Package org.apache.flink.table.runtime.util.collections

Class OptimizableHashSet

java.lang.Object
org.apache.flink.table.runtime.util.collections.OptimizableHashSet
Direct Known Subclasses:
DoubleHashSet, FloatHashSet, IntHashSet, LongHashSet, ObjectHashSet, ShortHashSet
public abstract class OptimizableHashSet extends Object
A type-specific hash set with with a fast, small-footprint implementation. Refer to the implementation of fastutil.

Instances of this class use a hash table to represent a set. The table is enlarged as needed by doubling its size when new entries are created.

The difference with fastutil is that if the range of the maximum and minimum values is small or the data is dense, a Dense array will be used to greatly improve the access speed.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    protected boolean
    containsNull
    Is this set has a null key.
    protected boolean
    containsZero
    Is this set has a zero key.
    static final int
    DEFAULT_INITIAL_SIZE
    The initial default size of a hash table.
    static final float
    DEFAULT_LOAD_FACTOR
    The default load factor of a hash table.
    static final int
    DENSE_THRESHOLD
    Decide whether to convert to dense mode if it does not require more memory or could fit within L1 cache.
    protected final float
    f
    The acceptable load factor.
    protected boolean
    isDense
    Is now dense mode.
    protected int
    mask
    The mask for wrapping a position counter.
    protected int
    maxFill
    Threshold after which we rehash.
    protected int
    n
    The current table size.
    protected int
    size
    Number of entries in the set.
    protected boolean[]
    used
    Used array for dense mode.

  • Constructor Summary

    Constructors
    Constructor
    Description
    OptimizableHashSet(int expected, float f)
     

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    addNull()
    Add a null key.
    static int
    arraySize(int expected, float f)
    Returns the least power of two smaller than or equal to 230 and larger than or equal to Math.ceil( expected / f ).
    boolean
    containsNull()
    Is there a null key.
    static int
    maxFill(int n, float f)
    Returns the maximum number of entries that can be filled before rehashing.
    static long
    nextPowerOfTwo(long x)
    Return the least power of two greater than or equal to the specified value.
    abstract void
    optimize()
    Decide whether to convert to dense mode.
    protected int
    realSize()
     

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • DEFAULT_INITIAL_SIZE

      public static final int DEFAULT_INITIAL_SIZE
      The initial default size of a hash table.
      See Also:

    • DEFAULT_LOAD_FACTOR

      public static final float DEFAULT_LOAD_FACTOR
      The default load factor of a hash table.
      See Also:

    • DENSE_THRESHOLD

      public static final int DENSE_THRESHOLD
      Decide whether to convert to dense mode if it does not require more memory or could fit within L1 cache.
      See Also:

    • f

      protected final float f
      The acceptable load factor.

    • mask

      protected int mask
      The mask for wrapping a position counter.

    • n

      protected int n
      The current table size.

    • maxFill

      protected int maxFill
      Threshold after which we rehash. It must be the table size times f.

    • containsNull

      protected boolean containsNull
      Is this set has a null key.

    • containsZero

      protected boolean containsZero
      Is this set has a zero key.

    • size

      protected int size
      Number of entries in the set.

    • isDense

      protected boolean isDense
      Is now dense mode.

    • used

      protected boolean[] used
      Used array for dense mode.

  • Constructor Details

    • OptimizableHashSet

      public OptimizableHashSet(int expected, float f)

  • Method Details

    • addNull

      public void addNull()
      Add a null key.

    • containsNull

      public boolean containsNull()
      Is there a null key.

    • realSize

      protected int realSize()

    • optimize

      public abstract void optimize()
      Decide whether to convert to dense mode.

    • nextPowerOfTwo

      public static long nextPowerOfTwo(long x)
      Return the least power of two greater than or equal to the specified value.

      Note that this function will return 1 when the argument is 0.

      Parameters:
      x - a long integer smaller than or equal to 262.
      Returns:
      the least power of two greater than or equal to the specified value.

    • maxFill

      public static int maxFill(int n, float f)
      Returns the maximum number of entries that can be filled before rehashing.
      Parameters:
      n - the size of the backing array.
      f - the load factor.
      Returns:
      the maximum number of entries before rehashing.

    • arraySize

      public static int arraySize(int expected, float f)
      Returns the least power of two smaller than or equal to 230 and larger than or equal to Math.ceil( expected / f ).
      Parameters:
      expected - the expected number of elements in a hash table.
      f - the load factor.
      Returns:
      the minimum possible size for a backing array.
      Throws:
      IllegalArgumentException - if the necessary size is larger than 230.