Package org.apache.lucene.queries.function

# Class ValueSource

java.lang.Object
org.apache.lucene.queries.function.ValueSource

Direct Known Subclasses:
  `BoolFunction`, `ByteKnnVectorFieldSource`, `ConstKnnByteVectorValueSource`, `ConstKnnFloatValueSource`, `ConstNumberSource`, `DocFreqValueSource`, `DualFloatFunction`, `FieldCacheSource`, `FloatKnnVectorFieldSource`, `LinearFloatFunction`, `LiteralValueSource`, `MaxDocValueSource`, `MultiFloatFunction`, `MultiFunction`, `MultiValueSource`, `NormValueSource`, `NumDocsValueSource`, `QueryValueSource`, `RangeMapFloatFunction`, `ReciprocalFloatFunction`, `ScaleFloatFunction`, `SingleFunction`, `SumTotalTermFreqValueSource`, `TotalTermFreqValueSource`, `VectorSimilarityFunction`

public abstract class ValueSource extends Object
Instantiates `FunctionValues` for a particular reader.
Often used when creating a `FunctionQuery`.

## Constructor Summary

Constructors
Constructor
Description
`ValueSource()`

## Method Summary

Modifier and Type
Method
Description
`DoubleValuesSource`
`asDoubleValuesSource()`
Expose this ValueSource as a DoubleValuesSource
`LongValuesSource`
`asLongValuesSource()`
Expose this ValueSource as a LongValuesSource
`void`
`createWeight(Map<Object,Object> context, IndexSearcher searcher)`
Implementations should propagate createWeight to sub-ValueSources which can optionally store weight info in the context.
`abstract String`
`description()`
description of field, used in explain()
`abstract boolean`
`equals(Object o)`
`static ValueSource`
`fromDoubleValuesSource(DoubleValuesSource in)`
`SortField`
`getSortField(boolean reverse)`
EXPERIMENTAL: This method is subject to change.
`abstract FunctionValues`
`getValues(Map<Object,Object> context, LeafReaderContext readerContext)`
Gets the values for this reader and the context that was previously passed to createWeight().
`abstract int`
`hashCode()`
`static Map<Object,Object>`
`newContext(IndexSearcher searcher)`
Returns a new non-threadsafe context map.
`String`
`toString()`

### Methods inherited from class java.lang.Object

`clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

## Constructor Details

### ValueSource

public ValueSource()

## Method Details

### getValues

public abstract FunctionValues getValues(Map<Object,Object> context, LeafReaderContext readerContext) throws IOException
Gets 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.

Throws:
  `IOException`

### equals

public abstract boolean equals(Object o)

Overrides:
  `equals` in class `Object`

### hashCode

public abstract int hashCode()

Overrides:
  `hashCode` in class `Object`

### description

public abstract String description()
description of field, used in explain()

### toString

public String toString()

Overrides:
  `toString` in class `Object`

### createWeight

public void createWeight(Map<Object,Object> context, IndexSearcher searcher) throws IOException
Implementations 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.

Throws:
  `IOException`

### newContext

public static Map<Object,Object> newContext(IndexSearcher searcher)
Returns a new non-threadsafe context map.

### asLongValuesSource

public LongValuesSource asLongValuesSource()
Expose this ValueSource as a LongValuesSource

### asDoubleValuesSource

public DoubleValuesSource asDoubleValuesSource()
Expose this ValueSource as a DoubleValuesSource

### fromDoubleValuesSource

public static ValueSource fromDoubleValuesSource(DoubleValuesSource in)

### getSortField

public SortField getSortField(boolean reverse)
EXPERIMENTAL: This method is subject to change.

Get the SortField for this ValueSource. Uses the `getValues(java.util.Map, org.apache.lucene.index.LeafReaderContext)` to populate the SortField.

Parameters:
  `reverse` - true if this is a reverse sort.
Returns:
  The `SortField` for the ValueSource