children1.add(constDesc);
greaterExprDesc.setChildren(children1);
ExprNodeGenericFuncDesc isNullExpr = new ExprNodeGenericFuncDesc();
isNullExpr.setTypeInfo(TypeInfoFactory.booleanTypeInfo);
GenericUDFOPNull isNullUdf = new GenericUDFOPNull();
isNullExpr.setGenericUDF(isNullUdf);
List<ExprNodeDesc> childOfIsNull = new ArrayList<ExprNodeDesc>();
childOfIsNull.add(greaterExprDesc);
isNullExpr.setChildren(childOfIsNull);