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Bug#48920: COUNT DISTINCT returns 1 for NULL values when in a

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subquery in the select list
      
When a dependent subquery with count(distinct <col>) was 
evaluated multiple times, the Distinct_Aggregator was reused. 
However, the Aggregator was not reset, so when the subquery was
evaluated for the next record in the outer select, old dependent
info was used.
      
The fix is to clear() the existing aggregator in 
Item_sum::set_aggregator(). This ensures that the aggregator is
reevaluated with the new dependent information.
This commit is contained in:
Jorgen Loland
2010-01-04 10:39:42 +01:00
parent 8050affe24
commit 3dab08f157
3 changed files with 104 additions and 0 deletions
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47
mysql-test/t/subselect3.test
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@@ -794,3 +794,50 @@ SHOW STATUS LIKE '%Handler_read_rnd_next';
DROP TABLE t1,t2;
--echo End of 5.1 tests
--echo #
--echo # BUG#48920: COUNT DISTINCT returns 1 for NULL values when in a subquery
--echo # in the select list
--echo #
--echo
CREATE TABLE t1 (
i int(11) DEFAULT NULL,
v varchar(1) DEFAULT NULL
);
--echo
INSERT INTO t1 VALUES (8,'v');
INSERT INTO t1 VALUES (9,'r');
INSERT INTO t1 VALUES (NULL,'y');
--echo
CREATE TABLE t2 (
i int(11) DEFAULT NULL,
v varchar(1) DEFAULT NULL,
KEY i_key (i)
);
--echo
INSERT INTO t2 VALUES (NULL,'r');
INSERT INTO t2 VALUES (0,'c');
INSERT INTO t2 VALUES (0,'o');
INSERT INTO t2 VALUES (2,'v');
INSERT INTO t2 VALUES (7,'c');
--echo
SELECT i, v, (SELECT COUNT(DISTINCT i)
FROM t1
WHERE v = t2.v) as subsel
FROM t2;
--echo
EXPLAIN EXTENDED
SELECT i, v, (SELECT COUNT(DISTINCT i)
FROM t1
WHERE v = t2.v) as subsel
FROM t2;
DROP TABLE t1,t2;
--echo End of 5.6 tests