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<!doctype html public "-//w3c//dtd html 4.0 transitional//en"><html><head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <meta name="Author" content="Doug Cutting"> <meta content="Grant Ingersoll" name="Author"></head><body><h2>Table Of Contents</h2><p> <ol> <li><a href="#search">Search Basics</a></li> <li><a href="#query">The Query Classes</a></li> <li><a href="#scoring">Changing the Scoring</a></li> </ol></p><a name="search"></a><h2>Search</h2><p>Search over indices.Applications usually call {@linkLucene.Net.Search.Searcher#search(Query)} or {@linkLucene.Net.Search.Searcher#search(Query,Filter)}. <!-- FILL IN MORE HERE --> </p><a name="query"></a><h2>Query Classes</h2><h4> <a href="TermQuery.html">TermQuery</a></h4><p>Of the various implementations of <a href="Query.html">Query</a>, the <a href="TermQuery.html">TermQuery</a> is the easiest to understand and the most often used in applications. A <a href="TermQuery.html">TermQuery</a> matches all the documents that contain the specified <a href="../index/Term.html">Term</a>, which is a word that occurs in a certain <a href="../document/Field.html">Field</a>. Thus, a <a href="TermQuery.html">TermQuery</a> identifies and scores all <a href="../document/Document.html">Document</a>s that have a <a href="../document/Field.html">Field</a> with the specified string in it. Constructing a <a href="TermQuery.html">TermQuery</a> is as simple as: <pre> TermQuery tq = new TermQuery(new Term("fieldName", "term"); </pre>In this example, the <a href="Query.html">Query</a> identifies all <a href="../document/Document.html">Document</a>s that have the <a href="../document/Field.html">Field</a> named <tt>"fieldName"</tt> and contain the word <tt>"term"</tt>.</p><h4> <a href="BooleanQuery.html">BooleanQuery</a></h4><p>Things start to get interesting when one combines multiple <a href="TermQuery.html">TermQuery</a> instances into a <a href="BooleanQuery.html">BooleanQuery</a>. A <a href="BooleanQuery.html">BooleanQuery</a> contains multiple <a href="BooleanClause.html">BooleanClause</a>s, where each clause contains a sub-query (<a href="Query.html">Query</a> instance) and an operator (from <a href="BooleanClause.Occur.html">BooleanClause.Occur</a>) describing how that sub-query is combined with the other clauses: <ol> <li><p>SHOULD -- Use this operator when a clause can occur in the result set, but is not required. If a query is made up of all SHOULD clauses, then every document in the result set matches at least one of these clauses.</p></li> <li><p>MUST -- Use this operator when a clause is required to occur in the result set. Every document in the result set will match all such clauses.</p></li> <li><p>MUST NOT -- Use this operator when a clause must not occur in the result set. No document in the result set will match any such clauses.</p></li> </ol> Boolean queries are constructed by adding two or more <a href="BooleanClause.html">BooleanClause</a> instances. If too many clauses are added, a <a href="BooleanQuery.TooManyClauses.html">TooManyClauses</a> exception will be thrown during searching. This most often occurs when a <a href="Query.html">Query</a> is rewritten into a <a href="BooleanQuery.html">BooleanQuery</a> with many <a href="TermQuery.html">TermQuery</a> clauses, for example by <a href="WildcardQuery.html">WildcardQuery</a>. The default setting for the maximum number of clauses 1024, but this can be changed via the static method <a href="BooleanQuery.html#setMaxClauseCount(int)">setMaxClauseCount</a> in <a href="BooleanQuery.html">BooleanQuery</a>.</p><h4>Phrases</h4><p>Another common search is to find documents containing certain phrases. This is handled in two different ways. <ol> <li> <p><a href="PhraseQuery.html">PhraseQuery</a> -- Matches a sequence of <a href="../index/Term.html">Terms</a>. <a href="PhraseQuery.html">PhraseQuery</a> uses a slop factor to determine how many positions may occur between any two terms in the phrase and still be considered a match.</p> </li> <li> <p><a href="spans/SpanNearQuery.html">SpanNearQuery</a> -- Matches a sequence of other <a href="spans/SpanQuery.html">SpanQuery</a> instances. <a href="spans/SpanNearQuery.html">SpanNearQuery</a> allows for much more complicated phrase queries since it is constructed from other to <a href="spans/SpanQuery.html">SpanQuery</a> instances, instead of only <a href="TermQuery.html">TermQuery</a> instances.</p> </li> </ol></p><h4> <a href="RangeQuery.html">RangeQuery</a></h4><p>The <a href="RangeQuery.html">RangeQuery</a> matches all documents that occur in the exclusive range of a lower <a href="../index/Term.html">Term</a> and an upper <a href="../index/Term.html">Term</a>. For example, one could find all documents that have terms beginning with the letters <tt>a</tt> through <tt>c</tt>. This type of <a href="Query.html">Query</a> is frequently used to find documents that occur in a specific date range.</p><h4> <a href="PrefixQuery.html">PrefixQuery</a>, <a href="WildcardQuery.html">WildcardQuery</a></h4><p>While the <a href="PrefixQuery.html">PrefixQuery</a> has a different implementation, it is essentially a special case of the <a href="WildcardQuery.html">WildcardQuery</a>. The <a href="PrefixQuery.html">PrefixQuery</a> allows an application to identify all documents with terms that begin with a certain string. The <a href="WildcardQuery.html">WildcardQuery</a> generalizes this by allowing for the use of <tt>*</tt> (matches 0 or more characters) and <tt>?</tt> (matches exactly one character) wildcards. Note that the <a href="WildcardQuery.html">WildcardQuery</a> can be quite slow. Also note that <a href="WildcardQuery.html">WildcardQuery</a> should not start with <tt>*</tt> and <tt>?</tt>, as these are extremely slow. For tricks on how to search using a wildcard at the beginning of a term, see <a href="http://www.gossamer-threads.com/lists/lucene/java-user/13373#13373"> Starts With x and Ends With x Queries</a> from the Lucene users's mailing list.</p><h4> <a href="FuzzyQuery.html">FuzzyQuery</a></h4><p>A <a href="FuzzyQuery.html">FuzzyQuery</a> matches documents that contain terms similar to the specified term. Similarity is determined using <a href="http://en.wikipedia.org/wiki/Levenshtein">Levenshtein (edit) distance</a>. This type of query can be useful when accounting for spelling variations in the collection.</p><a name="changingSimilarity"></a><h2>Changing Similarity</h2><p>Chances are <a href="DefaultSimilarity.html">DefaultSimilarity</a> is sufficient for all your searching needs. However, in some applications it may be necessary to customize your <a href="Similarity.html">Similarity</a> implementation. For instance, some⌨️ 快捷键说明
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