On 5 April 2014 04:18, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Greg Stark <stark@mit.edu> writes:
>> Well in many cases stype will just be internal for many of them. That
>> doesn't mean they're the same.
>
>> Hm, I suppose it might if they have the same sfunc.
>
>> This is actually where I started but we concluded that we needed some
>> declaration that the aggregates were actually related and would interpret
>> the state the same way and not just that it happened to use the same
>> storage format.
>
> Well, in practice you'd need to also compare the input datatype (consider
> polymorphic aggregates) and initcond. But the sfunc isn't told which
> finalfunc will be applied, so any aggregates that share the same sfunc and
> have the other conditions the same *must* have the identical transition
> data behavior. I don't see any reason to invent new syntax, and there
> are good reasons not to if we don't have to.
Definitely happy not to have additional syntax. So we can just
dynamically group the aggregates together.
-- Simon Riggs http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services
