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| author | Tomas Vondra | 2020-12-21 17:09:57 +0000 |
|---|---|---|
| committer | Tomas Vondra | 2020-12-21 17:10:20 +0000 |
| commit | f4a3c0b06250ddc8ae09b59b87cf68e9bc0d7ca1 (patch) | |
| tree | e4670149068b7cfe6abdedf560fb460239cd2c40 /src/test | |
| parent | 29f8f546767ebb4253f6dc37815e2d95fff9acd0 (diff) | |
Consider unsorted paths in generate_useful_gather_paths
generate_useful_gather_paths used to skip unsorted paths (without any
pathkeys), but that is unnecessary - the later code actually can handle
such paths just fine by adding a Sort node. This is clearly a thinko,
preventing construction of useful plans.
Backpatch to 13, where Incremental Sort was introduced.
Author: James Coleman
Reviewed-by: Tomas Vondra
Backpatch-through: 13
Discussion: https://postgr.es/m/CAAaqYe8cK3g5CfLC4w7bs=hC0mSksZC=H5M8LSchj5e5OxpTAg@mail.gmail.com
Diffstat (limited to 'src/test')
| -rw-r--r-- | src/test/regress/expected/incremental_sort.out | 13 | ||||
| -rw-r--r-- | src/test/regress/sql/incremental_sort.sql | 4 |
2 files changed, 17 insertions, 0 deletions
diff --git a/src/test/regress/expected/incremental_sort.out b/src/test/regress/expected/incremental_sort.out index 7cf2eee7c14..51471ae92de 100644 --- a/src/test/regress/expected/incremental_sort.out +++ b/src/test/regress/expected/incremental_sort.out @@ -1468,6 +1468,19 @@ explain (costs off) select * from t union select * from t order by 1,3; -> Parallel Seq Scan on t t_1 (13 rows) +-- Full sort, not just incremental sort can be pushed below a gather merge path +-- by generate_useful_gather_paths. +explain (costs off) select distinct a,b from t; + QUERY PLAN +------------------------------------------ + Unique + -> Gather Merge + Workers Planned: 2 + -> Sort + Sort Key: a, b + -> Parallel Seq Scan on t +(6 rows) + drop table t; -- Sort pushdown can't go below where expressions are part of the rel target. -- In particular this is interesting for volatile expressions which have to diff --git a/src/test/regress/sql/incremental_sort.sql b/src/test/regress/sql/incremental_sort.sql index 3ee11c394b9..cb48f200ce5 100644 --- a/src/test/regress/sql/incremental_sort.sql +++ b/src/test/regress/sql/incremental_sort.sql @@ -220,6 +220,10 @@ explain (costs off) select a,b,sum(c) from t group by 1,2 order by 1,2,3 limit 1 set enable_hashagg to off; explain (costs off) select * from t union select * from t order by 1,3; +-- Full sort, not just incremental sort can be pushed below a gather merge path +-- by generate_useful_gather_paths. +explain (costs off) select distinct a,b from t; + drop table t; -- Sort pushdown can't go below where expressions are part of the rel target. |