[windtalker]

What is changed, added, or deleted? (Required)

Document the TIFLASH_LM_FILTER optimizer hint so users can choose which TiFlash filter conditions participate in late materialization. Add syntax, query-block forms, column-matching rules, prerequisites, limitations, and usage examples that show how to verify the filter split with EXPLAIN.

The source code PR is still open and has no release milestone. An HTML TODO marks the introduction version for confirmation before merging.

Validation:

• Markdown lint passed for both changed files.
• Internal link and anchor checks passed for both changed files using the repository configuration.
• git diff --check passed.

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.

• master (the latest development version)
• v9.0 (TiDB 9.0 versions)
• v8.5 (TiDB 8.5 versions)
• v8.1 (TiDB 8.1 versions)
• v7.5 (TiDB 7.5 versions)
• v7.1 (TiDB 7.1 versions)
• v6.5 (TiDB 6.5 versions)

What is the related PR or file link(s)?

• Related code change PR links (if applicable): planner: support TiFlash LM filter hint tidb#72191
• This PR is translated from:
• Other reference link(s): planner: support TiFlash late materialization filter hint tidb#70186

AI agent involvement

• The changes in this PR were primarily made by an AI agent on behalf of the PR author.

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

Summary by CodeRabbit

• Documentation
  • Added guidance for the TIFLASH_LM_FILTER optimizer hint, including how to select filters by referenced columns and what happens to conditions that do not match.
  • Documented the hint’s syntax, prerequisites, scan limitations, and behavior when parameters are missing or invalid, with examples for single- and multi-column filters and how to inspect results with EXPLAIN.

[ti-chi-bot]

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Details

Needs approval from an approver in each of these files:

• OWNERS

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[coderabbitai]

No actionable comments were generated in the recent review.

Recent review info

Run configuration

• Source mode: Auto
• Repository: pingcap/docs
• Branch: master
• File: .coderabbit.yaml
• Commit: d6df199
• Layers: Repository YAML
• Review profile: ASSERTIVE
• Plan: Advanced
• Run ID: f506c524-2453-408e-940e-b9f6a7e8d257

Commits

Reviewing files that changed from the base of the PR and between b4169a9 and 184b3dc.

Files selected for processing: 2

• optimizer-hints.md
• tiflash/tiflash-late-materialization.md

Files with no reviewable changes: 1

• optimizer-hints.md

Included review availability: This review used your included allowance. Your plan provides up to 4 included reviews per hour; 2 remain after this review.

Walkthrough

The optimizer hints reference and TiFlash late-materialization guide now document the TIFLASH_LM_FILTER hint, its filter-selection behavior, syntax, examples, prerequisites, and limitations.

Changes: TIFLASH_LM_FILTER documentation

Layer / File(s)	Summary
Hint syntax and behavior optimizer-hints.md, tiflash/tiflash-late-materialization.md	Documents how the hint selects filters by referenced columns, affects cost-based selection, and handles prerequisites, limitations, and unmatched parameters. Includes usage examples and EXPLAIN guidance.

Priority: Normal

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

Change: Other

Suggested reviewers: qiancai

Merge Risk: Minimal · up to 184b3

The documentation-only change is mergeable pending normal documentation checks.

Pre-merge checks: 5

Check name	Status	Explanation
Description check		The description explains the documentation changes, affected TiDB version, related PRs and issue, AI involvement, validation results, and version-specific considerations. The required sections are pre…
Title check		The title clearly and concisely identifies the main change: documenting the TIFLASH_LM_FILTER optimizer hint.
Docstring Coverage		No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Description check

Explanation

The description explains the documentation changes, affected TiDB version, related PRs and issue, AI involvement, validation results, and version-specific considerations. The required sections are present and sufficiently complete.

Full details: Docstring Coverage

Explanation

No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0 files. (2 skipped: 2 unsupported.)

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