v59-0001-Handle-logical-slot-conflicts-on-standby.patch

From 5074e0917c4568b7d016d5e08dc43ac1c241b199 Mon Sep 17 00:00:00 2001
From: bdrouvotAWS <bdrouvot@amazon.com>
Date: Tue, 7 Feb 2023 08:57:56 +0000
Subject: [PATCH v59 1/6] Handle logical slot conflicts on standby.
MIME-Version: 1.0
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During WAL replay on standby, when slot conflict is identified,
invalidate such slots. Also do the same thing if wal_level on the primary server
is reduced to below logical and there are existing logical slots
on standby. Introduce a new ProcSignalReason value for slot
conflict recovery.

Author: Andres Freund (in an older version), Amit Khandekar, Bertrand Drouvot
Reviewed-By: Bertrand Drouvot, Andres Freund, Robert Haas, Fabrizio de Royes Mello,
Bharath Rupireddy, Amit Kapila, Álvaro Herrera
---
 src/backend/access/gist/gistxlog.c            |   2 +
 src/backend/access/hash/hash_xlog.c           |   1 +
 src/backend/access/heap/heapam.c              |   3 +
 src/backend/access/nbtree/nbtxlog.c           |   2 +
 src/backend/access/spgist/spgxlog.c           |   1 +
 src/backend/access/transam/xlog.c             |  21 +-
 .../replication/logical/logicalfuncs.c        |  13 +-
 src/backend/replication/slot.c                | 190 ++++++++++++++----
 src/backend/replication/slotfuncs.c           |   3 +-
 src/backend/replication/walsender.c           |   7 +
 src/backend/storage/ipc/procsignal.c          |   3 +
 src/backend/storage/ipc/standby.c             |  13 +-
 src/backend/tcop/postgres.c                   |  28 +++
 src/include/replication/slot.h                |  55 ++++-
 src/include/storage/procsignal.h              |   1 +
 src/include/storage/standby.h                 |   2 +
 16 files changed, 294 insertions(+), 51 deletions(-)
   7.0% src/backend/access/transam/
   5.3% src/backend/replication/logical/
  58.2% src/backend/replication/
   5.0% src/backend/storage/ipc/
   7.8% src/backend/tcop/
  13.0% src/include/replication/
   3.3% src/

diff --git a/src/backend/access/gist/gistxlog.c b/src/backend/access/gist/gistxlog.c
index b7678f3c14..9a86fb3fef 100644
--- a/src/backend/access/gist/gistxlog.c
+++ b/src/backend/access/gist/gistxlog.c
@@ -197,6 +197,7 @@ gistRedoDeleteRecord(XLogReaderState *record)
 		XLogRecGetBlockTag(record, 0, &rlocator, NULL, NULL);
 
 		ResolveRecoveryConflictWithSnapshot(xldata->snapshotConflictHorizon,
+											xldata->isCatalogRel,
 											rlocator);
 	}
 
@@ -390,6 +391,7 @@ gistRedoPageReuse(XLogReaderState *record)
 	 */
 	if (InHotStandby)
 		ResolveRecoveryConflictWithSnapshotFullXid(xlrec->snapshotConflictHorizon,
+												   xlrec->isCatalogRel,
 												   xlrec->locator);
 }
 
diff --git a/src/backend/access/hash/hash_xlog.c b/src/backend/access/hash/hash_xlog.c
index f2dd9be8d3..e8e06c62a9 100644
--- a/src/backend/access/hash/hash_xlog.c
+++ b/src/backend/access/hash/hash_xlog.c
@@ -1003,6 +1003,7 @@ hash_xlog_vacuum_one_page(XLogReaderState *record)
 
 		XLogRecGetBlockTag(record, 0, &rlocator, NULL, NULL);
 		ResolveRecoveryConflictWithSnapshot(xldata->snapshotConflictHorizon,
+											xldata->isCatalogRel,
 											rlocator);
 	}
 
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index f7d9ce59a4..371e855683 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -8717,6 +8717,7 @@ heap_xlog_prune(XLogReaderState *record)
 	 */
 	if (InHotStandby)
 		ResolveRecoveryConflictWithSnapshot(xlrec->snapshotConflictHorizon,
+											xlrec->isCatalogRel,
 											rlocator);
 
