Pass extra parameter to PostgreSQL aggregate final function

Question

Is the only way to pass an extra parameter to the final function of a PostgreSQL aggregate to create a special TYPE for the state value?

e.g.:

CREATE         


        

Answer 1

You would have to rewrite the final function itself, and in that case you might as well write a set of new aggregate functions, one for each possible COMPUTE_METHOD. If the COMPUTE_METHOD is a data value or implied by a data value, then a CASE statement can be used to select the appropriate aggregate method. Alternatively, you may want to create a custom composite type with fields for accum_number and COMPUTE_METHOD, and write a single new aggregate function that uses this new data type.