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* Created on 25-Jan-2006
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package org.apache.lucene.search.similar;
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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import java.io.IOException;
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import org.apache.lucene.analysis.Analyzer;
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import org.apache.lucene.index.IndexReader;
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import org.apache.lucene.search.BooleanClause;
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import org.apache.lucene.search.BooleanQuery;
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import org.apache.lucene.search.Query;
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import org.apache.lucene.search.similar.MoreLikeThis;
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import java.io.StringReader;
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* A simple wrapper for MoreLikeThis for use in scenarios where a Query object
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* is required eg in custom QueryParser extensions. At query.rewrite() time the
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* reader is used to construct the actual MoreLikeThis object and obtain the
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public class MoreLikeThisQuery extends Query {
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private String likeText;
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private String[] moreLikeFields;
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private Analyzer analyzer;
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private String fieldName;
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private float percentTermsToMatch = 0.3f;
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private int minTermFrequency = 1;
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private int maxQueryTerms = 5;
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private Set<?> stopWords = null;
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private int minDocFreq = -1;
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/** @deprecated use {@link #MoreLikeThisQuery(String, String[], Analyzer, String)} instead. */
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public MoreLikeThisQuery(String likeText, String[] moreLikeFields, Analyzer analyzer) {
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this(likeText, moreLikeFields, analyzer, moreLikeFields[0]);
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* @param moreLikeFields
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public MoreLikeThisQuery(String likeText, String[] moreLikeFields, Analyzer analyzer, String fieldName) {
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this.likeText = likeText;
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this.moreLikeFields = moreLikeFields;
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this.analyzer = analyzer;
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this.fieldName = fieldName;
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public Query rewrite(IndexReader reader) throws IOException {
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MoreLikeThis mlt = new MoreLikeThis(reader);
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mlt.setFieldNames(moreLikeFields);
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mlt.setAnalyzer(analyzer);
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mlt.setMinTermFreq(minTermFrequency);
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if (minDocFreq >= 0) {
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mlt.setMinDocFreq(minDocFreq);
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mlt.setMaxQueryTerms(maxQueryTerms);
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mlt.setStopWords(stopWords);
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BooleanQuery bq = (BooleanQuery) mlt.like(new StringReader(likeText), fieldName);
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BooleanClause[] clauses = bq.getClauses();
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// make at least half the terms match
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bq.setMinimumNumberShouldMatch((int) (clauses.length * percentTermsToMatch));
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* @see org.apache.lucene.search.Query#toString(java.lang.String)
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public String toString(String field) {
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return "like:" + likeText;
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public float getPercentTermsToMatch() {
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return percentTermsToMatch;
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public void setPercentTermsToMatch(float percentTermsToMatch) {
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this.percentTermsToMatch = percentTermsToMatch;
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public Analyzer getAnalyzer() {
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public void setAnalyzer(Analyzer analyzer) {
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this.analyzer = analyzer;
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public String getLikeText() {
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public void setLikeText(String likeText) {
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this.likeText = likeText;
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public int getMaxQueryTerms() {
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return maxQueryTerms;
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public void setMaxQueryTerms(int maxQueryTerms) {
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this.maxQueryTerms = maxQueryTerms;
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public int getMinTermFrequency() {
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return minTermFrequency;
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public void setMinTermFrequency(int minTermFrequency) {
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this.minTermFrequency = minTermFrequency;
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public String[] getMoreLikeFields() {
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return moreLikeFields;
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public void setMoreLikeFields(String[] moreLikeFields) {
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this.moreLikeFields = moreLikeFields;
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public Set<?> getStopWords() {
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public void setStopWords(Set<?> stopWords) {
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this.stopWords = stopWords;
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public int getMinDocFreq() {
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public void setMinDocFreq(int minDocFreq) {
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this.minDocFreq = minDocFreq;