Hi,
first I wanted to say thanks because Im asking a lot of questions lately
and you guys always answer me in a fast and kind way. Sandro you
specially must be tired of me. sorry!! :)
now another more question.
I found the function intersects (topogeom, topogeom) quite interesting
even it is not documented, because I was expecting it to show me the
persistent topology performance.
I have a table called suelos (10000 polygons) with a normal geometry
column (geom) and a topology column (topogeom) where I populated the
geometries.
This query takes 25 secs.
select count(*) from suelos s1, suelos s2 where st_intersects
(s1.geom, s2.geom);
I was expecting this query to take 1 or less secs:
select count(*) from suelos s1, suelos s2 where intersects (s1.topogeom,
s2.topogeom);
but after taking more than 10 mins I cancelled it.
Then I noticed that the topogeom column is not using any spatial index
then I added a column:
s1=# alter table suelos add column box geometry (polygon, 23030);
s1=# update suelos set box = st_envelope (topogeom::geometry);
s1=# create index gist_suelos_topogeom using gist (box);
and the following sentence took 60 secs (still much more that I was
expecting)
select count(*) from suelos s1, suelos s2 where s1.box && s2.box and
intersects (s1.topogeom, s2.topogeom);
Then my questions?
- How can we use spatial index with topogeometry layers, making a new
box column and keep it synchronized? Why topogeom composite type does
not include a box that we can index?
- The topogeom composite type is using indexes with its fields?
- Why its taking more time that geometry types if it should have
opposite behavior?
Regards and thanks,
Jose
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