Class TermsEnum
- All Implemented Interfaces:
BytesRefIterator
- Direct Known Subclasses:
BaseTermsEnum,FilteredTermsEnum,FilterLeafReader.FilterTermsEnum
seekCeil(BytesRef), seekExact(BytesRef)) or step through
(BytesRefIterator.next() terms to obtain frequency information (docFreq()), PostingsEnum or
PostingsEnum for the current term (postings(org.apache.lucene.index.PostingsEnum).
Term enumerations are always ordered by BytesRef.compareTo, which is Unicode sort order if the terms are UTF-8 bytes. 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.
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionstatic enumRepresents returned result fromseekCeil(org.apache.lucene.util.BytesRef). -
Field Summary
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Constructor Summary
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Method Summary
Modifier and TypeMethodDescriptionabstract AttributeSourceReturns the related attributes.abstract intdocFreq()Returns the number of documents containing the current term.abstract ImpactsEnumimpacts(int flags) Return aImpactsEnum.abstract longord()Returns ordinal position for current term.final PostingsEnumpostings(PostingsEnum reuse) GetPostingsEnumfor the current term.abstract PostingsEnumpostings(PostingsEnum reuse, int flags) GetPostingsEnumfor the current term, with control over whether freqs, positions, offsets or payloads are required.abstract IOBooleanSupplierprepareSeekExact(BytesRef text) Two-phaseseekExact(org.apache.lucene.util.BytesRef).abstract TermsEnum.SeekStatusSeeks to the specified term, if it exists, or to the next (ceiling) term.abstract voidseekExact(long ord) Seeks to the specified term by ordinal (position) as previously returned byord().abstract booleanAttempts to seek to the exact term, returning true if the term is found.abstract voidExpert: Seeks a specific position byTermStatepreviously obtained fromtermState().abstract BytesRefterm()Returns current term.abstract TermStateExpert: Returns the TermsEnums internal state to position the TermsEnum without re-seeking the term dictionary.abstract longReturns 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, waitMethods inherited from interface org.apache.lucene.util.BytesRefIterator
next
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Field Details
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EMPTY
An empty TermsEnum for quickly returning an empty instance e.g. inMultiTermQueryPlease 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.
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Constructor Details
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TermsEnum
protected TermsEnum()Sole constructor. (For invocation by subclass constructors, typically implicit.)
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Method Details
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attributes
Returns the related attributes. -
seekExact
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 thanseekCeil(org.apache.lucene.util.BytesRef).- Returns:
- true if the term is found; return false if the enum is unpositioned.
- Throws:
IOException
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prepareSeekExact
Two-phaseseekExact(org.apache.lucene.util.BytesRef). The first phase typically callsIndexInput.prefetch(long, long)on the right range of bytes under the hood, while the second phaseIOBooleanSupplier.get()actually seeks the term within these bytes. This can be used to parallelize I/O across multiple terms by callingprepareSeekExact(org.apache.lucene.util.BytesRef)on multiple terms enums before callingIOBooleanSupplier.get().NOTE: It is illegal to call other methods on this
TermsEnumafter calling this method untilIOBooleanSupplier.get()is called.NOTE: This may return
nullif thisTermsEnumcan identify that the term may not exist without performing any I/O.NOTE: The returned
IOBooleanSuppliermust be consumed in the same thread.- Throws:
IOException
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seekCeil
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
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seekExact
Seeks to the specified term by ordinal (position) as previously returned byord(). The target ord may be before or after the current ord, and must be within bounds.- Throws:
IOException
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seekExact
Expert: Seeks a specific position byTermStatepreviously obtained fromtermState(). Callers should maintain theTermStateto use this method. Low-level implementations may position the TermsEnum without re-seeking the term dictionary.Seeking by
TermStateshould only be used iff the state was obtained from the sameTermsEnuminstance.NOTE: Using this method with an incompatible
TermStatemight leave thisTermsEnumin undefined state. On a segment levelTermStateinstances are compatible only iff the source and the targetTermsEnumoperate on the same field. If operating on segment level, TermState instances must not be used across segments.NOTE: A seek by
TermStatemight not restore theAttributeSource's state.AttributeSourcestates must be maintained separately if this method is used.- Parameters:
term- the term the TermState corresponds tostate- theTermState- Throws:
IOException
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term
Returns current term. Do not call this when the enum is unpositioned.- Throws:
IOException
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ord
Returns ordinal position for current term. This is an optional method (the codec may throwUnsupportedOperationException). Do not call this when the enum is unpositioned.- Throws:
IOException
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docFreq
Returns the number of documents containing the current term. Do not call this when the enum is unpositioned.TermsEnum.SeekStatus.END.- Throws:
IOException
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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). Note that, like other term measures, this measure does not take deleted documents into account.- Throws:
IOException
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postings
GetPostingsEnumfor the current term. 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.Use this method if you only require documents and frequencies, and do not need any proximity data. This method is equivalent to
postings(reuse, PostingsEnum.FREQS)- Parameters:
reuse- pass a prior PostingsEnum for possible reuse- Throws:
IOException- See Also:
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postings
GetPostingsEnumfor 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.- Parameters:
reuse- pass a prior PostingsEnum for possible reuseflags- specifies which optional per-document values you require; seePostingsEnum.FREQS- Throws:
IOException
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impacts
Return aImpactsEnum.- Throws:
IOException- See Also:
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termState
Expert: Returns the TermsEnums internal state to position the TermsEnum without re-seeking the term dictionary.NOTE: A seek by
TermStatemight not capture theAttributeSource's state. Callers must maintain theAttributeSourcestates separately- Throws:
IOException- See Also:
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