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Commit 40b3525f authored by Sergei Petrunia's avatar Sergei Petrunia Committed by Sergei Golubchik
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MDEV-28621: group by optimization incorrectly removing subquery where subject buried in a function 

Workaround patch: Do not remove GROUP BY clause when it has
subquer(ies) in it.

remove_redundant_subquery_clauses() removes redundant GROUP BY clause
from queries in form:
  expr IN (SELECT no_aggregates GROUP BY ...)
  expr {CMP} {ALL|ANY|SOME} (SELECT no_aggregates GROUP BY ...)
This hits problems when the GROUP BY clause itself has subquer(y/ies).

This patch is just a workaround: it disables removal of GROUP BY clause
if the clause has one or more subqueries in it.

Tests:
- subselect_elimination.test has all known crashing cases.
- subselect4.result, insert_select.result are updated.
Note that in some cases results of SELECT are changed too (not just
EXPLAINs). These are caused by non-deterministic SQL: when running a
query like:

  x > ANY( SELECT col1 FROM t1 GROUP BY constant_expression)

without removing the GROUP BY, the executor is free to pick the value
of t1.col1 from any row in the GROUP BY group (denote it $COL1_VAL).
Then, it computes x > ANY(SELECT $COL1_VAL).

When running the same query and removing the GROUP BY:

   x > ANY( SELECT col1 FROM t1)

the executor will actually check all rows of t1.
parent ec6aa9ac
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mysql-test/main/insert_select.result
View file @ 40b3525f
...@@ -973,7 +973,6 @@ select * from t1; ...@@ -973,7 +973,6 @@ select * from t1;
a a
3 3
1 1
2
delete from t1; delete from t1;
insert into t1 values (3), (1); insert into t1 values (3), (1);
insert into t1 insert into t1
...@@ -984,8 +983,6 @@ select * from t1; ...@@ -984,8 +983,6 @@ select * from t1;
a a
3 3
1 1
3
2
delete from t1; delete from t1;
insert into t1 values (3), (1); insert into t1 values (3), (1);
insert into t1 insert into t1
...@@ -996,6 +993,7 @@ select * from t1; ...@@ -996,6 +993,7 @@ select * from t1;
a a
3 3
1 1
3
2 2
delete from t1; delete from t1;
insert into t1 values (3), (1); insert into t1 values (3), (1);
...@@ -1022,7 +1020,6 @@ select * from t1; ...@@ -1022,7 +1020,6 @@ select * from t1;
a a
3 3
1 1
2
delete from t1; delete from t1;
insert into t1 values (3), (1); insert into t1 values (3), (1);
execute stmt; execute stmt;
...@@ -1030,7 +1027,6 @@ select * from t1; ...@@ -1030,7 +1027,6 @@ select * from t1;
a a
3 3
1 1
2
delete from t1; delete from t1;
insert into t1 values (3), (1); insert into t1 values (3), (1);
delete from t1 delete from t1
...@@ -1040,6 +1036,8 @@ group by (select * from (select a from t1) dt ...@@ -1040,6 +1036,8 @@ group by (select * from (select a from t1) dt
where a = 1))); where a = 1)));
select * from t1; select * from t1;
a a
3
1
deallocate prepare stmt; deallocate prepare stmt;
drop table t1,t2,t3; drop table t1,t2,t3;
# #
......
mysql-test/main/subselect4.result
View file @ 40b3525f
This diff is collapsed.
