Adding upstream version 16.2.upstream/16.2

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

1 files changed, 756 insertions, 0 deletions

diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c
new file mode 100644
index 0000000..5044ff0
--- /dev/null
+++ b/src/backend/access/transam/xlogfuncs.c
@@ -0,0 +1,756 @@
+/*-------------------------------------------------------------------------
+ *
+ * xlogfuncs.c
+ *
+ * PostgreSQL write-ahead log manager user interface functions
+ *
+ * This file contains WAL control and information functions.
+ *
+ *
+ * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/backend/access/transam/xlogfuncs.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <unistd.h>
+
+#include "access/htup_details.h"
+#include "access/xlog_internal.h"
+#include "access/xlogbackup.h"
+#include "access/xlogrecovery.h"
+#include "access/xlogutils.h"
+#include "catalog/pg_type.h"
+#include "funcapi.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "replication/walreceiver.h"
+#include "storage/fd.h"
+#include "storage/ipc.h"
+#include "storage/smgr.h"
+#include "storage/standby.h"
+#include "utils/builtins.h"
+#include "utils/guc.h"
+#include "utils/memutils.h"
+#include "utils/numeric.h"
+#include "utils/pg_lsn.h"
+#include "utils/timestamp.h"
+#include "utils/tuplestore.h"
+
+/*
+ * Backup-related variables.
+ */
+static BackupState *backup_state = NULL;
+static StringInfo tablespace_map = NULL;
+
+/* Session-level context for the SQL-callable backup functions */
+static MemoryContext backupcontext = NULL;
+
+/*
+ * pg_backup_start: set up for taking an on-line backup dump
+ *
+ * Essentially what this does is to create the contents required for the
+ * backup_label file and the tablespace map.
+ *
+ * Permission checking for this function is managed through the normal
+ * GRANT system.
+ */
+Datum
+pg_backup_start(PG_FUNCTION_ARGS)
+{
+	text	   *backupid = PG_GETARG_TEXT_PP(0);
+	bool		fast = PG_GETARG_BOOL(1);
+	char	   *backupidstr;
+	SessionBackupState status = get_backup_status();
+	MemoryContext oldcontext;
+
+	backupidstr = text_to_cstring(backupid);
+
+	if (status == SESSION_BACKUP_RUNNING)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("a backup is already in progress in this session")));
+
+	/*
+	 * backup_state and tablespace_map need to be long-lived as they are used
+	 * in pg_backup_stop().  These are allocated in a dedicated memory context
+	 * child of TopMemoryContext, deleted at the end of pg_backup_stop().  If
+	 * an error happens before ending the backup, memory would be leaked in
+	 * this context until pg_backup_start() is called again.
+	 */
+	if (backupcontext == NULL)
+	{
+		backupcontext = AllocSetContextCreate(TopMemoryContext,
+											  "on-line backup context",
+											  ALLOCSET_START_SMALL_SIZES);
+	}
+	else
+	{
+		backup_state = NULL;
+		tablespace_map = NULL;
+		MemoryContextReset(backupcontext);
+	}
+
+	oldcontext = MemoryContextSwitchTo(backupcontext);
+	backup_state = (BackupState *) palloc0(sizeof(BackupState));
+	tablespace_map = makeStringInfo();
+	MemoryContextSwitchTo(oldcontext);
+
+	register_persistent_abort_backup_handler();
+	do_pg_backup_start(backupidstr, fast, NULL, backup_state, tablespace_map);
+
+	PG_RETURN_LSN(backup_state->startpoint);
+}
+
+
+/*
+ * pg_backup_stop: finish taking an on-line backup.
+ *
+ * The first parameter (variable 'waitforarchive'), which is optional,
+ * allows the user to choose if they want to wait for the WAL to be archived
+ * or if we should just return as soon as the WAL record is written.
+ *
+ * This function stops an in-progress backup, creates backup_label contents and
+ * it returns the backup stop LSN, backup_label and tablespace_map contents.
