Class ReciprocalFloatFunction
java.lang.Object
org.apache.lucene.queries.function.ValueSource
org.apache.lucene.queries.function.valuesource.ReciprocalFloatFunction
ReciprocalFloatFunction implements a reciprocal function f(x) = a/(mx+b), based on
the float value of a field or function as exported by ValueSource. 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.
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Field Summary
FieldsModifier and TypeFieldDescriptionprotected final floatprotected final floatprotected final floatprotected final ValueSource -
Constructor Summary
ConstructorsConstructorDescriptionReciprocalFloatFunction(ValueSource source, float m, float a, float b) f(source) = a/(m*float(source)+b) -
Method Summary
Modifier and TypeMethodDescriptionvoidcreateWeight(Map<Object, Object> context, IndexSearcher searcher) Implementations should propagate createWeight to sub-ValueSources which can optionally store weight info in the context.description of field, used in explain()booleangetValues(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 Details
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source
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m
protected final float m -
a
protected final float a -
b
protected final float b
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Constructor Details
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ReciprocalFloatFunction
f(source) = a/(m*float(source)+b)
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Method Details
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getValues
public FunctionValues getValues(Map<Object, Object> context, LeafReaderContext readerContext) throws IOExceptionDescription 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
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
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
- Specified by:
equalsin classValueSource
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