src/Test/Search/TestFuzzyQuery.cs

/*
 * 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,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
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using System;

using NUnit.Framework;

using Document = Lucene.Net.Documents.Document;
using Field = Lucene.Net.Documents.Field;
using IndexWriter = Lucene.Net.Index.IndexWriter;
using Term = Lucene.Net.Index.Term;
using RAMDirectory = Lucene.Net.Store.RAMDirectory;
using WhitespaceAnalyzer = Lucene.Net.Analysis.WhitespaceAnalyzer;
using LuceneTestCase = Lucene.Net.Util.LuceneTestCase;

namespace Lucene.Net.Search
{
	
	/// <summary> Tests {@link FuzzyQuery}.
	/// 
	/// </summary>
	/// <author>  Daniel Naber
	/// </author>
	[TestFixture]
	public class TestFuzzyQuery : LuceneTestCase
	{
		[Test]
		public virtual void  TestFuzziness()
		{
			RAMDirectory directory = new RAMDirectory();
			IndexWriter writer = new IndexWriter(directory, new WhitespaceAnalyzer(), true);
			AddDoc("aaaaa", writer);
			AddDoc("aaaab", writer);
			AddDoc("aaabb", writer);
			AddDoc("aabbb", writer);
			AddDoc("abbbb", writer);
			AddDoc("bbbbb", writer);
			AddDoc("ddddd", writer);
			writer.Optimize();
			writer.Close();
			IndexSearcher searcher = new IndexSearcher(directory);
			
			FuzzyQuery query = new FuzzyQuery(new Term("field", "aaaaa"), FuzzyQuery.defaultMinSimilarity, 0);
			Hits hits = searcher.Search(query);
			Assert.AreEqual(3, hits.Length());
			
			// same with prefix
			query = new FuzzyQuery(new Term("field", "aaaaa"), FuzzyQuery.defaultMinSimilarity, 1);
			hits = searcher.Search(query);
			Assert.AreEqual(3, hits.Length());
			query = new FuzzyQuery(new Term("field", "aaaaa"), FuzzyQuery.defaultMinSimilarity, 2);
			hits = searcher.Search(query);
			Assert.AreEqual(3, hits.Length());
			query = new FuzzyQuery(new Term("field", "aaaaa"), FuzzyQuery.defaultMinSimilarity, 3);
			hits = searcher.Search(query);
			Assert.AreEqual(3, hits.Length());
			query = new FuzzyQuery(new Term("field", "aaaaa"), FuzzyQuery.defaultMinSimilarity, 4);
			hits = searcher.Search(query);
			Assert.AreEqual(2, hits.Length());
			query = new FuzzyQuery(new Term("field", "aaaaa"), FuzzyQuery.defaultMinSimilarity, 5);
			hits = searcher.Search(query);
			Assert.AreEqual(1, hits.Length());
			query = new FuzzyQuery(new Term("field", "aaaaa"), FuzzyQuery.defaultMinSimilarity, 6);
			hits = searcher.Search(query);
			Assert.AreEqual(1, hits.Length());
			
			// not similar enough:
			query = new FuzzyQuery(new Term("field", "xxxxx"), FuzzyQuery.defaultMinSimilarity, 0);
			hits = searcher.Search(query);
			Assert.AreEqual(0, hits.Length());
			query = new FuzzyQuery(new Term("field", "aaccc"), FuzzyQuery.defaultMinSimilarity, 0); // edit distance to "aaaaa" = 3
			hits = searcher.Search(query);
			Assert.AreEqual(0, hits.Length());
			
			// query identical to a word in the index:
			query = new FuzzyQuery(new Term("field", "aaaaa"), FuzzyQuery.defaultMinSimilarity, 0);
			hits = searcher.Search(query);
			Assert.AreEqual(3, hits.Length());
			Assert.AreEqual(hits.Doc(0).Get("field"), ("aaaaa"));
			// default allows for up to two edits:
			Assert.AreEqual(hits.Doc(1).Get("field"), ("aaaab"));
			Assert.AreEqual(hits.Doc(2).Get("field"), ("aaabb"));
			
			// query similar to a word in the index:
			query = new FuzzyQuery(new Term("field", "aaaac"), FuzzyQuery.defaultMinSimilarity, 0);
			hits = searcher.Search(query);
			Assert.AreEqual(3, hits.Length());
			Assert.AreEqual(hits.Doc(0).Get("field"), ("aaaaa"));
			Assert.AreEqual(hits.Doc(1).Get("field"), ("aaaab"));
			Assert.AreEqual(hits.Doc(2).Get("field"), ("aaabb"));
			
