org.apache.lucene.spatial.SpatialStrategy Maven / Gradle / Ivy
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* 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,
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* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.lucene.spatial;
import org.apache.lucene.document.Field;
import org.apache.lucene.search.DoubleValuesSource;
import org.apache.lucene.search.Query;
import org.apache.lucene.spatial.query.SpatialArgs;
import org.apache.lucene.spatial.util.ReciprocalDoubleValuesSource;
import org.locationtech.spatial4j.context.SpatialContext;
import org.locationtech.spatial4j.shape.Point;
import org.locationtech.spatial4j.shape.Rectangle;
import org.locationtech.spatial4j.shape.Shape;
/**
* The SpatialStrategy encapsulates an approach to indexing and searching based on shapes.
*
* Different implementations will support different features. A strategy should document these
* common elements:
*
*
* - Can it index more than one shape per field?
*
- What types of shapes can be indexed?
*
- What types of query shapes can be used?
*
- What types of query operations are supported? This might vary per shape.
*
- Does it use some type of cache? When?
*
*
* If a strategy only supports certain shapes at index or query time, then in general it will throw
* an exception if given an incompatible one. It will not be coerced into compatibility.
*
* Note that a SpatialStrategy is not involved with the Lucene stored field values of shapes,
* which is immaterial to indexing and search.
*
*
Thread-safe.
*
*
This API is marked as experimental, however it is quite stable.
*
* @lucene.experimental
*/
public abstract class SpatialStrategy {
protected final SpatialContext ctx;
private final String fieldName;
/** Constructs the spatial strategy with its mandatory arguments. */
public SpatialStrategy(SpatialContext ctx, String fieldName) {
if (ctx == null) throw new IllegalArgumentException("ctx is required");
this.ctx = ctx;
if (fieldName == null || fieldName.length() == 0)
throw new IllegalArgumentException("fieldName is required");
this.fieldName = fieldName;
}
public SpatialContext getSpatialContext() {
return ctx;
}
/**
* The name of the field or the prefix of them if there are multiple fields needed internally.
*
* @return Not null.
*/
public String getFieldName() {
return fieldName;
}
/**
* Returns the IndexableField(s) from the {@code shape} that are to be added to the {@link
* org.apache.lucene.document.Document}. These fields are expected to be marked as indexed and not
* stored.
*
*
Note: If you want to store the shape as a string for retrieval in search results, you
* could add it like this:
*
*
document.add(new StoredField(fieldName,ctx.toString(shape)));
*
* The particular string representation used doesn't matter to the Strategy since it doesn't use
* it.
*
* @return Not null nor will it have null elements.
* @throws UnsupportedOperationException if given a shape incompatible with the strategy
*/
public abstract Field[] createIndexableFields(Shape shape);
/**
* See {@link #makeDistanceValueSource(org.locationtech.spatial4j.shape.Point, double)} called
* with a multiplier of 1.0 (i.e. units of degrees).
*/
public DoubleValuesSource makeDistanceValueSource(Point queryPoint) {
return makeDistanceValueSource(queryPoint, 1.0);
}
/**
* Make a ValueSource returning the distance between the center of the indexed shape and {@code
* queryPoint}. If there are multiple indexed shapes then the closest one is chosen. The result is
* multiplied by {@code multiplier}, which conveniently is used to get the desired units.
*/
public abstract DoubleValuesSource makeDistanceValueSource(Point queryPoint, double multiplier);
/**
* Make a Query based principally on {@link org.apache.lucene.spatial.query.SpatialOperation} and
* {@link Shape} from the supplied {@code args}. It should be constant scoring of 1.
*
* @throws UnsupportedOperationException If the strategy does not support the shape in {@code
* args}
* @throws org.apache.lucene.spatial.query.UnsupportedSpatialOperation If the strategy does not
* support the {@link org.apache.lucene.spatial.query.SpatialOperation} in {@code args}.
*/
public abstract Query makeQuery(SpatialArgs args);
/**
* Returns a ValueSource with values ranging from 1 to 0, depending inversely on the distance from
* {@link #makeDistanceValueSource(org.locationtech.spatial4j.shape.Point,double)}. The formula is
* {@code zScaling/(d + zScaling)} where 'd' is the distance and 'zScaling' is one tenth the
* distance to the farthest edge from the center. Thus the scores will be 1 for indexed points at
* the center of the query shape and as low as ~0.1 at its furthest edges.
*/
public final DoubleValuesSource makeRecipDistanceValueSource(Shape queryShape) {
Rectangle bbox = queryShape.getBoundingBox();
double diagonalDist =
ctx.getDistCalc()
.distance(
ctx.getShapeFactory().pointXY(bbox.getMinX(), bbox.getMinY()),
bbox.getMaxX(),
bbox.getMaxY());
double distToEdge = diagonalDist * 0.5;
float c = (float) distToEdge * 0.1f; // one tenth
DoubleValuesSource distance = makeDistanceValueSource(queryShape.getCenter(), 1.0);
return new ReciprocalDoubleValuesSource(c, distance);
}
@Override
public String toString() {
return getClass().getSimpleName() + " field:" + fieldName + " ctx=" + ctx;
}
}