expression: set json to right type

[xiongjiwei]

Signed-off-by: xiongjiwei [email protected]

What problem does this PR solve?

Issue Number: close #xxx

Problem Summary:

What is changed and how it works?

Check List

Tests

• [ ] Unit test
• [ ] Integration test
• [ ] Manual test (add detailed scripts or steps below)
• [ ] No code

Side effects

• [ ] Performance regression: Consumes more CPU
• [ ] Performance regression: Consumes more Memory
• [ ] Breaking backward compatibility

Documentation

• [ ] Affects user behaviors
• [ ] Contains syntax changes
• [ ] Contains variable changes
• [ ] Contains experimental features
• [ ] Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• tangenta
• xhebox

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[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/58a81bcbc2bcfe00a7829c04b77f0699716e6e5d

[xhebox]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: c26ef41ad1b463934784f636a456fdf2684cdb28

[sre-bot]

TiDB MergeCI notify

✅ Well Done! New fixed [2] after this pr merged.

CI Name	Result	Duration	Compare with Parent commit
idc-jenkins-ci-tidb/integration-common-test	✅ all 17 tests passed	18 min	Fixed
idc-jenkins-ci-tidb/integration-ddl-test	✅ all 6 tests passed	6 min 44 sec	Fixed
idc-jenkins-ci/integration-cdc-test	🟢 all 36 tests passed	29 min	Existing passed
idc-jenkins-ci-tidb/common-test	🟢 all 11 tests passed	14 min	Existing passed
idc-jenkins-ci-tidb/tics-test	🟢 all 1 tests passed	7 min 23 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	5 min 35 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-1	🟢 all 26 tests passed	4 min 54 sec	Existing passed
idc-jenkins-ci-tidb/mybatis-test	🟢 all 1 tests passed	3 min 15 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	2 min 55 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed