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[wk989898]

What problem does this PR solve?

Issue Number: close #xxx

What is changed and how it works?

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Tests

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[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

[ti-chi-bot]

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[gemini-code-assist]

Summary of Changes

Hello @wk989898, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a significant optimization to how multi-row DELETE statements are generated. By transitioning from a series of OR conditions to a single IN clause, the system can now execute batch deletions more efficiently. This change also involves a simplification of the codebase by removing a function that checked for mergeability of row changes, streamlining the SQL generation process.

Highlights

• SQL Generation Optimization: The GenDeleteSQL function has been refactored to generate DELETE ... IN (...) statements for multi-row deletions, replacing the less efficient DELETE ... OR ... syntax. This change aims to improve the performance of batch delete operations.
• Code Simplification: The SameTypeTargetAndColumns function, previously used to determine if row changes could be merged, has been removed. This likely simplifies the logic now that GenDeleteSQL uses a more generalized IN clause approach.

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[wk989898]

/test pull-cdc-mysql-integration-heavy

[gemini-code-assist]

Code Review

This pull request refactors GenDeleteSQL to use a more efficient IN clause for batch deletes, which is a good performance improvement. It also removes the now-unused SameTypeTargetAndColumns function. My review focuses on a potential correctness issue introduced by the GenDeleteSQL optimization. I've suggested adding a defensive check to prevent generating invalid SQL in edge cases.

[gemini-code-assist]

The new implementation of GenDeleteSQL is more efficient, but it assumes that all RowChanges in the changes slice will produce the same set of WHERE columns from whereColumnsAndValues. This was previously guaranteed by SameTypeTargetAndColumns, which has been removed in this PR.

If different RowChanges have different WHERE columns (e.g., due to using different unique keys with nullable columns), this function will generate an incorrect SQL statement, potentially leading to data inconsistencies.

For example, if changes[0] uses (colA) and changes[1] uses (colB), the generated SQL will be DELETE ... WHERE (colA) IN ((?), (?)) with arguments for both colA and colB, which is incorrect.

I suggest adding a check to ensure this precondition holds. A DPanic would be appropriate to catch this during development and testing, consistent with other checks in this package.

                cols, args := c.whereColumnsAndValues()
		if len(cols) != len(whereColumns) {
			// The number of where columns is not as expected.
			// This may happen when the handle key is not the same for all changes.
			log.L().DPanic("unexpected where columns length in GenDeleteSQL",
				zap.Int("expected", len(whereColumns)),
				zap.Int("got", len(cols)),
				zap.Any("expected-cols", whereColumns),
				zap.Any("got-cols", cols))
		}
		allArgs = append(allArgs, args...)

[ti-chi-bot]

@wk989898: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-cdc-mysql-integration-heavy	1ce7c23	link	true	/test pull-cdc-mysql-integration-heavy

Full PR test history. Your PR dashboard.

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