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  1. MariaDB Server
  2. MDEV-8230

GROUP_MIN_MAX is not applied for ENGINE=HEAP when it could

        Details

        • Type: Task
        • Status: Open
        • Priority: Major
        • Resolution: Unresolved
        • Fix Version/s: None
        • Component/s: None
        • Labels:
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          Description

          DROP TABLE IF EXISTS t1;
CREATE TABLE t1 (id INT NOT NULL, a INT NOT NULL) ENGINE=HEAP;
INSERT INTO t1 VALUES (1, 1);
INSERT INTO t1 VALUES (1, 2);
INSERT INTO t1 VALUES (1, 3);
INSERT INTO t1 VALUES (1, 4);
INSERT INTO t1 VALUES (2, 1);
INSERT INTO t1 VALUES (2, 2);
INSERT INTO t1 VALUES (2, 3);
INSERT INTO t1 VALUES (2, 4);
INSERT INTO t1 VALUES (3, 1);
INSERT INTO t1 VALUES (3, 2);
INSERT INTO t1 VALUES (3, 3);
INSERT INTO t1 VALUES (3, 4);
INSERT INTO t1 VALUES (4, 1);
INSERT INTO t1 VALUES (4, 2);
INSERT INTO t1 VALUES (4, 3);
INSERT INTO t1 VALUES (4, 4);
ALTER TABLE t1 ADD KEY (id,a) USING BTREE;
EXPLAIN SELECT id,MIN(a) FROM t1 WHERE a=4 GROUP BY id;
EXPLAIN SELECT id,MIN(a) FROM t1 WHERE a>=4 GROUP BY id;

          Both EXPLAIN return

          +------+-------------+-------+-------+---------------+------+---------+------+------+-------------+
| id   | select_type | table | type  | possible_keys | key  | key_len | ref  | rows | Extra       |
+------+-------------+-------+-------+---------------+------+---------+------+------+-------------+
|    1 | SIMPLE      | t1    | index | NULL          | id   | 8       | NULL |   16 | Using where |
+------+-------------+-------+-------+---------------+------+---------+------+------+-------------+

          which means group-min-max is not used.

          Perhaps it could in both cases.
          Notice, USING BTREE makes the index suitable for ">=".

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                  • Assignee:
                    Unassigned
                    Reporter:
                    bar Alexander Barkov
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                    Dates

                    • Created:
                      Updated: