From: Robert Haas <rhaas@postgresql.org>
Date: Fri, 6 Jun 2025 19:22:13 +0000 (-0400)
Subject: Look through Gather and Gather Merge nodes.
X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=2883eba2edf70b44a21ad7c1573582a1adb92a07;p=users%2Frhaas%2Fpostgres.git

Look through Gather and Gather Merge nodes.
---

diff --git a/contrib/pg_plan_advice/pgpa_join.c b/contrib/pg_plan_advice/pgpa_join.c
index d1428cc349..f0054bd0ef 100644
--- a/contrib/pg_plan_advice/pgpa_join.c
+++ b/contrib/pg_plan_advice/pgpa_join.c
@@ -154,12 +154,15 @@ pgpa_unroll_join(PlannedStmt *pstmt, Plan *plan,
 	Assert(join_unroller != NULL);
 
 	/*
-	 * We need to pass the join_unroller object down through plan nodes that
-	 * pgpa_decompose_join() regards as part of the join strategy.
-	 *
-	 * XXX. Gather and Gather Merge are going to be a problem here.
+	 * We need to pass the join_unroller object down through certain types
+	 * of plan nodes -- anything that's considered part of the join strategy,
+	 * such as Hash Join's Hash node or a Materialize node inserted on the
+	 * inner side of a nested loop as part of the join strategy -- and also
+	 * Gather and Gather Merge nodes, which can occur in a join tree but
+	 * are not themselves scans or joins.
 	 */
-	if (IsA(plan, Material) || IsA(plan, Memoize) || IsA(plan, Hash) || IsA(plan, Sort))
+	if (IsA(plan, Material) || IsA(plan, Memoize) || IsA(plan, Hash) ||
+		IsA(plan, Sort) || IsA(plan, Gather) || IsA(plan, GatherMerge))
 	{
 		*outer_join_unroller = join_unroller;
 		return;
@@ -392,6 +395,18 @@ pgpa_decompose_join(PlannedStmt *pstmt, Plan *plan,
 			elog(ERROR, "unrecognized node type: %d", (int) nodeTag(plan));
 	}
 
+	if (IsA(outerplan, Gather) || IsA(outerplan, GatherMerge))
+	{
+		outerplan = outerplan->lefttree;
+		elidedouter = pgpa_last_elided_node(pstmt, outerplan);
+	}
+
+	if (IsA(innerplan, Gather) || IsA(innerplan, GatherMerge))
+	{
+		innerplan = innerplan->lefttree;
+		elidedinner = pgpa_last_elided_node(pstmt, innerplan);
+	}
+
 	*realouter = outerplan;
 	*realinner = innerplan;
 	*elidedrealouter = elidedouter;