Package org.apache.datasketches.sampling

Class VarOptItemsUnion<T>

java.lang.Object
org.apache.datasketches.sampling.VarOptItemsUnion<T>
Type Parameters:
T - Type of items
public final class VarOptItemsUnion<T> extends Object
Provides a unioning operation over varopt sketches. This union allows the sample size k to float, possibly increasing or decreasing as warranted by the available data.
Author:
Jon Malkin, Kevin Lang

  • Method Details

    • newInstance

      public static <T> VarOptItemsUnion<T> newInstance(int maxK)
      Creates an empty Union with a maximum capacity of size k.
      Type Parameters:
      T - The type of item this union contains
      Parameters:
      maxK - The maximum allowed capacity of the unioned result
      Returns:
      A new VarOptItemsUnion

    • heapify

      public static <T> VarOptItemsUnion<T> heapify(org.apache.datasketches.memory.Memory srcMem, ArrayOfItemsSerDe<T> serDe)
      Instantiates a Union from Memory
      Type Parameters:
      T - The type of item this sketch contains
      Parameters:
      srcMem - Memory object containing a serialized union
      serDe - An instance of ArrayOfItemsSerDe
      Returns:
      A VarOptItemsUnion created from the provided Memory

    • update

      public void update(VarOptItemsSketch<T> sketchIn)
      Union the given sketch.

      This method can be repeatedly called.

      Parameters:
      sketchIn - The sketch to be merged

    • update

      public void update(org.apache.datasketches.memory.Memory mem, ArrayOfItemsSerDe<T> serDe)
      Union the given Memory image of the sketch.

      This method can be repeatedly called.

      Parameters:
      mem - Memory image of sketch to be merged
      serDe - An instance of ArrayOfItemsSerDe

    • update

      public void update(ReservoirItemsSketch<T> reservoirIn)
      Union a reservoir sketch. The reservoir sample is treated as if all items were added with a weight of 1.0.
      Parameters:
      reservoirIn - The reservoir sketch to be merged

    • getResult

      public VarOptItemsSketch<T> getResult()
      Gets the varopt sketch resulting from the union of any input sketches.
      Returns:
      A varopt sketch

    • reset

      public void reset()
      Resets this sketch to the empty state, but retains the original value of max k.

    • toString

      public String toString()
      Returns a human-readable summary of the sketch, without items.
      Overrides:
      toString in class Object
      Returns:
      A string version of the sketch summary

    • toByteArray

      public byte[] toByteArray(ArrayOfItemsSerDe<T> serDe)
      Returns a byte array representation of this union
      Parameters:
      serDe - An instance of ArrayOfItemsSerDe
      Returns:
      a byte array representation of this union

    • toByteArray

      public byte[] toByteArray(ArrayOfItemsSerDe<T> serDe, Class<?> clazz)
      Returns a byte array representation of this union. This method should be used when the array elements are subclasses of a common base class.
      Parameters:
      serDe - An instance of ArrayOfItemsSerDe
      clazz - A class to which the items are cast before serialization
      Returns:
      a byte array representation of this union