Package org.apache.druid.query.groupby.epinephelinae.collection

Class HashTableUtils

java.lang.Object
org.apache.druid.query.groupby.epinephelinae.collection.HashTableUtils
public class HashTableUtils extends Object

  • Method Summary

    Modifier and Type
    Method
    Description
    static int
    hashMemory(org.apache.datasketches.memory.Memory memory, long position, int length)
    Compute a simple, fast hash code of some memory range.
    static boolean
    memoryEquals(org.apache.datasketches.memory.Memory memory1, long offset1, org.apache.datasketches.memory.Memory memory2, long offset2, int length)
    Compare two memory ranges for equality.
    static int
    previousPowerOfTwo(int n)
    Computes the previous power of two less than or equal to a given "n".

    Methods inherited from class java.lang.Object

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

  • Method Details

    • previousPowerOfTwo

      public static int previousPowerOfTwo(int n)
      Computes the previous power of two less than or equal to a given "n". The integer should be between 1 (inclusive) and Integer.MAX_VALUE for best results. Other parameters will return Integer.MIN_VALUE.

    • hashMemory

      public static int hashMemory(org.apache.datasketches.memory.Memory memory, long position, int length)
      Compute a simple, fast hash code of some memory range.
      Parameters:
      memory - a region of memory
      position - position within the memory region
      length - length of memory to hash, starting at the position

    • memoryEquals

      public static boolean memoryEquals(org.apache.datasketches.memory.Memory memory1, long offset1, org.apache.datasketches.memory.Memory memory2, long offset2, int length)
      Compare two memory ranges for equality. The purpose of this function is to be faster than BaseState.equalTo(long, java.lang.Object, long, long) for the small memory ranges that typically comprise keys in hash tables. As of this writing, it is. See "MemoryBenchmark" in the druid-benchmarks module for performance evaluation code.
      Parameters:
      memory1 - a region of memory
      offset1 - position within the first memory region
      memory2 - another region of memory
      offset2 - position within the second memory region
      length - length of memory to compare, starting at the positions