Re: So, is COUNT(*) fast now?

Поиск
Список
Период
Сортировка
От Tom Lane
Тема Re: So, is COUNT(*) fast now?
Дата
Msg-id 29572.1319222011@sss.pgh.pa.us
обсуждение исходный текст
Ответ на Re: So, is COUNT(*) fast now?  (Robert Haas <robertmhaas@gmail.com>)
Ответы Re: So, is COUNT(*) fast now?
Список pgsql-hackers
Robert Haas <robertmhaas@gmail.com> writes:
> On Fri, Oct 21, 2011 at 2:08 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> What this test case proves is that btree's overhead per index
>> tuple touched is significantly more than the cost of the fastest path
>> through HeapTupleSatisfiesMVCC, which I don't find surprising
>> considering how much sweat has been expended on that code path over the
>> years.

> I think HeapTupleSatisfiesMVCC is probably being skipped anyway in
> this case, since all the heap pages should be PD_ALL_VISIBLE.

Proves my point ;-) ... you're comparing a code path that's been beat on
for *years* with one that just got written.
        regards, tom lane


В списке pgsql-hackers по дате отправления:

Предыдущее
От: Tom Lane
Дата:
Сообщение: Re: Synchronized snapshots versus multiple databases
Следующее
От: Pavel Stehule
Дата:
Сообщение: Re: psql command for bytea output