Re: Performance of count(*)

От: Michael Fuhr
Тема: Re: Performance of count(*)
Дата: ,
Msg-id: 20070322143713.GA34905@winnie.fuhr.org
(см: обсуждение, исходный текст)
Ответ на: Re: Performance of count(*)  (Andreas Kostyrka)
Список: pgsql-performance

Скрыть дерево обсуждения

Performance of count(*)  (Andreas Tille, )
 Re: Performance of count(*)  (Andreas Kostyrka, )
  Re: Performance of count(*)  (Andreas Tille, )
   Re: Performance of count(*)  (Andreas Kostyrka, )
    Re: Performance of count(*)  (Michael Fuhr, )
    Re: Performance of count(*)  (Carlos Moreno, )
   Re: Performance of count(*)  ("Luke Lonergan", )
 Re: Performance of count(*)  (Albert Cervera Areny, )
  Re: Performance of count(*)  (, )
   Re: Performance of count(*)  (Bill Moran, )
   Re: Performance of count(*)  (Mario Weilguni, )
   Re: Performance of count(*)  (Michael Stone, )
    Re: Performance of count(*)  (, )
    Re: Performance of count(*)  ("Craig A. James", )
     Re: Performance of count(*)  (Tino Wildenhain, )
      Re: Performance of count(*)  ("Craig A. James", )
       Re: Performance of count(*)  (Tino Wildenhain, )
        Re: Performance of count(*)  (Michael Stone, )
         Re: Performance of count(*)  ("Merlin Moncure", )
          Re: Performance of count(*)  (Michael Stone, )
          Re: Performance of count(*)  (Tino Wildenhain, )
          Re: Performance of count(*)  (Michael Stone, )
          Re: Performance of count(*)  (Michael Stone, )
         Re: Performance of count(*)  (Tino Wildenhain, )
          Re: Performance of count(*)  (Michael Stone, )
           Re: Performance of count(*)  (Tino Wildenhain, )
        Re: Performance of count(*)  ("Craig A. James", )
         Re: Performance of count(*)  (Tino Wildenhain, )
       Re: Performance of count(*)  (Steve Atkins, )
        Re: Performance of count(*)  ("Craig A. James", )
         Re: Performance of count(*)  (Tom Lane, )
          Re: Performance of count(*)  ("Craig A. James", )
           Re: Performance of count(*)  (Tom Lane, )
        Re: Performance of count(*)  (Guido Neitzer, )
         Re: Performance of count(*)  (Steve Atkins, )
     Re: Performance of count(*)  (Brian Hurt, )
      Re: Performance of count(*)  ("Craig A. James", )
 Re: Performance of count(*)  (, )
 Re: Performance of count(*)  ("Merlin Moncure", )
  Re: Performance of count(*)  ("Jonah H. Harris", )
   Re: Performance of count(*)  (Mario Weilguni, )
    Re: Performance of count(*)  (Andreas Kostyrka, )
     Re: Performance of count(*)  (Mario Weilguni, )
  Re: Performance of count(*)  (Michael Stone, )

On Thu, Mar 22, 2007 at 01:29:46PM +0100, Andreas Kostyrka wrote:
> * Andreas Tille <> [070322 13:24]:
> > Well, to be honest I'm not really interested in the performance of
> > count(*).  I was just discussing general performance issues on the
> > phone line and when my colleague asked me about the size of the
> > database he just wonderd why this takes so long for a job his
> > MS-SQL server is much faster.  So in principle I was just asking
> > a first question that is easy to ask.  Perhaps I come up with
> > more difficult optimisation questions.
>
> Simple. MSSQL is optimized for this case, and uses "older"
> datastructures. PG uses a MVCC storage, which is not optimized for
> this usecase. It's quite fast for different kinds of queries.

Ask about performing concurrent selects, inserts, updates, and
deletes in SQL Server and about the implications on ACID of locking
hints such as NOLOCK.  Then consider how MVCC handles concurrency
without blocking or the need for dirty reads.

--
Michael Fuhr


В списке pgsql-performance по дате сообщения:

От: Tino Wildenhain
Дата:
Сообщение: Re: Performance of count(*)
От: Michael Stone
Дата:
Сообщение: Re: Performance of count(*)