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  1. MariaDB Server
  2. MDEV-8694

Wrong result for SELECT..WHERE a NOT LIKE 'a ' AND a='a'

Details

    • Bug
    • Status: Closed (View Workflow)
    • Major
    • Resolution: Fixed
    • 10.1.6, 5.5(EOL), 10.0(EOL)
    • 10.1.7
    • Optimizer
    • None

    Description

      This script:

      DROP TABLE IF EXISTS t1;
      		 
      CREATE TABLE t1 (a VARCHAR(10) COLLATE latin1_bin);
      		 
      INSERT INTO t1 VALUES ('a'),('a ');
      		 
      SELECT a, LENGTH(a) FROM t1 WHERE a NOT LIKE 'a ';

      returns one row:

      +------+-----------+
      		 
      | a    | LENGTH(a) |
      		 
      +------+-----------+
      		 
      | a    |         1 |
      		 
      +------+-----------+

      Now if I make the condition even stronger:

      SELECT a, LENGTH(a) FROM t1 WHERE a NOT LIKE 'a ' AND a='a';

      it erroneously returns 2 rows:

      +------+-----------+
      		 
      | a    | LENGTH(a) |
      		 
      +------+-----------+
      		 
      | a    |         1 |
      		 
      | a    |         2 |
      		 
      +------+-----------+

      The problem happens in equal fields propagation.

      WHERE a NOT LIKE 'a ' AND a='a'

      gets rewritten to

      WHERE 'a' NOT LIKE 'a ' AND a='a'

      then LIKE gets removed from the condition.

      Attachments

        Issue Links

          blocks

          Bug - A problem which impairs or prevents the functions of the product. MDEV-8728 Fix a number of problems in equal field and equal expression propagation

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed

          Activity

            Ascending order - Click to sort in descending order
            bar Alexander Barkov created issue -
            bar Alexander Barkov made changes -
            Field Original Value New Value
            Description This script:
            {code}
            DROP TABLE IF EXISTS t1;
            CREATE TABLE t1 (a VARCHAR(10) COLLATE latin1_bin);
            INSERT INTO t1 VALUES ('a'),('a ');
            SELECT a, LENGTH(a) FROM t1 WHERE a NOT LIKE 'a ';
            {code}
            returns one row:
            {noformat}
            +------+-----------+
            | a | LENGTH(a) |
            +------+-----------+
            | a | 1 |
            +------+-----------+
            {noformat}

            Now if I make the condition even stronger:
            {code}
            SELECT a, LENGTH(a) FROM t1 WHERE a NOT LIKE 'a ' AND a='a';
            {code}
            it erroneously returns 2 rows:
            {noformat}
            +------+-----------+
            | a | LENGTH(a) |
            +------+-----------+
            | a | 1 |
            | a | 2 |
            +------+-----------+
            {noformat}
            		 This script:
            {code}
            DROP TABLE IF EXISTS t1;
            CREATE TABLE t1 (a VARCHAR(10) COLLATE latin1_bin);
            INSERT INTO t1 VALUES ('a'),('a ');
            SELECT a, LENGTH(a) FROM t1 WHERE a NOT LIKE 'a ';
            {code}
            returns one row:
            {noformat}
            +------+-----------+
            | a | LENGTH(a) |
            +------+-----------+
            | a | 1 |
            +------+-----------+
            {noformat}

            Now if I make the condition even stronger:
            {code}
            SELECT a, LENGTH(a) FROM t1 WHERE a NOT LIKE 'a ' AND a='a';
            {code}
            it erroneously returns 2 rows:
            {noformat}
            +------+-----------+
            | a | LENGTH(a) |
            +------+-----------+
            | a | 1 |
            | a | 2 |
            +------+-----------+
            {noformat}

            The problem happens in equal fields propagation.
            {code}
            WHERE a NOT LIKE 'a ' AND a='a'
            {code}
            gets rewritten to
            {code}
            WHERE 'a' NOT LIKE 'a ' AND a='a'
            {code}
            then LIKE gets removed from the condition.
            bar Alexander Barkov made changes -
            Fix Version/s 10.1.7 [ 19604 ]
            Fix Version/s 10.1 [ 16100 ]
            Resolution Fixed [ 1 ]
            Status Open [ 1 ] Closed [ 6 ]
            bar Alexander Barkov made changes -
            serg Sergei Golubchik made changes -
            Workflow MariaDB v3 [ 71238 ] MariaDB v4 [ 149528 ]

            People

              bar Alexander Barkov
              bar Alexander Barkov
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              Dates

                Created:
                Updated:
                Resolved:

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