mysql-test/main/subselect_elimination.result 0 → 100644
View file @ 40b3525f
#
# MDEV-28621 group by optimization incorrectly removing subquery where
# subject buried in a function
#
CREATE TABLE t1 (i int) ;
INSERT INTO t1 VALUES (1),(2),(3);
SELECT 1 FROM t1
WHERE i in
( SELECT a+1
FROM
(SELECT (SELECT i FROM (SELECT 1 FROM t1) dt) AS a FROM t1) dt2
GROUP BY a
);
ERROR 21000: Subquery returns more than 1 row
DROP TABLE t1;
create table t1 (a int, b int, c int);
insert into t1 select seq, seq, seq from seq_1_to_10;
create table t2 as select * from t1;
create table t20 as select * from t1;
create table t21 as select * from t1;
create table t3 as select * from t1;
select a, a in
(
select
(
select max(c) from t20 where t20.a<=t2.a
) as SUBQ1 from t2 group by SUBQ1+1
) as COL
from t1;
a COL
1 1
2 1
3 1
4 1
5 1
6 1
7 1
8 1
9 1
10 1
create view v2 as
select
a, b,
(select max(c) from t20 where t20.a<=t2.a) as SUBQ1,
(select max(c) from t21 where t21.a<=t2.a) as SUBQ2
from t2;
# test partial elimination
explain
select
a,
a in (select a from v2 where a>3 and v2.SUBQ2>=0 group by v2.SUBQ1, v2.SUBQ2)
from t1;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 10
2 MATERIALIZED t2 ALL NULL NULL NULL NULL 10 Using where; Using temporary
5 DEPENDENT SUBQUERY t21 ALL NULL NULL NULL NULL 10 Using where
4 DEPENDENT SUBQUERY t20 ALL NULL NULL NULL NULL 10 Using where
# test buried subselects in group by clause
select a, a in
(
select
(
select max(c) from t20 where t20.a<=t2.a
)*2 as SUBQ1 from t2 group by SUBQ1+1
) as COL
from t1;
a COL
1 0
2 1
3 0
4 1
5 0
6 1
7 0
8 1
9 0
10 1
drop view v2;
drop table t1, t2, t20, t21, t3;
# Testcase from MDEV-32311
SELECT (
( WITH x ( x ) AS
(SELECT ( SELECT 'x' UNION SELECT 'x' ) FROM ( SELECT ( 'x' ) ) x)
SELECT x FROM x
WHERE x IN ( ( SELECT 'x' AND x GROUP BY x ) )
)
) AS SUBQ;
SUBQ
x
# MDEV-32390:
CREATE TABLE t0 ( c43 DECIMAL ( 31 ) DEFAULT ( 45 ) ) ;
INSERT INTO t0 VALUES ( 13 ) , ( 29 ) ;
ALTER TABLE t0 ADD COLUMN c24 INT AFTER c43 ;
INSERT INTO t0 VALUES ( DEFAULT , DEFAULT ) , ( DEFAULT , DEFAULT ) ;
SELECT t1 . c22 AS c9 FROM ( SELECT ( SELECT + EXISTS ( SELECT -128 AS c29 ) <<
LOCATE ( t0 . c43 , t0 . c24 <= t0 . c24 NOT BETWEEN 4642475734208631537 AND
-108 , NULLIF ( 57 , -8 ) SOUNDS LIKE TRIM( TRAILING FROM 6107036197732405580 )
) - t0 . c43 AS c57 FROM t0 LIMIT 1 ) AS c22 FROM t0 ) AS t1 HAVING TRIM( CASE
t1 . c22 WHEN -16 THEN RAND ( ) % HEX ( t1 . c22 ) - SUBSTRING_INDEX ( t1 . c22,
':A9SEZxtjN,fKN*zR' , 'V*vhJb}&c%Op,[T[S,j`F9NDsK;\'8 4;m"
P,ce}1r"3ID1DN' ) >> NULLIF ( t1 . c22 , -95 ) ELSE -2 END IS TRUE
FROM t1 . c22 >= EXISTS ( SELECT t2 . c57 AS c59 FROM ( SELECT CASE c24 WHEN
-103 THEN 85 ELSE 22 END IS TRUE AS c57 FROM t0 ) AS t2 WHERE MOD ( 64 , 46 ) =
CONVERT ( 73 , BINARY ) % RAND ( ) IS NOT NULL = -65 GROUP BY c57 , c22 , c22
WINDOW w0 AS ( PARTITION BY t2 . c57 ) ) & PI ( ) ) ;
c9
DROP TABLE t0;
# MDEV-32309
SELECT
( WITH x ( x ) AS
(
WITH x ( x ) AS ( SELECT 1 ) SELECT ( SELECT x ) FROM x
)
SELECT x FROM x WHERE x IN ( SELECT NULL GROUP BY x )
) as col1 ;