 	/*
@@ -8888,6 +8889,7 @@ heap_xlog_visible(XLogReaderState *record)
 	 */
 	if (InHotStandby)
 		ResolveRecoveryConflictWithSnapshot(xlrec->snapshotConflictHorizon,
+											xlrec->flags & VISIBILITYMAP_XLOG_CATALOG_REL,
 											rlocator);
 
 	/*
@@ -9009,6 +9011,7 @@ heap_xlog_freeze_page(XLogReaderState *record)
 
 		XLogRecGetBlockTag(record, 0, &rlocator, NULL, NULL);
 		ResolveRecoveryConflictWithSnapshot(xlrec->snapshotConflictHorizon,
+											xlrec->isCatalogRel,
 											rlocator);
 	}
 
diff --git a/src/backend/access/nbtree/nbtxlog.c b/src/backend/access/nbtree/nbtxlog.c
index 414ca4f6de..c87e46ed66 100644
--- a/src/backend/access/nbtree/nbtxlog.c
+++ b/src/backend/access/nbtree/nbtxlog.c
@@ -669,6 +669,7 @@ btree_xlog_delete(XLogReaderState *record)
 		XLogRecGetBlockTag(record, 0, &rlocator, NULL, NULL);
 
 		ResolveRecoveryConflictWithSnapshot(xlrec->snapshotConflictHorizon,
+											xlrec->isCatalogRel,
 											rlocator);
 	}
 
@@ -1007,6 +1008,7 @@ btree_xlog_reuse_page(XLogReaderState *record)
 
 	if (InHotStandby)
 		ResolveRecoveryConflictWithSnapshotFullXid(xlrec->snapshotConflictHorizon,
+												   xlrec->isCatalogRel,
 												   xlrec->locator);
 }
 
diff --git a/src/backend/access/spgist/spgxlog.c b/src/backend/access/spgist/spgxlog.c
index b071b59c8a..459ac929ba 100644
--- a/src/backend/access/spgist/spgxlog.c
+++ b/src/backend/access/spgist/spgxlog.c
@@ -879,6 +879,7 @@ spgRedoVacuumRedirect(XLogReaderState *record)
 
 		XLogRecGetBlockTag(record, 0, &locator, NULL, NULL);
 		ResolveRecoveryConflictWithSnapshot(xldata->snapshotConflictHorizon,
+											xldata->isCatalogRel,
 											locator);
 	}
 
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 46821ad605..10085aa0d6 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -6806,7 +6806,7 @@ CreateCheckPoint(int flags)
 	 */
 	XLByteToSeg(RedoRecPtr, _logSegNo, wal_segment_size);
 	KeepLogSeg(recptr, &_logSegNo);
-	if (InvalidateObsoleteReplicationSlots(_logSegNo))
+	if (InvalidateObsoleteReplicationSlots(_logSegNo, InvalidOid, NULL))
 	{
 		/*
 		 * Some slots have been invalidated; recalculate the old-segment
@@ -7250,7 +7250,7 @@ CreateRestartPoint(int flags)
 	replayPtr = GetXLogReplayRecPtr(&replayTLI);
 	endptr = (receivePtr < replayPtr) ? replayPtr : receivePtr;
 	KeepLogSeg(endptr, &_logSegNo);
-	if (InvalidateObsoleteReplicationSlots(_logSegNo))
+	if (InvalidateObsoleteReplicationSlots(_logSegNo, InvalidOid, NULL))
 	{
 		/*
 		 * Some slots have been invalidated; recalculate the old-segment
@@ -7963,6 +7963,23 @@ xlog_redo(XLogReaderState *record)
 		/* Update our copy of the parameters in pg_control */
 		memcpy(&xlrec, XLogRecGetData(record), sizeof(xl_parameter_change));
 
