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Ensure result of an aggregate's finalfunc is made read-only.

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The finalfunc might return a read-write expanded object.  If we
de-duplicate multiple call sites for the aggregate, any function(s)
receiving the aggregate result earlier could alter or destroy the
value that reaches the ones called later.  This is a brown-paper-bag
bug in commit 42b746d4c, because we actually considered the need
for read-only-ness but failed to realize that it applied to the case
with a finalfunc as well as the case without.

Per report from Justin Pryzby.  New error in HEAD,
no need for back-patch.

Discussion: https://postgr.es/m/ZDm5TuKsh3tzoEjz@telsasoft.com
This commit is contained in:
Tom Lane
2023-04-16 14:16:40 -04:00
parent 1c54b93a8c
commit 78d5952dd0
4 changed files with 96 additions and 5 deletions
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7
src/backend/executor/nodeWindowAgg.c
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@ -623,10 +623,15 @@ finalize_windowaggregate(WindowAggState *winstate,
}
else
{
Datum res;
winstate->curaggcontext = peraggstate->aggcontext;
*result = FunctionCallInvoke(fcinfo);
res = FunctionCallInvoke(fcinfo);
winstate->curaggcontext = NULL;
*isnull = fcinfo->isnull;
*result = MakeExpandedObjectReadOnly(res,
fcinfo->isnull,
peraggstate->resulttypeLen);
}
}
else