col1
NULL
# MDEV-32391
CREATE TABLE t0 ( c15 INT , c33 INT ) engine=innodb;
INSERT INTO t0 ( c15 ) WITH t1 AS ( SELECT SQRT ( 123 ) NOT
REGEXP MOD ( 91 , -121 ) = ALL ( SELECT c15 AS c33 FROM t0 ) AS c49 FROM t0 )
SELECT t1 . c49 IS UNKNOWN AS c59 FROM t1 CROSS JOIN t0 AS t2
WHERE t1 . c49 = + EXISTS ( SELECT -5839312620871436105 AS c17 GROUP BY c49 )
BETWEEN -109 AND CHAR_LENGTH ( 2694839150676403988 ) - - LOWER ( -13 ) ;
DROP TABLE t0;
# MDEV-28620
CREATE TABLE t1 ( a int);
INSERT INTO t1 VALUES (1),(2);
SELECT EXISTS
( SELECT 1 FROM t1 GROUP BY 1 IN (SELECT a FROM t1)
ORDER BY a + (SELECT 1 FROM t1 WHERE (1,2) NOT IN (SELECT 1,0))
) as SUBQ;
ERROR 21000: Subquery returns more than 1 row
DROP TABLE t1;
# MDEV-30842 Item_subselect::get_cache_parameters and UBSAN member
# access within null pointer
CREATE TABLE x (x INT) ENGINE=InnoDB;
INSERT INTO x (x) VALUES (0);
INSERT INTO x (x) VALUES (x IN (SELECT (SELECT x FROM (SELECT x FROM
(SELECT 0 IN (SELECT x=0 FROM (SELECT x FROM (SELECT (SELECT (SELECT (SELECT
(SELECT 0 AS x) FROM x AS x) IN (SELECT 0 AS x) AS x) FROM x AS x) IN
(SELECT x WHERE x=0) AS x FROM x AS x) AS x) AS x GROUP BY x) AS x FROM x) AS x)
AS x) IN (SELECT 0 AS x) AS x FROM x));
ERROR HY000: Table 'x' is specified twice, both as a target for 'INSERT' and as a separate source for data
DROP TABLE x;
# MDEV-28622: Item_subselect eliminated flag set but Item still
# evaluated/used.
CREATE TABLE t1 ( a int) ;
CREATE VIEW v1 (i) AS SELECT EXISTS(SELECT 1) FROM t1;
SELECT 1 FROM v1 WHERE i NOT IN (SELECT i = 0 FROM v1 WHERE i = -1 GROUP BY i);
1
DROP TABLE t1;
DROP VIEW v1;
CREATE TABLE t(c1 INT);
SELECT 0
WHERE 0 IN
(
SELECT 0 FROM
(
SELECT 0 IN
(
SELECT
(
SELECT c1 FROM t
)
) AS c
FROM t
) AS dt
WHERE c GROUP BY c
);
0
DROP TABLE t;
create table t1 (a int, b int, c int);
insert into t1 select seq, seq, seq from seq_1_to_10;
create table t2 as select * from t1;
create table t20 as select * from t1;
create table t3 as select * from t1;
create view v2 as
select
a, b, (select max(c) from t20 where t20.a<=t2.a) as SUBQ1
from t2;
explain
select
a, a in (select a from v2 where a>3 group by v2.SUBQ1)
from t1;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 10
2 MATERIALIZED t2 ALL NULL NULL NULL NULL 10 Using where; Using temporary
4 DEPENDENT SUBQUERY t20 ALL NULL NULL NULL NULL 10 Using where
prepare s from '
explain
select
a, a in (select a from v2 where a>3 group by v2.SUBQ1)
from t1';
execute s;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 10
2 MATERIALIZED t2 ALL NULL NULL NULL NULL 10 Using where; Using temporary
4 DEPENDENT SUBQUERY t20 ALL NULL NULL NULL NULL 10 Using where
execute s;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 10
2 MATERIALIZED t2 ALL NULL NULL NULL NULL 10 Using where; Using temporary
4 DEPENDENT SUBQUERY t20 ALL NULL NULL NULL NULL 10 Using where
execute s;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 10
2 MATERIALIZED t2 ALL NULL NULL NULL NULL 10 Using where; Using temporary
4 DEPENDENT SUBQUERY t20 ALL NULL NULL NULL NULL 10 Using where
