Class DirectoryReader

Expert: Constructs a DirectoryReader on the given segmentReaders.

Default termInfosIndexDivisor.

The index directory.

Set behaviour of result in case of partial cluster

Returns the directory this index resides in.

Expert: return the IndexCommit that this reader has opened.

@lucene.experimental

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.

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

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

Implement this method to support OpenIfChanged(DirectoryReader, IndexWriter, Boolean). If this reader does not support reopen from IndexWriter, throw .

Returns true if an index likely exists at the specified directory. Note that if a corrupt index exists, or if an index in the process of committing

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

If this reader was created by calling an overload of Open(Directory), then this method checks if any further commits (see Commit()) have occurred in the directory.

If instead this reader is a near real-time reader (ie, obtained by a call to Open(IndexWriter, Boolean), or by calling an overload of OpenIfChanged(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 an overload of OpenIfChanged(DirectoryReader) to get a new reader that sees the changes.

Returns all commit points that exist in the Directory. Normally, because the default is KeepOnlyLastCommitDeletionPolicy, there would be only one commit point. But if you're using a custom IndexDeletionPolicy then there could be many commits. Once you have a given commit, you can open a reader on it by calling Open(IndexCommit) There must be at least one commit in the Directory, else this method throws IndexNotFoundException. Note that if a commit is in progress while this method is running, that commit may or may not be returned.

Expert: returns an IndexReader reading the index in the given IndexCommit.

Expert: returns an IndexReader reading the index in the given IndexCommit and termInfosIndexDivisor.

Open a near real time IndexReader from the IndexWriter.

@lucene.experimental

Returns a IndexReader reading the index in the given Directory

Expert: Returns a IndexReader reading the index in the given Directory with the given termInfosIndexDivisor.

If the index has changed since the provided reader was opened, open and return a new reader; else, return null. The new reader, if not null, will be the same type of reader as the previous one, ie a near-real-time (NRT) reader will open a new NRT reader, a MultiReader will open a new MultiReader, etc.

This method is typically far less costly than opening a fully new DirectoryReader as it shares resources (for example sub-readers) with the provided DirectoryReader, when possible.

The provided reader is not disposed (you are responsible for doing so); if a new reader is returned you also must eventually dispose it. Be sure to never dispose a reader while other threads are still using it; see SearcherManager to simplify managing this.

If the IndexCommit differs from what the provided reader is searching, open and return a new reader; else, return null.

Expert: If there changes (committed or not) in the IndexWriter versus what the provided reader is searching, then open and return a new IndexReader searching both committed and uncommitted changes from the writer; else, return null (though, the current implementation never returns null).

This provides "near real-time" searching, in that changes made during an IndexWriter session can be quickly made available for searching without closing the writer nor calling Commit().

It's near real-time because there is no hard guarantee on how quickly you can get a new reader after making changes with IndexWriter. You'll have to experiment in your situation to determine if it's fast enough. As this is a new and experimental feature, please report back on your findings so we can learn, improve and iterate.

The very first time this method is called, this writer instance will make every effort to pool the readers that it opens for doing merges, applying deletes, etc. This means additional resources (RAM, file descriptors, CPU time) will be consumed.

For lower latency on reopening a reader, you should call MergedSegmentWarmer (on IndexWriterConfig) to pre-warm a newly merged segment before it's committed to the index. This is important for minimizing index-to-search delay after a large merge.

If an AddIndexes* call is running in another thread, then this reader will only search those segments from the foreign index that have been successfully copied over, so far.

NOTE: Once the writer is disposed, any outstanding readers may continue to be used. However, if you attempt to reopen any of those readers, you'll hit an .

@lucene.experimental