ticdc: minor adjust the description of foreign_key_checks (#21068)#21073
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Hello @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!
Summary of Changes
Hello team,
Gemini or gemini-code-assist here to provide a summary of this pull request. This PR is an automated cherry-pick of #21068, originating from a translated PR (#20422) in the Chinese documentation repository. The primary goal is to make minor adjustments to the documentation regarding how TiCDC handles foreign_key_checks and to update the examples in the Limitations section of the ticdc-data-replication-capabilities.md file.
The changes clarify that while TiCDC doesn't replicate upstream foreign_key_checks settings or validate constraints itself, it explicitly sets SET SESSION foreign_key_checks = OFF; when writing data downstream. This ensures that downstream foreign key validation is bypassed for data replicated by TiCDC, even if global checks are enabled. Additionally, the PR updates the Limitations section to remove the foreign key validation example and add a new example illustrating errors caused by schema mismatches when DDLs are filtered.
Highlights
- Documentation Clarification: The documentation for TiCDC's handling of
foreign_key_checkshas been updated to explicitly state that TiCDC usesSET SESSION foreign_key_checks = OFF;when writing data downstream, bypassing validation. - Limitations Section Update: The example in the Limitations section has been changed from foreign key validation to an example demonstrating errors due to schema mismatches (like a dropped column) when DDL replication is filtered.
Changelog
- ticdc/ticdc-data-replication-capabilities.md
- Clarified the behavior of TiCDC regarding downstream
foreign_key_checksby adding information about theSET SESSION foreign_key_checks = OFF;setting (Diff 1). - Updated the example in the Limitations section, replacing the foreign key validation example with one about schema mismatch errors when DDLs are filtered (Diff 2).
- Clarified the behavior of TiCDC regarding downstream
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Code Review
This pull request aims to adjust the description of foreign_key_checks in the TiCDC documentation. The intended changes, as seen in the original PR #21068, improve clarity and provide a relevant example for TiCDC limitations.
However, there is a critical issue: the file ticdc/ticdc-data-replication-capabilities.md contains unresolved merge conflict markers. This must be addressed before the PR can be merged.
As the PR author is ti-chi-bot (indicating an automated cherry-pick), I have focused my review on adherence to the style guide's instructions for such PRs, which primarily involve correcting English grammar, spelling, and punctuation mistakes in the changed content (Style Guide, line 10). The actual textual changes (Diff 1 and the intended content in Diff 2) appear to be grammatically correct and use appropriate markdown (Style Guide, line 34 for backticks).
The most pressing action is to resolve the merge conflict.
Summary of Findings
- Merge Conflict: The file
ticdc/ticdc-data-replication-capabilities.mdcontains unresolved merge conflict markers that prevent the PR from being merged. This needs to be resolved by the maintainers.
Merge Readiness
This pull request is not ready to be merged due to a critical unresolved merge conflict in ticdc/ticdc-data-replication-capabilities.md. The conflict markers must be removed and the intended changes correctly applied. While I cannot approve PRs, I recommend that this conflict be addressed before any further review or merge consideration. The intended documentation changes themselves appear to be beneficial.
| <<<<<<< HEAD | ||
| - TiCDC only verifies the integrity of upstream data changes. It does not validate whether the changes conform to upstream or downstream constraints. If the data violates downstream constraints, TiCDC will return an error when writing to the downstream. For example, TiCDC does **not** perform any foreign key validation. | ||
| ======= | ||
| - TiCDC only verifies the integrity of upstream data changes. It does not validate whether the changes conform to upstream or downstream constraints. If the data violates downstream constraints, TiCDC will return an error when writing to the downstream. | ||
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| For example: When a changefeed is configured to filter out all DDL events, if the upstream executes a `DROP COLUMN` operation but continues to write `INSERT` statements involving that column, TiCDC will fail to replicate these DML changes to the downstream because of table schema mismatches. | ||
| >>>>>>> 5bc177c304 (ticdc: minor adjust the description of `foreign_key_checks` (#21068)) |
There was a problem hiding this comment.
This section contains unresolved merge conflict markers (<<<<<<< HEAD, =======, >>>>>>>). These must be resolved before the PR can be merged.
Given this is an automated cherry-pick of PR #21068, the conflict should be resolved by:
- Keeping the changes introduced by PR ticdc: minor adjust the description of
foreign_key_checks#21068 (which is the content between=======and>>>>>>> ...). - Removing the content between
<<<<<<< HEADand=======. - Removing the conflict markers themselves.
The suggested code below reflects the intended content from PR #21068 for this section.
Style Guide References
| <<<<<<< HEAD | |
| - TiCDC only verifies the integrity of upstream data changes. It does not validate whether the changes conform to upstream or downstream constraints. If the data violates downstream constraints, TiCDC will return an error when writing to the downstream. For example, TiCDC does **not** perform any foreign key validation. | |
| ======= | |
| - TiCDC only verifies the integrity of upstream data changes. It does not validate whether the changes conform to upstream or downstream constraints. If the data violates downstream constraints, TiCDC will return an error when writing to the downstream. | |
| For example: When a changefeed is configured to filter out all DDL events, if the upstream executes a `DROP COLUMN` operation but continues to write `INSERT` statements involving that column, TiCDC will fail to replicate these DML changes to the downstream because of table schema mismatches. | |
| >>>>>>> 5bc177c304 (ticdc: minor adjust the description of `foreign_key_checks` (#21068)) | |
| - TiCDC only verifies the integrity of upstream data changes. It does not validate whether the changes conform to upstream or downstream constraints. If the data violates downstream constraints, TiCDC will return an error when writing to the downstream. | |
| For example: When a changefeed is configured to filter out all DDL events, if the upstream executes a `DROP COLUMN` operation but continues to write `INSERT` statements involving that column, TiCDC will fail to replicate these DML changes to the downstream because of table schema mismatches. |
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[APPROVALNOTIFIER] This PR is APPROVED This pull-request has been approved by: lilin90 The full list of commands accepted by this bot can be found here. The pull request process is described here DetailsNeeds approval from an approver in each of these files:
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3 participants
This is an automated cherry-pick of #21068
First-time contributors' checklist
What is changed, added or deleted? (Required)
Which TiDB version(s) do your changes apply to? (Required)
Tips for choosing the affected version(s):
By default, CHOOSE MASTER ONLY so your changes will be applied to the next TiDB major or minor releases. If your PR involves a product feature behavior change or a compatibility change, CHOOSE THE AFFECTED RELEASE BRANCH(ES) AND MASTER.
For details, see tips for choosing the affected versions.
What is the related PR or file link(s)?
foreign_key_checksdocs-cn#20422Do your changes match any of the following descriptions?