+ *
+ * The backup_label contains the user-supplied label string (typically this
+ * would be used to tell where the backup dump will be stored), the starting
+ * time, starting WAL location for the dump and so on.  It is the caller's
+ * responsibility to write the backup_label and tablespace_map files in the
+ * data folder that will be restored from this backup.
+ *
+ * Permission checking for this function is managed through the normal
+ * GRANT system.
+ */
+Datum
+pg_backup_stop(PG_FUNCTION_ARGS)
+{
+#define PG_BACKUP_STOP_V2_COLS 3
+	TupleDesc	tupdesc;
+	Datum		values[PG_BACKUP_STOP_V2_COLS] = {0};
+	bool		nulls[PG_BACKUP_STOP_V2_COLS] = {0};
+	bool		waitforarchive = PG_GETARG_BOOL(0);
+	char	   *backup_label;
+	SessionBackupState status = get_backup_status();
+
+	/* Initialize attributes information in the tuple descriptor */
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+		elog(ERROR, "return type must be a row type");
+
+	if (status != SESSION_BACKUP_RUNNING)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("backup is not in progress"),
+				 errhint("Did you call pg_backup_start()?")));
+
+	Assert(backup_state != NULL);
+	Assert(tablespace_map != NULL);
+
+	/* Stop the backup */
+	do_pg_backup_stop(backup_state, waitforarchive);
+
+	/* Build the contents of backup_label */
+	backup_label = build_backup_content(backup_state, false);
+
+	values[0] = LSNGetDatum(backup_state->stoppoint);
+	values[1] = CStringGetTextDatum(backup_label);
+	values[2] = CStringGetTextDatum(tablespace_map->data);
+
+	/* Deallocate backup-related variables */
+	pfree(backup_label);
+
+	/* Clean up the session-level state and its memory context */
+	backup_state = NULL;
+	tablespace_map = NULL;
+	MemoryContextDelete(backupcontext);
+	backupcontext = NULL;
+
+	/* Returns the record as Datum */
+	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
+/*
+ * pg_switch_wal: switch to next xlog file
+ *
+ * Permission checking for this function is managed through the normal
+ * GRANT system.
+ */
+Datum
+pg_switch_wal(PG_FUNCTION_ARGS)
+{
+	XLogRecPtr	switchpoint;
+
+	if (RecoveryInProgress())
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("recovery is in progress"),
+				 errhint("WAL control functions cannot be executed during recovery.")));
+
+	switchpoint = RequestXLogSwitch(false);
+
+	/*
+	 * As a convenience, return the WAL location of the switch record
+	 */
+	PG_RETURN_LSN(switchpoint);
+}
+
+/*
+ * pg_log_standby_snapshot: call LogStandbySnapshot()
+ *
+ * Permission checking for this function is managed through the normal
+ * GRANT system.
+ */
+Datum
+pg_log_standby_snapshot(PG_FUNCTION_ARGS)
+{
+	XLogRecPtr	recptr;
+
+	if (RecoveryInProgress())
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("recovery is in progress"),
+				 errhint("%s cannot be executed during recovery.",
+						 "pg_log_standby_snapshot()")));
+
+	if (!XLogStandbyInfoActive())
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("pg_log_standby_snapshot() can only be used if wal_level >= replica")));
+
+	recptr = LogStandbySnapshot();
+
+	/*
+	 * As a convenience, return the WAL location of the last inserted record
+	 */
+	PG_RETURN_LSN(recptr);
+}
+
+/*
+ * pg_create_restore_point: a named point for restore
+ *
+ * Permission checking for this function is managed through the normal
+ * GRANT system.
+ */
+Datum
+pg_create_restore_point(PG_FUNCTION_ARGS)
+{
+	text	   *restore_name = PG_GETARG_TEXT_PP(0);
+	char	   *restore_name_str;
+	XLogRecPtr	restorepoint;
+
+	if (RecoveryInProgress())
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("recovery is in progress"),
+				 errhint("WAL control functions cannot be executed during recovery.")));
+
+	if (!XLogIsNeeded())
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("WAL level not sufficient for creating a restore point"),
+				 errhint("wal_level must be set to \"replica\" or \"logical\" at server start.")));
+
+	restore_name_str = text_to_cstring(restore_name);
+
+	if (strlen(restore_name_str) >= MAXFNAMELEN)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("value too long for restore point (maximum %d characters)", MAXFNAMELEN - 1)));
+
+	restorepoint = XLogRestorePoint(restore_name_str);
+
+	/*
+	 * As a convenience, return the WAL location of the restore point record
+	 */
+	PG_RETURN_LSN(restorepoint);
+}
+
+/*
+ * Report the current WAL write location (same format as pg_backup_start etc)
+ *
+ * This is useful for determining how much of WAL is visible to an external
+ * archiving process.  Note that the data before this point is written out
+ * to the kernel, but is not necessarily synced to disk.
+ */
+Datum
+pg_current_wal_lsn(PG_FUNCTION_ARGS)
+{
+	XLogRecPtr	current_recptr;
+
+	if (RecoveryInProgress())
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("recovery is in progress"),
+				 errhint("WAL control functions cannot be executed during recovery.")));
+
+	current_recptr = GetXLogWriteRecPtr();
+
+	PG_RETURN_LSN(current_recptr);
+}
+
+/*
+ * Report the current WAL insert location (same format as pg_backup_start etc)
+ *
+ * This function is mostly for debugging purposes.
+ */
+Datum
+pg_current_wal_insert_lsn(PG_FUNCTION_ARGS)
+{
+	XLogRecPtr	current_recptr;
+
+	if (RecoveryInProgress())
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("recovery is in progress"),
+				 errhint("WAL control functions cannot be executed during recovery.")));
+
+	current_recptr = GetXLogInsertRecPtr();
+
+	PG_RETURN_LSN(current_recptr);
+}
+
+/*
+ * Report the current WAL flush location (same format as pg_backup_start etc)
+ *
+ * This function is mostly for debugging purposes.
+ */
+Datum
+pg_current_wal_flush_lsn(PG_FUNCTION_ARGS)
+{
+	XLogRecPtr	current_recptr;
+
+	if (RecoveryInProgress())
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("recovery is in progress"),
+				 errhint("WAL control functions cannot be executed during recovery.")));
+
+	current_recptr = GetFlushRecPtr(NULL);
+
+	PG_RETURN_LSN(current_recptr);
+}
+
+/*
+ * Report the last WAL receive location (same format as pg_backup_start etc)
+ *
+ * This is useful for determining how much of WAL is guaranteed to be received
+ * and synced to disk by walreceiver.
+ */
+Datum
+pg_last_wal_receive_lsn(PG_FUNCTION_ARGS)
+{
+	XLogRecPtr	recptr;
+
+	recptr = GetWalRcvFlushRecPtr(NULL, NULL);
+
+	if (recptr == 0)
+		PG_RETURN_NULL();
+
+	PG_RETURN_LSN(recptr);
+}
+
+/*
+ * Report the last WAL replay location (same format as pg_backup_start etc)
+ *
+ * This is useful for determining how much of WAL is visible to read-only
+ * connections during recovery.
+ */
+Datum
+pg_last_wal_replay_lsn(PG_FUNCTION_ARGS)
+{
+	XLogRecPtr	recptr;
+
+	recptr = GetXLogReplayRecPtr(NULL);
+
+	if (recptr == 0)
+		PG_RETURN_NULL();
+
+	PG_RETURN_LSN(recptr);
+}
+
+/*
+ * Compute an xlog file name and decimal byte offset given a WAL location,
+ * such as is returned by pg_backup_stop() or pg_switch_wal().
+ *
+ * Note that a location exactly at a segment boundary is taken to be in
+ * the previous segment.  This is usually the right thing, since the
+ * expected usage is to determine which xlog file(s) are ready to archive.
