Class AnalyzingSuggester
- All Implemented Interfaces:
Accountable
- Direct Known Subclasses:
FuzzySuggester
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:
- 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.
- 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. - Lookups with the empty string return no results instead of all results.
- WARNING: This API is experimental and might change in incompatible ways in the next release.
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Nested Class Summary
Nested classes/interfaces inherited from class org.apache.lucene.search.suggest.Lookup
Lookup.LookupPriorityQueue, Lookup.LookupResult
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Field Summary
Modifier and TypeFieldDescriptionstatic final int
Include this flag in the options parameter toAnalyzingSuggester(Directory,String,Analyzer,Analyzer,int,int,int,boolean)
to always return the exact match first, regardless of score.static final int
Include this flag in the options parameter toAnalyzingSuggester(Directory,String,Analyzer,Analyzer,int,int,int,boolean)
to preserve token separators when matching.Fields inherited from class org.apache.lucene.search.suggest.Lookup
CHARSEQUENCE_COMPARATOR
Fields inherited from interface org.apache.lucene.util.Accountable
NULL_ACCOUNTABLE
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Constructor Summary
ConstructorDescriptionAnalyzingSuggester
(Directory tempDir, String tempFileNamePrefix, Analyzer analyzer) AnalyzingSuggester
(Directory tempDir, String tempFileNamePrefix, Analyzer indexAnalyzer, Analyzer queryAnalyzer) AnalyzingSuggester
(Directory tempDir, String tempFileNamePrefix, Analyzer indexAnalyzer, Analyzer queryAnalyzer, int options, int maxSurfaceFormsPerAnalyzedForm, int maxGraphExpansions, boolean preservePositionIncrements) Creates a new suggester. -
Method Summary
Modifier and TypeMethodDescriptionvoid
build
(InputIterator iterator) Builds up a new internalLookup
representation based on the givenInputIterator
.protected Automaton
Used by subclass to change the lookup automaton, if necessary.get
(CharSequence key) Returns the weight associated with an input string, or null if it does not exist.long
getCount()
Get the number of entries the lookup was built withprotected List<FSTUtil.Path<PairOutputs.Pair<Long,
BytesRef>>> getFullPrefixPaths
(List<FSTUtil.Path<PairOutputs.Pair<Long, BytesRef>>> prefixPaths, Automaton lookupAutomaton, FST<PairOutputs.Pair<Long, BytesRef>> fst) Returns all prefix paths to initialize the search.boolean
Discard current lookup data and load it from a previously saved copy.lookup
(CharSequence key, Set<BytesRef> contexts, boolean onlyMorePopular, int num) Look up a key and return possible completion for this key.long
Returns byte size of the underlying FST.boolean
store
(DataOutput output) Persist the constructed lookup data to a directory.
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Field Details
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EXACT_FIRST
public static final int EXACT_FIRSTInclude this flag in the options parameter toAnalyzingSuggester(Directory,String,Analyzer,Analyzer,int,int,int,boolean)
to always return the exact match first, regardless of score. This has no performance impact but could result in low-quality suggestions.- See Also:
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PRESERVE_SEP
public static final int PRESERVE_SEPInclude this flag in the options parameter toAnalyzingSuggester(Directory,String,Analyzer,Analyzer,int,int,int,boolean)
to preserve token separators when matching.- See Also:
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Constructor Details
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AnalyzingSuggester
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AnalyzingSuggester
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AnalyzingSuggester
public AnalyzingSuggester(Directory tempDir, String tempFileNamePrefix, Analyzer indexAnalyzer, Analyzer queryAnalyzer, int options, int maxSurfaceFormsPerAnalyzedForm, int maxGraphExpansions, boolean preservePositionIncrements) Creates a new suggester.- Parameters:
indexAnalyzer
- Analyzer that will be used for analyzing suggestions while building the index.queryAnalyzer
- Analyzer that will be used for analyzing query text during lookupoptions
- seeEXACT_FIRST
,PRESERVE_SEP
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.maxGraphExpansions
- Maximum number of graph paths to expand from the analyzed form. Set this to -1 for no limit.preservePositionIncrements
- Whether position holes should appear in the automata
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Method Details
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ramBytesUsed
public long ramBytesUsed()Returns byte size of the underlying FST. -
getChildResources
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convertAutomaton
Used by subclass to change the lookup automaton, if necessary. -
build
Description copied from class:Lookup
Builds up a new internalLookup
representation based on the givenInputIterator
. The implementation might re-sort the data internally.- Specified by:
build
in classLookup
- Throws:
IOException
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store
Description copied from class:Lookup
Persist the constructed lookup data to a directory. Optional operation.- Specified by:
store
in classLookup
- Parameters:
output
-DataOutput
to write the data to.- Returns:
- true if successful, false if unsuccessful or not supported.
- Throws:
IOException
- when fatal IO error occurs.
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load
Description copied from class:Lookup
Discard current lookup data and load it from a previously saved copy. Optional operation.- Specified by:
load
in classLookup
- Parameters:
input
- theDataInput
to load the lookup data.- Returns:
- true if completed successfully, false if unsuccessful or not supported.
- Throws:
IOException
- when fatal IO error occurs.
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lookup
public List<Lookup.LookupResult> lookup(CharSequence key, Set<BytesRef> contexts, boolean onlyMorePopular, int num) Description copied from class:Lookup
Look up a key and return possible completion for this key.- Specified by:
lookup
in classLookup
- Parameters:
key
- lookup key. Depending on the implementation this may be a prefix, misspelling, or even infix.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 matchonlyMorePopular
- return only more popular resultsnum
- maximum number of results to return- Returns:
- a list of possible completions, with their relative weight (e.g. popularity)
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getCount
public long getCount()Description copied from class:Lookup
Get the number of entries the lookup was built with -
getFullPrefixPaths
protected List<FSTUtil.Path<PairOutputs.Pair<Long,BytesRef>>> getFullPrefixPaths(List<FSTUtil.Path<PairOutputs.Pair<Long, BytesRef>>> prefixPaths, Automaton lookupAutomaton, FST<PairOutputs.Pair<Long, throws IOExceptionBytesRef>> fst) Returns all prefix paths to initialize the search.- Throws:
IOException
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get
Returns the weight associated with an input string, or null if it does not exist.
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