Re: more support for various frame types of window functions

2009/11/9 Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk>:
>>>>>> "Heikki" == Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
>
>  Heikki> Yeah, we need the reinitialization support to handle the generic case.
>
>  Heikki> One idea is to take a copy of the state datum after each row.
>
> Some existing aggregates, notably array_agg, rely on the assumption
> that this never happens.

I'm carefully coding to keep the existing behavior that when frame
start is UNBOUNDED PRECEDING aggregate state is cached. I don't see
how the copied state will help in other frame types, but is it rather
than that? We assume the frame starting and ending boundary never goes
back.

Regards,

--
Hitoshi Harada