public virtual void TestReverseDateSort()
        {
            IndexSearcher searcher = NewSearcher(Reader);

            Sort sort = new Sort(new SortField(DATE_TIME_FIELD, SortField.Type_e.STRING, true));
            Query query = new TermQuery(new Term(TEXT_FIELD, "document"));

            // Execute the search and process the search results.
            string[] actualOrder = new string[5];
            ScoreDoc[] hits = searcher.Search(query, null, 1000, sort).ScoreDocs;
            for (int i = 0; i < hits.Length; i++)
            {
                Document document = searcher.Doc(hits[i].Doc);
                string text = document.Get(TEXT_FIELD);
                actualOrder[i] = text;
            }

            // Set up the expected order (i.e. Document 5, 4, 3, 2, 1).
            string[] expectedOrder = new string[5];
            expectedOrder[0] = "Document 5";
            expectedOrder[1] = "Document 4";
            expectedOrder[2] = "Document 3";
            expectedOrder[3] = "Document 2";
            expectedOrder[4] = "Document 1";

            Assert.AreEqual(Arrays.AsList(expectedOrder), Arrays.AsList(actualOrder));
        }

        public static BooleanQuery ParseRange(string fieldName, long lowerValue, long upperValue, bool inclusive)
        {
            if (lowerValue > upperValue)
            {
                return null;
            }

            //var rangeQuery = new BooleanQuery();
            var dateQuery = new BooleanQuery();
            BooleanQuery.SetMaxClauseCount(int.MaxValue);

            for (long i = lowerValue; i < upperValue; i++)
            {
                var term = new Term(fieldName, i.ToString());
                var q = new TermQuery(term);
                dateQuery.Add(q, BooleanClause.Occur.SHOULD);
            }

            if (inclusive)
            {
                var term = new Term(fieldName, upperValue.ToString());
                var q = new TermQuery(term);
                dateQuery.Add(q, BooleanClause.Occur.SHOULD);
            }

            //if (dateQuery.GetClauses() != null || dateQuery.GetClauses().Length != 0)
            //{
            //    rangeQuery.Add(dateQuery, BooleanClause.Occur.MUST);
            //}

            return dateQuery;
        }

			public TermWeight(TermQuery enclosingInstance, Searcher searcher)
			{
				InitBlock(enclosingInstance);
				this.similarity = Enclosing_Instance.GetSimilarity(searcher);
				idfExp = similarity.IdfExplain(Enclosing_Instance.term, searcher);
				idf = idfExp.Idf;
			}

        public static LuceneResult MultiSearchBIMXchange(Dictionary<string,string> terms, int pageSize, int pageNumber)
        {
            var directory = FSDirectory.Open(new DirectoryInfo("LuceneIndex"));
            var booleanQuery = new BooleanQuery();
            foreach(var term in terms)
            {
                var query = new TermQuery(new Term(term.Key, term.Value));
                booleanQuery.Add(query,BooleanClause.Occur.MUST);
            }
            var searcher = new IndexSearcher(directory, true);

            var topDocs = searcher.Search(booleanQuery, 10);

            var docs = new List<Document>();
            var start = (pageNumber - 1) * pageSize;
            for (var i = start; i < start + pageSize && i < topDocs.TotalHits; i++)
            {
                var scoreDoc = topDocs.ScoreDocs[i];
                var docId = scoreDoc.doc;
                var doc = searcher.Doc(docId);
                docs.Add(doc);
            }

            searcher.Close();
            directory.Close();
            var result = new LuceneResult {Results = docs, TotalCount = topDocs.TotalHits};
            return result;
        }

        private IEnumerable<int> GetDocIDs(IndexReader reader, string groupByField, string group)
        {
            var query = new TermQuery(new Term(groupByField, group));
            Filter filter = new CachingWrapperFilter(new QueryWrapperFilter(query));

            return filter.GetDocIdSet(reader).AsEnumerable().ToList();
        }

 public AppQuery WithCategory(int category) {
     if (category != 0) {
         Query query = new TermQuery(new Term("Category", category.ToString()));
         AddQuery(query, BooleanClause.Occur.MUST);
     }
     return this;
 }

        private static IList<int> SearchCore(SearchFilter searchFilter, out int totalHits)
        {
            if (!Directory.Exists(LuceneCommon.IndexDirectory))
            {
                totalHits = 0;
                return new int[0];
            }

