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.Set;
import java.util.Vector;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermPositions;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.util.ToStringUtils;
/** A Query that matches documents containing a particular sequence of terms.
* A PhraseQuery is built by QueryParser for input like <code>"new york"</code>.
*
* <p>This query may be combined with other terms or queries with a {@link BooleanQuery}.
*/
public class PhraseQuery extends Query {
private String field;
private Vector terms = new Vector();
private Vector positions = new Vector();
private int slop = 0;
/** Constructs an empty phrase query. */
public PhraseQuery() {}
/** Sets the number of other words permitted between words in query phrase.
If zero, then this is an exact phrase search. For larger values this works
like a <code>WITHIN</code> or <code>NEAR</code> operator.
<p>The slop is in fact an edit-distance, where the units correspond to
moves of terms in the query phrase out of position. For example, to switch
the order of two words requires two moves (the first move places the words
atop one another), so to permit re-orderings of phrases, the slop must be
at least two.
<p>More exact matches are scored higher than sloppier matches, thus search
results are sorted by exactness.
<p>The slop is zero by default, requiring exact matches.*/
public void setSlop(int s) { slop = s; }
/** Returns the slop. See setSlop(). */
public int getSlop() { return slop; }
/**
* Adds a term to the end of the query phrase.
* The relative position of the term is the one immediately after the last term added.
*/
public void add(Term term) {
int position = 0;
if(positions.size() > 0)
position = ((Integer) positions.lastElement()).intValue() + 1;
add(term, position);
}
/**
* Adds a term to the end of the query phrase.
* The relative position of the term within the phrase is specified explicitly.
* This allows e.g. phrases with more than one term at the same position
* or phrases with gaps (e.g. in connection with stopwords).
*
* @param term
* @param position
*/
public void add(Term term, int position) {
if (terms.size() == 0)
field = term.field();
else if (term.field() != field)
throw new IllegalArgumentException("All phrase terms must be in the same field: " + term);
terms.addElement(term);
positions.addElement(new Integer(position));
}
/** Returns the set of terms in this phrase. */
public Term[] getTerms() {
return (Term[])terms.toArray(new Term[0]);
}
/**
* Returns the relative positions of terms in this phrase.
*/
public int[] getPositions() {
int[] result = new int[positions.size()];
for(int i = 0; i < positions.size(); i++)
result[i] = ((Integer) positions.elementAt(i)).intValue();
return result;
}
private class PhraseWeight implements Weight {
private Similarity similarity;
private float value;
private float idf;
private float queryNorm;
private float queryWeight;
public PhraseWeight(Searcher searcher)
throws IOException {
this.similarity = getSimilarity(searcher);
idf = similarity.idf(terms, searcher);
}
public String toString() { return "weight(" + PhraseQuery.this + ")"; }
public Query getQuery() { return PhraseQuery.this; }
public float getValue() { return value; }
public float sumOfSquaredWeights() {
queryWeight = idf * getBoost(); // compute query weight
return queryWeight * queryWeight; // square it
}
public void normalize(float queryNorm) {
this.queryNorm = queryNorm;
queryWeight *= queryNorm; // normalize query weight
value = queryWeight * idf; // idf for document
}
public Scorer scorer(IndexReader reader) throws IOException {
if (terms.size() == 0) // optimize zero-term case
return null;
TermPositions[] tps = new TermPositions[terms.size()];
for (int i = 0; i < terms.size(); i++) {
TermPositions p = reader.termPositions((Term)terms.elementAt(i));
