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  1. MariaDB Server
  2. MDEV-8709

Row equality elements do not get propagated

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    Description

      DROP TABLE IF EXISTS t1;
      		 
      CREATE TABLE t1 (a INT, b INT);
      		 
      INSERT INTO t1 VALUES (10,10),(20,20);
      		 
      EXPLAIN EXTENDED SELECT * FROM t1 WHERE a=10 AND b=10 AND a>=10;
      		 
      SHOW WARNINGS;

      returns:

      +-------+------+---------------------------------------------------------------------------------------------------------------------------------+
      		 
      | Level | Code | Message                                                                                                                         |
      		 
      +-------+------+---------------------------------------------------------------------------------------------------------------------------------+
      		 
      | Note  | 1003 | select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where ((`test`.`t1`.`a` = 10) and (`test`.`t1`.`b` = 10)) |
      		 
      +-------+------+---------------------------------------------------------------------------------------------------------------------------------+

      Notice, the a>=10 part was removed from the condition.

      Now if I rewrite the same query using ROW comparison syntax:

      EXPLAIN EXTENDED SELECT * FROM t1 WHERE (a,b)=(10,10) AND a>=10;
      		 
      SHOW WARNINGS;

      It returns:

      +-------+------+-------------------------------------------------------------------------------------------------------------------------------------------------------------+
      		 
      | Level | Code | Message                                                                                                                                                     |
      		 
      +-------+------+-------------------------------------------------------------------------------------------------------------------------------------------------------------+
      		 
      | Note  | 1003 | select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where ((`test`.`t1`.`a` = 10) and (`test`.`t1`.`b` = 10) and (`test`.`t1`.`a` >= 10)) |
      		 
      +-------+------+-------------------------------------------------------------------------------------------------------------------------------------------------------------+

      Notice, the a>=10 part is still there.

      The problem was that the items that participate in the (a,b)=(10,10) equality did not have cmp_context set properly.
      With the changes made under the terms of MDEV-8728 this problem does not seem to exists any more in 10.1.8.

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        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

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              bar Alexander Barkov
              bar Alexander Barkov
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                Created:
                Updated:
                Resolved:

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