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.
*/
import com.spatial4j.core.context.SpatialContext;
import com.spatial4j.core.shape.Point;
import com.spatial4j.core.shape.Rectangle;
import com.spatial4j.core.shape.Shape;
import org.apache.lucene.document.Field;
import org.apache.lucene.queries.function.ValueSource;
import org.apache.lucene.queries.function.valuesource.ReciprocalFloatFunction;
import org.apache.lucene.search.ConstantScoreQuery;
import org.apache.lucene.search.Filter;
import org.apache.lucene.search.Query;
import org.apache.lucene.spatial.query.SpatialArgs;
/**
* The SpatialStrategy encapsulates an approach to indexing and searching based
* on shapes.
* <p/>
* Different implementations will support different features. A strategy should
* document these common elements:
* <ul>
* <li>Can it index more than one shape per field?</li>
* <li>What types of shapes can be indexed?</li>
* <li>What types of query shapes can be used?</li>
* <li>What types of query operations are supported?
* This might vary per shape.</li>
* <li>Does it use the {@link org.apache.lucene.search.FieldCache},
* or some other type of cache? When?
* </ul>
* 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.
* <p/>
* Note that a SpatialStrategy is not involved with the Lucene stored field
* values of shapes, which is immaterial to indexing & search.
* <p/>
* Thread-safe.
*
* @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.
* <p/>
* Note: If you want to <i>store</i> the shape as a string for retrieval in
* search results, you could add it like this:
* <pre>document.add(new StoredField(fieldName,ctx.toString(shape)));</pre>
* 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(com.spatial4j.core.shape.Point, double)} called with
* a multiplier of 1.0 (i.e. units of degrees).
*/
public ValueSource 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 ValueSource 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}.
* The default implementation is
* <pre>return new ConstantScoreQuery(makeFilter(args));</pre>
*
* @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 Query makeQuery(SpatialArgs args) {
return new ConstantScoreQuery(makeFilter(args));
}
/**
* Make a Filter based principally on {@link org.apache.lucene.spatial.query.SpatialOperation}
* and {@link Shape} from the supplied {@code args}.
* <p />
* If a subclasses implements
* {@link #makeQuery(org.apache.lucene.spatial.query.SpatialArgs)}
* then this method could be simply:
* <pre>return new QueryWrapperFilter(makeQuery(args).getQuery());</pre>
*
* @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 Filter makeFilter(SpatialArgs args);
/**
* Returns a ValueSource with values ranging from 1 to 0, depending inversely
* on the distance from {@link #makeDistanceValueSource(com.spatial4j.core.shape.Point,double)}.
* The formula is {@code c/(d + c)} where 'd' is the distance and 'c' 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 ValueSource makeRecipDistanceValueSource(Shape queryShape) {
Rectangle bbox = queryShape.getBoundingBox();
double diagonalDist = ctx.getDistCalc().distance(
ctx.makePoint(bbox.getMinX(), bbox.getMinY()), bbox.getMaxX(), bbox.getMaxY());
double distToEdge = diagonalDist * 0.5;
float c = (float)distToEdge * 0.1f;//one tenth
return new ReciprocalFloatFunction(makeDistanceValueSource(queryShape.getCenter(), 1.0), 1f, c, c);
}
@Override
public String toString() {
return getClass().getSimpleName()+" field:"+fieldName+" ctx="+ctx;
}
}