org.apache.lucene.index

Class TermsEnum

java.lang.Object

org.apache.lucene.index.TermsEnum

All Implemented Interfaces:

BytesRefIterator

Direct Known Subclasses:

FilterAtomicReader.FilterTermsEnum, FilteredTermsEnum, FuzzyTermsEnum, MultiTermsEnum

public abstract class TermsEnum
extends Object
implements BytesRefIterator

Iterator to seek (seekCeil(BytesRef), seekExact(BytesRef,boolean)) or step through (BytesRefIterator.next() terms to obtain frequency information (docFreq()), DocsEnum or DocsAndPositionsEnum for the current term (docs(org.apache.lucene.util.Bits, org.apache.lucene.index.DocsEnum).

Term enumerations are always ordered by BytesRefIterator.getComparator(). Each term in the enumeration is greater than the one before it.

The TermsEnum is unpositioned when you first obtain it and you must first successfully call BytesRefIterator.next() or one of the seek methods.

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

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	TermsEnum.SeekStatus Represents returned result from seekCeil(org.apache.lucene.util.BytesRef, boolean).

Field Summary

Fields

Modifier and Type	Field and Description
static TermsEnum	EMPTY An empty TermsEnum for quickly returning an empty instance e.g.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	TermsEnum() Sole constructor.

Method Summary

Methods

Modifier and Type	Method and Description
AttributeSource	attributes() Returns the related attributes.
abstract int	docFreq() Returns the number of documents containing the current term.
DocsEnum	docs(Bits liveDocs, DocsEnum reuse) Get DocsEnum for the current term.
abstract DocsEnum	docs(Bits liveDocs, DocsEnum reuse, int flags) Get DocsEnum for the current term, with control over whether freqs are required.
DocsAndPositionsEnum	docsAndPositions(Bits liveDocs, DocsAndPositionsEnum reuse) Get DocsAndPositionsEnum for the current term.
abstract DocsAndPositionsEnum	docsAndPositions(Bits liveDocs, DocsAndPositionsEnum reuse, int flags) Get DocsAndPositionsEnum for the current term, with control over whether offsets and payloads are required.
abstract long	ord() Returns ordinal position for current term.
TermsEnum.SeekStatus	seekCeil(BytesRef text) Seeks to the specified term, if it exists, or to the next (ceiling) term.
abstract TermsEnum.SeekStatus	seekCeil(BytesRef text, boolean useCache) Expert: just like seekCeil(BytesRef) but allows you to control whether the implementation should attempt to use its term cache (if it uses one).
boolean	seekExact(BytesRef text, boolean useCache) Attempts to seek to the exact term, returning true if the term is found.
void	seekExact(BytesRef term, TermState state) Expert: Seeks a specific position by TermState previously obtained from termState().
abstract void	seekExact(long ord) Seeks to the specified term by ordinal (position) as previously returned by ord().
abstract BytesRef	term() Returns current term.
TermState	termState() Expert: Returns the TermsEnums internal state to position the TermsEnum without re-seeking the term dictionary.
abstract 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 java.lang.Object

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

Methods inherited from interface org.apache.lucene.util.BytesRefIterator

getComparator, next

Field Detail

EMPTY

public static final TermsEnum EMPTY

An empty TermsEnum for quickly returning an empty instance e.g. in MultiTermQuery

Please note: This enum should be unmodifiable, but it is currently possible to add Attributes to it. This should not be a problem, as the enum is always empty and the existence of unused Attributes does not matter.

Constructor Detail

TermsEnum

protected TermsEnum()

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

Method Detail

attributes

public AttributeSource attributes()

Returns the related attributes.

seekExact

public boolean seekExact(BytesRef text,
                boolean useCache)
                  throws IOException

Attempts to seek to the exact term, returning true if the term is found. If this returns false, the enum is unpositioned. For some codecs, seekExact may be substantially faster than seekCeil(org.apache.lucene.util.BytesRef, boolean).

Throws:

IOException

seekCeil

public abstract TermsEnum.SeekStatus seekCeil(BytesRef text,
                            boolean useCache)
                                       throws IOException

Expert: just like seekCeil(BytesRef) but allows you to control whether the implementation should attempt to use its term cache (if it uses one).

