--- /dev/null
+package org.apache.lucene.search.highlight;
+/**
+ * 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.HashSet;
+import java.util.Iterator;
+
+import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.Term;
+import org.apache.lucene.search.BooleanClause;
+import org.apache.lucene.search.BooleanQuery;
+import org.apache.lucene.search.FilteredQuery;
+import org.apache.lucene.search.Query;
+import org.apache.lucene.util.StringHelper;
+
+/**
+ * Utility class used to extract the terms used in a query, plus any weights.
+ * This class will not find terms for MultiTermQuery, TermRangeQuery and PrefixQuery classes
+ * so the caller must pass a rewritten query (see Query.rewrite) to obtain a list of
+ * expanded terms.
+ *
+ */
+public final class QueryTermExtractor
+{
+
+ /**
+ * Extracts all terms texts of a given Query into an array of WeightedTerms
+ *
+ * @param query Query to extract term texts from
+ * @return an array of the terms used in a query, plus their weights.
+ */
+ public static final WeightedTerm[] getTerms(Query query)
+ {
+ return getTerms(query,false);
+ }
+
+ /**
+ * Extracts all terms texts of a given Query into an array of WeightedTerms
+ *
+ * @param query Query to extract term texts from
+ * @param reader used to compute IDF which can be used to a) score selected fragments better
+ * b) use graded highlights eg changing intensity of font color
+ * @param fieldName the field on which Inverse Document Frequency (IDF) calculations are based
+ * @return an array of the terms used in a query, plus their weights.
+ */
+ public static final WeightedTerm[] getIdfWeightedTerms(Query query, IndexReader reader, String fieldName)
+ {
+ WeightedTerm[] terms=getTerms(query,false, fieldName);
+ int totalNumDocs=reader.numDocs();
+ for (int i = 0; i < terms.length; i++)
+ {
+ try
+ {
+ int docFreq=reader.docFreq(new Term(fieldName,terms[i].term));
+ // docFreq counts deletes
+ if(totalNumDocs < docFreq) {
+ docFreq = totalNumDocs;
+ }
+ //IDF algorithm taken from DefaultSimilarity class
+ float idf=(float)(Math.log((float)totalNumDocs/(double)(docFreq+1)) + 1.0);
+ terms[i].weight*=idf;
+ }
+ catch (IOException e)
+ {
+ //ignore
+ }
+ }
+ return terms;
+ }
+
+ /**
+ * Extracts all terms texts of a given Query into an array of WeightedTerms
+ *
+ * @param query Query to extract term texts from
+ * @param prohibited <code>true</code> to extract "prohibited" terms, too
+ * @param fieldName The fieldName used to filter query terms
+ * @return an array of the terms used in a query, plus their weights.
+ */
+ public static final WeightedTerm[] getTerms(Query query, boolean prohibited, String fieldName)
+ {
+ HashSet<WeightedTerm> terms=new HashSet<WeightedTerm>();
+ if(fieldName!=null)
+ {
+ fieldName= StringHelper.intern(fieldName);
+ }
+ getTerms(query,terms,prohibited,fieldName);
+ return terms.toArray(new WeightedTerm[0]);
+ }
+
+ /**
+ * Extracts all terms texts of a given Query into an array of WeightedTerms
+ *
+ * @param query Query to extract term texts from
+ * @param prohibited <code>true</code> to extract "prohibited" terms, too
+ * @return an array of the terms used in a query, plus their weights.
+ */
+ public static final WeightedTerm[] getTerms(Query query, boolean prohibited)
+ {
+ return getTerms(query,prohibited,null);
+ }
+
+ //fieldname MUST be interned prior to this call
+ private static final void getTerms(Query query, HashSet<WeightedTerm> terms,boolean prohibited, String fieldName)
+ {
+ try
+ {
+ if (query instanceof BooleanQuery)
+ getTermsFromBooleanQuery((BooleanQuery) query, terms, prohibited, fieldName);
+ else
+ if(query instanceof FilteredQuery)
+ getTermsFromFilteredQuery((FilteredQuery)query, terms,prohibited, fieldName);
+ else
+ {
+ HashSet<Term> nonWeightedTerms=new HashSet<Term>();
+ query.extractTerms(nonWeightedTerms);
+ for (Iterator<Term> iter = nonWeightedTerms.iterator(); iter.hasNext();)
+ {
+ Term term = iter.next();
+ if((fieldName==null)||(term.field()==fieldName))
+ {
+ terms.add(new WeightedTerm(query.getBoost(),term.text()));
+ }
+ }
+ }
+ }
+ catch(UnsupportedOperationException ignore)
+ {
+ //this is non-fatal for our purposes
+ }
+ }
+
+ /**
+ * extractTerms is currently the only query-independent means of introspecting queries but it only reveals
+ * a list of terms for that query - not the boosts each individual term in that query may or may not have.
+ * "Container" queries such as BooleanQuery should be unwrapped to get at the boost info held
+ * in each child element.
+ * Some discussion around this topic here:
+ * http://www.gossamer-threads.com/lists/lucene/java-dev/34208?search_string=introspection;#34208
+ * Unfortunately there seemed to be limited interest in requiring all Query objects to implement
+ * something common which would allow access to child queries so what follows here are query-specific
+ * implementations for accessing embedded query elements.
+ */
+ private static final void getTermsFromBooleanQuery(BooleanQuery query, HashSet<WeightedTerm> terms, boolean prohibited, String fieldName)
+ {
+ BooleanClause[] queryClauses = query.getClauses();
+ for (int i = 0; i < queryClauses.length; i++)
+ {
+ if (prohibited || queryClauses[i].getOccur()!=BooleanClause.Occur.MUST_NOT)
+ getTerms(queryClauses[i].getQuery(), terms, prohibited, fieldName);
+ }
+ }
+ private static void getTermsFromFilteredQuery(FilteredQuery query, HashSet<WeightedTerm> terms, boolean prohibited, String fieldName)
+ {
+ getTerms(query.getQuery(),terms,prohibited,fieldName);
+ }
+
+}
fnp / pylucene.git / blobdiff