automatic update or insert

Hi.

I have a little problem.

In a system of mine i need to insert records into table [tbStat], and
if the records exist i need to update them instead and increase a
column [cQuantity] for every update.

I.e. the first insert sets cQuantity to 1, and for every other run
cQuantity is increased.

Currently i have implemented this as a stored procedure in the plpgsql
language. This means that in my stored procedure i first do a select to
find out if the row exists or not, then i do a insert or update
depending if the row existed.

Unfortunately, stored procedures seems awfully slow. And i need the
application to go faster.

One solution could be to implement the stored procedure in my program
instead. I think that this will be atleast 50% faster than my stored
procedure, so that would be ok.

However, this has made me thinking. Couldn't this be done directly in
SQL?

Brgds Robert