+ */
+Datum
+pg_walfile_name_offset(PG_FUNCTION_ARGS)
+{
+	XLogSegNo	xlogsegno;
+	uint32		xrecoff;
+	XLogRecPtr	locationpoint = PG_GETARG_LSN(0);
+	char		xlogfilename[MAXFNAMELEN];
+	Datum		values[2];
+	bool		isnull[2];
+	TupleDesc	resultTupleDesc;
+	HeapTuple	resultHeapTuple;
+	Datum		result;
+
+	if (RecoveryInProgress())
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("recovery is in progress"),
+				 errhint("%s cannot be executed during recovery.",
+						 "pg_walfile_name_offset()")));
+
+	/*
+	 * Construct a tuple descriptor for the result row.  This must match this
+	 * function's pg_proc entry!
+	 */
+	resultTupleDesc = CreateTemplateTupleDesc(2);
+	TupleDescInitEntry(resultTupleDesc, (AttrNumber) 1, "file_name",
+					   TEXTOID, -1, 0);
+	TupleDescInitEntry(resultTupleDesc, (AttrNumber) 2, "file_offset",
+					   INT4OID, -1, 0);
+
+	resultTupleDesc = BlessTupleDesc(resultTupleDesc);
+
+	/*
+	 * xlogfilename
+	 */
+	XLByteToPrevSeg(locationpoint, xlogsegno, wal_segment_size);
+	XLogFileName(xlogfilename, GetWALInsertionTimeLine(), xlogsegno,
+				 wal_segment_size);
+
+	values[0] = CStringGetTextDatum(xlogfilename);
+	isnull[0] = false;
+
+	/*
+	 * offset
+	 */
+	xrecoff = XLogSegmentOffset(locationpoint, wal_segment_size);
+
+	values[1] = UInt32GetDatum(xrecoff);
+	isnull[1] = false;
+
+	/*
+	 * Tuple jam: Having first prepared your Datums, then squash together
+	 */
+	resultHeapTuple = heap_form_tuple(resultTupleDesc, values, isnull);
+
+	result = HeapTupleGetDatum(resultHeapTuple);
+
+	PG_RETURN_DATUM(result);
+}
+
+/*
+ * Compute an xlog file name given a WAL location,
+ * such as is returned by pg_backup_stop() or pg_switch_wal().
+ */
+Datum
+pg_walfile_name(PG_FUNCTION_ARGS)
+{
+	XLogSegNo	xlogsegno;
+	XLogRecPtr	locationpoint = PG_GETARG_LSN(0);
+	char		xlogfilename[MAXFNAMELEN];
+
+	if (RecoveryInProgress())
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("recovery is in progress"),
+				 errhint("%s cannot be executed during recovery.",
+						 "pg_walfile_name()")));
+
+	XLByteToPrevSeg(locationpoint, xlogsegno, wal_segment_size);
+	XLogFileName(xlogfilename, GetWALInsertionTimeLine(), xlogsegno,
+				 wal_segment_size);
+
+	PG_RETURN_TEXT_P(cstring_to_text(xlogfilename));
+}
+
+/*
+ * Extract the sequence number and the timeline ID from given a WAL file
+ * name.