+		/*
+		 * Invalidate logical slots if we are in hot standby and the primary
+		 * does not have a WAL level sufficient for logical decoding. No need
+		 * to search for potentially conflicting logically slots if standby is
+		 * running with wal_level lower than logical, because in that case, we
+		 * would have either disallowed creation of logical slots or
+		 * invalidated existing ones.
+		 */
+		if (InRecovery && InHotStandby &&
+			xlrec.wal_level < WAL_LEVEL_LOGICAL &&
+			wal_level >= WAL_LEVEL_LOGICAL)
+		{
+			TransactionId ConflictHorizon = InvalidTransactionId;
+
+			InvalidateObsoleteReplicationSlots(InvalidXLogRecPtr, InvalidOid, &ConflictHorizon);
+		}
+
 		LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
 		ControlFile->MaxConnections = xlrec.MaxConnections;
 		ControlFile->max_worker_processes = xlrec.max_worker_processes;
diff --git a/src/backend/replication/logical/logicalfuncs.c b/src/backend/replication/logical/logicalfuncs.c
index fa1b641a2b..575a047e53 100644
--- a/src/backend/replication/logical/logicalfuncs.c
+++ b/src/backend/replication/logical/logicalfuncs.c
@@ -216,9 +216,9 @@ pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool bin
 
 		/*
 		 * After the sanity checks in CreateDecodingContext, make sure the
-		 * restart_lsn is valid.  Avoid "cannot get changes" wording in this
-		 * errmsg because that'd be confusingly ambiguous about no changes
-		 * being available.
+		 * restart_lsn is valid or both effective_xmin and catalog_xmin are
+		 * valid. Avoid "cannot get changes" wording in this errmsg because
+		 * that'd be confusingly ambiguous about no changes being available.
 		 */
 		if (XLogRecPtrIsInvalid(MyReplicationSlot->data.restart_lsn))
 			ereport(ERROR,
@@ -227,6 +227,13 @@ pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool bin
 							NameStr(*name)),
 					 errdetail("This slot has never previously reserved WAL, or it has been invalidated.")));
 
+		if (LogicalReplicationSlotIsInvalid(MyReplicationSlot))
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					 errmsg("cannot read from logical replication slot \"%s\"",
+							NameStr(*name)),
+					 errdetail("This slot has been invalidated because it was conflicting with recovery.")));
+
 		MemoryContextSwitchTo(oldcontext);
 
 		/*
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index 2293c0c6fc..3e81784579 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -110,6 +110,13 @@ static void RestoreSlotFromDisk(const char *name);
 static void CreateSlotOnDisk(ReplicationSlot *slot);
 static void SaveSlotToPath(ReplicationSlot *slot, const char *dir, int elevel);
 
+/* to report termination/invalidation */
+static void ReportTerminationInvalidation(bool terminating, bool check_on_xid,
+										  int pid, NameData slotname,
+										  TransactionId *xid,
+										  XLogRecPtr restart_lsn,
+										  XLogRecPtr oldestLSN);
+
 /*
  * Report shared-memory space needed by ReplicationSlotsShmemInit.
  */
@@ -855,8 +862,7 @@ ReplicationSlotsComputeRequiredXmin(bool already_locked)
 		SpinLockAcquire(&s->mutex);
 		effective_xmin = s->effective_xmin;
 		effective_catalog_xmin = s->effective_catalog_xmin;
-		invalidated = (!XLogRecPtrIsInvalid(s->data.invalidated_at) &&
-					   XLogRecPtrIsInvalid(s->data.restart_lsn));
+		invalidated = ObsoleteSlotIsInvalid(s, true) || LogicalReplicationSlotIsInvalid(s);
 		SpinLockRelease(&s->mutex);
 
 		/* invalidated slots need not apply */
@@ -1225,28 +1231,93 @@ ReplicationSlotReserveWal(void)
 	}
 }
 
