Hi,
recently I had a query optimization issue related to spatial indexing with
a SQLView configured in GeoServer.
Long story short the PostGIS query planner was creating a sub-optimal
execution plan for queries like:
select ... from (<sql view>) as vtable where geometry &&
ST_GeomFromText(<wkt>, <crs>)
With a <wkt> representing a smal bbox, the query was incredibly slow, while
it was fast with a bigger one. The execution plan was quite different in
the two cases. Note that the internal query, without the external geometry
overlapping clause was indeed fast.
I tried a patch, replacing the where clause with:
ST_Envelope(geometry) && ST_GeomFromText(<wkt>, <crs>)
The query suddendly became fast also with small bboxes.
The new query should be equivalent to the original one, since the overlaps
operator should already compare envelopes.
That said, I was thinking to introduce a small change in the postgis filter
encoder, to recognize bbox filters and include the ST_Envelope(...)
function around the geometry property.
I am not 100% sure the change doesn't (negatively) affect other use cases,
so my idea is to introduce a System property to enable it
(org.geotools.jdbc.postgis.bboxfilter.envelop or something similar) and
leave the current behaviour by by default.
Any thoughts?
Thanks
Mauro
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Dott. Mauro Bartolomeoli
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