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| author | Igor Babaev <igor@askmonty.org> | 2018-07-25 11:57:57 -0700 |
|---|---|---|
| committer | Igor Babaev <igor@askmonty.org> | 2018-07-25 11:58:19 -0700 |
| commit | aad70e9b4cdd719c3f7a559764e37ba7eea7bc3e (patch) | |
| tree | 9335217f794275a03101aeedf668044c5599a0c6 /mysql-test/r/subselect.result | |
| parent | de85355436e483902e0fff432348bc16f9ec1557 (diff) | |
| download | mariadb-git-aad70e9b4cdd719c3f7a559764e37ba7eea7bc3e.tar.gz | |
MDEV-16820 Lost 'Impossible where' from query with inexpensive subquery
This patch fixes another problem introduced by the patch for mdev-4817.
The latter changed Item_cond::fix_fields() in such a way that it could
call the virtual method is_expensive(). With the first its call
the method saves the result in Item::is_expensive_cache. For all next
calls the method returns the result from this cache. So if the item
once was determined as expensive the method always returns true.
For subqueries it's not good, because non-optimized subqueries always
is considered as expensive.
It means that the cache should be invalidated after the call of
optimize_constant_subqueries().
Diffstat (limited to 'mysql-test/r/subselect.result')
| -rw-r--r-- | mysql-test/r/subselect.result | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/mysql-test/r/subselect.result b/mysql-test/r/subselect.result index e2ed43158f1..1c75aa66287 100644 --- a/mysql-test/r/subselect.result +++ b/mysql-test/r/subselect.result @@ -7240,6 +7240,22 @@ a 5 SET @@optimizer_switch= @optimiser_switch_save; DROP TABLE t1, t2, t3; +# +# MDEV-16820: impossible where with inexpensive subquery +# +create table t1 (a int) engine=myisam; +insert into t1 values (3), (1), (7); +create table t2 (b int, index idx(b)); +insert into t2 values (2), (5), (3), (2); +explain select * from t1 where (select max(b) from t2) = 10; +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE +2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL Select tables optimized away +explain select * from t1 where (select max(b) from t2) = 10 and t1.a > 3; +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE +2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL Select tables optimized away +drop table t1,t2; End of 5.5 tests # End of 10.0 tests # |