## Package org.apache.lucene.search.spans

The calculus of spans.

See:
Description

Class Summary
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.
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

Enum Summary
SpanPositionCheckQuery.AcceptStatus: Return value for `SpanPositionCheckQuery.acceptPosition(Spans)`.

## Package org.apache.lucene.search.spans Description

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 `SpanTermQuery`s) and inter-phrase proximity (when constructed from other `SpanNearQuery`s).
- A `SpanOrQuery` merges spans from a number of other `SpanQuery`s.
- A `SpanNotQuery` removes spans matching one `SpanQuery` which overlap 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);

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