+ */
+Datum
+pg_split_walfile_name(PG_FUNCTION_ARGS)
+{
+#define PG_SPLIT_WALFILE_NAME_COLS 2
+	char	   *fname = text_to_cstring(PG_GETARG_TEXT_PP(0));
+	char	   *fname_upper;
+	char	   *p;
+	TimeLineID	tli;
+	XLogSegNo	segno;
+	Datum		values[PG_SPLIT_WALFILE_NAME_COLS] = {0};
+	bool		isnull[PG_SPLIT_WALFILE_NAME_COLS] = {0};
+	TupleDesc	tupdesc;
+	HeapTuple	tuple;
+	char		buf[256];
+	Datum		result;
+
+	fname_upper = pstrdup(fname);
+
+	/* Capitalize WAL file name. */
+	for (p = fname_upper; *p; p++)
+		*p = pg_toupper((unsigned char) *p);
+
+	if (!IsXLogFileName(fname_upper))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid WAL file name \"%s\"", fname)));
+
+	XLogFromFileName(fname_upper, &tli, &segno, wal_segment_size);
+
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+		elog(ERROR, "return type must be a row type");
+
+	/* Convert to numeric. */
+	snprintf(buf, sizeof buf, UINT64_FORMAT, segno);
+	values[0] = DirectFunctionCall3(numeric_in,
+									CStringGetDatum(buf),
+									ObjectIdGetDatum(0),
+									Int32GetDatum(-1));
+
+	values[1] = Int64GetDatum(tli);
+
+	tuple = heap_form_tuple(tupdesc, values, isnull);
+	result = HeapTupleGetDatum(tuple);
+
+	PG_RETURN_DATUM(result);
+
+#undef PG_SPLIT_WALFILE_NAME_COLS
+}
+
+/*
+ * pg_wal_replay_pause - Request to pause recovery
+ *
+ * Permission checking for this function is managed through the normal
+ * GRANT system.
+ */
+Datum
+pg_wal_replay_pause(PG_FUNCTION_ARGS)
+{
+	if (!RecoveryInProgress())
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("recovery is not in progress"),
+				 errhint("Recovery control functions can only be executed during recovery.")));
+
+	if (PromoteIsTriggered())
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("standby promotion is ongoing"),
+				 errhint("%s cannot be executed after promotion is triggered.",
+						 "pg_wal_replay_pause()")));
+
+	SetRecoveryPause(true);
+
+	/* wake up the recovery process so that it can process the pause request */
+	WakeupRecovery();
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * pg_wal_replay_resume - resume recovery now
+ *
+ * Permission checking for this function is managed through the normal
+ * GRANT system.
+ */
+Datum
+pg_wal_replay_resume(PG_FUNCTION_ARGS)
+{
+	if (!RecoveryInProgress())
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("recovery is not in progress"),
+				 errhint("Recovery control functions can only be executed during recovery.")));
+
+	if (PromoteIsTriggered())
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("standby promotion is ongoing"),
+				 errhint("%s cannot be executed after promotion is triggered.",
+						 "pg_wal_replay_resume()")));
+
+	SetRecoveryPause(false);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * pg_is_wal_replay_paused
+ */
+Datum
+pg_is_wal_replay_paused(PG_FUNCTION_ARGS)
+{
+	if (!RecoveryInProgress())
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("recovery is not in progress"),
+				 errhint("Recovery control functions can only be executed during recovery.")));
+
+	PG_RETURN_BOOL(GetRecoveryPauseState() != RECOVERY_NOT_PAUSED);
+}
+
+/*
+ * pg_get_wal_replay_pause_state - Returns the recovery pause state.
+ *
+ * Returned values:
+ *
+ * 'not paused' - if pause is not requested
+ * 'pause requested' - if pause is requested but recovery is not yet paused
+ * 'paused' - if recovery is paused
+ */
+Datum
+pg_get_wal_replay_pause_state(PG_FUNCTION_ARGS)
+{
+	char	   *statestr = NULL;
+
+	if (!RecoveryInProgress())
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("recovery is not in progress"),
+				 errhint("Recovery control functions can only be executed during recovery.")));
+
+	/* get the recovery pause state */
+	switch (GetRecoveryPauseState())
+	{
+		case RECOVERY_NOT_PAUSED:
+			statestr = "not paused";
+			break;
+		case RECOVERY_PAUSE_REQUESTED:
+			statestr = "pause requested";
+			break;
+		case RECOVERY_PAUSED:
+			statestr = "paused";
+			break;
+	}
+
+	Assert(statestr != NULL);
+	PG_RETURN_TEXT_P(cstring_to_text(statestr));
+}
+
+/*
+ * Returns timestamp of latest processed commit/abort record.
