statistics: remove unused global singleton estimator

[0xPoe]

What problem does this PR solve?

Issue Number: ref #67449

Problem Summary: EstimateGlobalSingletonBySketches has no production callers.

What changed and how does it work?

Remove the unused estimator, its private helpers and dedicated tests; regenerate Bazel metadata. Keep NDV estimation unchanged.

Check List

Tests

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

  • I checked and no code files have been changed.

Validation (Ready profile; failpoints enabled and cleaned up):

make bazel_prepare
./tools/check/failpoint-go-test.sh pkg/statistics -run '^TestEstimateNDVByGEE$' -count=1
make lint
git diff --check

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

Summary by CodeRabbit

• Removed

  • Removed global singleton estimation based on sketch data.
  • The associated public estimation capability is no longer available.

• Tests

  • Removed coverage for the retired global singleton estimation behavior, including edge cases and invalid-input scenarios.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Team

Run ID: d010640e-e579-4d82-801f-12cdeb24ab82

📥 Commits

Reviewing files that changed from the base of the PR and between aec988e and d2afdda.

📒 Files selected for processing (3)

• pkg/statistics/BUILD.bazel
• pkg/statistics/estimate.go
• pkg/statistics/estimate_test.go

💤 Files with no reviewable changes (3)

• pkg/statistics/BUILD.bazel
• pkg/statistics/estimate.go
• pkg/statistics/estimate_test.go

Included review availability: Your plan provides up to 10 included reviews per hour; 9 remain after this review.

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📝 Walkthrough

Walkthrough

The change removes global singleton estimation from pkg/statistics, deletes its test suite, and removes the test file from the Bazel target.

Changes

Cohort / File(s)	Summary
Global singleton estimation removal pkg/statistics/estimate.go, pkg/statistics/estimate_test.go, pkg/statistics/BUILD.bazel	Removes the estimation API, supporting helpers, validation logic, aggregation tests, and Bazel source declaration.

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

Merge Risk: ⚪ Minimal · up to 3bf7d

This change removes an unused estimator and its associated tests and build metadata while leaving NDV estimation unchanged. No concrete current-head merge risk is identified.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the package and the main change: removal of the unused global singleton estimator.
Description check	✅ Passed	The description follows the required template, references issue #67449, explains the problem and changes, records validation steps, and includes side-effect, documentation, and release-note sections.
Docstring Coverage	✅ Passed	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	✅ 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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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.9336%. Comparing base (5acf657) to head (3bf7d8c).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #70928        +/-   ##
================================================
- Coverage   76.3212%   72.9336%   -3.3876%     
================================================
  Files          2041       2109        +68     
  Lines        556443     599132     +42689     
================================================
+ Hits         424684     436969     +12285     
- Misses       130859     160280     +29421     
- Partials        900       1883       +983     

Flag	Coverage Δ
integration	42.1823% <ø> (+2.5147%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	58.8258% <ø> (ø)
parser	∅ <ø> (∅)
br	46.5879% <ø> (-16.1200%)	⬇️

🚀 New features to boost your workflow:

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[0xPoe]

/hold

[0xPoe]

🔢 Self-check (PR reviewed by myself and ready for feedback)

• Code compiles successfully

• Unit tests added

• No AI-generated elegant nonsense in PR.

• Comments added where necessary

• PR title and description updated

• Documentation PR created (or confirmed not needed)

• PR size is reasonable

/cc @qw4990 @mjonss

[mjonss]

Nice cleanup!

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mjonss, qw4990

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Details

Needs approval from an approver in each of these files:

• pkg/statistics/OWNERS [mjonss,qw4990]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-09-09 08:28:18.327414339 +0000 UTC m=+1872733.498508510: ☑️ agreed by mjonss.
• 2026-09-09 08:30:53.169329093 +0000 UTC m=+1872888.340423203: ☑️ agreed by qw4990.

[0xPoe]

/unhold

[0xPoe]

/retest