18 files changed, 218 insertions, 111 deletions

diff --git a/src/backend/access/heap/pruneheap.c b/src/backend/access/heap/pruneheap.c
index 0d6311088ea..ac958d86374 100644
--- a/src/backend/access/heap/pruneheap.c
+++ b/src/backend/access/heap/pruneheap.c
@@ -461,7 +461,7 @@ heap_page_will_freeze(Relation relation, Buffer buffer,
  * 'new_relmin_mxid' arguments are required when freezing.  When
  * HEAP_PAGE_PRUNE_FREEZE option is passed, we also set presult->all_visible
  * and presult->all_frozen after determining whether or not to
- * opporunistically freeze, to indicate if the VM bits can be set.  They are
+ * opportunistically freeze, to indicate if the VM bits can be set.  They are
  * always set to false when the HEAP_PAGE_PRUNE_FREEZE option is not passed,
  * because at the moment only callers that also freeze need that information.
  *
@@ -504,6 +504,9 @@ heap_page_prune_and_freeze(PruneFreezeParams *params,
 	prstate.vistest = params->vistest;
 	prstate.mark_unused_now =
 		(params->options & HEAP_PAGE_PRUNE_MARK_UNUSED_NOW) != 0;
+
+	/* cutoffs must be provided if we will attempt freezing */
+	Assert(!(params->options & HEAP_PAGE_PRUNE_FREEZE) || params->cutoffs);
 	prstate.attempt_freeze = (params->options & HEAP_PAGE_PRUNE_FREEZE) != 0;
 	prstate.cutoffs = params->cutoffs;
 
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 95ad29a64b9..6fffdb9398e 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1076,6 +1076,8 @@ CREATE VIEW pg_stat_replication_slots AS
             s.mem_exceeded_count,
             s.total_txns,
             s.total_bytes,
+            s.slotsync_skip_count,
+            s.slotsync_skip_at,
             s.stats_reset
     FROM pg_replication_slots as r,
         LATERAL pg_stat_get_replication_slot(slot_name) as s
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index d1cbab58799..dd323c9b9fd 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -945,9 +945,7 @@ retry:
 	ExecDropSingleTupleTableSlot(existing_slot);
 
 #ifdef USE_INJECTION_POINTS
-	if (conflict)
-		INJECTION_POINT("check-exclusion-or-unique-constraint-conflict", NULL);
-	else
+	if (!conflict)
 		INJECTION_POINT("check-exclusion-or-unique-constraint-no-conflict", NULL);
 #endif
 
diff --git a/src/backend/nodes/bitmapset.c b/src/backend/nodes/bitmapset.c
index b4ecf0b0390..7b1e9d94103 100644
--- a/src/backend/nodes/bitmapset.c
+++ b/src/backend/nodes/bitmapset.c
@@ -538,7 +538,6 @@ bms_is_member(int x, const Bitmapset *a)
 int
 bms_member_index(Bitmapset *a, int x)
 {
-	int			i;
 	int			bitnum;
 	int			wordnum;
 	int			result = 0;
@@ -554,7 +553,7 @@ bms_member_index(Bitmapset *a, int x)
 	bitnum = BITNUM(x);
 
 	/* count bits in preceding words */
-	for (i = 0; i < wordnum; i++)
+	for (int i = 0; i < wordnum; i++)
 	{
 		bitmapword	w = a->words[i];
 
@@ -1306,7 +1305,6 @@ int
 bms_next_member(const Bitmapset *a, int prevbit)
 {
 	int			nwords;
-	int			wordnum;
 	bitmapword	mask;
 
 	Assert(bms_is_valid_set(a));
@@ -1316,7 +1314,7 @@ bms_next_member(const Bitmapset *a, int prevbit)
 	nwords = a->nwords;
 	prevbit++;
 	mask = (~(bitmapword) 0) << BITNUM(prevbit);
-	for (wordnum = WORDNUM(prevbit); wordnum < nwords; wordnum++)
+	for (int wordnum = WORDNUM(prevbit); wordnum < nwords; wordnum++)
 	{
 		bitmapword	w = a->words[wordnum];
 
@@ -1366,7 +1364,6 @@ bms_next_member(const Bitmapset *a, int prevbit)
 int
 bms_prev_member(const Bitmapset *a, int prevbit)
 {
-	int			wordnum;
 	int			ushiftbits;
 	bitmapword	mask;
 
