diff options
Diffstat (limited to 'mysql-test/main/subselect4.result')
| -rw-r--r-- | mysql-test/main/subselect4.result | 51 |
1 files changed, 50 insertions, 1 deletions
diff --git a/mysql-test/main/subselect4.result b/mysql-test/main/subselect4.result index bd9ecdc642b..783542c7dbf 100644 --- a/mysql-test/main/subselect4.result +++ b/mysql-test/main/subselect4.result @@ -2256,7 +2256,7 @@ SELECT a3 FROM t3 WHERE b2 = b1 AND b2 <= b1 ORDER BY b3 id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY t2 system NULL NULL NULL NULL 1 1 PRIMARY t1 ALL NULL NULL NULL NULL 2 Using where -3 DEPENDENT SUBQUERY t3 ALL NULL NULL NULL NULL 2 Using where +1 PRIMARY t3 ALL NULL NULL NULL NULL 2 Using where; FirstMatch(t1); Using join buffer (flat, BNL join) SELECT * FROM t1 WHERE a1 IN ( SELECT a2 FROM t2 WHERE a2 IN ( SELECT a3 FROM t3 WHERE b2 = b1 AND b2 <= b1 ORDER BY b3 @@ -2534,3 +2534,52 @@ x c1 1 drop table t1; +# +# MDEV-19134: EXISTS() slower if ORDER BY is defined +# +create table t0 (a int); +insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9); +create table t1(a int, b int); +insert into t1 select +A.a + B.a*10, A.a + B.a*10 from t0 A, t0 B; +create table t2 as select * from t1; +# This will be converted to semi-join: +explain +select * from t1 +where exists (select * from t2 where t2.a=t1.a order by t2.b); +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY t1 ALL NULL NULL NULL NULL 100 +1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 4 func 1 +2 MATERIALIZED t2 ALL NULL NULL NULL NULL 100 +# query with a non-zero constant LIMIT is converted to semi-join, too: +explain +select * from t1 +where exists (select * from t2 where t2.a=t1.a order by t2.b limit 2); +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY t1 ALL NULL NULL NULL NULL 100 +1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 4 func 1 +2 MATERIALIZED t2 ALL NULL NULL NULL NULL 100 +# Zero LIMIT should prevent the conversion (but it is not visible atm +# due to MDEV-19429) +explain +select * from t1 +where exists (select * from t2 where t2.a=t1.a order by t2.b limit 0); +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY t1 ALL NULL NULL NULL NULL 100 +1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 4 func 1 +2 MATERIALIZED t2 ALL NULL NULL NULL NULL 100 +# LIMIT+OFFSET prevents the conversion: +explain +select * from t1 +where exists (select * from t2 where t2.a=t1.a order by t2.b limit 2,3); +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY t1 ALL NULL NULL NULL NULL 100 Using where +2 DEPENDENT SUBQUERY t2 ALL NULL NULL NULL NULL 100 Using where; Using filesort +# This will be merged and converted into a semi-join: +explain +select * from t1 where t1.a in (select t2.a from t2 order by t2.b); +id select_type table type possible_keys key key_len ref rows Extra +1 PRIMARY t1 ALL NULL NULL NULL NULL 100 +1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 4 func 1 +2 MATERIALIZED t2 ALL NULL NULL NULL NULL 100 +drop table t0, t1, t2; |