+ *
+ * When the server has been started normally without recovery the function
+ * returns NULL.
+ */
+Datum
+pg_last_xact_replay_timestamp(PG_FUNCTION_ARGS)
+{
+	TimestampTz xtime;
+
+	xtime = GetLatestXTime();
+	if (xtime == 0)
+		PG_RETURN_NULL();
+
+	PG_RETURN_TIMESTAMPTZ(xtime);
+}
+
+/*
+ * Returns bool with current recovery mode, a global state.
+ */
+Datum
+pg_is_in_recovery(PG_FUNCTION_ARGS)
+{
+	PG_RETURN_BOOL(RecoveryInProgress());
+}
+
+/*
+ * Compute the difference in bytes between two WAL locations.
+ */
+Datum
+pg_wal_lsn_diff(PG_FUNCTION_ARGS)
+{
+	Datum		result;
+
+	result = DirectFunctionCall2(pg_lsn_mi,
+								 PG_GETARG_DATUM(0),
+								 PG_GETARG_DATUM(1));
+
+	PG_RETURN_DATUM(result);
+}
+
+/*
+ * Promotes a standby server.
+ *
+ * A result of "true" means that promotion has been completed if "wait" is
+ * "true", or initiated if "wait" is false.
+ */
+Datum
+pg_promote(PG_FUNCTION_ARGS)
+{
+	bool		wait = PG_GETARG_BOOL(0);
+	int			wait_seconds = PG_GETARG_INT32(1);
+	FILE	   *promote_file;
+	int			i;
+
+	if (!RecoveryInProgress())
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("recovery is not in progress"),
+				 errhint("Recovery control functions can only be executed during recovery.")));
+
+	if (wait_seconds <= 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("\"wait_seconds\" must not be negative or zero")));
+
+	/* create the promote signal file */
+	promote_file = AllocateFile(PROMOTE_SIGNAL_FILE, "w");
+	if (!promote_file)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not create file \"%s\": %m",
+						PROMOTE_SIGNAL_FILE)));
+
+	if (FreeFile(promote_file))
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not write file \"%s\": %m",
+						PROMOTE_SIGNAL_FILE)));
+
+	/* signal the postmaster */
+	if (kill(PostmasterPid, SIGUSR1) != 0)
+	{
+		ereport(WARNING,
+				(errmsg("failed to send signal to postmaster: %m")));
+		(void) unlink(PROMOTE_SIGNAL_FILE);
+		PG_RETURN_BOOL(false);
+	}
+
+	/* return immediately if waiting was not requested */
+	if (!wait)
+		PG_RETURN_BOOL(true);
+
+	/* wait for the amount of time wanted until promotion */
+#define WAITS_PER_SECOND 10
+	for (i = 0; i < WAITS_PER_SECOND * wait_seconds; i++)
+	{
+		int			rc;
+
+		ResetLatch(MyLatch);
+
+		if (!RecoveryInProgress())
+			PG_RETURN_BOOL(true);
+
+		CHECK_FOR_INTERRUPTS();
+
+		rc = WaitLatch(MyLatch,
+					   WL_LATCH_SET | WL_TIMEOUT | WL_POSTMASTER_DEATH,
+					   1000L / WAITS_PER_SECOND,
+					   WAIT_EVENT_PROMOTE);
+
+		/*
+		 * Emergency bailout if postmaster has died.  This is to avoid the
+		 * necessity for manual cleanup of all postmaster children.
+		 */
+		if (rc & WL_POSTMASTER_DEATH)
+			PG_RETURN_BOOL(false);
+	}
+
+	ereport(WARNING,
+			(errmsg_plural("server did not promote within %d second",
+						   "server did not promote within %d seconds",
+						   wait_seconds,
+						   wait_seconds)));
+	PG_RETURN_BOOL(false);
+}