Re: Performance of count(*)

От: Tino Wildenhain
Тема: Re: Performance of count(*)
Дата: ,
Msg-id: 4602BC84.8030101@wildenhain.de
(см: обсуждение, исходный текст)
Ответ на: Re: Performance of count(*)  ("Craig A. James")
Ответы: Re: Performance of count(*)  (Michael Stone)
Re: Performance of count(*)  ("Craig A. James")
Список: pgsql-performance

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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, )

Craig A. James schrieb:
> Tino Wildenhain wrote:
>> Craig A. James schrieb:
>> ...
>>> In our case (for a variety of reasons, but this one is critical), we
>>> actually can't use Postgres indexing at all -- we wrote an entirely
>>> separate indexing system for our data...
>>
>> ...There is no need to store or
>> maintain this information along with postgres when you can store
>> and maintain it directly in postgres as well.
>
> Whether we store our data inside or outside Postgres misses the point
> (in fact, most of our data is stored IN Postgres).  It's the code that
> actually performs the index operation that has to be external to Postgres.
>
>> On top of that, postgres has a very flexible and extensible index
>> system.
>
> You guys can correct me if I'm wrong, but the key feature that's missing
> from Postgres's flexible indexing is the ability to maintain state
> across queries.  Something like this:
>
>  select a, b, my_index_state() from foo where ...
>    offset 100 limit 10 using my_index(prev_my_index_state);
>

Yes, you are wrong :-) The technique is called "CURSOR"
if you maintain persistent connection per session
(e.g. stand allone application or clever pooling webapplication)

If its a naive web application you just store your session
in tables where you can easily maintain the scroll state
as well.

Regards
Tino


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