Commit e3181c59 authored by unknown's avatar unknown
Browse files

Merge lamia.home:/home/timka/mysql/src/4.1-bug-21456 

into  lamia.home:/home/timka/mysql/src/5.0-bug-21456


mysql-test/r/distinct.result:
  Merge the fix for BUG#21456
mysql-test/t/distinct.test:
  Merge the fix for BUG#21456
sql/sql_select.cc:
  Merge the fix for BUG#21456
parents 5c8c2ab4 2baf2fdf

mysql-test/r/distinct.result

+11 −0
Original line number Diff line number Diff line
@@ -563,6 +563,17 @@ id IFNULL(dsc, '-') 
2	line number two

3	line number three

drop table t1;

CREATE TABLE t1 (a int primary key, b int);

INSERT INTO t1 (a,b) values (1,1), (2,3), (3,2);

explain SELECT DISTINCT a, b FROM t1 ORDER BY b;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	Using filesort

SELECT DISTINCT a, b FROM t1 ORDER BY b;

a	b

1	1

3	2

2	3

DROP TABLE t1;

CREATE TABLE t1 (

ID int(11) NOT NULL auto_increment,

x varchar(20) default NULL,

mysql-test/t/distinct.test

+11 −0
Original line number Diff line number Diff line
@@ -385,6 +385,17 @@ insert into t1 values (1, "line number one"), (2, "line number two"), (3, "line 
select distinct id, IFNULL(dsc, '-') from t1;

drop table t1;



#

# Bug 21456: SELECT DISTINCT(x) produces incorrect results when using order by

#

CREATE TABLE t1 (a int primary key, b int);



INSERT INTO t1 (a,b) values (1,1), (2,3), (3,2);



explain SELECT DISTINCT a, b FROM t1 ORDER BY b;

SELECT DISTINCT a, b FROM t1 ORDER BY b;

DROP TABLE t1;



# End of 4.1 tests

sql/sql_select.cc

+34 −34
Original line number Diff line number Diff line
@@ -812,6 +812,40 @@ JOIN::optimize() 
    if (!order && org_order)

      skip_sort_order= 1;

  }

  /*

     Check if we can optimize away GROUP BY/DISTINCT.

     We can do that if there are no aggregate functions and the

     fields in DISTINCT clause (if present) and/or columns in GROUP BY

     (if present) contain direct references to all key parts of

     an unique index (in whatever order).

     Note that the unique keys for DISTINCT and GROUP BY should not

     be the same (as long as they are unique).



     The FROM clause must contain a single non-constant table.

  */

  if (tables - const_tables == 1 && (group_list || select_distinct) &&

      !tmp_table_param.sum_func_count &&

      (!join_tab[const_tables].select ||

       !join_tab[const_tables].select->quick ||

       join_tab[const_tables].select->quick->get_type() != 

       QUICK_SELECT_I::QS_TYPE_GROUP_MIN_MAX))

  {

    if (group_list &&

       list_contains_unique_index(join_tab[const_tables].table,

                                 find_field_in_order_list,

                                 (void *) group_list))

    {

      group_list= 0;

      group= 0;

    }

    if (select_distinct &&

       list_contains_unique_index(join_tab[const_tables].table,

                                 find_field_in_item_list,

                                 (void *) &fields_list))

    {

      select_distinct= 0;

    }

  }

  if (group_list || tmp_table_param.sum_func_count)

  {

    if (! hidden_group_fields && rollup.state == ROLLUP::STATE_NONE)
@@ -881,40 +915,6 @@ JOIN::optimize() 
    if (old_group_list && !group_list)

      select_distinct= 0;

  }

  /*

     Check if we can optimize away GROUP BY/DISTINCT.

     We can do that if there are no aggregate functions and the

     fields in DISTINCT clause (if present) and/or columns in GROUP BY

     (if present) contain direct references to all key parts of

     an unique index (in whatever order).

     Note that the unique keys for DISTINCT and GROUP BY should not

     be the same (as long as they are unique).



     The FROM clause must contain a single non-constant table.

  */

  if (tables - const_tables == 1 && (group_list || select_distinct) &&

      !tmp_table_param.sum_func_count &&

      (!join_tab[const_tables].select ||

       !join_tab[const_tables].select->quick ||

       join_tab[const_tables].select->quick->get_type() != 

       QUICK_SELECT_I::QS_TYPE_GROUP_MIN_MAX))

  {

    if (group_list &&

       list_contains_unique_index(join_tab[const_tables].table,

                                 find_field_in_order_list,

                                 (void *) group_list))

    {

      group_list= 0;

      group= 0;

    }

    if (select_distinct &&

       list_contains_unique_index(join_tab[const_tables].table,

                                 find_field_in_item_list,

                                 (void *) &fields_list))

    {

      select_distinct= 0;

    }

  }

  if (!group_list && group)

  {

    order=0;					// The output has only one row