prepare s from '
explain
select
a, a in (select a from v2 where a>3 and SUBQ1+1 group by v2.SUBQ1)
from t1';
execute s;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 10
2 MATERIALIZED t2 ALL NULL NULL NULL NULL 10 Using where; Using temporary
4 DEPENDENT SUBQUERY t20 ALL NULL NULL NULL NULL 10 Using where
execute s;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 10
2 MATERIALIZED t2 ALL NULL NULL NULL NULL 10 Using where; Using temporary
4 DEPENDENT SUBQUERY t20 ALL NULL NULL NULL NULL 10 Using where
execute s;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 10
2 MATERIALIZED t2 ALL NULL NULL NULL NULL 10 Using where; Using temporary
4 DEPENDENT SUBQUERY t20 ALL NULL NULL NULL NULL 10 Using where
create procedure p1()
begin
explain
select
a, a in (select a from v2 where a>3 group by v2.SUBQ1)
from t1;
end//
create procedure p2()
begin
explain
select
a, a in (select a from v2 where a>3 and SUBQ1+1 group by v2.SUBQ1)
from t1;
end//
call p1();
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 10
2 MATERIALIZED t2 ALL NULL NULL NULL NULL 10 Using where; Using temporary
4 DEPENDENT SUBQUERY t20 ALL NULL NULL NULL NULL 10 Using where
call p1();
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 10
2 MATERIALIZED t2 ALL NULL NULL NULL NULL 10 Using where; Using temporary
4 DEPENDENT SUBQUERY t20 ALL NULL NULL NULL NULL 10 Using where
call p2();
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 10
2 MATERIALIZED t2 ALL NULL NULL NULL NULL 10 Using where; Using temporary
4 DEPENDENT SUBQUERY t20 ALL NULL NULL NULL NULL 10 Using where
call p2();
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 10
2 MATERIALIZED t2 ALL NULL NULL NULL NULL 10 Using where; Using temporary
4 DEPENDENT SUBQUERY t20 ALL NULL NULL NULL NULL 10 Using where
drop procedure p1;
drop procedure p2;
drop view v2;
drop table t1,t2,t3,t20;
# end of 10.4 tests
mysql-test/main/subselect_elimination.test 0 → 100644
View file @ 40b3525f
--source include/have_innodb.inc
--source include/have_sequence.inc
--echo #
--echo # MDEV-28621 group by optimization incorrectly removing subquery where
--echo # subject buried in a function
--echo #
CREATE TABLE t1 (i int) ;
INSERT INTO t1 VALUES (1),(2),(3);
--error ER_SUBQUERY_NO_1_ROW
SELECT 1 FROM t1
WHERE i in
( SELECT a+1
FROM
(SELECT (SELECT i FROM (SELECT 1 FROM t1) dt) AS a FROM t1) dt2
GROUP BY a
);
DROP TABLE t1;
create table t1 (a int, b int, c int);
insert into t1 select seq, seq, seq from seq_1_to_10;
create table t2 as select * from t1;
create table t20 as select * from t1;
create table t21 as select * from t1;
create table t3 as select * from t1;
select a, a in
(
select
(
select max(c) from t20 where t20.a<=t2.a
) as SUBQ1 from t2 group by SUBQ1+1
) as COL
from t1;
create view v2 as
select
a, b,
(select max(c) from t20 where t20.a<=t2.a) as SUBQ1,
(select max(c) from t21 where t21.a<=t2.a) as SUBQ2
from t2;
--echo # test partial elimination
explain
select
a,
a in (select a from v2 where a>3 and v2.SUBQ2>=0 group by v2.SUBQ1, v2.SUBQ2)
from t1;
--echo # test buried subselects in group by clause
