/*
* 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.
*/
package org.apache.lucene.search;
import java.io.IOException;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Map;
import java.util.PriorityQueue;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermContext;
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.BytesRefBuilder;
/**
* 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<B> extends TermCollectingRewrite<B> {
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 Query rewrite(final IndexReader reader, final MultiTermQuery query) throws IOException {
final int maxSize = Math.min(size, getMaxSize());
final PriorityQueue<ScoreTerm> stQueue = new PriorityQueue<>();
collectTerms(reader, query, new TermCollector() {
private final MaxNonCompetitiveBoostAttribute maxBoostAtt =
attributes.addAttribute(MaxNonCompetitiveBoostAttribute.class);
private final Map<BytesRef,ScoreTerm> visitedTerms = new HashMap<>();
private TermsEnum termsEnum;
private BoostAttribute boostAtt;
private ScoreTerm st;
@Override
public void setNextEnum(TermsEnum termsEnum) {
this.termsEnum = termsEnum;
assert compareToLastTerm(null);
// lazy init the initial ScoreTerm because comparator is not known on ctor:
if (st == null)
st = new ScoreTerm(new TermContext(topReaderContext));
boostAtt = termsEnum.attributes().addAttribute(BoostAttribute.class);
}
// for assert:
private BytesRefBuilder lastTerm;
private boolean compareToLastTerm(BytesRef t) {
if (lastTerm == null && t != null) {
lastTerm = new BytesRefBuilder();
lastTerm.append(t);
} else if (t == null) {
lastTerm = null;
} else {
assert lastTerm.get().compareTo(t) < 0: "lastTerm=" + lastTerm + " t=" + t;
lastTerm.copyBytes(t);
}
return true;
}
@Override
public boolean collect(BytesRef bytes) throws IOException {
final float boost = boostAtt.getBoost();
// make sure within a single seg we always collect
// terms in order
assert compareToLastTerm(bytes);
//System.out.println("TTR.collect term=" + bytes.utf8ToString() + " boost=" + boost + " ord=" + readerContext.ord);
// ignore uncompetitive hits
if (stQueue.size() == maxSize) {
final ScoreTerm t = stQueue.peek();
if (boost < t.boost)
return true;
if (boost == t.boost && bytes.compareTo(t.bytes.get()) > 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(), termsEnum.totalTermFreq());
} else {
// add new entry in PQ, we must clone the term, else it may get overwritten!
st.bytes.copyBytes(bytes);
st.boost = boost;
visitedTerms.put(st.bytes.get(), st);
assert st.termState.docFreq() == 0;
st.termState.register(state, readerContext.ord, termsEnum.docFreq(), termsEnum.totalTermFreq());
stQueue.offer(st);
// possibly drop entries from queue
if (stQueue.size() > maxSize) {
st = stQueue.poll();
visitedTerms.remove(st.bytes.get());
st.termState.clear(); // reset the termstate!
} else {
st = new ScoreTerm(new TermContext(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.get());
}
}
return true;
}
});
final B b = getTopLevelBuilder();
final ScoreTerm[] scoreTerms = stQueue.toArray(new ScoreTerm[stQueue.size()]);
ArrayUtil.timSort(scoreTerms, scoreTermSortByTermComp);
for (final ScoreTerm st : scoreTerms) {
final Term term = new Term(query.field, st.bytes.toBytesRef());
// We allow negative term scores (fuzzy query does this, for example) while collecting the terms,
// but truncate such boosts to 0.0f when building the query:
addClause(b, term, st.termState.docFreq(), Math.max(0.0f, st.boost), st.termState); // add to query
}
return build(b);
}
@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>() {
@Override
public int compare(ScoreTerm st1, ScoreTerm st2) {
return st1.bytes.get().compareTo(st2.bytes.get());
}
};
static final class ScoreTerm implements Comparable<ScoreTerm> {
public final BytesRefBuilder bytes = new BytesRefBuilder();
public float boost;
public final TermContext termState;
public ScoreTerm(TermContext termState) {
this.termState = termState;
}
@Override
public int compareTo(ScoreTerm other) {
if (this.boost == other.boost)
return other.bytes.get().compareTo(this.bytes.get());
else
return Float.compare(this.boost, other.boost);
}
}
}