The pgsql-patches mailing list is for submitting modifications to
Postgres, not for asking these sorts of questions.
On Thu, 2007-20-09 at 06:49 +0100, sayali k wrote:
> I am keen in implementing certain additional aggregate
> functions like percentage, standard deviation etc. I
> would like to know the complexity of this and also the
> parts of the code which would have to be modified for
> the same,
stddev() already exists. Take a look at the implementation of the
existing aggregate functions, which can be found in
src/backend/utils/adt (float.c, numeric.c, etc.) There is no need to
modify the core Postgres backend code to add new aggregate functions, of
course.
I suggest doing a modicum of research first, and then asking on
pgsql-hackers if you have more specific questions about Postgres
internals.
-Neil