Class FSTCompletionLookup
- All Implemented Interfaces:
Accountable
Lookup API to FSTCompletion.
This adapter differs from FSTCompletion in that it attempts to discretize any
"weights" as passed from in InputIterator.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.
- See Also:
- 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 -
Field Summary
Fields inherited from class org.apache.lucene.search.suggest.Lookup
CHARSEQUENCE_COMPARATORFields inherited from interface org.apache.lucene.util.Accountable
NULL_ACCOUNTABLE -
Constructor Summary
ConstructorsConstructorDescriptionThis constructor should only be used to read a previously saved suggester.FSTCompletionLookup(Directory tempDir, String tempFileNamePrefix) This constructor prepares for creating a suggested FST using thebuild(InputIterator)method.FSTCompletionLookup(Directory tempDir, String tempFileNamePrefix, int buckets, boolean exactMatchFirst) This constructor prepares for creating a suggested FST using thebuild(InputIterator)method.FSTCompletionLookup(Directory tempDir, String tempFileNamePrefix, FSTCompletion completion, boolean exactMatchFirst) This constructor takes a pre-built automaton. -
Method Summary
Modifier and TypeMethodDescriptionvoidbuild(InputIterator iterator) Builds up a new internalLookuprepresentation based on the givenInputIterator.get(CharSequence key) Returns the bucket (weight) as a Long for the provided key if it exists, otherwise null if it does not.longgetCount()Get the number of entries the lookup was built withbooleanDiscard current lookup data and load it from a previously saved copy.lookup(CharSequence key, Set<BytesRef> contexts, boolean higherWeightsFirst, int num) Look up a key and return possible completion for this key.longbooleanstore(DataOutput output) Persist the constructed lookup data to a directory.
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Constructor Details
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FSTCompletionLookup
public FSTCompletionLookup()This constructor should only be used to read a previously saved suggester. -
FSTCompletionLookup
This constructor prepares for creating a suggested FST using thebuild(InputIterator)method. The number of weight discretization buckets is set toFSTCompletion.DEFAULT_BUCKETSand exact matches are promoted to the top of the suggestions list. -
FSTCompletionLookup
public FSTCompletionLookup(Directory tempDir, String tempFileNamePrefix, int buckets, boolean exactMatchFirst) This constructor prepares for creating a suggested FST using thebuild(InputIterator)method.- Parameters:
buckets- The number of weight discretization buckets (seeFSTCompletionfor details).exactMatchFirst- Iftrueexact 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
public FSTCompletionLookup(Directory tempDir, String tempFileNamePrefix, FSTCompletion completion, boolean exactMatchFirst) This constructor takes a pre-built automaton.- Parameters:
completion- An instance ofFSTCompletion.exactMatchFirst- Iftrueexact 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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Method Details
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build
Description copied from class:LookupBuilds up a new internalLookuprepresentation based on the givenInputIterator. The implementation might re-sort the data internally.- Specified by:
buildin classLookup- Throws:
IOException
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lookup
public List<Lookup.LookupResult> lookup(CharSequence key, Set<BytesRef> contexts, boolean higherWeightsFirst, int num) Description copied from class:LookupLook up a key and return possible completion for this key.- Specified by:
lookupin 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 matchhigherWeightsFirst- 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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get
Returns the bucket (weight) as a Long for the provided key if it exists, otherwise null if it does not. -
store
Description copied from class:LookupPersist the constructed lookup data to a directory. Optional operation.- Specified by:
storein classLookup- Parameters:
output-DataOutputto 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:LookupDiscard current lookup data and load it from a previously saved copy. Optional operation.- Specified by:
loadin classLookup- Parameters:
input- theDataInputto 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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ramBytesUsed
public long ramBytesUsed() -
getChildResources
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getCount
public long getCount()Description copied from class:LookupGet the number of entries the lookup was built with
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