Package org.apache.lucene.index

Class FilterDirectoryReader

java.lang.Object

org.apache.lucene.index.IndexReader

org.apache.lucene.index.CompositeReader

org.apache.lucene.index.BaseCompositeReader<LeafReader>

org.apache.lucene.index.DirectoryReader

org.apache.lucene.index.FilterDirectoryReader

All Implemented Interfaces:

Closeable, AutoCloseable

Direct Known Subclasses:

ExitableDirectoryReader, SoftDeletesDirectoryReaderWrapper

public abstract class FilterDirectoryReader
extends DirectoryReader

A FilterDirectoryReader wraps another DirectoryReader, allowing implementations to transform or extend it.

Subclasses should implement doWrapDirectoryReader to return an instance of the subclass.

If the subclass wants to wrap the DirectoryReader's subreaders, it should also implement a SubReaderWrapper subclass, and pass an instance to its super constructor.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected static class	FilterDirectoryReader.DelegatingCacheHelper	A DelegatingCacheHelper is a CacheHelper specialization for implementing long-lived caching behaviour for FilterDirectoryReader subclasses.
static class	FilterDirectoryReader.SubReaderWrapper	Factory class passed to FilterDirectoryReader constructor that allows subclasses to wrap the filtered DirectoryReader's subreaders.

Nested classes/interfaces inherited from class org.apache.lucene.index.IndexReader

IndexReader.CacheHelper, IndexReader.CacheKey, IndexReader.ClosedListener

Field Summary

Fields

Modifier and Type	Field	Description
protected final DirectoryReader	in	The filtered DirectoryReader

Fields inherited from class org.apache.lucene.index.DirectoryReader

directory

Fields inherited from class org.apache.lucene.index.BaseCompositeReader

subReadersSorter

Constructor Summary

Constructors

Constructor	Description
FilterDirectoryReader(DirectoryReader in, FilterDirectoryReader.SubReaderWrapper wrapper)	Create a new FilterDirectoryReader that filters a passed in DirectoryReader, using the supplied SubReaderWrapper to wrap its subreader.

Method Summary

Modifier and Type	Method	Description
protected void	doClose()	Implements close.
protected final DirectoryReader	doOpenIfChanged()	Implement this method to support DirectoryReader.openIfChanged(DirectoryReader).
protected final DirectoryReader	doOpenIfChanged(IndexCommit commit)	Implement this method to support DirectoryReader.openIfChanged(DirectoryReader,IndexCommit).
protected final DirectoryReader	doOpenIfChanged(IndexWriter writer, boolean applyAllDeletes)	Implement this method to support DirectoryReader.openIfChanged(DirectoryReader,IndexWriter,boolean).
protected abstract DirectoryReader	doWrapDirectoryReader(DirectoryReader in)	Called by the doOpenIfChanged() methods to return a new wrapped DirectoryReader.
DirectoryReader	getDelegate()	Returns the wrapped DirectoryReader.
IndexCommit	getIndexCommit()	Expert: return the IndexCommit that this reader has opened.
long	getVersion()	Version number when this IndexReader was opened.
boolean	isCurrent()	Check whether any new changes have occurred to the index since this reader was opened.
static DirectoryReader	unwrap(DirectoryReader reader)	Get the wrapped instance by reader as long as this reader is an instance of FilterDirectoryReader.

Methods inherited from class org.apache.lucene.index.DirectoryReader

directory, indexExists, listCommits, open, open, open, open, open, open, openIfChanged, openIfChanged, openIfChanged, openIfChanged

Methods inherited from class org.apache.lucene.index.BaseCompositeReader

docFreq, document, getDocCount, getSequentialSubReaders, getSumDocFreq, getSumTotalTermFreq, getTermVectors, maxDoc, numDocs, readerBase, readerIndex, totalTermFreq

Methods inherited from class org.apache.lucene.index.CompositeReader

getContext, toString

Methods inherited from class org.apache.lucene.index.IndexReader

close, decRef, document, document, ensureOpen, equals, getReaderCacheHelper, getRefCount, getTermVector, hasDeletions, hashCode, incRef, leaves, notifyReaderClosedListeners, numDeletedDocs, registerParentReader, tryIncRef

Methods inherited from class java.lang.Object

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

Field Details

in

protected final DirectoryReader in

The filtered DirectoryReader

Constructor Details

FilterDirectoryReader

public FilterDirectoryReader(DirectoryReader in,
 FilterDirectoryReader.SubReaderWrapper wrapper)
                      throws IOException

Create a new FilterDirectoryReader that filters a passed in DirectoryReader, using the supplied SubReaderWrapper to wrap its subreader.

