org.apache.lucene.queries.function

## Class ValueSource

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

- Direct Known Subclasses:
    BoolFunction, ConstNumberSource, DocFreqValueSource, DualFloatFunction, FieldCacheSource, LinearFloatFunction, LiteralValueSource, MaxDocValueSource, MultiFloatFunction, MultiFunction, MultiValueSource, NormValueSource, NumDocsValueSource, QueryValueSource, RangeMapFloatFunction, ReciprocalFloatFunction, ScaleFloatFunction, SingleFunction, SumTotalTermFreqValueSource, TotalTermFreqValueSource

      public abstract class ValueSource
      extends Object

  Instantiates `FunctionValues` for a particular reader.
  Often used when creating a `FunctionQuery`.

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `ValueSource()`

  - ### Method Summary

    All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `DoubleValuesSource` | `asDoubleValuesSource()` Expose this ValueSource as a DoubleValuesSource
    `LongValuesSource` | `asLongValuesSource()` Expose this ValueSource as a LongValuesSource
    `void` | `createWeight(Map 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)`
    `SortField` | `getSortField(boolean reverse)` EXPERIMENTAL: This method is subject to change.
    `abstract FunctionValues` | `getValues(Map context, LeafReaderContext readerContext)` Gets the values for this reader and the context that was previously passed to createWeight()
    `abstract int` | `hashCode()`
    `static Map` | `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 Detail

    - #### ValueSource

          public ValueSource()

  - ### Method Detail

    - #### getValues

          public abstract FunctionValues getValues(Map context,
                                                   LeafReaderContext readerContext)
                                            throws IOException

      Gets the values for this reader and the context that was previously passed to createWeight()
      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 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 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

    - #### 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

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