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Remove the RTE_GROUP RTE if we drop the groupClause

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For an EXISTS subquery, the only thing that matters is whether it
returns zero or more than zero rows.  Therefore, we remove certain SQL
features that won't affect that, among them the GROUP BY clauses.

After we drop the groupClause, we'd better remove the RTE_GROUP RTE
and clear the hasGroupRTE flag, as they depend on the groupClause.
Failing to do so could result in a bogus RTE_GROUP entry in the parent
query, leading to an assertion failure on the hasGroupRTE flag.

Reported-by: David Rowley
Author: Richard Guo
Discussion: https://postgr.es/m/CAApHDvp2_yht8uPLyWO-kVGWZhYvx5zjGfSrg4fBQ9fsC13V0g@mail.gmail.com
This commit is contained in:
Richard Guo
2024-10-25 09:52:34 +09:00
parent d32d146399
commit ffe12d1d22
3 changed files with 47 additions and 0 deletions
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24
src/backend/optimizer/plan/subselect.c
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@ -1539,6 +1539,8 @@ convert_EXISTS_sublink_to_join(PlannerInfo *root, SubLink *sublink,
static bool
simplify_EXISTS_query(PlannerInfo *root, Query *query)
{
ListCell *lc;
/*
* We don't try to simplify at all if the query uses set operations,
* aggregates, grouping sets, SRFs, modifying CTEs, HAVING, OFFSET, or FOR
@ -1607,6 +1609,28 @@ simplify_EXISTS_query(PlannerInfo *root, Query *query)
query->sortClause = NIL;
query->hasDistinctOn = false;
/*
* Since we have thrown away the GROUP BY clauses, we'd better remove the
* RTE_GROUP RTE and clear the hasGroupRTE flag.
*/
foreach(lc, query->rtable)
{
RangeTblEntry *rte = lfirst_node(RangeTblEntry, lc);
/*
* Remove the RTE_GROUP RTE and clear the hasGroupRTE flag. (Since
* we'll exit the foreach loop immediately, we don't bother with
* foreach_delete_current.)
*/
if (rte->rtekind == RTE_GROUP)
{
Assert(query->hasGroupRTE);
query->rtable = list_delete_cell(query->rtable, lc);
query->hasGroupRTE = false;
break;
}
}
return true;
}