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Commitbabe545

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Avoid leaking memory during large-scale REASSIGN OWNED BY operations.
The various ALTER OWNER routines tend to leak memory inCurrentMemoryContext. That's not a problem when they're only calledonce per command; but in this usage where we might be touching manyobjects, it can amount to a serious memory leak. Fix that by runningeach call in a short-lived context.(DROP OWNED BY likely has a similar issue, except that you'll probablyrun out of lock table space before noticing. REASSIGN is worth fixingsince for most non-table object types, it won't take any lock.)Back-patch to all supported branches. Unfortunately, in the backbranches this helps to only a limited extent, since the sinval messagequeue bloats quite a lot in this usage before commit3aafc03,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 LelargeDiscussion:https://postgr.es/m/CAECtzeW2DAoioEGBRjR=CzHP6TdL=yosGku8qZxfX9hhtrBB0Q@mail.gmail.com
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‎src/backend/catalog/pg_shdepend.c

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@@ -65,6 +65,7 @@
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#include"storage/lmgr.h"
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#include"utils/acl.h"
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#include"utils/fmgroids.h"
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#include"utils/memutils.h"
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#include"utils/syscache.h"
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typedefenum
@@ -1497,6 +1498,8 @@ shdepReassignOwned(List *roleids, Oid newrole)
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while ((tuple=systable_getnext(scan))!=NULL)
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{
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Form_pg_shdependsdepForm= (Form_pg_shdepend)GETSTRUCT(tuple);
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MemoryContextcxt,
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oldcxt;
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/*
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* We only operate on shared objects and objects in the current
@@ -1510,6 +1513,18 @@ shdepReassignOwned(List *roleids, Oid newrole)
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if (sdepForm->deptype!=SHARED_DEPENDENCY_OWNER)
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continue;
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/*
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* The various ALTER OWNER routines tend to leak memory in
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* CurrentMemoryContext. That's not a problem when they're only
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* called once per command; but in this usage where we might be
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* touching many objects, it can amount to a serious memory leak.
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* Fix that by running each call in a short-lived context.
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*/
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cxt=AllocSetContextCreate(CurrentMemoryContext,
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"shdepReassignOwned",
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ALLOCSET_DEFAULT_SIZES);
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oldcxt=MemoryContextSwitchTo(cxt);
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/* Issue the appropriate ALTER OWNER call */
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switch (sdepForm->classid)
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{
@@ -1598,6 +1613,11 @@ shdepReassignOwned(List *roleids, Oid newrole)
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elog(ERROR,"unexpected classid %u",sdepForm->classid);
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break;
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}
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/* Clean up */
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MemoryContextSwitchTo(oldcxt);
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MemoryContextDelete(cxt);
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/* Make sure the next iteration will see my changes */
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CommandCounterIncrement();
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}

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