/*
* 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.spans;
import java.io.IOException;
import java.util.Collections;
import java.util.Map;
import java.util.Objects;
import java.util.Set;
import org.apache.lucene.index.IndexReaderContext;
import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.index.PostingsEnum;
import org.apache.lucene.index.ReaderUtil;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermContext;
import org.apache.lucene.index.TermState;
import org.apache.lucene.index.Terms;
import org.apache.lucene.index.TermsEnum;
import org.apache.lucene.search.IndexSearcher;
/** Matches spans containing a term.
* This should not be used for terms that are indexed at position Integer.MAX_VALUE.
*/
public class SpanTermQuery extends SpanQuery {
protected final Term term;
protected final TermContext termContext;
/** Construct a SpanTermQuery matching the named term's spans. */
public SpanTermQuery(Term term) {
this.term = Objects.requireNonNull(term);
this.termContext = null;
}
/**
* Expert: Construct a SpanTermQuery matching the named term's spans, using
* the provided TermContext
*/
public SpanTermQuery(Term term, TermContext context) {
this.term = Objects.requireNonNull(term);
this.termContext = context;
}
/** Return the term whose spans are matched. */
public Term getTerm() { return term; }
@Override
public String getField() { return term.field(); }
@Override
public SpanWeight createWeight(IndexSearcher searcher, boolean needsScores, float boost) throws IOException {
final TermContext context;
final IndexReaderContext topContext = searcher.getTopReaderContext();
if (termContext == null || termContext.wasBuiltFor(topContext) == false) {
context = TermContext.build(topContext, term);
}
else {
context = termContext;
}
return new SpanTermWeight(context, searcher, needsScores ? Collections.singletonMap(term, context) : null, boost);
}
public class SpanTermWeight extends SpanWeight {
final TermContext termContext;
public SpanTermWeight(TermContext termContext, IndexSearcher searcher, Map<Term, TermContext> terms, float boost) throws IOException {
super(SpanTermQuery.this, searcher, terms, boost);
this.termContext = termContext;
assert termContext != null : "TermContext must not be null";
}
@Override
public void extractTerms(Set<Term> terms) {
terms.add(term);
}
@Override
public void extractTermContexts(Map<Term, TermContext> contexts) {
contexts.put(term, termContext);
}
@Override
public Spans getSpans(final LeafReaderContext context, Postings requiredPostings) throws IOException {
assert termContext.wasBuiltFor(ReaderUtil.getTopLevelContext(context)) : "The top-reader used to create Weight is not the same as the current reader's top-reader (" + ReaderUtil.getTopLevelContext(context);
final TermState state = termContext.get(context.ord);
if (state == null) { // term is not present in that reader
assert context.reader().docFreq(term) == 0 : "no termstate found but term exists in reader term=" + term;
return null;
}
final Terms terms = context.reader().terms(term.field());
if (terms == null)
return null;
if (terms.hasPositions() == false)
throw new IllegalStateException("field \"" + term.field() + "\" was indexed without position data; cannot run SpanTermQuery (term=" + term.text() + ")");
final TermsEnum termsEnum = terms.iterator();
termsEnum.seekExact(term.bytes(), state);
final PostingsEnum postings = termsEnum.postings(null, requiredPostings.getRequiredPostings());
float positionsCost = termPositionsCost(termsEnum) * PHRASE_TO_SPAN_TERM_POSITIONS_COST;
return new TermSpans(getSimScorer(context), postings, term, positionsCost);
}
}
/** A guess of
* the relative cost of dealing with the term positions
* when using a SpanNearQuery instead of a PhraseQuery.
*/
private static final float PHRASE_TO_SPAN_TERM_POSITIONS_COST = 4.0f;
private static final int TERM_POSNS_SEEK_OPS_PER_DOC = 128;
private static final int TERM_OPS_PER_POS = 7;
/** Returns an expected cost in simple operations
* of processing the occurrences of a term
* in a document that contains the term.
* <br>This may be inaccurate when {@link TermsEnum#totalTermFreq()} is not available.
* @param termsEnum The term is the term at which this TermsEnum is positioned.
* <p>
* This is a copy of org.apache.lucene.search.PhraseQuery.termPositionsCost().
* <br>
* TODO: keep only a single copy of this method and the constants used in it
* when SpanTermQuery moves to the o.a.l.search package.
*/
static float termPositionsCost(TermsEnum termsEnum) throws IOException {
int docFreq = termsEnum.docFreq();
assert docFreq > 0;
long totalTermFreq = termsEnum.totalTermFreq(); // -1 when not available
float expOccurrencesInMatchingDoc = (totalTermFreq < docFreq) ? 1 : (totalTermFreq / (float) docFreq);
return TERM_POSNS_SEEK_OPS_PER_DOC + expOccurrencesInMatchingDoc * TERM_OPS_PER_POS;
}
@Override
public String toString(String field) {
StringBuilder buffer = new StringBuilder();
if (term.field().equals(field))
buffer.append(term.text());
else
buffer.append(term.toString());
return buffer.toString();
}
@Override
public int hashCode() {
return classHash() ^ term.hashCode();
}
@Override
public boolean equals(Object other) {
return sameClassAs(other) &&
term.equals(((SpanTermQuery) other).term);
}
}