Adding upstream version 15.5.upstream/15.5

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

1 files changed, 1874 insertions, 0 deletions

diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
new file mode 100644
index 0000000..466f30c
--- /dev/null
+++ b/src/backend/replication/logical/logical.c
@@ -0,0 +1,1874 @@
+/*-------------------------------------------------------------------------
+ * logical.c
+ *	   PostgreSQL logical decoding coordination
+ *
+ * Copyright (c) 2012-2022, 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"),
+				 errdetail("Failed while allocating a WAL reading processor.")));
+
+	ctx->reorder = ReorderBufferAllocate();
+	ctx->snapshot_builder =
+		AllocateSnapshotBuilder(ctx->reorder, xmin_horizon, start_lsn,
+								need_full_snapshot, slot->data.two_phase_at);
+
+	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 when the two_phase is
+	 * enabled at the time of slot creation, or when the two_phase option is
+	 * given at the streaming start, provided the plugin supports all the
+	 * callbacks for two-phase.
+	 */
+	ctx->twophase &= slot->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.
+		 *
+		 * Starting at a different LSN than requested might not catch certain
+		 * kinds of client errors; so the client may wish to check that
+		 * confirmed_flush_lsn matches its expectations.
+		 */
+		elog(LOG, "%X/%X has been already streamed, forwarding to %X/%X",
+			 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 when the two_phase is
+	 * enabled at the time of slot creation, or when the two_phase option is
+	 * given at the streaming start, provided the plugin supports all the
+	 * callbacks for two-phase.
+	 */
+	ctx->twophase &= (slot->data.two_phase || ctx->twophase_opt_given);
+
+	/* Mark slot to allow two_phase decoding if not already marked */
+	if (ctx->twophase && !slot->data.two_phase)
+	{
+		SpinLockAcquire(&slot->mutex);
+		slot->data.two_phase = true;
+		slot->data.two_phase_at = start_lsn;
+		SpinLockRelease(&slot->mutex);
+		ReplicationSlotMarkDirty();
+		ReplicationSlotSave();
+		SnapBuildSetTwoPhaseAt(ctx->snapshot_builder, start_lsn);
+	}
+
+	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, "could not find logical decoding starting point: %s", err);
+		if (!record)
+			elog(ERROR, "could not find logical decoding starting point");
+
+		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;
+	if (slot->data.two_phase)
+		slot->data.two_phase_at = 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,
+						   bool skipped_xact)
+{
+	if (!ctx->update_progress)
+		return;
+
+	ctx->update_progress(ctx, ctx->write_location, ctx->write_xid,
+						 skipped_xact);
+}
+
+/*
+ * 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 up-to-date
+	 * 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 up-to-date
+	 * 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
+	 * up-to-date 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
+	 * up-to-date 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 up-to-date
+	 * 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 up-to-date
+	 * 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;
+	bool		got_new_xmin = false;
+
+	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;
+
+		/*
+		 * Log new xmin at an appropriate log level after releasing the
+		 * spinlock.
+		 */
+		got_new_xmin = true;
+	}
+	SpinLockRelease(&slot->mutex);
+
+	if (got_new_xmin)
+		elog(DEBUG1, "got new catalog xmin %u at %X/%X", xmin,
+			 LSN_FORMAT_ARGS(current_lsn));
+
+	/* 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);
+
+	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(ctx->slot, &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;
+}