From: | Ivan Sergio Borgonovo <mail(at)webthatworks(dot)it> |
---|---|
To: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: quick question abt pg_dump and restore |
Date: | 2008-01-09 16:28:15 |
Message-ID: | 20080109172815.2234f0b5@webthatworks.it |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-general |
On Wed, 09 Jan 2008 10:54:21 -0500
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> > Josh Harrison escribió:
> >> Fine. I can use order by when I want to order it in terms of
> >> some columns. But What if I want to maintain the same order as
> >> in the database1? ie., I want my rows of TableABC in Database2
> >> to be the same order as the rows in TableABC in Database 1 ???
>
> > You can't.
>
> According to the SQL standard, a table is an *unordered* collection
> of rows, and the results of any query are produced in an
> unspecified order (unless you use ORDER BY). The ambiguity about
> row ordering is intentional and is exploited by most DBMSes
> including Postgres to improve implementation efficiency. If you
> assume there is such a thing as a specific ordering within a table,
> you'll live to regret it eventually.
Does it make any sense *knowing* how the implementation works to load
records in a table in a specific order to improve performances?
And yeah I know that once you start deleting/updating row you may
lose the advantage you gained betting on some peculiarity of the
implementation... but in case you're dealing with a mostly static
table?
eg. if I'm importing a table does it make any sense to pre-sort it
before importing it in postgres?
--
Ivan Sergio Borgonovo
http://www.webthatworks.it
From | Date | Subject | |
---|---|---|---|
Next Message | Scott Marlowe | 2008-01-09 16:30:45 | Re: count(*) and bad design was: Experiences with extensibility |
Previous Message | Ivan Sergio Borgonovo | 2008-01-09 16:21:24 | Re: count(*) and bad design was: Experiences with extensibility |