expression: truncate time part for current_date columns

[tangenta]

What problem does this PR solve?

Issue Number: close #53746

Problem Summary:

When TiDB uses current_date as default value, "hour:minuate:second" is not truncated correctly. As a result, the queries with equal condition cannot match.

What changed and how does it work?

Truncate time part for current_date.

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

[tiprow]

Hi @tangenta. Thanks for your PR.

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[codecov]

Codecov Report

Attention: Patch coverage is 72.72727% with 3 lines in your changes missing coverage. Please review.

Project coverage is 55.6713%. Comparing base (3e180e2) to head (7890711).
Report is 39 commits behind head on master.

Additional details and impacted files

@@                Coverage Diff                @@
##             master     #54045         +/-   ##
=================================================
- Coverage   72.5840%   55.6713%   -16.9127%     
=================================================
  Files          1515       1637        +122     
  Lines        434637     614846     +180209     
=================================================
+ Hits         315477     342293      +26816     
- Misses        99700     249095     +149395     
- Partials      19460      23458       +3998     

Flag	Coverage Δ
integration	37.2464% <72.7272%> (?)
unit	71.5024% <72.7272%> (-0.0767%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	52.9656% <ø> (ø)
parser	∅ <ø> (∅)
br	50.1018% <ø> (+7.7665%)	⬆️

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Defined2014, XuHuaiyu

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Needs approval from an approver in each of these files:

• OWNERS [Defined2014,XuHuaiyu]
• pkg/expression/OWNERS [XuHuaiyu]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-06-17 06:40:14.288960121 +0000 UTC m=+10540.774448955: ☑️ agreed by Defined2014.
• 2024-06-21 07:52:19.753633539 +0000 UTC m=+360466.239122373: ☑️ agreed by XuHuaiyu.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #54575.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.1: #54946.