flushLag != -1 || clearLagTimes)
+			walsnd->flushLag = flushLag;
+		if (applyLag != -1 || clearLagTimes)
+			walsnd->applyLag = applyLag;
+		walsnd->replyTime = replyTime;
+		SpinLockRelease(&walsnd->mutex);
+	}
+
+	if (!am_cascading_walsender)
+		SyncRepReleaseWaiters();
+
+	/*
+	 * Advance our local xmin horizon when the client confirmed a flush.
+	 */
+	if (MyReplicationSlot && flushPtr != InvalidXLogRecPtr)
+	{
+		if (SlotIsLogical(MyReplicationSlot))
+			LogicalConfirmReceivedLocation(flushPtr);
+		else
+			PhysicalConfirmReceivedLocation(flushPtr);
+	}
+}
+
+/* compute new replication slot xmin horizon if needed */
+static void
+PhysicalReplicationSlotNewXmin(TransactionId feedbackXmin, TransactionId feedbackCatalogXmin)
+{
+	bool		changed = false;
+	ReplicationSlot *slot = MyReplicationSlot;
+
+	SpinLockAcquire(&slot->mutex);
+	MyProc->xmin = InvalidTransactionId;
+
+	/*
+	 * For physical replication we don't need the interlock provided by xmin
+	 * and effective_xmin since the consequences of a missed increase are
+	 * limited to query cancellations, so set both at once.
+	 */
+	if (!TransactionIdIsNormal(slot->data.xmin) ||
+		!TransactionIdIsNormal(feedbackXmin) ||
+		TransactionIdPrecedes(slot->data.xmin, feedbackXmin))
+	{
+		changed = true;
+		slot->data.xmin = feedbackXmin;
+		slot->effective_xmin = feedbackXmin;
+	}
+	if (!TransactionIdIsNormal(slot->data.catalog_xmin) ||
+		!TransactionIdIsNormal(feedbackCatalogXmin) ||
+		TransactionIdPrecedes(slot->data.catalog_xmin, feedbackCatalogXmin))
+	{
+		changed = true;
+		slot->data.catalog_xmin = feedbackCatalogXmin;
+		slot->effective_catalog_xmin = feedbackCatalogXmin;
+	}
+	SpinLockRelease(&slot->mutex);
+
+	if (changed)
+	{
+		ReplicationSlotMarkDirty();
+		ReplicationSlotsComputeRequiredXmin(false);
+	}
+}
+
+/*
+ * Check that the provided xmin/epoch are sane, that is, not in the future
+ * and not so far back as to be already wrapped around.
+ *
+ * Epoch of nextXid should be same as standby, or if the counter has
+ * wrapped, then one greater than standby.
+ *
+ * This check doesn't care about whether clog exists for these xids
+ * at all.
+ */
+static bool
+TransactionIdInRecentPast(TransactionId xid, uint32 epoch)
+{
+	FullTransactionId nextFullXid;
+	TransactionId nextXid;
+	uint32		nextEpoch;
+
+	nextFullXid = ReadNextFullTransactionId();
+	nextXid = XidFromFullTransactionId(nextFullXid);
+	nextEpoch = EpochFromFullTransactionId(nextFullXid);
+
+	if (xid <= nextXid)
+	{
+		if (epoch != nextEpoch)
+			return false;
+	}
+	else
+	{
+		if (epoch + 1 != nextEpoch)
+			return false;
+	}
+
+	if (!TransactionIdPrecedesOrEquals(xid, nextXid))
+		return false;			/* epoch OK, but it's wrapped around */
+
+	return true;
+}
+
+/*
+ * Hot Standby feedback
+ */
+static void
+ProcessStandbyHSFeedbackMessage(void)
+{
+	TransactionId feedbackXmin;
+	uint32		feedbackEpoch;
+	TransactionId feedbackCatalogXmin;
+	uint32		feedbackCatalogEpoch;
+	TimestampTz replyTime;
+
+	/*
+	 * Decipher the reply message. The caller already consumed the msgtype
+	 * byte. See XLogWalRcvSendHSFeedback() in walreceiver.c for the creation
+	 * of this message.
+	 */
+	replyTime = pq_getmsgint64(&reply_message);
+	feedbackXmin = pq_getmsgint(&reply_message, 4);
+	feedbackEpoch = pq_getmsgint(&reply_message, 4);
+	feedbackCatalogXmin = pq_getmsgint(&reply_message, 4);
+	feedbackCatalogEpoch = pq_getmsgint(&reply_message, 4);
+
+	if (message_level_is_interesting(DEBUG2))
+	{
+		char	   *replyTimeStr;
+
+		/* Copy because timestamptz_to_str returns a static buffer */
+		replyTimeStr = pstrdup(timestamptz_to_str(replyTime));
+
+		elog(DEBUG2, "hot standby feedback xmin %u epoch %u, catalog_xmin %u epoch %u reply_time %s",
+			 feedbackXmin,
+			 feedbackEpoch,
+			 feedbackCatalogXmin,
+			 feedbackCatalogEpoch,
+			 replyTimeStr);
+
+		pfree(replyTimeStr);
+	}
+
+	/*
+	 * Update shared state for this WalSender process based on reply data from
+	 * standby.
+	 */
+	{
+		WalSnd	   *walsnd = MyWalSnd;
+
+		SpinLockAcquire(&walsnd->mutex);
+		walsnd->replyTime = replyTime;
+		SpinLockRelease(&walsnd->mutex);
+	}
+
+	/*
+	 * Unset WalSender's xmins if the feedback message values are invalid.
+	 * This happens when the downstream turned hot_standby_feedback off.
+	 */
+	if (!TransactionIdIsNormal(feedbackXmin)
+		&& !TransactionIdIsNormal(feedbackCatalogXmin))
+	{
+		MyProc->xmin = InvalidTransactionId;
+		if (MyReplicationSlot != NULL)
+			PhysicalReplicationSlotNewXmin(feedbackXmin, feedbackCatalogXmin);
+		return;
+	}
+
+	/*
+	 * Check that the provided xmin/epoch are sane, that is, not in the future
+	 * and not so far back as to be already wrapped around.  Ignore if not.
+	 */
+	if (TransactionIdIsNormal(feedbackXmin) &&
+		!TransactionIdInRecentPast(feedbackXmin, feedbackEpoch))
+		return;
+
+	if (TransactionIdIsNormal(feedbackCatalogXmin) &&
+		!TransactionIdInRecentPast(feedbackCatalogXmin, feedbackCatalogEpoch))
+		return;
+
+	/*
+	 * Set the WalSender's xmin equal to the standby's requested xmin, so that
+	 * the xmin will be taken into account by GetSnapshotData() /
+	 * ComputeXidHorizons().  This will hold back the removal of dead rows and
+	 * thereby prevent the generation of cleanup conflicts on the standby
+	 * server.
+	 *
+	 * There is a small window for a race condition here: although we just
+	 * checked that feedbackXmin precedes nextXid, the nextXid could have
+	 * gotten advanced between our fetching it and applying the xmin below,
+	 * perhaps far enough to make feedbackXmin wrap around.  In that case the
+	 * xmin we set here would be "in the future" and have no effect.  No point
+	 * in worrying about this since it's too late to save the desired data
+	 * anyway.  Assuming that the standby sends us an increasing sequence of
+	 * xmins, this could only happen during the first reply cycle, else our
+	 * own xmin would prevent nextXid from advancing so far.
