Commit b5c119e7 authored by unknown's avatar unknown
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Fix for BUG#6976: 

In Item_ref::Item_ref set maybe_null (and other fields fix_fields sets) to be the 
same as in (*ref), because Item_ref::fix_fields() will not be called.  Previously 
maybe_null was 0 always and this produced a bogus state where 
maybe_null==0 && is_null() == true 
which broke evaluation for some upper-level Items, like AND and OR.


mysql-test/r/group_by.result:
  Test for BUG#6976
mysql-test/t/group_by.test:
  Test for BUG#6976
sql/item.cc:
  Comment added
sql/item.h:
  Fix for BUG#6976:
    in Item_ref::Item_ref(Item**...) fix all fields because fix_fields() will not be called.
parent 9286d1c1

mysql-test/r/group_by.result

+12 −0
Original line number Diff line number Diff line
@@ -626,3 +626,15 @@ explain SELECT i, COUNT(DISTINCT(i)) FROM t1 GROUP BY j ORDER BY NULL; 
table	type	possible_keys	key	key_len	ref	rows	Extra

t1	ALL	NULL	NULL	NULL	NULL	6	Using filesort

DROP TABLE t1;

create table t1 (a int);

insert into t1 values(null);

select min(a) is null from t1;

min(a) is null

1

select min(a) is null or null from t1;

min(a) is null or null

1

select 1 and min(a) is null from t1;

1 and min(a) is null

1

drop table t1;

mysql-test/t/group_by.test

+9 −0
Original line number Diff line number Diff line
@@ -447,3 +447,12 @@ INSERT INTO t1 VALUES (1,2),(2,3),(4,5),(3,5),(1,5),(23,5); 
SELECT i, COUNT(DISTINCT(i)) FROM t1 GROUP BY j ORDER BY NULL;

explain SELECT i, COUNT(DISTINCT(i)) FROM t1 GROUP BY j ORDER BY NULL;

DROP TABLE t1;



#Test for BUG#6976: Aggregate functions have incorrect NULL-ness

create table t1 (a int);

insert into t1 values(null);

select min(a) is null from t1;

select min(a) is null or null from t1;

select 1 and min(a) is null from t1;

drop table t1;

sql/item.cc

+1 −0
Original line number Diff line number Diff line
@@ -687,6 +687,7 @@ bool Item_null::send(THD *thd, String *packet) 
/*

  This is used for HAVING clause

  Find field in select list having the same name

  This is not always called, see also Item_ref::Item_ref

 */



bool Item_ref::fix_fields(THD *thd,TABLE_LIST *tables)

sql/item.h

+13 −1
Original line number Diff line number Diff line
@@ -401,7 +401,19 @@ class Item_ref :public Item_ident 
  Item_ref(char *db_par,char *table_name_par,char *field_name_par)

    :Item_ident(db_par,table_name_par,field_name_par),ref(0) {}

  Item_ref(Item **item, char *table_name_par,char *field_name_par)

    :Item_ident(NullS,table_name_par,field_name_par),ref(item) {}

    :Item_ident(NullS,table_name_par,field_name_par),ref(item)

  {

    /*

      This ctor is called from Item_XXX::split_sum_func, and fix_fields will

      not be called for *this, so we must setup everything here. **ref is 

      already fixed at this point.

    */

    max_length= (*ref)->max_length;

    decimals=	(*ref)->decimals;

    binary=	(*ref)->binary;

    with_sum_func= (*ref)->with_sum_func;

    maybe_null= (*ref)->maybe_null;

  }

  enum Type type() const		{ return REF_ITEM; }

  bool eq(const Item *item, bool binary_cmp) const

  { return (*ref)->eq(item, binary_cmp); }