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MDEV-19429: Wrong query result with EXISTS and LIMIT 0

Check EXISTS LIMIT before rewriting.
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Oleksandr Byelkin
Oleksandr Byelkin committed Jul 17, 2019
1 parent cc86a0b commit f90040fd9ccb99cb4541d181a7052c37dc38decb
@@ -1288,7 +1288,7 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
3 DEPENDENT SUBQUERY t3 ALL NULL NULL NULL NULL 2 100.00 Using where
Warnings:
Note 1276 Field or reference 't.a' of SELECT #3 was resolved in SELECT #1
Note 1003 select `test`.`t1`.`a` AS `a` from `test`.`t1` where <expr_cache><`test`.`t1`.`a`>(exists(select 28 from `test`.`t3` where ('j' < `test`.`t1`.`a`)))
Note 1003 select `test`.`t1`.`a` AS `a` from `test`.`t1` where <expr_cache><`test`.`t1`.`a`>(exists(select 28 from `test`.`t3` where ('j' < `test`.`t1`.`a`) limit 1))
SELECT * FROM (SELECT * FROM t1) AS t
WHERE EXISTS (SELECT t2.a FROM t3 RIGHT JOIN t2 ON (t3.a = t2.a)
WHERE t2.b < t.a);
@@ -341,7 +341,7 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
2 DEPENDENT SUBQUERY t7 eq_ref PRIMARY PRIMARY 4 test.t6.clinic_uq 1 100.00 Using index
Warnings:
Note 1276 Field or reference 'test.t6.clinic_uq' of SELECT #2 was resolved in SELECT #1
Note 1003 select `test`.`t6`.`patient_uq` AS `patient_uq`,`test`.`t6`.`clinic_uq` AS `clinic_uq` from `test`.`t6` where <expr_cache><`test`.`t6`.`clinic_uq`>(exists(select 1 from `test`.`t7` where (`test`.`t7`.`uq` = `test`.`t6`.`clinic_uq`)))
Note 1003 select `test`.`t6`.`patient_uq` AS `patient_uq`,`test`.`t6`.`clinic_uq` AS `clinic_uq` from `test`.`t6` where <expr_cache><`test`.`t6`.`clinic_uq`>(exists(select 1 from `test`.`t7` where (`test`.`t7`.`uq` = `test`.`t6`.`clinic_uq`) limit 1))
select * from t1 where a= (select a from t2,t4 where t2.b=t4.b);
ERROR 23000: Column 'a' in field list is ambiguous
drop table t1,t2,t3;
@@ -1887,7 +1887,7 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
2 DEPENDENT SUBQUERY t1 eq_ref PRIMARY PRIMARY 4 test.tt.id 1 100.00 Using where; Using index
Warnings:
Note 1276 Field or reference 'test.tt.id' of SELECT #2 was resolved in SELECT #1
Note 1003 select `test`.`tt`.`id` AS `id`,`test`.`tt`.`text` AS `text` from `test`.`t1` `tt` where (not(<expr_cache><`test`.`tt`.`id`>(exists(select `test`.`t1`.`id` from `test`.`t1` where ((`test`.`t1`.`id` < 8) and (`test`.`t1`.`id` = `test`.`tt`.`id`)) having (`test`.`t1`.`id` is not null)))))
Note 1003 select `test`.`tt`.`id` AS `id`,`test`.`tt`.`text` AS `text` from `test`.`t1` `tt` where (not(<expr_cache><`test`.`tt`.`id`>(exists(select `test`.`t1`.`id` from `test`.`t1` where ((`test`.`t1`.`id` < 8) and (`test`.`t1`.`id` = `test`.`tt`.`id`)) having (`test`.`t1`.`id` is not null) limit 1))))
insert into t1 (id, text) values (1000, 'text1000'), (1001, 'text1001');
create table t2 (id int not null, text varchar(20) not null default '', primary key (id));
