postgres_fdw: Add Assert to estimate_path_cost_size().

Etsuro Fujita · Etsuro Fujita · commit 21c9756db645 · 2025-07-06T17:15:00.000+09:00
When estimating the cost/size of a pre-sorted path for a given upper relation using local stats, this function dereferences the passed-in PgFdwPathExtraData pointer without checking that it is not NULL. But that is not a bug as the pointer is guaranteed to be non-NULL in that case; to avoid confusion, add an Assert to ensure that it is not NULL before dereferencing it. Reported-by: Ranier Vilela <ranier.vf@gmail.com> Author: Etsuro Fujita <etsuro.fujita@gmail.com> Reviewed-by: Ranier Vilela <ranier.vf@gmail.com> Discussion: https://postgr.es/m/CAEudQArgiALbV1akQpeZOgim7XP05n%3DbDP1%3DTcOYLA43nRX_vA%40mail.gmail.com
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
@@ -3507,6 +3507,13 @@ estimate_path_cost_size(PlannerInfo *root,
 			{
 				Assert(foreignrel->reloptkind == RELOPT_UPPER_REL &&
 					   fpinfo->stage == UPPERREL_GROUP_AGG);
+
+				/*
+				 * We can only get here when this function is called from
+				 * add_foreign_ordered_paths() or add_foreign_final_paths();
+				 * in which cases, the passed-in fpextra should not be NULL.
+				 */
+				Assert(fpextra);
 				adjust_foreign_grouping_path_cost(root, pathkeys,
 												  retrieved_rows, width,
 												  fpextra->limit_tuples,