			// now with prefix
			query = new FuzzyQuery(new Term("field", "aaaac"), FuzzyQuery.defaultMinSimilarity, 1);
			hits = searcher.Search(query);
			Assert.AreEqual(3, hits.Length());
			Assert.AreEqual(hits.Doc(0).Get("field"), ("aaaaa"));
			Assert.AreEqual(hits.Doc(1).Get("field"), ("aaaab"));
			Assert.AreEqual(hits.Doc(2).Get("field"), ("aaabb"));
			query = new FuzzyQuery(new Term("field", "aaaac"), FuzzyQuery.defaultMinSimilarity, 2);
			hits = searcher.Search(query);
			Assert.AreEqual(3, hits.Length());
			Assert.AreEqual(hits.Doc(0).Get("field"), ("aaaaa"));
			Assert.AreEqual(hits.Doc(1).Get("field"), ("aaaab"));
			Assert.AreEqual(hits.Doc(2).Get("field"), ("aaabb"));
			query = new FuzzyQuery(new Term("field", "aaaac"), FuzzyQuery.defaultMinSimilarity, 3);
			hits = searcher.Search(query);
			Assert.AreEqual(3, hits.Length());
			Assert.AreEqual(hits.Doc(0).Get("field"), ("aaaaa"));
			Assert.AreEqual(hits.Doc(1).Get("field"), ("aaaab"));
			Assert.AreEqual(hits.Doc(2).Get("field"), ("aaabb"));
			query = new FuzzyQuery(new Term("field", "aaaac"), FuzzyQuery.defaultMinSimilarity, 4);
			hits = searcher.Search(query);
			Assert.AreEqual(2, hits.Length());
			Assert.AreEqual(hits.Doc(0).Get("field"), ("aaaaa"));
			Assert.AreEqual(hits.Doc(1).Get("field"), ("aaaab"));
			query = new FuzzyQuery(new Term("field", "aaaac"), FuzzyQuery.defaultMinSimilarity, 5);
			hits = searcher.Search(query);
			Assert.AreEqual(0, hits.Length());
			
			
			query = new FuzzyQuery(new Term("field", "ddddX"), FuzzyQuery.defaultMinSimilarity, 0);
			hits = searcher.Search(query);
			Assert.AreEqual(1, hits.Length());
			Assert.AreEqual(hits.Doc(0).Get("field"), ("ddddd"));
			
			// now with prefix
			query = new FuzzyQuery(new Term("field", "ddddX"), FuzzyQuery.defaultMinSimilarity, 1);
			hits = searcher.Search(query);
			Assert.AreEqual(1, hits.Length());
			Assert.AreEqual(hits.Doc(0).Get("field"), ("ddddd"));
			query = new FuzzyQuery(new Term("field", "ddddX"), FuzzyQuery.defaultMinSimilarity, 2);
			hits = searcher.Search(query);
			Assert.AreEqual(1, hits.Length());
			Assert.AreEqual(hits.Doc(0).Get("field"), ("ddddd"));
			query = new FuzzyQuery(new Term("field", "ddddX"), FuzzyQuery.defaultMinSimilarity, 3);
			hits = searcher.Search(query);
			Assert.AreEqual(1, hits.Length());
			Assert.AreEqual(hits.Doc(0).Get("field"), ("ddddd"));
			query = new FuzzyQuery(new Term("field", "ddddX"), FuzzyQuery.defaultMinSimilarity, 4);
			hits = searcher.Search(query);
			Assert.AreEqual(1, hits.Length());
			Assert.AreEqual(hits.Doc(0).Get("field"), ("ddddd"));
			query = new FuzzyQuery(new Term("field", "ddddX"), FuzzyQuery.defaultMinSimilarity, 5);
			hits = searcher.Search(query);
			Assert.AreEqual(0, hits.Length());
			
			
			// different field = no match:
			query = new FuzzyQuery(new Term("anotherfield", "ddddX"), FuzzyQuery.defaultMinSimilarity, 0);
			hits = searcher.Search(query);
			Assert.AreEqual(0, hits.Length());
			
			searcher.Close();
			directory.Close();
		}
		
		[Test]
		public virtual void  TestFuzzinessLong()
		{
			RAMDirectory directory = new RAMDirectory();
			IndexWriter writer = new IndexWriter(directory, new WhitespaceAnalyzer(), true);
			AddDoc("aaaaaaa", writer);
			AddDoc("segment", writer);
			writer.Optimize();
			writer.Close();
			IndexSearcher searcher = new IndexSearcher(directory);
			
