From 8f4b0200e15a5684f6331f94caea002370754257 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Wed, 1 Dec 2021 13:44:47 -0500 Subject: [PATCH] Avoid leaking memory during large-scale REASSIGN OWNED BY operations. The various ALTER OWNER routines tend to leak memory in CurrentMemoryContext. That's not a problem when they're only called once per command; but in this usage where we might be touching many objects, it can amount to a serious memory leak. Fix that by running each call in a short-lived context. (DROP OWNED BY likely has a similar issue, except that you'll probably run out of lock table space before noticing. REASSIGN is worth fixing since for most non-table object types, it won't take any lock.) Back-patch to all supported branches. Unfortunately, in the back branches this helps to only a limited extent, since the sinval message queue bloats quite a lot in this usage before commit 3aafc030a, consuming memory more or less comparable to what's actually leaked. Still, it's clearly a leak with a simple fix, so we might as well fix it. Justin Pryzby, per report from Guillaume Lelarge Discussion: https://postgr.es/m/CAECtzeW2DAoioEGBRjR=CzHP6TdL=yosGku8qZxfX9hhtrBB0Q@mail.gmail.com --- src/backend/catalog/pg_shdepend.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/src/backend/catalog/pg_shdepend.c b/src/backend/catalog/pg_shdepend.c index d89a9fa2bf..e9b37383ac 100644 --- a/src/backend/catalog/pg_shdepend.c +++ b/src/backend/catalog/pg_shdepend.c @@ -65,6 +65,7 @@ #include "storage/lmgr.h" #include "utils/acl.h" #include "utils/fmgroids.h" +#include "utils/memutils.h" #include "utils/syscache.h" typedef enum @@ -1549,6 +1550,8 @@ shdepReassignOwned(List *roleids, Oid newrole) while ((tuple = systable_getnext(scan)) != NULL) { Form_pg_shdepend sdepForm = (Form_pg_shdepend) GETSTRUCT(tuple); + MemoryContext cxt, + oldcxt; /* * We only operate on shared objects and objects in the current @@ -1566,6 +1569,18 @@ shdepReassignOwned(List *roleids, Oid newrole) if (sdepForm->deptype != SHARED_DEPENDENCY_OWNER) continue; + /* + * The various ALTER OWNER routines tend to leak memory in + * CurrentMemoryContext. That's not a problem when they're only + * called once per command; but in this usage where we might be + * touching many objects, it can amount to a serious memory leak. + * Fix that by running each call in a short-lived context. + */ + cxt = AllocSetContextCreate(CurrentMemoryContext, + "shdepReassignOwned", + ALLOCSET_DEFAULT_SIZES); + oldcxt = MemoryContextSwitchTo(cxt); + /* Issue the appropriate ALTER OWNER call */ switch (sdepForm->classid) { @@ -1654,6 +1669,11 @@ shdepReassignOwned(List *roleids, Oid newrole) elog(ERROR, "unexpected classid %u", sdepForm->classid); break; } + + /* Clean up */ + MemoryContextSwitchTo(oldcxt); + MemoryContextDelete(cxt); + /* Make sure the next iteration will see my changes */ CommandCounterIncrement(); }