Class TermsEnum

Enumerator to seek (SeekCeil(BytesRef), SeekExact(BytesRef)) or step through (MoveNext() terms to obtain Term, frequency information (DocFreq), DocsEnum or DocsAndPositionsEnum for the current term (Docs(IBits, DocsEnum)).

Term enumerations are always ordered by Comparer. 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 MoveNext() or one of the Seek methods.

Note

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

Inheritance

object

TermsEnum

FilterAtomicReader.FilterTermsEnum

FilteredTermsEnum

MultiTermsEnum

FuzzyTermsEnum

Implements

IBytesRefEnumerator

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Namespace: Lucene.Net.Index

Assembly: Lucene.Net.dll

Syntax

public abstract class TermsEnum : IBytesRefEnumerator

Constructors

TermsEnum()

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

Declaration

protected TermsEnum()

Fields

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.

Declaration

public static readonly TermsEnum EMPTY

Field Value

Type	Description
TermsEnum

Properties

Attributes

Returns the related attributes.

Declaration

public virtual AttributeSource Attributes { get; }

Property Value

Type	Description
AttributeSource

Comparer

Return the BytesRef Comparer used to sort terms provided by the iterator. This may return null if there are no items or the iterator is not sorted. Callers may invoke this method many times, so it's best to cache a single instance & reuse it.

Declaration

public abstract IComparer<BytesRef> Comparer { get; }

Property Value

Type	Description
IComparer<BytesRef>

DocFreq

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

Declaration

public abstract int DocFreq { get; }

Property Value

Type	Description
int

See Also

END

Ord

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

Declaration

public abstract long Ord { get; }

Property Value

Type	Description
long

Term

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

Declaration

public abstract BytesRef Term { get; }

Property Value

Type	Description
BytesRef

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). 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.

Declaration

public abstract long TotalTermFreq { get; }

Property Value

Type	Description
long

Methods

Docs(IBits, DocsEnum)

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

Declaration

public DocsEnum Docs(IBits liveDocs, DocsEnum reuse)

Parameters

Type	Name	Description
IBits	liveDocs	Unset bits are documents that should not be returned
DocsEnum	reuse	Pass a prior DocsEnum for possible reuse

Returns

Type	Description
DocsEnum

Docs(IBits, DocsEnum, DocsFlags)

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.

Declaration

public abstract DocsEnum Docs(IBits liveDocs, DocsEnum reuse, DocsFlags flags)

Parameters

Type	Name	Description
IBits	liveDocs	Unset bits are documents that should not be returned
DocsEnum	reuse	Pass a prior DocsEnum for possible reuse
DocsFlags	flags	Specifies which optional per-document values you require; DocsFlags

Returns

Type	Description
DocsEnum

See Also

Docs(IBits, DocsEnum)

DocsAndPositions(IBits, DocsAndPositionsEnum)

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.

Declaration

public DocsAndPositionsEnum DocsAndPositions(IBits liveDocs, DocsAndPositionsEnum reuse)

Parameters

Type	Name	Description
IBits	liveDocs	Unset bits are documents that should not be returned
DocsAndPositionsEnum	reuse	Pass a prior DocsAndPositionsEnum for possible reuse

Returns

Type	Description
DocsAndPositionsEnum

See Also

DocsAndPositions(IBits, DocsAndPositionsEnum, DocsAndPositionsFlags)

DocsAndPositions(IBits, DocsAndPositionsEnum, DocsAndPositionsFlags)

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.

Declaration

public abstract DocsAndPositionsEnum DocsAndPositions(IBits liveDocs, DocsAndPositionsEnum reuse, DocsAndPositionsFlags flags)

Parameters

Type	Name	Description
IBits	liveDocs	Unset bits are documents that should not be returned
DocsAndPositionsEnum	reuse	Pass a prior DocsAndPositionsEnum for possible reuse
DocsAndPositionsFlags	flags	Specifies which optional per-position values you require; see DocsAndPositionsFlags.

Returns

Type	Description
DocsAndPositionsEnum

GetTermState()

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

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

Declaration

public virtual TermState GetTermState()

Returns

Type	Description
TermState

See Also

TermState

SeekExact(BytesRef, TermState)

MoveNext()

Moves to the next item in the TermsEnum.

The default implementation can and should be overridden with a more optimized version.

Declaration

public abstract bool MoveNext()

Returns

Type	Description
bool	true if the enumerator was successfully advanced to the next element; false if the enumerator has passed the end of the collection.

SeekCeil(BytesRef)

Seeks to the specified term, if it exists, or to the next (ceiling) term. Returns TermsEnum.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 END, the enum is unpositioned.

Declaration

public abstract TermsEnum.SeekStatus SeekCeil(BytesRef text)

Parameters

Type	Name	Description
BytesRef	text

Returns

Type	Description
TermsEnum.SeekStatus

SeekExact(BytesRef)

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(BytesRef) may be substantially faster than SeekCeil(BytesRef).

Declaration

public virtual bool SeekExact(BytesRef text)

Parameters

Type	Name	Description
BytesRef	text

Returns

Type	Description
bool

SeekExact(BytesRef, TermState)

Expert: Seeks a specific position by TermState previously obtained from GetTermState(). 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 state was obtained from the same TermsEnum instance.

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.

Declaration

public virtual void SeekExact(BytesRef term, TermState state)

Parameters

Type	Name	Description
BytesRef	term	the term the TermState corresponds to
TermState	state	the TermState

SeekExact(long)

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.

Declaration

public abstract void SeekExact(long ord)

Parameters

Type	Name	Description
long	ord

Implements

IBytesRefEnumerator