			FuzzyQuery query;
			// not similar enough:
			query = new FuzzyQuery(new Term("field", "xxxxx"), FuzzyQuery.defaultMinSimilarity, 0);
			Hits hits = searcher.Search(query);
			Assert.AreEqual(0, hits.Length());
			// edit distance to "aaaaaaa" = 3, this matches because the string is longer than
			// in testDefaultFuzziness so a bigger difference is allowed:
			query = new FuzzyQuery(new Term("field", "aaaaccc"), FuzzyQuery.defaultMinSimilarity, 0);
			hits = searcher.Search(query);
			Assert.AreEqual(1, hits.Length());
			Assert.AreEqual(hits.Doc(0).Get("field"), ("aaaaaaa"));
			
			// now with prefix
			query = new FuzzyQuery(new Term("field", "aaaaccc"), FuzzyQuery.defaultMinSimilarity, 1);
			hits = searcher.Search(query);
			Assert.AreEqual(1, hits.Length());
			Assert.AreEqual(hits.Doc(0).Get("field"), ("aaaaaaa"));
			query = new FuzzyQuery(new Term("field", "aaaaccc"), FuzzyQuery.defaultMinSimilarity, 4);
			hits = searcher.Search(query);
			Assert.AreEqual(1, hits.Length());
			Assert.AreEqual(hits.Doc(0).Get("field"), ("aaaaaaa"));
			query = new FuzzyQuery(new Term("field", "aaaaccc"), FuzzyQuery.defaultMinSimilarity, 5);
			hits = searcher.Search(query);
			Assert.AreEqual(0, hits.Length());
			
			// no match, more than half of the characters is wrong:
			query = new FuzzyQuery(new Term("field", "aaacccc"), FuzzyQuery.defaultMinSimilarity, 0);
			hits = searcher.Search(query);
			Assert.AreEqual(0, hits.Length());
			
			// now with prefix
			query = new FuzzyQuery(new Term("field", "aaacccc"), FuzzyQuery.defaultMinSimilarity, 2);
			hits = searcher.Search(query);
			Assert.AreEqual(0, hits.Length());
			
			// "student" and "stellent" are indeed similar to "segment" by default:
			query = new FuzzyQuery(new Term("field", "student"), FuzzyQuery.defaultMinSimilarity, 0);
			hits = searcher.Search(query);
			Assert.AreEqual(1, hits.Length());
			query = new FuzzyQuery(new Term("field", "stellent"), FuzzyQuery.defaultMinSimilarity, 0);
			hits = searcher.Search(query);
			Assert.AreEqual(1, hits.Length());
			
			// now with prefix
			query = new FuzzyQuery(new Term("field", "student"), FuzzyQuery.defaultMinSimilarity, 1);
			hits = searcher.Search(query);
			Assert.AreEqual(1, hits.Length());
			query = new FuzzyQuery(new Term("field", "stellent"), FuzzyQuery.defaultMinSimilarity, 1);
			hits = searcher.Search(query);
			Assert.AreEqual(1, hits.Length());
			query = new FuzzyQuery(new Term("field", "student"), FuzzyQuery.defaultMinSimilarity, 2);
			hits = searcher.Search(query);
			Assert.AreEqual(0, hits.Length());
			query = new FuzzyQuery(new Term("field", "stellent"), FuzzyQuery.defaultMinSimilarity, 2);
			hits = searcher.Search(query);
			Assert.AreEqual(0, hits.Length());
			
			// "student" doesn't match anymore thanks to increased minimum similarity:
			query = new FuzzyQuery(new Term("field", "student"), 0.6f, 0);
			hits = searcher.Search(query);
			Assert.AreEqual(0, hits.Length());
			
			try
			{
				query = new FuzzyQuery(new Term("field", "student"), 1.1f);
				Assert.Fail("Expected IllegalArgumentException");
			}
			catch (System.ArgumentException)
			{
				// expecting exception
			}
			try
			{
				query = new FuzzyQuery(new Term("field", "student"), - 0.1f);
				Assert.Fail("Expected IllegalArgumentException");
			}
			catch (System.ArgumentException)
			{
				// expecting exception
			}
			
			searcher.Close();
			directory.Close();
		}
		
		private void  AddDoc(System.String text, IndexWriter writer)
		{
			Lucene.Net.Documents.Document doc = new Lucene.Net.Documents.Document();
			doc.Add(new Field("field", text, Field.Store.YES, Field.Index.TOKENIZED));
			writer.AddDocument(doc);
		}
	}
}