Package org.apache.druid.frame.processor

Class TournamentTree

  • public class TournamentTree
extends Object
    Tree-of-losers tournament tree used for K-way merging. The tree contains a fixed set of elements, from 0 (inclusive) to numElements (exclusive). The tree represents a tournament played amongst the elements. At all times each node of the tree contains the loser of the match at that node. The winners of the matches are not explicitly stored, except for the overall winner of the tournament, which is stored in tree[0]. When used as part of k-way merge, expected usage is call getMin() to retrieve a run number, then read an element from the run. On the next call to getMin(), the tree internally calls update() to handle the case where the min needs to change. Refer to https://en.wikipedia.org/wiki/K-way_merge_algorithm#Tournament_Tree for additional details.

    • Constructor Detail

      • TournamentTree

        public TournamentTree​(int numElements,
                      it.unimi.dsi.fastutil.ints.IntComparator comparator)
        Creates a tree with a certain number of elements.
        Parameters:
        numElements - number of elements in the tree
        comparator - comparator for the elements. Smaller elements "win".

    • Method Detail

      • getMin

        public int getMin()
        Get the current minimum element (the overall winner, i.e., the run to pull the next element from in the K-way merge).