            SortField sortField = GetSortField(searchFilter);
            int numRecords = searchFilter.Skip + searchFilter.Take;

            using (var directory = new LuceneFileSystem(LuceneCommon.IndexDirectory))
            {
                var searcher = new IndexSearcher(directory, readOnly: true);
                var query = ParseQuery(searchFilter);

                var filterTerm = searchFilter.IncludePrerelease ? "IsLatest" : "IsLatestStable";
                var termQuery = new TermQuery(new Term(filterTerm, Boolean.TrueString));
                Filter filter = new QueryWrapperFilter(termQuery);
                

                var results = searcher.Search(query, filter: filter, n: numRecords, sort: new Sort(sortField));
                var keys = results.scoreDocs.Skip(searchFilter.Skip)
                                            .Select(c => ParseKey(searcher.Doc(c.doc).Get("Key")))
                                            .ToList();

                totalHits = results.totalHits;
                searcher.Close();
                return keys;
            }
        }

		public virtual void TestBasic()
		{
			// create a sort field and sort by it (reverse order)
			Query query = new TermQuery(new Term("body", "contents"));
			IndexReader r = searcher.IndexReader;
			// Just first pass query
			TopDocs hits = searcher.Search(query, 10);
			AreEqual(3, hits.TotalHits);
			AreEqual("3", r.Document(hits.ScoreDocs[0].Doc).Get("id"));
			AreEqual("1", r.Document(hits.ScoreDocs[1].Doc).Get("id"));
			AreEqual("2", r.Document(hits.ScoreDocs[2].Doc).Get("id"));
			// Now, rescore:
			Expression e = JavascriptCompiler.Compile("sqrt(_score) + ln(popularity)");
			SimpleBindings bindings = new SimpleBindings();
			bindings.Add(new SortField("popularity", SortField.Type_e.INT));
			bindings.Add(new SortField("_score", SortField.Type_e.SCORE));
			Rescorer rescorer = e.GetRescorer(bindings);
			hits = rescorer.Rescore(searcher, hits, 10);
			AreEqual(3, hits.TotalHits);
			AreEqual("2", r.Document(hits.ScoreDocs[0].Doc).Get("id"));
			AreEqual("1", r.Document(hits.ScoreDocs[1].Doc).Get("id"));
			AreEqual("3", r.Document(hits.ScoreDocs[2].Doc).Get("id"));
			string expl = rescorer.Explain(searcher, searcher.Explain(query, hits.ScoreDocs[0].Doc), hits.ScoreDocs[0].Doc).ToString();
			// Confirm the explanation breaks out the individual
			// variables:
			IsTrue(expl.Contains("= variable \"popularity\""));
			// Confirm the explanation includes first pass details:
			IsTrue(expl.Contains("= first pass score"));
			IsTrue(expl.Contains("body:contents in"));
		}

        public void TestTermSearch()
        {
            using (var dir = FSDirectory.Open(TestEnvironment.TestIndexDirectory))
            using (var indexSearcher = new IndexSearcher(dir))
            {
                var termSubjectAnt = new Term("subject", "ant");
                var termQuerySubjectAnt = new TermQuery(termSubjectAnt);
                var topDocsSubjectAnt = indexSearcher.Search(termQuerySubjectAnt, 10);

                // title=Ant in Action
                // subject=apache ant build tool junit java development
                Assert.Equal(1, topDocsSubjectAnt.TotalHits);


                var termSubjectJUnit = new Term("subject", "junit");
                var termQuerySubjectJUnit = new TermQuery(termSubjectJUnit);
                var topDocsSubjectJUnit = indexSearcher.Search(termQuerySubjectJUnit, 10);

//                ExplainResults(indexSearcher, termQuerySubjectJUnit, topDocsSubjectJUnit);

                // title=JUnit in Action, Second Edition
                // subject=junit unit testing mock objects

                // title=Ant in Action
                // subject=apache ant build tool junit java development
                Assert.Equal(2, topDocsSubjectJUnit.TotalHits); // Ants in Action, "JUnit in Action, Second Edition"
            }

