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MDEV-19008 Slow EXPLAIN SELECT ... WHERE col IN (const1,const2,(subquery))

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This commit is contained in:
Alexander Barkov
2019-03-21 13:43:17 +04:00
parent 482710b20c
commit f4484dfdbf
5 changed files with 49 additions and 1 deletions
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19
mysql-test/main/func_debug.result
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@ -1655,3 +1655,22 @@ Note 1105 DBUG: [1] arg=2 handler=0 (time)
Note 1105 DBUG: [2] arg=3 handler=2 (datetime)
SET SESSION debug_dbug="-d,Predicant_to_list_comparator";
SET SESSION debug_dbug="-d,Item_func_in";
#
# MDEV-19008 Slow EXPLAIN SELECT ... WHERE col IN (const1,const2,(subquery))
#
SET SESSION debug_dbug="+d,Item_subselect";
CREATE TABLE t1 (a INT);
INSERT INTO t1 VALUES (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
EXPLAIN SELECT * FROM t1 WHERE a IN (1,2,(SELECT MAX(a) FROM t1));
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 10 Using where
2 SUBQUERY t1 ALL NULL NULL NULL NULL 10
SELECT * FROM t1 WHERE a IN (1,2,(SELECT MAX(a) FROM t1));
a
1
2
9
Warnings:
Note 1105 DBUG: Item_subselect::exec (select max(`test`.`t1`.`a`) from `test`.`t1`)
DROP TABLE t1;
SET SESSION debug_dbug="-d,Item_subselect";