From 7f528e96c501704202b86edaf0ae115fe809ac5b Mon Sep 17 00:00:00 2001 From: Tomas Vondra Date: Wed, 7 Jun 2023 16:48:50 +0200 Subject: [PATCH] Use per-tuple context in ExecGetAllUpdatedCols Commit fc22b6623b (generated columns) replaced ExecGetUpdatedCols() with ExecGetAllUpdatedCols() in a couple places handling UPDATE (triggers and lock mode). However, ExecGetUpdatedCols() did exec_rt_fetch() while ExecGetAllUpdatedCols() also allocates memory through bms_union() without paying attention to the memory context and happened to use the long-lived ExecutorState, leaking the memory until the end of the query. The amount of leaked memory is proportional to the number of (updated) attributes, types of UPDATE triggers, and the number of processed rows (which for UPDATE ... FROM ... may be much higher than updated rows). Fixed by switching to the per-tuple context in GetAllUpdatedColumns(). This is fine for all in-core callers, but external callers may need to copy the result. But we're not aware of any such callers. Note the issue was introduced by fc22b6623b, but the macros were later renamed by f50e888990. Backpatch to 12, where the issue was introduced. Reported-by: Tomas Vondra Reviewed-by: Andres Freund, Tom Lane, Jakub Wartak Backpatch-through: 12 Discussion: https://postgr.es/m/222a3442-7f7d-246c-ed9b-a76209d19239@enterprisedb.com --- src/backend/executor/execUtils.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/src/backend/executor/execUtils.c b/src/backend/executor/execUtils.c index 4943339ebb..b74b0684b3 100644 --- a/src/backend/executor/execUtils.c +++ b/src/backend/executor/execUtils.c @@ -1348,10 +1348,25 @@ ExecGetExtraUpdatedCols(ResultRelInfo *relinfo, EState *estate) return NULL; } -/* Return columns being updated, including generated columns */ +/* + * Return columns being updated, including generated columns + * + * The bitmap is allocated in per-tuple memory context. It's up to the caller to + * copy it into a different context with the appropriate lifespan, if needed. + */ Bitmapset * ExecGetAllUpdatedCols(ResultRelInfo *relinfo, EState *estate) { - return bms_union(ExecGetUpdatedCols(relinfo, estate), - ExecGetExtraUpdatedCols(relinfo, estate)); + + Bitmapset *ret; + MemoryContext oldcxt; + + oldcxt = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate)); + + ret = bms_union(ExecGetUpdatedCols(relinfo, estate), + ExecGetExtraUpdatedCols(relinfo, estate)); + + MemoryContextSwitchTo(oldcxt); + + return ret; }