        }

		public virtual void  TestAsterisk()
		{
			RAMDirectory indexStore = GetIndexStore("body", new System.String[]{"metal", "metals"});
			IndexSearcher searcher = new IndexSearcher(indexStore);
			Query query1 = new TermQuery(new Term("body", "metal"));
			Query query2 = new WildcardQuery(new Term("body", "metal*"));
			Query query3 = new WildcardQuery(new Term("body", "m*tal"));
			Query query4 = new WildcardQuery(new Term("body", "m*tal*"));
			Query query5 = new WildcardQuery(new Term("body", "m*tals"));
			
			BooleanQuery query6 = new BooleanQuery();
			query6.Add(query5, false, false);
			
			BooleanQuery query7 = new BooleanQuery();
			query7.Add(query3, false, false);
			query7.Add(query5, false, false);
			
			// Queries do not automatically lower-case search terms:
			Query query8 = new WildcardQuery(new Term("body", "M*tal*"));
			
			AssertMatches(searcher, query1, 1);
			AssertMatches(searcher, query2, 2);
			AssertMatches(searcher, query3, 1);
			AssertMatches(searcher, query4, 2);
			AssertMatches(searcher, query5, 1);
			AssertMatches(searcher, query6, 1);
			AssertMatches(searcher, query7, 2);
			AssertMatches(searcher, query8, 0);
		}

        public static Lucene.Net.Search.Query FilterQueryByClasses(IESI.ISet<System.Type> classesAndSubclasses, Lucene.Net.Search.Query luceneQuery)
        {
            // A query filter is more practical than a manual class filtering post query (esp on scrollable resultsets)
            // it also probably minimise the memory footprint
            if (classesAndSubclasses == null)
            {
                return luceneQuery;
            }

            BooleanQuery classFilter = new BooleanQuery();

            // annihilate the scoring impact of DocumentBuilder.CLASS_FIELDNAME
            classFilter.SetBoost(0);
            foreach (System.Type clazz in classesAndSubclasses)
            {
                Term t = new Term(DocumentBuilder.CLASS_FIELDNAME, TypeHelper.LuceneTypeName(clazz));
                TermQuery termQuery = new TermQuery(t);
                classFilter.Add(termQuery, BooleanClause.Occur.SHOULD);
            }

            BooleanQuery filteredQuery = new BooleanQuery();
            filteredQuery.Add(luceneQuery, BooleanClause.Occur.MUST);
            filteredQuery.Add(classFilter, BooleanClause.Occur.MUST);
            return filteredQuery;
        }

        public virtual void  TestNullOrSubScorer()
        {
            Directory dir = new MockRAMDirectory();
            IndexWriter w = new IndexWriter(dir, new WhitespaceAnalyzer(), IndexWriter.MaxFieldLength.UNLIMITED);
            Document doc = new Document();
            doc.Add(new Field("field", "a b c d", Field.Store.NO, Field.Index.ANALYZED));
            w.AddDocument(doc);

            IndexReader r = w.GetReader();
            IndexSearcher s = new IndexSearcher(r);
            BooleanQuery q = new BooleanQuery();
            q.Add(new TermQuery(new Term("field", "a")), Occur.SHOULD);

            // LUCENE-2617: make sure that a term not in the index still contributes to the score via coord factor
            float score = s.Search(q, 10).MaxScore;
            Query subQuery = new TermQuery(new Term("field", "not_in_index"));
            subQuery.Boost = 0;
            q.Add(subQuery, Occur.SHOULD);
            float score2 = s.Search(q, 10).MaxScore;
            Assert.AreEqual(score * .5, score2, 1e-6);

            // LUCENE-2617: make sure that a clause not in the index still contributes to the score via coord factor
            BooleanQuery qq = (BooleanQuery)q.Clone();
            PhraseQuery phrase = new PhraseQuery();
            phrase.Add(new Term("field", "not_in_index"));
            phrase.Add(new Term("field", "another_not_in_index"));
            phrase.Boost = 0;
            qq.Add(phrase, Occur.SHOULD);
            score2 = s.Search(qq, 10).MaxScore;
            Assert.AreEqual(score * (1.0 / 3), score2, 1e-6);

            // now test BooleanScorer2
            subQuery = new TermQuery(new Term("field", "b"));
            subQuery.Boost = 0;
            q.Add(subQuery, Occur.MUST);
            score2 = s.Search(q, 10).MaxScore;
            Assert.AreEqual(score * (2.0 / 3), score2, 1e-6);

