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  1. MariaDB Server
  2. MDEV-8723

Wrong result for SELECT..WHERE COLLATION(a)='binary' AND a='a'

Details

    Description

      In this script:

      DROP TABLE IF EXISTS t1;
      		 
      CREATE TABLE t1 (a VARBINARY(10));
      		 
      INSERT INTO t1 VALUES ('a');
      		 
      SELECT * FROM t1 WHERE COLLATION(a)='binary';
      		 
      SELECT * FROM t1 WHERE a='a';

      the two SELECT queries return one row.

      Now if I join both conditions using AND in the same query:

      SELECT * FROM t1 WHERE COLLATION(a)='binary' AND a='a';

      It returns empty set.

      A similar script:

      DROP TABLE IF EXISTS t1;
      		 
      CREATE TABLE t1 (a VARBINARY(10));
      		 
      INSERT INTO t1 VALUES ('a');
      		 
      SELECT * FROM t1 WHERE CHARSET(a)='binary';
      		 
      SELECT * FROM t1 WHERE a='a'; 
      SELECT * FROM t1 WHERE CHARSET(a)='binary' AND a='a';

      A similar script:

      DROP TABLE IF EXISTS t1;
      		 
      CREATE TABLE t1 (a VARBINARY(10));
      		 
      INSERT INTO t1 VALUES ('a');
      		 
      SELECT * FROM t1 WHERE COERCIBILITY(a)=2;
      		 
      SELECT * FROM t1 WHERE a='a'; 
      SELECT * FROM t1 WHERE COERCIBILITY(a)=2 AND a='a';

      A similar script:

      DROP TABLE IF EXISTS t1;
      		 
      CREATE TABLE t1 (a VARBINARY(10));
      		 
      INSERT INTO t1 VALUES ('a');
      		 
      SELECT * FROM t1 WHERE WEIGHT_STRING(a)='a';
      		 
      SELECT * FROM t1 WHERE a='a'; 
      SELECT * FROM t1 WHERE WEIGHT_STRING(a)='a' AND a='a';

      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
          relates to

          Bug - A problem which impairs or prevents the functions of the product. MDEV-8695 Wrong result for SELECT..WHERE varchar_column='a' AND CRC32(varchar_column)=3904355907

          • Major - Major loss of function.
          • Closed

          Activity

            bar Alexander Barkov added a comment -

            After the fix

            EXPLAIN EXTENDED SELECT * FROM t1 WHERE COLLATION(a)='binary' AND a='a';
            		 
            SHOW WARNINGS;

            returns

            +-------+------+------------------------------------------------------------------------------+
            		 
            | Level | Code | Message                                                                      |
            		 
            +-------+------+------------------------------------------------------------------------------+
            		 
            | Note  | 1003 | select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` = 'a') |
            		 
            +-------+------+------------------------------------------------------------------------------+

            MySQL-5.7.8 does not support propagation in the same query:

            +---------+------+-------------------------------------------------------------------------------------------------------------------------------------------+
            		 
            | Level   | Code | Message                                                                                                                                   |
            		 
            +---------+------+-------------------------------------------------------------------------------------------------------------------------------------------+
            		 
            | Note    | 1003 | /* select#1 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` = 'a') and (collation(`test`.`t1`.`a`) = 'binary')) |
            		 
            +---------+------+-------------------------------------------------------------------------------------------------------------------------------------------+

            bar Alexander Barkov added a comment - After the fix EXPLAIN EXTENDED SELECT * FROM t1 WHERE COLLATION(a)='binary' AND a='a'; SHOW WARNINGS; returns +-------+------+------------------------------------------------------------------------------+ | Level | Code | Message | +-------+------+------------------------------------------------------------------------------+ | Note | 1003 | select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` = 'a') | +-------+------+------------------------------------------------------------------------------+ MySQL-5.7.8 does not support propagation in the same query: +---------+------+-------------------------------------------------------------------------------------------------------------------------------------------+ | Level | Code | Message | +---------+------+-------------------------------------------------------------------------------------------------------------------------------------------+ | Note | 1003 | /* select#1 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` = 'a') and (collation(`test`.`t1`.`a`) = 'binary')) | +---------+------+-------------------------------------------------------------------------------------------------------------------------------------------+

            People

              bar Alexander Barkov
              bar Alexander Barkov
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              Dates

                Created:
                Updated:
                Resolved:

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