select a, a in
(
select
(
select max(c) from t20 where t20.a<=t2.a
)*2 as SUBQ1 from t2 group by SUBQ1+1
) as COL
from t1;
drop view v2;
drop table t1, t2, t20, t21, t3;
--echo # Testcase from MDEV-32311
# some warning duplicated using ps-protocol
--disable_warnings
SELECT (
( WITH x ( x ) AS
(SELECT ( SELECT 'x' UNION SELECT 'x' ) FROM ( SELECT ( 'x' ) ) x)
SELECT x FROM x
WHERE x IN ( ( SELECT 'x' AND x GROUP BY x ) )
)
) AS SUBQ;
--enable_warnings
--echo # MDEV-32390:
CREATE TABLE t0 ( c43 DECIMAL ( 31 ) DEFAULT ( 45 ) ) ;
INSERT INTO t0 VALUES ( 13 ) , ( 29 ) ;
ALTER TABLE t0 ADD COLUMN c24 INT AFTER c43 ;
INSERT INTO t0 VALUES ( DEFAULT , DEFAULT ) , ( DEFAULT , DEFAULT ) ;
SELECT t1 . c22 AS c9 FROM ( SELECT ( SELECT + EXISTS ( SELECT -128 AS c29 ) <<
LOCATE ( t0 . c43 , t0 . c24 <= t0 . c24 NOT BETWEEN 4642475734208631537 AND
-108 , NULLIF ( 57 , -8 ) SOUNDS LIKE TRIM( TRAILING FROM 6107036197732405580 )
) - t0 . c43 AS c57 FROM t0 LIMIT 1 ) AS c22 FROM t0 ) AS t1 HAVING TRIM( CASE
t1 . c22 WHEN -16 THEN RAND ( ) % HEX ( t1 . c22 ) - SUBSTRING_INDEX ( t1 . c22,
':A9SEZxtjN,fKN*zR' , 'V*vhJb}&c%Op,[T[S,j`F9NDsK;\'8 4;m"
P,ce}1r"3ID1DN' ) >> NULLIF ( t1 . c22 , -95 ) ELSE -2 END IS TRUE
FROM t1 . c22 >= EXISTS ( SELECT t2 . c57 AS c59 FROM ( SELECT CASE c24 WHEN
-103 THEN 85 ELSE 22 END IS TRUE AS c57 FROM t0 ) AS t2 WHERE MOD ( 64 , 46 ) =
CONVERT ( 73 , BINARY ) % RAND ( ) IS NOT NULL = -65 GROUP BY c57 , c22 , c22
WINDOW w0 AS ( PARTITION BY t2 . c57 ) ) & PI ( ) ) ;
DROP TABLE t0;
--echo # MDEV-32309
SELECT
( WITH x ( x ) AS
(
WITH x ( x ) AS ( SELECT 1 ) SELECT ( SELECT x ) FROM x
)
SELECT x FROM x WHERE x IN ( SELECT NULL GROUP BY x )
) as col1 ;
--echo # MDEV-32391
CREATE TABLE t0 ( c15 INT , c33 INT ) engine=innodb;
INSERT INTO t0 ( c15 ) WITH t1 AS ( SELECT SQRT ( 123 ) NOT
REGEXP MOD ( 91 , -121 ) = ALL ( SELECT c15 AS c33 FROM t0 ) AS c49 FROM t0 )
SELECT t1 . c49 IS UNKNOWN AS c59 FROM t1 CROSS JOIN t0 AS t2
WHERE t1 . c49 = + EXISTS ( SELECT -5839312620871436105 AS c17 GROUP BY c49 )
BETWEEN -109 AND CHAR_LENGTH ( 2694839150676403988 ) - - LOWER ( -13 ) ;
DROP TABLE t0;
--echo # MDEV-28620
CREATE TABLE t1 ( a int);
INSERT INTO t1 VALUES (1),(2);
--error ER_SUBQUERY_NO_1_ROW
SELECT EXISTS
( SELECT 1 FROM t1 GROUP BY 1 IN (SELECT a FROM t1)
ORDER BY a + (SELECT 1 FROM t1 WHERE (1,2) NOT IN (SELECT 1,0))
) as SUBQ;
DROP TABLE t1;
--echo # MDEV-30842 Item_subselect::get_cache_parameters and UBSAN member
--echo # access within null pointer
CREATE TABLE x (x INT) ENGINE=InnoDB;
INSERT INTO x (x) VALUES (0);
--error ER_UPDATE_TABLE_USED
INSERT INTO x (x) VALUES (x IN (SELECT (SELECT x FROM (SELECT x FROM
(SELECT 0 IN (SELECT x=0 FROM (SELECT x FROM (SELECT (SELECT (SELECT (SELECT
(SELECT 0 AS x) FROM x AS x) IN (SELECT 0 AS x) AS x) FROM x AS x) IN
(SELECT x WHERE x=0) AS x FROM x AS x) AS x) AS x GROUP BY x) AS x FROM x) AS x)
AS x) IN (SELECT 0 AS x) AS x FROM x));
DROP TABLE x;
--echo # MDEV-28622: Item_subselect eliminated flag set but Item still
--echo # evaluated/used.
