Re: Various performance questions

Поиск
Список
Период
Сортировка
От Greg Stark
Тема Re: Various performance questions
Дата
Msg-id 877k2qy36r.fsf@stark.dyndns.tv
обсуждение исходный текст
Ответ на Re: Various performance questions  (Neil Conway <neilc@samurai.com>)
Ответы Re: Various performance questions  (Neil Conway <neilc@samurai.com>)
Список pgsql-performance
Neil Conway <neilc@samurai.com> writes:

> On Sun, 2003-10-26 at 22:49, Greg Stark wrote:
> > What version of postgres is this?. In 7.4 (and maybe 7.3?) count() uses an
> > int8 to store its count so it's not limited to 4 billion records.
> > Unfortunately int8 is somewhat inefficient as it has to be dynamically
> > allocated repeatedly.
>
> Uh, what? Why would an int8 need to be "dynamically allocated
> repeatedly"?

Perhaps I'm wrong, I'm extrapolating from a comment Tom Lane made that
profiling showed that the bulk of the cost in count() went to allocating
int8s. He commented that this could be optimized by having count() and sum()
bypass the regular api. I don't have the original message handy.

--
greg

В списке pgsql-performance по дате отправления:

Предыдущее
От: Greg Stark
Дата:
Сообщение: Re: vacuum locking
Следующее
От: Greg Stark
Дата:
Сообщение: Re: Very Poor Insert Performance