cdc(ddl): ensure strict ordering for multi-table DDLs after split (#12450) #12459
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Summary of ChangesHello @ti-chi-bot, 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 addresses a critical bug in the Change Data Capture (CDC) process where multi-table DDL operations, such as Highlights
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Code Review
This pull request enhances DDL event handling by introducing a Seq field to DDLEvent for strict ordering of multi-table DDLs, particularly for ActionRenameTables and ActionCreateTables. The schemaStorage now builds multiple DDLEvents for these operations, assigning a sequence number to ensure correct processing when events share the same commit timestamp. The ddlManager's logic for selecting the next DDL event was updated to prioritize events based on this new Seq field after CommitTs, a change explicitly praised by the reviewer as a critical fix. An integration test was added to validate the ordering of rename table DDLs. A review comment, however, pointed out a potential side effect in BuildDDLEvents where job.Query is directly modified within a loop, suggesting the use of a local copy of the job object to prevent unintended mutations.
| continue | ||
| } | ||
| if res == nil || res.CommitTs > ddls[0].CommitTs { | ||
| if res == nil || res.CommitTs > ddls[0].CommitTs || (res.CommitTs == ddls[0].CommitTs && res.Seq > ddls[0].Seq) { |
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The condition (res.CommitTs == ddls[0].CommitTs && res.Seq > ddls[0].Seq) is correctly added to ensure strict ordering of DDL events when they share the same CommitTs. This is a critical fix for multi-table DDLs to prevent out-of-order execution downstream.
| multiTableInfos := job.BinlogInfo.MultipleTableInfos | ||
| for index, tableInfo := range multiTableInfos { | ||
| newTableInfo := model.WrapTableInfo(job.SchemaID, job.SchemaName, job.BinlogInfo.FinishedTS, tableInfo) | ||
| job.Query = querys[index] |
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Modifying job.Query directly within this loop can lead to unexpected side effects if the original job object is expected to remain immutable or if job.Query is used elsewhere after this function call. It's generally safer to create a local copy of the job object for each iteration and modify the copy's Query field before passing it to event.FromJob.
For example:
// Create a copy of the job for each iteration
clonedJob := *job
clonedJob.Query = querys[index]
event.FromJob(&clonedJob, nil, newTableInfo)clonedJob := *job
clonedJob.Query = querys[index]
event := new(model.DDLEvent)
event.FromJob(&clonedJob, nil, newTableInfo)
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This is an automated cherry-pick of #12450
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
RENAMEstatement could be executed out of order downstream because they share the sameCommitTsand the order of ranging map is non-deterministic.Check List
Tests
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