+
+/*
+ * Report terminating or conflicting message.
+ *
+ * For both, logical conflict on standby and obsolete slot are handled.
+ */
+static void
+ReportTerminationInvalidation(bool terminating, bool check_on_xid, int pid,
+							  NameData slotname, TransactionId *xid,
+							  XLogRecPtr restart_lsn, XLogRecPtr oldestLSN)
+{
+	StringInfoData err_msg;
+	StringInfoData err_detail;
+	bool		hint = false;
+
+	initStringInfo(&err_msg);
+	initStringInfo(&err_detail);
+
+	if (terminating)
+		appendStringInfo(&err_msg, _("terminating process %d to release replication slot \"%s\""),
+						 pid,
+						 NameStr(slotname));
+	else
+		appendStringInfo(&err_msg, _("invalidating"));
+
+	if (check_on_xid)
+	{
+		if (terminating)
+			appendStringInfo(&err_msg, _(" because it conflicts with recovery"));
+
+		if (TransactionIdIsValid(*xid))
+			appendStringInfo(&err_detail, _("The slot conflicted with xid horizon %u."), *xid);
+		else
+			appendStringInfo(&err_detail, _("Logical decoding on standby requires wal_level to be at least logical on the primary server"));
+	}
+	else
+	{
+		if (!terminating)
+			appendStringInfo(&err_msg, _(" obsolete replication"));
+
+		appendStringInfo(&err_detail, _("The slot's restart_lsn %X/%X exceeds the limit by %llu bytes."),
+						 LSN_FORMAT_ARGS(restart_lsn),
+						 (unsigned long long) (oldestLSN - restart_lsn));
+
+		hint = true;
+	}
+
+	if (!terminating)
+		appendStringInfo(&err_msg, _(" slot \"%s\" because it conflicts with recovery"),
+						 NameStr(slotname));
+
+	ereport(LOG,
+			errmsg("%s", err_msg.data),
+			errdetail("%s", err_detail.data),
+			hint ? errhint("You might need to increase max_slot_wal_keep_size.") : 0);
+
+	pfree(err_msg.data);
+	pfree(err_detail.data);
+}
+
 /*
- * Helper for InvalidateObsoleteReplicationSlots -- acquires the given slot
- * and mark it invalid, if necessary and possible.
+ * Helper for InvalidateObsoleteReplicationSlots
+ *
+ * Acquires the given slot and mark it invalid, if necessary and possible.
  *
  * Returns whether ReplicationSlotControlLock was released in the interim (and
  * in that case we're not holding the lock at return, otherwise we are).
  *
- * Sets *invalidated true if the slot was invalidated. (Untouched otherwise.)
+ * Sets *invalidated true if an obsolete slot was invalidated. (Untouched otherwise.)
  *
  * This is inherently racy, because we release the LWLock
  * for syscalls, so caller must restart if we return true.
  */
 static bool
 InvalidatePossiblyObsoleteSlot(ReplicationSlot *s, XLogRecPtr oldestLSN,
-							   bool *invalidated)
+							   bool *invalidated, TransactionId *xid)
 {
 	int			last_signaled_pid = 0;
 	bool		released_lock = false;
+	bool		check_on_xid;
+
+	check_on_xid = xid ? true : false;
 
 	for (;;)
 	{
 		XLogRecPtr	restart_lsn;
+
 		NameData	slotname;
 		int			active_pid = 0;
 
@@ -1263,19 +1334,20 @@ InvalidatePossiblyObsoleteSlot(ReplicationSlot *s, XLogRecPtr oldestLSN,
 		 * Check if the slot needs to be invalidated. If it needs to be
 		 * invalidated, and is not currently acquired, acquire it and mark it
 		 * as having been invalidated.  We do this with the spinlock held to
-		 * avoid race conditions -- for example the restart_lsn could move
-		 * forward, or the slot could be dropped.
+		 * avoid race conditions -- for example the restart_lsn (or the
+		 * xmin(s) could) move forward or the slot could be dropped.
 		 */
 		SpinLockAcquire(&s->mutex);
 
 		restart_lsn = s->data.restart_lsn;
 
 		/*
-		 * If the slot is already invalid or is fresh enough, we don't need to
-		 * do anything.
+		 * If the slot is already invalid or is a non conflicting slot, we
+		 * don't need to do anything.
 		 */
-		if (XLogRecPtrIsInvalid(restart_lsn) || restart_lsn >= oldestLSN)
+		if (DoNotInvalidateSlot(s, xid, &oldestLSN))
 		{
+			/* then, we are not forcing for invalidation */
 			SpinLockRelease(&s->mutex);
 			if (released_lock)
 				LWLockRelease(ReplicationSlotControlLock);
@@ -1294,9 +1366,16 @@ InvalidatePossiblyObsoleteSlot(ReplicationSlot *s, XLogRecPtr oldestLSN,
 		{
 			MyReplicationSlot = s;
 			s->active_pid = MyProcPid;
-			s->data.invalidated_at = restart_lsn;
-			s->data.restart_lsn = InvalidXLogRecPtr;
-
+			if (xid)
+			{
+				s->effective_xmin = InvalidTransactionId;
+				s->data.catalog_xmin = InvalidTransactionId;
+			}
+			else
+			{
+				s->data.invalidated_at = restart_lsn;
+				s->data.restart_lsn = InvalidXLogRecPtr;
+			}
 			/* Let caller know */
 			*invalidated = true;
 		}
@@ -1329,15 +1408,15 @@ InvalidatePossiblyObsoleteSlot(ReplicationSlot *s, XLogRecPtr oldestLSN,
 			 */
 			if (last_signaled_pid != active_pid)
 			{
-				ereport(LOG,
-						errmsg("terminating process %d to release replication slot \"%s\"",
-							   active_pid, NameStr(slotname)),
-						errdetail("The slot's restart_lsn %X/%X exceeds the limit by %llu bytes.",
-								  LSN_FORMAT_ARGS(restart_lsn),
-								  (unsigned long long) (oldestLSN - restart_lsn)),
-						errhint("You might need to increase max_slot_wal_keep_size."));
-
-				(void) kill(active_pid, SIGTERM);
+				ReportTerminationInvalidation(true, check_on_xid, active_pid,
+											  slotname, xid, restart_lsn,
+											  oldestLSN);
+
+				if (check_on_xid)
+					(void) SendProcSignal(active_pid, PROCSIG_RECOVERY_CONFLICT_LOGICALSLOT, InvalidBackendId);
+				else
+					(void) kill(active_pid, SIGTERM);
+
 				last_signaled_pid = active_pid;
 			}
 
