Package org.apache.lucene.search.suggest.fst

Class FSTCompletion

  • public class FSTCompletion
extends java.lang.Object
    Finite state automata based implementation of "autocomplete" functionality.
    See Also:
    FSTCompletionBuilder

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      static class  FSTCompletion.Completion
      A single completion for a given key.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      static int DEFAULT_BUCKETS
      Default number of buckets.

    • Constructor Summary

      Constructors 
      Constructor Description
      FSTCompletion​(FST<java.lang.Object> automaton)
      Defaults to higher weights first and exact first.
      FSTCompletion​(FST<java.lang.Object> automaton, boolean higherWeightsFirst, boolean exactFirst)
      Constructs an FSTCompletion, specifying higherWeightsFirst and exactFirst.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      int getBucket​(java.lang.CharSequence key)
      Returns the bucket assigned to a given key (if found) or -1 if no exact match exists.
      int getBucketCount()
      Returns the bucket count (discretization thresholds).
      FST<java.lang.Object> getFST()
      Returns the internal automaton.
      java.util.List<FSTCompletion.Completion> lookup​(java.lang.CharSequence key, int num)
      Lookup suggestions to key.

      • Methods inherited from class java.lang.Object

        equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Field Detail

      • DEFAULT_BUCKETS

        public static final int DEFAULT_BUCKETS
        Default number of buckets.
        See Also:
        Constant Field Values

    • Constructor Detail

      • FSTCompletion

        public FSTCompletion​(FST<java.lang.Object> automaton,
                     boolean higherWeightsFirst,
                     boolean exactFirst)
        Constructs an FSTCompletion, specifying higherWeightsFirst and exactFirst.
        Parameters:
        automaton - Automaton with completions. See FSTCompletionBuilder.
        higherWeightsFirst - Return most popular suggestions first. This is the default behavior for this implementation. Setting it to false has no effect (use constant term weights to sort alphabetically only).
        exactFirst - Find and push an exact match to the first position of the result list if found.

    • Method Detail

      • lookup

        public java.util.List<FSTCompletion.Completion> lookup​(java.lang.CharSequence key,
                                                       int num)
        Lookup suggestions to key.
        Parameters:
        key - The prefix to which suggestions should be sought.
        num - At most this number of suggestions will be returned.
        Returns:
        Returns the suggestions, sorted by their approximated weight first (decreasing) and then alphabetically (UTF-8 codepoint order).

      • getBucketCount

        public int getBucketCount()
        Returns the bucket count (discretization thresholds).

      • getBucket

        public int getBucket​(java.lang.CharSequence key)
        Returns the bucket assigned to a given key (if found) or -1 if no exact match exists.

      • getFST

        public FST<java.lang.Object> getFST()
        Returns the internal automaton.