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Reject SELECT ... GROUP BY GROUPING SETS (()) FOR UPDATE.

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This case should be disallowed, just as FOR UPDATE with a plain
GROUP BY is disallowed; FOR UPDATE only makes sense when each row
of the query result can be identified with a single table row.
However, we missed teaching CheckSelectLocking() to check
groupingSets as well as groupClause, so that it would allow
degenerate grouping sets.  That resulted in a bad plan and
a null-pointer dereference in the executor.

Looking around for other instances of the same bug, the only one
I found was in examine_simple_variable().  That'd just lead to
silly estimates, but it should be fixed too.

Per private report from Yaoguang Chen.
Back-patch to all supported branches.
This commit is contained in:
Tom Lane
2021-06-01 11:12:56 -04:00
parent d250568121
commit e5b0fffa17
4 changed files with 12 additions and 2 deletions
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2
src/backend/parser/analyze.c
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@ -2688,7 +2688,7 @@ CheckSelectLocking(Query *qry, LockClauseStrength strength)
translator: %s is a SQL row locking clause such as FOR UPDATE */
errmsg("%s is not allowed with DISTINCT clause",
LCS_asString(strength))));
if (qry->groupClause != NIL)
if (qry->groupClause != NIL || qry->groupingSets != NIL)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
/*------