CoverageValidator rebuilds every adjacent polygon's indexes once per target

[bkeepers]

CoverageValidator::validate() loops over targets and calls the static CoveragePolygonValidator::validate(target, nearGeoms, gapWidth), which calls toCoveragePolygons(adjPolygons), constructing a fresh CoveragePolygon for every adjacent polygon of every target. CoveragePolygon lazily caches an IndexedPointInAreaLocator, but the wrapper itself never survives to the next target, so each polygon's point-in-area index is rebuilt once per adjacent target rather than once per validation run.

On a coverage with one large polygon adjacent to nearly everything, this dominates. Profiling coverage_is_valid on a real coastal coverage of 88,997 polygons / 20.7M vertices whose largest part (4.26M vertices) has an envelope intersecting 88,697 of the others (macOS sample, 11,230 samples, GEOS 3.13.1):

CoverageValidator::validate()
 └ CoveragePolygonValidator::validate()                       10,598
    └ checkTargetRings → markInvalidInteriorSegments           8,905
       └ markInvalidInteriorSection
          └ CoveragePolygon::contains(CoordinateXY)            8,905
             └ IndexedPointInAreaLocator::locate()             7,694  (68.5% of total)
                └ TemplateSTRtree<SegmentView>::build()        7,694
                   └ createParentNodes → std::__introsort      7,159

Scaling, measured with geosop coverageValidate on main (a03789b), fixtures of N real parts plus the one large polygon:

parts	wall
1,001	7.97 s
4,001	31.07 s
16,001	134.9 s

That is near-linear in part count (≈N^1.06), 8.4 ms per part at 16k. Extrapolated to the full 88,997-part coverage: a floor around 850–900 s, several times the CoverageUnion (194 s) the validation guards. The sensitivity to a single member is stark: adding the one large polygon to a 1,000-part subset moves coverage_is_valid from 0.030 s to 39.8 s.

The relevant code is unchanged between 3.13.1 and current main, and JTS shares the design (CoverageValidator.java constructs a fresh CoveragePolygonValidator per target and caches nothing across targets).

Evidence: https://github.com/openwatersio/geos/tree/coverage-validator-cache-diagnostic (commit defa895)