Please reply-all so others can learn and contribute.
On Sun, Jul 29, 2007 at 09:38:12PM -0700, Craig James wrote:
> Decibel! wrote:
> >It's unlikely that it's going to be faster to index scan 2.3M rows than
> >to sequential scan them. Try setting enable_seqscan=false and see if it
> >is or not.
> Out of curiosity ... Doesn't that depend on the table? Are all of the data
> for one row stored contiguously, or are the data stored column-wise? If
> it's the former, and the table has hundreds of columns, or a few columns
> with large text strings, then wouldn't the time for a sequential scan
> depend not on the number of rows, but rather the total amount of data?
Yes, the time for a seqscan is mostly dependent on table size and not
the number of rows. But the number of rows plays a very large role in
the cost of an indexscan.
Decibel!, aka Jim C. Nasby, Database Architect decibel(at)decibel(dot)org
Give your computer some brain candy! www.distributed.net Team #1828
In response to
pgsql-performance by date
|Next:||From: Richard Huxton||Date: 2007-07-30 07:21:34|
|Subject: Re: Questions on Tags table schema|
|Previous:||From: Decibel!||Date: 2007-07-30 01:29:26|
|Subject: Re: RES: RES: select on 1milion register = 6s|