This would be true if ST_Intersects would'nt already include a bounding box
intersection step before trying the real intersection algorithm.
The magic is already in PostGIS :)
ok, I'm very glad to know this.
Now I need just another little step to complete the question:
The bounding-box intersection used in the ST_Intersects is used even
when there isn't an index available on geometry field ?
Thx for clarification.
Andrea.
Il 23/09/2010 18:36, Vincent Picavet ha scritto:
Hi,
this mean that a query filter like this:
select ...
from
table1 as a,
table2 as b
where
( (a.geom&& b.geom)&& (ST_Intersects(a.geom,b.geom)=true ) )
if faster than a query without the&&
like this:
select ...
from
table1 as a,
table2 as b
where
( ST_Intersects(a.geom,b.geom)=true )
This would be true if ST_Intersects would'nt already include a bounding box
intersection step before trying the real intersection algorithm.
The magic is already in PostGIS :)
But you can try the difference with _st_intersects, which only does the
geometric intersection without the bbox comparison first.
Vincent
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