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avamingli pushed a commit to branch main
in repository https://gitbox.apache.org/repos/asf/cloudberry.git
The following commit(s) were added to refs/heads/main by this push:
new 78fef498264 Remove Upstream Assertion in Cloudberry's Parallel UNION
codes.
78fef498264 is described below
commit 78fef498264c13036626f1b414f34320748f1cc6
Author: Zhang Mingli <[email protected]>
AuthorDate: Mon Jul 14 23:04:26 2025 +0800
Remove Upstream Assertion in Cloudberry's Parallel UNION codes.
This commit addresses the scenario where paths have parallel_workers set
to 0, but contain subpaths with parallel_workers greater than 0. This
case is valid and enables our CBDB to maximize parallel execution where
feasible, enhancing overall performance in query processing.
explain(costs off) SELECT * FROM (SELECT AVG(a) as a FROM
dml_union_r UNION SELECT AVG(b) as a FROM dml_union_s) foo;
QUERY PLAN
-----------------------------------------------------------------------
Unique
Group Key: (avg(dml_union_r.a))
-> Sort
Sort Key: (avg(dml_union_r.a))
-> Append
-> Finalize Aggregate
-> Gather Motion 6:1 (slice1; segments: 6)
-> Partial Aggregate
-> Parallel Seq Scan on dml_union_r
-> Finalize Aggregate
-> Gather Motion 6:1 (slice2; segments: 6)
-> Partial Aggregate
-> Parallel Append
-> Seq Scan on
dml_union_s_1_prt_3 dml_union_s_2
-> Seq Scan on
dml_union_s_1_prt_4 dml_union_s_3
-> Seq Scan on
dml_union_s_1_prt_5 dml_union_s_4
-> Seq Scan on
dml_union_s_1_prt_6 dml_union_s_5
-> Seq Scan on
dml_union_s_1_prt_7 dml_union_s_6
-> Seq Scan on
dml_union_s_1_prt_8 dml_union_s_7
-> Seq Scan on
dml_union_s_1_prt_9 dml_union_s_8
-> Seq Scan on
dml_union_s_1_prt_10 dml_union_s_9
-> Seq Scan on
dml_union_s_1_prt_11 dml_union_s_10
-> Parallel Seq Scan on
dml_union_s_1_prt_2 dml_union_s_1
-> Parallel Seq Scan on
dml_union_s_1_prt_def dml_union_s_11
Optimizer: Postgres query optimizer
(25 rows)
Authored-by: Zhang Mingli [email protected]
---
src/backend/optimizer/prep/prepunion.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/src/backend/optimizer/prep/prepunion.c
b/src/backend/optimizer/prep/prepunion.c
index 243585fc308..ffaaea30b9c 100644
--- a/src/backend/optimizer/prep/prepunion.c
+++ b/src/backend/optimizer/prep/prepunion.c
@@ -710,7 +710,16 @@ generate_union_paths(SetOperationStmt *op, PlannerInfo
*root,
parallel_workers = Max(parallel_workers,
path->parallel_workers);
}
+#if 0
+ /*
+ * CBDB_PARALLEL:
+ * Unlike upstream, this scenario can occur when there are
paths with
+ * parallel_workers set to 0, but have subpaths with
parallel_workers > 0.
+ * This is a valid case that allows our Cloudberry
+ * to maximize parallel execution where possible.
+ */
Assert(parallel_workers > 0);
+#endif
/*
* If the use of parallel append is permitted, always request
at least
@@ -726,7 +735,12 @@ generate_union_paths(SetOperationStmt *op, PlannerInfo
*root,
parallel_workers = Min(parallel_workers,
max_parallel_workers_per_gather);
}
+#if 0
+ /*
+ * See above comments.
+ */
Assert(parallel_workers > 0);
+#endif
ppath = (Path *)
create_append_path(root, result_rel, NIL,
partial_pathlist,
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