Re: More grist for the PostgreSQL vs MySQL mill
От
Peter Rosenthal
Тема
Re: More grist for the PostgreSQL vs MySQL mill
Дата
Msg-id
7806f6cc0701211519x37f62fber60c1be222e8979ae@mail.gmail.com
Ответ на
Re: More grist for the PostgreSQL vs MySQL mill (Andrew - Supernews)
Список
Дерево обсуждения
Re: More grist for the PostgreSQL vs MySQL mill Andrew - Supernews <andrew+nonews@supernews.com>
Re: More grist for the PostgreSQL vs MySQL mill "Peter Rosenthal" <voiperster@gmail.com>
Re: More grist for the PostgreSQL vs MySQL mill "Shashank Tripathi" <shashank.tripathi@gmail.com>
Re: More grist for the PostgreSQL vs MySQL mill Jeff Davis <pgsql@j-davis.com>
Re: More grist for the PostgreSQL vs MySQL mill Tom Lane <tgl@sss.pgh.pa.us>
Re: More grist for the PostgreSQL vs MySQL mill Chris <dmagick@gmail.com>
Re: More grist for the PostgreSQL vs MySQL mill "Peter Rosenthal" <voiperster@gmail.com>
Re: More grist for the PostgreSQL vs MySQL mill Ron Johnson <ron.l.johnson@cox.net>
Re: More grist for the PostgreSQL vs MySQL mill "Harald Armin Massa" <haraldarminmassa@gmail.com>
Re: More grist for the PostgreSQL vs MySQL mill "Chad Wagner" <chad.wagner@gmail.com>
Re: More grist for the PostgreSQL vs MySQL mill "Harald Armin Massa" <haraldarminmassa@gmail.com>
Back on topic, I can confirm that MySQL does indeed have various problems with optimizing sub-selects.
There are times where doing two seperate selects is orders of magnitude faster than doing a single with a sub-select due to index selection decisions.
Namely:
select * from table where table_id in (select something from othertable);
is much much slower than:
select something from othertable;
select * from table where table_id in (?, ?, ?, ?, ?, ?, ?, ...)
MySQL are aware of this optimization problem but it does not seem to be of very high priority.
Bad optimization of complex queries is why I am looking at pg.
On 21/01/07, Andrew - Supernews <andrew+nonews@supernews.com> wrote:
On 2007-01-21, Ron Johnson <ron.l.johnson@cox.net> wrote:
>> And no BDB (at least last I checked is not GPL)
>
> It's BSD (for obvious reasons), no?
No, Sleepycat's licence is _NOT_ BSD.
--
Andrew, Supernews
http://www.supernews.com - individual and corporate NNTP services
---------------------------(end of broadcast)---------------------------
TIP 6: explain analyze is your friend
В списке pgsql-general по дате отправления
