Fix unsafe RTE_GROUP removal in simplify_EXISTS_query When simplify_EXISTS_query removes the GROUP BY clauses from an EXISTS subquery, it previously deleted the RTE_GROUP RTE directly from the subquery's range table.
This approach is dangerous because deleting an RTE from the middle of the rtable list shifts the index of any subsequent RTE, which can silently corrupt any Var nodes in the query tree that reference those later relations. (Currently, this direct removal has not caused problems because the RTE_GROUP RTE happens to always be the last entry in the rtable list. However, relying on that is extremely fragile and seems like trouble waiting to happen.) Instead of deleting the RTE_GROUP RTE, this patch converts it in-place to be RTE_RESULT type and clears its groupexprs list. This preserves the length and indexing of the rtable list, ensuring all Var references remain intact. Reported-by: Tom Lane <[email protected]> Author: Richard Guo <[email protected]> Reviewed-by: Tom Lane <[email protected]> Discussion: https://postgr.es/m/[email protected] Backpatch-through: 18 Branch ------ REL_18_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/1c7358099cbe77bc622bc817ec4e9d919ca91fcf Modified Files -------------- src/backend/optimizer/plan/subselect.c | 34 +++++++++++++++++----------------- 1 file changed, 17 insertions(+), 17 deletions(-)
