public PhysicalContext getPhysicalContext() {
      return physicalContext;
    }
Iterator each tasks. If this task has a local work,create a new task for this local work, named
MapredLocalTask. then make this new generated task depends on current task's parent task, and
make current task depends on this new generated task
ql/src/java/org/apache/hadoop/hive/ql/optimizer/physical/MapJoinResolver.java