Package org.apache.lucene.search.spans

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 SpanTermQuerys) and inter-phrase proximity (when constructed from other SpanNearQuerys).
• A SpanOrQuery merges spans from a number of other 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);

Class Summary

Class	Description
FieldMaskingSpanQuery	Wrapper to allow SpanQuery objects participate in composite single-field SpanQueries by 'lying' about their search field.
NearSpansOrdered	A Spans that is formed from the ordered subspans of a SpanNearQuery where the subspans do not overlap and have a maximum slop between them.
NearSpansUnordered	Similar to NearSpansOrdered, but for the unordered case.
SpanFirstQuery	Matches spans near the beginning of a field.
SpanMultiTermQueryWrapper<Q extends MultiTermQuery>	Wraps any MultiTermQuery as a SpanQuery, so it can be nested within other SpanQuery classes.
SpanMultiTermQueryWrapper.SpanRewriteMethod	Abstract class that defines how the query is rewritten.
SpanMultiTermQueryWrapper.TopTermsSpanBooleanQueryRewrite	A rewrite method that first translates each term into a SpanTermQuery in a BooleanClause.Occur.SHOULD clause in a BooleanQuery, and keeps the scores as computed by the query.
SpanNearPayloadCheckQuery	Only return those matches that have a specific payload at the given position.
SpanNearQuery	Matches spans which are near one another.
SpanNotQuery	Removes matches which overlap with another SpanQuery or within a x tokens before or y tokens after another SpanQuery.
SpanOrQuery	Matches the union of its clauses.
SpanPayloadCheckQuery	Only return those matches that have a specific payload at the given position.
SpanPositionCheckQuery	Base class for filtering a SpanQuery based on the position of a match.
SpanPositionRangeQuery	Checks to see if the SpanPositionCheckQuery.getMatch() lies between a start and end position
SpanQuery	Base class for span-based queries.
Spans	Expert: an enumeration of span matches.
SpanScorer	Public for extension only.
SpanTermQuery	Matches spans containing a term.
SpanWeight	Expert-only.
TermSpans	Expert: Public for extension only