mariadb/mysql-test/r/show_explain.result

drop table if exists t0, t1, t2;
drop view if exists v1;
create table t0 (a int);
insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table t1 (a int);
insert into t1 select A.a + 10*B.a + 100*C.a from t0 A, t0 B, t0 C;
alter table t1 add b int, add c int, add filler char(32);
update t1 set b=a, c=a, filler='fooo';
alter table t1 add key(a), add key(b);
show explain for 2*1000*1000*1000;
ERROR HY000: Unknown thread id: 2000000000
show explain for (select max(a) from t0);
ERROR 42000: This version of MySQL doesn't yet support 'Usage of subqueries or stored function calls as part of this statement'
show explain for $thr2;
ERROR HY000: Error when executing command SHOW EXPLAIN: Target is not running EXPLAINable command
show explain for $thr1;
ERROR HY000: Error when executing command SHOW EXPLAIN: Target is not running EXPLAINable command
set @show_explain_probe_select_id=1;
set debug='d,show_explain_probe_1';
select count(*) from t1 where a < 100000;
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	index	a	a	5	NULL	1000	Using where; Using index
Warnings:
Note	1003	select count(*) from t1 where a < 100000
count(*)
1000
select max(c) from t1 where a < 10;
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	range	a	a	5	NULL	10	Using index condition
Warnings:
Note	1003	select max(c) from t1 where a < 10
max(c)
9
# We can catch EXPLAIN, too.
set @show_expl_tmp= @@optimizer_switch;
set optimizer_switch='index_condition_pushdown=on,mrr=on,mrr_sort_keys=on';
explain select max(c) from t1 where a < 10;
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	range	a	a	5	NULL	10	Using index condition; Rowid-ordered scan
Warnings:
Note	1003	explain select max(c) from t1 where a < 10
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	range	a	a	5	NULL	10	Using index condition; Rowid-ordered scan
set optimizer_switch= @show_expl_tmp;
# UNION, first branch 
set @show_explain_probe_select_id=1;
set debug='d,show_explain_probe_1';
explain select a from t0 A union select a+1 from t0 B;
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	A	ALL	NULL	NULL	NULL	NULL	10	
2	UNION	B	ALL	NULL	NULL	NULL	NULL	10	
NULL	UNION RESULT	<union1,2>	ALL	NULL	NULL	NULL	NULL	NULL	
Warnings:
Note	1003	explain select a from t0 A union select a+1 from t0 B
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	A	ALL	NULL	NULL	NULL	NULL	10	
2	UNION	B	ALL	NULL	NULL	NULL	NULL	10	
NULL	UNION RESULT	<union1,2>	ALL	NULL	NULL	NULL	NULL	NULL	
# UNION, second branch
set @show_explain_probe_select_id=1;
set debug='d,show_explain_probe_1';
explain select a from t0 A union select a+1 from t0 B;
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	A	ALL	NULL	NULL	NULL	NULL	10	
2	UNION	B	ALL	NULL	NULL	NULL	NULL	10	
NULL	UNION RESULT	<union1,2>	ALL	NULL	NULL	NULL	NULL	NULL	
Warnings:
Note	1003	explain select a from t0 A union select a+1 from t0 B
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	A	ALL	NULL	NULL	NULL	NULL	10	
2	UNION	B	ALL	NULL	NULL	NULL	NULL	10	
NULL	UNION RESULT	<union1,2>	ALL	NULL	NULL	NULL	NULL	NULL	
# Uncorrelated  subquery, select
set @show_explain_probe_select_id=1;
set debug='d,show_explain_probe_1';
select a, (select max(a) from t0 B) from t0 A where a<1;
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	A	ALL	NULL	NULL	NULL	NULL	10	Using where
2	SUBQUERY	B	ALL	NULL	NULL	NULL	NULL	10	
Warnings:
Note	1003	select a, (select max(a) from t0 B) from t0 A where a<1
a	(select max(a) from t0 B)
0	9
# Uncorrelated  subquery, explain
set @show_explain_probe_select_id=1;
set debug='d,show_explain_probe_1';
explain select a, (select max(a) from t0 B) from t0 A where a<1;
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	A	ALL	NULL	NULL	NULL	NULL	10	Using where
2	SUBQUERY	B	ALL	NULL	NULL	NULL	NULL	10	
