Improve performance of H3 geo functions (combined sincos in coordinate transforms)

[alexey-milovidov]

Updates the contrib/h3 submodule to ClickHouse/h3#11, which speeds up the H3 geo coordinate transforms by computing paired sin/cos together (one sincos call) and removing redundant trig evaluations in the hot lat/lng <-> cell routines (_geoToVec3d, _geoAzimuthRads, _geoAzDistanceRads, _geoToHex2d).

Why

PR #100272 explored replacing the H3 C library with the Rust h3o crate for performance. Investigation showed that in a fair -O3 build the C library is already competitive with h3o (the large gaps in that PR came from an un-inlined C build), and the genuinely portable win is the combined-sincos / redundant-trig cleanup — which needs no Rust, no FFI wrappers, no panics across the boundary, and no backward-incompatible metric changes.

Correctness

Bit-for-bit identical output — the change only fuses paired calls (which return the same values) and removes duplicate evaluations. All 311 upstream h3 unit tests pass unchanged, so no ClickHouse .reference files change.

Performance (10M rows, clang -O3)

function	speedup
h3ToGeoBoundary	~14%
h3ToGeo	~9–11%
h3CellAreaM2 / h3CellAreaRads2	~8%
geoToH3	~3–4%

h3ToParent / h3IsValid are already optimal (loopless bit-twiddling) and unchanged.

Note: the submodule currently points at the sincos-optimization branch commit; it will be re-pointed to the merge commit once ClickHouse/h3#11 is merged into ClickHouse/v4.

Changelog category (leave one):

• Performance Improvement

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

Improve the performance of H3 geo functions (h3ToGeoBoundary, h3ToGeo, h3CellAreaM2/h3CellAreaRads2, geoToH3) by computing paired sine/cosine together and eliminating redundant trigonometric calls in the coordinate transforms. Results are unchanged (bit-for-bit identical).

Version info

• Merged into: 26.7.1.535 (included in 26.7 and later)

[clickhouse-gh]

Workflow [PR], commit [f5ff4b2]

Summary: ✅

• Performance Comparison: Performance dashboard

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AI Review

Summary

This PR updates contrib/h3 to one upstream commit that replaces repeated sin/cos evaluations in the hot coordinate-transform helpers with a shared _sincos helper. I found no correctness issue in the current diff or ClickHouse integration, and a local old-vs-new comparison of latLngToCell, cellToLatLng, cellToBoundary, cellAreaM2, and cellAreaRads2 over 21,936 inputs and 18,300 unique cells matched bit-for-bit.

Final Verdict

Status: ✅ Approve

[alexey-milovidov]

Sounds good.