statistics: add docs for the FLUSH STATS_DELTA statement

[qiancai]

What is changed, added or deleted? (Required)

Add documentation for the FLUSH STATS_DELTA statement introduced in v8.5.7 and v9.0.0 (pingcap/tidb#65668), which persists the pending statistics delta buffered in TiDB memory to the mysql.stats_meta system table immediately.

• Add a new page: sql-statements/sql-statement-flush-stats-delta.md (synopsis, options, examples, privileges).
• Add the statement to TOC.md and sql-statements/sql-statement-overview.md.
• Cross-link the statement from the "Automatic update" section in statistics.md.

All examples and behavior descriptions (target scopes, CLUSTER broadcast, privilege requirements, and warnings) are verified against a TiDB v8.5.7 TiUP playground with two TiDB instances.

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)?

• This PR is translated from: statistics: add docs for the FLUSH STATS_DELTA statement docs#23258
• Other reference link(s): planner: support flush stats_delta syntax for optimizer statistics tidb#65677, planner, executor, parser: implement scoped FLUSH STATS_DELTA tidb#67766, planner, executor, parser: support scoped FLUSH STATS_DELTA tidb#68159

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

• New Features
  • Added documentation for the FLUSH STATS_DELTA statement, including syntax, targets, permissions, examples, and behavior.
  • Added FLUSH STATS_DELTA to the SQL statement reference and statistics management documentation.
• Documentation
  • Updated release notes to link to the new statement documentation.
  • Documented immediate persistence of pending statistics updates in supported versions.

[github-actions]

Auto-sync completed successfully

Source PR: pingcap/docs#23258
Target PR: #21819

Chinese documentation has been updated based on English documentation changes.

[ti-chi-bot]

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[coderabbitai]

📝 Walkthrough

Walkthrough

Adds Chinese documentation for FLUSH STATS_DELTA, covering syntax, targets, cluster behavior, examples, permissions, compatibility, and references. Related SQL indexes, statistics guidance, the table of contents, and release notes are updated.

Changes

FLUSH STATS_DELTA documentation

Layer / File(s)	Summary
Statement behavior and syntax sql-statements/sql-statement-flush-stats-delta.md	Documents immediate statistics delta persistence, supported targets, CLUSTER, deduplication, partition handling, and missing-object behavior.
Usage, permissions, and compatibility sql-statements/sql-statement-flush-stats-delta.md	Adds single-table, wildcard, and cluster examples, required SELECT permissions, MySQL compatibility details, and related references.
Documentation navigation and statistics guidance sql-statements/sql-statement-overview.md, statistics.md, TOC.md, releases/release-8.5.7.md	Adds the statement to SQL and TOC indexes, explains its availability for statistics persistence, and links it from the release notes.

Estimated code review effort: 2 (Simple) | ~10 minutes

Suggested reviewers: lilin90

Poem

A rabbit hops through stats at night,
Flushing deltas into light.
Syntax blooms and links align,
Cluster carrots queue in line.
Docs now guide each data trail—
Hop, hop, flush, and details sail!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly states the main documentation addition for FLUSH STATS_DELTA.
Description check	✅ Passed	The description covers the change, affected versions, related links, and scope, with only an optional checklist section omitted.
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.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@sql-statements/sql-statement-flush-stats-delta.md`:
- Line 10: Correct the shared automatic-update links: in
sql-statements/sql-statement-flush-stats-delta.md lines 10-10, change the label
from 自动修改 to 自动更新 and target /statistics.md#自动更新; in statistics.md lines 19-19,
update the self-reference target to /statistics.md#自动更新.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: e78484c2-a88f-4f97-be6c-40836ad12543

📥 Commits

Reviewing files that changed from the base of the PR and between bae0ddc and a98cd8f.

📒 Files selected for processing (5)

• TOC.md
• releases/release-8.5.7.md
• sql-statements/sql-statement-flush-stats-delta.md
• sql-statements/sql-statement-overview.md
• statistics.md

[coderabbitai]

📐 Maintainability & Code Quality | 🟡 Minor | ⚡ Quick win

Correct the shared automatic-update anchor.

Both links target #automatic-update, while the supplied Chinese heading is ### 自动更新; the new statement page also uses the inaccurate label 自动修改.

• sql-statements/sql-statement-flush-stats-delta.md#L10-L10: change the label to 自动更新 and target /statistics.md#自动更新.
• statistics.md#L19-L19: change the self-reference target to /statistics.md#自动更新.

📍 Affects 2 files

• sql-statements/sql-statement-flush-stats-delta.md#L10-L10 (this comment)
• statistics.md#L19-L19

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@sql-statements/sql-statement-flush-stats-delta.md` at line 10, Correct the
shared automatic-update links: in
sql-statements/sql-statement-flush-stats-delta.md lines 10-10, change the label
from 自动修改 to 自动更新 and target /statistics.md#自动更新; in statistics.md lines 19-19,
update the self-reference target to /statistics.md#自动更新.