org.apache.lucene.index
Class AtomicReader

java.lang.Object
  org.apache.lucene.index.IndexReader
      org.apache.lucene.index.AtomicReader

All Implemented Interfaces:

Closeable

Direct Known Subclasses:

FilterAtomicReader, ParallelAtomicReader, SegmentReader, SlowCompositeReaderWrapper

public abstract class AtomicReader
extends IndexReader

AtomicReader is an abstract class, providing an interface for accessing an index. Search of an index is done entirely through this abstract interface, so that any subclass which implements it is searchable. IndexReaders implemented by this subclass do not consist of several sub-readers, they are atomic. They support retrieval of stored fields, doc values, terms, and postings.

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.

Nested Class Summary

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

IndexReader.ReaderClosedListener

Constructor Summary

protected

AtomicReader() Sole constructor.

Method Summary

int	docFreq(Term term) Returns the number of documents containing the term.
abstract DocValues	docValues(String field) Returns DocValues for this field.
abstract Fields	fields() Returns Fields for this reader.
AtomicReaderContext	getContext() Expert: Returns the root IndexReaderContext for this IndexReader's sub-reader tree.
abstract FieldInfos	getFieldInfos() Get the FieldInfos describing all fields in this reader.
abstract Bits	getLiveDocs() Returns the Bits representing live (not deleted) docs.
boolean	hasNorms(String field) Deprecated. (4.0) use getFieldInfos() and check FieldInfo.hasNorms() for the field instead.
abstract DocValues	normValues(String field) Returns DocValues for this field's normalization values.
DocsEnum	termDocsEnum(Term term) Returns DocsEnum for the specified term.
DocsAndPositionsEnum	termPositionsEnum(Term term) Returns DocsAndPositionsEnum for the specified term.
Terms	terms(String field) This may return null if the field does not exist.
long	totalTermFreq(Term term) Returns the number of documents containing the term t.

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

addReaderClosedListener, close, decRef, doClose, document, document, document, ensureOpen, equals, getCombinedCoreAndDeletesKey, getCoreCacheKey, getRefCount, getTermVector, getTermVectors, hasDeletions, hashCode, incRef, leaves, maxDoc, numDeletedDocs, numDocs, open, open, open, open, open, registerParentReader, removeReaderClosedListener, tryIncRef

Methods inherited from class java.lang.Object

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

Constructor Detail

AtomicReader

protected AtomicReader()

Sole constructor. (For invocation by subclass constructors, typically implicit.)

Method Detail

getContext

public final AtomicReaderContext getContext()

Description copied from class: IndexReader

Expert: Returns the root IndexReaderContext for this IndexReader's sub-reader tree.

Iff this reader is composed of sub readers, i.e. this reader being a composite reader, this method returns a CompositeReaderContext holding the reader's direct children as well as a view of the reader tree's atomic leaf contexts. All sub- IndexReaderContext instances referenced from this readers top-level context are private to this reader and are not shared with another context tree. For example, IndexSearcher uses this API to drive searching by one atomic leaf reader at a time. If this reader is not composed of child readers, this method returns an AtomicReaderContext.

Note: Any of the sub-CompositeReaderContext instances referenced from this top-level context do not support CompositeReaderContext.leaves(). Only the top-level context maintains the convenience leaf-view for performance reasons.

Specified by:

getContext in class IndexReader

hasNorms

@Deprecated
public final boolean hasNorms(String field)
                       throws IOException

Deprecated. (4.0) use getFieldInfos() and check FieldInfo.hasNorms() for the field instead.

Returns true if there are norms stored for this field.

Throws:

IOException

fields

public abstract Fields fields()
                       throws IOException

Returns Fields for this reader. This method may return null if the reader has no postings.

Throws:

IOException

docFreq

public final int docFreq(Term term)
                  throws IOException

Description copied from class: IndexReader

Returns the number of documents containing the term. This method returns 0 if the term or field does not exists. This method does not take into account deleted documents that have not yet been merged away.

Specified by:

docFreq in class IndexReader

Throws:

IOException

See Also:

TermsEnum.docFreq()

totalTermFreq

public final long totalTermFreq(Term term)
                         throws IOException

Returns the number of documents containing the term t. This method returns 0 if the term or field does not exists. This method does not take into account deleted documents that have not yet been merged away.

Specified by:

totalTermFreq in class IndexReader

Throws:

IOException

See Also:

TermsEnum.totalTermFreq()

terms

public final Terms terms(String field)
                  throws IOException

This may return null if the field does not exist.

Throws:

IOException

termDocsEnum

public final DocsEnum termDocsEnum(Term term)
                            throws IOException

Returns DocsEnum for the specified term. This will return null if either the field or term does not exist.

Throws:

IOException

See Also:

TermsEnum.docs(Bits, DocsEnum)

termPositionsEnum

public final DocsAndPositionsEnum termPositionsEnum(Term term)
                                             throws IOException

Returns DocsAndPositionsEnum for the specified term. This will return null if the field or term does not exist or positions weren't indexed.

Throws:

IOException

See Also:

TermsEnum.docsAndPositions(Bits, DocsAndPositionsEnum)

docValues

public abstract DocValues docValues(String field)
                             throws IOException

Returns DocValues for this field. This method may return null if the reader has no per-document values stored.

Throws:

IOException

normValues

public abstract DocValues normValues(String field)
                              throws IOException

Returns DocValues for this field's normalization values. This method may return null if the field has no norms.

Throws:

IOException

getFieldInfos

public abstract FieldInfos getFieldInfos()

Get the FieldInfos describing all fields in this reader.

WARNING: This API is experimental and might change in incompatible ways in the next release.

getLiveDocs

public abstract Bits getLiveDocs()

Returns the Bits representing live (not deleted) docs. A set bit indicates the doc ID has not been deleted. If this method returns null it means there are no deleted documents (all documents are live). The returned instance has been safely published for use by multiple threads without additional synchronization.