Package org.apache.lucene.search.suggest.analyzing

Class FuzzySuggester

  • public final class FuzzySuggester
extends AnalyzingSuggester
    Implements a fuzzy AnalyzingSuggester. The similarity measurement is based on the Damerau-Levenshtein (optimal string alignment) algorithm, though you can explicitly choose classic Levenshtein by passing false for the transpositions parameter.

    At most, this query will match terms up to 2 edits. Higher distances are not supported. Note that the fuzzy distance is measured in "byte space" on the bytes returned by the TokenStream's TermToBytesRefAttribute, usually UTF8. By default the analyzed bytes must be at least 3 DEFAULT_MIN_FUZZY_LENGTH bytes before any edits are considered. Furthermore, the first 1 DEFAULT_NON_FUZZY_PREFIX byte is not allowed to be edited. We allow up to 1 (@link #DEFAULT_MAX_EDITS} edit. If unicodeAware parameter in the constructor is set to true, maxEdits, minFuzzyLength, transpositions and nonFuzzyPrefix are measured in Unicode code points (actual letters) instead of bytes.

    NOTE: This suggester does not boost suggestions that required no edits over suggestions that did require edits. This is a known limitation.

    Note: complex query analyzers can have a significant impact on the lookup performance. It's recommended to not use analyzers that drop or inject terms like synonyms to keep the complexity of the prefix intersection low for good lookup performance. At index time, complex analyzers can safely be used.

    • Field Detail

      • DEFAULT_UNICODE_AWARE

        public static final boolean DEFAULT_UNICODE_AWARE
        Measure maxEdits, minFuzzyLength, transpositions and nonFuzzyPrefix parameters in Unicode code points (actual letters) instead of bytes.
        See Also:
        Constant Field Values

      • DEFAULT_NON_FUZZY_PREFIX

        public static final int DEFAULT_NON_FUZZY_PREFIX
        The default prefix length where edits are not allowed.
        See Also:
        Constant Field Values

      • DEFAULT_MAX_EDITS

        public static final int DEFAULT_MAX_EDITS
        The default maximum number of edits for fuzzy suggestions.
        See Also:
        Constant Field Values

    • Constructor Detail

      • FuzzySuggester

        public FuzzySuggester​(Analyzer analyzer)
        Creates a FuzzySuggester instance initialized with default values.
        Parameters:
        analyzer - the analyzer used for this suggester

      • FuzzySuggester

        public FuzzySuggester​(Analyzer indexAnalyzer,
                      Analyzer queryAnalyzer)
        Creates a FuzzySuggester instance with an index & a query analyzer initialized with default values.
        Parameters:
        indexAnalyzer - Analyzer that will be used for analyzing suggestions while building the index.
        queryAnalyzer - Analyzer that will be used for analyzing query text during lookup

      • FuzzySuggester

        public FuzzySuggester​(Analyzer indexAnalyzer,
                      Analyzer queryAnalyzer,
                      int options,
                      int maxSurfaceFormsPerAnalyzedForm,
                      int maxGraphExpansions,
                      boolean preservePositionIncrements,
                      int maxEdits,
                      boolean transpositions,
                      int nonFuzzyPrefix,
                      int minFuzzyLength,
                      boolean unicodeAware)
        Creates a FuzzySuggester instance.
        Parameters:
        indexAnalyzer - Analyzer that will be used for analyzing suggestions while building the index.
        queryAnalyzer - Analyzer that will be used for analyzing query text during lookup
        options - see AnalyzingSuggester.EXACT_FIRST, AnalyzingSuggester.PRESERVE_SEP
        maxSurfaceFormsPerAnalyzedForm - Maximum number of surface forms to keep for a single analyzed form. When there are too many surface forms we discard the lowest weighted ones.
        maxGraphExpansions - Maximum number of graph paths to expand from the analyzed form. Set this to -1 for no limit.
        preservePositionIncrements - Whether position holes should appear in the automaton
        maxEdits - must be >= 0 and <= LevenshteinAutomata.MAXIMUM_SUPPORTED_DISTANCE .
        transpositions - true if transpositions should be treated as a primitive edit operation. If this is false, comparisons will implement the classic Levenshtein algorithm.
        nonFuzzyPrefix - length of common (non-fuzzy) prefix (see default DEFAULT_NON_FUZZY_PREFIX
        minFuzzyLength - minimum length of lookup key before any edits are allowed (see default DEFAULT_MIN_FUZZY_LENGTH)
        unicodeAware - operate Unicode code points instead of bytes.