[GitHub] [jena] LorenzBuehmann commented on pull request #1344: jena-geosparql - Add assembler option to disable spatial index

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LorenzBuehmann commented on PR #1344:
URL: https://github.com/apache/jena/pull/1344#issuecomment-1146070778

   > Experts - what is the impact of no index on performance?
   Not an expert but using Fuseki with GeoSPARQL for a longer time now ...
   
   Containment checks can be way slower without index usage: 
   For example, currently, spatial containment queries that lead to point in polygon checks can make use of the index first (takes an envelope of the polygon, i.e. a rectangle to gather all points in this rectangle followed by a second check for proper point in polygon check necessary to filter points not in the polygon - for a large datasets and a small polygon this can be a huge performance gain. I don't have that exhaustive numbers at the moment though a minor example on a dataset about companies (`2 374 998` in total):
   
   The query gives the number of companies (`10 270`) in a small part of Germany:
   
   ``` sparql
   SELECT (count(?c) as ?cnt) {
      BIND("POLYGON((7.654288035299954 51.82366598560922,11.257803660299954 51.82366598560922,11.257803660299954 49.59800926392628,7.654288035299954 49.59800926392628,7.654288035299954 51.82366598560922))"^^geo:wktLiteral as ?box)
     ?c spatial:withinBoxGeom(?box) . # the explicit spatial index lookup
     ?c a coy:Company ;
     geo:hasGeometry/geo:asWKT ?lit .  
     FILTER(geof:sfContains(?box, ?lit))
   }
   ```
   with the index lookup triple pattern it takes 0.1s, without it takes ~10s.


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