Automatically create minmax + uniq statistics for new columns

[hanfei1991]

Changelog category (leave one):

• New Feature

Changelog entry (a user-readable short description of the changes that goes into CHANGELOG.md):

• auto_statistics_types MergeTree setting defaults to "minmax, uniq" — minmax and uniq statistics are created automatically for all suitable columns in new tables
• materialize_statistics_on_insert defaults to false — statistics are now built during merges rather than at INSERT time, reducing insert overhead. Use SET materialize_statistics_on_insert = 1 to restore the old
  behavior

Documentation entry for user-facing changes

• Documentation is written (mandatory for new features)

[clickhouse-gh]

Workflow [PR], commit [c8a1905]

Summary: ❌

job_name	test_name	status	info	comment
Stress test (arm_release)		failure
	Server died	FAIL	cidb, issue	ISSUE EXISTS
	Segmentation fault (STID: 4009-3959)	FAIL	cidb	IGNORED

---

AI Review

Summary

This PR changes defaults for statistics materialization: materialize_statistics_on_insert is now false (build stats during merges), and MergeTree auto_statistics_types now defaults to minmax, uniq. The code updates include corresponding compatibility history entries and broad test adjustments to keep existing expectations deterministic where needed. I did not find correctness, safety, compatibility, or performance blockers in the patch itself.

ClickHouse Rules

Item	Status	Notes
Deletion logging	➖
Serialization versioning	➖
Core-area scrutiny	✅
No test removal	✅
Experimental gate	➖
No magic constants	✅
Backward compatibility	✅
SettingsChangesHistory.cpp	✅
PR metadata quality	✅
Safe rollout	✅
Compilation time	✅
No large/binary files	✅

Final Verdict

• Status: ✅ Approve

[rschu1ze]

Tests in the private repository are destroyed :-/

[alexey-milovidov]

The Stress test (arm_msan) failure is fixed by #101239, which should be merged first. After it is merged, please update the branch to include the fix.

[clickhouse-gh]

LLVM Coverage Report

Metric	Baseline	Current	Δ
Lines	78.00%	84.00%	+6.00%
Functions	90.40%	90.90%	+0.50%
Branches	70.50%	76.50%	+6.00%

Changed lines: 100.00% (40/40) · Uncovered code

Full report · Diff report

[rschu1ze]

Public CI:

• Stress test (arm_release): Stress test segfault in DB::MergeTreeDataPartWriterCompact::cancel() #102553

Private CI:

• Somehow stuck in last commit but runs for previous runs were okay.