@@ -1370,14 +1449,11 @@ InvalidatePossiblyObsoleteSlot(ReplicationSlot *s, XLogRecPtr oldestLSN,
 			ReplicationSlotMarkDirty();
 			ReplicationSlotSave();
 			ReplicationSlotRelease();
+			pgstat_drop_replslot(s);
 
-			ereport(LOG,
-					errmsg("invalidating obsolete replication slot \"%s\"",
-						   NameStr(slotname)),
-					errdetail("The slot's restart_lsn %X/%X exceeds the limit by %llu bytes.",
-							  LSN_FORMAT_ARGS(restart_lsn),
-							  (unsigned long long) (oldestLSN - restart_lsn)),
-					errhint("You might need to increase max_slot_wal_keep_size."));
+			ReportTerminationInvalidation(false, check_on_xid, active_pid,
+										  slotname, xid, restart_lsn,
+										  oldestLSN);
 
 			/* done with this slot for now */
 			break;
@@ -1390,20 +1466,36 @@ InvalidatePossiblyObsoleteSlot(ReplicationSlot *s, XLogRecPtr oldestLSN,
 }
 
 /*
- * Mark any slot that points to an LSN older than the given segment
- * as invalid; it requires WAL that's about to be removed.
+ * Invalidate Obsolete slots or resolve recovery conflicts with logical slots.
+ *
+ * Obsolete case (aka xid is NULL):
  *
- * Returns true when any slot have got invalidated.
+ *	 Mark any slot that points to an LSN older than the given segment
+ *	 as invalid; it requires WAL that's about to be removed.
+ *	 invalidated is set to true when any slot have got invalidated.
  *
- * NB - this runs as part of checkpoint, so avoid raising errors if possible.
+ *  Logical replication slot case:
+ *
+ *	 When xid is valid, it means that we are about to remove rows older than xid.
+ *	 Therefore we need to invalidate slots that depend on seeing those rows.
+ *	 When xid is invalid, invalidate all logical slots. This is required when the
+ *	 master wal_level is set back to replica, so existing logical slots need to
+ *	 be invalidated.
  */
 bool
-InvalidateObsoleteReplicationSlots(XLogSegNo oldestSegno)
+InvalidateObsoleteReplicationSlots(XLogSegNo oldestSegno, Oid dboid, TransactionId *xid)
 {
-	XLogRecPtr	oldestLSN;
+
+	XLogRecPtr	oldestLSN = InvalidXLogRecPtr;
 	bool		invalidated = false;
 
-	XLogSegNoOffsetToRecPtr(oldestSegno, 0, wal_segment_size, oldestLSN);
+	Assert(max_replication_slots >= 0);
+
+	if (max_replication_slots == 0)
+		return invalidated;
+
+	if (!xid)
+		XLogSegNoOffsetToRecPtr(oldestSegno, 0, wal_segment_size, oldestLSN);
 
 restart:
 	LWLockAcquire(ReplicationSlotControlLock, LW_SHARED);
@@ -1414,21 +1506,35 @@ restart:
 		if (!s->in_use)
 			continue;
 
