public class

ParallelReader

extends IndexReader
java.lang.Object
   ↳ org.apache.lucene.index.IndexReader
     ↳ org.apache.lucene.index.ParallelReader

Class Overview

An IndexReader which reads multiple, parallel indexes. Each index added must have the same number of documents, but typically each contains different fields. Each document contains the union of the fields of all documents with the same document number. When searching, matches for a query term are from the first index added that has the field.

This is useful, e.g., with collections that have large fields which change rarely and small fields that change more frequently. The smaller fields may be re-indexed in a new index and both indexes may be searched together.

Warning: It is up to you to make sure all indexes are created and modified the same way. For example, if you add documents to one index, you need to add the same documents in the same order to the other indexes. Failure to do so will result in undefined behavior.

Summary

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Inherited Fields
From class org.apache.lucene.index.IndexReader
Public Constructors
ParallelReader()
Construct a ParallelReader.
ParallelReader(boolean closeSubReaders)
Construct a ParallelReader.
Public Methods
void add(IndexReader reader)
Add an IndexReader.
void add(IndexReader reader, boolean ignoreStoredFields)
Add an IndexReader whose stored fields will not be returned.
synchronized Object clone()
Efficiently clones the IndexReader (sharing most internal state).
int docFreq(Term term)
Returns the number of documents containing the term t.
Document document(int n, FieldSelector fieldSelector)
Get the Document at the n th position.
Collection<String> getFieldNames(IndexReader.FieldOption fieldNames)
Get a list of unique field names that exist in this index and have the specified field option information.
void getTermFreqVector(int docNumber, String field, TermVectorMapper mapper)
Load the Term Vector into a user-defined data structure instead of relying on the parallel arrays of the TermFreqVector.
TermFreqVector getTermFreqVector(int n, String field)
Return a term frequency vector for the specified document and field.
void getTermFreqVector(int docNumber, TermVectorMapper mapper)
Map all the term vectors for all fields in a Document
TermFreqVector[] getTermFreqVectors(int n)
Return an array of term frequency vectors for the specified document.
long getVersion()
Not implemented.
boolean hasDeletions()
Returns true if any documents have been deleted
boolean hasNorms(String field)
Returns true if there are norms stored for this field.
boolean isCurrent()
Checks recursively if all subreaders are up to date.
boolean isDeleted(int n)
Returns true if document n has been deleted
boolean isOptimized()
Checks recursively if all subindexes are optimized
int maxDoc()
Returns one greater than the largest possible document number.
byte[] norms(String field)
Returns the byte-encoded normalization factor for the named field of every document.
void norms(String field, byte[] result, int offset)
Reads the byte-encoded normalization factor for the named field of every document.
int numDocs()
Returns the number of documents in this index.
synchronized IndexReader reopen()
Tries to reopen the subreaders.
TermDocs termDocs()
Returns an unpositioned TermDocs enumerator.
TermDocs termDocs(Term term)
Returns an enumeration of all the documents which contain term.
TermPositions termPositions(Term term)
Returns an enumeration of all the documents which contain term.
TermPositions termPositions()
Returns an unpositioned TermPositions enumerator.
TermEnum terms(Term term)
Returns an enumeration of all terms starting at a given term.
TermEnum terms()
Returns an enumeration of all the terms in the index.
Protected Methods
synchronized void doClose()
Implements close.
void doCommit(Map<StringString> commitUserData)
Implements commit.
void doDelete(int n)
Implements deletion of the document numbered docNum.
IndexReader doReopen(boolean doClone)
void doSetNorm(int n, String field, byte value)
Implements setNorm in subclass.
void doUndeleteAll()
Implements actual undeleteAll() in subclass.
[Expand]
Inherited Methods
From class org.apache.lucene.index.IndexReader
From class java.lang.Object
From interface java.io.Closeable

Public Constructors

public ParallelReader ()

Construct a ParallelReader.

Note that all subreaders are closed if this ParallelReader is closed.

Throws
IOException

public ParallelReader (boolean closeSubReaders)

Construct a ParallelReader.

Parameters
closeSubReaders indicates whether the subreaders should be closed when this ParallelReader is closed
Throws
IOException

Public Methods

public void add (IndexReader reader)

Add an IndexReader.

Throws
IOException if there is a low-level IO error

public void add (IndexReader reader, boolean ignoreStoredFields)

Add an IndexReader whose stored fields will not be returned. This can accelerate search when stored fields are only needed from a subset of the IndexReaders.

Throws
IllegalArgumentException if not all indexes contain the same number of documents
IllegalArgumentException if not all indexes have the same value of maxDoc()
IOException if there is a low-level IO error

public synchronized Object clone ()

Efficiently clones the IndexReader (sharing most internal state).

On cloning a reader with pending changes (deletions, norms), the original reader transfers its write lock to the cloned reader. This means only the cloned reader may make further changes to the index, and commit the changes to the index on close, but the old reader still reflects all changes made up until it was cloned.

Like reopen(), it's safe to make changes to either the original or the cloned reader: all shared mutable state obeys "copy on write" semantics to ensure the changes are not seen by other readers.

public int docFreq (Term term)

Returns the number of documents containing the term t.

Throws
IOException

public Document document (int n, FieldSelector fieldSelector)

Get the Document at the n th position. The FieldSelector may be used to determine what Fields to load and how they should be loaded. NOTE: If this Reader (more specifically, the underlying FieldsReader) is closed before the lazy Field is loaded an exception may be thrown. If you want the value of a lazy Field to be available after closing you must explicitly load it or fetch the Document again with a new loader.

NOTE: for performance reasons, this method does not check if the requested document is deleted, and therefore asking for a deleted document may yield unspecified results. Usually this is not required, however you can call isDeleted(int) with the requested document ID to verify the document is not deleted.

