Commit f3726418 authored by unknown's avatar unknown
Browse files

Fix for bug #17896: MIN of CASE WHEN returns non-minimum value! 


sql/item_cmpfunc.cc:
  Fix for bug #17896: MIN of CASE WHEN returns non-minimum value!
  - NULL items should not affect the result type.
parent 4391f938

mysql-test/r/case.result

+8 −0
Original line number Diff line number Diff line
@@ -169,3 +169,11 @@ SELECT CASE '1' WHEN '2' THEN 'BUG' ELSE 'nobug' END; 
case+union+test

case+union+test

nobug

create table t1(a float, b int default 3);

insert into t1 (a) values (2), (11), (8);

select min(a), min(case when 1=1 then a else NULL end),

min(case when 1!=1 then NULL else a end) 

from t1 where b=3 group by b;

min(a)	min(case when 1=1 then a else NULL end)	min(case when 1!=1 then NULL else a end)

2	2	2

drop table t1;

mysql-test/t/case.test

+11 −0
Original line number Diff line number Diff line
@@ -119,4 +119,15 @@ SELECT 'case+union+test' 
UNION 

SELECT CASE '1' WHEN '2' THEN 'BUG' ELSE 'nobug' END;



#

# Bug #17896: problem with MIN(CASE...)

#



create table t1(a float, b int default 3);

insert into t1 (a) values (2), (11), (8);

select min(a), min(case when 1=1 then a else NULL end),

  min(case when 1!=1 then NULL else a end) 

from t1 where b=3 group by b;

drop table t1;



# End of 4.1 tests

sql/item_cmpfunc.cc

+15 −4
Original line number Diff line number Diff line
@@ -37,10 +37,21 @@ static Item_result item_store_type(Item_result a,Item_result b) 


static void agg_result_type(Item_result *type, Item **items, uint nitems)

{

  uint i;

  type[0]= items[0]->result_type();

  for (i=1 ; i < nitems ; i++)

    type[0]= item_store_type(type[0], items[i]->result_type());

  Item **item, **item_end;



  /* Note: NULL items don't affect the result type */

  *type= STRING_RESULT;

  /* Skip beginning NULL items */

  for (item= items, item_end= item + nitems; item < item_end; item++)

    if ((*item)->type() != Item::NULL_ITEM)

    {

      *type= (*item)->result_type();

      item++;

      break;

    }

  for (; item < item_end; item++)

    if ((*item)->type() != Item::NULL_ITEM)

      *type= item_store_type(type[0], (*item)->result_type());

}



static void agg_cmp_type(Item_result *type, Item **items, uint nitems)