Class ReciprocalFloatFunction
- java.lang.Object
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- org.apache.lucene.queries.function.ValueSource
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- org.apache.lucene.queries.function.valuesource.ReciprocalFloatFunction
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public class ReciprocalFloatFunction extends ValueSource
ReciprocalFloatFunctionimplements a reciprocal function f(x) = a/(mx+b), based on the float value of a field or function as exported byValueSource.
When a and b are equal, and x>=0, this function has a maximum value of 1 that drops as x increases. Increasing the value of a and b together results in a movement of the entire function to a flatter part of the curve.These properties make this an idea function for boosting more recent documents.
Example:
recip(ms(NOW,mydatefield),3.16e-11,1,1)A multiplier of 3.16e-11 changes the units from milliseconds to years (since there are about 3.16e10 milliseconds per year). Thus, a very recent date will yield a value close to 1/(0+1) or 1, a date a year in the past will get a multiplier of about 1/(1+1) or 1/2, and date two years old will yield 1/(2+1) or 1/3.
- See Also:
FunctionQuery
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Field Summary
Fields Modifier and Type Field Description protected floataprotected floatbprotected floatmprotected ValueSourcesource
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Constructor Summary
Constructors Constructor Description ReciprocalFloatFunction(ValueSource source, float m, float a, float b)f(source) = a/(m*float(source)+b)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description voidcreateWeight(Map<Object,Object> context, IndexSearcher searcher)Implementations should propagate createWeight to sub-ValueSources which can optionally store weight info in the context.Stringdescription()description of field, used in explain()booleanequals(Object o)FunctionValuesgetValues(Map<Object,Object> context, LeafReaderContext readerContext)Gets the values for this reader and the context that was previously passed to createWeight().inthashCode()-
Methods inherited from class org.apache.lucene.queries.function.ValueSource
asDoubleValuesSource, asLongValuesSource, fromDoubleValuesSource, getSortField, newContext, toString
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Field Detail
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source
protected final ValueSource source
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m
protected final float m
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a
protected final float a
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b
protected final float b
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Constructor Detail
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ReciprocalFloatFunction
public ReciprocalFloatFunction(ValueSource source, float m, float a, float b)
f(source) = a/(m*float(source)+b)
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Method Detail
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getValues
public FunctionValues getValues(Map<Object,Object> context, LeafReaderContext readerContext) throws IOException
Description copied from class:ValueSourceGets the values for this reader and the context that was previously passed to createWeight(). The values must be consumed in a forward docID manner, and you must call this method again to iterate through the values again.- Specified by:
getValuesin classValueSource- Throws:
IOException
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createWeight
public void createWeight(Map<Object,Object> context, IndexSearcher searcher) throws IOException
Description copied from class:ValueSourceImplementations should propagate createWeight to sub-ValueSources which can optionally store weight info in the context. The context object will be passed to getValues() where this info can be retrieved.- Overrides:
createWeightin classValueSource- Throws:
IOException
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description
public String description()
Description copied from class:ValueSourcedescription of field, used in explain()- Specified by:
descriptionin classValueSource
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hashCode
public int hashCode()
- Specified by:
hashCodein classValueSource
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equals
public boolean equals(Object o)
- Specified by:
equalsin classValueSource
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