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| author | Amit Kapila <akapila@postgresql.org> | 2018-09-04 10:49:05 +0530 |
|---|---|---|
| committer | Amit Kapila <akapila@postgresql.org> | 2018-09-04 10:49:05 +0530 |
| commit | bf61873ae3b64e2883c1a9c7af8e5df788a7123c (patch) | |
| tree | 91305bf35c63a017136ec8c0c61526a1dc1477cc /src/test | |
| parent | 3b7a96a619f78f80b4a470a0dcde4c92b5b7141f (diff) | |
| download | postgresql-bf61873ae3b64e2883c1a9c7af8e5df788a7123c.tar.gz postgresql-bf61873ae3b64e2883c1a9c7af8e5df788a7123c.zip | |
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 562eb2c5380..9fd86256d2f 100644 --- a/src/test/regress/expected/select_parallel.out +++ b/src/test/regress/expected/select_parallel.out @@ -573,6 +573,32 @@ explain (costs off) Index Cond: (unique1 = 1) (5 rows) +-- 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 EXPLAIN (analyze, timing off, summary off, costs off) SELECT * FROM tenk1; QUERY PLAN diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql index 1d29e966076..dd9365d7c6e 100644 --- a/src/test/regress/sql/select_parallel.sql +++ b/src/test/regress/sql/select_parallel.sql @@ -204,6 +204,12 @@ set force_parallel_mode=1; explain (costs off) select stringu1::int2 from tenk1 where unique1 = 1; +-- 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 EXPLAIN (analyze, timing off, summary off, costs off) SELECT * FROM tenk1; |