@@ -1391,7 +1388,7 @@ bms_prev_member(const Bitmapset *a, int prevbit)
 
 	ushiftbits = BITS_PER_BITMAPWORD - (BITNUM(prevbit) + 1);
 	mask = (~(bitmapword) 0) >> ushiftbits;
-	for (wordnum = WORDNUM(prevbit); wordnum >= 0; wordnum--)
+	for (int wordnum = WORDNUM(prevbit); wordnum >= 0; wordnum--)
 	{
 		bitmapword	w = a->words[wordnum];
 
diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index ede838cd40c..d228318dc72 100644
--- a/src/backend/nodes/nodeFuncs.c
+++ b/src/backend/nodes/nodeFuncs.c
@@ -4826,9 +4826,7 @@ planstate_walk_members(PlanState **planstates, int nplans,
 					   planstate_tree_walker_callback walker,
 					   void *context)
 {
-	int			j;
-
-	for (j = 0; j < nplans; j++)
+	for (int j = 0; j < nplans; j++)
 	{
 		if (PSWALK(planstates[j]))
 			return true;
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index d9fe21a07e0..0abca9f803b 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -346,8 +346,7 @@ outBitmapset(StringInfo str, const Bitmapset *bms)
 void
 outDatum(StringInfo str, Datum value, int typlen, bool typbyval)
 {
-	Size		length,
-				i;
+	Size		length;
 	char	   *s;
 
 	length = datumGetSize(value, typbyval, typlen);
@@ -356,7 +355,7 @@ outDatum(StringInfo str, Datum value, int typlen, bool typbyval)
 	{
 		s = (char *) (&value);
 		appendStringInfo(str, "%u [ ", (unsigned int) length);
-		for (i = 0; i < (Size) sizeof(Datum); i++)
+		for (Size i = 0; i < (Size) sizeof(Datum); i++)
 			appendStringInfo(str, "%d ", (int) (s[i]));
 		appendStringInfoChar(str, ']');
 	}
@@ -368,7 +367,7 @@ outDatum(StringInfo str, Datum value, int typlen, bool typbyval)
 		else
 		{
 			appendStringInfo(str, "%u [ ", (unsigned int) length);
-			for (i = 0; i < length; i++)
+			for (Size i = 0; i < length; i++)
 				appendStringInfo(str, "%d ", (int) (s[i]));
 			appendStringInfoChar(str, ']');
 		}
@@ -434,8 +433,6 @@ _outBoolExpr(StringInfo str, const BoolExpr *node)
 static void
 _outForeignKeyOptInfo(StringInfo str, const ForeignKeyOptInfo *node)
 {
-	int			i;
-
 	WRITE_NODE_TYPE("FOREIGNKEYOPTINFO");
 
 	WRITE_UINT_FIELD(con_relid);
@@ -450,10 +447,10 @@ _outForeignKeyOptInfo(StringInfo str, const ForeignKeyOptInfo *node)
 	WRITE_INT_FIELD(nmatched_ri);
 	/* for compactness, just print the number of matches per column: */
 	appendStringInfoString(str, " :eclass");
-	for (i = 0; i < node->nkeys; i++)
+	for (int i = 0; i < node->nkeys; i++)
 		appendStringInfo(str, " %d", (node->eclass[i] != NULL));
 	appendStringInfoString(str, " :rinfos");
-	for (i = 0; i < node->nkeys; i++)
+	for (int i = 0; i < node->nkeys; i++)
 		appendStringInfo(str, " %d", list_length(node->rinfos[i]));
 }
 
diff --git a/src/backend/nodes/params.c b/src/backend/nodes/params.c
index ec5946c5777..aeb8ace2c54 100644
--- a/src/backend/nodes/params.c
+++ b/src/backend/nodes/params.c
@@ -166,13 +166,12 @@ paramlist_param_ref(ParseState *pstate, ParamRef *pref)
 Size
 EstimateParamListSpace(ParamListInfo paramLI)
 {
-	int			i;
 	Size		sz = sizeof(int);
 
 	if (paramLI == NULL || paramLI->numParams <= 0)
 		return sz;
 
-	for (i = 0; i < paramLI->numParams; i++)
+	for (int i = 0; i < paramLI->numParams; i++)
 	{
 		ParamExternData *prm;
 		ParamExternData prmdata;
@@ -229,7 +228,6 @@ void
 SerializeParamList(ParamListInfo paramLI, char **start_address)
 {
 	int			nparams;
-	int			i;
 
 	/* Write number of parameters. */
 	if (paramLI == NULL || paramLI->numParams <= 0)
@@ -240,7 +238,7 @@ SerializeParamList(ParamListInfo paramLI, char **start_address)
 	*start_address += sizeof(int);
 
