Package org.apache.lucene.analysis.miscellaneous

Class WordDelimiterGraphFilter

  • All Implemented Interfaces:
    java.io.Closeable, java.lang.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

      • protWords

        final CharArraySet protWords
        If not null is the set of tokens to protect from being delimited

      • flags

        private final int flags

      • bufferedParts

        private int[] bufferedParts

      • bufferedLen

        private int bufferedLen

      • bufferedPos

        private int bufferedPos

      • bufferedTermParts

        private char[][] bufferedTermParts

      • adjustInternalOffsets

        private final boolean adjustInternalOffsets

      • lastConcatCount

        private int lastConcatCount

      • accumPosInc

        private int accumPosInc

      • savedTermBuffer

        private char[] savedTermBuffer

      • savedTermLength

        private int savedTermLength

      • savedStartOffset

        private int savedStartOffset

      • savedEndOffset

        private int savedEndOffset

      • lastStartOffset

        private int lastStartOffset

      • adjustingOffsets

        private boolean adjustingOffsets

      • wordPos

        private int wordPos

    • 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

    • Method Detail

      • bufferWordParts

        private void bufferWordParts()
                      throws java.io.IOException
        Iterates all words parts and concatenations, buffering up the term parts we should return.
        Throws:
        java.io.IOException

      • incrementToken

        public boolean incrementToken()
                       throws java.io.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:
        java.io.IOException

      • reset

        public void reset()
           throws java.io.IOException
        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.

        Overrides:
        reset in class TokenFilter
        Throws:
        java.io.IOException

      • buffer

        void buffer​(int startPos,
            int endPos,
            int startPart,
            int endPart)
        startPos, endPos -> graph start/end position startPart, endPart -> slice of the original term for this part

      • buffer

        void buffer​(char[] termPart,
            int startPos,
            int endPos,
            int startPart,
            int endPart)
        a null termPart means it's a simple slice of the original term

      • saveState

        private void saveState()
        Saves the existing attribute states

      • flushConcatenation

        private void flushConcatenation​(WordDelimiterGraphFilter.WordDelimiterConcatenation concat)
        Flushes the given WordDelimiterConcatenation by either writing its concat and then clearing, or just clearing.
        Parameters:
        concat - WordDelimiterConcatenation that will be flushed

      • shouldConcatenate

        private boolean shouldConcatenate​(int wordType)
        Determines whether to concatenate a word or number if the current word is the given type
        Parameters:
        wordType - Type of the current word used to determine if it should be concatenated
        Returns:
        true if concatenation should occur, false otherwise

      • shouldGenerateParts

        private boolean shouldGenerateParts​(int wordType)
        Determines whether a word/number part should be generated for a word of the given type
        Parameters:
        wordType - Type of the word used to determine if a word/number part should be generated
        Returns:
        true if a word/number part should be generated, false otherwise

      • concatenate

        private void concatenate​(WordDelimiterGraphFilter.WordDelimiterConcatenation concatenation)
        Concatenates the saved buffer to the given WordDelimiterConcatenation
        Parameters:
        concatenation - WordDelimiterConcatenation to concatenate the buffer to

      • has

        private boolean has​(int flag)
        Determines whether the given flag is set
        Parameters:
        flag - Flag to see if set
        Returns:
        true if flag is set

      • flagsToString

        public static java.lang.String flagsToString​(int flags)
        Returns string representation of configuration flags