org.apache.lucene.search

## Class FuzzyQuery

- java.lang.Object
- - org.apache.lucene.search.Query
  - - org.apache.lucene.search.MultiTermQuery
    - - org.apache.lucene.search.FuzzyQuery

-     public class FuzzyQuery
      extends MultiTermQuery

  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.TopTermsBlendedFreqScoringRewrite` 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 2 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".

- - ### Nested Class Summary

    - ### Nested classes/interfaces inherited from class org.apache.lucene.search.MultiTermQuery

      `MultiTermQuery.RewriteMethod, MultiTermQuery.TopTermsBlendedFreqScoringRewrite, MultiTermQuery.TopTermsBoostOnlyBooleanQueryRewrite, MultiTermQuery.TopTermsScoringBooleanQueryRewrite`

  - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static int` | `defaultMaxEdits`
    `static int` | `defaultMaxExpansions`
    `static float` | `defaultMinSimilarity` Deprecated. pass integer edit distances instead.
    `static int` | `defaultPrefixLength`
    `static boolean` | `defaultTranspositions`

    - ### Fields inherited from class org.apache.lucene.search.MultiTermQuery

      `CONSTANT_SCORE_BOOLEAN_REWRITE, CONSTANT_SCORE_REWRITE, field, rewriteMethod, SCORING_BOOLEAN_REWRITE`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `FuzzyQuery(Term term)` Calls `FuzzyQuery(term, defaultMaxEdits)`.
    `FuzzyQuery(Term term, int maxEdits)` Calls `FuzzyQuery(term, maxEdits, defaultPrefixLength)`.
    `FuzzyQuery(Term term, int maxEdits, int prefixLength)` Calls `FuzzyQuery(term, maxEdits, prefixLength, defaultMaxExpansions, defaultTranspositions)`.
    `FuzzyQuery(Term term, int maxEdits, int prefixLength, int maxExpansions, boolean transpositions)` Create a new FuzzyQuery that will match terms with an edit distance of at most `maxEdits` to `term`.

  - ### Method Summary

    All Methods Static Methods Instance Methods Concrete Methods Deprecated Methods
    Modifier and Type | Method and Description
    --- | ---
    `boolean` | `equals(Object obj)` Override and implement query instance equivalence properly in a subclass.
    `static int` | `floatToEdits(float minimumSimilarity, int termLen)` Deprecated. pass integer edit distances instead.
    `CompiledAutomaton` | `getAutomata()` Returns the compiled automata used to match terms
    `int` | `getMaxEdits()`
    `int` | `getPrefixLength()` Returns the non-fuzzy prefix length.
    `Term` | `getTerm()` Returns the pattern term.
    `protected TermsEnum` | `getTermsEnum(Terms terms, AttributeSource atts)` Construct the enumeration to be used, expanding the pattern term.
    `boolean` | `getTranspositions()` Returns true if transpositions should be treated as a primitive edit operation.
    `int` | `hashCode()` Override and implement query hash code properly in a subclass.
    `String` | `toString(String field)` Prints a query to a string, with `field` assumed to be the default field and omitted.
    `void` | `visit(QueryVisitor visitor)` Recurse through the query tree, visiting any child queries

    - ### Methods inherited from class org.apache.lucene.search.MultiTermQuery

      `getField, getRewriteMethod, getTermsEnum, rewrite, setRewriteMethod`

    - ### Methods inherited from class org.apache.lucene.search.Query

      `classHash, createWeight, sameClassAs, toString`

    - ### Methods inherited from class java.lang.Object

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

- - ### Field Detail

    - #### defaultMaxEdits

          public static final int defaultMaxEdits

      See Also:
        Constant Field Values

    - #### defaultPrefixLength

          public static final int defaultPrefixLength

      See Also:
        Constant Field Values

    - #### defaultMaxExpansions

          public static final int defaultMaxExpansions

      See Also:
        Constant Field Values

    - #### defaultTranspositions

          public static final boolean defaultTranspositions

      See Also:
        Constant Field Values

    - #### defaultMinSimilarity

          @Deprecated
          public static final float defaultMinSimilarity

      Deprecated. pass integer edit distances instead.
      See Also:
        Constant Field Values

