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

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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.
This commit is contained in:
Evgeny Potemkin 2008-10-27 12:26:32 +03:00
parent e300184c01
commit 170215e696
3 changed files with 30 additions and 2 deletions
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15
mysql-test/r/explain.result
View File

@ -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) X X X X X X X X X Range checked for each record (index map: 0xFFFFFFFFFF)
DROP TABLE t2; DROP TABLE t2;
DROP TABLE t1; 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;

12
mysql-test/t/explain.test
View File

@ -94,4 +94,16 @@ EXPLAIN SELECT 1 FROM
DROP TABLE t2; DROP TABLE t2;
DROP TABLE t1; 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. # End of 5.0 tests.

5
sql/item_cmpfunc.cc
View File

@ -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 Store the value of the field if it references an outer field because
the call to save_in_field below overrides that value. 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(); orig_field_val= field->val_int();
if (!(*item)->is_null() && !(*item)->save_in_field(field, 1)) 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 result= 1; // Item was replaced
} }
/* Restore the original field value. */ /* 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); result= field->store(orig_field_val, TRUE);
/* orig_field_val must be a valid value that can be restored back. */ /* orig_field_val must be a valid value that can be restored back. */