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

Browse source 
into  lamia.home:/home/timka/mysql/src/5.1-bug-21456
This commit is contained in:
timour/timka@lamia.home 2006-08-29 16:39:09 +03:00
commit 0368914b9a
3 changed files with 56 additions and 34 deletions
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11
mysql-test/r/distinct.result
View file

@ -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,

11
mysql-test/t/distinct.test
View file

@ -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

68
sql/sql_select.cc
View file

@ -822,6 +822,40 @@ 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)
@ -891,40 +925,6 @@ 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