Class ConcatenateGraphFilter

java.lang.Object
org.apache.lucene.util.AttributeSource
org.apache.lucene.analysis.TokenStream
org.apache.lucene.analysis.miscellaneous.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 Details

  • Constructor Details

    • 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
    • ConcatenateGraphFilter

      public ConcatenateGraphFilter(TokenStream inputTokenStream, boolean preserveSep, boolean preservePositionIncrements, int maxGraphExpansions)
      Parameters:
      preserveSep - Whether SEP_LABEL should separate the input tokens in the concatenated token
  • Method Details

    • 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
    • close

      public void close() throws IOException
      Description copied from class: TokenStream
      Releases resources associated with this stream.

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

      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Overrides:
      close in class TokenStream
      Throws:
      IOException
    • 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
    • replaceSep

      private static Automaton replaceSep(Automaton a, Character tokenSeparator)