insert into t2 (id, text) values (1, 'text1'), (2, 'text2'), (3, 'text3'), (4, 'text4'), (5, 'text5'), (6, 'text6'), (7, 'text7'), (8, 'text8'), (9, 'text9'), (10, 'text10'), (11, 'text1'), (12, 'text2'), (13, 'text3'), (14, 'text4'), (15, 'text5'), (16, 'text6'), (17, 'text7'), (18, 'text8'), (19, 'text9'), (20, 'text10'),(21, 'text1'), (22, 'text2'), (23, 'text3'), (24, 'text4'), (25, 'text5'), (26, 'text6'), (27, 'text7'), (28, 'text8'), (29, 'text9'), (30, 'text10'), (31, 'text1'), (32, 'text2'), (33, 'text3'), (34, 'text4'), (35, 'text5'), (36, 'text6'), (37, 'text7'), (38, 'text8'), (39, 'text9'), (40, 'text10'), (41, 'text1'), (42, 'text2'), (43, 'text3'), (44, 'text4'), (45, 'text5'), (46, 'text6'), (47, 'text7'), (48, 'text8'), (49, 'text9'), (50, 'text10');
@@ -2423,7 +2423,7 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
2 DEPENDENT SUBQUERY t1 ALL NULL NULL NULL NULL 2 100.00 Using where
Warnings:
Note 1276 Field or reference 'test.up.a' of SELECT #2 was resolved in SELECT #1
Note 1003 select `test`.`up`.`a` AS `a`,`test`.`up`.`b` AS `b` from `test`.`t1` `up` where <expr_cache><`test`.`up`.`a`>(exists(select 1 from `test`.`t1` where (`test`.`t1`.`a` = `test`.`up`.`a`)))
Note 1003 select `test`.`up`.`a` AS `a`,`test`.`up`.`b` AS `b` from `test`.`t1` `up` where <expr_cache><`test`.`up`.`a`>(exists(select 1 from `test`.`t1` where (`test`.`t1`.`a` = `test`.`up`.`a`) limit 1))
drop table t1;
CREATE TABLE t1 (t1_a int);
INSERT INTO t1 VALUES (1);
@@ -4432,7 +4432,7 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
2 DEPENDENT SUBQUERY t2 ALL NULL NULL NULL NULL 2 100.00 Using where
Warnings:
Note 1276 Field or reference 'test.t1.a' of SELECT #2 was resolved in SELECT #1
Note 1003 select 2 AS `2` from `test`.`t1` where <expr_cache><`test`.`t1`.`a`>(exists(select 1 from `test`.`t2` where (`test`.`t1`.`a` = `test`.`t2`.`a`)))
Note 1003 select 2 AS `2` from `test`.`t1` where <expr_cache><`test`.`t1`.`a`>(exists(select 1 from `test`.`t2` where (`test`.`t1`.`a` = `test`.`t2`.`a`) limit 1))
EXPLAIN EXTENDED
SELECT 2 FROM t1 WHERE EXISTS ((SELECT 1 FROM t2 WHERE t1.a=t2.a) UNION
(SELECT 1 FROM t2 WHERE t1.a = t2.a));
@@ -4444,7 +4444,7 @@ NULL UNION RESULT <union2,3> ALL NULL NULL NULL NULL NULL NULL
Warnings:
Note 1276 Field or reference 'test.t1.a' of SELECT #2 was resolved in SELECT #1
Note 1276 Field or reference 'test.t1.a' of SELECT #3 was resolved in SELECT #1
Note 1003 select 2 AS `2` from `test`.`t1` where <expr_cache><`test`.`t1`.`a`>(exists((select 1 from `test`.`t2` where (`test`.`t1`.`a` = `test`.`t2`.`a`)) union (select 1 from `test`.`t2` where (`test`.`t1`.`a` = `test`.`t2`.`a`))))
Note 1003 select 2 AS `2` from `test`.`t1` where <expr_cache><`test`.`t1`.`a`>(exists((select 1 from `test`.`t2` where (`test`.`t1`.`a` = `test`.`t2`.`a`)) union (select 1 from `test`.`t2` where (`test`.`t1`.`a` = `test`.`t2`.`a`)) limit 1))
DROP TABLE t1,t2;
create table t0(a int);
insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
@@ -7187,4 +7187,35 @@ 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;
#
# MDEV-19429: Wrong query result with EXISTS and LIMIT 0
#
create table t10 (a int);
insert into t10 values (1),(2),(3);
create table t12 (a int);
insert into t12 values (1),(2),(3);
select * from t10 where exists (select * from t12 order by a limit 0);
a
