Defining What to Store in the Storage Area - Advanced SQL Engine - Teradata Database

The type of intermediate results that an aggregate UDF needs to save depends on the type of calculation that the UDF performs and whether the method wants to represent the intermediate results as a byte array or as an object.

Consider a standard deviation function STD_DEV(x) that uses the following equation:

Here is a Java class called agr_storage with fields that match the necessary intermediate values:

class agr_storage implements Serializable{
   double count;
   double x_sq;
   double x_sum;

   public agr_storage(double a, double b, double c){
      count = a;
      x_sq = b;
      x_sum = c;
   }
}

Alternatively, especially when better performance is required, the method that implements the aggregate UDF can use a ByteBuffer for the intermediate results and use the putDouble() and getDouble() methods on the ByteBuffer for the necessary intermediate values.