Commit 170215e6 authored by Evgeny Potemkin's avatar Evgeny Potemkin
Browse files

Bug#37870: Usage of uninitialized value caused failed assertion. 

      
The convert_constant_item function converts a constant to integer using
field for condition like 'field = a_constant'. When the convert_constant_item
is called for a subquery the outer select is already being executed, so
convert_constant_item saves field's value to prevent its corruption.
For EXPLAIN field's value isn't initialized thus when convert_constant_item
tries to restore saved value it fails assertion.
      
Now the convert_constant_item doesn't save/restore field's value
for EXPLAIN.
parent e300184c

mysql-test/r/explain.result

+15 −0
Original line number Diff line number Diff line
@@ -107,3 +107,18 @@ X X X X X X X X X 
X	X	X	X	X	X	X	X	X	Range checked for each record (index map: 0xFFFFFFFFFF)

DROP TABLE t2;

DROP TABLE t1;

#

# Bug#37870: Usage of uninitialized value caused failed assertion.

#

create table t1 (dt datetime not null);

create table t2 (dt datetime not null);

insert into t1 values ('2001-01-01 1:1:1'), ('2001-01-01 1:1:1');

insert into t2 values ('2001-01-01 1:1:1'), ('2001-01-01 1:1:1');

flush tables;

EXPLAIN SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN (SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.dt IS NULL );

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	PRIMARY	OUTR	ALL	NULL	NULL	NULL	NULL	2	Using where

2	DEPENDENT SUBQUERY	INNR	ALL	NULL	NULL	NULL	NULL	2	Using where

SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN (SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.dt IS NULL );

dt

drop tables t1, t2;

mysql-test/t/explain.test

+12 −0
Original line number Diff line number Diff line
@@ -94,4 +94,16 @@ EXPLAIN SELECT 1 FROM 
DROP TABLE t2;

DROP TABLE t1;



--echo #

--echo # Bug#37870: Usage of uninitialized value caused failed assertion.

--echo #

create table t1 (dt datetime not null);

create table t2 (dt datetime not null);

insert into t1 values ('2001-01-01 1:1:1'), ('2001-01-01 1:1:1');

insert into t2 values ('2001-01-01 1:1:1'), ('2001-01-01 1:1:1');

flush tables;

EXPLAIN SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN (SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.dt IS NULL );

SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN (SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.dt IS NULL );

drop tables t1, t2;



# End of 5.0 tests.

sql/item_cmpfunc.cc

+3 −2
Original line number Diff line number Diff line
@@ -415,8 +415,9 @@ static bool convert_constant_item(THD *thd, Item_field *field_item, 
    /*

      Store the value of the field if it references an outer field because

      the call to save_in_field below overrides that value.

      Don't store it for EXPLAIN since it's not initialized.

    */

    if (field_item->depended_from)

    if (field_item->depended_from && !thd->lex->describe)

      orig_field_val= field->val_int();

    if (!(*item)->is_null() && !(*item)->save_in_field(field, 1))

    {
@@ -427,7 +428,7 @@ static bool convert_constant_item(THD *thd, Item_field *field_item, 
      result= 1;					// Item was replaced

    }

    /* Restore the original field value. */

    if (field_item->depended_from)

    if (field_item->depended_from && !thd->lex->describe)

    {

      result= field->store(orig_field_val, TRUE);

      /* orig_field_val must be a valid value that can be restored back. */