Class SpanNearClauseFactory

SpanNearClauseFactory:

Operations:

• create for a field name and an indexreader.
• add a weighted Term - this should add a corresponding SpanTermQuery, or increase the weight of an existing one.
• add a weighted subquery SpanNearQuery
• create a clause for SpanNearQuery from the things added above.

For this, create an array of SpanQuery's from the added ones. The clause normally is a SpanOrQuery over the added subquery SpanNearQuery the SpanTermQuery's for the added Term's

When it is necessary to suppress double subqueries as much as possible: GetHashCode() and Equals() on unweighted SpanQuery are needed (possibly via GetTerms(), the terms are individually hashable). Idem SpanNearQuery: hash on the subqueries and the slop. Evt. merge SpanNearQuery's by adding the weights of the corresponding subqueries.

To be determined: Are SpanQuery weights handled correctly during search by Lucene? Should the resulting SpanOrQuery be sorted? Could other SpanQueries be added for use in this factory:

• SpanOrQuery: in principle yes, but it only has access to it's terms via getTerms(); are the corresponding weights available?
• SpanFirstQuery: treat similar to subquery SpanNearQuery. (ok?)
• SpanNotQuery: treat similar to subquery SpanNearQuery. (ok?)

Factory for SpanOrQuery