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 * 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
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 * distributed under the License is distributed on an "AS IS" BASIS,
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package org.apache.lucene.queries.mlt;

import java.io.IOException;
import java.io.StringReader;
import java.util.Arrays;
import java.util.Objects;
import java.util.Set;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.BooleanClause;
import org.apache.lucene.search.BooleanQuery;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.QueryVisitor;

A simple wrapper for MoreLikeThis for use in scenarios where a Query object is required eg in custom QueryParser extensions. At query.rewrite() time the reader is used to construct the actual MoreLikeThis object and obtain the real Query object.
/** * A simple wrapper for MoreLikeThis for use in scenarios where a Query object is required eg * in custom QueryParser extensions. At query.rewrite() time the reader is used to construct the * actual MoreLikeThis object and obtain the real Query object. */
public class MoreLikeThisQuery extends Query { private String likeText; private String[] moreLikeFields; private Analyzer analyzer; private final String fieldName; private float percentTermsToMatch = 0.3f; private int minTermFrequency = 1; private int maxQueryTerms = 5; private Set<?> stopWords = null; private int minDocFreq = -1;
Params:
  • moreLikeFields – fields used for similarity measure
/** * @param moreLikeFields fields used for similarity measure */
public MoreLikeThisQuery(String likeText, String[] moreLikeFields, Analyzer analyzer, String fieldName) { this.likeText = Objects.requireNonNull(likeText); this.moreLikeFields = Objects.requireNonNull(moreLikeFields); this.analyzer = Objects.requireNonNull(analyzer); this.fieldName = Objects.requireNonNull(fieldName); } @Override public Query rewrite(IndexReader reader) throws IOException { MoreLikeThis mlt = new MoreLikeThis(reader); mlt.setFieldNames(moreLikeFields); mlt.setAnalyzer(analyzer); mlt.setMinTermFreq(minTermFrequency); if (minDocFreq >= 0) { mlt.setMinDocFreq(minDocFreq); } mlt.setMaxQueryTerms(maxQueryTerms); mlt.setStopWords(stopWords); BooleanQuery bq = (BooleanQuery) mlt.like(fieldName, new StringReader(likeText)); BooleanQuery.Builder newBq = new BooleanQuery.Builder(); for (BooleanClause clause : bq) { newBq.add(clause); } //make at least half the terms match newBq.setMinimumNumberShouldMatch((int) (bq.clauses().size() * percentTermsToMatch)); return newBq.build(); } /* (non-Javadoc) * @see org.apache.lucene.search.Query#toString(java.lang.String) */ @Override public String toString(String field) { return "like:" + likeText; } public float getPercentTermsToMatch() { return percentTermsToMatch; } public void setPercentTermsToMatch(float percentTermsToMatch) { this.percentTermsToMatch = percentTermsToMatch; } public Analyzer getAnalyzer() { return analyzer; } public void setAnalyzer(Analyzer analyzer) { this.analyzer = analyzer; } public String getLikeText() { return likeText; } public void setLikeText(String likeText) { this.likeText = likeText; } public int getMaxQueryTerms() { return maxQueryTerms; } public void setMaxQueryTerms(int maxQueryTerms) { this.maxQueryTerms = maxQueryTerms; } public int getMinTermFrequency() { return minTermFrequency; } public void setMinTermFrequency(int minTermFrequency) { this.minTermFrequency = minTermFrequency; } public String[] getMoreLikeFields() { return moreLikeFields; } public void setMoreLikeFields(String[] moreLikeFields) { this.moreLikeFields = moreLikeFields; } public Set<?> getStopWords() { return stopWords; } public void setStopWords(Set<?> stopWords) { this.stopWords = stopWords; } public int getMinDocFreq() { return minDocFreq; } public void setMinDocFreq(int minDocFreq) { this.minDocFreq = minDocFreq; } @Override public int hashCode() { final int prime = 31; int result = classHash(); result = prime * result + Objects.hash(analyzer, fieldName, likeText, stopWords); result = prime * result + maxQueryTerms; result = prime * result + minDocFreq; result = prime * result + minTermFrequency; result = prime * result + Arrays.hashCode(moreLikeFields); result = prime * result + Float.floatToIntBits(percentTermsToMatch); return result; } @Override public boolean equals(Object other) { return sameClassAs(other) && equalsTo(getClass().cast(other)); } private boolean equalsTo(MoreLikeThisQuery other) { return maxQueryTerms == other.maxQueryTerms && minDocFreq == other.minDocFreq && minTermFrequency == other.minTermFrequency && Float.floatToIntBits(percentTermsToMatch) == Float.floatToIntBits(other.percentTermsToMatch) && analyzer.equals(other.analyzer) && fieldName.equals(other.fieldName) && likeText.equals(other.likeText) && Arrays.equals(moreLikeFields, other.moreLikeFields) && Objects.equals(stopWords, other.stopWords); } @Override public void visit(QueryVisitor visitor) { visitor.visitLeaf(this); } }