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Bug #48419: another explain crash..

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WHERE predicates containing references to empty tables in a
subquery were handled incorrectly by the optimizer when
executing EXPLAIN. As a result, the optimizer could try to
evaluate such predicates rather than just stop with
"Impossible WHERE noticed after reading const tables" as 
it would do in a non-subquery case. This led to valgrind 
errors and crashes.

Fixed the code checking the above condition so that subqueries
are not excluded and hence are handled in the same way as top
level SELECTs.
This commit is contained in:
Alexey Kopytov 2010-04-30 15:10:48 +04:00
parent 8a96640e87
commit 96366e1196
4 changed files with 34 additions and 8 deletions
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12
mysql-test/r/explain.result
View File

@ -226,4 +226,16 @@ Warnings:
Note 1276 Field or reference 'test.t1.c' of SELECT #2 was resolved in SELECT #1
Note 1003 select (select 1 from `test`.`t2` where (`test`.`t2`.`d` = NULL)) AS `(SELECT 1 FROM t2 WHERE d = c)` from `test`.`t1`
DROP TABLE t1, t2;
#
# Bug #48419: another explain crash..
#
CREATE TABLE t1 (a INT);
CREATE TABLE t2 (b BLOB, KEY b(b(100)));
INSERT INTO t2 VALUES ('1'), ('2'), ('3');
FLUSH TABLES;
EXPLAIN SELECT 1 FROM t1 WHERE a = (SELECT 1 FROM t1 t JOIN t2 WHERE b <= 1 AND t.a);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
DROP TABLE t1, t2;
End of 5.1 tests.

12
mysql-test/r/ps.result
View File

@ -155,24 +155,24 @@ execute stmt1 ;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
6 DERIVED NULL NULL NULL NULL NULL NULL NULL no matching row in const table
5 DEPENDENT SUBQUERY t2 system NULL NULL NULL NULL 0 const row not found
4 DEPENDENT SUBQUERY t2 system NULL NULL NULL NULL 0 const row not found
5 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
4 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
3 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
2 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
execute stmt1 ;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
6 DERIVED NULL NULL NULL NULL NULL NULL NULL no matching row in const table
5 DEPENDENT SUBQUERY t2 system NULL NULL NULL NULL 0 const row not found
4 DEPENDENT SUBQUERY t2 system NULL NULL NULL NULL 0 const row not found
5 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
4 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
3 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
2 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
explain SELECT (SELECT SUM(c1 + c12 + 0.0) FROM t2 where (t1.c2 - 0e-3) = t2.c2 GROUP BY t1.c15 LIMIT 1) as scalar_s, exists (select 1.0e+0 from t2 where t2.c3 * 9.0000000000 = t1.c4) as exists_s, c5 * 4 in (select c6 + 0.3e+1 from t2) as in_s, (c7 - 4, c8 - 4) in (select c9 + 4.0, c10 + 40e-1 from t2) as in_row_s FROM t1, (select c25 x, c32 y from t2) tt WHERE x * 1 = c25;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
6 DERIVED NULL NULL NULL NULL NULL NULL NULL no matching row in const table
5 DEPENDENT SUBQUERY t2 system NULL NULL NULL NULL 0 const row not found
4 DEPENDENT SUBQUERY t2 system NULL NULL NULL NULL 0 const row not found
5 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
4 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
3 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
2 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
deallocate prepare stmt1;

15
mysql-test/t/explain.test
View File

@ -198,4 +198,19 @@ INSERT INTO t2 VALUES (NULL), (0);
EXPLAIN EXTENDED SELECT (SELECT 1 FROM t2 WHERE d = c) FROM t1;
DROP TABLE t1, t2;
--echo #
--echo # Bug #48419: another explain crash..
--echo #
CREATE TABLE t1 (a INT);
CREATE TABLE t2 (b BLOB, KEY b(b(100)));
INSERT INTO t2 VALUES ('1'), ('2'), ('3');
FLUSH TABLES;
EXPLAIN SELECT 1 FROM t1 WHERE a = (SELECT 1 FROM t1 t JOIN t2 WHERE b <= 1 AND t.a);
DROP TABLE t1, t2;
--echo End of 5.1 tests.

3
sql/sql_select.cc
View File

@ -1107,8 +1107,7 @@ JOIN::optimize()
}
if (conds && const_table_map != found_const_table_map &&
(select_options & SELECT_DESCRIBE) &&
select_lex->master_unit() == &thd->lex->unit) // upper level SELECT
(select_options & SELECT_DESCRIBE))
{
conds=new Item_int((longlong) 0,1); // Always false
}