Re: [Geotools-gt2-users] Beginner question about feature query

[Michael B. <mic...@gm...>]

Hello,

> Suppose I'm running the query a lot so I loaded all the geometries into
> FeatureCollection.

Sorry - do you mean load all features into memory or a subset of them ?

If you are working with a very large number of features in a database
with a spatial index I think it can be faster to query the database
than to query an unindexed in-memory collection. But this issue would
be better answered by someone who knows more about it than I do.

> And I'm doing queries like: check if this LineString intersect a polygon in
> another polygon table.
> Would it be faster than your example to loop through the collection I have
> and end the loop if I find an intersection?
>

You can do it that way but you can also create a filter to do the job
for you. When working with geometries I find it a bit easier to use
FilterFactory directly like this...

FilterFactory2 ff = CommonFactoryFinder.getFilterFactory2(null);
LineString line = ...
Filter intersectFilter = ff.intersects(ff.property("the_geom"),
ff.literal(line));

Once again you can do a bounding box filter first, using the bounds of
your LineString object, to cut down the running time.

You can read a bit more about filters here:
http://docs.codehaus.org/display/GEOTDOC/Filter+Examples

I'm not sure if I've answered the questions that you were asking. If
not, please post again.

Michael