Invalid JSON value for CAST to DATE/TIME/DATETIME/TIMESTAMP from column json_extract for virtual column

[wjhuang2016]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do?
   If possible, provide a recipe for reproducing the error.

create table t1 (a timestamp as (json_extract(k,'$.a')), b datetime as (json_extract(k, '$.a')) stored, k json);
insert into t1 set k='{\"a\":\"2018-09-28 12:59:51\"}';
select * from t1;

2. What did you expect to see?
   Get the data.

3. What did you see instead?

mysql> select * from t1;
+---+---------------------+------------------------------+
| a | b                   | k                            |
+---+---------------------+------------------------------+
| NULL | 2018-09-28 12:59:51 | {"a": "2018-09-28 12:59:51"} |
+---+---------------------+------------------------------+
1 row in set, 1 warning (0.00 sec)
mysql> show warnings;
+---------+------+---------------------------------------------------+
| Level   | Code | Message                                           |
+---------+------+---------------------------------------------------+
| Warning | 1105 | cannot convert datum from json to type timestamp. |
+---------+------+---------------------------------------------------+
1 row in set (0.00 sec)

4. What version of TiDB are you using (tidb-server -V or run select tidb_version(); on TiDB)?

master

[ghost]

Confirming this bug is fixed in master:

drop table if exists t1;
create table t1 (a timestamp as (json_extract(k,'$.a')), b datetime as (json_extract(k, '$.a')) stored, k json);
insert into t1 set k='{\"a\":\"2018-09-28 12:59:51\"}';
select * from t1;

..

mysql> select * from t1;
+---------------------+---------------------+------------------------------+
| a                   | b                   | k                            |
+---------------------+---------------------+------------------------------+
| 2018-09-28 12:59:51 | 2018-09-28 12:59:51 | {"a": "2018-09-28 12:59:51"} |
+---------------------+---------------------+------------------------------+
1 row in set (0.00 sec)

mysql> select tidb_version()\G
*************************** 1. row ***************************
tidb_version(): Release Version: v4.0.0-beta.2-798-gd941ff5cc
Edition: Community
Git Commit Hash: d941ff5cc8b4babf9dcfdd91b66a5c53b798c122
Git Branch: master
UTC Build Time: 2020-07-18 05:54:02
GoVersion: go1.13
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false
1 row in set (0.00 sec)

Interestingly, this is invalid in MySQL 5.7 but works in MySQL 8.0:

mysql [localhost:5731] {msandbox} (test) > insert into t1 set k='{\"a\":\"2018-09-28 12:59:51\"}';
ERROR 3156 (22018): Invalid JSON value for CAST to DATE/TIME/DATETIME/TIMESTAMP from column json_extract at row 1

mysql [localhost:8021] {msandbox} (test) > insert into t1 set k='{\"a\":\"2018-09-28 12:59:51\"}';
Query OK, 1 row affected (0.00 sec)

mysql [localhost:8021] {msandbox} (test) > select * from t1;
+---------------------+---------------------+------------------------------+
| a                   | b                   | k                            |
+---------------------+---------------------+------------------------------+
| 2018-09-28 12:59:51 | 2018-09-28 12:59:51 | {"a": "2018-09-28 12:59:51"} |
+---------------------+---------------------+------------------------------+
1 row in set (0.00 sec)

I am going to close this issue now. Thanks!