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 java.util.HashMap;
import java.util.Map;
import java.util.PriorityQueue;
import java.util.Comparator;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermState;
import org.apache.lucene.index.TermsEnum;
import org.apache.lucene.util.ArrayUtil;
import org.apache.lucene.util.BytesRef;
import org.apache.lucene.util.PerReaderTermState;
/**
* Base rewrite method for collecting only the top terms
* via a priority queue.
* @lucene.internal Only public to be accessible by spans package.
*/
public abstract class TopTermsRewrite<Q extends Query> extends TermCollectingRewrite<Q> {
private final int size;
/**
* Create a TopTermsBooleanQueryRewrite for
* at most <code>size</code> terms.
* <p>
* NOTE: if {@link BooleanQuery#getMaxClauseCount} is smaller than
* <code>size</code>, then it will be used instead.
*/
public TopTermsRewrite(int size) {
this.size = size;
}
/** return the maximum priority queue size */
public int getSize() {
return size;
}
/** return the maximum size of the priority queue (for boolean rewrites this is BooleanQuery#getMaxClauseCount). */
protected abstract int getMaxSize();
@Override
public final Q rewrite(final IndexReader reader, final MultiTermQuery query) throws IOException {
final int maxSize = Math.min(size, getMaxSize());
final PriorityQueue<ScoreTerm> stQueue = new PriorityQueue<ScoreTerm>();
collectTerms(reader, query, new TermCollector() {
private final MaxNonCompetitiveBoostAttribute maxBoostAtt =
attributes.addAttribute(MaxNonCompetitiveBoostAttribute.class);
private final Map<BytesRef,ScoreTerm> visitedTerms = new HashMap<BytesRef,ScoreTerm>();
private TermsEnum termsEnum;
private Comparator<BytesRef> termComp;
private BoostAttribute boostAtt;
private ScoreTerm st;
@Override
public void setNextEnum(TermsEnum termsEnum) throws IOException {
this.termsEnum = termsEnum;
this.termComp = termsEnum.getComparator();
// lazy init the initial ScoreTerm because comparator is not known on ctor:
if (st == null)
st = new ScoreTerm(this.termComp, new PerReaderTermState(topReaderContext));
boostAtt = termsEnum.attributes().addAttribute(BoostAttribute.class);
}
@Override
public boolean collect(BytesRef bytes) throws IOException {
final float boost = boostAtt.getBoost();
// ignore uncompetitive hits
if (stQueue.size() == maxSize) {
final ScoreTerm t = stQueue.peek();
if (boost < t.boost)
return true;
if (boost == t.boost && termComp.compare(bytes, t.bytes) > 0)
return true;
}
ScoreTerm t = visitedTerms.get(bytes);
final TermState state = termsEnum.termState();
assert state != null;
if (t != null) {
// if the term is already in the PQ, only update docFreq of term in PQ
assert t.boost == boost : "boost should be equal in all segment TermsEnums";
t.termState.register(state, readerContext.ord, termsEnum.docFreq());
} else {
// add new entry in PQ, we must clone the term, else it may get overwritten!
st.bytes.copy(bytes);
st.boost = boost;
visitedTerms.put(st.bytes, st);
assert st.termState.docFreq() == 0;
st.termState.register(state, readerContext.ord, termsEnum.docFreq());
stQueue.offer(st);
// possibly drop entries from queue
if (stQueue.size() > maxSize) {
st = stQueue.poll();
visitedTerms.remove(st.bytes);
st.termState.clear(); // reset the termstate!
} else {
st = new ScoreTerm(termComp, new PerReaderTermState(topReaderContext));
}
assert stQueue.size() <= maxSize : "the PQ size must be limited to maxSize";
// set maxBoostAtt with values to help FuzzyTermsEnum to optimize
if (stQueue.size() == maxSize) {
t = stQueue.peek();
maxBoostAtt.setMaxNonCompetitiveBoost(t.boost);
maxBoostAtt.setCompetitiveTerm(t.bytes);
}
}
return true;
}
});
final Term placeholderTerm = new Term(query.field);
final Q q = getTopLevelQuery();
final ScoreTerm[] scoreTerms = stQueue.toArray(new ScoreTerm[stQueue.size()]);
ArrayUtil.quickSort(scoreTerms, scoreTermSortByTermComp);
for (final ScoreTerm st : scoreTerms) {
final Term term = placeholderTerm.createTerm(st.bytes);
assert reader.docFreq(term) == st.termState.docFreq() : "reader DF is " + reader.docFreq(term) + " vs " + st.termState.docFreq();
addClause(q, term, st.termState.docFreq(), query.getBoost() * st.boost, st.termState); // add to query
}
query.incTotalNumberOfTerms(scoreTerms.length);
return q;
}
@Override
public int hashCode() {
return 31 * size;
}
@Override
public boolean equals(Object obj) {
if (this == obj) return true;
if (obj == null) return false;
if (getClass() != obj.getClass()) return false;
final TopTermsRewrite<?> other = (TopTermsRewrite<?>) obj;
if (size != other.size) return false;
return true;
}
private static final Comparator<ScoreTerm> scoreTermSortByTermComp =
new Comparator<ScoreTerm>() {
public int compare(ScoreTerm st1, ScoreTerm st2) {
assert st1.termComp == st2.termComp :
"term comparator should not change between segments";
return st1.termComp.compare(st1.bytes, st2.bytes);
}
};
static final class ScoreTerm implements Comparable<ScoreTerm> {
public final Comparator<BytesRef> termComp;
public final BytesRef bytes = new BytesRef();
public float boost;
public final PerReaderTermState termState;
public ScoreTerm(Comparator<BytesRef> termComp, PerReaderTermState termState) {
this.termComp = termComp;
this.termState = termState;
}
public int compareTo(ScoreTerm other) {
if (this.boost == other.boost)
return termComp.compare(other.bytes, this.bytes);
else
return Float.compare(this.boost, other.boost);
}
}
}