+	 *
+	 * We don't bother taking the ProcArrayLock here.  Setting the xmin field
+	 * is assumed atomic, and there's no real need to prevent concurrent
+	 * horizon determinations.  (If we're moving our xmin forward, this is
+	 * obviously safe, and if we're moving it backwards, well, the data is at
+	 * risk already since a VACUUM could already have determined the horizon.)
+	 *
+	 * If we're using a replication slot we reserve the xmin via that,
+	 * otherwise via the walsender's PGPROC entry. We can only track the
+	 * catalog xmin separately when using a slot, so we store the least of the
+	 * two provided when not using a slot.
+	 *
+	 * XXX: It might make sense to generalize the ephemeral slot concept and
+	 * always use the slot mechanism to handle the feedback xmin.
+	 */
+	if (MyReplicationSlot != NULL)	/* XXX: persistency configurable? */
+		PhysicalReplicationSlotNewXmin(feedbackXmin, feedbackCatalogXmin);
+	else
+	{
+		if (TransactionIdIsNormal(feedbackCatalogXmin)
+			&& TransactionIdPrecedes(feedbackCatalogXmin, feedbackXmin))
+			MyProc->xmin = feedbackCatalogXmin;
+		else
+			MyProc->xmin = feedbackXmin;
+	}
+}
+
+/*
+ * Compute how long send/receive loops should sleep.
+ *
+ * If wal_sender_timeout is enabled we want to wake up in time to send
+ * keepalives and to abort the connection if wal_sender_timeout has been
+ * reached.
+ */
+static long
+WalSndComputeSleeptime(TimestampTz now)
+{
+	long		sleeptime = 10000;	/* 10 s */
+
+	if (wal_sender_timeout > 0 && last_reply_timestamp > 0)
+	{
+		TimestampTz wakeup_time;
+
+		/*
+		 * At the latest stop sleeping once wal_sender_timeout has been
+		 * reached.
+		 */
+		wakeup_time = TimestampTzPlusMilliseconds(last_reply_timestamp,
+												  wal_sender_timeout);
+
+		/*
+		 * If no ping has been sent yet, wakeup when it's time to do so.
+		 * WalSndKeepaliveIfNecessary() wants to send a keepalive once half of
+		 * the timeout passed without a response.
+		 */
+		if (!waiting_for_ping_response)
+			wakeup_time = TimestampTzPlusMilliseconds(last_reply_timestamp,
+													  wal_sender_timeout / 2);
+
+		/* Compute relative time until wakeup. */
+		sleeptime = TimestampDifferenceMilliseconds(now, wakeup_time);
+	}
+
+	return sleeptime;
+}
+
+/*
+ * Check whether there have been responses by the client within
+ * wal_sender_timeout and shutdown if not.  Using last_processing as the
+ * reference point avoids counting server-side stalls against the client.
+ * However, a long server-side stall can make WalSndKeepaliveIfNecessary()
+ * postdate last_processing by more than wal_sender_timeout.  If that happens,
+ * the client must reply almost immediately to avoid a timeout.  This rarely
+ * affects the default configuration, under which clients spontaneously send a
+ * message every standby_message_timeout = wal_sender_timeout/6 = 10s.  We
+ * could eliminate that problem by recognizing timeout expiration at
+ * wal_sender_timeout/2 after the keepalive.
+ */
+static void
+WalSndCheckTimeOut(void)
+{
+	TimestampTz timeout;
+
+	/* don't bail out if we're doing something that doesn't require timeouts */
+	if (last_reply_timestamp <= 0)
+		return;
+
+	timeout = TimestampTzPlusMilliseconds(last_reply_timestamp,
+										  wal_sender_timeout);
+
+	if (wal_sender_timeout > 0 && last_processing >= timeout)
+	{
+		/*
+		 * Since typically expiration of replication timeout means
+		 * communication problem, we don't send the error message to the
+		 * standby.
+		 */
+		ereport(COMMERROR,
+				(errmsg("terminating walsender process due to replication timeout")));
+
+		WalSndShutdown();
+	}
+}
+
+/* Main loop of walsender process that streams the WAL over Copy messages. */
+static void
+WalSndLoop(WalSndSendDataCallback send_data)
+{
+	/*
+	 * Initialize the last reply timestamp. That enables timeout processing
+	 * from hereon.
+	 */
+	last_reply_timestamp = GetCurrentTimestamp();
+	waiting_for_ping_response = false;
+
+	/*
+	 * Loop until we reach the end of this timeline or the client requests to
+	 * stop streaming.
+	 */
+	for (;;)
+	{
+		/* Clear any already-pending wakeups */
+		ResetLatch(MyLatch);
+
+		CHECK_FOR_INTERRUPTS();
+
+		/* Process any requests or signals received recently */
+		if (ConfigReloadPending)
+		{
+			ConfigReloadPending = false;
+			ProcessConfigFile(PGC_SIGHUP);
+			SyncRepInitConfig();
+		}
+
+		/* Check for input from the client */
+		ProcessRepliesIfAny();
+
+		/*
+		 * If we have received CopyDone from the client, sent CopyDone
+		 * ourselves, and the output buffer is empty, it's time to exit
+		 * streaming.
+		 */
+		if (streamingDoneReceiving && streamingDoneSending &&
+			!pq_is_send_pending())
+			break;
+
+		/*
+		 * If we don't have any pending data in the output buffer, try to send
+		 * some more.  If there is some, we don't bother to call send_data
+		 * again until we've flushed it ... but we'd better assume we are not
+		 * caught up.
+		 */
+		if (!pq_is_send_pending())
+			send_data();
+		else
+			WalSndCaughtUp = false;
+
+		/* Try to flush pending output to the client */
+		if (pq_flush_if_writable() != 0)
+			WalSndShutdown();
+
+		/* If nothing remains to be sent right now ... */
+		if (WalSndCaughtUp && !pq_is_send_pending())
+		{
+			/*
+			 * If we're in catchup state, move to streaming.  This is an
+			 * important state change for users to know about, since before
+			 * this point data loss might occur if the primary dies and we
+			 * need to failover to the standby. The state change is also
+			 * important for synchronous replication, since commits that
+			 * started to wait at that point might wait for some time.
+			 */
+			if (MyWalSnd->state == WALSNDSTATE_CATCHUP)
+			{
+				ereport(DEBUG1,
+						(errmsg_internal("\"%s\" has now caught up with upstream server",
+										 application_name)));
+				WalSndSetState(WALSNDSTATE_STREAMING);
+			}
+
+			/*
+			 * When SIGUSR2 arrives, we send any outstanding logs up to the
+			 * shutdown checkpoint record (i.e., the latest record), wait for
+			 * them to be replicated to the standby, and exit. This may be a
+			 * normal termination at shutdown, or a promotion, the walsender
+			 * is not sure which.
+			 */
+			if (got_SIGUSR2)
+				WalSndDone(send_data);
+		}
+
+		/* Check for replication timeout. */
+		WalSndCheckTimeOut();
+
+		/* Send keepalive if the time has come */
+		WalSndKeepaliveIfNecessary();
+
+		/*
+		 * Block if we have unsent data.  XXX For logical replication, let
+		 * WalSndWaitForWal() handle any other blocking; idle receivers need
+		 * its additional actions.  For physical replication, also block if
+		 * caught up; its send_data does not block.
+		 */
+		if ((WalSndCaughtUp && send_data != XLogSendLogical &&
+			 !streamingDoneSending) ||
+			pq_is_send_pending())
+		{
+			long		sleeptime;
+			int			wakeEvents;
+
+			if (!streamingDoneReceiving)
+				wakeEvents = WL_SOCKET_READABLE;
+			else
+				wakeEvents = 0;
+
+			/*
+			 * Use fresh timestamp, not last_processing, to reduce the chance
+			 * of reaching wal_sender_timeout before sending a keepalive.
