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Fixed LP bug #944782.

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This bug in the function JOIN::drop_unused_derived_keys() could
leave the internal structures for a materialized derived table
in an inconsistent state. This led to a not quite correct EXPLAIN
output when no additional key had been created to access the table.
It also may lead to more serious consequences: so, the test case
added with this fix caused a crash in mariadb-5.5.20.
This commit is contained in:
Igor Babaev 2012-03-04 22:38:17 -08:00
parent 000deedf3b
commit 6f3c39a057
4 changed files with 77 additions and 6 deletions
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38
mysql-test/r/derived_view.result
View File

@ -420,7 +420,7 @@ join
(select * from (select * from t1 where f1 < 7 group by f1) tt where f1 > 2) z
on x.f1 = z.f1;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE <derived3> ALL key0 NULL NULL NULL 11 100.00 Using where
1 SIMPLE <derived3> ALL NULL NULL NULL NULL 11 100.00 Using where
1 SIMPLE <derived5> ref key0 key0 5 tt.f1 2 100.00
5 DERIVED t1 ALL NULL NULL NULL NULL 11 100.00 Using where; Using temporary; Using filesort
3 DERIVED t1 ALL NULL NULL NULL NULL 11 100.00 Using where; Using temporary; Using filesort
@ -478,7 +478,7 @@ join
(select * from t1 where f1 < 7 group by f1) tt where f1 > 2 group by f1) z
on x.f1 = z.f1;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY <derived2> ALL key0 NULL NULL NULL 11 100.00 Using where
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 11 100.00 Using where
1 PRIMARY <derived4> ref key0 key0 5 x.f1 2 100.00
4 DERIVED <derived5> ALL NULL NULL NULL NULL 11 100.00 Using where; Using temporary; Using filesort
5 DERIVED t1 ALL NULL NULL NULL NULL 11 100.00 Using where; Using temporary; Using filesort
@ -1585,7 +1585,7 @@ a
EXPLAIN
SELECT v1.a FROM v1,v2 WHERE v2.b = v1.b ORDER BY 1;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY <derived2> ALL key0 NULL NULL NULL 3 Using where; Using filesort
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 3 Using where; Using filesort
1 PRIMARY <derived3> ref key0 key0 5 v1.b 2
3 DERIVED t2 ALL NULL NULL NULL NULL 5 Using temporary; Using filesort
2 DERIVED t1 ALL NULL NULL NULL NULL 3 Using temporary; Using filesort
@ -1929,5 +1929,37 @@ x
y
drop table t1,t2,t3;
set SESSION optimizer_switch= @save_optimizer_switch;
#
# LP BUG#944782: derived table from an information schema table
#
SET @save_optimizer_switch=@@optimizer_switch;
SET SESSION optimizer_switch='derived_merge=on';
SET SESSION optimizer_switch='derived_with_keys=on';
CREATE TABLE t1 (c1 int PRIMARY KEY, c2 char(5));
EXPLAIN
SELECT COUNT(*) > 0
FROM INFORMATION_SCHEMA.COLUMNS
INNER JOIN
(SELECT TABLE_SCHEMA,
GROUP_CONCAT(COLUMN_NAME ORDER BY SEQ_IN_INDEX ASC) AS COL_NAMES
FROM INFORMATION_SCHEMA.STATISTICS
GROUP BY TABLE_SCHEMA) AS UNIQUES
ON ( COLUMNS.TABLE_SCHEMA = UNIQUES.TABLE_SCHEMA);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY COLUMNS ALL NULL NULL NULL NULL NULL Open_frm_only; Scanned all databases
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 2 Using where; Using join buffer (flat, BNL join)
2 DERIVED STATISTICS ALL NULL NULL NULL NULL NULL Open_frm_only; Scanned all databases; Using filesort
SELECT COUNT(*) > 0
FROM INFORMATION_SCHEMA.COLUMNS
INNER JOIN
(SELECT TABLE_SCHEMA,
GROUP_CONCAT(COLUMN_NAME ORDER BY SEQ_IN_INDEX ASC) AS COL_NAMES
FROM INFORMATION_SCHEMA.STATISTICS
GROUP BY TABLE_SCHEMA) AS UNIQUES
ON ( COLUMNS.TABLE_SCHEMA = UNIQUES.TABLE_SCHEMA);
COUNT(*) > 0
1
DROP TABLE t1;
set SESSION optimizer_switch= @save_optimizer_switch;
set optimizer_switch=@exit_optimizer_switch;
set join_cache_level=@exit_join_cache_level;

2
mysql-test/r/join_cache.result
View File

@ -5151,7 +5151,7 @@ EXPLAIN
SELECT * FROM (SELECT DISTINCT * FROM t1) t
WHERE t.a IN (SELECT t2.a FROM t2);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY <derived2> ALL key0 NULL NULL NULL 3
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 3
1 PRIMARY t2 ALL NULL NULL NULL NULL 4 Using where; Start temporary; End temporary; Using join buffer (flat, BNL join)
2 DERIVED t1 ALL NULL NULL NULL NULL 3 Using temporary
SELECT * FROM (SELECT DISTINCT * FROM t1) t

34
mysql-test/t/derived_view.test
View File

@ -1313,6 +1313,40 @@ drop table t1,t2,t3;
set SESSION optimizer_switch= @save_optimizer_switch;
--echo #
--echo # LP BUG#944782: derived table from an information schema table
--echo #
SET @save_optimizer_switch=@@optimizer_switch;
SET SESSION optimizer_switch='derived_merge=on';
SET SESSION optimizer_switch='derived_with_keys=on';
CREATE TABLE t1 (c1 int PRIMARY KEY, c2 char(5));
EXPLAIN
SELECT COUNT(*) > 0
FROM INFORMATION_SCHEMA.COLUMNS
INNER JOIN
(SELECT TABLE_SCHEMA,
GROUP_CONCAT(COLUMN_NAME ORDER BY SEQ_IN_INDEX ASC) AS COL_NAMES
FROM INFORMATION_SCHEMA.STATISTICS
GROUP BY TABLE_SCHEMA) AS UNIQUES
ON ( COLUMNS.TABLE_SCHEMA = UNIQUES.TABLE_SCHEMA);
# this query crashed in mariadb-5.5.20
SELECT COUNT(*) > 0
FROM INFORMATION_SCHEMA.COLUMNS
INNER JOIN
(SELECT TABLE_SCHEMA,
GROUP_CONCAT(COLUMN_NAME ORDER BY SEQ_IN_INDEX ASC) AS COL_NAMES
FROM INFORMATION_SCHEMA.STATISTICS
GROUP BY TABLE_SCHEMA) AS UNIQUES
ON ( COLUMNS.TABLE_SCHEMA = UNIQUES.TABLE_SCHEMA);
DROP TABLE t1;
set SESSION optimizer_switch= @save_optimizer_switch;
# The following command must be the last one the file
set optimizer_switch=@exit_optimizer_switch;
set join_cache_level=@exit_join_cache_level;

7
sql/sql_select.cc
View File

@ -8712,8 +8712,13 @@ void JOIN::drop_unused_derived_keys()
continue;
if (table->max_keys > 1)
table->use_index(tab->ref.key);
if (table->s->keys && tab->ref.key >= 0)
if (table->s->keys)
{
if (tab->ref.key >= 0)
tab->ref.key= 0;
else
table->s->keys= 0;
}
tab->keys= (key_map) (table->s->keys ? 1 : 0);
}
}