Multi-valued index should implicitly cast the json type

[YangKeao]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

CREATE TABLE t ( id INT PRIMARY KEY, j JSON, INDEX idx_a ((CAST(j->'$.a' AS DATE ARRAY))) );
INSERT INTO t VALUES (1, JSON_OBJECT('a', JSON_ARRAY('2024-05-13', '2020-01-01')));

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

mysql> CREATE TABLE t ( id INT PRIMARY KEY, j JSON, INDEX idx_a ((CAST(j->'$.a' AS DATE ARRAY))) );
Query OK, 0 rows affected (0.02 sec)

mysql> INSERT INTO t VALUES (1, JSON_OBJECT('a', JSON_ARRAY('2024-05-13', '2020-01-01')));
Query OK, 1 row affected (0.01 sec)

3. What did you see instead (Required)

mysql> CREATE TABLE t ( id INT PRIMARY KEY, j JSON, INDEX idx_a ((CAST(j->'$.a' AS DATE ARRAY))) );
Query OK, 0 rows affected (0.11 sec)

mysql> INSERT INTO t VALUES (1, JSON_OBJECT('a', JSON_ARRAY('2024-05-13', '2020-01-01')));
ERROR 3903 (HY000): Invalid JSON value for CAST for expression index 'idx_a'

A workaround is manually casting the type to date:

mysql> INSERT INTO t VALUES (1, JSON_OBJECT('a', JSON_ARRAY(cast('2024-05-13' as date))));
Query OK, 1 row affected (0.01 sec)

4. What is your TiDB version? (Required)

mysql> select tidb_version();
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version()                                                                                                                                                                                                                               |
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v8.0.0
Edition: Community
Git Commit Hash: 8ba1fa452b1ccdbfb85879ea94b9254aabba2916
Git Branch: HEAD
UTC Build Time: 2024-03-28 14:22:15
GoVersion: go1.21.4
Race Enabled: false
Check Table Before Drop: false
Store: tikv |
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

[xiongjiwei]

I am afraid it should not. ref https://bugs.mysql.com/bug.php?id=109333, doc

[YangKeao]

I am afraid it should not. ref https://bugs.mysql.com/bug.php?id=109333, doc

Thanks for the information. I remembered that I also submitted a similar bug report in the comment #50370 (comment), bug report.

I thought that the implicitly casting doesn't mean we'll introduce this bug (as long as the planner works well). But now, I agree to hold this PR for a while and see whether MySQL will change its behavior or not 🤔. As this issue has a workaround, it'll not be a big problem for the users.