-		if (InvalidatePossiblyObsoleteSlot(s, oldestLSN, &invalidated))
+		if (xid)
 		{
-			/* if the lock was released, start from scratch */
-			goto restart;
+			/* we are only dealing with *logical* slot conflicts */
+			if (!SlotIsLogical(s))
+				continue;
+
+			/*
+			 * not the database of interest and we don't want all the
+			 * database, skip
+			 */
+			if (s->data.database != dboid && TransactionIdIsValid(*xid))
+				continue;
 		}
+
+		if (InvalidatePossiblyObsoleteSlot(s, oldestLSN, &invalidated, xid))
+			goto restart;
 	}
+
 	LWLockRelease(ReplicationSlotControlLock);
 
 	/*
-	 * If any slots have been invalidated, recalculate the resource limits.
+	 * If any slots have been invalidated, recalculate the required xmin and
+	 * the required lsn (if appropriate).
 	 */
 	if (invalidated)
 	{
 		ReplicationSlotsComputeRequiredXmin(false);
-		ReplicationSlotsComputeRequiredLSN();
+		if (!xid)
+			ReplicationSlotsComputeRequiredLSN();
 	}
 
 	return invalidated;
diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
index 2f3c964824..015d276fd9 100644
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -319,8 +319,7 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
 		 * certain that the slot has been invalidated.  Otherwise, test
 		 * availability from restart_lsn.
 		 */
-		if (XLogRecPtrIsInvalid(slot_contents.data.restart_lsn) &&
-			!XLogRecPtrIsInvalid(slot_contents.data.invalidated_at))
+		if (ObsoleteSlotIsInvalid(slot, true))
 			walstate = WALAVAIL_REMOVED;
 		else
 			walstate = GetWALAvailability(slot_contents.data.restart_lsn);
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 75e8363e24..b686691ca2 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -1253,6 +1253,13 @@ StartLogicalReplication(StartReplicationCmd *cmd)
 
 	ReplicationSlotAcquire(cmd->slotname, true);
 
+	if (LogicalReplicationSlotIsInvalid(MyReplicationSlot))
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("cannot read from logical replication slot \"%s\"",
+						cmd->slotname),
+				 errdetail("This slot has been invalidated because it was conflicting with recovery.")));
+
 	if (XLogRecPtrIsInvalid(MyReplicationSlot->data.restart_lsn))
 		ereport(ERROR,
 				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
diff --git a/src/backend/storage/ipc/procsignal.c b/src/backend/storage/ipc/procsignal.c
index 395b2cf690..c85cb5cc18 100644
--- a/src/backend/storage/ipc/procsignal.c
+++ b/src/backend/storage/ipc/procsignal.c
@@ -673,6 +673,9 @@ procsignal_sigusr1_handler(SIGNAL_ARGS)
 	if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_SNAPSHOT))
 		RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_SNAPSHOT);
 
+	if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_LOGICALSLOT))
+		RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_LOGICALSLOT);
+
 	if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK))
 		RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK);
 
diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c
index 9f56b4e95c..c62245afc7 100644
--- a/src/backend/storage/ipc/standby.c
+++ b/src/backend/storage/ipc/standby.c
@@ -24,6 +24,7 @@
 #include "access/xlogutils.h"
 #include "miscadmin.h"
 #include "pgstat.h"
+#include "replication/slot.h"
 #include "storage/bufmgr.h"
 #include "storage/lmgr.h"
 #include "storage/proc.h"
@@ -466,6 +467,7 @@ ResolveRecoveryConflictWithVirtualXIDs(VirtualTransactionId *waitlist,
  */
 void
 ResolveRecoveryConflictWithSnapshot(TransactionId snapshotConflictHorizon,
+									bool isCatalogRel,
 									RelFileLocator locator)
 {
 	VirtualTransactionId *backends;
@@ -491,6 +493,9 @@ ResolveRecoveryConflictWithSnapshot(TransactionId snapshotConflictHorizon,
 										   PROCSIG_RECOVERY_CONFLICT_SNAPSHOT,
 										   WAIT_EVENT_RECOVERY_CONFLICT_SNAPSHOT,
 										   true);
+
+	if (wal_level >= WAL_LEVEL_LOGICAL && isCatalogRel)
+		InvalidateObsoleteReplicationSlots(InvalidXLogRecPtr, locator.dbOid, &snapshotConflictHorizon);
 }
 
