Date: Wed, 7 Jun 2006 09:50:20 -0500
From: "Jim C. Nasby" <jnasby@pervasive.com>
To: soni de <soni.de@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Regarding ALTER Command
Message-ID: <20060607145020.GT45331@pervasive.com>
References: <9f2e40a90606070543l1066f162v19fc0887d916e2bb@mail.gmail.com>
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On Wed, Jun 07, 2006 at 06:13:11PM +0530, soni de wrote:
> Hello,
> 
> 
> 
> We have database on which continueous operations of INSERT, DELETE, UPDATE
> are going on, In the mean time irrespective of INSERT and UPDATE we want to
> ALTER some filelds from the table can we do that?
> 
> Would the ALTER command on heavily loaded database create any perfomance
> problem?
> 
> Is it feasible to do ALTER when lots of INSERT operations are going on?
 
The problem you'll run into is that ALTER will grab an exclusive table
lock. If *all* the transactions hitting the table are very short, this
shouldn't be too big of an issue; the ALTER will block all new accesses
to the table while it waits for all the pending ones to complete, but if
all the pending ones complete quickly it shouldn't be a big issue.

If one of the pending statements takes a long time though...
 
> Postgresql version we are using is -- PostgreSQL 7.2.4

You very badly need to upgrade. 7.2 is no longer supported, and there
have been over a half-dozen data loss bugs fixed since then.
-- 
Jim C. Nasby, Sr. Engineering Consultant      jnasby@pervasive.com
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461