Join bottomJoin = new Join();
BasicOperator op1 = opIt.next();
// op1.removeFromOperatorGraph();
// op1.getPrecedingOperators().clear();
// headOperator.addSucceedingOperator(op1);
op1.addSucceedingOperator(new OperatorIDTuple(bottomJoin, 0));
BasicOperator op2 = opIt.next();
// op2.removeFromOperatorGraph();
// op2.getPrecedingOperators().clear();
// headOperator.addSucceedingOperator(op2);
op2.addSucceedingOperator(new OperatorIDTuple(bottomJoin, 1));