diff options
| author | Amit Kapila | 2018-09-04 04:36:09 +0000 |
|---|---|---|
| committer | Amit Kapila | 2018-09-04 04:58:08 +0000 |
| commit | 14e9b2a752efaa427ce1b400b9aaa5a636898a04 (patch) | |
| tree | 3738849af0fdc0f64027208cda178093ca431858 /src/test | |
| parent | 7c9e19ca9a4de6eb98582548ec6dd0d83fc5ac2d (diff) | |
Prohibit pushing subqueries containing window function calculation to
workers.
Allowing window function calculation in workers leads to inconsistent
results because if the input row ordering is not fully deterministic, the
output of window functions might vary across workers. The fix is to treat
them as parallel-restricted.
In the passing, improve the coding pattern in max_parallel_hazard_walker
so that it has a chain of mutually-exclusive if ... else if ... else if
... else if ... IsA tests.
Reported-by: Marko Tiikkaja
Bug: 15324
Author: Amit Kapila
Reviewed-by: Tom Lane
Backpatch-through: 9.6
Discussion: https://postgr.es/m/CAL9smLAnfPJCDUUG4ckX2iznj53V7VSMsYefzZieN93YxTNOcw@mail.gmail.com
Diffstat (limited to 'src/test')
| -rw-r--r-- | src/test/regress/expected/select_parallel.out | 26 | ||||
| -rw-r--r-- | src/test/regress/sql/select_parallel.sql | 6 |
2 files changed, 32 insertions, 0 deletions
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out index f1b8cd43376..13cdd3d5cca 100644 --- a/src/test/regress/expected/select_parallel.out +++ b/src/test/regress/expected/select_parallel.out @@ -958,6 +958,32 @@ select count(*) from tenk1; reset force_parallel_mode; reset role; +-- Window function calculation can't be pushed to workers. +explain (costs off, verbose) + select count(*) from tenk1 a where (unique1, two) in + (select unique1, row_number() over() from tenk1 b); + QUERY PLAN +---------------------------------------------------------------------------------------------- + Aggregate + Output: count(*) + -> Hash Semi Join + Hash Cond: ((a.unique1 = b.unique1) AND (a.two = (row_number() OVER (?)))) + -> Gather + Output: a.unique1, a.two + Workers Planned: 4 + -> Parallel Seq Scan on public.tenk1 a + Output: a.unique1, a.two + -> Hash + Output: b.unique1, (row_number() OVER (?)) + -> WindowAgg + Output: b.unique1, row_number() OVER (?) + -> Gather + Output: b.unique1 + Workers Planned: 4 + -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 b + Output: b.unique1 +(18 rows) + -- to increase the parallel query test coverage SAVEPOINT settings; SET LOCAL force_parallel_mode = 1; diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql index 7771e055ab9..3d1dffe61d2 100644 --- a/src/test/regress/sql/select_parallel.sql +++ b/src/test/regress/sql/select_parallel.sql @@ -362,6 +362,12 @@ select count(*) from tenk1; reset force_parallel_mode; reset role; +-- Window function calculation can't be pushed to workers. +explain (costs off, verbose) + select count(*) from tenk1 a where (unique1, two) in + (select unique1, row_number() over() from tenk1 b); + + -- to increase the parallel query test coverage SAVEPOINT settings; SET LOCAL force_parallel_mode = 1; |