public class CorrelationOptimizer
Implementation of Correlation Optimizer. This optimizer is based on
the paper "YSmart: Yet Another SQL-to-MapReduce Translator"
(Rubao Lee, Tian Luo, Yin Huai, Fusheng Wang, Yongqiang He, and Xiaodong Zhang)
Correlation Optimizer detects if ReduceSinkOperators share same keys.
Then, it will transform the query plan tree (operator tree) by exploiting
detected correlations. For details, see the original paper of YSmart.
Test queries associated with this optimizer are correlationoptimizer1.q to