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Re: multicolumn index column order

From: "Valentine Gogichashvili" <valgog(at)gmail(dot)com>
To: "andrew(at)pillette(dot)com" <andrew(at)pillette(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: multicolumn index column order
Date: 2007-07-24 07:40:43
Message-ID: 3ce9822f0707240040o2f358155p7ff7537bbe986209@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
On 7/24/07, andrew(at)pillette(dot)com <andrew(at)pillette(dot)com> wrote:
>
> valgog <valgog(at)gmail(dot)com> wrote ..
> > On Jul 23, 7:00 pm, t(dot)(dot)(dot)(at)sss(dot)pgh(dot)pa(dot)us (Tom Lane) wrote:
> > > valgog <val(dot)(dot)(dot)(at)gmail(dot)com> writes:
> > > > how to build an multicolumn index with one column order ASCENDING
> and
> > > > another column order DESCENDING?
> > >
> > > Use 8.3 ;-)
> > >
> > > In existing releases you could fake it with a custom reverse-sorting
> > > operator class, but it's a pain in the neck to create one.
>
> I've often gotten what I want by using a calculated index on (f1, -f2).
> ORDER BY will take an expression, e.g. ORDER BY f1, -f2. Simpler than a
> custom operator.
>


Yes, this is true, but I do now know how to make text order be reversible?
There is no - (minus) operator for text value. By now it is not a problem
for me, but theoretically I do not see other chance to reverse text fields
order...

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