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MWL#182: Explain running statements

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- 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
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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

17
sql/sql_lex.cc
View File

@ -3706,6 +3706,22 @@ int st_select_lex::print_explain(select_result_sink *output)
FALSE, // bool need_order,
FALSE, // bool distinct,
NULL); //const char *message
if (res)
goto err;
for (SELECT_LEX_UNIT *unit= join->select_lex->first_inner_unit();
unit;
unit= unit->next_unit())
{
/*
Display subqueries only if they are not parts of eliminated WHERE/ON
clauses.
*/
if (!(unit->item && unit->item->eliminated))
{
unit->print_explain(output);
}
}
}
else
{
@ -3717,6 +3733,7 @@ int st_select_lex::print_explain(select_result_sink *output)
FALSE, // bool distinct,
msg); //const char *message
}
err:
return 0;
}

11
sql/sql_select.cc
View File

@ -265,7 +265,9 @@ void dbug_serve_apcs(THD *thd, int n_calls)
/*
Usage
Debugging: check if @name=value, comparing as integer
Intended usage:
DBUG_EXECUTE_IF("show_explain_probe_2",
if (dbug_user_var_equals_int(thd, "select_id", select_id))
@ -2102,7 +2104,6 @@ void JOIN::exec_inner()
int tmp_error;
DBUG_ENTER("JOIN::exec");
DBUG_EXECUTE_IF("show_explain_probe_2", dbug_serve_apcs(thd, 1););
DBUG_EXECUTE_IF("show_explain_probe_1",
if (dbug_user_var_equals_int(thd,
"show_explain_probe_select_id",
@ -20516,6 +20517,7 @@ void JOIN::clear()
}
}
int print_fake_select_lex_join(select_result_sink *result, bool on_the_fly,
SELECT_LEX *select_lex, uint8 select_options)
{
@ -20594,6 +20596,7 @@ int print_fake_select_lex_join(select_result_sink *result, bool on_the_fly,
return 0;
}
/**
EXPLAIN handling.
@ -21162,6 +21165,10 @@ int JOIN::print_explain(select_result_sink *result, bool on_the_fly,
}
/*
See st_select_lex::print_explain() for the SHOW EXPLAIN counterpart
*/
static void select_describe(JOIN *join, bool need_tmp_table, bool need_order,
bool distinct,const char *message)
{