expression: fix json_key not compatible with MySQL

[hawkingrei]

What problem does this PR solve?

json_key is not compatible with MySQL

MySQL

mysql> select version();\
+-----------+
| version() |
+-----------+
| 8.0.18    |
+-----------+
1 row in set (0.01 sec)

mysql> SELECT JSON_KEYS('[]');
+-----------------+
| JSON_KEYS('[]') |
+-----------------+
| NULL            |
+-----------------+
1 row in set (0.00 sec)

TiDB

mysql> SELECT JSON_KEYS('[]');
ERROR 3069 (22032): Invalid JSON data provided to function  %s: %s

Check List

Tests

• Unit test
• Integration test

Release note

fix json_key not compatible with MySQL

[hawkingrei]

@qw4990 PTAL

[hawkingrei]

/run-all-tests

[bb7133]

LGTM

[bb7133]

Thanks for your contribution! @hawkingrei

Would you please update the release note from your PR description?

Release note

• Write release note for bug-fix

It is the note that will be presented to the end-users of TiDB, you can follow the existing release notes from TiDB releases: https://github.com/pingcap/tidb/releases, thanks.

[hawkingrei]

Thanks for your contribution! @hawkingrei

Would you please update the release note from your PR description?

Release note

• Write release note for bug-fix

It is the note that will be presented to the end-users of TiDB, you can follow the existing release notes from TiDB releases: https://github.com/pingcap/tidb/releases, thanks.

updated

[zz-jason]

LGTM

[sre-bot]

Your auto merge job has been accepted, waiting for 14548

[sre-bot]

/run-all-tests

[sre-bot]

cherry pick to release-3.0 failed

[hawkingrei]

@zz-jason cherry pick to release-3.0 failed

[zz-jason]

@hawkingrei would you like to help us to back port the bugfix on non-vectorized implementation of json_keys() to release 3.0 and 2.1?

[hawkingrei]

@hawkingrei would you like to help us to back port the bugfix on non-vectorized implementation of json_keys() to release 3.0 and 2.1?

Yes, Let me try.