Warnings:
Note	1003	explain select a, (select max(a) from t0 B) from t0 A where a<1
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	A	ALL	NULL	NULL	NULL	NULL	10	Using where
2	SUBQUERY	B	ALL	NULL	NULL	NULL	NULL	10	
# correlated  subquery, select
set @show_explain_probe_select_id=1;
set debug='d,show_explain_probe_1';
select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1;
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	a	ALL	NULL	NULL	NULL	NULL	10	Using where
2	DEPENDENT SUBQUERY	b	ALL	NULL	NULL	NULL	NULL	10	Using where
Warnings:
Note	1003	select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1
a	(select max(a) from t0 b where b.a+a.a<10)
0	9
# correlated  subquery, explain
set @show_explain_probe_select_id=1;
set debug='d,show_explain_probe_1';
select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1;
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	a	ALL	NULL	NULL	NULL	NULL	10	Using where
2	DEPENDENT SUBQUERY	b	ALL	NULL	NULL	NULL	NULL	10	Using where
Warnings:
Note	1003	select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1
a	(select max(a) from t0 b where b.a+a.a<10)
0	9
# correlated  subquery, select, while inside the subquery
set @show_explain_probe_select_id=2;
set debug='d,show_explain_probe_1';
select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1;
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	a	ALL	NULL	NULL	NULL	NULL	10	Using where
2	DEPENDENT SUBQUERY	b	ALL	NULL	NULL	NULL	NULL	10	Using where
Warnings:
Note	1003	select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1
a	(select max(a) from t0 b where b.a+a.a<10)
0	9
# correlated  subquery, explain, while inside the subquery
set @show_explain_probe_select_id=2;
set debug='d,show_explain_probe_1';
select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1;
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	a	ALL	NULL	NULL	NULL	NULL	10	Using where
2	DEPENDENT SUBQUERY	b	ALL	NULL	NULL	NULL	NULL	10	Using where
Warnings:
Note	1003	select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1
a	(select max(a) from t0 b where b.a+a.a<10)
0	9
# Try to do SHOW EXPLAIN for a query that runs a  SET command:
#   I've found experimentally that select_id==2 here...
# 
set @show_explain_probe_select_id=2;
set debug='d,show_explain_probe_1';
set @foo= (select max(a) from t0 where sin(a) >0);
show explain for $thr2;
ERROR HY000: Error when executing command SHOW EXPLAIN: Target is not running EXPLAINable command
#
# Attempt SHOW EXPLAIN for an UPDATE
#
create table t2 as select a as a, a as dummy from t0 limit 2;
set @show_explain_probe_select_id=2;
set debug='d,show_explain_probe_1';
update t2 set dummy=0 where (select max(a) from t0 where t2.a + t0.a <3) >3 ;
show explain for $thr2;
ERROR HY000: Error when executing command SHOW EXPLAIN: Target is not running EXPLAINable command
show explain for $thr2;
ERROR HY000: Error when executing command SHOW EXPLAIN: Target is not running EXPLAINable command
drop table t2;
#
# Attempt SHOW EXPLAIN for a DELETE
# 
create table t2 as select a as a, a as dummy from t0 limit 2;
set @show_explain_probe_select_id=2;
set debug='d,show_explain_probe_1';
delete from t2 where (select max(a) from t0 where t2.a + t0.a <3) >3 ;
show explain for $thr2;
ERROR HY000: Error when executing command SHOW EXPLAIN: Target is not running EXPLAINable command
show explain for $thr2;
ERROR HY000: Error when executing command SHOW EXPLAIN: Target is not running EXPLAINable command
drop table t2;
#
# Multiple SHOW EXPLAIN calls for one select 
# 
create table t2 as select a as a, a as dummy from t0 limit 3;
set @show_explain_probe_select_id=2;
set debug='d,show_explain_probe_1';
select t2.a, ((select max(a) from t0 where t2.a + t0.a <3) >3) as SUBQ from t2;
