The calculus of spans.
A span is a <doc,startPosition,endPosition> tuple.
The following span query operators are implemented: * A SpanTermQuery matches all spans containing a particular Term. * A SpanNearQuery matches spans which occur near one another, and can be used to implement things like phrase search (when constructed from xref:Lucene.Net.Search.Spans.SpanTermQuerys) and inter-phrase proximity (when constructed from other xref:Lucene.Net.Search.Spans.SpanNearQuerys). * A SpanOrQuery merges spans from a number of other xref:Lucene.Net.Search.Spans.SpanQuerys. * A SpanNotQuery removes spans matching one SpanQuery which overlap (or comes near) another. This can be used, e.g., to implement within-paragraph search. * A SpanFirstQuery matches spans matching q whose end position is less than n. This can be used to constrain matches to the first part of the document. * A SpanPositionRangeQuery is a more general form of SpanFirstQuery that can constrain matches to arbitrary portions of the document. 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.
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:
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);
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:
Query query = new BooleanQuery();
query.add(johnKerryNearGeorgeBushAtStart, true, false);
query.add(new TermQuery("content", "iraq"), true, false);