            // PhraseQuery w/ no terms added returns a null scorer
            PhraseQuery pq = new PhraseQuery();
            q.Add(pq, Occur.SHOULD);
            Assert.AreEqual(1, s.Search(q, 10).TotalHits);
            
            // A required clause which returns null scorer should return null scorer to
            // IndexSearcher.
            q = new BooleanQuery();
            pq = new PhraseQuery();
            q.Add(new TermQuery(new Term("field", "a")), Occur.SHOULD);
            q.Add(pq, Occur.MUST);
            Assert.AreEqual(0, s.Search(q, 10).TotalHits);
            
            DisjunctionMaxQuery dmq = new DisjunctionMaxQuery(1.0f);
            dmq.Add(new TermQuery(new Term("field", "a")));
            dmq.Add(pq);
            Assert.AreEqual(1, s.Search(dmq, 10).TotalHits);
            
            r.Close();
            w.Close();
            dir.Close();
        }

        private IQueryable<Package> SearchCore(SearchFilter searchFilter, out int totalHits)
        {
            int numRecords = searchFilter.Skip + searchFilter.Take;

            var searcher = new IndexSearcher(_directory, readOnly: true);
            var query = ParseQuery(searchFilter);

            // IF searching by relevance, boost scores by download count.
            if (searchFilter.SortProperty == SortProperty.Relevance)
            {
                var downloadCountBooster = new FieldScoreQuery("DownloadCount", FieldScoreQuery.Type.INT);
                query = new CustomScoreQuery(query, downloadCountBooster);
            }

            var filterTerm = searchFilter.IncludePrerelease ? "IsLatest" : "IsLatestStable";
            var termQuery = new TermQuery(new Term(filterTerm, Boolean.TrueString));
            var filter = new QueryWrapperFilter(termQuery);
            var results = searcher.Search(query, filter: filter, n: numRecords, sort: new Sort(GetSortField(searchFilter)));
            totalHits = results.totalHits;

            if (results.totalHits == 0 || searchFilter.CountOnly)
            {
                return Enumerable.Empty<Package>().AsQueryable();
            }

            var packages = results.scoreDocs
                                  .Skip(searchFilter.Skip)
                                  .Select(sd => PackageFromDoc(searcher.Doc(sd.doc)))
                                  .ToList();
            return packages.AsQueryable();
        }

		public override Query Rewrite(IndexReader reader)
		{
			BooleanQuery query = new BooleanQuery(true);
			TermEnum enumerator = reader.Terms(prefix);
			try
			{
				System.String prefixText = prefix.Text();
				System.String prefixField = prefix.Field();
				do 
				{
					Term term = enumerator.Term();
#if !FRAMEWORK_1_1
                    if (term != null && term.Text().StartsWith(prefixText, StringComparison.Ordinal) && term.Field() == prefixField)
#else
                    if (term != null && term.Text().StartsWith(prefixText) && term.Field() == prefixField)
#endif
                    {
						TermQuery tq = new TermQuery(term); // found a match
						tq.SetBoost(GetBoost()); // set the boost
						query.Add(tq, BooleanClause.Occur.SHOULD); // add to query
						//System.out.println("added " + term);
					}
					else
					{
						break;
					}
				}
				while (enumerator.Next());
			}
			finally
			{
				enumerator.Close();
			}
			return query;
		}

        public virtual void Test()
        {
            Term allTerm = new Term(FIELD, "all");
            TermQuery termQuery = new TermQuery(allTerm);

            Weight weight = IndexSearcher.CreateNormalizedWeight(termQuery);
            Assert.IsTrue(IndexSearcher.TopReaderContext is AtomicReaderContext);
            AtomicReaderContext context = (AtomicReaderContext)IndexSearcher.TopReaderContext;
            BulkScorer ts = weight.BulkScorer(context, true, ((AtomicReader)context.Reader()).LiveDocs);
            // we have 2 documents with the term all in them, one document for all the
            // other values
            IList<TestHit> docs = new List<TestHit>();
            // must call next first

