private List<ExprNodeDesc> evaluateCastOnConstants(List<ExprNodeDesc> childExpr)
      throws HiveException {
    List<ExprNodeDesc> evaluatedChildren = new ArrayList<>();
    if (childExpr != null) {
        for (ExprNodeDesc expr : childExpr) {
          expr = this.evaluateCastOnConstants(expr);
          evaluatedChildren.add(expr);
        }
    }
    return evaluatedChildren;
  }
Handles only the special cases of cast/+ve/-ve operator on a constant.
@param exprDesc
@return The same expression if no evaluation done, else return the constant
        expression.
@throws HiveException
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/VectorizationContext.java