ddl: fix unexpected duplicate entry error when adding unique index (#56162)

[ti-chi-bot]

This is an automated cherry-pick of #56162

What problem does this PR solve?

Issue Number: close #56161

Problem Summary: when merge-temp-index workers check duplicate index keys, they use BatchGet() to get index KV from the origin index and record them as a map. However, this map is not updated while handling temp index records, there may be a false-positive detection.

For example, we have {key_1 -> handle_1, key_2 -> handle_2}. If there is a temp index record like key_1 -> handle_3, then there is a duplicate key.

In this issue, we have two temp index records:

key_1 -> handle_1(deleted)
key_1 -> handle_2

The first record passes the check because a delete operation cannot cause a duplicate key. The second record fails the check because handle_2 != handle_1, even if handle_1 is deleted in the previous operation.

What changed and how does it work?

Maintain the map while handling, and remove the delete keys if necessary.

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

[Benjamin2037]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Benjamin2037, tangenta

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-09-24 09:14:33.386226063 +0000 UTC m=+1557343.126650002: ☑️ agreed by Benjamin2037.
• 2024-09-24 09:34:17.601512155 +0000 UTC m=+1558527.341936093: ☑️ agreed by tangenta.

[tangenta]

/retest

[codecov]

Codecov Report

Attention: Patch coverage is 88.23529% with 2 lines in your changes missing coverage. Please review.

Please upload report for BASE (release-7.5@55eefb6). Learn more about missing BASE report.

Additional details and impacted files

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Flag	Coverage Δ
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