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  1. MariaDB Server
  2. MDEV-8723

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

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          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';

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                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

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                  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')) |
+---------+------+-------------------------------------------------------------------------------------------------------------------------------------------+
                  Show
                  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

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