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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