cdc(ddl): ensure strict ordering for multi-table DDLs after split

[wlwilliamx]

What problem does this PR solve?

Issue Number: close #12449

What is changed and how it works?

This PR addresses an issue where split DDLs from a multi-table RENAME statement could be executed out of order downstream because they share the same CommitTs and the order of ranging map is non-deterministic.

Check List

Tests

• Unit test
• Integration test
• Manual test

Questions

Will it cause performance regression or break compatibility?

None

Do you need to update user documentation, design documentation or monitoring documentation?

None

Release note

Fix the incorrect execution order of split DDLs generated from a multi-table DDL statement (e.g., RENAME TABLE).

[gemini-code-assist]

Summary of Changes

Hello @wlwilliamx, 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 resolves a critical issue where multi-table DDL statements, such as RENAME, could lead to out-of-order execution of their constituent DDL events downstream. This problem stemmed from these split DDLs sharing the same commit timestamp and being processed non-deterministically. The solution introduces a sequence number for these events, ensuring that the original logical order of the multi-table DDL is preserved during replication, thereby enhancing data consistency and reliability in the CDC pipeline.

Highlights

• Strict DDL Ordering: Introduced a new Seq (sequence) field to DDLEvent to ensure strict ordering for split DDLs originating from a single multi-table DDL statement (e.g., RENAME TABLE) that share the same CommitTs.
• Sequence Assignment: The Seq field is populated during the buildRenameEvents process in schema_storage.go, assigning an incremental sequence number to each individual DDL event generated from a multi-table DDL.
• DDL Manager Logic Update: The ddlManager's getNextDDL function was updated to consider both CommitTs and the new Seq field when determining the next DDL to execute, guaranteeing correct order even when commit timestamps are identical.
• Serialization Updates: MessagePack (msgp) serialization and deserialization logic for DDLEvent and RedoDDLEvent was updated to properly handle the new Seq field, ensuring it is correctly transmitted and parsed.

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[gemini-code-assist]

Code Review

This pull request effectively addresses the issue of potential out-of-order execution for DDLs split from multi-table statements. By introducing a Seq field to DDLEvent, you've provided a mechanism to enforce a strict ordering for DDLs that share the same commit timestamp. The implementation across schema_storage, ddl_manager, and the model files is clean and correct. I particularly appreciate the refactoring in cdc/model/sink_gen.go which improves code reuse and maintainability for serialization logic. I have one comment regarding the manual edits in the generated file.

[gemini-code-assist]

These changes, which refactor the serialization logic for DDLEvent within RedoDDLEvent and change method receivers to pointers, are great improvements for maintainability and performance. However, since this is a generated file (as indicated by the DO NOT EDIT header), these manual changes might be lost the next time go generate is run. If the file is regenerated without these manual changes, the Seq field will not be correctly serialized for RedoDDLEvent, which could break the ordering guarantee this PR aims to provide when using redo logs. This is a potential correctness issue. Could you explore ways to make these changes permanent, perhaps by configuring the msgp generator, or add a prominent comment to the file to prevent accidental overwrites by the generator in the future?

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: asddongmen, lidezhu

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

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Details

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• OWNERS [asddongmen,lidezhu]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-12-07 11:40:09.946992314 +0000 UTC m=+781954.760769886: ☑️ agreed by asddongmen.
• 2025-12-08 07:09:26.802272727 +0000 UTC m=+852111.616050299: ☑️ agreed by lidezhu.

[wlwilliamx]

/retest

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.1: #12456.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #12457.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #12458.
But this PR has conflicts, please resolve them!

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #12459.
But this PR has conflicts, please resolve them!

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #12460.
But this PR has conflicts, please resolve them!