expresssion: fix div result type infer bug if a integer type has minimum display length (#56158)

[ti-chi-bot]

This is an automated cherry-pick of #56158

What problem does this PR solve?

Issue Number: close #55837

Problem Summary:
In MySQL, it support minimum display length when creating a integer type, for example, you can create table with type col1 bigint(4), it means the display length of col1 should be at least 4.
However, TiDB just treated 4 as the flen of the current type, which will cause wrong result in some cases, since 4 here does not mean the max length of col1 is 4: for example, in #55837 a column is declared as ts bigint(4), so tidb think the result type of ts/1000 is Decimal(9,4), which is obviousely wrong, and caused the wrong result.

Since the root cause of #55837 is when user declare an interger type with minimun display length, TiDB actually treated the minimum display length as the max length of the given type, a complete fix should be re-design of TiDB's support of minimum display length of integer type, which will involve a lots of work, and it's hardly to be finished within a short time. So this pr use a simple workaround to fix #55837

What changed and how does it work?

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

[windtalker]

lgtm

[codecov]

Codecov Report

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Additional details and impacted files

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-09-23 01:36:31.036118278 +0000 UTC m=+1443460.776542217: ☑️ agreed by windtalker.
• 2024-09-23 03:16:07.490176466 +0000 UTC m=+1449437.230600405: ☑️ agreed by XuHuaiyu.