database/mariadb
1
0
Fork 0
mirror of https://github.com/MariaDB/server.git synced 2025-07-30 16:24:05 +03:00
Code Activity

MWL#182: Explain running statements

Browse Source 
- Get subqueries to work, part #1.
This commit is contained in:
Sergey Petrunya
2011-10-28 02:30:02 +04:00
parent 286a751490
commit ca020dfa9e
4 changed files with 155 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

61
mysql-test/r/show_explain.result
View File

@ -64,4 +64,65 @@ 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
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
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
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
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
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
a (select max(a) from t0 b where b.a+a.a<10)
0 9
drop table t0,t1;

69
mysql-test/t/show_explain.test
View File

@ -110,6 +110,7 @@ evalp show explain for $thr2;
connection con1;
reap;
--echo # UNION, second branch
set @show_explain_probe_select_id=1;
set debug='d,show_explain_probe_1';
@ -120,7 +121,73 @@ evalp show explain for $thr2;
connection con1;
reap;
# Let's try with a subquery
--echo # Uncorrelated subquery, select
set @show_explain_probe_select_id=1;
set debug='d,show_explain_probe_1';
send select a, (select max(a) from t0 B) from t0 A where a<1;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;
--echo # Uncorrelated subquery, explain
set @show_explain_probe_select_id=1;
set debug='d,show_explain_probe_1';
send explain select a, (select max(a) from t0 B) from t0 A where a<1;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;
--echo # correlated subquery, select
set @show_explain_probe_select_id=1;
set debug='d,show_explain_probe_1';
send select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;
--echo # correlated subquery, explain
set @show_explain_probe_select_id=1;
set debug='d,show_explain_probe_1';
send select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;
--echo # correlated subquery, select, while inside the subquery
set @show_explain_probe_select_id=2; # <---
set debug='d,show_explain_probe_1';
send select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;
--echo # correlated subquery, explain, while inside the subquery
set @show_explain_probe_select_id=2;
set debug='d,show_explain_probe_1';
send select a, (select max(a) from t0 b where b.a+a.a<10) from t0 a where a<1;
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;
# TODO: explain in the parent subuqery when the un-correlated child has been
# run (and have done irreversible cleanups)
# TODO: hit JOIN::optimize for non-select commands: UPDATE/DELETE, SET.
## TODO: Test this: multiple SHOW EXPLAIN calls in course of running of one select