Package org.apache.lucene.analysis.miscellaneous

Class WordDelimiterGraphFilter

  • All Implemented Interfaces:
    Closeable, AutoCloseable
    public final class WordDelimiterGraphFilter
extends TokenFilter
    Splits words into subwords and performs optional transformations on subword groups, producing a correct token graph so that e.g. PhraseQuery can work correctly when this filter is used in the search-time analyzer. Unlike the deprecated WordDelimiterFilter, this token filter produces a correct token graph as output. However, it cannot consume an input token graph correctly. Processing is suppressed by KeywordAttribute.isKeyword()=true.

    Words are split into subwords with the following rules:

    • split on intra-word delimiters (by default, all non alpha-numeric characters): "Wi-Fi" → "Wi", "Fi"
    • split on case transitions: "PowerShot" → "Power", "Shot"
    • split on letter-number transitions: "SD500" → "SD", "500"
    • leading and trailing intra-word delimiters on each subword are ignored: "//hello---there, 'dude'" → "hello", "there", "dude"
    • trailing "'s" are removed for each subword: "O'Neil's" → "O", "Neil"
      • Note: this step isn't performed in a separate filter because of possible subword combinations.
    The GENERATE... options affect how incoming tokens are broken into parts, and the various CATENATE_... parameters affect how those parts are combined.
    • If no CATENATE option is set, then no subword combinations are generated: "PowerShot" → 0:"Power", 1:"Shot" (0 and 1 are the token positions)
    • CATENATE_WORDS means that in addition to the subwords, maximum runs of non-numeric subwords are catenated and produced at the same position of the last subword in the run:
      • "PowerShot" → 0:"Power", 1:"Shot" 1:"PowerShot"
      • "A's+B's&C's" > 0:"A", 1:"B", 2:"C", 2:"ABC"
      • "Super-Duper-XL500-42-AutoCoder!" → 0:"Super", 1:"Duper", 2:"XL", 2:"SuperDuperXL", 3:"500" 4:"42", 5:"Auto", 6:"Coder", 6:"AutoCoder"
    • CATENATE_NUMBERS works like CATENATE_WORDS, but for adjacent digit sequences.
    • CATENATE_ALL smushes together all the token parts without distinguishing numbers and words.
    One use for WordDelimiterGraphFilter is to help match words with different subword delimiters. For example, if the source text contained "wi-fi" one may want "wifi" "WiFi" "wi-fi" "wi+fi" queries to all match. One way of doing so is to specify CATENATE options in the analyzer used for indexing, and not in the analyzer used for querying. Given that the current StandardTokenizer immediately removes many intra-word delimiters, it is recommended that this filter be used after a tokenizer that does not do this (such as WhitespaceTokenizer).

    • Field Detail

      • GENERATE_WORD_PARTS

        public static final int GENERATE_WORD_PARTS
        Causes parts of words to be generated:

        "PowerShot" => "Power" "Shot"

        See Also:
        Constant Field Values

      • GENERATE_NUMBER_PARTS

        public static final int GENERATE_NUMBER_PARTS
        Causes number subwords to be generated:

        "500-42" => "500" "42"

        See Also:
        Constant Field Values

      • CATENATE_WORDS

        public static final int CATENATE_WORDS
        Causes maximum runs of word parts to be catenated:

        "wi-fi" => "wifi"

        See Also:
        Constant Field Values

      • CATENATE_NUMBERS

        public static final int CATENATE_NUMBERS
        Causes maximum runs of number parts to be catenated:

        "500-42" => "50042"

        See Also:
        Constant Field Values

      • CATENATE_ALL

        public static final int CATENATE_ALL
        Causes all subword parts to be catenated:

        "wi-fi-4000" => "wifi4000"

        See Also:
        Constant Field Values

      • PRESERVE_ORIGINAL

        public static final int PRESERVE_ORIGINAL
        Causes original words are preserved and added to the subword list (Defaults to false)

        "500-42" => "500" "42" "500-42"

        See Also:
        Constant Field Values

      • SPLIT_ON_CASE_CHANGE

        public static final int SPLIT_ON_CASE_CHANGE
        Causes lowercase -> uppercase transition to start a new subword.
        See Also:
        Constant Field Values

      • SPLIT_ON_NUMERICS

        public static final int SPLIT_ON_NUMERICS
        If not set, causes numeric changes to be ignored (subwords will only be generated given SUBWORD_DELIM tokens).
        See Also:
        Constant Field Values

      • STEM_ENGLISH_POSSESSIVE

        public static final int STEM_ENGLISH_POSSESSIVE
        Causes trailing "'s" to be removed for each subword

        "O'Neil's" => "O", "Neil"

        See Also:
        Constant Field Values

    • Constructor Detail

      • WordDelimiterGraphFilter

        public WordDelimiterGraphFilter​(TokenStream in,
                                boolean adjustInternalOffsets,
                                byte[] charTypeTable,
                                int configurationFlags,
                                CharArraySet protWords)
        Creates a new WordDelimiterGraphFilter
        Parameters:
        in - TokenStream to be filtered
        adjustInternalOffsets - if the offsets of partial terms should be adjusted
        charTypeTable - table containing character types
        configurationFlags - Flags configuring the filter
        protWords - If not null is the set of tokens to protect from being delimited

      • WordDelimiterGraphFilter

        public WordDelimiterGraphFilter​(TokenStream in,
                                int configurationFlags,
                                CharArraySet protWords)
        Creates a new WordDelimiterGraphFilter using WordDelimiterIterator.DEFAULT_WORD_DELIM_TABLE as its charTypeTable
        Parameters:
        in - TokenStream to be filtered
        configurationFlags - Flags configuring the filter
        protWords - If not null is the set of tokens to protect from being delimited