Class WFSTCompletionLookup
- java.lang.Object
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- org.apache.lucene.search.suggest.Lookup
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- org.apache.lucene.search.suggest.fst.WFSTCompletionLookup
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- All Implemented Interfaces:
Accountable
public class WFSTCompletionLookup extends Lookup implements Accountable
Suggester based on a weighted FST: it first traverses the prefix, then walks the n shortest paths to retrieve top-ranked suggestions.NOTE: Input weights must be between 0 and
Integer.MAX_VALUE
, any other values will be rejected.
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Nested Class Summary
Nested Classes Modifier and Type Class Description private static class
WFSTCompletionLookup.WFSTInputIterator
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Nested classes/interfaces inherited from class org.apache.lucene.search.suggest.Lookup
Lookup.LookupPriorityQueue, Lookup.LookupResult
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Field Summary
Fields Modifier and Type Field Description private long
count
Number of entries the lookup was built withprivate boolean
exactFirst
True if exact match suggestions should always be returned first.private FST<java.lang.Long>
fst
FST, weights are encoded as costs: (Integer.MAX_VALUE-weight) private Directory
tempDir
private java.lang.String
tempFileNamePrefix
(package private) static java.util.Comparator<java.lang.Long>
weightComparator
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Fields inherited from class org.apache.lucene.search.suggest.Lookup
CHARSEQUENCE_COMPARATOR
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Fields inherited from interface org.apache.lucene.util.Accountable
NULL_ACCOUNTABLE
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Constructor Summary
Constructors Constructor Description WFSTCompletionLookup(Directory tempDir, java.lang.String tempFileNamePrefix)
WFSTCompletionLookup(Directory tempDir, java.lang.String tempFileNamePrefix, boolean exactFirst)
Creates a new suggester.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description void
build(InputIterator iterator)
Builds up a new internalLookup
representation based on the givenInputIterator
.private static int
decodeWeight(long encoded)
cost -> weightprivate static int
encodeWeight(long value)
weight -> costjava.lang.Object
get(java.lang.CharSequence key)
Returns the weight associated with an input string, or null if it does not exist.java.util.Collection<Accountable>
getChildResources()
Returns nested resources of this class.long
getCount()
Get the number of entries the lookup was built withboolean
load(DataInput input)
Discard current lookup data and load it from a previously saved copy.java.util.List<Lookup.LookupResult>
lookup(java.lang.CharSequence key, java.util.Set<BytesRef> contexts, boolean onlyMorePopular, int num)
Look up a key and return possible completion for this key.private java.lang.Long
lookupPrefix(BytesRef scratch, FST.Arc<java.lang.Long> arc)
long
ramBytesUsed()
Returns byte size of the underlying FST.boolean
store(DataOutput output)
Persist the constructed lookup data to a directory.
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Field Detail
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fst
private FST<java.lang.Long> fst
FST, weights are encoded as costs: (Integer.MAX_VALUE-weight)
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exactFirst
private final boolean exactFirst
True if exact match suggestions should always be returned first.
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count
private long count
Number of entries the lookup was built with
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tempDir
private final Directory tempDir
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tempFileNamePrefix
private final java.lang.String tempFileNamePrefix
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weightComparator
static final java.util.Comparator<java.lang.Long> weightComparator
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Constructor Detail
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WFSTCompletionLookup
public WFSTCompletionLookup(Directory tempDir, java.lang.String tempFileNamePrefix)
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WFSTCompletionLookup
public WFSTCompletionLookup(Directory tempDir, java.lang.String tempFileNamePrefix, boolean exactFirst)
Creates a new suggester.- Parameters:
exactFirst
-true
if suggestions that match the prefix exactly should always be returned first, regardless of score. This has no performance impact, but could result in low-quality suggestions.
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Method Detail
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build
public void build(InputIterator iterator) throws java.io.IOException
Description copied from class:Lookup
Builds up a new internalLookup
representation based on the givenInputIterator
. The implementation might re-sort the data internally.
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store
public boolean store(DataOutput output) throws java.io.IOException
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:
java.io.IOException
- when fatal IO error occurs.
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load
public boolean load(DataInput input) throws java.io.IOException
Description copied from class:Lookup
Discard current lookup data and load it from a previously saved copy. Optional operation.
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lookup
public java.util.List<Lookup.LookupResult> lookup(java.lang.CharSequence key, java.util.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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lookupPrefix
private java.lang.Long lookupPrefix(BytesRef scratch, FST.Arc<java.lang.Long> arc) throws java.io.IOException
- Throws:
java.io.IOException
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get
public java.lang.Object get(java.lang.CharSequence key)
Returns the weight associated with an input string, or null if it does not exist.
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decodeWeight
private static int decodeWeight(long encoded)
cost -> weight
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encodeWeight
private static int encodeWeight(long value)
weight -> cost
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ramBytesUsed
public long ramBytesUsed()
Returns byte size of the underlying FST.- Specified by:
ramBytesUsed
in interfaceAccountable
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getChildResources
public java.util.Collection<Accountable> getChildResources()
Description copied from interface:Accountable
Returns nested resources of this class. The result should be a point-in-time snapshot (to avoid race conditions).- Specified by:
getChildResources
in interfaceAccountable
- See Also:
Accountables
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