MySQL Bugs: #78025: Special IS NULL logic for 0000-00-00 does not work with merge views and SQ

Bug #78025	Special IS NULL logic for 0000-00-00 does not work with merge views and SQ
Submitted:	11 Aug 2015 17:43	Modified:	11 Aug 2015 21:30
Reporter:	Elena Stepanova	Email Updates:
Status:	Verified	Impact on me:	None
Category:	MySQL Server: Optimizer	Severity:	S3 (Non-critical)
Version:	5.5, 5.6, 5.7	OS:	Any
Assigned to:		CPU Architecture:	Any

Description:
MySQL has special logic for IS NULL operator with 0000-00-00 dates: 
http://dev.mysql.com/doc/refman/5.7/en/comparison-operators.html#operator_is-null

<quote>
For DATE and DATETIME columns that are declared as NOT NULL, you can find the special date '0000-00-00' by using a statement like this:

SELECT * FROM tbl_name WHERE date_column IS NULL
</quote>

However, it does not work with MERGE views (and derived_merge in 5.7). 

Output from the test case provided in 'How to repeat' section:

MySQL [test]> CREATE TABLE t1 (d DATE NOT NULL) ENGINE=MyISAM;
Query OK, 0 rows affected (0.23 sec)

MySQL [test]> INSERT INTO t1 VALUES ('0000-00-00'), ('0000-00-00');
Query OK, 2 rows affected (0.01 sec)
Records: 2  Duplicates: 0  Warnings: 0

MySQL [test]> CREATE ALGORITHM=MERGE VIEW v_merge AS SELECT * FROM t1;
Query OK, 0 rows affected (0.10 sec)

MySQL [test]> CREATE ALGORITHM=TEMPTABLE VIEW v_temptable AS SELECT * FROM t1;
Query OK, 0 rows affected (0.11 sec)

MySQL [test]> # This works:

MySQL [test]> SELECT * FROM t1 WHERE d IS NULL;
+------------+
| d          |
+------------+
| 0000-00-00 |
| 0000-00-00 |
+------------+
2 rows in set (0.00 sec)

MySQL [test]> SELECT * FROM v_temptable WHERE d IS NULL;
+------------+
| d          |
+------------+
| 0000-00-00 |
| 0000-00-00 |
+------------+
2 rows in set (0.00 sec)

MySQL [test]> # This does not work:

MySQL [test]> SELECT * FROM v_merge WHERE d IS NULL;
Empty set (0.00 sec)

MySQL [test]> # 5.7 part:

MySQL [test]> # This does not work:

MySQL [test]> SET optimizer_switch = 'derived_merge=on';
Query OK, 0 rows affected (0.00 sec)

MySQL [test]> SELECT * FROM ( SELECT * FROM t1 ) AS sq WHERE d IS NULL;
Empty set (0.00 sec)

MySQL [test]> # This works:

MySQL [test]> SET optimizer_switch = 'derived_merge=off';
Query OK, 0 rows affected (0.00 sec)

MySQL [test]> SELECT * FROM ( SELECT * FROM t1 ) AS sq WHERE d IS NULL;
+------------+
| d          |
+------------+
| 0000-00-00 |
| 0000-00-00 |
+------------+
2 rows in set (0.00 sec)

How to repeat:
set sql_mode= '';

DROP TABLE IF EXISTS t1, v_merge, v_temptable;

CREATE TABLE t1 (d DATE NOT NULL) ENGINE=MyISAM;
INSERT INTO t1 VALUES ('0000-00-00'), ('0000-00-00');

CREATE ALGORITHM=MERGE VIEW v_merge AS SELECT * FROM t1;
CREATE ALGORITHM=TEMPTABLE VIEW v_temptable AS SELECT * FROM t1;

# This works:

SELECT * FROM t1 WHERE d IS NULL;
SELECT * FROM v_temptable WHERE d IS NULL;

# This does not work:

SELECT * FROM v_merge WHERE d IS NULL;

# 5.7 part:

# This does not work:

SET optimizer_switch = 'derived_merge=on';
SELECT * FROM ( SELECT * FROM t1 ) AS sq WHERE d IS NULL;

# This works:

SET optimizer_switch = 'derived_merge=off';
SELECT * FROM ( SELECT * FROM t1 ) AS sq WHERE d IS NULL;

Thank you for the bug report.
C:\dbs>NET START mysqld57
The MySQLD57 service is starting.
The MySQLD57 service was started successfully.

C:\dbs>57

C:\dbs>c:\dbs\5.7\bin\mysql -uroot -p --port=3570 --prompt="mysql 5.7 > "
Enter password: ******
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.7.9 Source distribution PULL 08/08/2015

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Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql 5.7 > USE test
Database changed
mysql 5.7 > set sql_mode= '';
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql 5.7 >
mysql 5.7 > DROP TABLE IF EXISTS t1, v_merge, v_temptable;
Query OK, 0 rows affected, 3 warnings (0.00 sec)

mysql 5.7 >
mysql 5.7 > CREATE TABLE t1 (d DATE NOT NULL) ENGINE=MyISAM;
Query OK, 0 rows affected (0.03 sec)

mysql 5.7 > INSERT INTO t1 VALUES ('0000-00-00'), ('0000-00-00');
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql 5.7 >
mysql 5.7 > CREATE ALGORITHM=MERGE VIEW v_merge AS SELECT * FROM t1;
Query OK, 0 rows affected (0.04 sec)

mysql 5.7 > CREATE ALGORITHM=TEMPTABLE VIEW v_temptable AS SELECT * FROM t1;
Query OK, 0 rows affected (0.03 sec)

mysql 5.7 >
mysql 5.7 > # This works:
mysql 5.7 >
mysql 5.7 > SELECT * FROM t1 WHERE d IS NULL;
+------------+
| d          |
+------------+
| 0000-00-00 |
| 0000-00-00 |
+------------+
2 rows in set (0.00 sec)

mysql 5.7 > SELECT * FROM v_temptable WHERE d IS NULL;
+------------+
| d          |
+------------+
| 0000-00-00 |
| 0000-00-00 |
+------------+
2 rows in set (0.00 sec)

mysql 5.7 >
mysql 5.7 > # This does not work:
mysql 5.7 >
mysql 5.7 > SELECT * FROM v_merge WHERE d IS NULL;
Empty set (0.00 sec)

mysql 5.7 >
mysql 5.7 > # 5.7 part:
mysql 5.7 >
mysql 5.7 > # This does not work:
mysql 5.7 >
mysql 5.7 > SET optimizer_switch = 'derived_merge=on';
Query OK, 0 rows affected (0.00 sec)

mysql 5.7 > SELECT * FROM ( SELECT * FROM t1 ) AS sq WHERE d IS NULL;
Empty set (0.00 sec)

mysql 5.7 >
mysql 5.7 > # This works:
mysql 5.7 >
mysql 5.7 > SET optimizer_switch = 'derived_merge=off';
Query OK, 0 rows affected (0.00 sec)

mysql 5.7 > SELECT * FROM ( SELECT * FROM t1 ) AS sq WHERE d IS NULL;
+------------+
| d          |
+------------+
| 0000-00-00 |
| 0000-00-00 |
+------------+
2 rows in set (0.00 sec)