From: Ragnar Hafstað <gnari@simnet.is>
To: pgsql-performance@postgresql.org
Cc: Andrei Bintintan <klodoma@ar-sd.net>
Cc: pgsql-sql@postgresql.org
Subject: Re: [SQL] OFFSET impact on Performance???
Date: Thu, 20 Jan 2005 19:23:12 +0000
Message-ID: <1106248992.22416.25.camel@localhost.localdomain> (raw)
In-Reply-To: <1106248326.22416.22.camel@localhost.localdomain>
References: <019f01c4fee1$1b58d600$0b00a8c0@forge>
<41EF9FD3.5020400@archonet.com>
<020d01c4fef6$595bb9d0$0b00a8c0@forge>
<87pt00c9zd.fsf@stark.xeocode.com>
<1106248326.22416.22.camel@localhost.localdomain>
On Thu, 2005-01-20 at 19:12 +0000, Ragnar Hafstað wrote:
> On Thu, 2005-01-20 at 11:59 -0500, Greg Stark wrote:
>
> > The best way to do pages for is not to use offset or cursors but to use an
> > index. This only works if you can enumerate all the sort orders the
> > application might be using and can have an index on each of them.
> >
> > To do this the query would look something like:
> >
> > SELECT * FROM tab WHERE col > ? ORDER BY col LIMIT 50
> >
> > Then you take note of the last value used on a given page and if the user
> > selects "next" you pass that as the starting point for the next page.
>
> this will only work unchanged if the index is unique. imagine , for
> example if you have more than 50 rows with the same value of col.
>
> one way to fix this is to use ORDER BY col,oid
and a slightly more complex WHERE clause as well, of course
gnari
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To: pgsql-sql@postgresql.org
Cc: gnari@simnet.is, pgsql-performance@postgresql.org, klodoma@ar-sd.net
Subject: Re: [SQL] OFFSET impact on Performance???
In-Reply-To: <1106248992.22416.25.camel@localhost.localdomain>
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