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Merge mysql.com:/home/kgeorge/mysql/4.1/B16458

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into  mysql.com:/home/kgeorge/mysql/5.0/B16458


sql/sql_select.cc:
  Auto merged
mysql-test/r/distinct.result:
  merge 4.1->5.0
mysql-test/t/distinct.test:
  merge 4.1->5.0
This commit is contained in:
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2006-06-27 17:59:49 +03:00
parent d0412ab8e0 4b36c1d8ff
commit 6a4ec2e99d
3 changed files with 247 additions and 0 deletions
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51
mysql-test/r/distinct.result
View File

@ -504,6 +504,57 @@ a 2 b
2 2 4
3 2 5
DROP TABLE t1,t2;
CREATE TABLE t1(a INT PRIMARY KEY, b INT);
INSERT INTO t1 VALUES (1,1), (2,1), (3,1);
EXPLAIN SELECT DISTINCT a FROM t1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL PRIMARY 4 NULL 3 Using index
EXPLAIN SELECT DISTINCT a,b FROM t1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 3
EXPLAIN SELECT DISTINCT t1_1.a, t1_1.b FROM t1 t1_1, t1 t1_2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1_1 ALL NULL NULL NULL NULL 3 Using temporary
1 SIMPLE t1_2 index NULL PRIMARY 4 NULL 3 Using index; Distinct
EXPLAIN SELECT DISTINCT t1_1.a, t1_1.b FROM t1 t1_1, t1 t1_2
WHERE t1_1.a = t1_2.a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1_1 ALL PRIMARY NULL NULL NULL 3 Using temporary
1 SIMPLE t1_2 eq_ref PRIMARY PRIMARY 4 test.t1_1.a 1 Using index; Distinct
EXPLAIN SELECT a FROM t1 GROUP BY a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL PRIMARY 4 NULL 3 Using index
EXPLAIN SELECT a,b FROM t1 GROUP BY a,b;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 3
EXPLAIN SELECT DISTINCT a,b FROM t1 GROUP BY a,b;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 3
CREATE TABLE t2(a INT, b INT, c INT, d INT, PRIMARY KEY (a,b));
INSERT INTO t2 VALUES (1,1,1,50), (1,2,3,40), (2,1,3,4);
EXPLAIN SELECT DISTINCT a FROM t2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 index NULL PRIMARY 8 NULL 3 Using index
EXPLAIN SELECT DISTINCT a,a FROM t2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 index NULL PRIMARY 8 NULL 3 Using index; Using temporary
EXPLAIN SELECT DISTINCT b,a FROM t2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 index NULL PRIMARY 8 NULL 3 Using index
EXPLAIN SELECT DISTINCT a,c FROM t2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 3 Using temporary
EXPLAIN SELECT DISTINCT c,a,b FROM t2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 3
EXPLAIN SELECT DISTINCT a,b,d FROM t2 GROUP BY c,b,d;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 3 Using temporary; Using filesort
CREATE UNIQUE INDEX c_b_unq ON t2 (c,b);
EXPLAIN SELECT DISTINCT a,b,d FROM t2 GROUP BY c,b,d;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 3
DROP TABLE t1,t2;
create table t1 (id int, dsc varchar(50));
insert into t1 values (1, "line number one"), (2, "line number two"), (3, "line number three");
select distinct id, IFNULL(dsc, '-') from t1;

28
mysql-test/t/distinct.test
View File

@ -348,6 +348,34 @@ SELECT DISTINCT a, b, 2 FROM t2;
SELECT DISTINCT 2, a, b FROM t2;
SELECT DISTINCT a, 2, b FROM t2;
DROP TABLE t1,t2;
#
# Bug#16458: Simple SELECT FOR UPDATE causes "Result Set not updatable"
# error.
#
CREATE TABLE t1(a INT PRIMARY KEY, b INT);
INSERT INTO t1 VALUES (1,1), (2,1), (3,1);
EXPLAIN SELECT DISTINCT a FROM t1;
EXPLAIN SELECT DISTINCT a,b FROM t1;
EXPLAIN SELECT DISTINCT t1_1.a, t1_1.b FROM t1 t1_1, t1 t1_2;
EXPLAIN SELECT DISTINCT t1_1.a, t1_1.b FROM t1 t1_1, t1 t1_2
WHERE t1_1.a = t1_2.a;
EXPLAIN SELECT a FROM t1 GROUP BY a;
EXPLAIN SELECT a,b FROM t1 GROUP BY a,b;
EXPLAIN SELECT DISTINCT a,b FROM t1 GROUP BY a,b;
CREATE TABLE t2(a INT, b INT, c INT, d INT, PRIMARY KEY (a,b));
INSERT INTO t2 VALUES (1,1,1,50), (1,2,3,40), (2,1,3,4);
EXPLAIN SELECT DISTINCT a FROM t2;
EXPLAIN SELECT DISTINCT a,a FROM t2;
EXPLAIN SELECT DISTINCT b,a FROM t2;
EXPLAIN SELECT DISTINCT a,c FROM t2;
EXPLAIN SELECT DISTINCT c,a,b FROM t2;
EXPLAIN SELECT DISTINCT a,b,d FROM t2 GROUP BY c,b,d;
CREATE UNIQUE INDEX c_b_unq ON t2 (c,b);
EXPLAIN SELECT DISTINCT a,b,d FROM t2 GROUP BY c,b,d;
DROP TABLE t1,t2;
# Bug 9784 DISTINCT IFNULL truncates data