+			 */
+			sleeptime = WalSndComputeSleeptime(GetCurrentTimestamp());
+
+			if (pq_is_send_pending())
+				wakeEvents |= WL_SOCKET_WRITEABLE;
+
+			/* Sleep until something happens or we time out */
+			WalSndWait(wakeEvents, sleeptime, WAIT_EVENT_WAL_SENDER_MAIN);
+		}
+	}
+}
+
+/* Initialize a per-walsender data structure for this walsender process */
+static void
+InitWalSenderSlot(void)
+{
+	int			i;
+
+	/*
+	 * WalSndCtl should be set up already (we inherit this by fork() or
+	 * EXEC_BACKEND mechanism from the postmaster).
+	 */
+	Assert(WalSndCtl != NULL);
+	Assert(MyWalSnd == NULL);
+
+	/*
+	 * Find a free walsender slot and reserve it. This must not fail due to
+	 * the prior check for free WAL senders in InitProcess().
+	 */
+	for (i = 0; i < max_wal_senders; i++)
+	{
+		WalSnd	   *walsnd = &WalSndCtl->walsnds[i];
+
+		SpinLockAcquire(&walsnd->mutex);
+
+		if (walsnd->pid != 0)
+		{
+			SpinLockRelease(&walsnd->mutex);
+			continue;
+		}
+		else
+		{
+			/*
+			 * Found a free slot. Reserve it for us.
+			 */
+			walsnd->pid = MyProcPid;
+			walsnd->state = WALSNDSTATE_STARTUP;
+			walsnd->sentPtr = InvalidXLogRecPtr;
+			walsnd->needreload = false;
+			walsnd->write = InvalidXLogRecPtr;
+			walsnd->flush = InvalidXLogRecPtr;
+			walsnd->apply = InvalidXLogRecPtr;
+			walsnd->writeLag = -1;
+			walsnd->flushLag = -1;
+			walsnd->applyLag = -1;
+			walsnd->sync_standby_priority = 0;
+			walsnd->latch = &MyProc->procLatch;
+			walsnd->replyTime = 0;
+			SpinLockRelease(&walsnd->mutex);
+			/* don't need the lock anymore */
+			MyWalSnd = (WalSnd *) walsnd;
+
+			break;
+		}
+	}
+
+	Assert(MyWalSnd != NULL);
+
+	/* Arrange to clean up at walsender exit */
+	on_shmem_exit(WalSndKill, 0);
+}
+
+/* Destroy the per-walsender data structure for this walsender process */
+static void
+WalSndKill(int code, Datum arg)
+{
+	WalSnd	   *walsnd = MyWalSnd;
+
+	Assert(walsnd != NULL);
+
+	MyWalSnd = NULL;
+
+	SpinLockAcquire(&walsnd->mutex);
+	/* clear latch while holding the spinlock, so it can safely be read */
+	walsnd->latch = NULL;
+	/* Mark WalSnd struct as no longer being in use. */
+	walsnd->pid = 0;
+	SpinLockRelease(&walsnd->mutex);
+}
+
+/* XLogReaderRoutine->segment_open callback */
+static void
+WalSndSegmentOpen(XLogReaderState *state, XLogSegNo nextSegNo,
+				  TimeLineID *tli_p)
+{
+	char		path[MAXPGPATH];
+
+	/*-------
+	 * When reading from a historic timeline, and there is a timeline switch
+	 * within this segment, read from the WAL segment belonging to the new
+	 * timeline.
+	 *
+	 * For example, imagine that this server is currently on timeline 5, and
+	 * we're streaming timeline 4. The switch from timeline 4 to 5 happened at
+	 * 0/13002088. In pg_wal, we have these files:
+	 *
+	 * ...
+	 * 000000040000000000000012
+	 * 000000040000000000000013
+	 * 000000050000000000000013
+	 * 000000050000000000000014
+	 * ...
+	 *
+	 * In this situation, when requested to send the WAL from segment 0x13, on
+	 * timeline 4, we read the WAL from file 000000050000000000000013. Archive
+	 * recovery prefers files from newer timelines, so if the segment was
+	 * restored from the archive on this server, the file belonging to the old
+	 * timeline, 000000040000000000000013, might not exist. Their contents are
+	 * equal up to the switchpoint, because at a timeline switch, the used
+	 * portion of the old segment is copied to the new file.  -------
+	 */
+	*tli_p = sendTimeLine;
+	if (sendTimeLineIsHistoric)
+	{
+		XLogSegNo	endSegNo;
+
+		XLByteToSeg(sendTimeLineValidUpto, endSegNo, state->segcxt.ws_segsize);
+		if (nextSegNo == endSegNo)
+			*tli_p = sendTimeLineNextTLI;
+	}
+
+	XLogFilePath(path, *tli_p, nextSegNo, state->segcxt.ws_segsize);
+	state->seg.ws_file = BasicOpenFile(path, O_RDONLY | PG_BINARY);
+	if (state->seg.ws_file >= 0)
+		return;
+
+	/*
+	 * If the file is not found, assume it's because the standby asked for a
+	 * too old WAL segment that has already been removed or recycled.
+	 */
+	if (errno == ENOENT)
+	{
+		char		xlogfname[MAXFNAMELEN];
+		int			save_errno = errno;
+
+		XLogFileName(xlogfname, *tli_p, nextSegNo, wal_segment_size);
+		errno = save_errno;
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("requested WAL segment %s has already been removed",
+						xlogfname)));
+	}
+	else
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not open file \"%s\": %m",
+						path)));
+}
+
+/*
+ * Send out the WAL in its normal physical/stored form.
+ *
+ * Read up to MAX_SEND_SIZE bytes of WAL that's been flushed to disk,
+ * but not yet sent to the client, and buffer it in the libpq output
+ * buffer.
+ *
+ * If there is no unsent WAL remaining, WalSndCaughtUp is set to true,
+ * otherwise WalSndCaughtUp is set to false.
+ */
+static void
+XLogSendPhysical(void)
+{
+	XLogRecPtr	SendRqstPtr;
+	XLogRecPtr	startptr;
+	XLogRecPtr	endptr;
+	Size		nbytes;
+	XLogSegNo	segno;
+	WALReadError errinfo;
+
+	/* If requested switch the WAL sender to the stopping state. */
+	if (got_STOPPING)
+		WalSndSetState(WALSNDSTATE_STOPPING);
+
+	if (streamingDoneSending)
+	{
+		WalSndCaughtUp = true;
+		return;
+	}
+
+	/* Figure out how far we can safely send the WAL. */
+	if (sendTimeLineIsHistoric)
+	{
+		/*
+		 * Streaming an old timeline that's in this server's history, but is
+		 * not the one we're currently inserting or replaying. It can be
+		 * streamed up to the point where we switched off that timeline.
+		 */
+		SendRqstPtr = sendTimeLineValidUpto;
+	}
+	else if (am_cascading_walsender)
+	{
+		/*
+		 * Streaming the latest timeline on a standby.
+		 *
+		 * Attempt to send all WAL that has already been replayed, so that we
+		 * know it's valid. If we're receiving WAL through streaming
+		 * replication, it's also OK to send any WAL that has been received
+		 * but not replayed.
+		 *
+		 * The timeline we're recovering from can change, or we can be
+		 * promoted. In either case, the current timeline becomes historic. We
+		 * need to detect that so that we don't try to stream past the point
+		 * where we switched to another timeline. We check for promotion or
+		 * timeline switch after calculating FlushPtr, to avoid a race
+		 * condition: if the timeline becomes historic just after we checked
+		 * that it was still current, it's still be OK to stream it up to the
+		 * FlushPtr that was calculated before it became historic.
