Re: count * performance issue

Поиск
Список
Период
Сортировка
От Bill Moran
Тема Re: count * performance issue
Дата
Msg-id 20080311093537.a60e2e3d.wmoran@collaborativefusion.com
обсуждение исходный текст
Ответ на Re: count * performance issue  ("Robins Tharakan" <tharakan@gmail.com>)
Ответы Re: count * performance issue  (Matthew <matthew@flymine.org>)
Список pgsql-performance
In response to "Robins Tharakan" <tharakan@gmail.com>:

> Hi,
>
> I have been reading this conversation for a few days now and I just wanted
> to ask this. From the release notes, one of the new additions in 8.3 is
> (Allow col IS NULL to use an index (Teodor)).
>
> Sorry, if I am missing something here, but shouldn't something like this
> allow us to get a (fast) accurate count ?
>
> SELECT COUNT(*) from table WHERE indexed_field IS NULL
> +
> SELECT COUNT(*) from table WHERE indexed_field IS NOT NULL

For certain, qualified definitions of "fast", sure.

--
Bill Moran
Collaborative Fusion Inc.
http://people.collaborativefusion.com/~wmoran/

wmoran@collaborativefusion.com
Phone: 412-422-3463x4023

****************************************************************
IMPORTANT: This message contains confidential information and is
intended only for the individual named. If the reader of this
message is not an intended recipient (or the individual
responsible for the delivery of this message to an intended
recipient), please be advised that any re-use, dissemination,
distribution or copying of this message is prohibited. Please
notify the sender immediately by e-mail if you have received
this e-mail by mistake and delete this e-mail from your system.
E-mail transmission cannot be guaranteed to be secure or
error-free as information could be intercepted, corrupted, lost,
destroyed, arrive late or incomplete, or contain viruses. The
sender therefore does not accept liability for any errors or
omissions in the contents of this message, which arise as a
result of e-mail transmission.
****************************************************************

В списке pgsql-performance по дате отправления:

Предыдущее
От: "petchimuthu lingam"
Дата:
Сообщение: how many index can have????
Следующее
От: "sathiya psql"
Дата:
Сообщение: list user created triggers