Refactor projection settings: replace optional fields with generic SettingsChanges

[amosbird]

Replace per-projection optional index_granularity/index_granularity_bytes fields with a generic SettingsChanges map and a has_index_granularity_overrides flag. This enables projections to override any allowed MergeTreeSettings, not just granularity.

Changes:

• ProjectionDescription: replace optional<UInt64> index_granularity/index_granularity_bytes with SettingsChanges settings_changes and bool has_index_granularity_overrides. Remove loadSettings; validation now happens in getProjectionFromAST.
• MergeTreeData::getSettings: accept const SettingsChanges * instead of ProjectionDescriptionRawPtr. Skip copy when settings_changes is empty.
• IProjectionIndex: add getDefaultSettings and getMaxRows virtual methods.
• getProjectionFromAST: accept LoadingStrictnessLevel. On CREATE, enforce an ALLOWED_PROJECTION_SETTINGS whitelist covering part format, granularity, compression, serialization, and related settings. Run sanityCheck and reject index_granularity_bytes = 0.
• Add test 04068_projection_index_settings covering granularity overrides, ALTER+MATERIALIZE, DETACH/ATTACH persistence, min_bytes_for_wide_part override (Compact vs parent), min_compress_block_size override, disallowed settings rejection, and non-adaptive table rejection.

Changelog category (leave one):

• Improvement

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

Allow projections to override additional MergeTree settings (compression, part format, serialization) beyond just index_granularity, with a whitelist of allowed settings and validation.

Documentation entry for user-facing changes

• Documentation is not required (internal refactor, no new user-facing syntax)

[clickhouse-gh]

Workflow [PR], commit [89468aa]

Summary: ❌

job_name	test_name	status	info	comment
AST fuzzer (amd_debug)		failure
	Logical error: Primary key type mismatch, expected A, got B. (STID: 3436-4175)	FAIL	cidb

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AI Review

Summary

This PR refactors projection-level settings to use generic SettingsChanges, wires these overrides through MergeTree settings resolution, and adds validation plus stateless coverage for projection setting persistence and behavior. I reviewed the touched core storage/projection code paths and tests and did not find additional high-confidence correctness, safety, or performance issues beyond an existing inline bot comment already posted on this PR.

Missing context

• ⚠️ No CI test logs or performance report artifacts were provided in this review task, so runtime validation relied on code inspection and added test coverage in the diff.

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

[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.

[alexey-milovidov]

The Can't adjust last granule error in CI is a known issue. The fix is in #101641

[clickhouse-gh]

LLVM Coverage Report

Metric	Baseline	Current	Δ
Lines	84.10%	84.00%	-0.10%
Functions	90.90%	90.90%	+0.00%
Branches	76.60%	76.50%	-0.10%

Changed lines: 91.60% (109/119) | lost baseline coverage: 4 line(s) · Uncovered code

Full report · Diff report