Mark Kirkwood <[EMAIL PROTECTED]> writes:
> It is a bit confusing - '(distinct) cardinality' might be a better
> heading for their 'cardinality' column!
The usual mathematical meaning of "cardinality" is "the number of
members in a set". That isn't real helpful for the point at hand,
because the
chris smith wrote:
It'd be nice if the database developers agreed on what terms meant.
http://dev.mysql.com/doc/refman/5.1/en/myisam-index-statistics.html
The SHOW INDEX statement displays a cardinality value based on N/S,
where N is the number of rows in the table and S is the average value
chris smith wrote:
> I believe postgres (because it's a lot more standards compliant).. but
> sheesh - what a difference!
>
> This week's task - stop reading mysql documentation.
You don't _have_ to believe Postgres -- this is stuff taught in any
statistics course.
--
Alvaro Herrera
On 4/2/06, chris smith <[EMAIL PROTECTED]> wrote:
> On 4/2/06, Jim C. Nasby <[EMAIL PROTECTED]> wrote:
> > On Sat, Apr 01, 2006 at 11:23:37AM +1000, chris smith wrote:
> > > On 4/1/06, Brendan Duddridge <[EMAIL PROTECTED]> wrote:
> > > > Hi Jim,
> > > >
> > > > I'm not quite sure what you mean by t
On 4/2/06, Jim C. Nasby <[EMAIL PROTECTED]> wrote:
> On Sat, Apr 01, 2006 at 11:23:37AM +1000, chris smith wrote:
> > On 4/1/06, Brendan Duddridge <[EMAIL PROTECTED]> wrote:
> > > Hi Jim,
> > >
> > > I'm not quite sure what you mean by the correlation of category_id?
> >
> > It means how many disti
On 3/31/06, Magnus Hagander <[EMAIL PROTECTED]> wrote:
> > This is a blatant thread steal... but here we go...
> > Do people have any opinions on the pgsql driver?
> I beleive so. I've been using it for a long time with zero problems.
> While I don't use many of the exotic features in it, I doubt
Hi Jim,
from SELECT * FROM pg_stats WHERE tablename='table' AND
attname='category_id'
I find correlation on category_product for category_id is 0.643703
Would setting the index on category_id to be clustered help with this?
Thanks,
__
On Sat, Apr 01, 2006 at 11:23:37AM +1000, chris smith wrote:
> On 4/1/06, Brendan Duddridge <[EMAIL PROTECTED]> wrote:
> > Hi Jim,
> >
> > I'm not quite sure what you mean by the correlation of category_id?
>
> It means how many distinct values does it have (at least that's my
> understanding of i
On 01/04/06, Magnus Hagander <[EMAIL PROTECTED]> wrote:
> > This is a blatant thread steal... but here we go...
> > Do people have any opinions on the pgsql driver?
>
> It's very nice.
...
Thanks for the tips - i'll try a couple of test apps soon.
Cheers
Antoine
--
This is where I should put s