            ts.Score(new CollectorAnonymousInnerClassHelper(this, context, docs));
            Assert.IsTrue(docs.Count == 2, "docs Size: " + docs.Count + " is not: " + 2);
            TestHit doc0 = docs[0];
            TestHit doc5 = docs[1];
            // The scores should be the same
            Assert.IsTrue(doc0.Score == doc5.Score, doc0.Score + " does not equal: " + doc5.Score);
            /*
             * Score should be (based on Default Sim.: All floats are approximate tf = 1
             * numDocs = 6 docFreq(all) = 2 idf = ln(6/3) + 1 = 1.693147 idf ^ 2 =
             * 2.8667 boost = 1 lengthNorm = 1 //there is 1 term in every document coord
             * = 1 sumOfSquaredWeights = (idf * boost) ^ 2 = 1.693147 ^ 2 = 2.8667
             * queryNorm = 1 / (sumOfSquaredWeights)^0.5 = 1 /(1.693147) = 0.590
             *
             * score = 1 * 2.8667 * 1 * 1 * 0.590 = 1.69
             */
            Assert.IsTrue(doc0.Score == 1.6931472f, doc0.Score + " does not equal: " + 1.6931472f);
        }

        public virtual void TestFieldCacheRangeFilterDoubles()
        {
            IndexReader reader = SignedIndexReader;
            IndexSearcher search = NewSearcher(reader);

            int numDocs = reader.NumDocs;
            double? minIdO = Convert.ToDouble(MinId + .5);
            double? medIdO = Convert.ToDouble((float)minIdO + ((MaxId - MinId)) / 2.0);

            ScoreDoc[] result;
            Query q = new TermQuery(new Term("body", "body"));

            result = search.Search(q, FieldCacheRangeFilter.NewDoubleRange("id", minIdO, medIdO, T, T), numDocs).ScoreDocs;
            Assert.AreEqual(numDocs / 2, result.Length, "find all");
            int count = 0;
            result = search.Search(q, FieldCacheRangeFilter.NewDoubleRange("id", null, medIdO, F, T), numDocs).ScoreDocs;
            count += result.Length;
            result = search.Search(q, FieldCacheRangeFilter.NewDoubleRange("id", medIdO, null, F, F), numDocs).ScoreDocs;
            count += result.Length;
            Assert.AreEqual(numDocs, count, "sum of two concenatted ranges");
            result = search.Search(q, FieldCacheRangeFilter.NewDoubleRange("id", null, null, T, T), numDocs).ScoreDocs;
            Assert.AreEqual(numDocs, result.Length, "find all");
            result = search.Search(q, FieldCacheRangeFilter.NewDoubleRange("id", Convert.ToDouble(double.PositiveInfinity), null, F, F), numDocs).ScoreDocs;
            Assert.AreEqual(0, result.Length, "infinity special case");
            result = search.Search(q, FieldCacheRangeFilter.NewDoubleRange("id", null, Convert.ToDouble(double.NegativeInfinity), F, F), numDocs).ScoreDocs;
            Assert.AreEqual(0, result.Length, "infinity special case");
        }

        public Task<SearchResultCollection> Search(string search)
        {
            return System.Threading.Tasks.Task.Run(() =>
            {
                var src = new SearchResultCollection();
                if (string.IsNullOrWhiteSpace(search)) return src;
                try
                {

                                                       
                    var parser = new QueryParser(Version.LUCENE_30,"All", analyzer);
                    Query q = new TermQuery(new Term("All", search));
                                                           
                    using (var indexSearcher = new IndexSearcher(directory, true))
                    {
                        Query query = parser.Parse(search);
                        TopDocs result = indexSearcher.Search(query, 50);
                        foreach (ScoreDoc h in result.ScoreDocs)
                        {
                            Document doc = indexSearcher.Doc(h.Doc);
                            string id = doc.Get("id");
                            BaseContent value;
                            if (LookupTable.TryGetValue(id, out value)) src.Add(new SearchResult {Relevance = h.Score, Content = value});
                        }
                    }
                }
                catch (Exception e)
                {

                    Logger.Log("DataServer","Error lucene search",e.Message,Logger.Level.Error);
                }
                return src;
            });
        }

