Details
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Bug
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Status: Closed (View Workflow)
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Major
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Resolution: Fixed
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10.0(EOL), 10.1(EOL)
Description
This script:
DROP TABLE IF EXISTS t1;
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CREATE TABLE t1 (a VARCHAR(10)) ENGINE=MyISAM;
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INSERT INTO t1 VALUES ('a'),('A');
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SELECT * FROM t1 WHERE a='a' AND a <> _latin1'A' COLLATE latin1_bin;
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correctly returns one row:
+------+
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| a |
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+------+
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| a |
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+------+
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If I rewrite the query to use a derived table:
DROP TABLE IF EXISTS t1;
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CREATE TABLE t1 (a VARCHAR(10)) ENGINE=MyISAM;
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INSERT INTO t1 VALUES ('a'),('A');
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SELECT * FROM (SELECT * FROM t1) AS table1 WHERE a='a' AND a <> _latin1'A' COLLATE latin1_bin;
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it erroneously returns two rows:
+------+
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| a |
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+------+
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| a |
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| A |
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+------+
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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;
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CREATE TABLE t1 (a ENUM('5','6')) ENGINE=MyISAM;
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INSERT INTO t1 VALUES ('5'),('6');
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SELECT * FROM (SELECT * FROM t1) AS table1 WHERE a='5';
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SELECT * FROM (SELECT * FROM t1) AS table1 WHERE a=1;
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SELECT * FROM (SELECT * FROM t1) AS table1 WHERE a='5' AND a=1;
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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;
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DROP VIEW IF EXISTS v1;
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CREATE TABLE t1 (a varchar(10) character set cp1251 collate cp1251_ukrainian_ci, KEY (a)) ;
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INSERT INTO t1 VALUES ('DD'), ('ZZ'), ('ZZ'), ('KK'), ('FF'), ('HH'),('MM'),('`1');
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CREATE VIEW v1 AS SELECT * FROM t1;
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SELECT * FROM t1 WHERE a <> 0 AND a = ' 1';
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SELECT * FROM v1 WHERE a <> 0 AND a = ' 1';
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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;
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CREATE TABLE t1 (a ENUM('5','6'));
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INSERT INTO t1 VALUES ('5'),('6');
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DROP VIEW IF EXISTS v1;
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CREATE VIEW v1 AS SELECT * FROM t1;
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SELECT * FROM t1 WHERE a='5' AND a<2;
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SELECT * FROM v1 WHERE a='5' AND a<2;
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The first SELECT correctly return one row, the second SELECT erroneously returns no rows.
