Added a spatial index to the overlayng polygonbuilder #1379
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arriopolis
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pramsey
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Jan 16, 2026
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pramsey
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LGTM, nice contained change. I guess we need a port of HPRtree at some point.
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@arriopolis Nice work!
@pramsey yes indeedy. It might be even more effective in GEOS than JTS, due to advantages of less memory allocation, better locality, and better small-size index handling. |
dbaston
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Jan 17, 2026
| if (hole->getShell() == nullptr) { | ||
| OverlayEdgeRing* shell = hole->findEdgeRingContaining(shells); | ||
| // get list of overlapping shells | ||
| std::vector<OverlayEdgeRing*> shellListOverlaps; |
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Can move this outside of the for loop and call .clear() inside the for loop to reuse it.
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This PR ports this JTS PR to GEOS. It adds a spatial index to the polygonbuilder in overlayNG.
The proposed implementation differs from the JTS implementation, since the latter uses an HPR-tree (Hilbert-packed R-tree) as the spatial filter. The implementation of the HPR-tree has not yet been ported to GEOS, so I'm using an STR-tree here instead. Following the discussion at the JTS PR, the adverse consequences should be insignificant.
The performance improvements are substantial. Similar to this GEOS PR, I benchmarked the code using a difference operation between two MultiPolygons. To simulate real-world data, I used datasets taken from OSM. Specifically, I took the landmass of a region, and subtracted all its rivers and lakes. The resulting runtimes are listed in the table below.
All timings have been obtained by taking the average runtime of 5 independent runs. The improvement becomes pretty significant for large objects (~20x improvement for USA), signifying that this PR removes a considerable bottleneck in the old implementation. I also verified that the two implementations produce the same results by comparing the areas of the resulting objects.