        //END
        //this method creates document from an ObjectToIndex
        public void BuildIndex(FileToIndex file)
        {
            using (var analyzer = new Lucene.Net.Analysis.Ru.RussianAnalyzer(Version.LUCENE_30))
            {
                using (IndexWriter idxw = new IndexWriter(_directory, analyzer, IndexWriter.MaxFieldLength.UNLIMITED))
                {
                    //check if document exists, if true deletes existing

                    var searchQuery = new TermQuery(new Term("Id", file.Id.ToString()));
                    idxw.DeleteDocuments(searchQuery);
                    //creation
                    Document doc = new Document();
                    doc.Add(new Field("Id", file.Id.ToString(), Field.Store.YES, Field.Index.NOT_ANALYZED));//аналайзер разбивает строки на слова
                    doc.Add(new Field("Title", file.Title, Field.Store.YES, Field.Index.ANALYZED));
                    doc.Add(new Field("Description", file.Description, Field.Store.YES, Field.Index.ANALYZED));
                    doc.Add(new Field("Authors", file.Authors, Field.Store.YES, Field.Index.ANALYZED));
                    doc.Add(new Field("Text", file.Text, Field.Store.YES, Field.Index.ANALYZED));
                    doc.Add(new Field("Hashtags", file.Hashtags, Field.Store.YES, Field.Index.ANALYZED));
                    doc.Add(new Field("Discipline", file.Discipline, Field.Store.YES, Field.Index.ANALYZED));
                    //write the document to the index
                    idxw.AddDocument(doc);
                    //optimize and close the writer
                    idxw.Commit();

                    idxw.Optimize();

                }
            }
        }

        private static Query ParseQuery(string searchTerm)
        {
            var fields = new Dictionary<string, float> { { "Id", 1.2f }, { "Title", 1.0f }, { "Tags", 1.0f}, { "Description", 0.8f }, { "Author", 0.6f } };
            var analyzer = new StandardAnalyzer(LuceneCommon.LuceneVersion);
            searchTerm = QueryParser.Escape(searchTerm).ToLowerInvariant();

            var queryParser = new MultiFieldQueryParser(LuceneCommon.LuceneVersion, fields.Keys.ToArray(), analyzer, fields);

            var conjuctionQuery = new BooleanQuery();
            conjuctionQuery.SetBoost(1.5f);
            var disjunctionQuery = new BooleanQuery();
            var wildCardQuery = new BooleanQuery();
            wildCardQuery.SetBoost(0.7f);
            var exactIdQuery = new TermQuery(new Term("Id-Exact", searchTerm));
            exactIdQuery.SetBoost(2.5f);

            foreach(var term in searchTerm.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries))
            {
                conjuctionQuery.Add(queryParser.Parse(term), BooleanClause.Occur.MUST);
                disjunctionQuery.Add(queryParser.Parse(term), BooleanClause.Occur.SHOULD);

                foreach (var field in fields)
                {
                    var wildCardTermQuery = new WildcardQuery(new Term(field.Key, term + "*"));
                    wildCardTermQuery.SetBoost(0.7f * field.Value);
                    wildCardQuery.Add(wildCardTermQuery, BooleanClause.Occur.SHOULD);
                }
            }

            return conjuctionQuery.Combine(new Query[] { exactIdQuery, conjuctionQuery, disjunctionQuery, wildCardQuery });
        }

		public Result Search (string term, int count, int start) {
			try {
				term = term.ToLower ();
				Term htTerm = new Term ("hottext", term);
				Query qq1 = new FuzzyQuery (htTerm);
				Query qq2 = new TermQuery (htTerm);
				qq2.Boost = 10f;
				Query qq3 = new PrefixQuery (htTerm);
				qq3.Boost = 10f;
				DisjunctionMaxQuery q1 = new DisjunctionMaxQuery (0f);
				q1.Add (qq1);
				q1.Add (qq2);
				q1.Add (qq3);
				Query q2 = new TermQuery (new Term ("text", term));
				q2.Boost = 3f;
				Query q3 = new TermQuery (new Term ("examples", term));
				q3.Boost = 3f;
				DisjunctionMaxQuery q = new DisjunctionMaxQuery (0f);

				q.Add (q1);
				q.Add (q2);
				q.Add (q3);
			
				TopDocs top = SearchInternal (q, count, start);
				Result r = new Result (term, searcher, top.ScoreDocs);
				Results.Add (r);
				return r;
			} catch (IOException) {
				Console.WriteLine ("No index in {0}", dir);
				return null;
			}
		}