org.apache.lucene.search.suggest.fst
Class FSTCompletion

java.lang.Object
  org.apache.lucene.search.suggest.fst.FSTCompletion

public class FSTCompletion
extends Object

Finite state automata based implementation of "autocomplete" functionality.

See Also:

FSTCompletionBuilder

WARNING: This API is experimental and might change in incompatible ways in the next release.

Nested Class Summary

static class

FSTCompletion.Completion A single completion for a given key.

Field Summary

static int

DEFAULT_BUCKETS Default number of buckets.

Constructor Summary

FSTCompletion(FST<Object> automaton)
Defaults to higher weights first and exact first.

FSTCompletion(FST<Object> automaton, boolean higherWeightsFirst, boolean exactFirst)
Constructs an FSTCompletion, specifying higherWeightsFirst and exactFirst.

Method Summary

int	getBucket(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<Object>	getFST() Returns the internal automaton.
List<FSTCompletion.Completion>	lookup(CharSequence key, int num) Lookup suggestions to key.

Methods inherited from class java.lang.Object

clone, equals, finalize, 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<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.

FSTCompletion

public FSTCompletion(FST<Object> automaton)

Defaults to higher weights first and exact first.

See Also:

FSTCompletion(FST, boolean, boolean)

Method Detail

lookup

public List<FSTCompletion.Completion> lookup(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(CharSequence key)

Returns the bucket assigned to a given key (if found) or -1 if no exact match exists.

getFST

public FST<Object> getFST()

Returns the internal automaton.