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Re: Replication Syatem

From: "Gauri Kanekar" <meetgaurikanekar(at)gmail(dot)com>
To: "Greg Smith" <gsmith(at)gregsmith(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Replication Syatem
Date: 2008-04-29 11:05:40
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
From most of the reply found that upgrade to higher version of postgres  may
be to 8.3.1 may be one of the solution to tackle this problem

Checked about HOT feature in 8.3.1.

Do we need to do any special config changes or any other setting for HOT to

Any special guideline to follow to make HOT working??

~ Gauri

On Tue, Apr 29, 2008 at 2:07 PM, Greg Smith <gsmith(at)gregsmith(dot)com> wrote:

> On Tue, 29 Apr 2008, Gauri Kanekar wrote:
>  We do vacuum full, as vacuum verbose analyse dont regain space for us.
> >
> Ah, now we're getting to the root of your problem here.  You expect that
> VACUUM should reclaim space.
> Whenever you UPDATE a row, it writes a new one out, then switches to use
> that version.  This leaves behind the original.  Those now unused rows are
> what VACUUM gathers, but it doesn't give that space back to the operating
> system.
> The model here assumes that you'll need that space again for the next time
> you UPDATE or INSERT a row.  So instead VACUUM just keeps those available
> for database reuse rather than returning it to the operating system.
> Now, if you don't VACUUM frequently enough, this model breaks down, and
> the table can get bigger with space that may never get reused.  The idea is
> that you should be VACUUMing up now unneeded rows at about the same rate
> they're being re-used.  When you don't keep up, the database can expand in
> space that you don't get back again.  The right answer to this problem is
> not to use VACUUM FULL; it's to use regular VACUUM more often.
> --
> * Greg Smith gsmith(at)gregsmith(dot)com Baltimore, MD


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