Re: [GENERAL] Tuning queries on large database

Поиск
Список
Период
Сортировка
От Rod Taylor
Тема Re: [GENERAL] Tuning queries on large database
Дата
Msg-id 1091711927.84496.22.camel@jester
обсуждение исходный текст
Ответ на Re: [GENERAL] Tuning queries on large database  (Valerie Schneider DSI/DEV <Valerie.Schneider@meteo.fr>)
Список pgsql-performance
> so it takes about 28 Gb instead of 68 Gb !

Huzzah!

> For my different queries, it's better but less performant than oracle :

Not surprising. Oracle has a number of optimizations that we don't have
implemented at this point, particularly where aggregates are involved.

One that PG could use, particularly for Q4, is the ability to execute a
selective sequential scan based on a read of the index -- right now it
pulls in actual data from the table structure while following the index
-- creates unnecessary disk-head movement.

The only solution to that, at the moment, is to cluster the table by
pk_data.


I am curious though, could you run the below query on both systems and
report back times?

        select 'Q4', * from data where num_poste between 600 and 625;

I'm wondering if Oracle is using a shortcut since the count(*) doesn't
actually require the data -- just knowledge of whether a matching row
exists or not.



В списке pgsql-performance по дате отправления:

Предыдущее
От: Gaetano Mendola
Дата:
Сообщение: Re: [GENERAL] Tuning queries on large database
Следующее
От: "Merlin Moncure"
Дата:
Сообщение: Re: [GENERAL] Tuning queries on large database