explain select * from t10 where exists (select * from t12 order by a limit 0);
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 Zero limit
prepare stmt1 from "select * from t10 where exists (select * from t12 order by a limit ?)";
set @l=1;
execute stmt1 using @l;
a
1
2
3
set @l=2;
execute stmt1 using @l;
a
1
2
3
set @l=0;
execute stmt1 using @l;
a
deallocate prepare stmt1;
drop table t10, t12;
End of 5.5 tests
@@ -2219,7 +2219,7 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
3 MATERIALIZED t3 ALL NULL NULL NULL NULL 8 100.00
Warnings:
Note 1276 Field or reference 'test.t1.f1' of SELECT #2 was resolved in SELECT #1
Note 1003 select `test`.`t1`.`f1` AS `f1` from `test`.`t1` where <expr_cache><`test`.`t1`.`f1`>(exists(select 1 from `test`.`t2` semi join (`test`.`t3`) join `test`.`t3` where ((`test`.`t3`.`i3` = `test`.`t2`.`i2`) and (`test`.`t1`.`f1` = `test`.`t3`.`f3`))))
Note 1003 select `test`.`t1`.`f1` AS `f1` from `test`.`t1` where <expr_cache><`test`.`t1`.`f1`>(exists(select 1 from `test`.`t2` semi join (`test`.`t3`) join `test`.`t3` where ((`test`.`t3`.`i3` = `test`.`t2`.`i2`) and (`test`.`t1`.`f1` = `test`.`t3`.`f3`)) limit 1))
# this checks the result set above
set @save_optimizer_switch= @@optimizer_switch;
set optimizer_switch= 'materialization=off,semijoin=off';
@@ -348,7 +348,7 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
2 DEPENDENT SUBQUERY t7 eq_ref PRIMARY PRIMARY 4 test.t6.clinic_uq 1 100.00 Using index
Warnings:
Note 1276 Field or reference 'test.t6.clinic_uq' of SELECT #2 was resolved in SELECT #1
Note 1003 select `test`.`t6`.`patient_uq` AS `patient_uq`,`test`.`t6`.`clinic_uq` AS `clinic_uq` from `test`.`t6` where <expr_cache><`test`.`t6`.`clinic_uq`>(exists(select 1 from `test`.`t7` where (`test`.`t7`.`uq` = `test`.`t6`.`clinic_uq`)))
Note 1003 select `test`.`t6`.`patient_uq` AS `patient_uq`,`test`.`t6`.`clinic_uq` AS `clinic_uq` from `test`.`t6` where <expr_cache><`test`.`t6`.`clinic_uq`>(exists(select 1 from `test`.`t7` where (`test`.`t7`.`uq` = `test`.`t6`.`clinic_uq`) limit 1))
select * from t1 where a= (select a from t2,t4 where t2.b=t4.b);
ERROR 23000: Column 'a' in field list is ambiguous
drop table t1,t2,t3;
@@ -1894,7 +1894,7 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
2 DEPENDENT SUBQUERY t1 eq_ref PRIMARY PRIMARY 4 test.tt.id 1 100.00 Using where; Using index
Warnings:
Note 1276 Field or reference 'test.tt.id' of SELECT #2 was resolved in SELECT #1
Note 1003 select `test`.`tt`.`id` AS `id`,`test`.`tt`.`text` AS `text` from `test`.`t1` `tt` where (not(<expr_cache><`test`.`tt`.`id`>(exists(select `test`.`t1`.`id` from `test`.`t1` where ((`test`.`t1`.`id` < 8) and (`test`.`t1`.`id` = `test`.`tt`.`id`)) having (`test`.`t1`.`id` is not null)))))
Note 1003 select `test`.`tt`.`id` AS `id`,`test`.`tt`.`text` AS `text` from `test`.`t1` `tt` where (not(<expr_cache><`test`.`tt`.`id`>(exists(select `test`.`t1`.`id` from `test`.`t1` where ((`test`.`t1`.`id` < 8) and (`test`.`t1`.`id` = `test`.`tt`.`id`)) having (`test`.`t1`.`id` is not null) limit 1))))
insert into t1 (id, text) values (1000, 'text1000'), (1001, 'text1001');
