public abstract class SpanFilter
extends Filter

Abstract base class providing a mechanism to restrict searches to a subset of an index and also maintains and returns position information. This is useful if you want to compare the positions from a SpanQuery with the positions of items in a filter. For instance, if you had a SpanFilter that marked all the occurrences of the word "foo" in documents, and then you entered a new SpanQuery containing bar, you could not only filter by the word foo, but you could then compare position information for post processing.