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	3	
2	DEPENDENT SUBQUERY	t0	ALL	NULL	NULL	NULL	NULL	10	Using where
Warnings:
Note	1003	select t2.a, ((select max(a) from t0 where t2.a + t0.a <3) >3) as SUBQ from t2
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	3	
2	DEPENDENT SUBQUERY	t0	ALL	NULL	NULL	NULL	NULL	10	Using where
Warnings:
Note	1003	select t2.a, ((select max(a) from t0 where t2.a + t0.a <3) >3) as SUBQ from t2
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	3	
2	DEPENDENT SUBQUERY	t0	ALL	NULL	NULL	NULL	NULL	10	Using where
Warnings:
Note	1003	select t2.a, ((select max(a) from t0 where t2.a + t0.a <3) >3) as SUBQ from t2
a	SUBQ
0	0
1	0
2	0
drop table t2;
#
# SHOW EXPLAIN for SELECT ... ORDER BY with "Using filesort"
#
explain select * from t0 order by a;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t0	ALL	NULL	NULL	NULL	NULL	10	Using filesort
set debug='d,show_explain_probe_1';
set @show_explain_probe_select_id=1;
select * from t0 order by a;
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t0	ALL	NULL	NULL	NULL	NULL	10	Using filesort
Warnings:
Note	1003	select * from t0 order by a
a
0
1
2
3
4
5
6
7
8
9
#
# SHOW EXPLAIN for SELECT ... with "Using temporary"
#
explain select distinct a from t0;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t0	ALL	NULL	NULL	NULL	NULL	10	Using temporary
set debug='d,show_explain_probe_1';
set @show_explain_probe_select_id=1;
select distinct a from t0;
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t0	ALL	NULL	NULL	NULL	NULL	10	Using temporary
Warnings:
Note	1003	select distinct a from t0
a
0
1
2
3
4
5
6
7
8
9
#
# SHOW EXPLAIN for SELECT ... with "Using temporary; Using filesort"
#
explain select distinct a from t0;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t0	ALL	NULL	NULL	NULL	NULL	10	Using temporary
set debug='d,show_explain_probe_1';
set @show_explain_probe_select_id=1;
select distinct a from t0;
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t0	ALL	NULL	NULL	NULL	NULL	10	Using temporary
Warnings:
Note	1003	select distinct a from t0
a
0
1
2
3
4
5
6
7
8
9
set debug='';
#
# MDEV-238: SHOW EXPLAIN: Server crashes in JOIN::print_explain with FROM subquery and GROUP BY
#
CREATE TABLE t2 ( a INT );
INSERT INTO t2 VALUES (1),(2),(1),(4),(2);
explain SELECT alias.a FROM t2, ( SELECT * FROM t2 ) AS alias GROUP BY alias.a;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	5	Using temporary; Using filesort
1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	5	Using join buffer (flat, BNL join)
set debug='d,show_explain_in_find_all_keys';
SELECT alias.a FROM t2, ( SELECT * FROM t2 ) AS alias GROUP BY alias.a;
# NOTE: current code will not show "Using join buffer":
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	5	Using temporary; Using filesort
1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	5	
Warnings:
Note	1003	SELECT alias.a FROM t2, ( SELECT * FROM t2 ) AS alias GROUP BY alias.a
a
1
2
4
set debug='';
DROP TABLE t2;
#
# MDEV-239: Assertion `field_types == 0 ... ' failed in Protocol_text::store(double, uint32, String*) with 
#          SHOW EXPLAIN over EXPLAIN EXTENDED
#
CREATE TABLE t2 (a INT);
INSERT INTO t2 VALUES (1),(2),(1),(4),(2);
EXPLAIN EXTENDED SELECT alias.a FROM t2, ( SELECT * FROM t2 ) AS alias GROUP BY alias.a ;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	5	100.00	Using temporary; Using filesort
1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	5	100.00	Using join buffer (flat, BNL join)
Warnings:
Note	1003	select `test`.`t2`.`a` AS `a` from `test`.`t2` join `test`.`t2` group by `test`.`t2`.`a`
set @show_explain_probe_select_id=1;
set debug='d,show_explain_probe_join_exec_end';
EXPLAIN EXTENDED SELECT alias.a FROM t2, ( SELECT * FROM t2 ) AS alias GROUP BY alias.a ;