+		 */
+		bool		becameHistoric = false;
+
+		SendRqstPtr = GetStandbyFlushRecPtr();
+
+		if (!RecoveryInProgress())
+		{
+			/*
+			 * We have been promoted. RecoveryInProgress() updated
+			 * ThisTimeLineID to the new current timeline.
+			 */
+			am_cascading_walsender = false;
+			becameHistoric = true;
+		}
+		else
+		{
+			/*
+			 * Still a cascading standby. But is the timeline we're sending
+			 * still the one recovery is recovering from? ThisTimeLineID was
+			 * updated by the GetStandbyFlushRecPtr() call above.
+			 */
+			if (sendTimeLine != ThisTimeLineID)
+				becameHistoric = true;
+		}
+
+		if (becameHistoric)
+		{
+			/*
+			 * The timeline we were sending has become historic. Read the
+			 * timeline history file of the new timeline to see where exactly
+			 * we forked off from the timeline we were sending.
+			 */
+			List	   *history;
+
+			history = readTimeLineHistory(ThisTimeLineID);
+			sendTimeLineValidUpto = tliSwitchPoint(sendTimeLine, history, &sendTimeLineNextTLI);
+
+			Assert(sendTimeLine < sendTimeLineNextTLI);
+			list_free_deep(history);
+
+			sendTimeLineIsHistoric = true;
+
+			SendRqstPtr = sendTimeLineValidUpto;
+		}
+	}
+	else
+	{
+		/*
+		 * Streaming the current timeline on a primary.
+		 *
+		 * Attempt to send all data that's already been written out and
+		 * fsync'd to disk.  We cannot go further than what's been written out
+		 * given the current implementation of WALRead().  And in any case
+		 * it's unsafe to send WAL that is not securely down to disk on the
+		 * primary: if the primary subsequently crashes and restarts, standbys
+		 * must not have applied any WAL that got lost on the primary.
+		 */
+		SendRqstPtr = GetFlushRecPtr();
+	}
+
+	/*
+	 * Record the current system time as an approximation of the time at which
+	 * this WAL location was written for the purposes of lag tracking.
+	 *
+	 * In theory we could make XLogFlush() record a time in shmem whenever WAL
+	 * is flushed and we could get that time as well as the LSN when we call
+	 * GetFlushRecPtr() above (and likewise for the cascading standby
+	 * equivalent), but rather than putting any new code into the hot WAL path
+	 * it seems good enough to capture the time here.  We should reach this
+	 * after XLogFlush() runs WalSndWakeupProcessRequests(), and although that
+	 * may take some time, we read the WAL flush pointer and take the time
+	 * very close to together here so that we'll get a later position if it is
+	 * still moving.
+	 *
+	 * Because LagTrackerWrite ignores samples when the LSN hasn't advanced,
+	 * this gives us a cheap approximation for the WAL flush time for this
+	 * LSN.
+	 *
+	 * Note that the LSN is not necessarily the LSN for the data contained in
+	 * the present message; it's the end of the WAL, which might be further
+	 * ahead.  All the lag tracking machinery cares about is finding out when
+	 * that arbitrary LSN is eventually reported as written, flushed and
+	 * applied, so that it can measure the elapsed time.
+	 */
+	LagTrackerWrite(SendRqstPtr, GetCurrentTimestamp());
+
+	/*
+	 * If this is a historic timeline and we've reached the point where we
+	 * forked to the next timeline, stop streaming.
+	 *
+	 * Note: We might already have sent WAL > sendTimeLineValidUpto. The
+	 * startup process will normally replay all WAL that has been received
+	 * from the primary, before promoting, but if the WAL streaming is
+	 * terminated at a WAL page boundary, the valid portion of the timeline
+	 * might end in the middle of a WAL record. We might've already sent the
+	 * first half of that partial WAL record to the cascading standby, so that
+	 * sentPtr > sendTimeLineValidUpto. That's OK; the cascading standby can't
+	 * replay the partial WAL record either, so it can still follow our
+	 * timeline switch.
+	 */
+	if (sendTimeLineIsHistoric && sendTimeLineValidUpto <= sentPtr)
+	{
+		/* close the current file. */
+		if (xlogreader->seg.ws_file >= 0)
+			wal_segment_close(xlogreader);
+
+		/* Send CopyDone */
+		pq_putmessage_noblock('c', NULL, 0);
+		streamingDoneSending = true;
+
+		WalSndCaughtUp = true;
+
+		elog(DEBUG1, "walsender reached end of timeline at %X/%X (sent up to %X/%X)",
+			 LSN_FORMAT_ARGS(sendTimeLineValidUpto),
+			 LSN_FORMAT_ARGS(sentPtr));
+		return;
+	}
+
+	/* Do we have any work to do? */
+	Assert(sentPtr <= SendRqstPtr);
+	if (SendRqstPtr <= sentPtr)
+	{
+		WalSndCaughtUp = true;
+		return;
+	}
+
+	/*
+	 * Figure out how much to send in one message. If there's no more than
+	 * MAX_SEND_SIZE bytes to send, send everything. Otherwise send
+	 * MAX_SEND_SIZE bytes, but round back to logfile or page boundary.
+	 *
+	 * The rounding is not only for performance reasons. Walreceiver relies on
+	 * the fact that we never split a WAL record across two messages. Since a
+	 * long WAL record is split at page boundary into continuation records,
+	 * page boundary is always a safe cut-off point. We also assume that
+	 * SendRqstPtr never points to the middle of a WAL record.
+	 */
+	startptr = sentPtr;
+	endptr = startptr;
+	endptr += MAX_SEND_SIZE;
+
+	/* if we went beyond SendRqstPtr, back off */
+	if (SendRqstPtr <= endptr)
+	{
+		endptr = SendRqstPtr;
+		if (sendTimeLineIsHistoric)
+			WalSndCaughtUp = false;
+		else
+			WalSndCaughtUp = true;
+	}
+	else
+	{
+		/* round down to page boundary. */
+		endptr -= (endptr % XLOG_BLCKSZ);
+		WalSndCaughtUp = false;
+	}
+
+	nbytes = endptr - startptr;
+	Assert(nbytes <= MAX_SEND_SIZE);
+
+	/*
+	 * OK to read and send the slice.
+	 */
+	resetStringInfo(&output_message);
+	pq_sendbyte(&output_message, 'w');
+
+	pq_sendint64(&output_message, startptr);	/* dataStart */
+	pq_sendint64(&output_message, SendRqstPtr); /* walEnd */
+	pq_sendint64(&output_message, 0);	/* sendtime, filled in last */
+
+	/*
+	 * Read the log directly into the output buffer to avoid extra memcpy
+	 * calls.
+	 */
+	enlargeStringInfo(&output_message, nbytes);
+
+retry:
+	if (!WALRead(xlogreader,
+				 &output_message.data[output_message.len],
+				 startptr,
+				 nbytes,
+				 xlogreader->seg.ws_tli,	/* Pass the current TLI because
+											 * only WalSndSegmentOpen controls
+											 * whether new TLI is needed. */
+				 &errinfo))
+		WALReadRaiseError(&errinfo);
+
+	/* See logical_read_xlog_page(). */
+	XLByteToSeg(startptr, segno, xlogreader->segcxt.ws_segsize);
+	CheckXLogRemoved(segno, xlogreader->seg.ws_tli);
+
+	/*
+	 * During recovery, the currently-open WAL file might be replaced with the
+	 * file of the same name retrieved from archive. So we always need to
+	 * check what we read was valid after reading into the buffer. If it's
+	 * invalid, we try to open and read the file again.
