Re: Query only slow on first run

Поиск
Список
Период
Сортировка
От Steinar H. Gunderson
Тема Re: Query only slow on first run
Дата
Msg-id 20071128203442.GB30600@uio.no
обсуждение исходный текст
Ответ на Re: Query only slow on first run  (cluster <skrald@amossen.dk>)
Ответы Re: Query only slow on first run  (cluster <skrald@amossen.dk>)
Список pgsql-performance
On Wed, Nov 28, 2007 at 09:16:08PM +0100, cluster wrote:
> Hmm, actually I still don't understand why it takes 6400 ms to fetch the
> rows. As far as I can see the index used is "covering" so that real row
> lookups shouldn't be necessary.

The indexes don't contain visibility information, so Postgres has to look up
the row on disk to verify it isn't dead.

> Also, only the the random_numbers induces by questions with status = 1
> should be considered - and this part is a relatively small subset.

Again, you'll need to have a combined index if you want this to help you any.

/* Steinar */
--
Homepage: http://www.sesse.net/

В списке pgsql-performance по дате отправления:

Предыдущее
От: cluster
Дата:
Сообщение: Re: Query only slow on first run
Следующее
От: david@lang.hm
Дата:
Сообщение: Re: TB-sized databases