Class AnalyzingSuggester

Suggester that first analyzes the surface form, adds the analyzed form to a weighted FST, and then does the same thing at lookup time. This means lookup is based on the analyzed form while suggestions are still the surface form(s).

This can result in powerful suggester functionality. For example, if you use an analyzer removing stop words, then the partial text "ghost chr..." could see the suggestion "The Ghost of Christmas Past". Note that position increments MUST NOT be preserved for this example to work, so you should call the constructor with Lucene.Net.Search.Suggest.Analyzing.AnalyzingSuggester.preservePositionIncrements parameter set to false

If SynonymFilter is used to map wifi and wireless network to hotspot then the partial text "wirele..." could suggest "wifi router". Token normalization like stemmers, accent removal, etc., would allow suggestions to ignore such variations.

When two matching suggestions have the same weight, they are tie-broken by the analyzed form. If their analyzed form is the same then the order is undefined.

There are some limitations:

  1. A lookup from a query like "net" in English won't be any different than "net " (ie, user added a trailing space) because analyzers don't reflect when they've seen a token separator and when they haven't.
  2. If you're using StopFilter, and the user will type "fast apple", but so far all they've typed is "fast a", again because the analyzer doesn't convey whether it's seen a token separator after the "a", StopFilter will remove that "a" causing far more matches than you'd expect.
  3. Lookups with the empty string return no results instead of all results.
@lucene.experimental

Inheritance
System.Object
Lookup
AnalyzingSuggester
FuzzySuggester
Inherited Members
Namespace: Lucene.Net.Search.Suggest.Analyzing
Assembly: Lucene.Net.Suggest.dll
Syntax
public class AnalyzingSuggester : Lookup

Constructors

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AnalyzingSuggester(Analyzer)

Calls AnalyzingSuggester(Analyzer, Analyzer, SuggesterOptions, Int32, Int32, Boolean)

Declaration
public AnalyzingSuggester(Analyzer analyzer)
Parameters
Type Name Description
Analyzer analyzer
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AnalyzingSuggester(Analyzer, Analyzer)

Calls AnalyzingSuggester(Analyzer, Analyzer, SuggesterOptions, Int32, Int32, Boolean)

Declaration
public AnalyzingSuggester(Analyzer indexAnalyzer, Analyzer queryAnalyzer)
Parameters
Type Name Description
Analyzer indexAnalyzer
Analyzer queryAnalyzer
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AnalyzingSuggester(Analyzer, Analyzer, SuggesterOptions, Int32, Int32, Boolean)

Creates a new suggester.

Declaration
public AnalyzingSuggester(Analyzer indexAnalyzer, Analyzer queryAnalyzer, SuggesterOptions options, int maxSurfaceFormsPerAnalyzedForm, int maxGraphExpansions, bool preservePositionIncrements)
Parameters
Type Name Description
Analyzer indexAnalyzer

Analyzer that will be used for analyzing suggestions while building the index.

Analyzer queryAnalyzer

Analyzer that will be used for analyzing query text during lookup

SuggesterOptions options

see EXACT_FIRST, PRESERVE_SEP

System.Int32 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.

System.Int32 maxGraphExpansions

Maximum number of graph paths to expand from the analyzed form. Set this to -1 for no limit.

System.Boolean preservePositionIncrements

Whether position holes should appear in the automata

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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ConvertAutomaton(Automaton)

Used by subclass to change the lookup automaton, if necessary.

Declaration
protected virtual Automaton ConvertAutomaton(Automaton a)
Parameters
Type Name Description
Automaton a
Returns
Type Description
Automaton
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DoLookup(String, IEnumerable<BytesRef>, Boolean, Int32)

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

Returns the weight associated with an input string, or null if it does not exist.

Declaration
public virtual object Get(string key)
Parameters
Type Name Description
System.String key
Returns
Type Description
System.Object
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GetFullPrefixPaths(IList<FSTUtil.Path<PairOutputs<Nullable<Int64>, BytesRef>.Pair>>, Automaton, FST<PairOutputs<Nullable<Int64>, BytesRef>.Pair>)

Returns all prefix paths to initialize the search.

Declaration
protected virtual IList<FSTUtil.Path<PairOutputs<long?, BytesRef>.Pair>> GetFullPrefixPaths(IList<FSTUtil.Path<PairOutputs<long?, BytesRef>.Pair>> prefixPaths, Automaton lookupAutomaton, FST<PairOutputs<long?, BytesRef>.Pair> fst)
Parameters
Type Name Description
IList<FSTUtil.Path<PairOutputs.Pair<>>> prefixPaths
Automaton lookupAutomaton
FST<PairOutputs.Pair<>> fst
Returns
Type Description
IList<FSTUtil.Path<PairOutputs.Pair<>>>
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GetSizeInBytes()

Returns byte size of the underlying FST.

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