ticdc: document ignore-update-only-columns filter

[lidezhu]

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• This PR is translated from: ticdc: document ignore-update-only-columns filter docs-cn#21883
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Summary by CodeRabbit

• New Features

  • Added the ignore-update-only-columns event-filter option for Kafka changefeeds.
  • UPDATE events are filtered when only configured columns change, except when primary or unique keys are modified.
  • Added OpenAPI support for configuring and viewing this option.

• Documentation

  • Documented case sensitivity, invalid-column warnings, and behavior for non-Kafka downstreams.

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[coderabbitai]

📝 Walkthrough

Walkthrough

The documentation adds the Kafka-only ignore-update-only-columns filter, its matching rules, and its exceptions. OpenAPI v2 create, response, and update configuration examples now include the option.

Changes

TiCDC filter documentation

Layer / File(s)	Summary
Document filter behavior ticdc/ticdc-changefeed-config.md, ticdc/ticdc-filter.md, ticdc/ticdc-open-api-v2.md	Documents the filter syntax, Kafka-only behavior, update-column matching, key-column exceptions, case sensitivity, and nonexistent-column handling.
Update OpenAPI configuration schemas ticdc/ticdc-open-api-v2.md	Adds ignore_update_only_columns to create, response, and update replication-task configuration examples.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Mergeability Score: ⚪ Minimal · up to 999e6

The PR adds documentation for the filter behavior, but one statement should clarify that updates to primary-key or unique-key columns are not filtered. This is a localized documentation correction with no runtime impact.

Suggested reviewers: qiancai

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description selects the affected versions and provides a reference, but it leaves the required change summary section empty.	Add a concise summary of what was documented and why, including the affected TiCDC filter behavior.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly identifies the TiCDC documentation change for the ignore-update-only-columns filter.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch ldz/add-ignore-update-config

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[coderabbitai]

Actionable comments posted: 1

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

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Run ID: 538b94ba-d150-4158-8ce6-c3717b20b445

📥 Commits

Reviewing files that changed from the base of the PR and between 97bbec4 and 999e668.

📒 Files selected for processing (3)

• ticdc/ticdc-changefeed-config.md
• ticdc/ticdc-filter.md
• ticdc/ticdc-open-api-v2.md

[coderabbitai]

🗄️ Data Integrity & Integration | 🟡 Minor | ⚡ Quick win

Document the primary/unique-key exception.

Line 298 states that every matching update is filtered. This conflicts with ticdc/ticdc-filter.md: TiCDC does not filter the event when a changed column is a primary key or unique key column.

As per path instructions: “For every actionable issue, provide a GitHub committable suggestion block when the fix can be safely applied to contiguous lines.”

Apply this suggestion

Suggested change

	| `ignore_update_only_columns` | `STRING ARRAY` type. Introduced in v8.5.8 and applicable only to Kafka downstreams. If all columns whose values are changed in an UPDATE event are included in this array, TiCDC filters out the event. For example, `["version", "updated_at"]`. (Optional) |
	| `ignore_update_only_columns` | `STRING ARRAY` type. Introduced in v8.5.8 and applicable only to Kafka downstreams. If all columns whose values are changed in an `UPDATE` event are included in this array, TiCDC filters out the event, except when the event changes a primary key or unique key column. For example, `["version", "updated_at"]`. (Optional) |

Source: Path instructions