+	 */
+	if (am_cascading_walsender)
+	{
+		WalSnd	   *walsnd = MyWalSnd;
+		bool		reload;
+
+		SpinLockAcquire(&walsnd->mutex);
+		reload = walsnd->needreload;
+		walsnd->needreload = false;
+		SpinLockRelease(&walsnd->mutex);
+
+		if (reload && xlogreader->seg.ws_file >= 0)
+		{
+			wal_segment_close(xlogreader);
+
+			goto retry;
+		}
+	}
+
+	output_message.len += nbytes;
+	output_message.data[output_message.len] = '\0';
+
+	/*
+	 * Fill the send timestamp last, so that it is taken as late as possible.
+	 */
+	resetStringInfo(&tmpbuf);
+	pq_sendint64(&tmpbuf, GetCurrentTimestamp());
+	memcpy(&output_message.data[1 + sizeof(int64) + sizeof(int64)],
+		   tmpbuf.data, sizeof(int64));
+
+	pq_putmessage_noblock('d', output_message.data, output_message.len);
+
+	sentPtr = endptr;
+
+	/* Update shared memory status */
+	{
+		WalSnd	   *walsnd = MyWalSnd;
+
+		SpinLockAcquire(&walsnd->mutex);
+		walsnd->sentPtr = sentPtr;
+		SpinLockRelease(&walsnd->mutex);
+	}
+
+	/* Report progress of XLOG streaming in PS display */
+	if (update_process_title)
+	{
+		char		activitymsg[50];
+
+		snprintf(activitymsg, sizeof(activitymsg), "streaming %X/%X",
+				 LSN_FORMAT_ARGS(sentPtr));
+		set_ps_display(activitymsg);
+	}
+}
+
+/*
+ * Stream out logically decoded data.
+ */
+static void
+XLogSendLogical(void)
+{
+	XLogRecord *record;
+	char	   *errm;
+
+	/*
+	 * We'll use the current flush point to determine whether we've caught up.
+	 * This variable is static in order to cache it across calls.  Caching is
+	 * helpful because GetFlushRecPtr() needs to acquire a heavily-contended
+	 * spinlock.
+	 */
+	static XLogRecPtr flushPtr = InvalidXLogRecPtr;
+
+	/*
+	 * Don't know whether we've caught up yet. We'll set WalSndCaughtUp to
+	 * true in WalSndWaitForWal, if we're actually waiting. We also set to
+	 * true if XLogReadRecord() had to stop reading but WalSndWaitForWal
+	 * didn't wait - i.e. when we're shutting down.
+	 */
+	WalSndCaughtUp = false;
+
+	record = XLogReadRecord(logical_decoding_ctx->reader, &errm);
+
+	/* xlog record was invalid */
+	if (errm != NULL)
+		elog(ERROR, "%s", errm);
+
+	if (record != NULL)
+	{
+		/*
+		 * Note the lack of any call to LagTrackerWrite() which is handled by
+		 * WalSndUpdateProgress which is called by output plugin through
+		 * logical decoding write api.
+		 */
+		LogicalDecodingProcessRecord(logical_decoding_ctx, logical_decoding_ctx->reader);
+
+		sentPtr = logical_decoding_ctx->reader->EndRecPtr;
+	}
+
+	/*
+	 * If first time through in this session, initialize flushPtr.  Otherwise,
+	 * we only need to update flushPtr if EndRecPtr is past it.
+	 */
+	if (flushPtr == InvalidXLogRecPtr)
+		flushPtr = GetFlushRecPtr();
+	else if (logical_decoding_ctx->reader->EndRecPtr >= flushPtr)
+		flushPtr = GetFlushRecPtr();
+
+	/* If EndRecPtr is still past our flushPtr, it means we caught up. */
+	if (logical_decoding_ctx->reader->EndRecPtr >= flushPtr)
+		WalSndCaughtUp = true;
+
+	/*
+	 * If we're caught up and have been requested to stop, have WalSndLoop()
+	 * terminate the connection in an orderly manner, after writing out all
+	 * the pending data.
+	 */
+	if (WalSndCaughtUp && got_STOPPING)
+		got_SIGUSR2 = true;
+
+	/* Update shared memory status */
+	{
+		WalSnd	   *walsnd = MyWalSnd;
+
+		SpinLockAcquire(&walsnd->mutex);
+		walsnd->sentPtr = sentPtr;
+		SpinLockRelease(&walsnd->mutex);
+	}
+}
+
+/*
+ * Shutdown if the sender is caught up.
+ *
+ * NB: This should only be called when the shutdown signal has been received
+ * from postmaster.
+ *
+ * Note that if we determine that there's still more data to send, this
+ * function will return control to the caller.
+ */
+static void
+WalSndDone(WalSndSendDataCallback send_data)
+{
+	XLogRecPtr	replicatedPtr;
+
+	/* ... let's just be real sure we're caught up ... */
+	send_data();
+
+	/*
+	 * To figure out whether all WAL has successfully been replicated, check
+	 * flush location if valid, write otherwise. Tools like pg_receivewal will
+	 * usually (unless in synchronous mode) return an invalid flush location.
+	 */
+	replicatedPtr = XLogRecPtrIsInvalid(MyWalSnd->flush) ?
+		MyWalSnd->write : MyWalSnd->flush;
+
+	if (WalSndCaughtUp && sentPtr == replicatedPtr &&
+		!pq_is_send_pending())
+	{
+		QueryCompletion qc;
+
+		/* Inform the standby that XLOG streaming is done */
+		SetQueryCompletion(&qc, CMDTAG_COPY, 0);
+		EndCommand(&qc, DestRemote, false);
+		pq_flush();
+
+		proc_exit(0);
+	}
+	if (!waiting_for_ping_response)
+		WalSndKeepalive(true);
+}
+
+/*
+ * Returns the latest point in WAL that has been safely flushed to disk, and
+ * can be sent to the standby. This should only be called when in recovery,
+ * ie. we're streaming to a cascaded standby.
+ *
+ * As a side-effect, ThisTimeLineID is updated to the TLI of the last
+ * replayed WAL record.
+ */
+static XLogRecPtr
+GetStandbyFlushRecPtr(void)
+{
+	XLogRecPtr	replayPtr;
+	TimeLineID	replayTLI;
+	XLogRecPtr	receivePtr;
+	TimeLineID	receiveTLI;
+	XLogRecPtr	result;
+
+	/*
+	 * We can safely send what's already been replayed. Also, if walreceiver
+	 * is streaming WAL from the same timeline, we can send anything that it
+	 * has streamed, but hasn't been replayed yet.
+	 */
+
+	receivePtr = GetWalRcvFlushRecPtr(NULL, &receiveTLI);
+	replayPtr = GetXLogReplayRecPtr(&replayTLI);
+
+	ThisTimeLineID = replayTLI;
+
+	result = replayPtr;
+	if (receiveTLI == ThisTimeLineID && receivePtr > replayPtr)
+		result = receivePtr;
+
+	return result;
+}
+
+/*
+ * Request walsenders to reload the currently-open WAL file
+ */
+void
+WalSndRqstFileReload(void)
+{
+	int			i;
+
+	for (i = 0; i < max_wal_senders; i++)
+	{
+		WalSnd	   *walsnd = &WalSndCtl->walsnds[i];
+
+		SpinLockAcquire(&walsnd->mutex);
+		if (walsnd->pid == 0)
+		{
+			SpinLockRelease(&walsnd->mutex);
+			continue;
+		}
+		walsnd->needreload = true;
+		SpinLockRelease(&walsnd->mutex);
+	}
+}
+
+/*
+ * Handle PROCSIG_WALSND_INIT_STOPPING signal.
