org.apache.lucene.index

Class FilteredTermsEnum

java.lang.Object

org.apache.lucene.index.TermsEnum

org.apache.lucene.index.FilteredTermsEnum

All Implemented Interfaces:

BytesRefIterator

Direct Known Subclasses:

AutomatonTermsEnum, SingleTermsEnum

public abstract class FilteredTermsEnum
extends TermsEnum

Abstract class for enumerating a subset of all terms.

Term enumerations are always ordered by BytesRef.compareTo(org.apache.lucene.util.BytesRef). Each term in the enumeration is greater than all that precede it.

Please note: Consumers of this enum cannot call seek(), it is forward only; it throws UnsupportedOperationException when a seeking method is called.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected static class	FilteredTermsEnum.AcceptStatus Return value, if term should be accepted or the iteration should END.

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

TermsEnum.SeekStatus

Field Summary

Fields

Modifier and Type	Field and Description
protected BytesRef	actualTerm Which term the enum is currently positioned to.
protected TermsEnum	tenum The delegate TermsEnum.

Fields inherited from class org.apache.lucene.index.TermsEnum

EMPTY

Constructor Summary

Constructors

Constructor and Description
FilteredTermsEnum(TermsEnum tenum) Creates a filtered TermsEnum on a terms enum.
FilteredTermsEnum(TermsEnum tenum, boolean startWithSeek) Creates a filtered TermsEnum on a terms enum.

Method Summary

Modifier and Type	Method and Description
protected abstract FilteredTermsEnum.AcceptStatus	accept(BytesRef term) Return if term is accepted, not accepted or the iteration should ended (and possibly seek).
AttributeSource	attributes() Returns the related attributes, the returned AttributeSource is shared with the delegate TermsEnum.
int	docFreq() Returns the number of documents containing the current term.
ImpactsEnum	impacts(int flags) Return a ImpactsEnum.
BytesRef	next() Increments the iteration to the next BytesRef in the iterator.
protected BytesRef	nextSeekTerm(BytesRef currentTerm) On the first call to next() or if accept(org.apache.lucene.util.BytesRef) returns FilteredTermsEnum.AcceptStatus.YES_AND_SEEK or FilteredTermsEnum.AcceptStatus.NO_AND_SEEK, this method will be called to eventually seek the underlying TermsEnum to a new position.
long	ord() Returns ordinal position for current term.
PostingsEnum	postings(PostingsEnum reuse, int flags) Get PostingsEnum for the current term, with control over whether freqs, positions, offsets or payloads are required.
TermsEnum.SeekStatus	seekCeil(BytesRef term) This enum does not support seeking!
boolean	seekExact(BytesRef term) This enum does not support seeking!
void	seekExact(BytesRef term, TermState state) This enum does not support seeking!
void	seekExact(long ord) This enum does not support seeking!
protected void	setInitialSeekTerm(BytesRef term) Use this method to set the initial BytesRef to seek before iterating.
BytesRef	term() Returns current term.
TermState	termState() Returns the filtered enums term state
long	totalTermFreq() Returns the total number of occurrences of this term across all documents (the sum of the freq() for each doc that has this term).

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

postings

Methods inherited from class java.lang.Object

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

Field Detail

actualTerm

protected BytesRef actualTerm

Which term the enum is currently positioned to.

tenum

protected final TermsEnum tenum

The delegate TermsEnum.

Constructor Detail

FilteredTermsEnum

public FilteredTermsEnum(TermsEnum tenum)

Creates a filtered TermsEnum on a terms enum.

Parameters:

tenum - the terms enumeration to filter.

FilteredTermsEnum

public FilteredTermsEnum(TermsEnum tenum,
                         boolean startWithSeek)

Creates a filtered TermsEnum on a terms enum.

Parameters:

tenum - the terms enumeration to filter.

Method Detail

accept

protected abstract FilteredTermsEnum.AcceptStatus accept(BytesRef term)
                                                  throws IOException

Return if term is accepted, not accepted or the iteration should ended (and possibly seek).

Throws:

IOException

setInitialSeekTerm

protected final void setInitialSeekTerm(BytesRef term)

Use this method to set the initial BytesRef to seek before iterating. This is a convenience method for subclasses that do not override nextSeekTerm(org.apache.lucene.util.BytesRef). If the initial seek term is null (default), the enum is empty.