 	/* Write each parameter in turn. */
-	for (i = 0; i < nparams; i++)
+	for (int i = 0; i < nparams; i++)
 	{
 		ParamExternData *prm;
 		ParamExternData prmdata;
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index 2f933e95cb9..9a8ca27ec10 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -599,8 +599,7 @@ parseNodeString(void)
 Datum
 readDatum(bool typbyval)
 {
-	Size		length,
-				i;
+	Size		length;
 	int			tokenLength;
 	const char *token;
 	Datum		res;
@@ -623,7 +622,7 @@ readDatum(bool typbyval)
 			elog(ERROR, "byval datum but length = %zu", length);
 		res = (Datum) 0;
 		s = (char *) (&res);
-		for (i = 0; i < (Size) sizeof(Datum); i++)
+		for (Size i = 0; i < (Size) sizeof(Datum); i++)
 		{
 			token = pg_strtok(&tokenLength);
 			s[i] = (char) atoi(token);
@@ -634,7 +633,7 @@ readDatum(bool typbyval)
 	else
 	{
 		s = (char *) palloc(length);
-		for (i = 0; i < length; i++)
+		for (Size i = 0; i < length; i++)
 		{
 			token = pg_strtok(&tokenLength);
 			s[i] = (char) atoi(token);
diff --git a/src/backend/nodes/tidbitmap.c b/src/backend/nodes/tidbitmap.c
index 23d97b3a6c8..1f83d0d55f5 100644
--- a/src/backend/nodes/tidbitmap.c
+++ b/src/backend/nodes/tidbitmap.c
@@ -369,10 +369,9 @@ tbm_add_tuples(TIDBitmap *tbm, const ItemPointerData *tids, int ntids,
 {
 	BlockNumber currblk = InvalidBlockNumber;
 	PagetableEntry *page = NULL;	/* only valid when currblk is valid */
-	int			i;
 
 	Assert(tbm->iterating == TBM_NOT_ITERATING);
-	for (i = 0; i < ntids; i++)
+	for (int i = 0; i < ntids; i++)
 	{
 		BlockNumber blk = ItemPointerGetBlockNumber(tids + i);
 		OffsetNumber off = ItemPointerGetOffsetNumber(tids + i);
@@ -471,12 +470,11 @@ static void
 tbm_union_page(TIDBitmap *a, const PagetableEntry *bpage)
 {
 	PagetableEntry *apage;
-	int			wordnum;
 
 	if (bpage->ischunk)
 	{
 		/* Scan b's chunk, mark each indicated page lossy in a */
-		for (wordnum = 0; wordnum < WORDS_PER_CHUNK; wordnum++)
+		for (int wordnum = 0; wordnum < WORDS_PER_CHUNK; wordnum++)
 		{
 			bitmapword	w = bpage->words[wordnum];
 
@@ -511,7 +509,7 @@ tbm_union_page(TIDBitmap *a, const PagetableEntry *bpage)
 		else
 		{
 			/* Both pages are exact, merge at the bit level */
-			for (wordnum = 0; wordnum < WORDS_PER_PAGE; wordnum++)
+			for (int wordnum = 0; wordnum < WORDS_PER_PAGE; wordnum++)
 				apage->words[wordnum] |= bpage->words[wordnum];
 			apage->recheck |= bpage->recheck;
 		}
@@ -579,14 +577,13 @@ static bool
 tbm_intersect_page(TIDBitmap *a, PagetableEntry *apage, const TIDBitmap *b)
 {
 	const PagetableEntry *bpage;
-	int			wordnum;
 
 	if (apage->ischunk)
 	{
 		/* Scan each bit in chunk, try to clear */
 		bool		candelete = true;
 
-		for (wordnum = 0; wordnum < WORDS_PER_CHUNK; wordnum++)
+		for (int wordnum = 0; wordnum < WORDS_PER_CHUNK; wordnum++)
 		{
 			bitmapword	w = apage->words[wordnum];
 
@@ -640,7 +637,7 @@ tbm_intersect_page(TIDBitmap *a, PagetableEntry *apage, const TIDBitmap *b)
 		{
 			/* Both pages are exact, merge at the bit level */
 			Assert(!bpage->ischunk);
-			for (wordnum = 0; wordnum < WORDS_PER_PAGE; wordnum++)
+			for (int wordnum = 0; wordnum < WORDS_PER_PAGE; wordnum++)
 			{
 				apage->words[wordnum] &= bpage->words[wordnum];
 				if (apage->words[wordnum] != 0)
@@ -904,10 +901,9 @@ tbm_extract_page_tuple(TBMIterateResult *iteritem,
 					   uint32 max_offsets)
 {
 	PagetableEntry *page = iteritem->internal_page;
-	int			wordnum;
 	int			ntuples = 0;
 
