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  1. MariaDB Server
  2. MDEV-7232

Condition propagation does not work for temporal types

        Details

        • Type: Bug
        • Status: Open
        • Priority: Minor
        • Resolution: Unresolved
        • Affects Version/s: 5.5.40, 10.0.14, 10.1.1
        • Fix Version/s: 10.1
        • Component/s: Optimizer
        • Labels:
          None

          Description

          Condition propagation works for string and numeric data types:

          DROP TABLE IF EXISTS t1;
CREATE TABLE t1 (c1 VARCHAR(10));
INSERT INTO t1 VALUES ('2001-01-01'),('2001-01-02');
EXPLAIN EXTENDED SELECT * FROM t1 WHERE CONCAT(c1)='2001-01-01' AND CONCAT(c1)>'2002-01-01';

          The above script correctly detects impossible condition:

          +------+-------------+-------+------+---------------+------+---------+------+------+----------+------------------+
| id   | select_type | table | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra            |
+------+-------------+-------+------+---------------+------+---------+------+------+----------+------------------+
|    1 | SIMPLE      | NULL  | NULL | NULL          | NULL | NULL    | NULL | NULL |     NULL | Impossible WHERE |
+------+-------------+-------+------+---------------+------+---------+------+------+----------+------------------+

          But in case of temporal data types, it does not work:

          DROP TABLE IF EXISTS t1;
CREATE TABLE t1 (c1 DATE);
INSERT INTO t1 VALUES ('2001-01-01'),('2001-01-02');
EXPLAIN EXTENDED SELECT * FROM t1 WHERE TIMESTAMP(c1)=TIMESTAMP'2001-01-01 00:00:00' AND TIMESTAMP(c1)>TIMESTAMP'2002-01-01 00:00:00';
SHOW WARNINGS;

          It does not detect that the condition is not possible:

          +------+-------------+-------+------+---------------+------+---------+------+------+----------+-------------+
| id   | select_type | table | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra       |
+------+-------------+-------+------+---------------+------+---------+------+------+----------+-------------+
|    1 | SIMPLE      | t1    | ALL  | NULL          | NULL | NULL    | NULL |    2 |   100.00 | Using where |
+------+-------------+-------+------+---------------+------+---------+------+------+----------+-------------+
+-------+------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Level | Code | Message                                                                                                                                                                                                  |
+-------+------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Note  | 1003 | select `test`.`t1`.`c1` AS `c1` from `test`.`t1` where ((cast(`test`.`t1`.`c1` as datetime) = TIMESTAMP'2001-01-01 00:00:00') and (cast(`test`.`t1`.`c1` as datetime) > TIMESTAMP'2002-01-01 00:00:00')) |
+-------+------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

          It's going to scan the entire table.

          The problem happens because clone_item() returns NULL for temporal literals. It should be rewritten to do true cloning.

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

                    • Created:
                      Updated: