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 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 Lucene.Net.Analysis.Core.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", Lucene.Net.Analysis.Core.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.

Note

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

Inheritance

object

Lookup

AnalyzingSuggester

FuzzySuggester

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.Analyzing

Assembly: Lucene.Net.Suggest.dll

Syntax

public class AnalyzingSuggester : Lookup

Constructors

AnalyzingSuggester(Analyzer)

Calls AnalyzingSuggester(analyzer, analyzer, SuggesterOptions.EXACT_FIRST | SuggesterOptions.PRESERVE_SEP, 256, -1, true)

Declaration

public AnalyzingSuggester(Analyzer analyzer)

Parameters

Type	Name	Description
Analyzer	analyzer

AnalyzingSuggester(Analyzer, Analyzer)

Calls AnalyzingSuggester(indexAnalyzer, queryAnalyzer, SuggesterOptions.EXACT_FIRST | SuggesterOptions.PRESERVE_SEP, 256, -1, true)

Declaration

public AnalyzingSuggester(Analyzer indexAnalyzer, Analyzer queryAnalyzer)

Parameters

Type	Name	Description
Analyzer	indexAnalyzer
Analyzer	queryAnalyzer

AnalyzingSuggester(Analyzer, Analyzer, SuggesterOptions, int, int, bool)

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
int	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.
int	maxGraphExpansions	Maximum number of graph paths to expand from the analyzed form. Set this to -1 for no limit.
bool	preservePositionIncrements	Whether position holes should appear in the automata

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

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)

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

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 onlyMorePopular, 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	onlyMorePopular	return only more popular results
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)

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
string	key

Returns

Type	Description
object

GetFullPrefixPaths(IList<Path<Pair>>, Automaton, FST<Pair>)

Returns all prefix paths to initialize the search.

Declaration

protected virtual IList<FSTUtil.Path<PairOutputs<Int64, BytesRef>.Pair>> GetFullPrefixPaths(IList<FSTUtil.Path<PairOutputs<Int64, BytesRef>.Pair>> prefixPaths, Automaton lookupAutomaton, FST<PairOutputs<Int64, BytesRef>.Pair> fst)

Parameters

Type	Name	Description
IList<FSTUtil.Path<PairOutputs<Int64, BytesRef>.Pair>>	prefixPaths
Automaton	lookupAutomaton
FST<PairOutputs<Int64, BytesRef>.Pair>	fst

Returns

Type	Description
IList<FSTUtil.Path<PairOutputs<Int64, BytesRef>.Pair>>

GetSizeInBytes()

Returns byte size of the underlying FST.

Declaration

public override long GetSizeInBytes()

Returns

Type	Description
long

Overrides

Lookup.GetSizeInBytes()

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.

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.