From 8f55b9a8ba6d6543c162927c29f8d06ce1cd7372 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Sun, 1 Jul 2007 17:45:42 +0000 Subject: [PATCH] Avoid memory leakage when a series of subtransactions invoke AFTER triggers that are fired at end-of-statement (as is the normal case for foreign keys, for example). In this situation the per-subxact deferred trigger context is always empty when subtransaction exit is reached; so we could free it, but were not doing so, leading to an intratransaction leak of 8K or more per subtransaction. Per off-list example from Viatcheslav Kalinin subsequent to bug #3418 (his original bug report omitted a foreign key constraint needed to cause this leak). Back-patch to 8.2; prior versions were not using per-subxact contexts for deferred triggers, so did not have this leak. --- src/backend/commands/trigger.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c index e2dadb7a7e..3f251ad6dd 100644 --- a/src/backend/commands/trigger.c +++ b/src/backend/commands/trigger.c @@ -7,7 +7,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.214 2007/03/19 23:38:29 wieck Exp $ + * $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.215 2007/07/01 17:45:42 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -2814,6 +2814,24 @@ AfterTriggerEndSubXact(bool isCommit) afterTriggers->state_stack[my_level] = NULL; Assert(afterTriggers->query_depth == afterTriggers->depth_stack[my_level]); + /* + * It's entirely possible that the subxact created an event_cxt but + * there is not anything left in it (because all the triggers were + * fired at end-of-statement). If so, we should release the context + * to prevent memory leakage in a long sequence of subtransactions. + * We can detect whether there's anything of use in the context by + * seeing if anything was added to the global events list since + * subxact start. (This test doesn't catch every case where the + * context is deletable; for instance maybe the only additions were + * from a sub-sub-xact. But it handles the common case.) + */ + if (afterTriggers->cxt_stack[my_level] && + afterTriggers->events.tail == afterTriggers->events_stack[my_level].tail) + { + MemoryContextDelete(afterTriggers->cxt_stack[my_level]); + /* avoid double delete if abort later */ + afterTriggers->cxt_stack[my_level] = NULL; + } } else { -- 2.40.0