168
sql/sql_select.cc
View File

@ -163,6 +163,10 @@ static Item* part_of_refkey(TABLE *form,Field *field);
uint find_shortest_key(TABLE *table, const key_map *usable_keys);
static bool test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,
ha_rows select_limit, bool no_changes);
static bool list_contains_unique_index(TABLE *table,
bool (*find_func) (Field *, void *), void *data);
static bool find_field_in_item_list (Field *field, void *data);
static bool find_field_in_order_list (Field *field, void *data);
static int create_sort_index(THD *thd, JOIN *join, ORDER *order,
ha_rows filesort_limit, ha_rows select_limit);
static int remove_duplicates(JOIN *join,TABLE *entry,List<Item> &fields,
@ -858,6 +862,36 @@ 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)
{
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
@ -11209,6 +11243,140 @@ test_if_subkey(ORDER *order, TABLE *table, uint ref, uint ref_key_parts,
return best;
}
/*
Check if GROUP BY/DISTINCT can be optimized away because the set is
already known to be distinct.
SYNOPSIS
list_contains_unique_index ()
table The table to operate on.
find_func function to iterate over the list and search
for a field
DESCRIPTION
Used in removing the GROUP BY/DISTINCT of the following types of
statements:
SELECT [DISTINCT] <unique_key_cols>... FROM <single_table_ref>
[GROUP BY <unique_key_cols>,...]
If (a,b,c is distinct)
then <any combination of a,b,c>,{whatever} is also distinct
This function checks if all the key parts of any of the unique keys
of the table are referenced by a list : either the select list
through find_field_in_item_list or GROUP BY list through
find_field_in_order_list.
If the above holds then we can safely remove the GROUP BY/DISTINCT,
as no result set can be more distinct than an unique key.
RETURN VALUE
1 found
0 not found.
*/
static bool
list_contains_unique_index(TABLE *table,
bool (*find_func) (Field *, void *), void *data)
{
for (uint keynr= 0; keynr < table->keys; keynr++)
{
if (keynr == table->primary_key ||
(table->key_info[keynr].flags & HA_NOSAME))
{
KEY *keyinfo= table->key_info + keynr;
KEY_PART_INFO *key_part, *key_part_end;
for (key_part=keyinfo->key_part,
key_part_end=key_part+ keyinfo->key_parts;
key_part < key_part_end;
key_part++)
{
if (!find_func(key_part->field, data))
break;
}
if (key_part == key_part_end)
return 1;
}
}
return 0;
}
/*
Helper function for list_contains_unique_index.
Find a field reference in a list of ORDER structures.
SYNOPSIS
find_field_in_order_list ()
field The field to search for.
data ORDER *.The list to search in
DESCRIPTION
Finds a direct reference of the Field in the list.
RETURN VALUE
1 found
0 not found.
*/
static bool
find_field_in_order_list (Field *field, void *data)
{
ORDER *group= (ORDER *) data;
bool part_found= 0;
for (ORDER *tmp_group= group; tmp_group; tmp_group=tmp_group->next)
{
Item *item= (*tmp_group->item)->real_item();
if (item->type() == Item::FIELD_ITEM &&
((Item_field*) item)->field->eq(field))
{
part_found= 1;
break;
}
}
return part_found;
}
/*
Helper function for list_contains_unique_index.
Find a field reference in a dynamic list of Items.
SYNOPSIS
find_field_in_item_list ()
field in The field to search for.
data in List<Item> *.The list to search in
DESCRIPTION
Finds a direct reference of the Field in the list.
RETURN VALUE
1 found
0 not found.
*/
static bool
find_field_in_item_list (Field *field, void *data)
{
List<Item> *fields= (List<Item> *) data;
bool part_found= 0;
List_iterator<Item> li(*fields);
Item *item;
while ((item= li++))
{
if (item->type() == Item::FIELD_ITEM &&
((Item_field*) item)->field->eq(field))
{
part_found= 1;
break;
}
}
return part_found;
}
/*
Test if we can skip the ORDER BY by using an index.