 /*
@@ -499,6 +504,7 @@ ResolveRecoveryConflictWithSnapshot(TransactionId snapshotConflictHorizon,
  */
 void
 ResolveRecoveryConflictWithSnapshotFullXid(FullTransactionId snapshotConflictHorizon,
+										   bool isCatalogRel,
 										   RelFileLocator locator)
 {
 	/*
@@ -517,7 +523,9 @@ ResolveRecoveryConflictWithSnapshotFullXid(FullTransactionId snapshotConflictHor
 		TransactionId truncated;
 
 		truncated = XidFromFullTransactionId(snapshotConflictHorizon);
-		ResolveRecoveryConflictWithSnapshot(truncated, locator);
+		ResolveRecoveryConflictWithSnapshot(truncated,
+											isCatalogRel,
+											locator);
 	}
 }
 
@@ -1478,6 +1486,9 @@ get_recovery_conflict_desc(ProcSignalReason reason)
 		case PROCSIG_RECOVERY_CONFLICT_SNAPSHOT:
 			reasonDesc = _("recovery conflict on snapshot");
 			break;
+		case PROCSIG_RECOVERY_CONFLICT_LOGICALSLOT:
+			reasonDesc = _("recovery conflict on replication slot");
+			break;
 		case PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK:
 			reasonDesc = _("recovery conflict on buffer deadlock");
 			break;
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index a10ecbaf50..fb2de8542d 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -2526,6 +2526,9 @@ errdetail_recovery_conflict(void)
 		case PROCSIG_RECOVERY_CONFLICT_SNAPSHOT:
 			errdetail("User query might have needed to see row versions that must be removed.");
 			break;
+		case PROCSIG_RECOVERY_CONFLICT_LOGICALSLOT:
+			errdetail("User was using the logical slot that must be dropped.");
+			break;
 		case PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK:
 			errdetail("User transaction caused buffer deadlock with recovery.");
 			break;
@@ -3137,6 +3140,31 @@ RecoveryConflictInterrupt(ProcSignalReason reason)
 				/* Intentional fall through to session cancel */
 				/* FALLTHROUGH */
 
+			case PROCSIG_RECOVERY_CONFLICT_LOGICALSLOT:
+
+				/*
+				 * For conflicts that require a logical slot to be
+				 * invalidated, the requirement is for the signal receiver to
+				 * release the slot, so that it could be invalidated by the
+				 * signal sender. So for normal backends, the transaction
+				 * should be aborted, just like for other recovery conflicts.
+				 * But if it's walsender on standby, we don't want to go
+				 * through the following IsTransactionOrTransactionBlock()
+				 * check, so break here.
+				 */
+				if (am_cascading_walsender &&
+					reason == PROCSIG_RECOVERY_CONFLICT_LOGICALSLOT &&
+					MyReplicationSlot && SlotIsLogical(MyReplicationSlot))
+				{
+					RecoveryConflictPending = true;
+					QueryCancelPending = true;
+					InterruptPending = true;
+					break;
+				}
+
+				/* Intentional fall through to session cancel */
+				/* FALLTHROUGH */
+
 			case PROCSIG_RECOVERY_CONFLICT_DATABASE:
 				RecoveryConflictPending = true;
 				ProcDiePending = true;
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index 8872c80cdf..914b6aebc3 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -168,6 +168,58 @@ typedef struct ReplicationSlot
 #define SlotIsPhysical(slot) ((slot)->data.database == InvalidOid)
 #define SlotIsLogical(slot) ((slot)->data.database != InvalidOid)
 
