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Fixed bug #15633: Evaluation of Item_equal for non-const table caused wrong

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select result

Item equal objects are employed only at the optimize phase. Usually they are not
supposed to be evaluated.  Yet in some cases we call the method val_int() for
them. Here we have to take care of restricting the predicate such an object
represents f1=f2= ...=fn to the projection of known fields fi1=...=fik.

Added a check for field's table being const in Item_equal::val_int().
If the field's table is not const val_int() just skips that field when
evaluating Item_equal.
This commit is contained in:
evgen@moonbone.local 2006-01-11 22:49:43 +03:00
parent c34595c975
commit 605f62fce8
5 changed files with 42 additions and 3 deletions
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2
mysql-test/r/func_group.result
View file

@ -865,6 +865,7 @@ select 1, min(a) from t1m where 1=99;
1 NULL
select 1, min(1) from t1m where a=99;
1 min(1)
1 NULL
select 1, min(1) from t1m where 1=99;
1 min(1)
1 NULL
@ -876,6 +877,7 @@ select 1, max(a) from t1m where 1=99;
1 NULL
select 1, max(1) from t1m where a=99;
1 max(1)
1 NULL
select 1, max(1) from t1m where 1=99;
1 max(1)
1 NULL

13
mysql-test/r/select.result
View file

@ -3337,3 +3337,16 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 const PRIMARY PRIMARY 4 const 1 Using index
1 SIMPLE t3 const PRIMARY PRIMARY 8 const,const 1
DROP TABLE t1,t2,t3;
create table t1 (f1 int unique);
create table t2 (f2 int unique);
create table t3 (f3 int unique);
insert into t1 values(1),(2);
insert into t2 values(1),(2);
insert into t3 values(1),(NULL);
select * from t3 where f3 is null;
f3
NULL
select t2.f2 from t1 left join t2 on f1=f2 join t3 on f1=f3 where f1=1;
f2
1
drop table t1,t2,t3;

14
mysql-test/t/select.test
View file

@ -2805,3 +2805,17 @@ EXPLAIN SELECT t2.key_a,foo
WHERE t2.key_a=2 and key_b=5;
DROP TABLE t1,t2,t3;
#
# Bug #15633 Evaluation of Item_equal for non-const table caused wrong
# select result
#
create table t1 (f1 int unique);
create table t2 (f2 int unique);
create table t3 (f3 int unique);
insert into t1 values(1),(2);
insert into t2 values(1),(2);
insert into t3 values(1),(NULL);
select * from t3 where f3 is null;
select t2.f2 from t1 left join t2 on f1=f2 join t3 on f1=f3 where f1=1;
drop table t1,t2,t3;

9
sql/item_cmpfunc.cc
View file

@ -3765,6 +3765,7 @@ void Item_equal::update_used_tables()
longlong Item_equal::val_int()
{
Item_field *item_field;
if (cond_false)
return 0;
List_iterator_fast<Item_field> it(fields);
@ -3772,11 +3773,15 @@ longlong Item_equal::val_int()
if ((null_value= item->null_value))
return 0;
eval_item->store_value(item);
while ((item= it++))
while ((item_field= it++))
{
if ((null_value= item->null_value) || eval_item->cmp(item))
/* Skip fields of non-const tables. They haven't been read yet */
if (item_field->field->table->const_table)
{
if ((null_value= item_field->null_value) || eval_item->cmp(item_field))
return 0;
}
}
return 1;
}

5
sql/item_cmpfunc.h
View file

@ -1150,6 +1150,11 @@ public:
are deleted in the end of execution. All changes made to these
objects need not be registered in the list of changes of the parse
tree and do not harm PS/SP re-execution.
Item equal objects are employed only at the optimize phase. Usually they are
not supposed to be evaluated. Yet in some cases we call the method val_int()
for them. We have to take care of restricting the predicate such an
object represents f1=f2= ...=fn to the projection of known fields fi1=...=fik.
*/
class Item_equal: public Item_bool_func