Re: Various performance questions

On Mon, Oct 27, 2003 at 12:52:27PM +0530, Shridhar Daithankar wrote:
> Dror Matalon wrote:
> 
> >On Mon, Oct 27, 2003 at 01:04:49AM -0500, Christopher Browne wrote:
> >>Most of the time involves:
> >>
> >>a) Reading each page of the table, and
> >>b) Figuring out which records on those pages are still "live."
> >
> >
> >The table has been VACUUM ANALYZED so that there are no "dead" records.
> >It's still not clear why select count() would be slower than select with
> >a "where" clause.
> 
> Do a vacuum verbose full and then everything should be within small range 
> of each other.
> 

I did vaccum full verbose and the results are the same as before, 55
seconds for count(*) and 26 seconds for count(*) where channel < 5000.

> Also in the where clause, does explicitly typecasting helps?
> 
> Like 'where channel<5000::int2;'

It makes no difference.

> 
>  HTH
> 
>  Shridhar
> 

-- 
Dror Matalon
Zapatec Inc 
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