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  1. MariaDB Server
  2. MDEV-8747

Wrong result for SELECT..WHERE derived_table_column='a' AND derived_table_column<>_latin1'A' COLLATE latin1_bin

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      Description

      This script:

      DROP TABLE IF EXISTS t1;
      CREATE TABLE t1 (a VARCHAR(10)) ENGINE=MyISAM;
      INSERT INTO t1 VALUES ('a'),('A');
      SELECT * FROM t1 WHERE a='a' AND a <> _latin1'A' COLLATE latin1_bin;

      correctly returns one row:

      +------+
      | a    |
      +------+
      | a    |
      +------+

      If I rewrite the query to use a derived table:

      DROP TABLE IF EXISTS t1;
      CREATE TABLE t1 (a VARCHAR(10)) ENGINE=MyISAM;
      INSERT INTO t1 VALUES ('a'),('A');
      SELECT * FROM (SELECT * FROM t1) AS table1 WHERE a='a' AND a <> _latin1'A' COLLATE latin1_bin;

      it erroneously returns two rows:

      +------+
      | a    |
      +------+
      | a    |
      | A    |
      +------+

      The problems happens because Item_direct_view_ref has cmp_context correctly set to STRING_RESULT, while its referenced field has cmp_context set to IMPOSSIBLE_RESULT. This makes equal field propagation replace the field to constant in <>.

      The same bug causes ENUM column to return bad results:

      DROP TABLE IF EXISTS t1;
      CREATE TABLE t1 (a ENUM('5','6')) ENGINE=MyISAM;
      INSERT INTO t1 VALUES ('5'),('6');
      SELECT * FROM (SELECT * FROM t1) AS table1 WHERE a='5';
      SELECT * FROM (SELECT * FROM t1) AS table1 WHERE a=1;
      SELECT * FROM (SELECT * FROM t1) AS table1 WHERE a='5' AND a=1;

      The first and the second query correctly return one row, equal to '5'. The third query erroneously returns empty set.

      The same problem is also demonstrated in this script:

      DROP TABLE IF EXISTS t1;
      DROP VIEW IF EXISTS v1;
      CREATE TABLE t1 (a varchar(10) character set cp1251 collate cp1251_ukrainian_ci, KEY (a)) ;
      INSERT INTO t1 VALUES ('DD'), ('ZZ'), ('ZZ'), ('KK'), ('FF'), ('HH'),('MM'),('`1');
      CREATE VIEW v1 AS SELECT * FROM t1;
      SELECT * FROM t1 WHERE a <> 0 AND a = ' 1';
      SELECT * FROM v1 WHERE a <> 0 AND a = ' 1';

      The first SELECT returns empty set, the second SELECT returns one row.

      The same problem is repeatable in this script:

      DROP TABLE IF EXISTS t1;
      CREATE TABLE t1 (a ENUM('5','6'));
      INSERT INTO t1 VALUES ('5'),('6');
      DROP VIEW IF EXISTS v1;
      CREATE VIEW v1 AS SELECT * FROM t1;
      SELECT * FROM t1 WHERE a='5' AND a<2;
      SELECT * FROM v1 WHERE a='5' AND a<2;

      The first SELECT correctly return one row, the second SELECT erroneously returns no rows.

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              • Assignee:
                bar Alexander Barkov
                Reporter:
                bar Alexander Barkov
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                • Created:
                  Updated:
                  Resolved: