DoubleValuesSource (Lucene 6.5.0 API)

java.lang.Object
- org.apache.lucene.search.DoubleValuesSource

```
public abstract class DoubleValuesSource
extends Object
```
Base class for producing DoubleValues To obtain a DoubleValues object for a leaf reader, clients should call getValues(LeafReaderContext, DoubleValues). DoubleValuesSource objects for NumericDocValues fields can be obtained by calling fromDoubleField(String), fromFloatField(String), fromIntField(String) or fromLongField(String), or from fromField(String, LongToDoubleFunction) if special long-to-double encoding is required. Scores may be used as a source for value calculations by wrapping a Scorer using fromScorer(Scorer) and passing the resulting DoubleValues to getValues(LeafReaderContext, DoubleValues). The scores can then be accessed using the SCORES DoubleValuesSource.

Field Summary

Fields
Modifier and Type	Field and Description
`static DoubleValuesSource`	`SCORES` A DoubleValuesSource that exposes a document's score If this source is used as part of a values calculation, then callers must not pass `null` as the `DoubleValues` parameter on `getValues(LeafReaderContext, DoubleValues)`

Constructor Summary

Constructors
Constructor and Description

DoubleValuesSource()

Constructors
Constructor and Description
`DoubleValuesSource()`

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`static DoubleValuesSource`	`constant(double value)` Creates a DoubleValuesSource that always returns a constant value
`static DoubleValuesSource`	`fromDoubleField(String field)` Creates a DoubleValuesSource that wraps a double-valued field
`static DoubleValuesSource`	`fromField(String field, LongToDoubleFunction decoder)` Creates a DoubleValuesSource that wraps a generic NumericDocValues field
`static DoubleValuesSource`	`fromFloatField(String field)` Creates a DoubleValuesSource that wraps a float-valued field
`static DoubleValuesSource`	`fromIntField(String field)` Creates a DoubleValuesSource that wraps an int-valued field
`static DoubleValuesSource`	`fromLongField(String field)` Creates a DoubleValuesSource that wraps a long-valued field
`static DoubleValues`	`fromScorer(Scorer scorer)` Returns a DoubleValues instance that wraps scores returned by a Scorer
`static DoubleValuesSource`	`function(DoubleValuesSource in, DoubleUnaryOperator function)` Creates a DoubleValuesSource that is a function of another DoubleValuesSource
`SortField`	`getSortField(boolean reverse)` Create a sort field based on the value of this producer
`abstract DoubleValues`	`getValues(LeafReaderContext ctx, DoubleValues scores)` Returns a `DoubleValues` instance for the passed-in LeafReaderContext and scores If scores are not needed to calculate the values (ie `returns false`, callers may safely pass `null` for the `scores` parameter.
`abstract boolean`	`needsScores()` Return true if document scores are needed to calculate values
`static DoubleValuesSource`	`scoringFunction(DoubleValuesSource in, ToDoubleBiFunction<Double,Double> function)` Creates a DoubleValuesSource that is a function of another DoubleValuesSource and a score
`LongValuesSource`	`toLongValuesSource()` Convert to a LongValuesSource by casting the double values to longs

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - SCORES
```
public static final DoubleValuesSource SCORES
```
    A DoubleValuesSource that exposes a document's score If this source is used as part of a values calculation, then callers must not pass null as the DoubleValues parameter on getValues(LeafReaderContext, DoubleValues)
- Constructor Detail
  - DoubleValuesSource
```
public DoubleValuesSource()
```
- Method Detail
  - getValues
```
public abstract DoubleValues getValues(LeafReaderContext ctx,
                                       DoubleValues scores)
                                throws IOException
```
    Returns a DoubleValues instance for the passed-in LeafReaderContext and scores If scores are not needed to calculate the values (ie returns false, callers may safely pass null for the scores parameter.
    
    Throws:
    
    IOException
  - needsScores
```
public abstract boolean needsScores()
```
    Return true if document scores are needed to calculate values
  - getSortField
```
public SortField getSortField(boolean reverse)
```
    Create a sort field based on the value of this producer
    
    Parameters:
    
    reverse - true if the sort should be decreasing
  - toLongValuesSource
```
public final LongValuesSource toLongValuesSource()
```
    Convert to a LongValuesSource by casting the double values to longs
  - fromField
```
public static DoubleValuesSource fromField(String field,
                                           LongToDoubleFunction decoder)
```
    Creates a DoubleValuesSource that wraps a generic NumericDocValues field
    
    Parameters:
    
    field - the field to wrap, must have NumericDocValues
    
    decoder - a function to convert the long-valued doc values to doubles
  - fromDoubleField
```
public static DoubleValuesSource fromDoubleField(String field)
```
    Creates a DoubleValuesSource that wraps a double-valued field
  - fromFloatField
```
public static DoubleValuesSource fromFloatField(String field)
```
    Creates a DoubleValuesSource that wraps a float-valued field
  - fromLongField
```
public static DoubleValuesSource fromLongField(String field)
```
    Creates a DoubleValuesSource that wraps a long-valued field
  - fromIntField
```
public static DoubleValuesSource fromIntField(String field)
```
    Creates a DoubleValuesSource that wraps an int-valued field
  - constant
```
public static DoubleValuesSource constant(double value)
```
    Creates a DoubleValuesSource that always returns a constant value
  - function
```
public static DoubleValuesSource function(DoubleValuesSource in,
                                          DoubleUnaryOperator function)
```
    Creates a DoubleValuesSource that is a function of another DoubleValuesSource
  - scoringFunction
```
public static DoubleValuesSource scoringFunction(DoubleValuesSource in,
                                                 ToDoubleBiFunction<Double,Double> function)
```
    Creates a DoubleValuesSource that is a function of another DoubleValuesSource and a score
    
    Parameters:
    
    in - the DoubleValuesSource to use as an input
    
    function - a function of the form (source, score) == result
  - fromScorer
```
public static DoubleValues fromScorer(Scorer scorer)
```
    Returns a DoubleValues instance that wraps scores returned by a Scorer

Class DoubleValuesSource

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

SCORES

Constructor Detail

DoubleValuesSource

Method Detail

getValues

needsScores

getSortField

toLongValuesSource

fromField

fromDoubleField

fromFloatField

fromLongField

fromIntField

constant

function

scoringFunction

fromScorer