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:

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).

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	IGNORE_KEYWORDS Suppresses processing terms with KeywordAttribute.isKeyword()=true.
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 java.lang.String	flagsToString(int flags) Returns string representation of configuration flags
boolean	incrementToken() Consumers (i.e., IndexWriter) use this method to advance the stream to the next token.
void	reset() This method is called by a consumer before it begins consumption using TokenStream.incrementToken().
java.lang.String	toString() Returns a string consisting of the class's simple name, the hex representation of the identity hash code, and the current reflection of all attributes.

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

IGNORE_KEYWORDS

public static final int IGNORE_KEYWORDS

Suppresses processing terms with KeywordAttribute.isKeyword()=true.

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 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

flagsToString

public static java.lang.String flagsToString(int flags)

Returns string representation of configuration flags

toString

public java.lang.String toString()

Description copied from class: AttributeSource

Returns a string consisting of the class's simple name, the hex representation of the identity hash code, and the current reflection of all attributes.

Overrides:

toString in class AttributeSource

See Also:

AttributeSource.reflectAsString(boolean)