create table t2 (id int not null, text varchar(20) not null default '', primary key (id));
insert into t2 (id, text) values (1, 'text1'), (2, 'text2'), (3, 'text3'), (4, 'text4'), (5, 'text5'), (6, 'text6'), (7, 'text7'), (8, 'text8'), (9, 'text9'), (10, 'text10'), (11, 'text1'), (12, 'text2'), (13, 'text3'), (14, 'text4'), (15, 'text5'), (16, 'text6'), (17, 'text7'), (18, 'text8'), (19, 'text9'), (20, 'text10'),(21, 'text1'), (22, 'text2'), (23, 'text3'), (24, 'text4'), (25, 'text5'), (26, 'text6'), (27, 'text7'), (28, 'text8'), (29, 'text9'), (30, 'text10'), (31, 'text1'), (32, 'text2'), (33, 'text3'), (34, 'text4'), (35, 'text5'), (36, 'text6'), (37, 'text7'), (38, 'text8'), (39, 'text9'), (40, 'text10'), (41, 'text1'), (42, 'text2'), (43, 'text3'), (44, 'text4'), (45, 'text5'), (46, 'text6'), (47, 'text7'), (48, 'text8'), (49, 'text9'), (50, 'text10');
@@ -2430,7 +2430,7 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
2 DEPENDENT SUBQUERY t1 ALL NULL NULL NULL NULL 2 100.00 Using where
Warnings:
Note 1276 Field or reference 'test.up.a' of SELECT #2 was resolved in SELECT #1
Note 1003 select `test`.`up`.`a` AS `a`,`test`.`up`.`b` AS `b` from `test`.`t1` `up` where <expr_cache><`test`.`up`.`a`>(exists(select 1 from `test`.`t1` where (`test`.`t1`.`a` = `test`.`up`.`a`)))
Note 1003 select `test`.`up`.`a` AS `a`,`test`.`up`.`b` AS `b` from `test`.`t1` `up` where <expr_cache><`test`.`up`.`a`>(exists(select 1 from `test`.`t1` where (`test`.`t1`.`a` = `test`.`up`.`a`) limit 1))
drop table t1;
CREATE TABLE t1 (t1_a int);
INSERT INTO t1 VALUES (1);
@@ -4436,7 +4436,7 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
2 DEPENDENT SUBQUERY t2 ALL NULL NULL NULL NULL 2 100.00 Using where
Warnings:
Note 1276 Field or reference 'test.t1.a' of SELECT #2 was resolved in SELECT #1
Note 1003 select 2 AS `2` from `test`.`t1` where <expr_cache><`test`.`t1`.`a`>(exists(select 1 from `test`.`t2` where (`test`.`t1`.`a` = `test`.`t2`.`a`)))
Note 1003 select 2 AS `2` from `test`.`t1` where <expr_cache><`test`.`t1`.`a`>(exists(select 1 from `test`.`t2` where (`test`.`t1`.`a` = `test`.`t2`.`a`) limit 1))
EXPLAIN EXTENDED
SELECT 2 FROM t1 WHERE EXISTS ((SELECT 1 FROM t2 WHERE t1.a=t2.a) UNION
(SELECT 1 FROM t2 WHERE t1.a = t2.a));
@@ -4448,7 +4448,7 @@ NULL UNION RESULT <union2,3> ALL NULL NULL NULL NULL NULL NULL
Warnings:
Note 1276 Field or reference 'test.t1.a' of SELECT #2 was resolved in SELECT #1
Note 1276 Field or reference 'test.t1.a' of SELECT #3 was resolved in SELECT #1
Note 1003 select 2 AS `2` from `test`.`t1` where <expr_cache><`test`.`t1`.`a`>(exists((select 1 from `test`.`t2` where (`test`.`t1`.`a` = `test`.`t2`.`a`)) union (select 1 from `test`.`t2` where (`test`.`t1`.`a` = `test`.`t2`.`a`))))
Note 1003 select 2 AS `2` from `test`.`t1` where <expr_cache><`test`.`t1`.`a`>(exists((select 1 from `test`.`t2` where (`test`.`t1`.`a` = `test`.`t2`.`a`)) union (select 1 from `test`.`t2` where (`test`.`t1`.`a` = `test`.`t2`.`a`)) limit 1))
DROP TABLE t1,t2;
create table t0(a int);
insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
