DirectoryReader
DirectoryReader is an implementation of CompositeReader that can read indexes in a [ ].
DirectoryReader instances are usually constructed with a call to one of the static open() methods, e.g. .open.
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.
Inheritors
Properties
Expert: Returns the root IndexReaderContext for this IndexReader's sub-reader tree.
Optional method: Return a CacheHelper that can be used to cache based on the content of this reader. Two readers that have different data or different sets of deleted documents will be considered different.
Expert: returns the sequential sub readers that this reader is logically composed of. This method may not return null.
Functions
Implement this method to support .openIfChanged. 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. If this reader does not support reopen from a specific IndexCommit, throw [ ].
Implement this method to support .openIfChanged. If this reader does not support reopen from IndexWriter, throw [ ].
Throws AlreadyClosedException if this IndexReader or any of its child readers is closed, otherwise returns.
Returns the number of documents that have at least one term for this field. Note that, just like other term measures, this measure does not take deleted documents into account.
Expert: returns the current refCount for this reader
Returns the sum of TermsEnum.docFreq for all terms in this field. Note that, just like other term measures, this measure does not take deleted documents into account.
Returns the sum of TermsEnum.totalTermFreq for all terms in this field. Note that, just like other term measures, this measure does not take deleted documents into account.
Returns true if any documents have been deleted. Implementers should consider overriding this method if .maxDoc or .numDocs are not constant-time operations.
Expert: increments the refCount of this IndexReader instance. RefCounts are used to determine when a reader can be closed safely, i.e. as soon as there are no more references. Be sure to always call a corresponding .decRef, in a finally clause; otherwise the reader may never be closed. Note that .close simply calls decRef(), which means that the IndexReader will not really be closed until .decRef has been called for all outstanding references.
Returns the reader's leaves, or itself if this reader is atomic. This is a convenience method calling this.getContext().leaves().
Returns the number of deleted documents.
Expert: This method is called by IndexReaders which wrap other readers (e.g. [ ] or FilterLeafReader) to register the parent at the child (this reader) on construction of the parent. When this reader is closed, it will mark all registered parents as closed, too. The references to parent readers are weak only, so they can be GCed once they are no longer in use.
Returns a StoredFields reader for the stored fields of this index.
Returns a TermVectors reader for the term vectors of this index.
Returns the total number of occurrences of term across all documents (the sum of the freq() for each doc that has this term). Note that, like other term measures, this measure does not take deleted documents into account.
Expert: increments the refCount of this IndexReader instance only if the IndexReader has not been closed yet and returns true iff the refCount was successfully incremented, otherwise false. If this method returns false the reader is either already closed or is currently being closed. Either way this reader instance shouldn't be used by an application unless true is returned.