On Fri, Jul 30, 2010 at 10:34 AM, Derrick Rice <derrick.rice@gmail.com> wrote:
> Is it possible to use the ARRAY(select ...) syntax as a substitute for
> array_agg on versions of postgresql that don't have it? (8.2) It works
> simply enough when only selecting a single column, but if I need to group by
> some other column, I'm not clear how I'd go about doing that.
>
> For example, write the following in ARRAY(select...) form.
yup...we've had array() for ages (I think -- see below).
now, you've always been able to do array aggregation in userland --
it's been in the docs as example since I can remember (see here:
http://www.postgresql.org/docs/8.2/static/xaggr.html)
The old school array_accum however is much slower than the newer
array_agg. (which in turn is just a tiny bit slower than array()
discounting grouping effects). So you _definitely_ want to use
array() if you don't require aggregate grouping features in older
postgres versions.
hm. I looked for the documentation for array(select...) to figure out
exactly when it was introduced, couldn't find it. Anyone know
if/where this is documented?
merlin