+++ /dev/null
-/**
- * Copyright 2004 The Apache Software Foundation.
- *
- * Licensed 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.similar;
-
-import java.io.IOException;
-import java.io.StringReader;
-import java.util.HashSet;
-import java.util.Set;
-
-import org.apache.lucene.analysis.Analyzer;
-import org.apache.lucene.analysis.TokenStream;
-import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
-import org.apache.lucene.index.Term;
-import org.apache.lucene.search.BooleanClause;
-import org.apache.lucene.search.BooleanQuery;
-import org.apache.lucene.search.IndexSearcher;
-import org.apache.lucene.search.Query;
-import org.apache.lucene.search.TermQuery;
-
-/**
- * Simple similarity measures.
- *
- * @see MoreLikeThis
- */
-public final class SimilarityQueries
-{
- /**
- *
- */
- private SimilarityQueries()
- {
- }
-
- /**
- * Simple similarity query generators.
- * Takes every unique word and forms a boolean query where all words are optional.
- * After you get this you'll use to to query your {@link IndexSearcher} for similar docs.
- * The only caveat is the first hit returned <b>should be</b> your source document - you'll
- * need to then ignore that.
- *
- * <p>
- * So, if you have a code fragment like this:
- * <br>
- * <code>
- * Query q = formSimilaryQuery( "I use Lucene to search fast. Fast searchers are good", new StandardAnalyzer(), "contents", null);
- * </code>
- *
- * <p>
- * The query returned, in string form, will be <code>'(i use lucene to search fast searchers are good')</code>.
- *
- * <p>
- * The philosophy behind this method is "two documents are similar if they share lots of words".
- * Note that behind the scenes, Lucene's scoring algorithm will tend to give two documents a higher similarity score if the share more uncommon words.
- *
- * <P>
- * This method is fail-safe in that if a long 'body' is passed in and
- * {@link BooleanQuery#add BooleanQuery.add()} (used internally)
- * throws
- * {@link org.apache.lucene.search.BooleanQuery.TooManyClauses BooleanQuery.TooManyClauses}, the
- * query as it is will be returned.
- *
- * @param body the body of the document you want to find similar documents to
- * @param a the analyzer to use to parse the body
- * @param field the field you want to search on, probably something like "contents" or "body"
- * @param stop optional set of stop words to ignore
- * @return a query with all unique words in 'body'
- * @throws IOException this can't happen...
- */
- public static Query formSimilarQuery( String body,
- Analyzer a,
- String field,
- Set<?> stop)
- throws IOException
- {
- TokenStream ts = a.reusableTokenStream( field, new StringReader( body));
- CharTermAttribute termAtt = ts.addAttribute(CharTermAttribute.class);
-
- BooleanQuery tmp = new BooleanQuery();
- Set<String> already = new HashSet<String>(); // ignore dups
- while (ts.incrementToken()) {
- String word = termAtt.toString();
- // ignore opt stop words
- if ( stop != null &&
- stop.contains( word)) continue;
- // ignore dups
- if ( ! already.add( word)) continue;
- // add to query
- TermQuery tq = new TermQuery( new Term( field, word));
- try
- {
- tmp.add( tq, BooleanClause.Occur.SHOULD);
- }
- catch( BooleanQuery.TooManyClauses too)
- {
- // fail-safe, just return what we have, not the end of the world
- break;
- }
- }
- return tmp;
- }
-}
fnp / pylucene.git / blobdiff