@@ -7184,6 +7184,37 @@ 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;
#
# MDEV-19429: Wrong query result with EXISTS and LIMIT 0
#
create table t10 (a int);
insert into t10 values (1),(2),(3);
create table t12 (a int);
insert into t12 values (1),(2),(3);
select * from t10 where exists (select * from t12 order by a limit 0);
a
explain select * from t10 where exists (select * from t12 order by a limit 0);
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 Zero limit
prepare stmt1 from "select * from t10 where exists (select * from t12 order by a limit ?)";
set @l=1;
execute stmt1 using @l;
a
1
2
3
set @l=2;
execute stmt1 using @l;
a
1
2
3
set @l=0;
execute stmt1 using @l;
a
deallocate prepare stmt1;
drop table t10, t12;
End of 5.5 tests
set optimizer_switch=default;
select @@optimizer_switch like '%materialization=on%';
@@ -344,7 +344,7 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
2 DEPENDENT SUBQUERY t7 eq_ref PRIMARY PRIMARY 4 test.t6.clinic_uq 1 100.00 Using index
Warnings:
Note 1276 Field or reference 'test.t6.clinic_uq' of SELECT #2 was resolved in SELECT #1
Note 1003 select `test`.`t6`.`patient_uq` AS `patient_uq`,`test`.`t6`.`clinic_uq` AS `clinic_uq` from `test`.`t6` where exists(select 1 from `test`.`t7` where (`test`.`t7`.`uq` = `test`.`t6`.`clinic_uq`))
Note 1003 select `test`.`t6`.`patient_uq` AS `patient_uq`,`test`.`t6`.`clinic_uq` AS `clinic_uq` from `test`.`t6` where exists(select 1 from `test`.`t7` where (`test`.`t7`.`uq` = `test`.`t6`.`clinic_uq`) limit 1)
select * from t1 where a= (select a from t2,t4 where t2.b=t4.b);
ERROR 23000: Column 'a' in field list is ambiguous
drop table t1,t2,t3;
@@ -1890,7 +1890,7 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
2 DEPENDENT SUBQUERY t1 eq_ref PRIMARY PRIMARY 4 test.tt.id 1 100.00 Using where; Using index
Warnings:
Note 1276 Field or reference 'test.tt.id' of SELECT #2 was resolved in SELECT #1
Note 1003 select `test`.`tt`.`id` AS `id`,`test`.`tt`.`text` AS `text` from `test`.`t1` `tt` where (not(exists(select `test`.`t1`.`id` from `test`.`t1` where ((`test`.`t1`.`id` < 8) and (`test`.`t1`.`id` = `test`.`tt`.`id`)) having (`test`.`t1`.`id` is not null))))
Note 1003 select `test`.`tt`.`id` AS `id`,`test`.`tt`.`text` AS `text` from `test`.`t1` `tt` where (not(exists(select `test`.`t1`.`id` from `test`.`t1` where ((`test`.`t1`.`id` < 8) and (`test`.`t1`.`id` = `test`.`tt`.`id`)) having (`test`.`t1`.`id` is not null) limit 1)))
insert into t1 (id, text) values (1000, 'text1000'), (1001, 'text1001');
create table t2 (id int not null, text varchar(20) not null default '', primary key (id));
insert into t2 (id, text) values (1, 'text1'), (2, 'text2'), (3, 'text3'), (4, 'text4'), (5, 'text5'), (6, 'text6'), (7, 'text7'), (8, 'text8'), (9, 'text9'), (10, 'text10'), (11, 'text1'), (12, 'text2'), (13, 'text3'), (14, 'text4'), (15, 'text5'), (16, 'text6'), (17, 'text7'), (18, 'text8'), (19, 'text9'), (20, 'text10'),(21, 'text1'), (22, 'text2'), (23, 'text3'), (24, 'text4'), (25, 'text5'), (26, 'text6'), (27, 'text7'), (28, 'text8'), (29, 'text9'), (30, 'text10'), (31, 'text1'), (32, 'text2'), (33, 'text3'), (34, 'text4'), (35, 'text5'), (36, 'text6'), (37, 'text7'), (38, 'text8'), (39, 'text9'), (40, 'text10'), (41, 'text1'), (42, 'text2'), (43, 'text3'), (44, 'text4'), (45, 'text5'), (46, 'text6'), (47, 'text7'), (48, 'text8'), (49, 'text9'), (50, 'text10');
