本文主要结合测试案例介绍了Lucene下的各种查询语句以及它们的简化方法.通过本文你将了解Lucene的基本查询语句,并通过学习相关的测试代码以加强了解.源代码下载具体的查询语句在了解了SQL后, 你是否想了解一下查询语法树?在这里简要介绍一些能被Lucene直接使用的查询语句.1. TermQuery查询某个特定的词,在文章开始的例子中已有介绍.常用于查询关键字. [Test] public void Keyword()
{
IndexSearcher searcher = new IndexSearcher(directory); Term t = new Term("isbn", "1930110995"); Query query = new TermQuery(t); Hits hits = searcher.Search(query); Assert.AreEqual(1, hits.Length(), "JUnit in Action");
}注意Lucene中的关键字,是需要用户去保证唯一性的. TermQuery和QueryParse只要在QueryParse的Parse方法中只有一个word,就会自动转换成TermQuery.2. RangeQuery用于查询范围,通常用于时间,还是来看例子:namespace dotLucene.inAction.BasicSearch{ public class RangeQueryTest : LiaTestCase
{
private Term begin, end; [SetUp] protected override void Init() { begin = new Term("pubmonth", "200004"); end = new Term("pubmonth", "200206"); base.Init();
} [Test] public void Inclusive() { RangeQuery query = new RangeQuery(begin, end, true); IndexSearcher searcher = new IndexSearcher(directory); Hits hits = searcher.Search(query); Assert.AreEqual(1, hits.Length()); } [Test] public void Exclusive() { RangeQuery query = new RangeQuery(begin, end, false); IndexSearcher searcher = new IndexSearcher(directory); Hits hits = searcher.Search(query); Assert.AreEqual(0, hits.Length()); } }}RangeQuery的第三个参数用于表示是否包含该起止日期.RangeQuery和QueryParse [Test] public void TestQueryParser() { Query query = QueryParser.Parse("pubmonth:[200004 TO 200206]", "subject", new SimpleAnalyzer()); Assert.IsTrue(query is RangeQuery); IndexSearcher searcher = new IndexSearcher(directory); Hits hits = searcher.Search(query); query = QueryParser.Parse("{200004 TO 200206}", "pubmonth", new SimpleAnalyzer()); hits = searcher.Search(query); Assert.AreEqual(0, hits.Length(), "JDwA in 200206"); } Lucene用[] 和{}分别表示包含和不包含.3. PrefixQuery用于搜索是否包含某个特定前缀,常用于Catalog的检索. [Test] public void TestPrefixQuery() { PrefixQuery query = new PrefixQuery(new Term("category", "/Computers")); IndexSearcher searcher = new IndexSearcher(directory); Hits hits = searcher.Search(query); Assert.AreEqual(2, hits.Length()); query = new PrefixQuery(new Term("category", "/Computers/JUnit")); hits = searcher.Search(query); Assert.AreEqual(1, hits.Length(), "JUnit in Action"); }PrefixQuery和QueryParse [Test] public void TestQueryParser() { QueryParser qp = new QueryParser("category", new SimpleAnalyzer()); qp.SetLowercaseWildcardTerms(false); Query query =qp.Parse("/Computers*"); Console.Out.WriteLine("query = {0}", query.ToString()); IndexSearcher searcher = new IndexSearcher(directory); Hits hits = searcher.Search(query); Assert.AreEqual(2, hits.Length()); query =qp.Parse("/Computers/JUnit*"); hits = searcher.Search(query); Assert.AreEqual(1, hits.Length(), "JUnit in Action"); }这里需要注意的是我们使用了QueryParser对象,而不是QueryParser类. 原因在于使用对象可以对QueryParser的一些默认属性进行修改.比如在上面的例子中我们的category是大写的,而QueryParser默认会把所有的含*的查询字符串变成小写/computer*. 这样我们就会查不到原文中的/Computers* ,所以我们需要通过设置QueryParser的默认属性来改变这一默认选项.即qp.SetLowercaseWildcardTerms(false)所做的工作. 4. BooleanQuery用于测试满足多个条件.