1 files changed, 33 insertions, 6 deletions

diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index bb09c40..1f9d0ed 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -1321,6 +1321,11 @@ InvalidatePossiblyObsoleteSlot(ReplicationSlotInvalidationCause cause,
 {
 	int			last_signaled_pid = 0;
 	bool		released_lock = false;
+	bool		terminated = false;
+	TransactionId initial_effective_xmin = InvalidTransactionId;
+	TransactionId initial_catalog_effective_xmin = InvalidTransactionId;
+	XLogRecPtr	initial_restart_lsn = InvalidXLogRecPtr;
+	ReplicationSlotInvalidationCause conflict_prev PG_USED_FOR_ASSERTS_ONLY = RS_INVAL_NONE;
 
 	for (;;)
 	{
@@ -1355,11 +1360,24 @@ InvalidatePossiblyObsoleteSlot(ReplicationSlotInvalidationCause cause,
 		 */
 		if (s->data.invalidated == RS_INVAL_NONE)
 		{
+			/*
+			 * The slot's mutex will be released soon, and it is possible that
+			 * those values change since the process holding the slot has been
+			 * terminated (if any), so record them here to ensure that we
+			 * would report the correct conflict cause.
+			 */
+			if (!terminated)
+			{
+				initial_restart_lsn = s->data.restart_lsn;
+				initial_effective_xmin = s->effective_xmin;
+				initial_catalog_effective_xmin = s->effective_catalog_xmin;
+			}
+
 			switch (cause)
 			{
 				case RS_INVAL_WAL_REMOVED:
-					if (s->data.restart_lsn != InvalidXLogRecPtr &&
-						s->data.restart_lsn < oldestLSN)
+					if (initial_restart_lsn != InvalidXLogRecPtr &&
+						initial_restart_lsn < oldestLSN)
 						conflict = cause;
 					break;
 				case RS_INVAL_HORIZON:
@@ -1368,12 +1386,12 @@ InvalidatePossiblyObsoleteSlot(ReplicationSlotInvalidationCause cause,
 					/* invalid DB oid signals a shared relation */
 					if (dboid != InvalidOid && dboid != s->data.database)
 						break;
-					if (TransactionIdIsValid(s->effective_xmin) &&
-						TransactionIdPrecedesOrEquals(s->effective_xmin,
+					if (TransactionIdIsValid(initial_effective_xmin) &&
+						TransactionIdPrecedesOrEquals(initial_effective_xmin,
 													  snapshotConflictHorizon))
 						conflict = cause;
-					else if (TransactionIdIsValid(s->effective_catalog_xmin) &&
-							 TransactionIdPrecedesOrEquals(s->effective_catalog_xmin,
+					else if (TransactionIdIsValid(initial_catalog_effective_xmin) &&
+							 TransactionIdPrecedesOrEquals(initial_catalog_effective_xmin,
 														   snapshotConflictHorizon))
 						conflict = cause;
 					break;
@@ -1386,6 +1404,13 @@ InvalidatePossiblyObsoleteSlot(ReplicationSlotInvalidationCause cause,
 			}
 		}
 
+		/*
+		 * The conflict cause recorded previously should not change while the
+		 * process owning the slot (if any) has been terminated.
+		 */
+		Assert(!(conflict_prev != RS_INVAL_NONE && terminated &&
+				 conflict_prev != conflict));
+
 		/* if there's no conflict, we're done */
 		if (conflict == RS_INVAL_NONE)
 		{
@@ -1460,6 +1485,8 @@ InvalidatePossiblyObsoleteSlot(ReplicationSlotInvalidationCause cause,
 					(void) kill(active_pid, SIGTERM);
 
 				last_signaled_pid = active_pid;
+				terminated = true;
+				conflict_prev = conflict;
 			}
 
 			/* Wait until the slot is released. */