16.20 - Saving Intermediate Results - Advanced SQL Engine - Teradata Database

Teradata Vantage™ - SQL External Routine Programming

Product
Advanced SQL Engine
Teradata Database
Release Number
16.20
Release Date
April 2020
Content Type
Programming Reference
Publication ID
B035-1147-162K
Language
English (United States)

During the AGR_INIT aggregation phase, a UDF must also save the first set of data values passed in through arguments into the intermediate aggregate storage area. The first set of data values are for the first row to aggregate for the group.

Thereafter, each time the function is called during the AGR_DETAIL aggregation phase, it must accumulate the row data passed in through arguments into the intermediate aggregate storage area for the specific group. Each group being aggregated to has a separate intermediate storage area.

The aggregation storage area is pointed to by interim1 in the FNC_Context_t function context argument.

In the standard deviation example, the x input argument is the column the standard deviation is being calculated for. For the standard deviation calculation, the function uses the value of x to calculate the following:
  • sum(X 2)
  • sum(X)

The following statements perform the necessary calculations using the column value, and then combine the results with the intermediate storage:

s1->n++;
s1->x_sq  += *x * *x;
s1->x_sum += *x;