On Fri, Feb 16, 2001 at 10:56:57PM +0100, Benjamin Pflugmann wrote:
>
> > When you set up your database server so that it has enough RAM to
> > keep the whole database in main memory (buffer cache), random reads
> > don't need to wait for physical disk seeks and can be very fast.
> [...]
> > So m
Hi.
On Fri, Feb 16, 2001 at 09:42:02AM +0100, [EMAIL PROTECTED] wrote:
> Benjamin Pflugmann wrote :
[...]
> > "Second" is never the best way. MySQL uses "First" up to some
> > percentage of the amount of records (30% I believe), then uses
> > "Third", because reading the data in file order (unsor
Benjamin Pflugmann wrote :
>
> Hi.
> []
>
> If MySQL uses the index, it has one of two possibilities.
>
> First:
> 1. Read the whole isbn index, and for each row
> 2. seek the record in the data file and get author from it.
> This is quite slow because of the random file seeks needed.
>
>
Hi.
On Thu, Feb 15, 2001 at 03:53:39PM -0500, [EMAIL PROTECTED] wrote:
> 15/02/01 15:14, Quentin Bennett, [EMAIL PROTECTED]:
[...]
> > Adding the author to the query means that the query now has to go to the
> > data file to get the information, and since there is no restriction on isbn,
> > the
15/02/01 15:14, Quentin Bennett, [EMAIL PROTECTED]:
> Hi,
>
> I think you are mis-understanding the information provided. What the "using
> index" note means is that the isbn column is part of the index, and since
> that is all that is selected, the index file is used to provide the data,
> the
s, is
the result pre-sorted, so the order by is trivial, or is a sort still
performed.
Hope this helps
Regards
Quentin
-Original Message-
From: François Bélanger [mailto:[EMAIL PROTECTED]]
Sent: Friday, 16 February 2001 08:01
To: [EMAIL PROTECTED]
Subject: Index not used for order by wh