if (p == null)
return null;
tps[i] = p;
}
if (slop == 0) // optimize exact case
return new ExactPhraseScorer(this, tps, getPositions(), similarity,
reader.norms(field));
else
return
new SloppyPhraseScorer(this, tps, getPositions(), similarity, slop,
reader.norms(field));
}
public Explanation explain(IndexReader reader, int doc)
throws IOException {
Explanation result = new Explanation();
result.setDescription("weight("+getQuery()+" in "+doc+"), product of:");
StringBuffer docFreqs = new StringBuffer();
StringBuffer query = new StringBuffer();
query.append('\"');
for (int i = 0; i < terms.size(); i++) {
if (i != 0) {
docFreqs.append(" ");
query.append(" ");
}
Term term = (Term)terms.elementAt(i);
docFreqs.append(term.text());
docFreqs.append("=");
docFreqs.append(reader.docFreq(term));
query.append(term.text());
}
query.append('\"');
Explanation idfExpl =
new Explanation(idf, "idf(" + field + ": " + docFreqs + ")");
// explain query weight
Explanation queryExpl = new Explanation();
queryExpl.setDescription("queryWeight(" + getQuery() + "), product of:");
Explanation boostExpl = new Explanation(getBoost(), "boost");
if (getBoost() != 1.0f)
queryExpl.addDetail(boostExpl);
queryExpl.addDetail(idfExpl);
Explanation queryNormExpl = new Explanation(queryNorm,"queryNorm");
queryExpl.addDetail(queryNormExpl);
queryExpl.setValue(boostExpl.getValue() *
idfExpl.getValue() *
queryNormExpl.getValue());
result.addDetail(queryExpl);
// explain field weight
Explanation fieldExpl = new Explanation();
fieldExpl.setDescription("fieldWeight("+field+":"+query+" in "+doc+
"), product of:");
Explanation tfExpl = scorer(reader).explain(doc);
fieldExpl.addDetail(tfExpl);
fieldExpl.addDetail(idfExpl);
Explanation fieldNormExpl = new Explanation();
byte[] fieldNorms = reader.norms(field);
float fieldNorm =
fieldNorms!=null ? Similarity.decodeNorm(fieldNorms[doc]) : 0.0f;
fieldNormExpl.setValue(fieldNorm);
fieldNormExpl.setDescription("fieldNorm(field="+field+", doc="+doc+")");
fieldExpl.addDetail(fieldNormExpl);
fieldExpl.setValue(tfExpl.getValue() *
idfExpl.getValue() *
fieldNormExpl.getValue());
result.addDetail(fieldExpl);
// combine them
result.setValue(queryExpl.getValue() * fieldExpl.getValue());
if (queryExpl.getValue() == 1.0f)
return fieldExpl;
return result;
}
}
protected Weight createWeight(Searcher searcher) throws IOException {
if (terms.size() == 1) { // optimize one-term case
Term term = (Term)terms.elementAt(0);
Query termQuery = new TermQuery(term);
termQuery.setBoost(getBoost());
return termQuery.createWeight(searcher);
}
return new PhraseWeight(searcher);
}
/**
* @see org.apache.lucene.search.Query#extractTerms(java.util.Set)
*/
public void extractTerms(Set queryTerms) {
queryTerms.addAll(terms);
}
/** Prints a user-readable version of this query. */
public String toString(String f) {
StringBuffer buffer = new StringBuffer();
if (!field.equals(f)) {
buffer.append(field);
buffer.append(":");
}
buffer.append("\"");
for (int i = 0; i < terms.size(); i++) {
buffer.append(((Term)terms.elementAt(i)).text());
if (i != terms.size()-1)
buffer.append(" ");
}
buffer.append("\"");
if (slop != 0) {
buffer.append("~");
buffer.append(slop);
}
buffer.append(ToStringUtils.boost(getBoost()));
return buffer.toString();
}
/** Returns true iff <code>o</code> is equal to this. */
public boolean equals(Object o) {
if (!(o instanceof PhraseQuery))
return false;
PhraseQuery other = (PhraseQuery)o;
return (this.getBoost() == other.getBoost())
&& (this.slop == other.slop)
&& this.terms.equals(other.terms)
&& this.positions.equals(other.positions);
}
/** Returns a hash code value for this object.*/
public int hashCode() {
return Float.floatToIntBits(getBoost())
^ slop
^ terms.hashCode()
^ positions.hashCode();
}
}
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