+static inline bool
+ObsoleteSlotIsInvalid(ReplicationSlot *s, bool check_invalidated_at)
+{
+	if (check_invalidated_at)
+		return (!XLogRecPtrIsInvalid(s->data.invalidated_at) &&
+				XLogRecPtrIsInvalid(s->data.restart_lsn));
+	else
+		return (XLogRecPtrIsInvalid(s->data.restart_lsn));
+}
+
+static inline bool
+LogicalReplicationSlotIsInvalid(ReplicationSlot *s)
+{
+	return (!TransactionIdIsValid(s->effective_xmin) &&
+			!TransactionIdIsValid(s->data.catalog_xmin));
+}
+
+static inline bool
+LogicalReplicationSlotXidsConflict(ReplicationSlot *s, TransactionId xid)
+{
+	TransactionId slot_effective_xmin;
+	TransactionId slot_catalog_xmin;
+
+	slot_effective_xmin = s->effective_xmin;
+	slot_catalog_xmin = s->data.catalog_xmin;
+
+	return (((TransactionIdIsValid(slot_effective_xmin) && TransactionIdPrecedesOrEquals(slot_effective_xmin, xid)) ||
+			 (TransactionIdIsValid(slot_catalog_xmin) && TransactionIdPrecedesOrEquals(slot_catalog_xmin, xid))));
+}
+
+static inline bool
+SlotIsFreshEnough(ReplicationSlot *s, XLogRecPtr oldestLSN)
+{
+	return (s->data.restart_lsn >= oldestLSN);
+}
+
+static inline bool
+LogicalSlotIsNotConflicting(ReplicationSlot *s, TransactionId *xid)
+{
+	return (TransactionIdIsValid(*xid) && !LogicalReplicationSlotXidsConflict(s, *xid));
+}
+
+static inline bool
+DoNotInvalidateSlot(ReplicationSlot *s, TransactionId *xid, XLogRecPtr *oldestLSN)
+{
+	if (xid)
+		return (LogicalReplicationSlotIsInvalid(s) || LogicalSlotIsNotConflicting(s, xid));
+	else
+		return (ObsoleteSlotIsInvalid(s, false) || SlotIsFreshEnough(s, *oldestLSN));
+
+}
+
 /*
  * Shared memory control area for all of replication slots.
  */
@@ -215,7 +267,7 @@ extern void ReplicationSlotsComputeRequiredLSN(void);
 extern XLogRecPtr ReplicationSlotsComputeLogicalRestartLSN(void);
 extern bool ReplicationSlotsCountDBSlots(Oid dboid, int *nslots, int *nactive);
 extern void ReplicationSlotsDropDBSlots(Oid dboid);
-extern bool InvalidateObsoleteReplicationSlots(XLogSegNo oldestSegno);
+extern bool InvalidateObsoleteReplicationSlots(XLogSegNo oldestSegno, Oid dboid, TransactionId *xid);
 extern ReplicationSlot *SearchNamedReplicationSlot(const char *name, bool need_lock);
 extern int	ReplicationSlotIndex(ReplicationSlot *slot);
 extern bool ReplicationSlotName(int index, Name name);
@@ -227,5 +279,6 @@ extern void CheckPointReplicationSlots(void);
 
 extern void CheckSlotRequirements(void);
 extern void CheckSlotPermissions(void);
+extern void ResolveRecoveryConflictWithLogicalSlots(Oid dboid, TransactionId xid, char *reason);
 
 #endif							/* SLOT_H */
diff --git a/src/include/storage/procsignal.h b/src/include/storage/procsignal.h
index 905af2231b..2f52100b00 100644
--- a/src/include/storage/procsignal.h
+++ b/src/include/storage/procsignal.h
@@ -42,6 +42,7 @@ typedef enum
 	PROCSIG_RECOVERY_CONFLICT_TABLESPACE,
 	PROCSIG_RECOVERY_CONFLICT_LOCK,
 	PROCSIG_RECOVERY_CONFLICT_SNAPSHOT,
+	PROCSIG_RECOVERY_CONFLICT_LOGICALSLOT,
 	PROCSIG_RECOVERY_CONFLICT_BUFFERPIN,
 	PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK,
 
diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h
index 2effdea126..41f4dc372e 100644
--- a/src/include/storage/standby.h
+++ b/src/include/storage/standby.h
@@ -30,8 +30,10 @@ extern void InitRecoveryTransactionEnvironment(void);
 extern void ShutdownRecoveryTransactionEnvironment(void);
 
 extern void ResolveRecoveryConflictWithSnapshot(TransactionId snapshotConflictHorizon,
+												bool isCatalogRel,
 												RelFileLocator locator);
 extern void ResolveRecoveryConflictWithSnapshotFullXid(FullTransactionId snapshotConflictHorizon,
+													   bool isCatalogRel,
 													   RelFileLocator locator);
 extern void ResolveRecoveryConflictWithTablespace(Oid tsid);
 extern void ResolveRecoveryConflictWithDatabase(Oid dbid);
-- 
2.34.1