Datetime string literal parsing mistreat separator . as FSP delimiter

[ichn-hu]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

CREATE TABLE `t` (
  `dt` datetime DEFAULT NULL,
  `ts` timestamp NULL DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;
insert into t values ('2020.10.10 10.10.10', '2020.10.10 10.10.10');

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

On MySQL:

mysql> select * from t;
+---------------------+---------------------+
| dt                  | ts                  |
+---------------------+---------------------+
| 2020-10-10 10:10:10 | 2020-10-10 10:10:10 |
+---------------------+---------------------+

3. What did you see instead (Required)

On TiDB:

mysql> select * from t;
+---------------------+---------------------+
| dt                  | ts                  |
+---------------------+---------------------+
| 2020-10-10 10:10:00 | 2020-10-10 10:10:00 |
+---------------------+---------------------+
1 rows in set (0.00 sec)

4. What is your TiDB version? (Required)

Could reproduce on master, 4.0 & 3.0

mysql> select tidb_version();
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version()                                                                                                                                                                                                                                                                                                                    |
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v4.0.0-beta.2-1393-g106b04dda-dirty
Edition: Community
Git Commit Hash: 106b04ddab7b5aabc42a58f5136565a8c7efb7a5
Git Branch: master
UTC Build Time: 2020-10-19 07:22:01
GoVersion: go1.15.2
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false |
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

[ichn-hu]

/label sig/execution

[ti-srebot]

These labels are not found sig-execution.

[ichn-hu]

/label sig/execution

[ichn-hu]

I found this bug while working on #20348 , could fix it together.

[ichn-hu]

for more information, quoted from https://dev.mysql.com/doc/refman/5.7/en/date-and-time-literals.html

A trailing fractional seconds part is recognized in the 'D hh:mm:ss.fraction', 'hh:mm:ss.fraction', 'hhmmss.fraction', and hhmmss.fraction time formats, where fraction is the fractional part in up to microseconds (6 digits) precision. The fractional part should always be separated from the rest of the time by a decimal point; no other fractional seconds delimiter is recognized.

Therefore, this seemingly ambiguous case is acutally specified that MySQL won't accept hh:mm.fraction.

[ichn-hu]

/assign @ichn-hu

[seiya-annie]

/info

[ti-srebot]

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