From fec187dc3ca2b684d31e4cb0445f392d9c909f85 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
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 6964d439ef7..05fe44042ec 100644
--- a/src/backend/catalog/pg_shdepend.c
+++ b/src/backend/catalog/pg_shdepend.c
@@ -64,6 +64,7 @@
#include "miscadmin.h"
#include "utils/acl.h"
#include "utils/fmgroids.h"
+#include "utils/memutils.h"
#include "utils/syscache.h"
#include "utils/tqual.h"
@@ -1364,6 +1365,8 @@ 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
@@ -1381,6 +1384,18 @@ 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)
{
@@ -1469,6 +1484,11 @@ 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();
}
--
2.39.5