[windtalker]

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

Add union to the SQL operator list for tidb_executor_concurrency in system-variables.md to document its concurrency control.

Validation: ./scripts/markdownlint system-variables.md and git diff --check passed.

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

• Related code change PR links (if applicable):
• This PR is translated from:
• Other reference link(s): https://github.com/pingcap/tidb/blob/master/pkg/executor/builder.go and https://github.com/pingcap/tidb/blob/master/pkg/sessionctx/variable/session.go

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

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• Delete files
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Summary by CodeRabbit

• 文档
  • 在 tidb_executor_concurrency 管理的算子范围中加入 Union 算子。

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: Repository: pingcap/docs-cn/.coderabbit.yaml
• Review profile: ASSERTIVE
• Plan: Advanced
• Run ID: c3bd62e5-5311-4480-83e8-f4b35aabe483

📥 Commits

Reviewing files that changed from the base of the PR and between ade7687 and b32f967.

📒 Files selected for processing (1)

• system-variables.md

Included review availability: This review used your included allowance. Your plan provides up to 4 included reviews per hour; 3 remain after this review.

📝 Walkthrough

文档更新了 tidb_executor_concurrency 的算子列表，将 union 加入该变量管理的算子范围。

Changes: 并发算子范围

Layer / File(s)	Summary
更新算子列表 system-variables.md	在 tidb_executor_concurrency 的算子列表中新增 union。

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~3 minutes

Change: Other

Suggested reviewers: qiancai

Merge Risk: ⚪ Minimal · up to b32f9

The documentation accurately describes Union result-fetch concurrency; no actionable merge risk remains.

Pre-merge checks · 5

Passed checks (5 passed)

Check name	Status	Explanation
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.
Title check		标题准确概括了主要变更，明确说明将 union 加入 tidb_executor_concurrency 的算子列表。
Description check		描述包含变更内容、适用版本、参考链接、AI 参与情况和检查结果。必需章节完整，内容与变更一致。

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