expression: fix charset conversion warning and error behavior

[YangKeao]

What problem does this PR solve?

Issue Number: close #50295

Problem Summary:

The error cannotConvertString should have three different behaviors:

1. Explicit cast, and SQL_MODE is strict: it'll return NULL and add a warning.
2. Explicit cast, and SQL_MODE is not strict: it'll return truncated string and add a warning.
3. Implicit cast: it'll return an error.

TiDB returns error in all cases, so it's not compatible.

What changed and how does it work?

Fix the behavior of from_binary function. Now it's only fixed on TiDB, and will need some modification on TiKV as well.

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

[ti-chi-bot]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[tiprow]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[YangKeao]

/retest

[YangKeao]

/retest

[YangKeao]

/retest

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 8 lines in your changes are missing coverage. Please review.

Project coverage is 74.1593%. Comparing base (601e21c) to head (f0a66f0).
Report is 2 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #51191        +/-   ##
================================================
+ Coverage   72.4105%   74.1593%   +1.7488%     
================================================
  Files          1492       1492                
  Lines        429312     429505       +193     
================================================
+ Hits         310867     318518      +7651     
+ Misses        99145      91098      -8047     
- Partials      19300      19889       +589     

Flag	Coverage Δ
integration	47.6690% <71.8750%> (?)
unit	71.2358% <56.2500%> (-0.0632%)	⬇️

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

Components	Coverage Δ
dumpling	53.9957% <ø> (ø)
parser	∅ <ø> (∅)
br	50.0769% <ø> (+8.6467%)	⬆️

[YangKeao]

/retest

[YangKeao]

/retest

[YangKeao]

/retest

[YangKeao]

/retest

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Defined2014, zanmato1984

The full list of commands accepted by this bot can be found here.

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Needs approval from an approver in each of these files:

• OWNERS [Defined2014,zanmato1984]
• pkg/expression/OWNERS [zanmato1984]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-05-11 06:36:44.752260832 +0000 UTC m=+1289558.509396406: ☑️ agreed by zanmato1984.
• 2024-05-11 08:55:04.226530729 +0000 UTC m=+1297857.983666299: ☑️ agreed by Defined2014.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.1: #53227.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #53470.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #53471.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #53472.