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From:Phil Date:May 21 2008 1:29pm
Subject:Re: DESC index column
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yes, you'd have to alter the queries to use the new index. As I say it's
very application dependent and does not always apply, but you can normally
shoehorn any application to use it.

Phil

On Wed, May 21, 2008 at 9:22 AM, Bof <bof90@stripped> wrote:

> Hi Phil -
>
> Thanks for the suggestion. Might that involve possibly
> changing queries in the web application hitting the
> database so that it uses the new column, or would the
> indexing on the new column take care of speeding up
> the existing queries?
>
> cheers
> Iain
> --
>
>
> --- Phil <freedc.bok@stripped> wrote:
>
> > What I've done in the past is to create extra
> > columns which contain the
> > reverse of a number/date used previously in an
> > index.
> >
> > So, for instance if it's a simple INT column (A) and
> > you know the max would
> > be 9999999 for example, create an extra column and
> > populate that with
> > (10000000 - A) and use it as an ASC index.
> >
> > Same can be done with dates.
> >
> > Not always applicable, but it works and is fairly
> > easy to implement.
> >
> > Phil
> >
> > On Tue, May 20, 2008 at 2:20 PM, Bof
> > <bof90@stripped> wrote:
> >
> > > Hi all -
> > > Is there a good workaround for mysql's lack of
> > 'DESC'
> > > functionality when creating an index?
> > >
> > > I'm looking at migrating an Oracle RAC database to
> > > mysql (InnoDB or Cluster - testing both at the
> > > moment), and the Oracle database uses a lot of
> > > multi-column indexes with some colums indexed in
> > > descending order.
> > >
> > > If I can't emulate the descending index colums
> > somehow
> > > it's likely to seriously impact performance and
> > > possibly derail the prospect of migration - help!
> > >
> > > cheers
> > > Iain
> > > --
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > --
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> >
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> > >
> >
> >
> >
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> >
>
>
>
>
>


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Thread
DESC index columnBof21 May
  • Re: DESC index columnPhil21 May
    • Re: DESC index columnBof21 May
      • Re: DESC index columnPhil21 May
  • Re: DESC index columnRob Wultsch21 May