org.apache.lucene.search
Class DocIdSet

java.lang.Object
  extended by org.apache.lucene.search.DocIdSet
Direct Known Subclasses:
DocIdBitSet, FieldCacheDocIdSet, FilteredDocIdSet, FixedBitSet, OpenBitSet, SortedVIntList

public abstract class DocIdSet
extends Object

A DocIdSet contains a set of doc ids. Implementing classes must only implement iterator() to provide access to the set.


Field Summary
static DocIdSet EMPTY_DOCIDSET
          An empty DocIdSet instance for easy use, e.g.
 
Constructor Summary
DocIdSet()
           
 
Method Summary
 boolean isCacheable()
          This method is a hint for CachingWrapperFilter, if this DocIdSet should be cached without copying it into a BitSet.
abstract  DocIdSetIterator iterator()
          Provides a DocIdSetIterator to access the set.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

EMPTY_DOCIDSET

public static final DocIdSet EMPTY_DOCIDSET
An empty DocIdSet instance for easy use, e.g. in Filters that hit no documents.

Constructor Detail

DocIdSet

public DocIdSet()
Method Detail

iterator

public abstract DocIdSetIterator iterator()
                                   throws IOException
Provides a DocIdSetIterator to access the set. This implementation can return null or EMPTY_DOCIDSET.iterator() if there are no docs that match.

Throws:
IOException

isCacheable

public boolean isCacheable()
This method is a hint for CachingWrapperFilter, if this DocIdSet should be cached without copying it into a BitSet. The default is to return false. If you have an own DocIdSet implementation that does its iteration very effective and fast without doing disk I/O, override this method and return true.