+ */
+void
+HandleWalSndInitStopping(void)
+{
+	Assert(am_walsender);
+
+	/*
+	 * If replication has not yet started, die like with SIGTERM. If
+	 * replication is active, only set a flag and wake up the main loop. It
+	 * will send any outstanding WAL, wait for it to be replicated to the
+	 * standby, and then exit gracefully.
+	 */
+	if (!replication_active)
+		kill(MyProcPid, SIGTERM);
+	else
+		got_STOPPING = true;
+}
+
+/*
+ * SIGUSR2: set flag to do a last cycle and shut down afterwards. The WAL
+ * sender should already have been switched to WALSNDSTATE_STOPPING at
+ * this point.
+ */
+static void
+WalSndLastCycleHandler(SIGNAL_ARGS)
+{
+	int			save_errno = errno;
+
+	got_SIGUSR2 = true;
+	SetLatch(MyLatch);
+
+	errno = save_errno;
+}
+
+/* Set up signal handlers */
+void
+WalSndSignals(void)
+{
+	/* Set up signal handlers */
+	pqsignal(SIGHUP, SignalHandlerForConfigReload);
+	pqsignal(SIGINT, StatementCancelHandler);	/* query cancel */
+	pqsignal(SIGTERM, die);		/* request shutdown */
+	/* SIGQUIT handler was already set up by InitPostmasterChild */
+	InitializeTimeouts();		/* establishes SIGALRM handler */
+	pqsignal(SIGPIPE, SIG_IGN);
+	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
+	pqsignal(SIGUSR2, WalSndLastCycleHandler);	/* request a last cycle and
+												 * shutdown */
+
+	/* Reset some signals that are accepted by postmaster but not here */
+	pqsignal(SIGCHLD, SIG_DFL);
+}
+
+/* Report shared-memory space needed by WalSndShmemInit */
+Size
+WalSndShmemSize(void)
+{
+	Size		size = 0;
+
+	size = offsetof(WalSndCtlData, walsnds);
+	size = add_size(size, mul_size(max_wal_senders, sizeof(WalSnd)));
+
+	return size;
+}
+
+/* Allocate and initialize walsender-related shared memory */
+void
+WalSndShmemInit(void)
+{
+	bool		found;
+	int			i;
+
+	WalSndCtl = (WalSndCtlData *)
+		ShmemInitStruct("Wal Sender Ctl", WalSndShmemSize(), &found);
+
+	if (!found)
+	{
+		/* First time through, so initialize */
+		MemSet(WalSndCtl, 0, WalSndShmemSize());
+
+		for (i = 0; i < NUM_SYNC_REP_WAIT_MODE; i++)
+			SHMQueueInit(&(WalSndCtl->SyncRepQueue[i]));
+
+		for (i = 0; i < max_wal_senders; i++)
+		{
+			WalSnd	   *walsnd = &WalSndCtl->walsnds[i];
+
+			SpinLockInit(&walsnd->mutex);
+		}
+	}
+}
+
+/*
+ * Wake up all walsenders
+ *
+ * This will be called inside critical sections, so throwing an error is not
+ * advisable.
+ */
+void
+WalSndWakeup(void)
+{
+	int			i;
+
+	for (i = 0; i < max_wal_senders; i++)
+	{
+		Latch	   *latch;
+		WalSnd	   *walsnd = &WalSndCtl->walsnds[i];
+
+		/*
+		 * Get latch pointer with spinlock held, for the unlikely case that
+		 * pointer reads aren't atomic (as they're 8 bytes).
+		 */
+		SpinLockAcquire(&walsnd->mutex);
+		latch = walsnd->latch;
+		SpinLockRelease(&walsnd->mutex);
+
+		if (latch != NULL)
+			SetLatch(latch);
+	}
+}
+
+/*
+ * Wait for readiness on the FeBe socket, or a timeout.  The mask should be
+ * composed of optional WL_SOCKET_WRITEABLE and WL_SOCKET_READABLE flags.  Exit
+ * on postmaster death.
+ */
+static void
+WalSndWait(uint32 socket_events, long timeout, uint32 wait_event)
+{
+	WaitEvent	event;
+
+	ModifyWaitEvent(FeBeWaitSet, FeBeWaitSetSocketPos, socket_events, NULL);
+	if (WaitEventSetWait(FeBeWaitSet, timeout, &event, 1, wait_event) == 1 &&
+		(event.events & WL_POSTMASTER_DEATH))
+		proc_exit(1);
+}
+
+/*
+ * Signal all walsenders to move to stopping state.
+ *
+ * This will trigger walsenders to move to a state where no further WAL can be
+ * generated. See this file's header for details.
+ */
+void
+WalSndInitStopping(void)
+{
+	int			i;
+
+	for (i = 0; i < max_wal_senders; i++)
+	{
+		WalSnd	   *walsnd = &WalSndCtl->walsnds[i];
+		pid_t		pid;
+
+		SpinLockAcquire(&walsnd->mutex);
+		pid = walsnd->pid;
+		SpinLockRelease(&walsnd->mutex);
+
+		if (pid == 0)
+			continue;
+
+		SendProcSignal(pid, PROCSIG_WALSND_INIT_STOPPING, InvalidBackendId);
+	}
+}
+
+/*
+ * Wait that all the WAL senders have quit or reached the stopping state. This
+ * is used by the checkpointer to control when the shutdown checkpoint can
+ * safely be performed.
+ */
+void
+WalSndWaitStopping(void)
+{
+	for (;;)
+	{
+		int			i;
+		bool		all_stopped = true;
+
+		for (i = 0; i < max_wal_senders; i++)
+		{
+			WalSnd	   *walsnd = &WalSndCtl->walsnds[i];
+
+			SpinLockAcquire(&walsnd->mutex);
+
+			if (walsnd->pid == 0)
+			{
+				SpinLockRelease(&walsnd->mutex);
+				continue;
+			}
+
+			if (walsnd->state != WALSNDSTATE_STOPPING)
+			{
+				all_stopped = false;
+				SpinLockRelease(&walsnd->mutex);
+				break;
+			}
+			SpinLockRelease(&walsnd->mutex);
+		}
+
+		/* safe to leave if confirmation is done for all WAL senders */
+		if (all_stopped)
+			return;
+
+		pg_usleep(10000L);		/* wait for 10 msec */
+	}
+}
+
+/* Set state for current walsender (only called in walsender) */
+void
+WalSndSetState(WalSndState state)
+{
+	WalSnd	   *walsnd = MyWalSnd;
+
+	Assert(am_walsender);
+
+	if (walsnd->state == state)
+		return;
+
+	SpinLockAcquire(&walsnd->mutex);
+	walsnd->state = state;
+	SpinLockRelease(&walsnd->mutex);
+}
+
+/*
+ * Return a string constant representing the state. This is used
+ * in system views, and should *not* be translated.
+ */
+static const char *
+WalSndGetStateString(WalSndState state)
+{
+	switch (state)
+	{
+		case WALSNDSTATE_STARTUP:
+			return "startup";
+		case WALSNDSTATE_BACKUP:
+			return "backup";
+		case WALSNDSTATE_CATCHUP:
+			return "catchup";
+		case WALSNDSTATE_STREAMING:
+			return "streaming";
+		case WALSNDSTATE_STOPPING:
+			return "stopping";
+	}
+	return "UNKNOWN";
+}
+
+static Interval *
+offset_to_interval(TimeOffset offset)
+{
+	Interval   *result = palloc(sizeof(Interval));
+
+	result->month = 0;
+	result->day = 0;
+	result->time = offset;
+
+	return result;
+}
+
+/*
+ * Returns activity of walsenders, including pids and xlog locations sent to
+ * standby servers.