-	for (wordnum = 0; wordnum < WORDS_PER_PAGE; wordnum++)
+	for (int wordnum = 0; wordnum < WORDS_PER_PAGE; wordnum++)
 	{
 		bitmapword	w = page->words[wordnum];
 
diff --git a/src/backend/replication/logical/slotsync.c b/src/backend/replication/logical/slotsync.c
index 8b4afd87dc9..1f4f06d467b 100644
--- a/src/backend/replication/logical/slotsync.c
+++ b/src/backend/replication/logical/slotsync.c
@@ -187,6 +187,9 @@ update_local_synced_slot(RemoteSlot *remote_slot, Oid remote_dbid,
 		TransactionIdPrecedes(remote_slot->catalog_xmin,
 							  slot->data.catalog_xmin))
 	{
+		/* Update slot sync skip stats */
+		pgstat_report_replslotsync(slot);
+
 		/*
 		 * This can happen in following situations:
 		 *
@@ -277,6 +280,13 @@ update_local_synced_slot(RemoteSlot *remote_slot, Oid remote_dbid,
 						errdetail_internal("Remote slot has LSN %X/%08X but local slot has LSN %X/%08X.",
 										   LSN_FORMAT_ARGS(remote_slot->confirmed_lsn),
 										   LSN_FORMAT_ARGS(slot->data.confirmed_flush)));
+
+			/*
+			 * If we can't reach a consistent snapshot, the slot won't be
+			 * persisted. See update_and_persist_local_synced_slot().
+			 */
+			if (found_consistent_snapshot && !(*found_consistent_snapshot))
+				pgstat_report_replslotsync(slot);
 		}
 
 		updated_xmin_or_lsn = true;
@@ -563,6 +573,7 @@ update_and_persist_local_synced_slot(RemoteSlot *remote_slot, Oid remote_dbid)
 	bool		found_consistent_snapshot = false;
 	bool		remote_slot_precedes = false;
 
+	/* Slotsync skip stats are handled in function update_local_synced_slot() */
 	(void) update_local_synced_slot(remote_slot, remote_dbid,
 									&found_consistent_snapshot,
 									&remote_slot_precedes);
@@ -624,31 +635,9 @@ static bool
 synchronize_one_slot(RemoteSlot *remote_slot, Oid remote_dbid)
 {
 	ReplicationSlot *slot;
-	XLogRecPtr	latestFlushPtr;
+	XLogRecPtr	latestFlushPtr = GetStandbyFlushRecPtr(NULL);
 	bool		slot_updated = false;
 
-	/*
-	 * Make sure that concerned WAL is received and flushed before syncing
-	 * slot to target lsn received from the primary server.
-	 */
-	latestFlushPtr = GetStandbyFlushRecPtr(NULL);
-	if (remote_slot->confirmed_lsn > latestFlushPtr)
-	{
-		/*
-		 * Can get here only if GUC 'synchronized_standby_slots' on the
-		 * primary server was not configured correctly.
-		 */
-		ereport(AmLogicalSlotSyncWorkerProcess() ? LOG : ERROR,
-				errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
-				errmsg("skipping slot synchronization because the received slot sync"
-					   " LSN %X/%08X for slot \"%s\" is ahead of the standby position %X/%08X",
-					   LSN_FORMAT_ARGS(remote_slot->confirmed_lsn),
-					   remote_slot->name,
-					   LSN_FORMAT_ARGS(latestFlushPtr)));
-
-		return false;
-	}
-
 	/* Search for the named slot */
 	if ((slot = SearchNamedReplicationSlot(remote_slot->name, true)))
 	{
@@ -707,10 +696,40 @@ synchronize_one_slot(RemoteSlot *remote_slot, Oid remote_dbid)
 		/* Skip the sync of an invalidated slot */
 		if (slot->data.invalidated != RS_INVAL_NONE)
 		{
+			pgstat_report_replslotsync(slot);
+
 			ReplicationSlotRelease();
 			return slot_updated;
 		}
 
+		/*
+		 * Make sure that concerned WAL is received and flushed before syncing
+		 * slot to target lsn received from the primary server.
+		 *
+		 * Report statistics only after the slot has been acquired, ensuring
+		 * it cannot be dropped during the reporting process.
+		 */
+		if (remote_slot->confirmed_lsn > latestFlushPtr)
+		{
+			pgstat_report_replslotsync(slot);
+
+			/*
+			 * Can get here only if GUC 'synchronized_standby_slots' on the
+			 * primary server was not configured correctly.
+			 */
+			ereport(AmLogicalSlotSyncWorkerProcess() ? LOG : ERROR,
+					errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					errmsg("skipping slot synchronization because the received slot sync"
+						   " LSN %X/%08X for slot \"%s\" is ahead of the standby position %X/%08X",
+						   LSN_FORMAT_ARGS(remote_slot->confirmed_lsn),
+						   remote_slot->name,
+						   LSN_FORMAT_ARGS(latestFlushPtr)));
+
+			ReplicationSlotRelease();
+
+			return slot_updated;
+		}
+
 		/* Slot not ready yet, let's attempt to make it sync-ready now. */
 		if (slot->data.persistency == RS_TEMPORARY)
 		{
@@ -784,6 +803,34 @@ synchronize_one_slot(RemoteSlot *remote_slot, Oid remote_dbid)
 		ReplicationSlotsComputeRequiredXmin(true);
 		LWLockRelease(ProcArrayLock);
 