You can only use this method, if you keep the default implementation of nextSeekTerm(org.apache.lucene.util.BytesRef).

nextSeekTerm

protected BytesRef nextSeekTerm(BytesRef currentTerm)
                         throws IOException

On the first call to next() or if accept(org.apache.lucene.util.BytesRef) returns FilteredTermsEnum.AcceptStatus.YES_AND_SEEK or FilteredTermsEnum.AcceptStatus.NO_AND_SEEK, this method will be called to eventually seek the underlying TermsEnum to a new position. On the first call, currentTerm will be null, later calls will provide the term the underlying enum is positioned at. This method returns per default only one time the initial seek term and then null, so no repositioning is ever done.

Override this method, if you want a more sophisticated TermsEnum, that repositions the iterator during enumeration. If this method always returns null the enum is empty.

Please note: This method should always provide a greater term than the last enumerated term, else the behaviour of this enum violates the contract for TermsEnums.

Throws:

IOException

attributes

public AttributeSource attributes()

Returns the related attributes, the returned AttributeSource is shared with the delegate TermsEnum.

Specified by:

attributes in class TermsEnum

term

public BytesRef term()
              throws IOException

Description copied from class: TermsEnum

Returns current term. Do not call this when the enum is unpositioned.

Specified by:

term in class TermsEnum

Throws:

IOException

docFreq

public int docFreq()
            throws IOException

Description copied from class: TermsEnum

Returns the number of documents containing the current term. Do not call this when the enum is unpositioned. TermsEnum.SeekStatus.END.

Specified by:

docFreq in class TermsEnum

Throws:

IOException

totalTermFreq

public long totalTermFreq()
                   throws IOException

Description copied from class: TermsEnum

Returns the total number of occurrences of this 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 TermsEnum

Throws:

IOException

seekExact

public boolean seekExact(BytesRef term)
                  throws IOException

This enum does not support seeking!

Specified by:

seekExact in class TermsEnum

Returns:

true if the term is found; return false if the enum is unpositioned.

Throws:

UnsupportedOperationException - In general, subclasses do not support seeking.

IOException

seekCeil

public TermsEnum.SeekStatus seekCeil(BytesRef term)
                              throws IOException

This enum does not support seeking!

Specified by:

seekCeil in class TermsEnum

Throws:

UnsupportedOperationException - In general, subclasses do not support seeking.

IOException

seekExact

public void seekExact(long ord)
               throws IOException

This enum does not support seeking!

Specified by:

seekExact in class TermsEnum

Throws:

UnsupportedOperationException - In general, subclasses do not support seeking.

IOException

ord

public long ord()
         throws IOException

Description copied from class: TermsEnum

Returns ordinal position for current term. This is an optional method (the codec may throw UnsupportedOperationException). Do not call this when the enum is unpositioned.

Specified by:

ord in class TermsEnum

Throws:

IOException

postings

public PostingsEnum postings(PostingsEnum reuse,
                             int flags)
                      throws IOException

Description copied from class: TermsEnum

Get PostingsEnum for the current term, with control over whether freqs, positions, offsets or payloads are required. Do not call this when the enum is unpositioned. This method will not return null.

NOTE: the returned iterator may return deleted documents, so deleted documents have to be checked on top of the PostingsEnum.

Specified by:

postings in class TermsEnum

Parameters:

reuse - pass a prior PostingsEnum for possible reuse

flags - specifies which optional per-document values you require; see PostingsEnum.FREQS

Throws:

IOException

impacts

public ImpactsEnum impacts(int flags)
                    throws IOException

Description copied from class: TermsEnum

Return a ImpactsEnum.

Specified by:

impacts in class TermsEnum

Throws:

IOException

See Also:

TermsEnum.postings(PostingsEnum, int)

seekExact

public void seekExact(BytesRef term,
                      TermState state)
               throws IOException

This enum does not support seeking!

Specified by:

seekExact in class TermsEnum

Parameters:

term - the term the TermState corresponds to

state - the TermState

Throws:

UnsupportedOperationException - In general, subclasses do not support seeking.

IOException

termState

public TermState termState()
                    throws IOException

Returns the filtered enums term state

Specified by:

termState in class TermsEnum

Throws:

IOException

See Also:

TermState, TermsEnum.seekExact(BytesRef, TermState)

next

public BytesRef next()
              throws IOException

Description copied from interface: BytesRefIterator

Increments the iteration to the next BytesRef in the iterator. Returns the resulting BytesRef or null if the end of the iterator is reached. The returned BytesRef may be re-used across calls to next. After this method returns null, do not call it again: the results are undefined.

Returns:

the next BytesRef in the iterator or null if the end of the iterator is reached.

Throws:

IOException - If there is a low-level I/O error.