Class CompositeReader

Instances of this reader type can only be used to get stored fields from the underlying AtomicReaders, but it is not possible to directly retrieve postings. To do that, get the AtomicReaderContext for all sub-readers via Leaves. Alternatively, you can mimic an AtomicReader (with a serious slowdown), by wrapping composite readers with SlowCompositeReaderWrapper.

IndexReader instances for indexes on disk are usually constructed with a call to one of the static DirectoryReader.Open() methods, e.g. Open(Directory). DirectoryReader implements the CompositeReader interface, it is not possible to directly get postings.

Concrete subclasses of IndexReader are usually constructed with a call to one of the static Open() methods, e.g. Open(Directory).

For efficiency, in this API documents are often referred to via document numbers, non-negative integers which each name a unique document in the index. These document numbers are ephemeral -- they may change as documents are added to and deleted from an index. Clients should thus not rely on a given document having the same number between sessions.

NOTE: IndexReader instances are completely thread safe, meaning multiple threads can call any of its methods, concurrently. If your application requires external synchronization, you should not synchronize on the IndexReader instance; use your own (non-Lucene) objects instead.