Details
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Bug
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Status: Closed (View Workflow)
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Major
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Resolution: Fixed
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10.2.29, 10.1.44, 10.3.22, 10.4.12, 10.5.1
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None
Description
DROP TABLE IF EXISTS t1,t2;
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CREATE TABLE t1 (a ENUM('a') CHARACTER SET latin1 PRIMARY KEY);
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INSERT INTO t1 VALUES ('a');
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DROP TABLE IF EXISTS t2;
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CREATE TABLE t2 (a ENUM('a','A') CHARACTER SET latin1 COLLATE latin1_bin);
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INSERT INTO t2 VALUES ('a'),('A');
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SELECT t1.* FROM t1 JOIN t2 ON t1.a COLLATE latin1_swedish_ci=t2.a;
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SELECT t1.* FROM t1 LEFT JOIN t2 ON t1.a COLLATE latin1_swedish_ci=t2.a;
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This script correctly returns 2 rows for the both SELECT queries.
+---+
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| a |
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+---+
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| a |
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| a |
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+---+
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2 rows in set (0.00 sec)
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If I now add a primary key on t2 and rerun the queries again:
ALTER TABLE t2 ADD PRIMARY KEY(a); |
SELECT t1.* FROM t1 JOIN t2 ON t1.a COLLATE latin1_swedish_ci=t2.a; |
SELECT t1.* FROM t1 LEFT JOIN t2 ON t1.a COLLATE latin1_swedish_ci=t2.a; |
both queries return only one rows:
+---+
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| a |
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+---+
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| a |
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+---+
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1 row in set (0.00 sec)
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This is wrong. Two rows should always be returned.
The same problem is repeatable if I change data type for t1.a from ENUM to VARCHAR(10) or SET('a').
Attachments
Issue Links
- relates to
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- Closed
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I've reopened this bug because I found a variant of the test case for
MDEV-6978that does not work properly.Let's change the definition of table t2 for
Now let's add one row
After this let's execute the query from your test case
We get the result
MariaDB [test]> SELECT t1.* FROM t1 LEFT JOIN t2 ON t1.c1 COLLATE latin1_swedish_ci=t2.c1;+----+| c1 |+----+| a || a |+----+Now let's add more rows:
The query returns the same result set as expected.
Now let's add the primary key as in your test case
Now the query returns a wrong result set
MariaDB [test]> SELECT t1.* FROM t1 LEFT JOIN t2 ON t1.c1 COLLATE latin n1_swedish_ci=t2.c1;+----+| c1 |+----+| a |+----+Note that now the query uses a plan different from that used in your test case after addition of the primary key. This plan employs a range index scan rather then a full index scan as in your test case.
MariaDB [test]> EXPLAIN SELECT t1.* FROM t1 LEFT JOIN t2 ON t1.c1 COLLATE latin1_swedish_ci=t2.c1;+------+-------------+-------+--------+---------------+---------+---------+------+------+--------------------------+| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |+------+-------------+-------+--------+---------------+---------+---------+------+------+--------------------------+| 1 | SIMPLE | t1 | system | NULL | NULL | NULL | NULL | 1 | || 1 | SIMPLE | t2 | range | PRIMARY | PRIMARY | 1 | NULL | 1 | Using where; Using index |+------+-------------+-------+--------+---------------+---------+---------+------+------+--------------------------+I reproduced the problem in the current 10.4 and 10.1. All other versions most probably are also affected.