cast double as datetime is not compatible with tidb/mysql

[fzhedu]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

2. What did you expect to see? (Required)

mysql> select cast(111 as datetime);
+-----------------------+
| cast(111 as datetime) |
+-----------------------+
| 2000-01-11 00:00:00   |
+-----------------------+
1 row in set (0.00 sec)

mysql> select cast(111.1 as datetime);
+-------------------------+
| cast(111.1 as datetime) |
+-------------------------+
| 2000-01-11 00:00:00     |
+-------------------------+
1 row in set (0.00 sec)

mysql> select cast(111.1 as datetime) from tdate;
+-------------------------+
| cast(111.1 as datetime) |
+-------------------------+
| 2000-01-11 00:00:00     |
+-------------------------+
1 row in set (0.00 sec)

mysql> set @@tidb_enforce_mpp=on;
Query OK, 0 rows affected (0.00 sec)

mysql> select cast(111.1 as datetime) from tdate;
+-------------------------+
| cast(111.1 as datetime) |
+-------------------------+
| NULL                    |
+-------------------------+
1 row in set (0.01 sec)

mysql> select cast(111 as datetime) from tdate;
+-----------------------+
| cast(111 as datetime) |
+-----------------------+
| 2000-01-11 00:00:00   |
+-----------------------+
1 row in set (0.01 sec)

3. What did you see instead (Required)

4. What is your TiFlash version? (Required)

master