package org.apache.lucene.spatial;
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
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import com.spatial4j.core.context.SpatialContext;
import com.spatial4j.core.distance.DistanceUtils;
import com.spatial4j.core.shape.Point;
import com.spatial4j.core.shape.Shape;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.document.IntField;
import org.apache.lucene.document.StoredField;
import org.apache.lucene.index.DirectoryReader;
import org.apache.lucene.index.IndexableField;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.queries.function.ValueSource;
import org.apache.lucene.search.Filter;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.MatchAllDocsQuery;
import org.apache.lucene.search.Sort;
import org.apache.lucene.search.SortField;
import org.apache.lucene.search.TopDocs;
import org.apache.lucene.spatial.prefix.RecursivePrefixTreeStrategy;
import org.apache.lucene.spatial.prefix.tree.GeohashPrefixTree;
import org.apache.lucene.spatial.prefix.tree.SpatialPrefixTree;
import org.apache.lucene.spatial.query.SpatialArgs;
import org.apache.lucene.spatial.query.SpatialArgsParser;
import org.apache.lucene.spatial.query.SpatialOperation;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.RAMDirectory;
import org.apache.lucene.util.LuceneTestCase;
import java.io.IOException;
/**
* This class serves as example code to show how to use the Lucene spatial
* module.
*/
public class SpatialExample extends LuceneTestCase {
//Note: Test invoked via TestTestFramework.spatialExample()
public static void main(String[] args) throws Exception {
new SpatialExample().test();
}
public void test() throws Exception {
init();
indexPoints();
search();
}
/**
* The Spatial4j {@link SpatialContext} is a sort of global-ish singleton
* needed by Lucene spatial. It's a facade to the rest of Spatial4j, acting
* as a factory for {@link Shape}s and provides access to reading and writing
* them from Strings.
*/
private SpatialContext ctx;//"ctx" is the conventional variable name
/**
* The Lucene spatial {@link SpatialStrategy} encapsulates an approach to
* indexing and searching shapes, and providing distance values for them.
* It's a simple API to unify different approaches. You might use more than
* one strategy for a shape as each strategy has its strengths and weaknesses.
* <p />
* Note that these are initialized with a field name.
*/
private SpatialStrategy strategy;
private Directory directory;
protected void init() {
//Typical geospatial context
// These can also be constructed from SpatialContextFactory
this.ctx = SpatialContext.GEO;
int maxLevels = 11;//results in sub-meter precision for geohash
//TODO demo lookup by detail distance
// This can also be constructed from SpatialPrefixTreeFactory
SpatialPrefixTree grid = new GeohashPrefixTree(ctx, maxLevels);
this.strategy = new RecursivePrefixTreeStrategy(grid, "myGeoField");
this.directory = new RAMDirectory();
}
private void indexPoints() throws Exception {
IndexWriterConfig iwConfig = new IndexWriterConfig(TEST_VERSION_CURRENT,null);
IndexWriter indexWriter = new IndexWriter(directory, iwConfig);
//Spatial4j is x-y order for arguments
indexWriter.addDocument(newSampleDocument(
2, ctx.makePoint(-80.93, 33.77)));
//Spatial4j has a WKT parser which is also "x y" order
indexWriter.addDocument(newSampleDocument(
4, ctx.readShapeFromWkt("POINT(60.9289094 -50.7693246)")));
indexWriter.addDocument(newSampleDocument(
20, ctx.makePoint(0.1,0.1), ctx.makePoint(0, 0)));
indexWriter.close();
}
private Document newSampleDocument(int id, Shape... shapes) {
Document doc = new Document();
doc.add(new IntField("id", id, Field.Store.YES));
//Potentially more than one shape in this field is supported by some
// strategies; see the javadocs of the SpatialStrategy impl to see.
for (Shape shape : shapes) {
for (IndexableField f : strategy.createIndexableFields(shape)) {
doc.add(f);
}
//store it too; the format is up to you
// (assume point in this example)
Point pt = (Point) shape;
doc.add(new StoredField(strategy.getFieldName(), pt.getX()+" "+pt.getY()));
}
return doc;
}
private void search() throws Exception {
IndexReader indexReader = DirectoryReader.open(directory);
IndexSearcher indexSearcher = new IndexSearcher(indexReader);
Sort idSort = new Sort(new SortField("id", SortField.Type.INT));
//--Filter by circle (<= distance from a point)
{
//Search with circle
//note: SpatialArgs can be parsed from a string
SpatialArgs args = new SpatialArgs(SpatialOperation.Intersects,
ctx.makeCircle(-80.0, 33.0, DistanceUtils.dist2Degrees(200, DistanceUtils.EARTH_MEAN_RADIUS_KM)));
Filter filter = strategy.makeFilter(args);
TopDocs docs = indexSearcher.search(new MatchAllDocsQuery(), filter, 10, idSort);
assertDocMatchedIds(indexSearcher, docs, 2);
//Now, lets get the distance for the 1st doc via computing from stored point value:
// (this computation is usually not redundant)
Document doc1 = indexSearcher.doc(docs.scoreDocs[0].doc);
String doc1Str = doc1.getField(strategy.getFieldName()).stringValue();
//assume doc1Str is "x y" as written in newSampleDocument()
int spaceIdx = doc1Str.indexOf(' ');
double x = Double.parseDouble(doc1Str.substring(0, spaceIdx));
double y = Double.parseDouble(doc1Str.substring(spaceIdx+1));
double doc1DistDEG = ctx.calcDistance(args.getShape().getCenter(), x, y);
assertEquals(121.6d, DistanceUtils.degrees2Dist(doc1DistDEG, DistanceUtils.EARTH_MEAN_RADIUS_KM), 0.1);
//or more simply:
assertEquals(121.6d, doc1DistDEG * DistanceUtils.DEG_TO_KM, 0.1);
}
//--Match all, order by distance ascending
{
Point pt = ctx.makePoint(60, -50);
ValueSource valueSource = strategy.makeDistanceValueSource(pt, DistanceUtils.DEG_TO_KM);//the distance (in km)
Sort distSort = new Sort(valueSource.getSortField(false)).rewrite(indexSearcher);//false=asc dist
TopDocs docs = indexSearcher.search(new MatchAllDocsQuery(), 10, distSort);
assertDocMatchedIds(indexSearcher, docs, 4, 20, 2);
//To get the distance, we could compute from stored values like earlier.
// However in this example we sorted on it, and the distance will get
// computed redundantly. If the distance is only needed for the top-X
// search results then that's not a big deal. Alternatively, try wrapping
// the ValueSource with CachingDoubleValueSource then retrieve the value
// from the ValueSource now. See LUCENE-4541 for an example.
}
//demo arg parsing
{
SpatialArgs args = new SpatialArgs(SpatialOperation.Intersects,
ctx.makeCircle(-80.0, 33.0, 1));
SpatialArgs args2 = new SpatialArgsParser().parse("Intersects(BUFFER(POINT(-80 33),1))", ctx);
assertEquals(args.toString(),args2.toString());
}
indexReader.close();
}
private void assertDocMatchedIds(IndexSearcher indexSearcher, TopDocs docs, int... ids) throws IOException {
int[] gotIds = new int[docs.totalHits];
for (int i = 0; i < gotIds.length; i++) {
gotIds[i] = indexSearcher.doc(docs.scoreDocs[i].doc).getField("id").numericValue().intValue();
}
assertArrayEquals(ids,gotIds);
}
}