org.apache.lucene.analysis.miscellaneous

Class WordDelimiterGraphFilter

java.lang.Object

org.apache.lucene.util.AttributeSource

org.apache.lucene.analysis.TokenStream

org.apache.lucene.analysis.TokenFilter

org.apache.lucene.analysis.miscellaneous.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.

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" > 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 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 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.State

Field Summary

Fields

Modifier and Type	Field and Description
static int	CATENATE_ALL Causes all subword parts to be catenated:
static int	CATENATE_NUMBERS Causes maximum runs of number parts to be catenated:
static int	CATENATE_WORDS Causes maximum runs of word parts to be catenated:
static int	GENERATE_NUMBER_PARTS Causes number subwords to be generated:
static int	GENERATE_WORD_PARTS Causes parts of words to be generated:
static int	PRESERVE_ORIGINAL Causes original words are preserved and added to the subword list (Defaults to false)
static int	SPLIT_ON_CASE_CHANGE Causes lowercase -> uppercase transition to start a new subword.
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

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

input

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

DEFAULT_TOKEN_ATTRIBUTE_FACTORY

Constructor Summary

Constructors

Constructor and Description
WordDelimiterGraphFilter(TokenStream in, byte[] charTypeTable, int configurationFlags, CharArraySet protWords) Creates a new WordDelimiterGraphFilter
WordDelimiterGraphFilter(TokenStream in, int configurationFlags, CharArraySet protWords) Creates a new WordDelimiterGraphFilter using WordDelimiterIterator.DEFAULT_WORD_DELIM_TABLE as its charTypeTable

Method Summary

Modifier and Type	Method and Description
static String	flagsToString(int flags) Returns string representation of configuration flags
boolean	incrementToken()
void	reset()
String	toString()

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, endAttributes, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, removeAllAttributes, restoreState

Methods inherited from class java.lang.Object

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

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,
                                byte[] charTypeTable,
                                int configurationFlags,
                                CharArraySet protWords)

Creates a new WordDelimiterGraphFilter

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

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

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

flagsToString

public static String flagsToString(int flags)

Returns string representation of configuration flags

toString

public String toString()

Overrides:

toString in class AttributeSource