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MDEV-305: SHOW EXPLAIN: ref returned by SHOW EXPLAIN is different from the normal EXPLAIN ('const' vs empty string)

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- The problem was that create_ref_for_key() would act differently, depending on 
  whether we're running EXPLAIN or the actual query.
- As the first step, fixed the EXPLAIN printout not to depend on actions in create_ref_for_key().
This commit is contained in:
Sergey Petrunya
2012-06-04 19:48:53 +04:00
parent 6f199f7c4f
commit a8b2e831f0
4 changed files with 69 additions and 14 deletions
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31
mysql-test/r/show_explain.result
View File

@ -448,7 +448,7 @@ 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
2 SUBQUERY t2 const PRIMARY PRIMARY 4 const 1 Using where
3 SUBQUERY NULL NULL NULL NULL NULL NULL NULL Select tables optimized away
Warnings:
Note 1003 SELECT * FROM t2 WHERE a =
@ -521,9 +521,7 @@ INSERT INTO t2 VALUES
(1,5),(2,4),(3,6),(4,9),(5,2),(6,8),(7,4),(8,8),(9,0),(10,43),
(11,23),(12,3),(13,45),(14,16),(15,2),(16,33),(17,2),(18,5),(19,9),(20,2);
set @show_explain_probe_select_id=1;
set debug='d,show_explain_probe_join_exec_end';
Warnings:
Warning 1287 The syntax '@@debug' is deprecated and will be removed in MariaDB 5.6. Please use '@@debug_dbug' instead
set debug_dbug='d,show_explain_probe_join_exec_end';
SELECT * FROM t2 WHERE (5, 78) IN (SELECT `a1`, MAX(`a1`) FROM t2 GROUP BY `a1`);
show explain for $thr2;
id select_type table type possible_keys key key_len ref rows Extra
@ -531,8 +529,25 @@ id select_type table type possible_keys key key_len ref rows Extra
Warnings:
Note 1003 SELECT * FROM t2 WHERE (5, 78) IN (SELECT `a1`, MAX(`a1`) FROM t2 GROUP BY `a1`)
pk a1
set debug='';
Warnings:
Warning 1287 The syntax '@@debug' is deprecated and will be removed in MariaDB 5.6. Please use '@@debug_dbug' instead
set debug_dbug='';
DROP TABLE t2;
drop table t0,t1;
DROP TABLE t1;
#
# MDEV-305: SHOW EXPLAIN: ref returned by SHOW EXPLAIN is different from the normal EXPLAIN ('const' vs empty string)
#
CREATE TABLE t1(a INT, KEY(a));
INSERT INTO t1 VALUES (3),(1),(5),(1);
set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_join_exec_start';
SELECT 'test' FROM t1 WHERE a=1;
show explain for $thr2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref a a 5 const 1 Using index
Warnings:
Note 1003 SELECT 'test' FROM t1 WHERE a=1
test
test
test
set debug_dbug='';
DROP TABLE t1;
drop table t0;

29
mysql-test/t/show_explain.test
View File

@ -508,7 +508,7 @@ INSERT INTO t2 VALUES
(11,23),(12,3),(13,45),(14,16),(15,2),(16,33),(17,2),(18,5),(19,9),(20,2);
set @show_explain_probe_select_id=1;
set debug='d,show_explain_probe_join_exec_end';
set debug_dbug='d,show_explain_probe_join_exec_end';
send
SELECT * FROM t2 WHERE (5, 78) IN (SELECT `a1`, MAX(`a1`) FROM t2 GROUP BY `a1`);
connection default;
@ -516,10 +516,33 @@ connection default;
evalp show explain for $thr2;
connection con1;
reap;
set debug='';
set debug_dbug='';
DROP TABLE t2;
DROP TABLE t1;
--echo #
--echo # MDEV-305: SHOW EXPLAIN: ref returned by SHOW EXPLAIN is different from the normal EXPLAIN ('const' vs empty string)
--echo #
CREATE TABLE t1(a INT, KEY(a));
INSERT INTO t1 VALUES (3),(1),(5),(1);
set @show_explain_probe_select_id=1;
set debug_dbug='d,show_explain_probe_join_exec_start';
send SELECT 'test' FROM t1 WHERE a=1;
connection default;
--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.
@ -527,4 +550,4 @@ DROP TABLE t2;
## TODO: SHOW EXPLAIN while the primary query is running EXPLAIN EXTENDED/PARTITIONS
##
drop table t0,t1;
drop table t0;