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Improved javadoc for span queries. 

git-svn-id: https://svn.apache.org/repos/asf/lucene/java/trunk@150276 13f79535-47bb-0310-9956-ffa450edef68
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Doug Cutting 2004-03-30 20:33:25 +00:00
parent 73779b4489
commit 45c5ec4577
1 changed files with 69 additions and 0 deletions
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src/java/org/apache/lucene/search/spans/package.html
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@ -3,5 +3,74 @@
<head></head>
<body>
The calculus of spans.
<p>A span is a <code>&lt;doc,startPosition,endPosition&gt;</code> tuple.</p>
<p>The following span query operators are implemented:
<ul>
<li>A <a href="SpanTermQuery.html">SpanTermQuery</a> matches all spans
containing a particular <a href="../../index/Term.html">Term</a>.</li>
<li> A <a href="SpanNearQuery.html">SpanNearQuery</a> matches spans
which occur near one another, and can be used to implement things like
phrase search (when constructed from <a
href="SpanTermQuery.html">SpanTermQueries</a> and inter-phrase
proximity (when constructed from other <a
href="SpanNearQuery.html">SpanNearQueries</a>.</li>
<li>A <a href="SpanOrQuery.html">SpanOrQuery</a> merges spans from a
number of other <a href="SpanQuery.html">SpanQueries</a>.</li>
<li>A <a href="SpanNotQuery.html">SpanNotQuery</a> removes spans
matching one <a href="SpanQuery.html">SpanQuery</a> which overlap
another. This can be used, e.g., to implement within-paragraph
search.</li>
<li>A <a href="SpanFirstQuery.html">SpanFirstQuery</a> matches spans
matching <code>q</code> whose end position is less than
<code>n</code>. This can be used to constrain matches to the first
part of the document.</li>
</ul>
In all cases, output spans are minimally inclusive. In other words, a
span formed by matching a span in x and y starts at the lesser of the
two starts and ends at the greater of the two ends.
</p>
<p>For example, a span query which matches "John Kerry" within ten
words of "George Bush" within the first 100 words of the document
could be constructed with:
<pre>
SpanQuery john = new SpanTermQuery(new Term("content", "john"));
SpanQuery kerry = new SpanTermQuery(new Term("content", "kerry"));
SpanQuery george = new SpanTermQuery(new Term("content", "george"));
SpanQuery bush = new SpanTermQuery(new Term("content", "bush"));
SpanQuery johnKerry =
new SpanNearQuery(new SpanQuery[] {john, kerry}, 0, true);
SpanQuery georgeBush =
new SpanNearQuery(new SpanQuery[] {george, bush}, 0, true);
SpanQuery johnKerryNearGeorgeBush =
new SpanNearQuery(new SpanQuery[] {johnKerry, georgeBush}, 10, false);
SpanQuery johnKerryNearGeorgeBushAtStart =
new SpanFirstQuery(johnKerryNearGeorgeBush, 100);
</pre>
<p>Span queries may be freely intermixed with other Lucene queries.
So, for example, the above query can be restricted to documents which
also use the word "iraq" with:
<pre>
Query query = new BooleanQuery();
query.add(johnKerryNearGeorgeBushAtStart, true, false);
query.add(new TermQuery("content", "iraq"), true, false);
</pre>
</body>
</html>