+		/*
+		 * Make sure that concerned WAL is received and flushed before syncing
+		 * slot to target lsn received from the primary server.
+		 *
+		 * Report statistics only after the slot has been acquired, ensuring
+		 * it cannot be dropped during the reporting process.
+		 */
+		if (remote_slot->confirmed_lsn > latestFlushPtr)
+		{
+			pgstat_report_replslotsync(slot);
+
+			/*
+			 * Can get here only if GUC 'synchronized_standby_slots' on the
+			 * primary server was not configured correctly.
+			 */
+			ereport(AmLogicalSlotSyncWorkerProcess() ? LOG : ERROR,
+					errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					errmsg("skipping slot synchronization because the received slot sync"
+						   " LSN %X/%08X for slot \"%s\" is ahead of the standby position %X/%08X",
+						   LSN_FORMAT_ARGS(remote_slot->confirmed_lsn),
+						   remote_slot->name,
+						   LSN_FORMAT_ARGS(latestFlushPtr)));
+
+			ReplicationSlotRelease();
+
+			return false;
+		}
+
 		update_and_persist_local_synced_slot(remote_slot, remote_dbid);
 
 		slot_updated = true;
diff --git a/src/backend/storage/lmgr/lwlock.c b/src/backend/storage/lmgr/lwlock.c
index b017880f5e4..255cfa8fa95 100644
--- a/src/backend/storage/lmgr/lwlock.c
+++ b/src/backend/storage/lmgr/lwlock.c
@@ -998,7 +998,7 @@ LWLockWakeup(LWLock *lock)
 			else
 				desired_state &= ~LW_FLAG_RELEASE_OK;
 
-			if (proclist_is_empty(&wakeup))
+			if (proclist_is_empty(&lock->waiters))
 				desired_state &= ~LW_FLAG_HAS_WAITERS;
 
 			desired_state &= ~LW_FLAG_LOCKED;	/* release lock */
diff --git a/src/backend/utils/activity/pgstat.c b/src/backend/utils/activity/pgstat.c
index 7ef06150df7..8713c7a0483 100644
--- a/src/backend/utils/activity/pgstat.c
+++ b/src/backend/utils/activity/pgstat.c
@@ -1551,20 +1551,18 @@ pgstat_assert_is_up(void)
  * ------------------------------------------------------------
  */
 
-/* helpers for pgstat_write_statsfile() */
-static void
-write_chunk(FILE *fpout, void *ptr, size_t len)
+/* helper for pgstat_write_statsfile() */
+void
+pgstat_write_chunk(FILE *fpout, void *ptr, size_t len)
 {
 	int			rc;
 
 	rc = fwrite(ptr, len, 1, fpout);
 
-	/* we'll check for errors with ferror once at the end */
+	/* We check for errors with ferror() when done writing the stats. */
 	(void) rc;
 }
 
-#define write_chunk_s(fpout, ptr) write_chunk(fpout, ptr, sizeof(*ptr))
-
 /*
  * This function is called in the last process that is accessing the shared
  * stats so locking is not required.
@@ -1606,7 +1604,7 @@ pgstat_write_statsfile(void)
 	 * Write the file header --- currently just a format ID.
 	 */
 	format_id = PGSTAT_FILE_FORMAT_ID;
-	write_chunk_s(fpout, &format_id);
+	pgstat_write_chunk_s(fpout, &format_id);
 
 	/* Write various stats structs for fixed number of objects */
 	for (PgStat_Kind kind = PGSTAT_KIND_MIN; kind <= PGSTAT_KIND_MAX; kind++)
@@ -1631,8 +1629,8 @@ pgstat_write_statsfile(void)
 			ptr = pgStatLocal.snapshot.custom_data[kind - PGSTAT_KIND_CUSTOM_MIN];
 
 		fputc(PGSTAT_FILE_ENTRY_FIXED, fpout);
-		write_chunk_s(fpout, &kind);
-		write_chunk(fpout, ptr, info->shared_data_len);
+		pgstat_write_chunk_s(fpout, &kind);
+		pgstat_write_chunk(fpout, ptr, info->shared_data_len);
 	}
 
