[VasShabu]

What is the purpose of the change

Removes the built-in DEDUPLICATE_KEEP_FIRST process table function added in FLINK-40896. It is replaced by the DEDUPLICATE and DEDUPLICATE_WINDOW functions, and is removed before it ships in a release.

Brief change log

• Removed the DEDUPLICATE_KEEP_FIRST entry from BuiltInFunctionDefinitions, DeduplicateKeepFirstTypeStrategy, and the DeduplicateKeepFirst runtime function
• Removed its semantic, restore and unit tests, including the restore-test plans and savepoints
• Removed the deduplicate-keep-first reference page and the function's row in the process table functions overview (English and content.zh)
• Removed the function from the ValidationOnlyInputTypeStrategy example in AGENTS.md

The classic ROW_NUMBER deduplication operators are unaffected.

Verifying this change

This change removes the function together with its tests and adds no new behavior. It is covered by the existing ProcessTableFunctionTest, ProcessTableFunctionSemanticTests and ProcessTableFunctionRestoreTests, which pass.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable

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Was generative AI tooling used to co-author this PR?

• Yes (please specify the tool below)

Generated-by: Claude Code (Claude Sonnet 5.5, Claude Opus 5.5)

[flinkbot]

CI report:

• f5929a1 Azure: SUCCESS

Bot commands

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• @flinkbot run azure re-run the last Azure build

[gustavodemorais]

LGTM. We can reuse or revert any part of this at any moment depending on the mailing list discussion.

[gustavodemorais]

LGTM