package org.apache.lucene.search;
/**
* 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.BooleanClause.Occur;
/** Expert: A <code>Scorer</code> for documents matching a <code>Term</code>.
*/
final class TermScorer extends Scorer {
private DocsEnum docsEnum;
private byte[] norms;
private float weightValue;
private int doc = -1;
private int freq;
private int pointer;
private int pointerMax;
private static final int SCORE_CACHE_SIZE = 32;
private float[] scoreCache = new float[SCORE_CACHE_SIZE];
private int[] docs;
private int[] freqs;
private final DocsEnum.BulkReadResult bulkResult;
/**
* 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 similarity
* The </code>Similarity</code> implementation to be used for score
* computations.
* @param norms
* The field norms of the document fields for the <code>Term</code>.
*/
TermScorer(Weight weight, DocsEnum td, Similarity similarity, byte[] norms) {
super(similarity, weight);
this.docsEnum = td;
this.norms = norms;
this.weightValue = weight.getValue();
bulkResult = td.getBulkResult();
for (int i = 0; i < SCORE_CACHE_SIZE; i++)
scoreCache[i] = getSimilarity().tf(i) * weightValue;
}
@Override
public void score(Collector c) throws IOException {
score(c, Integer.MAX_VALUE, nextDoc());
}
private final void refillBuffer() throws IOException {
pointerMax = docsEnum.read(); // refill
docs = bulkResult.docs.ints;
freqs = bulkResult.freqs.ints;
}
// firstDocID is ignored since nextDoc() sets 'doc'
@Override
protected boolean score(Collector c, int end, int firstDocID) throws IOException {
c.setScorer(this);
while (doc < end) { // for docs in window
c.collect(doc); // collect score
if (++pointer >= pointerMax) {
refillBuffer();
if (pointerMax != 0) {
pointer = 0;
} else {
doc = NO_MORE_DOCS; // set to sentinel value
return false;
}
}
doc = docs[pointer];
freq = freqs[pointer];
}
return true;
}
@Override
public int docID() {
return doc;
}
@Override
public float freq() {
return freq;
}
/**
* Advances to the next document matching the query. <br>
* The iterator over the matching documents is buffered using
* {@link TermDocs#read(int[],int[])}.
*
* @return the document matching the query or NO_MORE_DOCS if there are no more documents.
*/
@Override
public int nextDoc() throws IOException {
pointer++;
if (pointer >= pointerMax) {
refillBuffer();
if (pointerMax != 0) {
pointer = 0;
} else {
return doc = NO_MORE_DOCS;
}
}
doc = docs[pointer];
freq = freqs[pointer];
assert doc != NO_MORE_DOCS;
return doc;
}
@Override
public float score() {
assert doc != NO_MORE_DOCS;
float raw = // compute tf(f)*weight
freq < SCORE_CACHE_SIZE // check cache
? scoreCache[freq] // cache hit
: getSimilarity().tf(freq)*weightValue; // cache miss
return norms == null ? raw : raw * getSimilarity().decodeNormValue(norms[doc]); // normalize for field
}
/**
* 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 {
// first scan in cache
for (pointer++; pointer < pointerMax; pointer++) {
if (docs[pointer] >= target) {
freq = freqs[pointer];
return doc = docs[pointer];
}
}
// not found in readahead cache, seek underlying stream
int newDoc = docsEnum.advance(target);
//System.out.println("ts.advance docsEnum=" + docsEnum);
if (newDoc != NO_MORE_DOCS) {
doc = newDoc;
freq = docsEnum.freq();
} else {
doc = NO_MORE_DOCS;
}
return doc;
}
/** Returns a string representation of this <code>TermScorer</code>. */
@Override
public String toString() { return "scorer(" + weight + ")"; }
}