[MDEV-8706] Wrong result for SELECT..WHERE time_column=TIMESTAMP'2015-08-30 00:00:00' AND time_column='00:00:00' Created: 2015-08-30  Updated: 2015-09-12  Resolved: 2015-09-09

Status: Closed
Project: MariaDB Server
Component/s: Optimizer
Affects Version/s: 10.0, 10.1
Fix Version/s: 10.1.7

Type: Bug Priority: Major
Reporter: Alexander Barkov Assignee: Alexander Barkov
Resolution: Fixed Votes: 0
Labels: propagation, upstream-not-supported

Issue Links:
Blocks
blocks MDEV-8728 Fix a number of problems in equal fie... Closed

 Description   

In this script:

SET timestamp=UNIX_TIMESTAMP('2015-08-30 10:20:30');
 
DROP TABLE IF EXISTS t1;
 
CREATE TABLE t1 (a TIME);
 
INSERT INTO t1 VALUES ('00:00:00');
 
SELECT * FROM t1 WHERE a=TIMESTAMP'2015-08-30 00:00:00';
 
SELECT * FROM t1 WHERE a='00:00:00';
 
SELECT * FROM t1 WHERE a=TIMESTAMP'2015-08-30 00:00:00' AND a='00:00:00';
 
SELECT * FROM t1 WHERE a>=TIMESTAMP'2015-08-30 00:00:00' AND a='00:00:00';

the first and the second SELECT queries correctly return one row.
The third and the fourth SELECT query erroneously return empty set.

If I rewrite the third query to use TIME literal:

SELECT * FROM t1 WHERE a=TIMESTAMP'2015-08-30 00:00:00' AND a=TIME'00:00:00';

it correctly returns one row.

Another example:

SET timestamp=UNIX_TIMESTAMP('2015-08-30 10:20:30');
 
DROP TABLE IF EXISTS t1;
 
CREATE TABLE t1 (a DATE);
 
INSERT INTO t1 VALUES ('2015-08-30'),('2015-08-31');
 
SELECT * FROM t1 WHERE a=TIME'00:00:00';
 
SELECT * FROM t1 WHERE LENGTH(a)=10;
 
SELECT * FROM t1 WHERE LENGTH(a)=10 AND a=TIME'00:00:00';

correctly returns one row in the first SELECT and both rows in the second SELECT, but erroneously returns empty set in the third SELECT.

The reason is that Item_equal remembers a wrong equal constant. In case if time_column=<const> equality it should remember a constant of TIME type.

 Comments   
Comment by Alexander Barkov [ 2015-09-12 ]

After the fix this script in MariaDB

SET timestamp=UNIX_TIMESTAMP('2015-08-30 10:20:30');
 
DROP TABLE IF EXISTS t1;
 
CREATE TABLE t1 (a TIME);
 
INSERT INTO t1 VALUES ('00:00:00');
 
EXPLAIN EXTENDED SELECT * FROM t1 WHERE a>=TIMESTAMP'2015-08-30 00:00:00' AND a='00:00:00';
 
SHOW WARNINGS;

returns

+-------+------+-----------------------------------------------------------------------------------------+
 
| Level | Code | Message                                                                                 |
 
+-------+------+-----------------------------------------------------------------------------------------+
 
| Note  | 1003 | select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` = TIME'00:00:00') |
 
+-------+------+-----------------------------------------------------------------------------------------+

The same query in MySQL-5.7.8 returns:

+---------+------+------------------------------------------------------------------------------------------------------------------------------------------+
 
| Level   | Code | Message                                                                                                                                  |
 
+---------+------+------------------------------------------------------------------------------------------------------------------------------------------+
 
| Warning | 1681 | 'EXTENDED' is deprecated and will be removed in a future release.                                                                        |
 
| Note    | 1003 | /* select#1 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` >= '00:00:00') and (`test`.`t1`.`a` = '00:00:00')) |
 
+---------+------+------------------------------------------------------------------------------------------------------------------------------------------+

I.e. MySQL does not support propagation in this example

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