C# Class org.apache.lucene.analysis.miscellaneous.WordDelimiterFilter

Splits words into subwords and performs optional transformations on subword groups. 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 combinations parameter affects how subwords are combined:
  • combinations="0" causes no subword combinations: "PowerShot" → 0:"Power", 1:"Shot" (0 and 1 are the token positions)
  • combinations="1" 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" -gt; 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"
One use for WordDelimiterFilter 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 combinations="1" in the analyzer used for indexing, and combinations="0" (the default) 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).
Inheritance: TokenFilter
Show file Open project: paulirwin/lucene.net Class Usage Examples

Public Methods

Method Description
WordDelimiterFilter ( System.Version matchVersion, TokenStream @in, int configurationFlags, CharArraySet protWords ) : System

Creates a new WordDelimiterFilter using WordDelimiterIterator#DEFAULT_WORD_DELIM_TABLE as its charTypeTable
WordDelimiterFilter ( System.Version matchVersion, TokenStream @in, sbyte charTypeTable, int configurationFlags, CharArraySet protWords ) : System

Creates a new WordDelimiterFilter
incrementToken ( ) : bool
reset ( ) : void

Private Methods

Method Description
InitializeInstanceFields ( ) : void
buffer ( ) : void
concatenate ( WordDelimiterConcatenation concatenation ) : void

Concatenates the saved buffer to the given WordDelimiterConcatenation
flushConcatenation ( WordDelimiterConcatenation concatenation ) : bool

Flushes the given WordDelimiterConcatenation by either writing its concat and then clearing, or just clearing.
generatePart ( bool isSingleWord ) : void

Generates a word/number part, updating the appropriate attributes
has ( int flag ) : bool

Determines whether the given flag is set
isAlpha ( int type ) : bool

Checks if the given word type includes #ALPHA
isDigit ( int type ) : bool

Checks if the given word type includes #DIGIT
isSubwordDelim ( int type ) : bool

Checks if the given word type includes #SUBWORD_DELIM
isUpper ( int type ) : bool

Checks if the given word type includes #UPPER
position ( bool inject ) : int

Get the position increment gap for a subword or concatenation
saveState ( ) : void

Saves the existing attribute states
shouldConcatenate ( int wordType ) : bool

Determines whether to concatenate a word or number if the current word is the given type
shouldGenerateParts ( int wordType ) : bool

Determines whether a word/number part should be generated for a word of the given type

Method Details

WordDelimiterFilter() public method

Creates a new WordDelimiterFilter using WordDelimiterIterator#DEFAULT_WORD_DELIM_TABLE as its charTypeTable
public WordDelimiterFilter ( System.Version matchVersion, TokenStream @in, int configurationFlags, CharArraySet protWords ) : System
matchVersion System.Version
@in TokenStream
configurationFlags int Flags configuring the filter
protWords CharArraySet If not null is the set of tokens to protect from being delimited
return System

WordDelimiterFilter() public method

Creates a new WordDelimiterFilter
public WordDelimiterFilter ( System.Version matchVersion, TokenStream @in, sbyte charTypeTable, int configurationFlags, CharArraySet protWords ) : System
matchVersion System.Version
@in TokenStream
charTypeTable sbyte table containing character types
configurationFlags int Flags configuring the filter
protWords CharArraySet If not null is the set of tokens to protect from being delimited
return System

incrementToken() public method

public incrementToken ( ) : bool
return bool

reset() public method

public reset ( ) : void
return void