Re: [HACKERS] Function-manager redesign: second draft (long)

Jan Wieck wrote:
> 
>     Another  detail  I'm  missing  now  is  a new, really defined
>     interface for type input/output functions. The fact that they
>     are  defined  taking  one  opaque  (yepp, should be something
>     different as already discussed) argument but in fact get more
>     information from the attribute is ugly.

Can we currently return a list of the same type ?

I guess we can, as lists (or arrays) are fundamentl types in 
PostgreSQL, but I'm not sure.

I would like to define aggregate functions list() and set()

Could I define then just once and specify that they return an array 
of their input type ?

Half of that is currently done for count() - i.e. it can take any 
type of argument, but I guess the return-array-of-input-type is more 
complicated.




Also (probably off topic) how hard would it be to add another type 
of aggregate funtions tha operate on pairs of values ?

I would like to have FOR_MIN and FOR_MAX (and possibly MIN_MIN and
MAX_MAX) functions that return _another_ field from a table for a 
minimal value in one field.

-------------
Hannu