org.apache.lucene.analysis.miscellaneous
Class WordDelimiterFilter

java.lang.Object
  org.apache.lucene.util.AttributeSource
      org.apache.lucene.analysis.TokenStream
          org.apache.lucene.analysis.TokenFilter
              org.apache.lucene.analysis.miscellaneous.WordDelimiterFilter

All Implemented Interfaces:

Closeable

public final class WordDelimiterFilter
extends TokenFilter

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).

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource

AttributeSource.AttributeFactory, AttributeSource.State

Field Summary

static int	ALPHA
static int	ALPHANUM
static int	CATENATE_ALL Causes all subword parts to be catenated: "wi-fi-4000" => "wifi4000"
static int	CATENATE_NUMBERS Causes maximum runs of word parts to be catenated: "wi-fi" => "wifi"
static int	CATENATE_WORDS Causes maximum runs of word parts to be catenated: "wi-fi" => "wifi"
static int	DIGIT
static int	GENERATE_NUMBER_PARTS Causes number subwords to be generated: "500-42" => "500" "42"
static int	GENERATE_WORD_PARTS Causes parts of words to be generated: "PowerShot" => "Power" "Shot"
static int	LOWER
static int	PRESERVE_ORIGINAL Causes original words are preserved and added to the subword list (Defaults to false) "500-42" => "500" "42" "500-42"
static int	SPLIT_ON_CASE_CHANGE If not set, causes case changes to be ignored (subwords will only be generated given SUBWORD_DELIM tokens)
static int	SPLIT_ON_NUMERICS If not set, causes numeric changes to be ignored (subwords will only be generated given SUBWORD_DELIM tokens).
static int	STEM_ENGLISH_POSSESSIVE Causes trailing "'s" to be removed for each subword "O'Neil's" => "O", "Neil"
static int	SUBWORD_DELIM
static int	UPPER

Fields inherited from class org.apache.lucene.analysis.TokenFilter

input

Constructor Summary

WordDelimiterFilter(TokenStream in, byte[] charTypeTable, int configurationFlags, CharArraySet protWords)
Creates a new WordDelimiterFilter

WordDelimiterFilter(TokenStream in, int configurationFlags, CharArraySet protWords)
Creates a new WordDelimiterFilter using WordDelimiterIterator.DEFAULT_WORD_DELIM_TABLE as its charTypeTable

Method Summary

boolean	incrementToken()
void	reset()

Methods inherited from class org.apache.lucene.analysis.TokenFilter

close, end

Methods inherited from class org.apache.lucene.util.AttributeSource

addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, restoreState, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

LOWER

public static final int LOWER

See Also:

Constant Field Values

UPPER

public static final int UPPER

See Also:

Constant Field Values

DIGIT

public static final int DIGIT

See Also:

Constant Field Values

SUBWORD_DELIM

public static final int SUBWORD_DELIM

See Also:

Constant Field Values

ALPHA

public static final int ALPHA

See Also:

Constant Field Values

ALPHANUM

public static final int ALPHANUM

See Also:

Constant Field Values

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 word parts to be catenated:

"wi-fi" => "wifi"

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

If not set, causes case changes to be ignored (subwords will only be generated given SUBWORD_DELIM tokens)

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

WordDelimiterFilter

public WordDelimiterFilter(TokenStream in,
                           byte[] charTypeTable,
                           int configurationFlags,
                           CharArraySet protWords)

Creates a new WordDelimiterFilter

Parameters:

in - TokenStream to be filtered

charTypeTable - table containing character types

configurationFlags - Flags configuring the filter

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

WordDelimiterFilter

public WordDelimiterFilter(TokenStream in,
                           int configurationFlags,
                           CharArraySet protWords)

Creates a new WordDelimiterFilter 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

incrementToken

public boolean incrementToken()
                       throws IOException

Specified by:

incrementToken in class TokenStream

Throws:

IOException

reset

public void reset()
           throws IOException

Overrides:

reset in class TokenFilter

Throws:

IOException