下面两个例子用于分别测试了满足与条件和或条件的情况. [Test] public void And() { TermQuery searchingBooks = new TermQuery(new Term("subject", "junit")); RangeQuery currentBooks = new RangeQuery(new Term("pubmonth", "200301"), new Term("pubmonth", "200312"), true); BooleanQuery currentSearchingBooks = new BooleanQuery(); currentSearchingBooks.Add(searchingBooks, true, false); currentSearchingBooks.Add(currentBooks, true, false); IndexSearcher searcher = new IndexSearcher(directory); Hits hits = searcher.Search(currentSearchingBooks); AssertHitsIncludeTitle(hits, "JUnit in Action"); } [Test] public void Or() { TermQuery methodologyBooks = new TermQuery( new Term("category", "/Computers/JUnit")); TermQuery easternPhilosophyBooks = new TermQuery( new Term("category", "/Computers/Ant")); BooleanQuery enlightenmentBooks = new BooleanQuery(); enlightenmentBooks.Add(methodologyBooks, false, false); enlightenmentBooks.Add(easternPhilosophyBooks, false, false); IndexSearcher searcher = new IndexSearcher(directory); Hits hits = searcher.Search(enlightenmentBooks); Console.Out.WriteLine("or = " + enlightenmentBooks); AssertHitsIncludeTitle(hits, "Java Development with Ant"); AssertHitsIncludeTitle(hits, "JUnit in Action"); }什么时候是与什么时候又是或? 关键在于BooleanQuery对象的Add方法的参数.参数一是待添加的查询条件.参数二Required表示这个条件必须满足吗? True表示必须满足, False表示可以不满足该条件.参数三Prohibited表示这个条件必须拒绝吗? True表示这么满足这个条件的结果要排除, False表示可以满足该条件.这样会有三种组合情况,如下表所示:BooleanQuery和QueryParse [Test] public void TestQueryParser() { Query query = QueryParser.Parse("pubmonth:[200301 TO 200312] AND junit", "subject", new SimpleAnalyzer()); IndexSearcher searcher = new IndexSearcher(directory); Hits hits = searcher.Search(query); Assert.AreEqual(1, hits.Length()); query = QueryParser.Parse("/Computers/JUnit OR /Computers/Ant", "category", new WhitespaceAnalyzer()); hits = searcher.Search(query); Assert.AreEqual(2, hits.Length()); }注意AND和OR的大小 如果想要Ａ与非B 就用 A AND –B 表示, +A –B也可以.默认的情况下QueryParser会把空格认为是或关系,就象google一样.但是你可以通过QueryParser对象修改这一属性.[Test] public void TestQueryParserDefaultAND() { QueryParser qp = new QueryParser("subject", new SimpleAnalyzer()); qp.SetOperator(QueryParser.DEFAULT_OPERATOR_AND ); Query query = qp.Parse("pubmonth:[200301 TO 200312] junit"); IndexSearcher searcher = new IndexSearcher(directory); Hits hits = searcher.Search(query); Assert.AreEqual(1, hits.Length()); }5. PhraseQuery查询短语,这里面主要有一个slop的概念, 也就是各个词之间的位移偏差, 这个值会影响到结果的评分.如果slop为0,当然最匹配.看看下面的例子就比较容易明白了,有关slop的计算用户就不需要理解了,不过slop太大的时候对查询效率是有影响的,所以在实际使用中要把该值设小一点. PhraseQuery对于短语的顺序是不管的,这点在查询时除了提高命中率外,也会对性能产生很大的影响, 利用SpanNearQuery可以对短语的顺序进行控制,提高性能. [SetUp] protected void Init() { // set up sample document RAMDirectory directory = new RAMDirectory(); IndexWriter writer = new IndexWriter(directory, new WhitespaceAnalyzer(), true); Document doc = new Document(); doc.Add(Field.Text("field", "the quick brown fox jumped over the lazy dog")); writer.AddDocument(doc); writer.Close(); searcher = new IndexSearcher(directory); } private bool matched(String[] phrase, int slop) { PhraseQuery query = new PhraseQuery(); query.SetSlop(slop); for (int i = 0; i < phrase.Length; i++) { query.Add(new Term("field", phrase[i])); } Hits hits = searcher.Search(query); return hits.Length() > 0; } [Test] public void SlopComparison() { String[] phrase = new String[]{"quick", "fox"}; Assert.IsFalse(matched(phrase, 0), "exact phrase not found"); Assert.IsTrue(matched(phrase, 1), "close enough"); } [Test] public void Reverse() { String[] phrase = new String[] {"fox", "quick"}; Assert.IsFalse(matched(phrase, 2), "exact phrase not found"); Assert.IsTrue(matched(phrase, 3), "close enough"); } [Test] public void Multiple()- { Assert.IsFalse(matched(new String[] {"quick", "jumped", "lazy"}, 3), "not close enough"); Assert.IsTrue(matched(new String[] {"quick", "jumped", "lazy"}, 4), "just enough"); Assert.IsFalse(matched(new String[] {"lazy", "jumped", "quick"}, 7), "almost but not quite"); Assert.IsTrue(matched(new String[] {"lazy", "jumped", "quick"}, 8), "bingo"); }PhraseQuery和QueryParse利用QueryParse进行短语查询的时候要先设定slop的值,有两种方式如下所示[Test] public void TestQueryParser() { Query q1 = QueryParser.Parse(""quick fox"", "field", new SimpleAnalyzer()); Hits hits1 = searcher.Search(q1); Assert.AreEqual(hits1.Length(), 0); Query q2 = QueryParser.Parse(""quick fox"~1", //第一种方式 "field", new SimpleAnalyzer()); Hits hits2 = searcher.Search(q2); Assert.AreEqual(hits2.Length(), 1); QueryParser qp = new QueryParser("field", new SimpleAnalyzer()); qp.SetPhraseSlop(1); //第二种方式 Query q3=qp.Parse(""quick fox""); Assert.AreEqual(""quick fox"~1", q3.ToString("field"),"sloppy, implicitly"); Hits hits3 = searcher.Search(q2); Assert.AreEqual(hits3.Length(), 1); }6. WildcardQuery通配符搜索,需要注意的是child, mildew的分值是一样的. [Test] public void Wildcard() { IndexSingleFieldDocs(new Field[] { Field.Text("contents", "wild"), Field.Text("contents", "child"), Field.Text("contents", "mild"), Field.Text("contents", "mildew") }); IndexSearcher searcher = new IndexSearcher(directory); Query query = new WildcardQuery( new Term("contents", "?ild*")); Hits hits = searcher.Search(query); Assert.AreEqual(3, hits.Length(), "child no match"); Assert.AreEqual(hits.Score(0), hits.Score(1), 0.0, "score the same"); Assert.AreEqual(hits.Score(1), hits.Score(2), 0.0, "score the same"); }WildcardQuery和QueryParse需要注意的是出于性能的考虑使用QueryParse的时候,不允许在开头就使用就使用通配符.同样处于性能考虑会将只在末尾含有*的查询词转换为PrefixQuery. [Test, ExpectedException(typeof (ParseException))] public void TestQueryParserException() { Query query = QueryParser.Parse("?ild*", "contents", new WhitespaceAnalyzer()); } [Test] public void TestQueryParserTailAsterrisk() { Query query = QueryParser.Parse("mild*", "contents", new WhitespaceAnalyzer()); Assert.IsTrue(query is PrefixQuery); Assert.IsFalse(query is WildcardQuery); } [Test] public void TestQueryParser() { Query query = QueryParser.Parse("mi?d*", "contents", new WhitespaceAnalyzer()); Hits hits = searcher.Search(query); Assert.AreEqual(2, hits.Length()); }7. FuzzyQuery模糊查询, 需要注意的是两个匹配项的分值是不同的,这点和WildcardQuery是不同的 [Test] public void Fuzzy() { Query query = new FuzzyQuery(new Term("contents", "wuzza")); Hits hits = searcher.Search(query); Assert.AreEqual( 2, hits.Length(),"both close enough"); Assert.IsTrue(hits.Score(0) != hits.Score(1),"wuzzy closer than fuzzy"); Assert.AreEqual("wuzzy", hits.Doc(0).Get("contents"),"wuzza bear"); }FuzzyQuery和QueryParse注意和PhraseQuery中表示slop的区别,前者~后要跟数字. [Test] public void TestQueryParser() { Query query =QueryParser.Parse("wuzza~","contents",new SimpleAnalyzer()); Hits hits = searcher.Search(query); Assert.AreEqual( 2, hits.Length(),"both close enough"); }