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	5	Using temporary; Using filesort
1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	5	Using join buffer (flat, BNL join)
Warnings:
Note	1003	EXPLAIN EXTENDED SELECT alias.a FROM t2, ( SELECT * FROM t2 ) AS alias GROUP BY alias.a
id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	5	100.00	Using temporary; Using filesort
1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	5	100.00	Using join buffer (flat, BNL join)
Warnings:
Note	1003	select `test`.`t2`.`a` AS `a` from `test`.`t2` join `test`.`t2` group by `test`.`t2`.`a`
set debug='';
DROP TABLE t2;
#
# MDEV-240: SHOW EXPLAIN: Assertion `this->optimized == 2' failed in 
# JOIN::print_explain on query with a JOIN, TEMPTABLE view,
#          
CREATE TABLE t3 (a INT);
CREATE ALGORITHM=TEMPTABLE VIEW v1 AS SELECT * FROM t3;
INSERT INTO t3 VALUES (8);
CREATE TABLE t2 (b INT);
INSERT INTO t2 VALUES (4),(5),(6),(7),(8),(9);
explain SELECT * FROM v1, t2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	<derived2>	system	NULL	NULL	NULL	NULL	1	
1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	6	
2	DERIVED	t3	system	NULL	NULL	NULL	NULL	1	
set @show_explain_probe_select_id=2;
set debug='d,show_explain_probe_join_exec_end';
SELECT * FROM v1, t2;
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Not yet optimized
Warnings:
Note	1003	SELECT * FROM v1, t2
a	b
8	4
8	5
8	6
8	7
8	8
8	9
set debug='';
DROP VIEW v1;
DROP TABLE t2, t3;
#
# MDEV-267: SHOW EXPLAIN: Server crashes in JOIN::print_explain on most of queries
#
set @show_explain_probe_select_id=1;
set debug='d,show_explain_probe_join_exec_end';
select sleep(1);
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
Warnings:
Note	1003	select sleep(1)
sleep(1)
0
set debug='';
#
# Same as above, but try another reason for JOIN to be degenerate
#
set @show_explain_probe_select_id=1;
set debug='d,show_explain_probe_join_exec_end';
select * from t0 where 1>10;
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
Warnings:
Note	1003	select * from t0 where 1>10
a
set debug='';
#
# Same as above, but try another reason for JOIN to be degenerate (2)
#
create table t3(a int primary key);
insert into t3 select a from t0;
set @show_explain_probe_select_id=1;
set debug='d,show_explain_probe_join_exec_end';
select * from t0,t3 where t3.a=112233;
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t3	const	PRIMARY	PRIMARY	4		0	unique row not found
1	SIMPLE	t0	ALL	NULL	NULL	NULL	NULL	10	
Warnings:
Note	1003	select * from t0,t3 where t3.a=112233
a	a
set debug='';
drop table t3;
#
# MDEV-270: SHOW EXPLAIN: server crashes in JOIN::print_explain on a query with 
#           select tables optimized away
#
CREATE TABLE t2 (pk INT PRIMARY KEY, a INT ) ENGINE=MyISAM;
INSERT INTO t2 VALUES 
(1,4),(2,62),(3,7),(4,1),(5,0),(6,7),(7,7),(8,1),(9,7),(10,1),
(11,5),(12,2),(13,0),(14,1),(15,8),(16,1),(17,1),(18,9),(19,1),(20,5) ;
explain SELECT * FROM t2 WHERE a = 
(SELECT MAX(a) FROM t2 
WHERE pk= (SELECT MAX(pk) FROM t2 WHERE pk = 3)
);
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	20	Using where
2	SUBQUERY	t2	const	PRIMARY	PRIMARY	4	const	1	Using where
3	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
set @show_explain_probe_select_id=2;
set debug='d,show_explain_probe_do_select';
SELECT * FROM t2 WHERE a = 
(SELECT MAX(a) FROM t2 
WHERE pk= (SELECT MAX(pk) FROM t2 WHERE pk = 3)
);
show explain for $thr2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	20	Using where
2	SUBQUERY	t2	const	PRIMARY	PRIMARY	4		1	Using where
3	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
Warnings:
Note	1003	SELECT * FROM t2 WHERE a = 
(SELECT MAX(a) FROM t2 
WHERE pk= (SELECT MAX(pk) FROM t2 WHERE pk = 3)
)
pk	a
3	7
6	7
7	7
9	7
set debug='';
drop table t2;
drop table t0,t1;