+ */
+Datum
+pg_stat_get_wal_senders(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_WAL_SENDERS_COLS	12
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+	TupleDesc	tupdesc;
+	Tuplestorestate *tupstore;
+	MemoryContext per_query_ctx;
+	MemoryContext oldcontext;
+	SyncRepStandbyData *sync_standbys;
+	int			num_standbys;
+	int			i;
+
+	/* check to see if caller supports us returning a tuplestore */
+	if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("set-valued function called in context that cannot accept a set")));
+	if (!(rsinfo->allowedModes & SFRM_Materialize))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("materialize mode required, but it is not allowed in this context")));
+
+	/* Build a tuple descriptor for our result type */
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+		elog(ERROR, "return type must be a row type");
+
+	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
+	oldcontext = MemoryContextSwitchTo(per_query_ctx);
+
+	tupstore = tuplestore_begin_heap(true, false, work_mem);
+	rsinfo->returnMode = SFRM_Materialize;
+	rsinfo->setResult = tupstore;
+	rsinfo->setDesc = tupdesc;
+
+	MemoryContextSwitchTo(oldcontext);
+
+	/*
+	 * Get the currently active synchronous standbys.  This could be out of
+	 * date before we're done, but we'll use the data anyway.
+	 */
+	num_standbys = SyncRepGetCandidateStandbys(&sync_standbys);
+
+	for (i = 0; i < max_wal_senders; i++)
+	{
+		WalSnd	   *walsnd = &WalSndCtl->walsnds[i];
+		XLogRecPtr	sentPtr;
+		XLogRecPtr	write;
+		XLogRecPtr	flush;
+		XLogRecPtr	apply;
+		TimeOffset	writeLag;
+		TimeOffset	flushLag;
+		TimeOffset	applyLag;
+		int			priority;
+		int			pid;
+		WalSndState state;
+		TimestampTz replyTime;
+		bool		is_sync_standby;
+		Datum		values[PG_STAT_GET_WAL_SENDERS_COLS];
+		bool		nulls[PG_STAT_GET_WAL_SENDERS_COLS];
+		int			j;
+
+		/* Collect data from shared memory */
+		SpinLockAcquire(&walsnd->mutex);
+		if (walsnd->pid == 0)
+		{
+			SpinLockRelease(&walsnd->mutex);
+			continue;
+		}
+		pid = walsnd->pid;
+		sentPtr = walsnd->sentPtr;
+		state = walsnd->state;
+		write = walsnd->write;
+		flush = walsnd->flush;
+		apply = walsnd->apply;
+		writeLag = walsnd->writeLag;
+		flushLag = walsnd->flushLag;
+		applyLag = walsnd->applyLag;
+		priority = walsnd->sync_standby_priority;
+		replyTime = walsnd->replyTime;
+		SpinLockRelease(&walsnd->mutex);
+
+		/*
+		 * Detect whether walsender is/was considered synchronous.  We can
+		 * provide some protection against stale data by checking the PID
+		 * along with walsnd_index.
+		 */
+		is_sync_standby = false;
+		for (j = 0; j < num_standbys; j++)
+		{
+			if (sync_standbys[j].walsnd_index == i &&
+				sync_standbys[j].pid == pid)
+			{
+				is_sync_standby = true;
+				break;
+			}
+		}
+
+		memset(nulls, 0, sizeof(nulls));
+		values[0] = Int32GetDatum(pid);
+
+		if (!is_member_of_role(GetUserId(), ROLE_PG_READ_ALL_STATS))
+		{
+			/*
+			 * Only superusers and members of pg_read_all_stats can see
+			 * details. Other users only get the pid value to know it's a
+			 * walsender, but no details.
+			 */
+			MemSet(&nulls[1], true, PG_STAT_GET_WAL_SENDERS_COLS - 1);
+		}
+		else
+		{
+			values[1] = CStringGetTextDatum(WalSndGetStateString(state));
+
+			if (XLogRecPtrIsInvalid(sentPtr))
+				nulls[2] = true;
+			values[2] = LSNGetDatum(sentPtr);
+
+			if (XLogRecPtrIsInvalid(write))
+				nulls[3] = true;
+			values[3] = LSNGetDatum(write);
+
+			if (XLogRecPtrIsInvalid(flush))
+				nulls[4] = true;
+			values[4] = LSNGetDatum(flush);
+
+			if (XLogRecPtrIsInvalid(apply))
+				nulls[5] = true;
+			values[5] = LSNGetDatum(apply);
+
+			/*
+			 * Treat a standby such as a pg_basebackup background process
+			 * which always returns an invalid flush location, as an
+			 * asynchronous standby.
+			 */
+			priority = XLogRecPtrIsInvalid(flush) ? 0 : priority;
+
+			if (writeLag < 0)
+				nulls[6] = true;
+			else
+				values[6] = IntervalPGetDatum(offset_to_interval(writeLag));
+
+			if (flushLag < 0)
+				nulls[7] = true;
+			else
+				values[7] = IntervalPGetDatum(offset_to_interval(flushLag));
+
+			if (applyLag < 0)
+				nulls[8] = true;
+			else
+				values[8] = IntervalPGetDatum(offset_to_interval(applyLag));
+
+			values[9] = Int32GetDatum(priority);
+
+			/*
+			 * More easily understood version of standby state. This is purely
+			 * informational.
+			 *
+			 * In quorum-based sync replication, the role of each standby
+			 * listed in synchronous_standby_names can be changing very
+			 * frequently. Any standbys considered as "sync" at one moment can
+			 * be switched to "potential" ones at the next moment. So, it's
+			 * basically useless to report "sync" or "potential" as their sync
+			 * states. We report just "quorum" for them.
+			 */
+			if (priority == 0)
+				values[10] = CStringGetTextDatum("async");
+			else if (is_sync_standby)
+				values[10] = SyncRepConfig->syncrep_method == SYNC_REP_PRIORITY ?
+					CStringGetTextDatum("sync") : CStringGetTextDatum("quorum");
+			else
+				values[10] = CStringGetTextDatum("potential");
+
+			if (replyTime == 0)
+				nulls[11] = true;
+			else
+				values[11] = TimestampTzGetDatum(replyTime);
+		}
+
+		tuplestore_putvalues(tupstore, tupdesc, values, nulls);
+	}
+
+	/* clean up and return the tuplestore */
+	tuplestore_donestoring(tupstore);
+
+	return (Datum) 0;
+}
+
+/*
+ * Send a keepalive message to standby.
+ *
+ * If requestReply is set, the message requests the other party to send
+ * a message back to us, for heartbeat purposes.  We also set a flag to
+ * let nearby code that we're waiting for that response, to avoid
+ * repeated requests.
+ */
+static void
+WalSndKeepalive(bool requestReply)
+{
+	elog(DEBUG2, "sending replication keepalive");
+
+	/* construct the message... */
+	resetStringInfo(&output_message);
+	pq_sendbyte(&output_message, 'k');
+	pq_sendint64(&output_message, sentPtr);
+	pq_sendint64(&output_message, GetCurrentTimestamp());
+	pq_sendbyte(&output_message, requestReply ? 1 : 0);
+
+	/* ... and send it wrapped in CopyData */
+	pq_putmessage_noblock('d', output_message.data, output_message.len);
+
+	/* Set local flag */
+	if (requestReply)
+		waiting_for_ping_response = true;
+}
+
+/*
+ * Send keepalive message if too much time has elapsed.
