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Fix alias matching in transformLockingClause().

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When locking a specific named relation for a FOR [KEY] UPDATE/SHARE
clause, transformLockingClause() finds the relation to lock by
scanning the rangetable for an RTE with a matching eref->aliasname.
However, it failed to account for the visibility rules of a join RTE.

If a join RTE doesn't have a user-supplied alias, it will have a
generated eref->aliasname of "unnamed_join" that is not visible as a
relation name in the parse namespace. Such an RTE needs to be skipped,
otherwise it might be found in preference to a regular base relation
with a user-supplied alias of "unnamed_join", preventing it from being
locked.

In addition, if a join RTE doesn't have a user-supplied alias, but
does have a join_using_alias, then the RTE needs to be matched using
that alias rather than the generated eref->aliasname, otherwise a
misleading "relation not found" error will be reported rather than a
"join cannot be locked" error.

Backpatch all the way, except for the second part which only goes back
to 14, where JOIN USING aliases were added.

Dean Rasheed, reviewed by Tom Lane.

Discussion: https://postgr.es/m/CAEZATCUY_KOBnqxbTSPf=7fz9HWPnZ5Xgb9SwYzZ8rFXe7nb=w@mail.gmail.com
This commit is contained in:
Dean Rasheed
2022-07-07 13:08:00 +01:00
parent d2323570ad
commit f890223bc3
3 changed files with 23 additions and 0 deletions
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9
src/backend/parser/analyze.c
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@ -2818,6 +2818,15 @@ transformLockingClause(ParseState *pstate, Query *qry, LockingClause *lc,
++i;
if (!rte->inFromCl)
continue;
/*
* A join RTE without an alias is not visible as a relation
* name and needs to be skipped (otherwise it might hide a
* base relation with the same name).
*/
if (rte->rtekind == RTE_JOIN && rte->alias == NULL)
continue;
if (strcmp(rte->eref->aliasname, thisrel->relname) == 0)
{
switch (rte->rtekind)