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  1. MariaDB Server
  2. MDEV-8695

Wrong result for SELECT..WHERE varchar_column='a' AND CRC32(varchar_column)=3904355907

    Details

    • Type: Bug
    • Status: Closed (View Workflow)
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: 5.5, 10.0, 10.1
    • Fix Version/s: 10.1.7
    • Component/s: Optimizer
    • Labels:
      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), CRC32(a) FROM t1 WHERE CRC32(a)=3904355907; 

      returns one row:

      +------+-----------+------------+
      | a    | LENGTH(a) | CRC32(a)   |
      +------+-----------+------------+
      | a    |         1 | 3904355907 |
      +------+-----------+------------+

      If I make the condition even stricter:

      SELECT a, LENGTH(a), CRC32(a) FROM t1 WHERE a='a' AND CRC32(a)=3904355907;

      it erroneously returns two rows:

      +------+-----------+------------+
      | a    | LENGTH(a) | CRC32(a)   |
      +------+-----------+------------+
      | a    |         1 | 3904355907 |
      | a    |         2 |  105998545 |
      +------+-----------+------------+

      This script demonstrates the same problem:

      SET NAMES latin1;
      DROP TABLE IF EXISTS t1;
      CREATE TABLE t1 (a VARCHAR(10) COLLATE latin1_bin);
      INSERT INTO t1 VALUES ('a'),('a ');
      SELECT a, HEX(a) FROM t1 WHERE HEX(a)='61';

      It returns one row:

      +------+--------+
      | a    | HEX(a) |
      +------+--------+
      | a    | 61     |
      +------+--------+

      Now if I make the condition even stricter:

      SELECT *,HEX(a) FROM t1 WHERE a='a' AND HEX(a)='61';

      It returns two rows:

      +------+--------+
      | a    | HEX(a) |
      +------+--------+
      | a    | 61     |
      | a    | 6120   |
      +------+--------+

      A similar problem with trailing spaces:

      DROP TABLE IF EXISTS t1;
      CREATE TABLE t1 (a VARCHAR(10) COLLATE latin1_bin);
      INSERT INTO t1 VALUES ('a ');
      SELECT * FROM t1 WHERE a='a';
      SELECT * FROM t1 WHERE LENGTH(a)=2;
      SELECT * FROM t1 WHERE a='a' AND LENGTH(a)=2;

      The first and the second query correctly return one row. The third query erroneously returns no rows.

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

                • Created:
                  Updated:
                  Resolved: