本文主要結合測試案例介紹了Lucene下的各種查詢語句以及它們的簡化方法.
通過本文你將了解Lucene的基本查詢語句,并可以學習所有的測試代碼已加強了解.

具體的查詢語句

在了解了SQL后, 你是否想了解一下查詢語法樹?在這里簡要介紹一些能被Lucene直接使用的查詢語句.

1.???????? TermQuery
查詢某個特定的詞,在文章開始的例子中已有介紹.常用于查詢關鍵字.

???????????? [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中的關鍵字,是需要用戶去保證唯一性的.

?TermQuery和QueryParse

只要在QueryParse的Parse方法中只有一個word,就會自動轉換成TermQuery.

2.???????? RangeQuery
用于查詢范圍,通常用于時間,還是來看例子:

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的第三個參數用于表示是否包含該起止日期.

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{}分別表示包含和不包含.

3.??? PrefixQuery

用于搜索是否包含某個特定前綴,常用于Catalog的檢索.

???????????[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");
???????? }

這里需要注意的是我們使用了QueryParser對象,而不是QueryParser類. 原因在于使用對象可以對QueryParser的一些默認屬性進行修改.比如在上面的例子中我們的category是大寫的,而QueryParser默認會把所有的含*的查詢字符串變成小寫/computer*. 這樣我們就會查不到原文中的/Computers* ,所以我們需要通過設置QueryParser的默認屬性來改變這一默認選項.即qp.SetLowercaseWildcardTerms(false)所做的工作.

4.???? BooleanQuery

用于測試滿足多個條件.

下面兩個例子用于分別測試了滿足與條件和或條件的情況.

???????? [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");

???????? }

什么時候是與什么時候又是或? 關鍵在于BooleanQuery對象的Add方法的參數.

參數一是待添加的查詢條件.

參數二Required表示這個條件必須滿足嗎? True表示必須滿足, False表示可以不滿足該條件.

參數三Prohibited表示這個條件必須拒絕嗎? True表示這么滿足這個條件的結果要排除, False表示可以滿足該條件.

這樣會有三種組合情況,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與非B 就用 A AND –B 表示, +A –B也可以.

默認的情況下QueryParser會把空格認為是或關系,就象google一樣.但是你可以通過QueryParser對象修改這一屬性.

[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
查詢短語,這里面主要有一個slop的概念, 也就是各個詞之間的位移偏差, 這個值會影響到結果的評分.如果slop為0,當然最匹配.看看下面的例子就比較容易明白了,有關slop的計算用戶就不需要理解了,不過slop太大的時候對查詢效率是有影響的,所以在實際使用中要把該值設小一點.?PhraseQuery對于短語的順序是不管的,這點在查詢時除了提高命中率外,也會對性能產生很大的影響, 利用SpanNearQuery可以對短語的順序進行控制,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進行短語查詢的時候要先設定slop的值,有兩種方式如下所示

[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",????????? //第一種方式
???????? ??????????????????????????? "field", new SimpleAnalyzer());
???????? Hits hits2 = searcher.Search(q2);
???????? Assert.AreEqual(hits2.Length(), 1);

???????? QueryParser qp = new QueryParser("field", new SimpleAnalyzer());
???????? qp.SetPhraseSlop(1);??????????????????????????????????? //第二種方式
???????? 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的分值是一樣的.
???????? [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慮使用QueryParse的時候,不允許在開頭就使用就使用通配符.
同樣處于性能考慮會將只在末尾含有*的查詢詞轉換為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
模糊查詢, 需要注意的是兩個匹配項的分值是不同的,這點和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的區別,前者~后要跟數字.

???????? [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");
???????? }