org.apache.lucene.search
Class CachingWrapperFilter

java.lang.Object
  org.apache.lucene.search.Filter
      org.apache.lucene.search.CachingWrapperFilter

public class CachingWrapperFilter
extends Filter

Wraps another Filter's result and caches it. The purpose is to allow filters to simply filter, and then wrap with this class to add caching.

Field Summary

protected static DocIdSet

EMPTY_DOCIDSET An empty DocIdSet instance

Constructor Summary

CachingWrapperFilter(Filter filter)
Wraps another filter's result and caches it.

Method Summary

protected DocIdSet	cacheImpl(DocIdSetIterator iterator, AtomicReader reader) Default cache implementation: uses WAH8DocIdSet.
protected DocIdSet	docIdSetToCache(DocIdSet docIdSet, AtomicReader reader) Provide the DocIdSet to be cached, using the DocIdSet provided by the wrapped Filter.
boolean	equals(Object o)
DocIdSet	getDocIdSet(AtomicReaderContext context, Bits acceptDocs) Creates a DocIdSet enumerating the documents that should be permitted in search results.
Filter	getFilter() Gets the contained filter.
int	hashCode()
long	sizeInBytes() Returns total byte size used by cached filters.
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

EMPTY_DOCIDSET

protected static final DocIdSet EMPTY_DOCIDSET

An empty DocIdSet instance

Constructor Detail

CachingWrapperFilter

public CachingWrapperFilter(Filter filter)

Wraps another filter's result and caches it.

Parameters:

filter - Filter to cache results of

Method Detail

getFilter

public Filter getFilter()

Gets the contained filter.

Returns:

the contained filter.

docIdSetToCache

protected DocIdSet docIdSetToCache(DocIdSet docIdSet,
                                   AtomicReader reader)
                            throws IOException

Provide the DocIdSet to be cached, using the DocIdSet provided by the wrapped Filter.

This implementation returns the given DocIdSet, if DocIdSet.isCacheable() returns true, else it calls cacheImpl(DocIdSetIterator,AtomicReader)

Note: This method returns EMPTY_DOCIDSET if the given docIdSet is null or if DocIdSet.iterator() return null. The empty instance is use as a placeholder in the cache instead of the null value.

Throws:

IOException

cacheImpl

protected DocIdSet cacheImpl(DocIdSetIterator iterator,
                             AtomicReader reader)
                      throws IOException

Default cache implementation: uses WAH8DocIdSet.

Throws:

IOException

getDocIdSet

public DocIdSet getDocIdSet(AtomicReaderContext context,
                            Bits acceptDocs)
                     throws IOException

Description copied from class: Filter

Creates a DocIdSet enumerating the documents that should be permitted in search results. NOTE: null can be returned if no documents are accepted by this Filter.

Note: This method will be called once per segment in the index during searching. The returned DocIdSet must refer to document IDs for that segment, not for the top-level reader.

Specified by:

getDocIdSet in class Filter

Parameters:

context - a AtomicReaderContext instance opened on the index currently searched on. Note, it is likely that the provided reader info does not represent the whole underlying index i.e. if the index has more than one segment the given reader only represents a single segment. The provided context is always an atomic context, so you can call AtomicReader.fields() on the context's reader, for example.

acceptDocs - Bits that represent the allowable docs to match (typically deleted docs but possibly filtering other documents)

Returns:

a DocIdSet that provides the documents which should be permitted or prohibited in search results. NOTE: null should be returned if the filter doesn't accept any documents otherwise internal optimization might not apply in the case an empty DocIdSet is returned.

Throws:

IOException

toString

public String toString()

Overrides:

toString in class Object

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

sizeInBytes

public long sizeInBytes()

Returns total byte size used by cached filters.