I wrote the following code to test this out and when I up the size of the
feature collection up to 500,000 (or 100 times bigger than your problem) I
get an average search time of 82 milliseconds for a random bounding box
(over 100 tries). So I wouldn't worry too much about it
Ian
public LineSearch() {
try {
TYPE = DataUtilities.createType("", "Location",
"the_geom:LineString:srid=4326");
} catch (SchemaException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
ArrayList<SimpleFeature> feats = new ArrayList<>();
for (int i = 0; i < 500000; i++) {
feats.add(GenerateRandomData.createSimpleLineFeature(TYPE));
}
features = new ListFeatureCollection(TYPE, feats);
index = new SpatialIndexFeatureCollection(TYPE);
index.addAll(features);
}
public static void main(String[] args) {
LineSearch me = new LineSearch();
long sum = 0;
int loopCount = 100;
for (int j = 0; j < loopCount; j++) {
double xMin = (Math.random() * 360.0) - 180.0;
double xMax = xMin + 10.0;
double yMin = (Math.random() * 180.0) - 90.0;
double yMax = yMin + 5.0;
ReferencedEnvelope bbox = new ReferencedEnvelope(xMin, xMax, yMin,
yMax, DefaultGeographicCRS.WGS84);
long start = System.currentTimeMillis();
List<SimpleFeature> nLines = me.search(bbox);
long end = System.currentTimeMillis();
long duration = end - start;
sum+=duration;
}
System.out.println("Average search time = "+(sum/loopCount));
}
private List<SimpleFeature> search(ReferencedEnvelope bbox) {
BBOX bbFilter =
FILTERFACTORY.bbox(FILTERFACTORY.property(TYPE.getGeometryDescriptor().getLocalName()),
bbox);
FeatureCollection<SimpleFeatureType, SimpleFeature> subCollection =
features.subCollection(bbFilter);
return DataUtilities.list(subCollection);
}
On 10 February 2016 at 11:23, Stefan Schuster <stefan.m.schus...@gmail.com>
wrote:
> Hello
>
> I have about 5000 LINESTRINGS, in a List. Now I want to create a function
> “filterWithRectangle” that returns all the LINESTRINGS that are inside a
> given rectangle:
>
>
>
> List<LineString> filterWithRectangle(List<LineString> allLineStrings,
> Coordinate leftTop, Coordinate rightBottom)
>
>
>
> It is easys to implement this function by iterating over all Coordinates
> of all LineStrings and compare with the given rectangle.
>
>
>
> But this function will be called very often with the same List of
> “allLineStrings” and with different Coordinates for the rectangle.
> Therefore I wonder if it is possible to create an index for the LineStrings
> for better performance. I read that shapefiles can do something like this,
> but as far as I understood this needs access to a hard disc. I'm lokking
> for a solution that works in memory.
>
> Any ideas?
>
> Thanks for any suggestions!
>
> Stefan
>
>
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--
Ian Turton
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