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Bug #47904 Incorrect results w/ table subquery, derived SQs, and LEFT JOIN

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on index

'my_decimal' class has two members which can be used to access the 
value. The member variable buf (inherited from parent class decimal_t) 
is set to member variable buffer so that both are pointing to same value.

Item_copy_decimal::copy() uses memcpy to clone 'my_decimal'. The member
buffer is declared as an array and memcpy results in copying the values
of the array, but the inherited member buf, which should be pointing at
the begining of the array 'buffer' starts pointing to the begining of 
buffer in original object (which is being cloned). Further updates on 
'my_decimal' updates only the inherited member 'buf' but leaves 
buffer unchanged.

Later when the new object (which now holds a inconsistent value) is cloned
again using proper cloning function 'my_decimal2decimal' the buf pointer
is fixed resulting in loss of the current value.

Using my_decimal2decimal instead of memcpy in Item_copy_decimal::copy()
fixed this problem.


mysql-test/r/subselect.result:
  Updated result file after addding test case for bug#47904.
mysql-test/t/subselect.test:
  Added test case for bug#47904.
sql/item.cc:
  Memcopy shouldn't be used to clone my_decimal. Use my_decimal2decimal
  instead.
This commit is contained in:
Anurag Shekhar 2010-04-02 01:35:36 +05:30
parent 40de15baa1
commit ab8ff15cd1
3 changed files with 173 additions and 1 deletions
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89
mysql-test/r/subselect.result
View File

@ -4628,3 +4628,92 @@ WHERE t1.a = d1.a;
ERROR 42S22: Unknown column 'd1.a' in 'where clause'
DROP TABLE t1;
End of 5.1 tests.
Set up test tables.
CREATE TABLE t1 (
t1_id INT UNSIGNED,
PRIMARY KEY(t1_id)
) Engine=MyISAM;
INSERT INTO t1 (t1_id) VALUES (1), (2), (3), (4), (5);
CREATE TABLE t2 SELECT * FROM t1;
CREATE TABLE t3 (
t3_id INT UNSIGNED AUTO_INCREMENT,
t1_id INT UNSIGNED,
amount DECIMAL(16,2),
PRIMARY KEY(t3_id),
KEY(t1_id)
) Engine=MyISAM;
INSERT INTO t3 (t1_id, t3_id, amount)
VALUES (1, 1, 100.00), (2, 2, 200.00), (4, 4, 400.00);
This is the 'inner query' running by itself.
Produces correct results.
SELECT
t1.t1_id,
IFNULL((SELECT SUM(amount) FROM t3 WHERE t3.t1_id=t1.t1_id), 0) AS total_amount
FROM
t1
LEFT JOIN t2 ON t2.t1_id=t1.t1_id
GROUP BY
t1.t1_id
;
t1_id total_amount
1 100.00
2 200.00
3 0.00
4 400.00
5 0.00
SELECT * FROM (the same inner query)
Produces correct results.
SELECT * FROM (
SELECT
t1.t1_id,
IFNULL((SELECT SUM(amount) FROM t3 WHERE t3.t1_id=t1.t1_id), 0) AS total_amount
FROM
t1
LEFT JOIN t2 ON t2.t1_id=t1.t1_id
GROUP BY
t1.t1_id
) AS t;
t1_id total_amount
1 100.00
2 200.00
3 0.00
4 400.00
5 0.00
Now make t2.t1_id part of a key.
ALTER TABLE t2 ADD PRIMARY KEY(t1_id);
Same inner query by itself.
Still correct results.
SELECT
t1.t1_id,
IFNULL((SELECT SUM(amount) FROM t3 WHERE t3.t1_id=t1.t1_id), 0) AS total_amount
FROM
t1
LEFT JOIN t2 ON t2.t1_id=t1.t1_id
GROUP BY
t1.t1_id;
t1_id total_amount
1 100.00
2 200.00
3 0
4 400.00
5 0
SELECT * FROM (the same inner query), now with indexes on the LEFT JOIN
SELECT * FROM (
SELECT
t1.t1_id,
IFNULL((SELECT SUM(amount) FROM t3 WHERE t3.t1_id=t1.t1_id), 0) AS total_amount
FROM
t1
LEFT JOIN t2 ON t2.t1_id=t1.t1_id
GROUP BY
t1.t1_id
) AS t;
t1_id total_amount
1 100.00
2 200.00
3 0.00
4 400.00
5 0.00
DROP TABLE t3;
DROP TABLE t2;
DROP TABLE t1;

83
mysql-test/t/subselect.test
View File

@ -3618,3 +3618,86 @@ DROP TABLE t1;
--echo End of 5.1 tests.
#
# Bug #47904 Incorrect results w/ table subquery, derived SQs, and LEFT JOIN on index
#
--echo Set up test tables.
CREATE TABLE t1 (
t1_id INT UNSIGNED,
PRIMARY KEY(t1_id)
) Engine=MyISAM;
INSERT INTO t1 (t1_id) VALUES (1), (2), (3), (4), (5);
CREATE TABLE t2 SELECT * FROM t1;
CREATE TABLE t3 (
t3_id INT UNSIGNED AUTO_INCREMENT,
t1_id INT UNSIGNED,
amount DECIMAL(16,2),
PRIMARY KEY(t3_id),
KEY(t1_id)
) Engine=MyISAM;
INSERT INTO t3 (t1_id, t3_id, amount)
VALUES (1, 1, 100.00), (2, 2, 200.00), (4, 4, 400.00);
--echo This is the 'inner query' running by itself.
--echo Produces correct results.
SELECT
t1.t1_id,
IFNULL((SELECT SUM(amount) FROM t3 WHERE t3.t1_id=t1.t1_id), 0) AS total_amount
FROM
t1
LEFT JOIN t2 ON t2.t1_id=t1.t1_id
GROUP BY
t1.t1_id
;
--echo SELECT * FROM (the same inner query)
--echo Produces correct results.
SELECT * FROM (
SELECT
t1.t1_id,
IFNULL((SELECT SUM(amount) FROM t3 WHERE t3.t1_id=t1.t1_id), 0) AS total_amount
FROM
t1
LEFT JOIN t2 ON t2.t1_id=t1.t1_id
GROUP BY
t1.t1_id
) AS t;
--echo Now make t2.t1_id part of a key.
ALTER TABLE t2 ADD PRIMARY KEY(t1_id);
--echo Same inner query by itself.
--echo Still correct results.
SELECT
t1.t1_id,
IFNULL((SELECT SUM(amount) FROM t3 WHERE t3.t1_id=t1.t1_id), 0) AS total_amount
FROM
t1
LEFT JOIN t2 ON t2.t1_id=t1.t1_id
GROUP BY
t1.t1_id;
--echo SELECT * FROM (the same inner query), now with indexes on the LEFT JOIN
SELECT * FROM (
SELECT
t1.t1_id,
IFNULL((SELECT SUM(amount) FROM t3 WHERE t3.t1_id=t1.t1_id), 0) AS total_amount
FROM
t1
LEFT JOIN t2 ON t2.t1_id=t1.t1_id
GROUP BY
t1.t1_id
) AS t;
DROP TABLE t3;
DROP TABLE t2;
DROP TABLE t1;

2
sql/item.cc
View File

@ -3515,7 +3515,7 @@ void Item_copy_decimal::copy()
{
my_decimal *nr= item->val_decimal(&cached_value);
if (nr && nr != &cached_value)
memcpy (&cached_value, nr, sizeof (my_decimal));
my_decimal2decimal (nr, &cached_value);
null_value= item->null_value;
}