From e749eaf46e9b05d25592d9c83bde7fb026e9c6eb Mon Sep 17 00:00:00 2001 From: Michael Paquier Date: Thu, 21 Nov 2024 15:14:13 +0900 Subject: [PATCH] Fix memory leak in pgoutput for the WAL sender RelationSyncCache, the hash table in charge of tracking the relation schemas sent through pgoutput, was forgetting to free the TupleDesc associated to the two slots used to store the new and old tuples, causing some memory to be leaked each time a relation is invalidated when the slots of an existing relation entry are cleaned up. This is rather hard to notice as the bloat is pretty minimal, but a long-running WAL sender would be in trouble over time depending on the workload. sysbench has proved to be pretty good at showing the problem, coupled with some memory monitoring of the WAL sender. Issue introduced in 52e4f0cd472d, that has added row filters for tables logically replicated. Author: Boyu Yang Reviewed-by: Michael Paquier, Hou Zhijie Discussion: https://postgr.es/m/DM3PR84MB3442E14B340E553313B5C816E3252@DM3PR84MB3442.NAMPRD84.PROD.OUTLOOK.COM Backpatch-through: 15 --- src/backend/replication/pgoutput/pgoutput.c | 24 +++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/src/backend/replication/pgoutput/pgoutput.c b/src/backend/replication/pgoutput/pgoutput.c index c57c5ed8de9..bb8f3ea702f 100644 --- a/src/backend/replication/pgoutput/pgoutput.c +++ b/src/backend/replication/pgoutput/pgoutput.c @@ -2046,10 +2046,34 @@ get_rel_sync_entry(PGOutputData *data, Relation relation) * Tuple slots cleanups. (Will be rebuilt later if needed). */ if (entry->old_slot) + { + TupleDesc desc = entry->old_slot->tts_tupleDescriptor; + + Assert(desc->tdrefcount == -1); + ExecDropSingleTupleTableSlot(entry->old_slot); + + /* + * ExecDropSingleTupleTableSlot() would not free the TupleDesc, so + * do it now to avoid any leaks. + */ + FreeTupleDesc(desc); + } if (entry->new_slot) + { + TupleDesc desc = entry->new_slot->tts_tupleDescriptor; + + Assert(desc->tdrefcount == -1); + ExecDropSingleTupleTableSlot(entry->new_slot); + /* + * ExecDropSingleTupleTableSlot() would not free the TupleDesc, so + * do it now to avoid any leaks. + */ + FreeTupleDesc(desc); + } + entry->old_slot = NULL; entry->new_slot = NULL;