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improve javadocs for LatLonPoint.nearest()

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This commit is contained in:
Robert Muir 2016-04-15 14:45:22 -04:00
parent 8f2a3a5271
commit 40e3e1e72e
1 changed files with 21 additions and 5 deletions
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26
lucene/sandbox/src/java/org/apache/lucene/document/LatLonPoint.java
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@ -64,6 +64,7 @@ import static org.apache.lucene.geo.GeoEncodingUtils.encodeLongitudeCeil;
* <li>{@link #newDistanceQuery newDistanceQuery()} for matching points within a specified distance.
* <li>{@link #newDistanceSort newDistanceSort()} for ordering documents by distance from a specified location.
* <li>{@link #newPolygonQuery newPolygonQuery()} for matching points within an arbitrary polygon.
* <li>{@link #nearest nearest()} for finding the k-nearest neighbors by distance.
* </ul>
* <p>
* <b>WARNING</b>: Values are indexed with some loss of precision from the
@ -304,24 +305,39 @@ public class LatLonPoint extends Field {
}
/**
* Finds the {@code topN} nearest indexed points to the provided point, according to Haversine distance.
* Finds the {@code n} nearest indexed points to the provided point, according to Haversine distance.
* <p>
* This is functionally equivalent to running {@link MatchAllDocsQuery} with a {@link #newDistanceSort},
* but is far more efficient since it takes advantage of properties the indexed BKD tree. Currently this
* only works with {@link Lucene60PointsFormat} (used by the default codec).
* <p>
* Documents are ordered by ascending distance from the location. The value returned in {@link FieldDoc} for
* the hits contains a Double instance with the distance in meters.
*
* @param searcher IndexSearcher to find nearest points from.
* @param field field name. must not be null.
* @param latitude latitude at the center: must be within standard +/-90 coordinate bounds.
* @param longitude longitude at the center: must be within standard +/-180 coordinate bounds.
* @param n the number of nearest neighbors to retrieve.
* @return TopFieldDocs containing documents ordered by distance.
* @throws IllegalArgumentException if the underlying PointValues is not a {@code Lucene60PointsReader} (this is a current limitation).
* @throws IOException if an IOException occurs while finding the points.
*/
public static TopFieldDocs nearest(IndexSearcher s, String fieldName, double latitude, double longitude, int n) throws IOException {
// TODO: what about multi-valued documents? what happens?
// TODO: parameter checking, what if i pass a negative n, bogus latitude, null field,etc?
public static TopFieldDocs nearest(IndexSearcher searcher, String field, double latitude, double longitude, int n) throws IOException {
List<BKDReader> readers = new ArrayList<>();
List<Integer> docBases = new ArrayList<>();
List<Bits> liveDocs = new ArrayList<>();
int totalHits = 0;
for(LeafReaderContext leaf : s.getIndexReader().leaves()) {
for(LeafReaderContext leaf : searcher.getIndexReader().leaves()) {
PointValues points = leaf.reader().getPointValues();
if (points != null) {
if (points instanceof Lucene60PointsReader == false) {
throw new IllegalArgumentException("can only run on Lucene60PointsReader points implementation, but got " + points);
}
totalHits += points.getDocCount(fieldName);
BKDReader reader = ((Lucene60PointsReader) points).getBKDReader(fieldName);
totalHits += points.getDocCount(field);
BKDReader reader = ((Lucene60PointsReader) points).getBKDReader(field);
if (reader != null) {
readers.add(reader);
docBases.add(leaf.docBase);