v2-0002-Avoid-creating-duplicate-ordered-append-paths.patch
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Filename: v2-0002-Avoid-creating-duplicate-ordered-append-paths.patch
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Part: 1
From a41f31d1e5341e93f41d7c467c32a20c2e2d958e Mon Sep 17 00:00:00 2001 From: Richard Guo <guofenglinux@gmail.com> Date: Tue, 4 Nov 2025 16:01:41 +0900 Subject: [PATCH v2 2/2] Avoid creating duplicate ordered append paths In generate_orderedappend_paths(), the function does not handle the case where the paths in total_subpaths and fractional_subpaths are identical. This situation is not uncommon, and as a result, it may generate two exactly identical ordered append paths. Fix by checking whether total_subpaths and fractional_subpaths contain the same paths, and skipping creation of the ordered append path for the fractional case when they are identical. --- src/backend/optimizer/path/allpaths.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c index 41233b98373..4c43fd0b19b 100644 --- a/src/backend/optimizer/path/allpaths.c +++ b/src/backend/optimizer/path/allpaths.c @@ -1877,6 +1877,7 @@ generate_orderedappend_paths(PlannerInfo *root, RelOptInfo *rel, List *total_subpaths = NIL; List *fractional_subpaths = NIL; bool startup_neq_total = false; + bool fraction_neq_total = false; bool match_partition_order; bool match_partition_order_desc; int end_index; @@ -2005,15 +2006,21 @@ generate_orderedappend_paths(PlannerInfo *root, RelOptInfo *rel, * XXX We might consider partially sorted paths too (with an * incremental sort on top). But we'd have to build all the * incremental paths, do the costing etc. + * + * Also, notice whether we actually have different paths for + * the "fractional" and "total" cases. This helps avoid + * generating two identical ordered append paths. */ - if (!cheapest_fractional) + if (cheapest_fractional == NULL) cheapest_fractional = cheapest_total; + else if (cheapest_fractional != cheapest_total) + fraction_neq_total = true; } /* * Notice whether we actually have different paths for the - * "cheapest" and "total" cases; frequently there will be no point - * in two create_merge_append_path() calls. + * "cheapest" and "total" cases. This helps avoid generating two + * identical ordered append paths. */ if (cheapest_startup != cheapest_total) startup_neq_total = true; @@ -2084,7 +2091,7 @@ generate_orderedappend_paths(PlannerInfo *root, RelOptInfo *rel, false, -1)); - if (fractional_subpaths) + if (fractional_subpaths && fraction_neq_total) add_path(rel, (Path *) create_append_path(root, rel, fractional_subpaths, @@ -2110,7 +2117,7 @@ generate_orderedappend_paths(PlannerInfo *root, RelOptInfo *rel, pathkeys, NULL)); - if (fractional_subpaths) + if (fractional_subpaths && fraction_neq_total) add_path(rel, (Path *) create_merge_append_path(root, rel, fractional_subpaths, -- 2.39.5 (Apple Git-154)