org.apache.lucene.index

Class BaseCompositeReader<R extends IndexReader>

java.lang.Object

org.apache.lucene.index.IndexReader

org.apache.lucene.index.CompositeReader

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

All Implemented Interfaces:

Closeable, AutoCloseable

Direct Known Subclasses:

DirectoryReader, MultiReader, ParallelCompositeReader

public abstract class BaseCompositeReader<R extends IndexReader>
extends CompositeReader

Base class for implementing CompositeReaders based on an array of sub-readers. The implementing class has to add code for correctly refcounting and closing the sub-readers.

User code will most likely use MultiReader to build a composite reader on a set of sub-readers (like several DirectoryReaders).

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.

See Also:

MultiReader

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

Nested Class Summary

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

IndexReader.CacheHelper, IndexReader.CacheKey, IndexReader.ClosedListener

Field Summary

Fields

Modifier and Type	Field and Description
protected Comparator<R>	subReadersSorter A comparator for sorting sub-readers

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	BaseCompositeReader(R[] subReaders, Comparator<R> subReadersSorter) Constructs a BaseCompositeReader on the given subReaders.

Method Summary

Modifier and Type	Method and Description
int	docFreq(Term term) Returns the number of documents containing the term.
void	document(int docID, StoredFieldVisitor visitor) Expert: visits the fields of a stored document, for custom processing/loading of each field.
int	getDocCount(String field) Returns the number of documents that have at least one term for this field.
protected List<? extends R>	getSequentialSubReaders() Expert: returns the sequential sub readers that this reader is logically composed of.
long	getSumDocFreq(String field) Returns the sum of TermsEnum.docFreq() for all terms in this field.
long	getSumTotalTermFreq(String field) Returns the sum of TermsEnum.totalTermFreq() for all terms in this field.
Fields	getTermVectors(int docID) Retrieve term vectors for this document, or null if term vectors were not indexed.
int	maxDoc() Returns one greater than the largest possible document number.
int	numDocs() Returns the number of documents in this index.
protected int	readerBase(int readerIndex) Helper method for subclasses to get the docBase of the given sub-reader index.
protected int	readerIndex(int docID) Helper method for subclasses to get the corresponding reader for a doc ID
long	totalTermFreq(Term term) Returns the total number of occurrences of term across all documents (the sum of the freq() for each doc that has this term).

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

getContext, toString

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

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

Methods inherited from class java.lang.Object

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

Field Detail

subReadersSorter

protected final Comparator<R extends IndexReader> subReadersSorter

A comparator for sorting sub-readers

Constructor Detail

BaseCompositeReader

protected BaseCompositeReader(R[] subReaders,
                              Comparator<R> subReadersSorter)
                       throws IOException

Constructs a BaseCompositeReader on the given subReaders.

Parameters:

subReaders - the wrapped sub-readers. This array is returned by getSequentialSubReaders() and used to resolve the correct subreader for docID-based methods. Please note: This array is not cloned and not protected for modification, the subclass is responsible to do this.

subReadersSorter - – a comparator for sorting sub readers. If not null, this comparator is used to sort sub readers, before using the for resolving doc IDs.

Throws:

IOException

Method Detail

getTermVectors

public final Fields getTermVectors(int docID)
                            throws IOException

Description copied from class: IndexReader

Retrieve term vectors for this document, or null if term vectors were not indexed. The returned Fields instance acts like a single-document inverted index (the docID will be 0).

Specified by:

getTermVectors in class IndexReader

Throws:

IOException

numDocs

public final int numDocs()

Description copied from class: IndexReader

Returns the number of documents in this index.

NOTE: This operation may run in O(maxDoc). Implementations that can't return this number in constant-time should cache it.

Specified by:

numDocs in class IndexReader

maxDoc

public final int maxDoc()

Description copied from class: IndexReader

Returns one greater than the largest possible document number. This may be used to, e.g., determine how big to allocate an array which will have an element for every document number in an index.

Specified by:

maxDoc in class IndexReader

document

public final void document(int docID,
                           StoredFieldVisitor visitor)
                    throws IOException

Description copied from class: IndexReader

Expert: visits the fields of a stored document, for custom processing/loading of each field. If you simply want to load all fields, use IndexReader.document(int). If you want to load a subset, use DocumentStoredFieldVisitor.

Specified by:

document in class IndexReader

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

Description copied from class: IndexReader

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.

Specified by:

totalTermFreq in class IndexReader

Throws:

IOException

getSumDocFreq

public final long getSumDocFreq(String field)
                         throws IOException

Description copied from class: IndexReader

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.

Specified by:

getSumDocFreq in class IndexReader

Throws:

IOException

See Also:

Terms.getSumDocFreq()

getDocCount

public final int getDocCount(String field)
                      throws IOException

Description copied from class: IndexReader

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.

Specified by:

getDocCount in class IndexReader

Throws:

IOException

See Also:

Terms.getDocCount()

getSumTotalTermFreq

public final long getSumTotalTermFreq(String field)
                               throws IOException

Description copied from class: IndexReader

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.

Specified by:

getSumTotalTermFreq in class IndexReader

Throws:

IOException

See Also:

Terms.getSumTotalTermFreq()

readerIndex

protected final int readerIndex(int docID)

Helper method for subclasses to get the corresponding reader for a doc ID

readerBase

protected final int readerBase(int readerIndex)

Helper method for subclasses to get the docBase of the given sub-reader index.

getSequentialSubReaders

protected final List<? extends R> getSequentialSubReaders()

Description copied from class: CompositeReader

Expert: returns the sequential sub readers that this reader is logically composed of. This method may not return null.

NOTE: In contrast to previous Lucene versions this method is no longer public, code that wants to get all LeafReaders this composite is composed of should use IndexReader.leaves().

Specified by:

getSequentialSubReaders in class CompositeReader

See Also:

IndexReader.leaves()