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MDEV-323: SHOW EXPLAIN: Plan produced by SHOW EXPLAIN loses 'UNION RESULT' line

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- Make SHOW EXPLAIN code correctly print fake_select_lex: both in the case where 
  it has not yet been executed, and when it has been executed.
This commit is contained in:
Sergey Petrunya 2012-06-07 21:19:22 +04:00
parent a161c19bf2
commit 950dc8022e
4 changed files with 65 additions and 4 deletions
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34
mysql-test/r/show_explain.result
View File

@ -625,4 +625,38 @@ a + 1
set debug_dbug='';
DROP VIEW v1;
DROP TABLE t1;
#
# MDEV-323: SHOW EXPLAIN: Plan produced by SHOW EXPLAIN loses
# 'UNION RESULT' line on the way without saying that the plan was already deleted
#
CREATE TABLE t1 (a INT);
INSERT INTO t1 VALUES (4),(6);
EXPLAIN
SELECT a FROM t1 WHERE a IN ( SELECT 1+SLEEP(0.01) UNION SELECT 2 );
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2 Using where
2 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL No tables used
3 DEPENDENT UNION NULL NULL NULL NULL NULL NULL NULL No tables used
NULL UNION RESULT <union2,3> ALL NULL NULL NULL NULL NULL
set debug_dbug='d,show_explain_probe_union_read';
SELECT a FROM t1 WHERE a IN ( SELECT 1+SLEEP(0.01) UNION SELECT 2 );
show explain for $thr2;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2 Using where
2 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL No tables used
3 DEPENDENT UNION NULL NULL NULL NULL NULL NULL NULL No tables used
NULL UNION RESULT <union2,3> ALL NULL NULL NULL NULL NULL
Warnings:
Note 1003 SELECT a FROM t1 WHERE a IN ( SELECT 1+SLEEP(0.01) UNION SELECT 2 )
show explain for $thr2;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2 Using where
2 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL No tables used
3 DEPENDENT UNION NULL NULL NULL NULL NULL NULL NULL No tables used
NULL UNION RESULT <union2,3> ALL NULL NULL NULL NULL NULL
Warnings:
Note 1003 SELECT a FROM t1 WHERE a IN ( SELECT 1+SLEEP(0.01) UNION SELECT 2 )
a
set debug_dbug='';
DROP TABLE t1;
drop table t0;

27
mysql-test/t/show_explain.test
View File

@ -634,6 +634,33 @@ DROP VIEW v1;
DROP TABLE t1;
--echo #
--echo # MDEV-323: SHOW EXPLAIN: Plan produced by SHOW EXPLAIN loses
--echo # 'UNION RESULT' line on the way without saying that the plan was already deleted
--echo #
CREATE TABLE t1 (a INT);
INSERT INTO t1 VALUES (4),(6);
EXPLAIN
SELECT a FROM t1 WHERE a IN ( SELECT 1+SLEEP(0.01) UNION SELECT 2 );
set debug_dbug='d,show_explain_probe_union_read';
send
SELECT a FROM t1 WHERE a IN ( SELECT 1+SLEEP(0.01) UNION SELECT 2 );
connection default;
--source include/wait_condition.inc
evalp show explain for $thr2;
--source include/wait_condition.inc
evalp show explain for $thr2;
connection con1;
reap;
set debug_dbug='';
DROP TABLE t1;
## TODO: Test this: have several SHOW EXPLAIN requests be queued up for a
## thread and served together.

6
sql/sql_lex.cc
View File

@ -4165,10 +4165,8 @@ int st_select_lex_unit::print_explain(select_result_sink *output,
break;
}
/*
Note: it could be that fake_select_lex->join == NULL still at this point
*/
if (fake_select_lex && !fake_select_lex->join)
/* Note: fake_select_lex->join may be NULL or non-NULL at this point */
if (fake_select_lex)
{
res= print_fake_select_lex_join(output, TRUE /* on the fly */,
fake_select_lex, explain_flags);

2
sql/sql_union.cc
View File

@ -720,6 +720,8 @@ bool st_select_lex_unit::exec()
}
}
DBUG_EXECUTE_IF("show_explain_probe_union_read",
dbug_serve_apcs(thd, 1););
/* Send result to 'result' */
saved_error= TRUE;
{