 	/*
@@ -1686,7 +1684,7 @@ pgstat_write_statsfile(void)
 		{
 			/* normal stats entry, identified by PgStat_HashKey */
 			fputc(PGSTAT_FILE_ENTRY_HASH, fpout);
-			write_chunk_s(fpout, &ps->key);
+			pgstat_write_chunk_s(fpout, &ps->key);
 		}
 		else
 		{
@@ -1696,21 +1694,21 @@ pgstat_write_statsfile(void)
 			kind_info->to_serialized_name(&ps->key, shstats, &name);
 
 			fputc(PGSTAT_FILE_ENTRY_NAME, fpout);
-			write_chunk_s(fpout, &ps->key.kind);
-			write_chunk_s(fpout, &name);
+			pgstat_write_chunk_s(fpout, &ps->key.kind);
+			pgstat_write_chunk_s(fpout, &name);
 		}
 
 		/* Write except the header part of the entry */
-		write_chunk(fpout,
-					pgstat_get_entry_data(ps->key.kind, shstats),
-					pgstat_get_entry_len(ps->key.kind));
+		pgstat_write_chunk(fpout,
+						   pgstat_get_entry_data(ps->key.kind, shstats),
+						   pgstat_get_entry_len(ps->key.kind));
 	}
 	dshash_seq_term(&hstat);
 
 	/*
 	 * No more output to be done. Close the temp file and replace the old
 	 * pgstat.stat with it.  The ferror() check replaces testing for error
-	 * after each individual fputc or fwrite (in write_chunk()) above.
+	 * after each individual fputc or fwrite (in pgstat_write_chunk()) above.
 	 */
 	fputc(PGSTAT_FILE_ENTRY_END, fpout);
 
@@ -1738,15 +1736,13 @@ pgstat_write_statsfile(void)
 	}
 }
 
-/* helpers for pgstat_read_statsfile() */
-static bool
-read_chunk(FILE *fpin, void *ptr, size_t len)
+/* helper for pgstat_read_statsfile() */
+bool
+pgstat_read_chunk(FILE *fpin, void *ptr, size_t len)
 {
 	return fread(ptr, 1, len, fpin) == len;
 }
 
-#define read_chunk_s(fpin, ptr) read_chunk(fpin, ptr, sizeof(*ptr))
-
 /*
  * Reads in existing statistics file into memory.
  *
@@ -1790,7 +1786,7 @@ pgstat_read_statsfile(void)
 	/*
 	 * Verify it's of the expected format.
 	 */
-	if (!read_chunk_s(fpin, &format_id))
+	if (!pgstat_read_chunk_s(fpin, &format_id))
 	{
 		elog(WARNING, "could not read format ID");
 		goto error;
@@ -1820,7 +1816,7 @@ pgstat_read_statsfile(void)
 					char	   *ptr;
 
 					/* entry for fixed-numbered stats */
-					if (!read_chunk_s(fpin, &kind))
+					if (!pgstat_read_chunk_s(fpin, &kind))
 					{
 						elog(WARNING, "could not read stats kind for entry of type %c", t);
 						goto error;
@@ -1860,7 +1856,7 @@ pgstat_read_statsfile(void)
 							info->shared_data_off;
 					}
 
-					if (!read_chunk(fpin, ptr, info->shared_data_len))
+					if (!pgstat_read_chunk(fpin, ptr, info->shared_data_len))
 					{
 						elog(WARNING, "could not read data of stats kind %u for entry of type %c with size %u",
 							 kind, t, info->shared_data_len);
@@ -1881,7 +1877,7 @@ pgstat_read_statsfile(void)
 					if (t == PGSTAT_FILE_ENTRY_HASH)
 					{
 						/* normal stats entry, identified by PgStat_HashKey */
-						if (!read_chunk_s(fpin, &key))
+						if (!pgstat_read_chunk_s(fpin, &key))
 						{
 							elog(WARNING, "could not read key for entry of type %c", t);
 							goto error;
@@ -1910,12 +1906,12 @@ pgstat_read_statsfile(void)
 						PgStat_Kind kind;
 						NameData	name;
 
-						if (!read_chunk_s(fpin, &kind))
+						if (!pgstat_read_chunk_s(fpin, &kind))
 						{
 							elog(WARNING, "could not read stats kind for entry of type %c", t);
 							goto error;
 						}
-						if (!read_chunk_s(fpin, &name))
+						if (!pgstat_read_chunk_s(fpin, &name))
 						{
 							elog(WARNING, "could not read name of stats kind %u for entry of type %c",
 								 kind, t);
@@ -1990,9 +1986,9 @@ pgstat_read_statsfile(void)
 							 key.objid, t);
 					}
 
