TermScorer.java

package doser.lucene.query;

/*
 * 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 java.io.IOException;

import org.apache.lucene.index.DocsEnum;
import org.apache.lucene.search.Scorer;
import org.apache.lucene.search.Weight;
import org.apache.lucene.search.similarities.Similarity;

/**
 * Expert: A <code>Scorer</code> for documents matching a <code>Term</code>.
 */
final class TermScorer extends Scorer {
	private final Similarity.SimScorer docScorer;
	private final DocsEnum docsEnum;

	/**
	 * Construct a <code>TermScorer</code>.
	 * 
	 * @param weight
	 *            The weight of the <code>Term</code> in the query.
	 * @param docsEnum
	 *            An iterator over the documents matching the <code>Term</code>.
	 * @param docScorer
	 *            The </code>Similarity.SimScorer</code> implementation to be
	 *            used for score computations.
	 */
	TermScorer(final Weight weight, final DocsEnum docsEnum,
			final Similarity.SimScorer docScorer) {
		super(weight);
		this.docScorer = docScorer;
		this.docsEnum = docsEnum;
	}

	/**
	 * Advances to the first match beyond the current whose document number is
	 * greater than or equal to a given target. <br>
	 * The implementation uses {@link DocsEnum#advance(int)}.
	 * 
	 * @param target
	 *            The target document number.
	 * @return the matching document or NO_MORE_DOCS if none exist.
	 */
	@Override
	public int advance(final int target) throws IOException {
		return docsEnum.advance(target);
	}

	@Override
	public long cost() {
		return docsEnum.cost();
	}

	@Override
	public int docID() {
		return docsEnum.docID();
	}

	@Override
	public int freq() throws IOException {
		return docsEnum.freq();
	}

	/**
	 * Advances to the next document matching the query. <br>
	 * 
	 * @return the document matching the query or NO_MORE_DOCS if there are no
	 *         more documents.
	 */
	@Override
	public int nextDoc() throws IOException {
		return docsEnum.nextDoc();
	}

	@Override
	public float score() throws IOException {
		assert docID() != NO_MORE_DOCS;
		return docScorer.score(docsEnum.docID(), docsEnum.freq());
	}

	/** Returns a string representation of this <code>TermScorer</code>. */
	@Override
	public String toString() {
		return "scorer(" + weight + ")";
	}
}

// import java.io.IOException;
//
// import org.apache.lucene.index.DocsEnum;
// import org.apache.lucene.search.Scorer;
// import org.apache.lucene.search.Weight;
// import org.apache.lucene.search.similarities.Similarity;
//
// /** Expert: A <code>Scorer</code> for documents matching a <code>Term</code>.
// */
// final class TermScorer extends Scorer {
// private final DocsEnum docsEnum;
// private final Similarity.ExactSimScorer docScorer;
// private final int docFreq;
//
// /**
// * Construct a <code>TermScorer</code>.
// *
// * @param weight
// * The weight of the <code>Term</code> in the query.
// * @param td
// * An iterator over the documents matching the <code>Term</code>.
// * @param docScorer
// * The </code>Similarity.ExactSimScorer</code> implementation
// * to be used for score computations.
// * @param docFreq
// * per-segment docFreq of this term
// */
// TermScorer(Weight weight, DocsEnum td, Similarity.ExactSimScorer docScorer,
// int docFreq) {
// super(weight);
// this.docScorer = docScorer;
// this.docsEnum = td;
// this.docFreq = docFreq;
// }
//
// @Override
// public int docID() {
// return docsEnum.docID();
// }
//
// @Override
// public int freq() throws IOException {
// return docsEnum.freq();
// }
//
// /**
// * Advances to the next document matching the query. <br>
// *
// * @return the document matching the query or NO_MORE_DOCS if there are no
// more documents.
// */
// @Override
// public int nextDoc() throws IOException {
// return docsEnum.nextDoc();
// }
//
// @Override
// public float score() throws IOException {
// assert docID() != NO_MORE_DOCS;
// return docScorer.score(docsEnum.docID(), docsEnum.freq());
// }
//
// /**
// * Advances to the first match beyond the current whose document number is
// * greater than or equal to a given target. <br>
// * The implementation uses {@link DocsEnum#advance(int)}.
// *
// * @param target
// * The target document number.
// * @return the matching document or NO_MORE_DOCS if none exist.
// */
// @Override
// public int advance(int target) throws IOException {
// return docsEnum.advance(target);
// }
//
// /** Returns a string representation of this <code>TermScorer</code>. */
// @Override
// public String toString() { return "scorer(" + weight + ")"; }
//
// // TODO: benchmark if the specialized conjunction really benefits
// // from this, or if instead its from sorting by docFreq, or both
//
// DocsEnum getDocsEnum() {
// return docsEnum;
// }
//
// // TODO: generalize something like this for scorers?
// // even this is just an estimation...
//
// int getDocFreq() {
// return docFreq;
// }
// }