Aggregate Functions (UDAFs)
Aggregate functions perform an operation on a set of values and return one value. Vertica provides standard built-in aggregate functions such as AVG, MAX, and MIN. User-Defined Aggregate Functions work similarly to the built-in aggregate functions.
User-Defined Aggregate Functions:
-
Support a single input column (or set) of values and provide a single output column.
- Support RLE decompression; RLE input is decompressed before it is sent to a UDAF.
- Can be used with the GROUP BY and HAVING clauses. Only columns appearing in the GROUP BY clause can be selected.
- Cannot be used with correlated subquery.
UDAFs are available for C++ only.