Parameters
n Get the document at the nth position
fieldSelector The FieldSelector to use to determine what Fields should be loaded on the Document. May be null, in which case all Fields will be loaded.
Returns
  • The stored fields of the Document at the nth position

public Collection<String> getFieldNames (IndexReader.FieldOption fieldNames)

Get a list of unique field names that exist in this index and have the specified field option information.

Parameters
fieldNames specifies which field option should be available for the returned fields
Returns
  • Collection of Strings indicating the names of the fields.

public void getTermFreqVector (int docNumber, String field, TermVectorMapper mapper)

Load the Term Vector into a user-defined data structure instead of relying on the parallel arrays of the TermFreqVector.

Parameters
docNumber The number of the document to load the vector for
field The name of the field to load
mapper The TermVectorMapper to process the vector. Must not be null
Throws
IOException

public TermFreqVector getTermFreqVector (int n, String field)

Return a term frequency vector for the specified document and field. The returned vector contains terms and frequencies for the terms in the specified field of this document, if the field had the storeTermVector flag set. If termvectors had been stored with positions or offsets, a TermPositionVector is returned.

Parameters
n document for which the term frequency vector is returned
field field for which the term frequency vector is returned.
Returns
  • term frequency vector May be null if field does not exist in the specified document or term vector was not stored.
Throws
IOException

public void getTermFreqVector (int docNumber, TermVectorMapper mapper)

Map all the term vectors for all fields in a Document

Parameters
docNumber The number of the document to load the vector for
mapper The TermVectorMapper to process the vector. Must not be null
Throws
IOException

public TermFreqVector[] getTermFreqVectors (int n)

Return an array of term frequency vectors for the specified document. The array contains a vector for each vectorized field in the document. Each vector contains terms and frequencies for all terms in a given vectorized field. If no such fields existed, the method returns null. The term vectors that are returned may either be of type TermFreqVector or of type TermPositionVector if positions or offsets have been stored.

Parameters
n document for which term frequency vectors are returned
Returns
  • array of term frequency vectors. May be null if no term vectors have been stored for the specified document.
Throws
IOException

public long getVersion ()

Not implemented.

public boolean hasDeletions ()

Returns true if any documents have been deleted

public boolean hasNorms (String field)

Returns true if there are norms stored for this field.

Throws
IOException

public boolean isCurrent ()

Checks recursively if all subreaders are up to date.

public boolean isDeleted (int n)

Returns true if document n has been deleted

public boolean isOptimized ()

Checks recursively if all subindexes are optimized

Returns
  • true if the index is optimized; false otherwise

public int maxDoc ()

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.

public byte[] norms (String field)

Returns the byte-encoded normalization factor for the named field of every document. This is used by the search code to score documents.

Throws
IOException

public void norms (String field, byte[] result, int offset)

Reads the byte-encoded normalization factor for the named field of every document. This is used by the search code to score documents.

Throws
IOException

public int numDocs ()

Returns the number of documents in this index.

public synchronized IndexReader reopen ()

Tries to reopen the subreaders.
If one or more subreaders could be re-opened (i. e. subReader.reopen() returned a new instance != subReader), then a new ParallelReader instance is returned, otherwise this instance is returned.

A re-opened instance might share one or more subreaders with the old instance. Index modification operations result in undefined behavior when performed before the old instance is closed. (see reopen()).

If subreaders are shared, then the reference count of those readers is increased to ensure that the subreaders remain open until the last referring reader is closed.

Throws
CorruptIndexException if the index is corrupt
IOException if there is a low-level IO error

public TermDocs termDocs ()

Returns an unpositioned TermDocs enumerator.

Throws
IOException

public TermDocs termDocs (Term term)

Returns an enumeration of all the documents which contain term. For each document, the document number, the frequency of the term in that document is also provided, for use in search scoring. If term is null, then all non-deleted docs are returned with freq=1. Thus, this method implements the mapping:

    Term    =>    <docNum, freq>*

The enumeration is ordered by document number. Each document number is greater than all that precede it in the enumeration.

Throws
IOException

public TermPositions termPositions (Term term)

Returns an enumeration of all the documents which contain term. For each document, in addition to the document number and frequency of the term in that document, a list of all of the ordinal positions of the term in the document is available. Thus, this method implements the mapping:

    Term    =>    <docNum, freq, <pos1, pos2, ... posfreq-1> >*

This positional information facilitates phrase and proximity searching.

The enumeration is ordered by document number. Each document number is greater than all that precede it in the enumeration.

Throws
IOException

public TermPositions termPositions ()

Returns an unpositioned TermPositions enumerator.

Throws
IOException

public TermEnum terms (Term term)

Returns an enumeration of all terms starting at a given term. If the given term does not exist, the enumeration is positioned at the first term greater than the supplied term. The enumeration is ordered by Term.compareTo(). Each term is greater than all that precede it in the enumeration.

Throws
IOException

public TermEnum terms ()

Returns an enumeration of all the terms in the index. The enumeration is ordered by Term.compareTo(). Each term is greater than all that precede it in the enumeration. Note that after calling terms(), next() must be called on the resulting enumeration before calling other methods such as term().

Throws
IOException

Protected Methods

protected synchronized void doClose ()

Implements close.

Throws
IOException

protected void doCommit (Map<StringString> commitUserData)

Implements commit.

Throws
IOException

protected void doDelete (int n)

Implements deletion of the document numbered docNum. Applications should call deleteDocument(int) or deleteDocuments(Term).

protected IndexReader doReopen (boolean doClone)

protected void doSetNorm (int n, String field, byte value)

Implements setNorm in subclass.

protected void doUndeleteAll ()

Implements actual undeleteAll() in subclass.