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
System.Object
Lookup
FSTCompletionLookup
Inherited Members
System.Object.Equals(System.Object)
System.Object.Equals(System.Object, System.Object)
System.Object.GetHashCode()
System.Object.GetType()
System.Object.MemberwiseClone()
System.Object.ReferenceEquals(System.Object, System.Object)
System.Object.ToString()
Namespace: Lucene.Net.Search.Suggest.Fst
Assembly: Lucene.Net.Suggest.dll
Syntax
public class FSTCompletionLookup : Lookup

Constructors

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FSTCompletionLookup()

This constructor prepares for creating a suggested FST using the Build(IInputIterator) 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()
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FSTCompletionLookup(FSTCompletion, Boolean)

This constructor takes a pre-built automaton.

Declaration
public FSTCompletionLookup(FSTCompletion completion, bool exactMatchFirst)
Parameters
Type Name Description
FSTCompletion completion

An instance of FSTCompletion.

System.Boolean 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.

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FSTCompletionLookup(Int32, Boolean)

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

Declaration
public FSTCompletionLookup(int buckets, bool exactMatchFirst)
Parameters
Type Name Description
System.Int32 buckets

The number of weight discretization buckets (see FSTCompletion for details).
System.Boolean 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.

Properties

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Count

Declaration
public override long Count { get; }
Property Value
Type Description
System.Int64
Overrides

Methods

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Build(IInputIterator)

Declaration
public override void Build(IInputIterator iterator)
Parameters
Type Name Description
IInputIterator iterator
Overrides
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DoLookup(String, IEnumerable<BytesRef>, Boolean, Int32)

Declaration
public override IList<Lookup.LookupResult> DoLookup(string key, IEnumerable<BytesRef> contexts, bool higherWeightsFirst, int num)
Parameters
Type Name Description
System.String key
System.Collections.Generic.IEnumerable<BytesRef> contexts
System.Boolean higherWeightsFirst
System.Int32 num
Returns
Type Description
System.Collections.Generic.IList<Lookup.LookupResult>
Overrides
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Get(String)

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

Declaration
public virtual object Get(string key)
Parameters
Type Name Description
System.String key
Returns
Type Description
System.Object
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GetSizeInBytes()

Declaration
public override long GetSizeInBytes()
Returns
Type Description
System.Int64
Overrides
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Load(DataInput)

Declaration
public override bool Load(DataInput input)
Parameters
Type Name Description
DataInput input
Returns
Type Description
System.Boolean
Overrides
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Store(DataOutput)

Declaration
public override bool Store(DataOutput output)
Parameters
Type Name Description
DataOutput output
Returns
Type Description
System.Boolean
Overrides

See Also