Class FSTCompletionLookup

An adapter from Lookup API to FSTCompletion.

This adapter differs from FSTCompletion in that it attempts to discretize any "weights" as passed from in Weight to match the number of buckets. For the rationale for bucketing, see FSTCompletion.

Note:Discretization requires an additional sorting pass.

The range of weights for bucketing/ discretization is determined by sorting the input by weight and then dividing into equal ranges. Then, scores within each range are assigned to that bucket.

Note that this means that even large differences in weights may be lost during automaton construction, but the overall distinction between "classes" of weights will be preserved regardless of the distribution of weights.

For fine-grained control over which weights are assigned to which buckets, use FSTCompletion directly or TSTLookup, for example.

Inheritance

object

Lookup

FSTCompletionLookup

Inherited Members

Lookup.CHARSEQUENCE_COMPARER

Lookup.Build(IDictionary)

Lookup.Load(Stream)

Lookup.Store(Stream)

Lookup.DoLookup(string, bool, int)

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Namespace: Lucene.Net.Search.Suggest.Fst

Assembly: Lucene.Net.Suggest.dll

Syntax

public class FSTCompletionLookup : Lookup

Constructors

FSTCompletionLookup()

This constructor prepares for creating a suggested FST using the Build(IInputEnumerator) method. The number of weight discretization buckets is set to DEFAULT_BUCKETS and exact matches are promoted to the top of the suggestions list.

Declaration

public FSTCompletionLookup()

See Also

FSTCompletion

FSTCompletionLookup(FSTCompletion, bool)

This constructor takes a pre-built automaton.

Declaration

public FSTCompletionLookup(FSTCompletion completion, bool exactMatchFirst)

Parameters

Type	Name	Description
FSTCompletion	completion	An instance of FSTCompletion.
bool	exactMatchFirst	If true exact matches are promoted to the top of the suggestions list. Otherwise they appear in the order of discretized weight and alphabetical within the bucket.

See Also

FSTCompletion

FSTCompletionLookup(int, bool)

This constructor prepares for creating a suggested FST using the Build(IInputEnumerator) method.

Declaration

public FSTCompletionLookup(int buckets, bool exactMatchFirst)

Parameters

Type	Name	Description
int	buckets	The number of weight discretization buckets (see FSTCompletion for details).
bool	exactMatchFirst	If true exact matches are promoted to the top of the suggestions list. Otherwise they appear in the order of discretized weight and alphabetical within the bucket.

See Also

FSTCompletion

Properties

Count

Get the number of entries the lookup was built with

Declaration

public override long Count { get; }

Property Value

Type	Description
long	total number of suggester entries

Overrides

Lookup.Count

See Also

FSTCompletion

Methods

Build(IInputEnumerator)

Builds up a new internal Lookup representation based on the given IInputEnumerator. The implementation might re-sort the data internally.

Declaration

public override void Build(IInputEnumerator enumerator)

Parameters

Type	Name	Description
IInputEnumerator	enumerator

Overrides

Lookup.Build(IInputEnumerator)

See Also

FSTCompletion

DoLookup(string, IEnumerable<BytesRef>, bool, int)

Look up a key and return possible completion for this key.

Declaration

public override IList<Lookup.LookupResult> DoLookup(string key, IEnumerable<BytesRef> contexts, bool higherWeightsFirst, int num)

Parameters

Type	Name	Description
string	key	lookup key. Depending on the implementation this may be a prefix, misspelling, or even infix.
IEnumerable<BytesRef>	contexts	contexts to filter the lookup by, or null if all contexts are allowed; if the suggestion contains any of the contexts, it's a match
bool	higherWeightsFirst
int	num	maximum number of results to return

Returns

Type	Description
IList<Lookup.LookupResult>	a list of possible completions, with their relative weight (e.g. popularity)

Overrides

Lookup.DoLookup(string, IEnumerable<BytesRef>, bool, int)

See Also

FSTCompletion

Get(string)

Returns the bucket (weight) as a Nullable{long} for the provided key if it exists, otherwise null if it does not.

Declaration

public virtual long? Get(string key)

Parameters

Type	Name	Description
string	key

Returns

Type	Description
long?

See Also

FSTCompletion

GetSizeInBytes()

Get the size of the underlying lookup implementation in memory

Declaration

public override long GetSizeInBytes()

Returns

Type	Description
long	ram size of the lookup implementation in bytes

Overrides

Lookup.GetSizeInBytes()

See Also

FSTCompletion

Load(DataInput)

Discard current lookup data and load it from a previously saved copy. Optional operation.

Declaration

public override bool Load(DataInput input)

Parameters

Type	Name	Description
DataInput	input	the Lucene.Net.Store.DataInput to load the lookup data.

Returns

Type	Description
bool	true if completed successfully, false if unsuccessful or not supported.

Overrides

Lookup.Load(DataInput)

Exceptions

Type	Condition
IOException	when fatal IO error occurs.

See Also

FSTCompletion

Store(DataOutput)

Persist the constructed lookup data to a directory. Optional operation.

Declaration

public override bool Store(DataOutput output)

Parameters

Type	Name	Description
DataOutput	output	Lucene.Net.Store.DataOutput to write the data to.

Returns

Type	Description
bool	true if successful, false if unsuccessful or not supported.

Overrides

Lookup.Store(DataOutput)

Exceptions

Type	Condition
IOException	when fatal IO error occurs.

See Also

FSTCompletion

See Also

FSTCompletion