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  1. MariaDB Server
  2. MDEV-8231

GROUP_MIN_MAX is not applied for LIKE

        Details

        • Type: Bug
        • Status: Open
        • Priority: Minor
        • Resolution: Unresolved
        • Affects Version/s: 10.1, 10.0, 5.5
        • Fix Version/s: 10.1
        • Component/s: None
        • Labels:
          None

          Description

          This script:

          DROP TABLE IF EXISTS t1;
CREATE TABLE t1 (id INT NOT NULL, a VARCHAR(20), KEY(id,a)) ENGINE=MyISAM;
INSERT INTO t1 VALUES (1,'01');
INSERT INTO t1 VALUES (1,'02');
INSERT INTO t1 VALUES (1,'03');
INSERT INTO t1 VALUES (1,'04');
INSERT INTO t1 VALUES (2,'01'); 
INSERT INTO t1 VALUES (2,'02'); 
INSERT INTO t1 VALUES (2,'03'); 
INSERT INTO t1 VALUES (2,'04');
INSERT INTO t1 VALUES (3,'01'); 
INSERT INTO t1 VALUES (3,'02'); 
INSERT INTO t1 VALUES (3,'03'); 
INSERT INTO t1 VALUES (3,'04');
INSERT INTO t1 VALUES (4,'01'); 
INSERT INTO t1 VALUES (4,'02'); 
INSERT INTO t1 VALUES (4,'03'); 
INSERT INTO t1 VALUES (4,'04');
EXPLAIN SELECT id,MIN(a),MAX(a) FROM t1 WHERE a BETWEEN '04' AND '05' GROUP BY id;

          returns

          +------+-------------+-------+-------+---------------+------+---------+------+------+---------------------------------------+
| id   | select_type | table | type  | possible_keys | key  | key_len | ref  | rows | Extra                                 |
+------+-------------+-------+-------+---------------+------+---------+------+------+---------------------------------------+
|    1 | SIMPLE      | t1    | range | NULL          | id   | 27      | NULL |    9 | Using where; Using index for group-by |
+------+-------------+-------+-------+---------------+------+---------+------+------+---------------------------------------+

          If I used LIKE instead of BETWEEN with the same table:

          EXPLAIN SELECT id,MIN(a),MAX(a) FROM t1 WHERE a LIKE '04%' GROUP BY id;

          group-min-max is not applied:

          +------+-------------+-------+-------+---------------+------+---------+------+------+--------------------------+
| id   | select_type | table | type  | possible_keys | key  | key_len | ref  | rows | Extra                    |
+------+-------------+-------+-------+---------------+------+---------+------+------+--------------------------+
|    1 | SIMPLE      | t1    | index | NULL          | id   | 27      | NULL |   16 | Using where; Using index |
+------+-------------+-------+-------+---------------+------+---------+------+------+--------------------------+

          Group-min-max could safely be applied.

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                  • Assignee:
                    bar Alexander Barkov
                    Reporter:
                    bar Alexander Barkov
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                    Dates

                    • Created:
                      Updated: