Package org.apache.datasketches.sampling

Class 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 Detail

      • 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