Class 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
System.Object
AttributeSource
TokenStream
TokenFilter
WordDelimiterFilter
Implements
System.IDisposable
Inherited Members
System.Object.Equals(System.Object, System.Object)
System.Object.GetType()
System.Object.MemberwiseClone()
System.Object.ReferenceEquals(System.Object, System.Object)
Namespace: Lucene.Net.Analysis.Miscellaneous
Assembly: Lucene.Net.Analysis.Common.dll
Syntax
public sealed class WordDelimiterFilter : TokenFilter, IDisposable

Constructors

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WordDelimiterFilter(LuceneVersion, TokenStream, WordDelimiterFlags, CharArraySet)

Creates a new WordDelimiterFilter using DEFAULT_WORD_DELIM_TABLE as its charTypeTable

Declaration
public WordDelimiterFilter(LuceneVersion matchVersion, TokenStream in, WordDelimiterFlags configurationFlags, CharArraySet protWords)
Parameters
Type Name Description
LuceneVersion matchVersion

lucene compatibility version

TokenStream in

TokenStream to be filtered

WordDelimiterFlags configurationFlags

Flags configuring the filter

CharArraySet protWords

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

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WordDelimiterFilter(LuceneVersion, TokenStream, Byte[], WordDelimiterFlags, CharArraySet)

Creates a new WordDelimiterFilter

Declaration
public WordDelimiterFilter(LuceneVersion matchVersion, TokenStream in, byte[] charTypeTable, WordDelimiterFlags configurationFlags, CharArraySet protWords)
Parameters
Type Name Description
LuceneVersion matchVersion

lucene compatibility version

TokenStream in

TokenStream to be filtered

System.Byte[] charTypeTable

table containing character types

WordDelimiterFlags configurationFlags

Flags configuring the filter

CharArraySet protWords

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

Fields

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ALPHA

Declaration
public const int ALPHA = 3
Field Value
Type Description
System.Int32
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ALPHANUM

Declaration
public const int ALPHANUM = 7
Field Value
Type Description
System.Int32
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DIGIT

Declaration
public const int DIGIT = 4
Field Value
Type Description
System.Int32
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LOWER

Declaration
public const int LOWER = 1
Field Value
Type Description
System.Int32
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SUBWORD_DELIM

Declaration
public const int SUBWORD_DELIM = 8
Field Value
Type Description
System.Int32
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UPPER

Declaration
public const int UPPER = 2
Field Value
Type Description
System.Int32

Methods

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IncrementToken()

Declaration
public override bool IncrementToken()
Returns
Type Description
System.Boolean
Overrides
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Reset()

Declaration
public override void Reset()
Overrides

Implements

System.IDisposable