expression: fix the wrong behavior of conv function (#53681)

[ti-chi-bot]

This is an automated cherry-pick of #53681

What problem does this PR solve?

Issue Number: close #53505

Problem Summary: expression: fix the wrong behavior of conv function

What changed and how does it work?

When evaluating Constant, should always use Constant.EvalXXX() instead of accessing Constant.Value directly, otherwise there might be wrong result if it's a parameter (?).

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

  • I checked and no code files have been changed.

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

[fixdb]

+1

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-06-06 04:37:47.894207464 +0000 UTC m=+7421.947519390: ☑️ agreed by fixdb.
• 2024-06-07 06:44:38.637872766 +0000 UTC m=+101432.691184691: ☑️ agreed by qw4990.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: fixdb, hawkingrei, qw4990

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[qw4990]

/test unit-test

[tiprow]

@qw4990: No presubmit jobs available for pingcap/tidb@release-6.5

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/test unit-test

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[qw4990]

/test unit-test

[tiprow]

@qw4990: No presubmit jobs available for pingcap/tidb@release-6.5

In response to this:

/test unit-test

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[codecov]

Codecov Report

Attention: Patch coverage is 40.00000% with 3 lines in your changes missing coverage. Please review.

Please upload report for BASE (release-6.5@21791f4). Learn more about missing BASE report.

Additional details and impacted files

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