-					if (!read_chunk(fpin,
-									pgstat_get_entry_data(key.kind, header),
-									pgstat_get_entry_len(key.kind)))
+					if (!pgstat_read_chunk(fpin,
+										   pgstat_get_entry_data(key.kind, header),
+										   pgstat_get_entry_len(key.kind)))
 					{
 						elog(WARNING, "could not read data for entry %u/%u/%" PRIu64 " of type %c",
 							 key.kind, key.dboid,
diff --git a/src/backend/utils/activity/pgstat_replslot.c b/src/backend/utils/activity/pgstat_replslot.c
index d210c261ac6..f93179146c2 100644
--- a/src/backend/utils/activity/pgstat_replslot.c
+++ b/src/backend/utils/activity/pgstat_replslot.c
@@ -103,6 +103,36 @@ pgstat_report_replslot(ReplicationSlot *slot, const PgStat_StatReplSlotEntry *re
 }
 
 /*
+ * Report replication slot sync skip statistics.
+ *
+ * Similar to pgstat_report_replslot(), we can rely on the stats for the
+ * slot to exist and to belong to this slot.
+ */
+void
+pgstat_report_replslotsync(ReplicationSlot *slot)
+{
+	PgStat_EntryRef *entry_ref;
+	PgStatShared_ReplSlot *shstatent;
+	PgStat_StatReplSlotEntry *statent;
+
+	/* Slot sync stats are valid only for logical slots on standby. */
+	Assert(SlotIsLogical(slot));
+	Assert(RecoveryInProgress());
+
+	entry_ref = pgstat_get_entry_ref_locked(PGSTAT_KIND_REPLSLOT, InvalidOid,
+											ReplicationSlotIndex(slot), false);
+	Assert(entry_ref != NULL);
+
+	shstatent = (PgStatShared_ReplSlot *) entry_ref->shared_stats;
+	statent = &shstatent->stats;
+
+	statent->slotsync_skip_count += 1;
+	statent->slotsync_skip_at = GetCurrentTimestamp();
+
+	pgstat_unlock_entry(entry_ref);
+}
+
+/*
  * Report replication slot creation.
  *
  * NB: This gets called with ReplicationSlotAllocationLock already held, be
@@ -133,7 +163,7 @@ pgstat_create_replslot(ReplicationSlot *slot)
  * Report replication slot has been acquired.
  *
  * This guarantees that a stats entry exists during later
- * pgstat_report_replslot() calls.
+ * pgstat_report_replslot() or pgstat_report_replslotsync() calls.
  *
  * If we previously crashed, no stats data exists. But if we did not crash,
  * the stats do belong to this slot:
diff --git a/src/backend/utils/adt/formatting.c b/src/backend/utils/adt/formatting.c
index 5f7b3114da7..5bfeda2ffde 100644
--- a/src/backend/utils/adt/formatting.c
+++ b/src/backend/utils/adt/formatting.c
@@ -1617,16 +1617,6 @@ str_numth(char *dest, const char *num, enum TH_Case type)
  *****************************************************************************/
 
 /*
- * If the system provides the needed functions for wide-character manipulation
- * (which are all standardized by C99), then we implement upper/lower/initcap
- * using wide-character functions, if necessary.  Otherwise we use the
- * traditional <ctype.h> functions, which of course will not work as desired
- * in multibyte character sets.  Note that in either case we are effectively
- * assuming that the database character encoding matches the encoding implied
- * by LC_CTYPE.
- */
-
-/*
  * collation-aware, wide-character-aware lower function
  *
  * We pass the number of bytes so we can pass varlena and char*
diff --git a/src/backend/utils/adt/pg_locale_libc.c b/src/backend/utils/adt/pg_locale_libc.c
index 716f005066a..abf27283a33 100644
--- a/src/backend/utils/adt/pg_locale_libc.c
+++ b/src/backend/utils/adt/pg_locale_libc.c
@@ -434,9 +434,6 @@ strlower_libc_sb(char *dest, size_t destsize, const char *src, ssize_t srclen,
 		locale_t	loc = locale->lt;
 		char	   *p;
 
-		if (srclen + 1 > destsize)
-			return srclen;
-
 		memcpy(dest, src, srclen);
 		dest[srclen] = '\0';
 
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 3d98d064a94..7e2ed69138a 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -2129,7 +2129,7 @@ pg_stat_get_archiver(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_replication_slot(PG_FUNCTION_ARGS)
 {
-#define PG_STAT_GET_REPLICATION_SLOT_COLS 11
+#define PG_STAT_GET_REPLICATION_SLOT_COLS 13
 	text	   *slotname_text = PG_GETARG_TEXT_P(0);
 	NameData	slotname;
 	TupleDesc	tupdesc;
@@ -2160,7 +2160,11 @@ pg_stat_get_replication_slot(PG_FUNCTION_ARGS)
 					   INT8OID, -1, 0);
 	TupleDescInitEntry(tupdesc, (AttrNumber) 10, "total_bytes",
 					   INT8OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 11, "stats_reset",
+	TupleDescInitEntry(tupdesc, (AttrNumber) 11, "slotsync_skip_count",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 12, "slotsync_skip_at",
+					   TIMESTAMPTZOID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 13, "stats_reset",
 					   TIMESTAMPTZOID, -1, 0);
 	BlessTupleDesc(tupdesc);
 
@@ -2186,11 +2190,17 @@ pg_stat_get_replication_slot(PG_FUNCTION_ARGS)
 	values[7] = Int64GetDatum(slotent->mem_exceeded_count);
 	values[8] = Int64GetDatum(slotent->total_txns);
 	values[9] = Int64GetDatum(slotent->total_bytes);
+	values[10] = Int64GetDatum(slotent->slotsync_skip_count);
+
+	if (slotent->slotsync_skip_at == 0)
+		nulls[11] = true;
+	else
+		values[11] = TimestampTzGetDatum(slotent->slotsync_skip_at);
 
 	if (slotent->stat_reset_timestamp == 0)
-		nulls[10] = true;
+		nulls[12] = true;
 	else
-		values[10] = TimestampTzGetDatum(slotent->stat_reset_timestamp);
+		values[12] = TimestampTzGetDatum(slotent->stat_reset_timestamp);
 
 	/* Returns the record as Datum */
 	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
diff --git a/src/backend/utils/misc/gen_guc_tables.pl b/src/backend/utils/misc/gen_guc_tables.pl
index 601c34ec30b..562819b7832 100644
--- a/src/backend/utils/misc/gen_guc_tables.pl
+++ b/src/backend/utils/misc/gen_guc_tables.pl
@@ -38,6 +38,52 @@ sub dquote
 	return q{"} . $s =~ s/"/\\"/gr . q{"};
 }
 
+sub validate_guc_entry
+{
+	my ($entry) = @_;
+
+	my @required_common =
+	  qw(name type context group short_desc variable boot_val);
+
+	my %required_by_type = (
+		int => [qw(min max)],
+		real => [qw(min max)],
+		enum => [qw(options)],
+		bool => [],      # no extra required fields
+		string => [],    # no extra required fields
+	);
+
+	for my $f (@required_common)
+	{
+		unless (defined $entry->{$f})
+		{
+			die sprintf(
+				qq{%s:%d: error: entry "%s" is missing required field "%s"\n},
+				$input_fname, $entry->{line_number},
+				$entry->{name} // '<unknown>', $f);
+		}
+	}
+
+	unless (exists $required_by_type{ $entry->{type} })
+	{
+		die sprintf(
+			qq{%s:%d: error: entry "%s" has unrecognized GUC type "%s"\n},
+			$input_fname, $entry->{line_number},
+			$entry->{name}, $entry->{type} // '<unknown>');
+	}
+
+	for my $f (@{ $required_by_type{ $entry->{type} } })
+	{
+		unless (defined $entry->{$f})
+		{
+			die sprintf(
+				qq{%s:%d: error: entry "%s" of type "%s" is missing required field "%s"\n},
+				$input_fname, $entry->{line_number}, $entry->{name},
+				$entry->{type}, $f);
+		}
+	}
+}
+
 # Print GUC table.
 sub print_table
 {
@@ -50,6 +96,8 @@ sub print_table
 
 	foreach my $entry (@{$parse})
 	{
+		validate_guc_entry($entry);
+
 		if (defined($prev_name) && lc($prev_name) ge lc($entry->{name}))
 		{
 			die sprintf(
diff --git a/src/backend/utils/time/snapmgr.c b/src/backend/utils/time/snapmgr.c
index 24f73a49d27..434abbf6b6f 100644
--- a/src/backend/utils/time/snapmgr.c
+++ b/src/backend/utils/time/snapmgr.c
@@ -459,6 +459,7 @@ InvalidateCatalogSnapshot(void)
 		pairingheap_remove(&RegisteredSnapshots, &CatalogSnapshot->ph_node);
 		CatalogSnapshot = NULL;
 		SnapshotResetXmin();
+		INJECTION_POINT("pre-invalidate-catalog-snapshot-end", NULL);
 		INJECTION_POINT("invalidate-catalog-snapshot-end", NULL);
 	}
 }