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Merge gkodinov@bk-internal.mysql.com:/home/bk/mysql-5.0-opt

Browse source 
into  rakia.gmz:/home/kgeorge/mysql/autopush/B25551-5.0-opt
This commit is contained in:
gkodinov/kgeorge@rakia.gmz 2007-02-01 10:50:41 +02:00
commit 0d40608fff
3 changed files with 52 additions and 10 deletions
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26
mysql-test/r/distinct.result
View file

@ -530,7 +530,8 @@ id select_type table type possible_keys key key_len ref rows Extra
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));
CREATE TABLE t2(a INT, b INT NOT NULL, c INT NOT NULL, 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
@ -644,3 +645,26 @@ SELECT COUNT(*) FROM
COUNT(*)
2
DROP TABLE t1, t2;
CREATE TABLE t1 (a INT, UNIQUE (a));
INSERT INTO t1 VALUES (4),(null),(2),(1),(null),(3);
EXPLAIN SELECT DISTINCT a FROM t1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL a 5 NULL 6 Using index
SELECT DISTINCT a FROM t1;
a
NULL
1
2
3
4
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 a 5 NULL 6 Using index
SELECT a FROM t1 GROUP BY a;
a
NULL
1
2
3
4
DROP TABLE t1;

17
mysql-test/t/distinct.test
View file

@ -364,7 +364,8 @@ 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));
CREATE TABLE t2(a INT, b INT NOT NULL, c INT NOT NULL, 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;
@ -525,3 +526,17 @@ SELECT COUNT(*) FROM
(SELECT DISTINCT a FROM t2 WHERE a='oe' COLLATE latin1_german2_ci) dt;
DROP TABLE t1, t2;
#
# Bug #25551: inconsistent behaviour in grouping NULL, depending on index type
#
CREATE TABLE t1 (a INT, UNIQUE (a));
INSERT INTO t1 VALUES (4),(null),(2),(1),(null),(3);
EXPLAIN SELECT DISTINCT a FROM t1;
#result must have one row with NULL
SELECT DISTINCT a FROM t1;
EXPLAIN SELECT a FROM t1 GROUP BY a;
#result must have one row with NULL
SELECT a FROM t1 GROUP BY a;
DROP TABLE t1;

19
sql/sql_select.cc
View file

@ -873,10 +873,11 @@ JOIN::optimize()
}
/*
Check if we can optimize away GROUP BY/DISTINCT.
We can do that if there are no aggregate functions and the
We can do that if there are no aggregate functions, 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).
an unique index (in whatever order) and if the key parts of the
unique index cannot contain NULLs.
Note that the unique keys for DISTINCT and GROUP BY should not
be the same (as long as they are unique).
@ -11896,7 +11897,7 @@ test_if_subkey(ORDER *order, TABLE *table, uint ref, uint ref_key_parts,
/*
Check if GROUP BY/DISTINCT can be optimized away because the set is
Check if GROUP BY/DISTINCT can be optimized away because the set is
already known to be distinct.
SYNOPSIS
@ -11904,7 +11905,7 @@ test_if_subkey(ORDER *order, TABLE *table, uint ref, uint ref_key_parts,
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:
@ -11915,12 +11916,13 @@ test_if_subkey(ORDER *order, TABLE *table, uint ref, uint ref_key_parts,
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
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,
If the above holds and the key parts cannot contain NULLs 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.
@ -11943,7 +11945,8 @@ list_contains_unique_index(TABLE *table,
key_part < key_part_end;
key_part++)
{
if (!find_func(key_part->field, data))
if (key_part->field->maybe_null() ||
!find_func(key_part->field, data))
break;
}
if (key_part == key_part_end)