expression: fix wrong flen from baseFunctionClass

[joechenrh]

What problem does this PR solve?

Issue Number: close #56587

Problem Summary:

What changed and how does it work?

ro Previously, quoteFunctionClass may return type with flen = 0

https://github.com/pingcap/tidb/blob/f0b3bf0332ae33b0593f5f89ead872f71816cbd3/pkg/expression/builtin_string.go#L2899

And this type will be passed into LogicalUnionAll, which will result to a wrong type.

https://github.com/pingcap/tidb/blob/f0b3bf0332ae33b0593f5f89ead872f71816cbd3/pkg/planner/core/logical_plan_builder.go#L1586-L1591

Some other functions also have this problem, for example:

mysql> select elt(2, "123", cast('abcdefg' as char)) union all select "1234";
+----------------------------------------+
| elt(2, "123", cast('abcdefg' as char)) |
+----------------------------------------+
| abcd                                   |
| 1234                                   |
+----------------------------------------+
2 rows in set, 1 warning (0.00 sec)

Check List

Tests

• [X] 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[bot]]

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Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 74.8608%. Comparing base (0e3efb6) to head (3afd694). Report is 8 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #56607        +/-   ##
================================================
+ Coverage   72.8325%   74.8608%   +2.0283%     
================================================
  Files          1672       1717        +45     
  Lines        462833     472049      +9216     
================================================
+ Hits         337093     353380     +16287     
+ Misses       104947      96604      -8343     
- Partials      20793      22065      +1272     

Flag	Coverage Δ
integration	49.1691% <83.3333%> (?)
unit	72.4300% <100.0000%> (+0.2216%)	:arrow_up:

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Components	Coverage Δ
dumpling	52.7673% <ø> (ø)
parser	∅ <ø> (∅)
br	60.7186% <ø> (+15.6309%)	:arrow_up:

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[joechenrh]

/retest

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[yibin87]

/test check-dev

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[ti-chi-bot[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: windtalker, yibin87

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[ti-chi-bot[bot]]

[LGTM Timeline notifier]

Timeline:

• 2024-10-21 05:46:33.878196916 +0000 UTC m=+243594.574987550: :ballot_box_with_check: agreed by windtalker.
• 2024-11-19 07:51:17.919284155 +0000 UTC m=+947440.110153151: :ballot_box_with_check: agreed by yibin87.

[joechenrh]

/retest

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[joechenrh]

/retest

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[joechenrh]

/ok-to-test

[joechenrh]

/retest

[joechenrh]

/retest

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #57518.