package org.apache.lucene.search;
/**
* Copyright 2004 The Apache Software Foundation
*
* Licensed 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 org.apache.lucene.index.IndexReader;
import java.io.IOException;
import java.util.BitSet;
/**
* A query that wraps a filter and simply returns a constant score equal to the
* query boost for every document in the filter.
*
* @author yonik
* @version $Id$
*/
public class ConstantScoreQuery extends Query {
protected final Filter filter;
public ConstantScoreQuery(Filter filter) {
this.filter=filter;
}
public Query rewrite(IndexReader reader) throws IOException {
return this;
}
protected class ConstantWeight implements Weight {
private Searcher searcher;
private float queryNorm;
private float queryWeight;
public ConstantWeight(Searcher searcher) {
this.searcher = searcher;
}
public Query getQuery() {
return ConstantScoreQuery.this;
}
public float getValue() {
return queryWeight;
}
public float sumOfSquaredWeights() throws IOException {
queryWeight = getBoost();
return queryWeight * queryWeight;
}
public void normalize(float norm) {
this.queryNorm = norm;
queryWeight *= this.queryNorm;
}
public Scorer scorer(IndexReader reader) throws IOException {
return new ConstantScorer(getSimilarity(searcher), reader, this);
}
public Explanation explain(IndexReader reader, int doc) throws IOException {
ConstantScorer cs = (ConstantScorer)scorer(reader);
boolean exists = cs.bits.get(doc);
Explanation result = new Explanation();
if (exists) {
result.setDescription("ConstantScoreQuery(" + filter
+ "), product of:");
result.setValue(queryWeight);
result.addDetail(new Explanation(getBoost(), "boost"));
result.addDetail(new Explanation(queryNorm,"queryNorm"));
} else {
result.setDescription("ConstantScoreQuery(" + filter
+ ") doesn't match id " + doc);
result.setValue(0);
}
return result;
}
}
protected class ConstantScorer extends Scorer {
final BitSet bits;
final float theScore;
int doc=-1;
public ConstantScorer(Similarity similarity, IndexReader reader, Weight w) throws IOException {
super(similarity);
theScore = w.getValue();
bits = filter.bits(reader);
}
public boolean next() throws IOException {
doc = bits.nextSetBit(doc+1);
return doc >= 0;
}
public int doc() {
return doc;
}
public float score() throws IOException {
return theScore;
}
public boolean skipTo(int target) throws IOException {
doc = bits.nextSetBit(target); // requires JDK 1.4
return doc >= 0;
}
public Explanation explain(int doc) throws IOException {
throw new UnsupportedOperationException();
}
}
protected Weight createWeight(Searcher searcher) {
return new ConstantScoreQuery.ConstantWeight(searcher);
}
/** Prints a user-readable version of this query. */
public String toString(String field)
{
return "ConstantScore(" + filter.toString()
+ (getBoost()==1.0 ? ")" : "^" + getBoost());
}
/** Returns true if <code>o</code> is equal to this. */
public boolean equals(Object o) {
if (this == o) return true;
if (!(o instanceof ConstantScoreQuery)) return false;
ConstantScoreQuery other = (ConstantScoreQuery)o;
return this.getBoost()==other.getBoost() && filter.equals(other.filter);
}
/** Returns a hash code value for this object. */
public int hashCode() {
// Simple add is OK since no existing filter hashcode has a float component.
return filter.hashCode() + Float.floatToIntBits(getBoost());
}
}
|