Parameters:

in - the DirectoryReader to filter

wrapper - the SubReaderWrapper to use to wrap subreaders

Throws:

IOException

Method Details

unwrap

public static DirectoryReader unwrap(DirectoryReader reader)

Get the wrapped instance by reader as long as this reader is an instance of FilterDirectoryReader.

doWrapDirectoryReader

protected abstract DirectoryReader doWrapDirectoryReader(DirectoryReader in)
                                                  throws IOException

Called by the doOpenIfChanged() methods to return a new wrapped DirectoryReader.

Implementations should just return an instantiation of themselves, wrapping the passed in DirectoryReader.

Parameters:

in - the DirectoryReader to wrap

Returns:

the wrapped DirectoryReader

Throws:

IOException

doOpenIfChanged

protected final DirectoryReader doOpenIfChanged()
                                         throws IOException

Description copied from class: DirectoryReader

Implement this method to support DirectoryReader.openIfChanged(DirectoryReader). If this reader does not support reopen, return null, so client code is happy. This should be consistent with DirectoryReader.isCurrent() (should always return true) if reopen is not supported.

Specified by:

doOpenIfChanged in class DirectoryReader

Returns:

null if there are no changes; else, a new DirectoryReader instance.

Throws:

IOException - if there is a low-level IO error

doOpenIfChanged

protected final DirectoryReader doOpenIfChanged(IndexCommit commit)
                                         throws IOException

Description copied from class: DirectoryReader

Implement this method to support DirectoryReader.openIfChanged(DirectoryReader,IndexCommit). If this reader does not support reopen from a specific IndexCommit, throw UnsupportedOperationException.

Specified by:

doOpenIfChanged in class DirectoryReader

Returns:

null if there are no changes; else, a new DirectoryReader instance.

Throws:

IOException - if there is a low-level IO error

doOpenIfChanged

protected final DirectoryReader doOpenIfChanged(IndexWriter writer,
 boolean applyAllDeletes)
                                         throws IOException

Description copied from class: DirectoryReader

Implement this method to support DirectoryReader.openIfChanged(DirectoryReader,IndexWriter,boolean). If this reader does not support reopen from IndexWriter, throw UnsupportedOperationException.

Specified by:

doOpenIfChanged in class DirectoryReader

Returns:

null if there are no changes; else, a new DirectoryReader instance.

Throws:

IOException - if there is a low-level IO error

getVersion

public long getVersion()

Description copied from class: DirectoryReader

Version number when this IndexReader was opened.

This method returns the version recorded in the commit that the reader opened. This version is advanced every time a change is made with IndexWriter.

Specified by:

getVersion in class DirectoryReader

isCurrent

public boolean isCurrent()
                  throws IOException

Description copied from class: DirectoryReader

Check whether any new changes have occurred to the index since this reader was opened.

If this reader was created by calling DirectoryReader.open(org.apache.lucene.store.Directory), then this method checks if any further commits (see IndexWriter.commit()) have occurred in the directory.

If instead this reader is a near real-time reader (ie, obtained by a call to DirectoryReader.open(IndexWriter), or by calling DirectoryReader.openIfChanged(org.apache.lucene.index.DirectoryReader) on a near real-time reader), then this method checks if either a new commit has occurred, or any new uncommitted changes have taken place via the writer. Note that even if the writer has only performed merging, this method will still return false.

In any event, if this returns false, you should call DirectoryReader.openIfChanged(org.apache.lucene.index.DirectoryReader) to get a new reader that sees the changes.

Specified by:

isCurrent in class DirectoryReader

Throws:

IOException - if there is a low-level IO error

getIndexCommit

public IndexCommit getIndexCommit()
                           throws IOException

Description copied from class: DirectoryReader

Expert: return the IndexCommit that this reader has opened.

Specified by:

getIndexCommit in class DirectoryReader

Throws:

IOException

doClose

protected void doClose()
                throws IOException

Description copied from class: IndexReader

Implements close.

Specified by:

doClose in class IndexReader

Throws:

IOException

getDelegate

public DirectoryReader getDelegate()

Returns the wrapped DirectoryReader.