Re: optimizing queries and indexes...

Поиск
Список
Период
Сортировка
От Tom Lane
Тема Re: optimizing queries and indexes...
Дата
Msg-id 16540.1000614855@sss.pgh.pa.us
обсуждение исходный текст
Ответ на optimizing queries and indexes...  ("Robert J. Sanford, Jr." <rsanford@nolimitsystems.com>)
Ответы Re: optimizing queries and indexes...  ("Josh Berkus" <josh@agliodbs.com>)
Список pgsql-sql
[ Sorry for slow response, I've been out of town ]

"Robert J. Sanford, Jr." <rsanford@nolimitsystems.com> writes:
> [ some questions already ably answered by Josh and Stephan ]

I just wanted to throw in one more tidbit:

> for example, one thing that one of my friends said is:
>    select X
>    from big_table
>        ,little_table
>    Generally speaking, Oracle optimizes better
>    when the smaller/reducing tables are on the
>    bottom and the larger tables are on the top.
>    I believe SQLServer likes them in the opposite
>    direction.

Postgres absolutely does not care: the optimizer will always consider
both A-join-B and B-join-A orders for every join it has to do.  As
Stephan and Josh noted, you can constrain the join pairs the optimizer
will consider if you use explicit-JOIN syntax --- but each pair will be
considered in both directions.
        regards, tom lane


В списке pgsql-sql по дате отправления:

Предыдущее
От: A_Schnabel@t-online.de (Andre Schnabel)
Дата:
Сообщение: Re: To query many tables.
Следующее
От: Kovacs Baldvin
Дата:
Сообщение: Intentional, or bug?