Package org.apache.lucene.analysis.miscellaneous

Class ConcatenateGraphFilter

  • All Implemented Interfaces:
    Closeable, AutoCloseable
    public final class ConcatenateGraphFilter
extends TokenStream
    Concatenates/Joins every incoming token with a separator into one output token for every path through the token stream (which is a graph). In simple cases this yields one token, but in the presence of any tokens with a zero positionIncrmeent (e.g. synonyms) it will be more. This filter uses the token bytes, position increment, and position length of the incoming stream. Other attributes are not used or manipulated.

    • Field Detail

      • SEP_LABEL

        public static final int SEP_LABEL
        Represents the default separator between tokens.
        See Also:
        Constant Field Values

      • DEFAULT_MAX_GRAPH_EXPANSIONS

        public static final int DEFAULT_MAX_GRAPH_EXPANSIONS
        See Also:
        Constant Field Values

      • DEFAULT_TOKEN_SEPARATOR

        public static final Character DEFAULT_TOKEN_SEPARATOR

      • DEFAULT_PRESERVE_POSITION_INCREMENTS

        public static final boolean DEFAULT_PRESERVE_POSITION_INCREMENTS
        See Also:
        Constant Field Values

    • Constructor Detail

      • ConcatenateGraphFilter

        public ConcatenateGraphFilter​(TokenStream inputTokenStream)
        Creates a token stream to convert input to a token stream of accepted strings by its token stream graph.

        This constructor uses the default settings of the constants in this class.

      • ConcatenateGraphFilter

        public ConcatenateGraphFilter​(TokenStream inputTokenStream,
                              Character tokenSeparator,
                              boolean preservePositionIncrements,
                              int maxGraphExpansions)
        Creates a token stream to convert input to a token stream of accepted strings by its token stream graph.
        Parameters:
        inputTokenStream - The input/incoming TokenStream
        tokenSeparator - Separator to use for concatenation. Can be null, in this case tokens will be concatenated without any separators.
        preservePositionIncrements - Whether to add an empty token for missing positions. The effect is a consecutive SEP_LABEL. When false, it's as if there were no missing positions (we pretend the surrounding tokens were adjacent).
        maxGraphExpansions - If the tokenStream graph has more than this many possible paths through, then we'll throw TooComplexToDeterminizeException to preserve the stability and memory of the machine.
        Throws:
        TooComplexToDeterminizeException - if the tokenStream graph has more than maxGraphExpansions expansions

    • Method Detail

      • reset

        public void reset()
           throws IOException
        Description copied from class: TokenStream
        This method is called by a consumer before it begins consumption using TokenStream.incrementToken().

        Resets this stream to a clean state. Stateful implementations must implement this method so that they can be reused, just as if they had been created fresh.

        If you override this method, always call super.reset(), otherwise some internal state will not be correctly reset (e.g., Tokenizer will throw IllegalStateException on further usage).

        Overrides:
        reset in class TokenStream
        Throws:
        IOException

      • incrementToken

        public boolean incrementToken()
                       throws IOException
        Description copied from class: TokenStream
        Consumers (i.e., IndexWriter) use this method to advance the stream to the next token. Implementing classes must implement this method and update the appropriate AttributeImpls with the attributes of the next token.

        The producer must make no assumptions about the attributes after the method has been returned: the caller may arbitrarily change it. If the producer needs to preserve the state for subsequent calls, it can use AttributeSource.captureState() to create a copy of the current attribute state.

        This method is called for every token of a document, so an efficient implementation is crucial for good performance. To avoid calls to AttributeSource.addAttribute(Class) and AttributeSource.getAttribute(Class), references to all AttributeImpls that this stream uses should be retrieved during instantiation.

        To ensure that filters and consumers know which attributes are available, the attributes must be added during instantiation. Filters and consumers are not required to check for availability of attributes in TokenStream.incrementToken().

        Specified by:
        incrementToken in class TokenStream
        Returns:
        false for end of stream; true otherwise
        Throws:
        IOException

      • end

        public void end()
         throws IOException
        Description copied from class: TokenStream
        This method is called by the consumer after the last token has been consumed, after TokenStream.incrementToken() returned false (using the new TokenStream API). Streams implementing the old API should upgrade to use this feature.

        This method can be used to perform any end-of-stream operations, such as setting the final offset of a stream. The final offset of a stream might differ from the offset of the last token eg in case one or more whitespaces followed after the last token, but a WhitespaceTokenizer was used.

        Additionally any skipped positions (such as those removed by a stopfilter) can be applied to the position increment, or any adjustment of other attributes where the end-of-stream value may be important.

        If you override this method, always call super.end().

        Overrides:
        end in class TokenStream
        Throws:
        IOException - If an I/O error occurs

      • toAutomaton

        public Automaton toAutomaton()
                      throws IOException
        Converts the tokenStream to an automaton, treating the transition labels as utf-8. Does *not* close it.
        Throws:
        IOException

      • toAutomaton

        public Automaton toAutomaton​(boolean unicodeAware)
                      throws IOException
        Converts the tokenStream to an automaton. Does *not* close it.
        Throws:
        IOException