CREATE TABLE t1 ( a int) ;
CREATE VIEW v1 (i) AS SELECT EXISTS(SELECT 1) FROM t1;
SELECT 1 FROM v1 WHERE i NOT IN (SELECT i = 0 FROM v1 WHERE i = -1 GROUP BY i);
DROP TABLE t1;
DROP VIEW v1;
CREATE TABLE t(c1 INT);
SELECT 0
WHERE 0 IN
(
SELECT 0 FROM
(
SELECT 0 IN
(
SELECT
(
SELECT c1 FROM t
)
) AS c
FROM t
) AS dt
WHERE c GROUP BY c
);
DROP TABLE t;
create table t1 (a int, b int, c int);
insert into t1 select seq, seq, seq from seq_1_to_10;
create table t2 as select * from t1;
create table t20 as select * from t1;
create table t3 as select * from t1;
create view v2 as
select
a, b, (select max(c) from t20 where t20.a<=t2.a) as SUBQ1
from t2;
explain
select
a, a in (select a from v2 where a>3 group by v2.SUBQ1)
from t1;
prepare s from '
explain
select
a, a in (select a from v2 where a>3 group by v2.SUBQ1)
from t1';
execute s;
execute s;
execute s;
prepare s from '
explain
select
a, a in (select a from v2 where a>3 and SUBQ1+1 group by v2.SUBQ1)
from t1';
execute s;
execute s;
execute s;
delimiter //;
create procedure p1()
begin
explain
select
a, a in (select a from v2 where a>3 group by v2.SUBQ1)
from t1;
end//
create procedure p2()
begin
explain
select
a, a in (select a from v2 where a>3 and SUBQ1+1 group by v2.SUBQ1)
from t1;
end//
delimiter ;//
call p1();
call p1();
call p2();
call p2();
drop procedure p1;
drop procedure p2;
drop view v2;
drop table t1,t2,t3,t20;
--echo # end of 10.4 tests
sql/sql_select.cc
View file @ 40b3525f
...@@ -671,37 +671,57 @@ void remove_redundant_subquery_clauses(st_select_lex *subq_select_lex) ...@@ -671,37 +671,57 @@ void remove_redundant_subquery_clauses(st_select_lex *subq_select_lex)
if (subq_select_lex->group_list.elements && if (subq_select_lex->group_list.elements &&
!subq_select_lex->with_sum_func && !subq_select_lex->join->having) !subq_select_lex->with_sum_func && !subq_select_lex->join->having)
{ {
/*
Temporary workaround for MDEV-28621: Do not remove GROUP BY expression
if it has any subqueries in it.
*/
bool have_subquery= false;
for (ORDER *ord= subq_select_lex->group_list.first; ord; ord= ord->next) for (ORDER *ord= subq_select_lex->group_list.first; ord; ord= ord->next)
{ {
/* if ((*ord->item)->with_subquery())
Do not remove the item if it is used in select list and then referred {
from GROUP BY clause by its name or number. Example: have_subquery= true;
break;
select (select ... ) as SUBQ ... group by SUBQ }
}
Here SUBQ cannot be removed. if (!have_subquery)
*/ {
if (!ord->in_field_list) for (ORDER *ord= subq_select_lex->group_list.first; ord; ord= ord->next)
{ {
(*ord->item)->walk(&Item::eliminate_subselect_processor, FALSE, NULL);
/* /*
Remove from the JOIN::all_fields list any reference to the elements Do not remove the item if it is used in select list and then referred
of the eliminated GROUP BY list unless it is 'in_field_list'. from GROUP BY clause by its name or number. Example:
This is needed in order not to confuse JOIN::make_aggr_tables_info()
when it constructs different structure for execution phase. select (select ... ) as SUBQ ... group by SUBQ
*/
List_iterator<Item> li(subq_select_lex->join->all_fields); Here SUBQ cannot be removed.
Item *item; */
while ((item= li++)) if (!ord->in_field_list)
{ {
if (item == *ord->item) /*
li.remove(); Not necessary due to workaround for MDEV-28621:
} (*ord->item)->walk(&Item::eliminate_subselect_processor, FALSE, NULL);
*/
/*
Remove from the JOIN::all_fields list any reference to the elements
of the eliminated GROUP BY list unless it is 'in_field_list'.
This is needed in order not to confuse JOIN::make_aggr_tables_info()
when it constructs different structure for execution phase.
*/
List_iterator<Item> li(subq_select_lex->join->all_fields);
Item *item;
while ((item= li++))
{
if (item == *ord->item)
li.remove();
}
}
} }
subq_select_lex->join->group_list= NULL;
subq_select_lex->group_list.empty();
DBUG_PRINT("info", ("GROUP BY removed"));
} }
subq_select_lex->join->group_list= NULL;
subq_select_lex->group_list.empty();
DBUG_PRINT("info", ("GROUP BY removed"));
} }
/* /*
......
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