Class LimitTokenCountFilter

  • All Implemented Interfaces:, java.lang.AutoCloseable

    public final class LimitTokenCountFilter
    extends TokenFilter
    This TokenFilter limits the number of tokens while indexing. It is a replacement for the maximum field length setting inside IndexWriter.

    By default, this filter ignores any tokens in the wrapped TokenStream once the limit has been reached, which can result in reset() being called prior to incrementToken() returning false. For most TokenStream implementations this should be acceptable, and faster then consuming the full stream. If you are wrapping a TokenStream which requires that the full stream of tokens be exhausted in order to function properly, use the consumeAllTokens option.

    • Constructor Detail

      • LimitTokenCountFilter

        public LimitTokenCountFilter​(TokenStream in,
                                     int maxTokenCount)
        Build a filter that only accepts tokens up to a maximum number. This filter will not consume any tokens beyond the maxTokenCount limit
        See Also:
      • LimitTokenCountFilter

        public LimitTokenCountFilter​(TokenStream in,
                                     int maxTokenCount,
                                     boolean consumeAllTokens)
        Build an filter that limits the maximum number of tokens per field.
        in - the stream to wrap
        maxTokenCount - max number of tokens to produce
        consumeAllTokens - whether all tokens from the input must be consumed even if maxTokenCount is reached.
    • Method Detail

      • incrementToken

        public boolean incrementToken()
        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
        false for end of stream; true otherwise
      • reset

        public void reset()
        Description copied from class: TokenFilter
        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).

        NOTE: The default implementation chains the call to the input TokenStream, so be sure to call super.reset() when overriding this method.

        reset in class TokenFilter