@@ -2426,7 +2426,7 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
2 DEPENDENT SUBQUERY t1 ALL NULL NULL NULL NULL 2 100.00 Using where
Warnings:
Note 1276 Field or reference 'test.up.a' of SELECT #2 was resolved in SELECT #1
Note 1003 select `test`.`up`.`a` AS `a`,`test`.`up`.`b` AS `b` from `test`.`t1` `up` where exists(select 1 from `test`.`t1` where (`test`.`t1`.`a` = `test`.`up`.`a`))
Note 1003 select `test`.`up`.`a` AS `a`,`test`.`up`.`b` AS `b` from `test`.`t1` `up` where exists(select 1 from `test`.`t1` where (`test`.`t1`.`a` = `test`.`up`.`a`) limit 1)
drop table t1;
CREATE TABLE t1 (t1_a int);
INSERT INTO t1 VALUES (1);
@@ -4432,7 +4432,7 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
2 DEPENDENT SUBQUERY t2 ALL NULL NULL NULL NULL 2 100.00 Using where
Warnings:
Note 1276 Field or reference 'test.t1.a' of SELECT #2 was resolved in SELECT #1
Note 1003 select 2 AS `2` from `test`.`t1` where exists(select 1 from `test`.`t2` where (`test`.`t1`.`a` = `test`.`t2`.`a`))
Note 1003 select 2 AS `2` from `test`.`t1` where exists(select 1 from `test`.`t2` where (`test`.`t1`.`a` = `test`.`t2`.`a`) limit 1)
EXPLAIN EXTENDED
SELECT 2 FROM t1 WHERE EXISTS ((SELECT 1 FROM t2 WHERE t1.a=t2.a) UNION
(SELECT 1 FROM t2 WHERE t1.a = t2.a));
@@ -4444,7 +4444,7 @@ NULL UNION RESULT <union2,3> ALL NULL NULL NULL NULL NULL NULL
Warnings:
Note 1276 Field or reference 'test.t1.a' of SELECT #2 was resolved in SELECT #1
Note 1276 Field or reference 'test.t1.a' of SELECT #3 was resolved in SELECT #1
Note 1003 select 2 AS `2` from `test`.`t1` where exists((select 1 from `test`.`t2` where (`test`.`t1`.`a` = `test`.`t2`.`a`)) union (select 1 from `test`.`t2` where (`test`.`t1`.`a` = `test`.`t2`.`a`)))
Note 1003 select 2 AS `2` from `test`.`t1` where exists((select 1 from `test`.`t2` where (`test`.`t1`.`a` = `test`.`t2`.`a`)) union (select 1 from `test`.`t2` where (`test`.`t1`.`a` = `test`.`t2`.`a`)) limit 1)
DROP TABLE t1,t2;
create table t0(a int);
insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
@@ -7182,5 +7182,36 @@ 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;
#
# MDEV-19429: Wrong query result with EXISTS and LIMIT 0
#
create table t10 (a int);
insert into t10 values (1),(2),(3);
create table t12 (a int);
insert into t12 values (1),(2),(3);
select * from t10 where exists (select * from t12 order by a limit 0);
a
explain select * from t10 where exists (select * from t12 order by a limit 0);
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 Zero limit
prepare stmt1 from "select * from t10 where exists (select * from t12 order by a limit ?)";
set @l=1;
execute stmt1 using @l;
a
1
2
3
set @l=2;
execute stmt1 using @l;
a
1
2
3
set @l=0;
execute stmt1 using @l;
a
deallocate prepare stmt1;
drop table t10, t12;
End of 5.5 tests
set @optimizer_switch_for_subselect_test=null;

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