Skip site navigation (1) Skip section navigation (2)

Re: Various performance questions

From: Dror Matalon <dror(at)zapatec(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: Various performance questions
Date: 2003-10-27 07:43:57
Message-ID: 20031027074357.GG2979@rlx11.zapatec.com (view raw or flat)
Thread:
Lists: pgsql-performance
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 
1700 MLK Way
Berkeley, CA 94709
http://www.zapatec.com

In response to

pgsql-performance by date

Next:From: Neil ConwayDate: 2003-10-27 09:18:53
Subject: Re: explicit casting required for index use
Previous:From: Shridhar DaithankarDate: 2003-10-27 07:22:27
Subject: Re: Various performance questions

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group