+ */
+static void
+WalSndKeepaliveIfNecessary(void)
+{
+	TimestampTz ping_time;
+
+	/*
+	 * Don't send keepalive messages if timeouts are globally disabled or
+	 * we're doing something not partaking in timeouts.
+	 */
+	if (wal_sender_timeout <= 0 || last_reply_timestamp <= 0)
+		return;
+
+	if (waiting_for_ping_response)
+		return;
+
+	/*
+	 * If half of wal_sender_timeout has lapsed without receiving any reply
+	 * from the standby, send a keep-alive message to the standby requesting
+	 * an immediate reply.
+	 */
+	ping_time = TimestampTzPlusMilliseconds(last_reply_timestamp,
+											wal_sender_timeout / 2);
+	if (last_processing >= ping_time)
+	{
+		WalSndKeepalive(true);
+
+		/* Try to flush pending output to the client */
+		if (pq_flush_if_writable() != 0)
+			WalSndShutdown();
+	}
+}
+
+/*
+ * Record the end of the WAL and the time it was flushed locally, so that
+ * LagTrackerRead can compute the elapsed time (lag) when this WAL location is
+ * eventually reported to have been written, flushed and applied by the
+ * standby in a reply message.
+ */
+static void
+LagTrackerWrite(XLogRecPtr lsn, TimestampTz local_flush_time)
+{
+	bool		buffer_full;
+	int			new_write_head;
+	int			i;
+
+	if (!am_walsender)
+		return;
+
+	/*
+	 * If the lsn hasn't advanced since last time, then do nothing.  This way
+	 * we only record a new sample when new WAL has been written.
+	 */
+	if (lag_tracker->last_lsn == lsn)
+		return;
+	lag_tracker->last_lsn = lsn;
+
+	/*
+	 * If advancing the write head of the circular buffer would crash into any
+	 * of the read heads, then the buffer is full.  In other words, the
+	 * slowest reader (presumably apply) is the one that controls the release
+	 * of space.
+	 */
+	new_write_head = (lag_tracker->write_head + 1) % LAG_TRACKER_BUFFER_SIZE;
+	buffer_full = false;
+	for (i = 0; i < NUM_SYNC_REP_WAIT_MODE; ++i)
+	{
+		if (new_write_head == lag_tracker->read_heads[i])
+			buffer_full = true;
+	}
+
+	/*
+	 * If the buffer is full, for now we just rewind by one slot and overwrite
+	 * the last sample, as a simple (if somewhat uneven) way to lower the
+	 * sampling rate.  There may be better adaptive compaction algorithms.
+	 */
+	if (buffer_full)
+	{
+		new_write_head = lag_tracker->write_head;
+		if (lag_tracker->write_head > 0)
+			lag_tracker->write_head--;
+		else
+			lag_tracker->write_head = LAG_TRACKER_BUFFER_SIZE - 1;
+	}
+
+	/* Store a sample at the current write head position. */
+	lag_tracker->buffer[lag_tracker->write_head].lsn = lsn;
+	lag_tracker->buffer[lag_tracker->write_head].time = local_flush_time;
+	lag_tracker->write_head = new_write_head;
+}
+
+/*
+ * Find out how much time has elapsed between the moment WAL location 'lsn'
+ * (or the highest known earlier LSN) was flushed locally and the time 'now'.
+ * We have a separate read head for each of the reported LSN locations we
+ * receive in replies from standby; 'head' controls which read head is
+ * used.  Whenever a read head crosses an LSN which was written into the
+ * lag buffer with LagTrackerWrite, we can use the associated timestamp to
+ * find out the time this LSN (or an earlier one) was flushed locally, and
+ * therefore compute the lag.
+ *
+ * Return -1 if no new sample data is available, and otherwise the elapsed
+ * time in microseconds.
+ */
+static TimeOffset
+LagTrackerRead(int head, XLogRecPtr lsn, TimestampTz now)
+{
+	TimestampTz time = 0;
+
+	/* Read all unread samples up to this LSN or end of buffer. */
+	while (lag_tracker->read_heads[head] != lag_tracker->write_head &&
+		   lag_tracker->buffer[lag_tracker->read_heads[head]].lsn <= lsn)
+	{
+		time = lag_tracker->buffer[lag_tracker->read_heads[head]].time;
+		lag_tracker->last_read[head] =
+			lag_tracker->buffer[lag_tracker->read_heads[head]];
+		lag_tracker->read_heads[head] =
+			(lag_tracker->read_heads[head] + 1) % LAG_TRACKER_BUFFER_SIZE;
+	}
+
+	/*
+	 * If the lag tracker is empty, that means the standby has processed
+	 * everything we've ever sent so we should now clear 'last_read'.  If we
+	 * didn't do that, we'd risk using a stale and irrelevant sample for
+	 * interpolation at the beginning of the next burst of WAL after a period
+	 * of idleness.
+	 */
+	if (lag_tracker->read_heads[head] == lag_tracker->write_head)
+		lag_tracker->last_read[head].time = 0;
+
+	if (time > now)
+	{
+		/* If the clock somehow went backwards, treat as not found. */
+		return -1;
+	}
+	else if (time == 0)
+	{
+		/*
+		 * We didn't cross a time.  If there is a future sample that we
+		 * haven't reached yet, and we've already reached at least one sample,
+		 * let's interpolate the local flushed time.  This is mainly useful
+		 * for reporting a completely stuck apply position as having
+		 * increasing lag, since otherwise we'd have to wait for it to
+		 * eventually start moving again and cross one of our samples before
+		 * we can show the lag increasing.
+		 */
+		if (lag_tracker->read_heads[head] == lag_tracker->write_head)
+		{
+			/* There are no future samples, so we can't interpolate. */
+			return -1;
+		}
+		else if (lag_tracker->last_read[head].time != 0)
+		{
+			/* We can interpolate between last_read and the next sample. */
+			double		fraction;
+			WalTimeSample prev = lag_tracker->last_read[head];
+			WalTimeSample next = lag_tracker->buffer[lag_tracker->read_heads[head]];
+
+			if (lsn < prev.lsn)
+			{
+				/*
+				 * Reported LSNs shouldn't normally go backwards, but it's
+				 * possible when there is a timeline change.  Treat as not
+				 * found.
+				 */
+				return -1;
+			}
+
+			Assert(prev.lsn < next.lsn);
+
+			if (prev.time > next.time)
+			{
+				/* If the clock somehow went backwards, treat as not found. */
+				return -1;
+			}
+
+			/* See how far we are between the previous and next samples. */
+			fraction =
+				(double) (lsn - prev.lsn) / (double) (next.lsn - prev.lsn);
+
+			/* Scale the local flush time proportionally. */
+			time = (TimestampTz)
+				((double) prev.time + (next.time - prev.time) * fraction);
+		}
+		else
+		{
+			/*
+			 * We have only a future sample, implying that we were entirely
+			 * caught up but and now there is a new burst of WAL and the
+			 * standby hasn't processed the first sample yet.  Until the
+			 * standby reaches the future sample the best we can do is report
+			 * the hypothetical lag if that sample were to be replayed now.
+			 */
+			time = lag_tracker->buffer[lag_tracker->read_heads[head]].time;
+		}
+	}
+
+	/* Return the elapsed time since local flush time in microseconds. */
+	Assert(time != 0);
+	return now - time;
+}