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Fix bug lp:806943

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Analysis:
This bug is yet another incarnation of the generic problem
where optimization of the outer query triggers evaluation
of a subquery, and this evaluation performs a destructive
change to the subquery plan. Specifically a temp table is
created for the DISTINCT operation that replaces the
original subquery table. Later, select_describe() attempts
to print the table name, however, there is no corresponding
TABLE_LIST object to the internal temp table, so we get a
crash. Execution works fine because it is not interested in
the corresponding TABLE_LIST object (or its name).

Solution:
Similar to other such bugs, block the evaluation of expensive
Items in convert_const_to_int().
This commit is contained in:
unknown 2011-07-07 16:28:26 +03:00
parent 801a4ebca9
commit 4128ec4852
3 changed files with 65 additions and 1 deletions
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31
mysql-test/r/subselect4.result
View file

@ -1784,4 +1784,35 @@ WHERE EXISTS (SELECT DISTINCT f1 FROM t4) LIMIT 1)
AND t2.f2 = t1.f1;
f1 f2 f1 f2
drop table t1,t2,t3,t4;
#
# LP BUG#806943 Second crash with select_describe with nested subqueries in maria-5.3
#
CREATE TABLE t1 ( f4 int) ;
INSERT INTO t1 VALUES (0),(0);
CREATE TABLE t2 ( f2 int) ;
CREATE TABLE t3 ( f1 int NOT NULL );
CREATE TABLE t4 ( f2 int, f3 int) ;
INSERT INTO t4 VALUES (8,0),(3,0);
EXPLAIN SELECT *
FROM t2, t3
WHERE t3.f1 = (
SELECT SUM( f2 )
FROM t4
WHERE EXISTS (
SELECT DISTINCT f4
FROM t1));
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 t4 ALL NULL NULL NULL NULL 2
3 SUBQUERY t1 ALL NULL NULL NULL NULL 2 Using temporary
SELECT *
FROM t2, t3
WHERE t3.f1 = (
SELECT SUM( f2 )
FROM t4
WHERE EXISTS (
SELECT DISTINCT f4
FROM t1));
f2 f1
drop table t1, t2, t3, t4;
set optimizer_switch=@subselect4_tmp;

33
mysql-test/t/subselect4.test
View file

@ -1461,4 +1461,37 @@ WHERE t2.f2 = (SELECT f2 FROM t3
drop table t1,t2,t3,t4;
--echo #
--echo # LP BUG#806943 Second crash with select_describe with nested subqueries in maria-5.3
--echo #
CREATE TABLE t1 ( f4 int) ;
INSERT INTO t1 VALUES (0),(0);
CREATE TABLE t2 ( f2 int) ;
CREATE TABLE t3 ( f1 int NOT NULL );
CREATE TABLE t4 ( f2 int, f3 int) ;
INSERT INTO t4 VALUES (8,0),(3,0);
EXPLAIN SELECT *
FROM t2, t3
WHERE t3.f1 = (
SELECT SUM( f2 )
FROM t4
WHERE EXISTS (
SELECT DISTINCT f4
FROM t1));
SELECT *
FROM t2, t3
WHERE t3.f1 = (
SELECT SUM( f2 )
FROM t4
WHERE EXISTS (
SELECT DISTINCT f4
FROM t1));
drop table t1, t2, t3, t4;
set optimizer_switch=@subselect4_tmp;

2
sql/item_cmpfunc.cc
View file

@ -434,7 +434,7 @@ static bool convert_const_to_int(THD *thd, Item_field *field_item,
field_item->field_type() != MYSQL_TYPE_YEAR)
return 1;
if ((*item)->const_item())
if ((*item)->const_item() && !(*item)->is_expensive())
{
TABLE *table= field->table;
ulong orig_sql_mode= thd->variables.sql_mode;