Package org.apache.lucene.analysis.shingle

Class ShingleFilter

  • All Implemented Interfaces:
    Closeable, AutoCloseable
    public final class ShingleFilter
extends TokenFilter
    A ShingleFilter constructs shingles (token n-grams) from a token stream. In other words, it creates combinations of tokens as a single token.

    For example, the sentence "please divide this sentence into shingles" might be tokenized into shingles "please divide", "divide this", "this sentence", "sentence into", and "into shingles".

    This filter handles position increments > 1 by inserting filler tokens (tokens with termtext "_"). It does not handle a position increment of 0.

    • Field Detail

      • DEFAULT_FILLER_TOKEN

        public static final String DEFAULT_FILLER_TOKEN
        filler token for when positionIncrement is more than 1
        See Also:
        Constant Field Values

      • DEFAULT_MAX_SHINGLE_SIZE

        public static final int DEFAULT_MAX_SHINGLE_SIZE
        default maximum shingle size is 2.
        See Also:
        Constant Field Values

      • DEFAULT_MIN_SHINGLE_SIZE

        public static final int DEFAULT_MIN_SHINGLE_SIZE
        default minimum shingle size is 2.
        See Also:
        Constant Field Values

      • DEFAULT_TOKEN_TYPE

        public static final String DEFAULT_TOKEN_TYPE
        default token type attribute value is "shingle"
        See Also:
        Constant Field Values

      • DEFAULT_TOKEN_SEPARATOR

        public static final String DEFAULT_TOKEN_SEPARATOR
        The default string to use when joining adjacent tokens to form a shingle
        See Also:
        Constant Field Values

    • Constructor Detail

      • ShingleFilter

        public ShingleFilter​(TokenStream input,
                     int minShingleSize,
                     int maxShingleSize)
        Constructs a ShingleFilter with the specified shingle size from the TokenStream input
        Parameters:
        input - input stream
        minShingleSize - minimum shingle size produced by the filter.
        maxShingleSize - maximum shingle size produced by the filter.

      • ShingleFilter

        public ShingleFilter​(TokenStream input,
                     int maxShingleSize)
        Constructs a ShingleFilter with the specified shingle size from the TokenStream input
        Parameters:
        input - input stream
        maxShingleSize - maximum shingle size produced by the filter.

      • ShingleFilter

        public ShingleFilter​(TokenStream input)
        Construct a ShingleFilter with default shingle size: 2.
        Parameters:
        input - input stream

      • ShingleFilter

        public ShingleFilter​(TokenStream input,
                     String tokenType)
        Construct a ShingleFilter with the specified token type for shingle tokens and the default shingle size: 2
        Parameters:
        input - input stream
        tokenType - token type for shingle tokens

    • Method Detail

      • setTokenType

        public void setTokenType​(String tokenType)
        Set the type of the shingle tokens produced by this filter. (default: "shingle")
        Parameters:
        tokenType - token tokenType

      • setOutputUnigrams

        public void setOutputUnigrams​(boolean outputUnigrams)
        Shall the output stream contain the input tokens (unigrams) as well as shingles? (default: true.)
        Parameters:
        outputUnigrams - Whether or not the output stream shall contain the input tokens (unigrams)

      • setOutputUnigramsIfNoShingles

        public void setOutputUnigramsIfNoShingles​(boolean outputUnigramsIfNoShingles)
        Shall we override the behavior of outputUnigrams==false for those times when no shingles are available (because there are fewer than minShingleSize tokens in the input stream)? (default: false.)

        Note that if outputUnigrams==true, then unigrams are always output, regardless of whether any shingles are available.

        Parameters:
        outputUnigramsIfNoShingles - Whether or not to output a single unigram when no shingles are available.

      • setMaxShingleSize

        public void setMaxShingleSize​(int maxShingleSize)
        Set the max shingle size (default: 2)
        Parameters:
        maxShingleSize - max size of output shingles

      • setMinShingleSize

        public void setMinShingleSize​(int minShingleSize)
        Set the min shingle size (default: 2).

        This method requires that the passed in minShingleSize is not greater than maxShingleSize, so make sure that maxShingleSize is set before calling this method.

        The unigram output option is independent of the min shingle size.

        Parameters:
        minShingleSize - min size of output shingles

      • setTokenSeparator

        public void setTokenSeparator​(String tokenSeparator)
        Sets the string to use when joining adjacent tokens to form a shingle
        Parameters:
        tokenSeparator - used to separate input stream tokens in output shingles

      • setFillerToken

        public void setFillerToken​(String fillerToken)
        Sets the string to insert for each position at which there is no token (i.e., when position increment is greater than one).
        Parameters:
        fillerToken - string to insert at each position where there is no token