  - ### Constructor Detail

    - #### FuzzyQuery

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

      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.
      Parameters:
        `term` - the term to search for
        `maxEdits` - must be `>= 0` and `<=` `LevenshteinAutomata.MAXIMUM_SUPPORTED_DISTANCE`.
        `prefixLength` - length of common (non-fuzzy) prefix
        `maxExpansions` - the maximum number of terms to match. If this number is greater than `BooleanQuery.getMaxClauseCount()` when the query is rewritten, then the maxClauseCount will be used instead.
        `transpositions` - true if transpositions should be treated as a primitive edit operation. If this is false, comparisons will implement the classic Levenshtein algorithm.

    - #### FuzzyQuery

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

      Calls `FuzzyQuery(term, maxEdits, prefixLength, defaultMaxExpansions, defaultTranspositions)`.

    - #### FuzzyQuery

          public FuzzyQuery(Term term,
                            int maxEdits)

      Calls `FuzzyQuery(term, maxEdits, defaultPrefixLength)`.

    - #### FuzzyQuery

          public FuzzyQuery(Term term)

      Calls `FuzzyQuery(term, defaultMaxEdits)`.

  - ### Method Detail

    - #### getMaxEdits

          public int getMaxEdits()

      Returns:
        the maximum number of edit distances allowed for this query to match.

    - #### getPrefixLength

          public int getPrefixLength()

      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.

    - #### getTranspositions

          public boolean getTranspositions()

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

    - #### getAutomata

          public CompiledAutomaton getAutomata()

      Returns the compiled automata used to match terms

    - #### visit

          public void visit(QueryVisitor visitor)

      Description copied from class: `Query`
      Recurse through the query tree, visiting any child queries
      Overrides:
        `visit` in class `Query`
      Parameters:
        `visitor` - a QueryVisitor to be called by each query in the tree

    - #### getTermsEnum

          protected TermsEnum getTermsEnum(Terms terms,
                                           AttributeSource atts)
                                    throws IOException

      Description copied from class: `MultiTermQuery`
      Construct the enumeration to be used, expanding the pattern term. This method should only be called if the field exists (ie, implementations can assume the field does exist). This method should not return null (should instead return `TermsEnum.EMPTY` if no terms match). The TermsEnum must already be positioned to the first matching term. The given `AttributeSource` is passed by the `MultiTermQuery.RewriteMethod` to share information between segments, for example `TopTermsRewrite` uses it to share maximum competitive boosts
      Specified by:
        `getTermsEnum` in class `MultiTermQuery`
      Throws:
        `IOException`

    - #### getTerm

          public Term getTerm()

      Returns the pattern term.

    - #### toString

          public String toString(String field)

      Description copied from class: `Query`
      Prints a query to a string, with `field` assumed to be the default field and omitted.
      Specified by:
        `toString` in class `Query`

    - #### hashCode

          public int hashCode()

      Description copied from class: `Query`
      Override and implement query hash code properly in a subclass. This is required so that `QueryCache` works properly.
      Overrides:
        `hashCode` in class `MultiTermQuery`
      See Also:
        `Query.equals(Object)`

    - #### equals

          public boolean equals(Object obj)

      Description copied from class: `Query`
      Override and implement query instance equivalence properly in a subclass. This is required so that `QueryCache` works properly. Typically a query will be equal to another only if it's an instance of the same class and its document-filtering properties are identical that other instance. Utility methods are provided for certain repetitive code.
      Overrides:
        `equals` in class `MultiTermQuery`
      See Also:
        `Query.sameClassAs(Object)`, `Query.classHash()`

    - #### floatToEdits

          @Deprecated
          public static int floatToEdits(float minimumSimilarity,
                                                     int termLen)

      Deprecated. pass integer edit distances instead.
      Helper function to convert from deprecated "minimumSimilarity" fractions to raw edit distances.
      Parameters:
        `minimumSimilarity` - scaled similarity
        `termLen` - length (in unicode codepoints) of the term.
      Returns:
        equivalent number of maxEdits

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