consumer: skip data file by global checkpointTs in storage consumer

[wk989898]

Added functionality to retrieve and update global checkpoint timestamp from metadata file.

What problem does this PR solve?

Issue Number: close #4885

What is changed and how it works?

file discovery is now fenced by the storage metadata checkpoint, instead of discovering every visible schema.json and .index file immediately.

• Before this patch, getNewFiles() scanned all visible schema/index files
  and immediately inserted them into the consumer’s in-memory seen state
  (tableDMLIdxMap / tableDefMap), then diffDMLMaps() decided what was “new”.
• That meant a later-version DDL file could be discovered first, executed in
  cmd/storage-consumer/consumer.go:596, and advance tableDDLWatermark. If an
  older-version DML index was only discovered in the next round, it hit the
  unchanged stale-DML branch at cmd/storage-consumer/consumer.go:678 and got
  dropped.
• After this patch, discovery itself is checkpoint-aware. Files whose
  TableVersion is ahead of the current global checkpoint are skipped before
  they enter the seen maps.
• That detail matters: skipped files are not marked as seen. So when the
  checkpoint later advances, those files are discovered for the first time
  and diffDMLMaps() still reports them as genuinely new.
• The stale DDL/DML logic in cmd/storage-consumer/consumer.go:641 and cmd/
  storage-consumer/consumer.go:680 is unchanged. The fix works by preventing
  future schema versions from being discovered too early, so the watermark
  no longer runs ahead of older-version DML discovery.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Questions

Will it cause performance regression or break compatibility?

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

Release note

Please refer to [Release Notes Language Style Guide](https://pingcap.github.io/tidb-dev-guide/contribute-to-tidb/release-notes-style-guide.html) to write a quality release note.

If you don't think this PR needs a release note then fill it with `None`.

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📥 Commits

Reviewing files that changed from the base of the PR and between f195970 and 5103e02.

📒 Files selected for processing (1)

• cmd/storage-consumer/consumer.go

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch wk989898-patch-4

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[gemini-code-assist]

Code Review

This pull request introduces a mechanism to filter DML and schema files based on a global checkpoint timestamp retrieved from a 'metadata' file in external storage. The consumer now tracks a globalCheckpointTs and uses it to skip files with a version higher than the current checkpoint. Review feedback identifies a critical backward compatibility issue: if the metadata file is missing, the checkpoint defaults to 0, causing all files to be skipped. It is recommended to only apply the filtering logic when a non-zero checkpoint has been successfully retrieved.

[wk989898]

/test storage

[wk989898]

/test storage

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: 3AceShowHand, wlwilliamx

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• OWNERS [3AceShowHand,wlwilliamx]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-04-22 09:58:31.547949365 +0000 UTC m=+2159916.753309412: ☑️ agreed by 3AceShowHand.
• 2026-04-22 10:03:14.93897532 +0000 UTC m=+2160200.144335367: ☑️ agreed by wlwilliamx.

[ti-chi-bot]

@wk989898: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-unit-test	5103e02	link	unknown	/test pull-unit-test

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #5939.
But this PR has conflicts, please resolve them!