Package org.apache.lucene.index

Class TermsEnum

    • 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 abstract AttributeSource attributes()
        Returns the related attributes.

      • seekExact

        public abstract boolean seekExact​(BytesRef text)
                           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).
        Returns:
        true if the term is found; return false if the enum is unpositioned.
        Throws:
        IOException

      • seekCeil

        public abstract 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 abstract 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 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.

        Parameters:
        term - the term the TermState corresponds to
        state - the TermState
        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). Note that, like other term measures, this measure does not take deleted documents into account.
        Throws:
        IOException

      • postings

        public abstract PostingsEnum postings​(PostingsEnum reuse,
                                      int flags)
                               throws IOException
        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.

        Parameters:
        reuse - pass a prior PostingsEnum for possible reuse
        flags - specifies which optional per-document values you require; see PostingsEnum.FREQS
        Throws:
        IOException