Tom, Richard,
Thanks for the advice, guys! This being Postgres, I *knew* there would
be other options.
> > create aggregate catenate(sfunc1=textcat, basetype=text,
> stype1=text, initcond1='');
>
> > Then group by client and catenate(firstname || ' ' || lastname)
>
> With a custom aggregate you could make the aggregate function
> responsible for handling the ordering of contacts:
>
> select client, contactlist(contact) from table group by client;
>
> If I were doing this, I'd make the aggregate state variable be "array
> of
> text", and have the transition function simply append each new value
> to
> the array. (Or, if you're willing to assume that no newlines appear
> in
> the contact names, the state variable can be plain text and can list
> the
> contacts one per line.) Then the finalization function would sort
> the
> array elements and concatenate them with inserted commas. These two
> functions would be pretty trivial to write in pltcl or plperl, either
> of which are the tool of first choice for string-bashing problems.
Hmmm... neither of these options sounds like it would be faster and
more scalable than a simple PL/pgSQL function which loops throught the
names and appends them to a string. Perhaps for Phase II of our project
I'll be able to afford somebody to write a custom aggregate in C.
-Josh Berkus
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