From f47b33a19115f432ad80777db0d1350d23bb6cf5 Mon Sep 17 00:00:00 2001
From: Richard Guo <rguo@postgresql.org>
Date: Mon, 29 Jul 2024 11:33:18 +0900
Subject: [PATCH] Simplify create_merge_append_path for clarity
We don't currently support parameterized MergeAppend paths: there's
little use for an ordered path on the inside of a nestloop. Given
this, we can simplify create_merge_append_path by directly setting
param_info to NULL instead of calling get_appendrel_parampathinfo. We
can also simplify the Assert for child paths a little bit.
This change won't make any measurable difference in performance; it's
just for clarity's sake.
Author: Richard Guo
Reviewed-by: Alena Rybakina, Paul A Jungwirth
Discussion: https://postgr.es/m/CAMbWs4_n1bgH2nACMuGsXZct3KH6PBFS0tPdQsXdstRfyxTunQ@mail.gmail.com
---
src/backend/optimizer/util/pathnode.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index b8b1eae295..54e042a8a5 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -1423,11 +1423,16 @@ create_merge_append_path(PlannerInfo *root,
Cost input_total_cost;
ListCell *l;
+ /*
+ * We don't currently support parameterized MergeAppend paths, as
+ * explained in the comments for generate_orderedappend_paths.
+ */
+ Assert(bms_is_empty(rel->lateral_relids) && bms_is_empty(required_outer));
+
pathnode->path.pathtype = T_MergeAppend;
pathnode->path.parent = rel;
pathnode->path.pathtarget = rel->reltarget;
- pathnode->path.param_info = get_appendrel_parampathinfo(rel,
- required_outer);
+ pathnode->path.param_info = NULL;
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel;
pathnode->path.parallel_workers = 0;
@@ -1453,6 +1458,9 @@ create_merge_append_path(PlannerInfo *root,
{
Path *subpath = (Path *) lfirst(l);
+ /* All child paths should be unparameterized */
+ Assert(bms_is_empty(PATH_REQ_OUTER(subpath)));
+
pathnode->path.rows += subpath->rows;
pathnode->path.parallel_safe = pathnode->path.parallel_safe &&
subpath->parallel_safe;
@@ -1480,9 +1488,6 @@ create_merge_append_path(PlannerInfo *root,
input_startup_cost += sort_path.startup_cost;
input_total_cost += sort_path.total_cost;
}
-
- /* All child paths must have same parameterization */
- Assert(bms_equal(PATH_REQ_OUTER(subpath), required_outer));
}
/*