Re: more support for various frame types of window functions

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От Hitoshi Harada
Тема Re: more support for various frame types of window functions
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Msg-id e08cc0400911090612v1aaea42ch69f28475793228ef@mail.gmail.com
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Ответ на Re: more support for various frame types of window functions  (Andrew Gierth <andrew@tao11.riddles.org.uk>)
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2009/11/9 Andrew Gierth <andrew@tao11.riddles.org.uk>:
>>>>>> "Heikki" == Heikki Linnakangas <heikki.linnakangas@enterprisedb.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


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