Class FuzzyQuery

Implements the fuzzy search query. The similarity measurement is based on the Damerau-Levenshtein (optimal string alignment) algorithm, though you can explicitly choose classic Levenshtein by passing false to the transpositions parameter.

this query uses MultiTermQuery.TopTermsScoringBooleanQueryRewrite as default. So terms will be collected and scored according to their edit distance. Only the top terms are used for building the BooleanQuery. It is not recommended to change the rewrite mode for fuzzy queries.

At most, this query will match terms up to MAXIMUM_SUPPORTED_DISTANCE edits. Higher distances (especially with transpositions enabled), are generally not useful and will match a significant amount of the term dictionary. If you really want this, consider using an n-gram indexing technique (such as the SpellChecker in the suggest module) instead.

NOTE: terms of length 1 or 2 will sometimes not match because of how the scaled distance between two terms is computed. For a term to match, the edit distance between the terms must be less than the minimum length term (either the input term, or the candidate term). For example, FuzzyQuery on term "abcd" with maxEdits=2 will not match an indexed term "ab", and FuzzyQuery on term "a" with maxEdits=2 will not match an indexed term "abc".

Inheritance

System.Object

Query

MultiTermQuery

FuzzyQuery

Inherited Members

MultiTermQuery.m_field

MultiTermQuery.m_rewriteMethod

MultiTermQuery.CONSTANT_SCORE_FILTER_REWRITE

MultiTermQuery.SCORING_BOOLEAN_QUERY_REWRITE

MultiTermQuery.CONSTANT_SCORE_BOOLEAN_QUERY_REWRITE

MultiTermQuery.CONSTANT_SCORE_AUTO_REWRITE_DEFAULT

MultiTermQuery.Field

MultiTermQuery.GetTermsEnum(Terms)

MultiTermQuery.Rewrite(IndexReader)

MultiTermQuery.MultiTermRewriteMethod

Query.Boost

Query.ToString()

Query.CreateWeight(IndexSearcher)

Query.ExtractTerms(ISet<Term>)

Query.Clone()

Namespace: Lucene.Net.Search

Assembly: Lucene.Net.dll

Syntax

public class FuzzyQuery : MultiTermQuery

Constructors

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FuzzyQuery(Term)

Calls FuzzyQuery(Term, Int32).

Declaration

public FuzzyQuery(Term term)

Parameters

Type	Name	Description
Term	term

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FuzzyQuery(Term, Int32)

Calls FuzzyQuery(Term, Int32, Int32).

Declaration

public FuzzyQuery(Term term, int maxEdits)

Parameters

Type	Name	Description
Term	term
System.Int32	maxEdits

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FuzzyQuery(Term, Int32, Int32)

Calls FuzzyQuery(Term, Int32, Int32, Int32, Boolean).

Declaration

public FuzzyQuery(Term term, int maxEdits, int prefixLength)

Parameters

Type	Name	Description
Term	term
System.Int32	maxEdits
System.Int32	prefixLength

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FuzzyQuery(Term, Int32, Int32, Int32, Boolean)

Create a new FuzzyQuery that will match terms with an edit distance of at most maxEdits to term. If a prefixLength > 0 is specified, a common prefix of that length is also required.

Declaration

public FuzzyQuery(Term term, int maxEdits, int prefixLength, int maxExpansions, bool transpositions)

Parameters

Type	Name	Description
Term	term	The term to search for
System.Int32	maxEdits	Must be >= 0 and <= MAXIMUM_SUPPORTED_DISTANCE.
System.Int32	prefixLength	Length of common (non-fuzzy) prefix
System.Int32	maxExpansions	The maximum number of terms to match. If this number is greater than MaxClauseCount when the query is rewritten, then the maxClauseCount will be used instead.
System.Boolean	transpositions	`true` if transpositions should be treated as a primitive edit operation. If this is `false`, comparisons will implement the classic Levenshtein algorithm.

Fields

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DefaultMaxEdits

Declaration

public const int DefaultMaxEdits = null

Field Value

Type	Description
System.Int32

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DefaultMaxExpansions

Declaration

public const int DefaultMaxExpansions = null

Field Value

Type	Description
System.Int32

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DefaultMinSimilarity

Declaration

public const float DefaultMinSimilarity = null

Field Value

Type	Description
System.Single

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DefaultPrefixLength

Declaration

public const int DefaultPrefixLength = null

Field Value

Type	Description
System.Int32

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DefaultTranspositions

Declaration

public const bool DefaultTranspositions = null

Field Value

Type	Description
System.Boolean

Properties

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MaxEdits

Declaration

public virtual int MaxEdits { get; }

Property Value

Type	Description
System.Int32	The maximum number of edit distances allowed for this query to match.

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PrefixLength

Returns the non-fuzzy prefix length. This is the number of characters at the start of a term that must be identical (not fuzzy) to the query term if the query is to match that term.

Declaration

public virtual int PrefixLength { get; }

Property Value

Type	Description
System.Int32

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Term

Returns the pattern term.

Declaration

public virtual Term Term { get; }

Property Value

Type	Description
Term

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Transpositions

Returns true if transpositions should be treated as a primitive edit operation. If this is false, comparisons will implement the classic Levenshtein algorithm.

Declaration

public virtual bool Transpositions { get; }

Property Value

Type	Description
System.Boolean

Methods

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Equals(Object)

Declaration

public override bool Equals(object obj)

Parameters

Type	Name	Description
System.Object	obj

Returns

Type	Description
System.Boolean

Overrides

MultiTermQuery.Equals(Object)

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GetHashCode()

Declaration

public override int GetHashCode()

Returns

Type	Description
System.Int32

Overrides

MultiTermQuery.GetHashCode()

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GetTermsEnum(Terms, AttributeSource)

Declaration

protected override TermsEnum GetTermsEnum(Terms terms, AttributeSource atts)

Parameters

Type	Name	Description
Terms	terms
AttributeSource	atts

Returns

Type	Description
TermsEnum

Overrides

MultiTermQuery.GetTermsEnum(Terms, AttributeSource)

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SingleToEdits(Single, Int32)

Helper function to convert from deprecated "minimumSimilarity" fractions to raw edit distances.

NOTE: this was floatToEdits() in Lucene

Declaration

public static int SingleToEdits(float minimumSimilarity, int termLen)

Parameters

Type	Name	Description
System.Single	minimumSimilarity	Scaled similarity
System.Int32	termLen	Length (in unicode codepoints) of the term.

Returns

Type	Description
System.Int32	Equivalent number of maxEdits

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ToString(String)

Declaration

public override string ToString(string field)

Parameters

Type	Name	Description
System.String	field

Returns

Type	Description
System.String

Overrides

Query.ToString(String)