Throws:

IOException

seekCeil

public final TermsEnum.SeekStatus seekCeil(BytesRef text)
                                    throws IOException

Seeks to the specified term, if it exists, or to the next (ceiling) term. Returns SeekStatus to indicate whether exact term was found, a different term was found, or EOF was hit. The target term may be before or after the current term. If this returns SeekStatus.END, the enum is unpositioned.

Throws:

IOException

seekExact

public abstract void seekExact(long ord)
                        throws IOException

Seeks to the specified term by ordinal (position) as previously returned by ord(). The target ord may be before or after the current ord, and must be within bounds.

Throws:

IOException

seekExact

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

Expert: Seeks a specific position by TermState previously obtained from termState(). Callers should maintain the TermState to use this method. Low-level implementations may position the TermsEnum without re-seeking the term dictionary.

Seeking by TermState should only be used iff the enum the state was obtained from and the enum the state is used for seeking are obtained from the same IndexReader.

NOTE: Using this method with an incompatible TermState might leave this TermsEnum in undefined state. On a segment level TermState instances are compatible only iff the source and the target TermsEnum operate on the same field. If operating on segment level, TermState instances must not be used across segments.

NOTE: A seek by TermState might not restore the AttributeSource's state. AttributeSource states must be maintained separately if this method is used.

Parameters:

term - the term the TermState corresponds to

state - the TermState

Throws:

IOException

term

public abstract BytesRef term()
                       throws IOException

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

Throws:

IOException

ord

public abstract long ord()
                  throws IOException

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.

Throws:

IOException

docFreq

public abstract int docFreq()
                     throws IOException

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

Throws:

IOException

totalTermFreq

public abstract long totalTermFreq()
                            throws IOException

Returns the total number of occurrences of this term across all documents (the sum of the freq() for each doc that has this term). This will be -1 if the codec doesn't support this measure. Note that, like other term measures, this measure does not take deleted documents into account.

Throws:

IOException

docs

public final DocsEnum docs(Bits liveDocs,
            DocsEnum reuse)
                    throws IOException

Get DocsEnum for the current term. Do not call this when the enum is unpositioned. This method will not return null.

Parameters:

liveDocs - unset bits are documents that should not be returned

reuse - pass a prior DocsEnum for possible reuse

Throws:

IOException

docs

public abstract DocsEnum docs(Bits liveDocs,
            DocsEnum reuse,
            int flags)
                       throws IOException

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

Parameters:

liveDocs - unset bits are documents that should not be returned

reuse - pass a prior DocsEnum for possible reuse

flags - specifies which optional per-document values you require; see DocsEnum.FLAG_FREQS

Throws:

IOException

See Also:

docs(Bits, DocsEnum, int)

docsAndPositions

public final DocsAndPositionsEnum docsAndPositions(Bits liveDocs,
                                    DocsAndPositionsEnum reuse)
                                            throws IOException

Get DocsAndPositionsEnum for the current term. Do not call this when the enum is unpositioned. This method will return null if positions were not indexed.

Parameters:

liveDocs - unset bits are documents that should not be returned

reuse - pass a prior DocsAndPositionsEnum for possible reuse

Throws:

IOException

See Also:

docsAndPositions(Bits, DocsAndPositionsEnum, int)

docsAndPositions

public abstract DocsAndPositionsEnum docsAndPositions(Bits liveDocs,
                                    DocsAndPositionsEnum reuse,
                                    int flags)
                                               throws IOException

Get DocsAndPositionsEnum for the current term, with control over whether offsets and payloads are required. Some codecs may be able to optimize their implementation when offsets and/or payloads are not required. Do not call this when the enum is unpositioned. This will return null if positions were not indexed.

Parameters:

liveDocs - unset bits are documents that should not be returned

reuse - pass a prior DocsAndPositionsEnum for possible reuse

flags - specifies which optional per-position values you require; see DocsAndPositionsEnum.FLAG_OFFSETS and DocsAndPositionsEnum.FLAG_PAYLOADS.

Throws:

IOException

termState

public TermState termState()
                    throws IOException

Expert: Returns the TermsEnums internal state to position the TermsEnum without re-seeking the term dictionary.

NOTE: A seek by TermState might not capture the AttributeSource's state. Callers must maintain the AttributeSource states separately

Throws:

IOException

See Also:

TermState, seekExact(BytesRef, TermState)