Re: How do I know my table is bloated?

On Thu, May 30, 2013 at 3:36 PM, Igor Neyman <ineyman(at)perceptron(dot)com> wrote:

>
>
> From: Rodrigo Barboza [mailto:rodrigombufrj(at)gmail(dot)com]
> Sent: Thursday, May 30, 2013 2:24 PM
> To: Igor Neyman
> Cc: pgsql-admin(at)postgresql(dot)org
> Subject: Re: [ADMIN] How do I know my table is bloated?
>
>
> I am using the defualt values for autovaccum.
> How do you suggest to tune the autovacuum?
> If the problem is index bloat, autovaccum won't be a solution, am I right?
>
> ----------------------------------------------------------
>
> Rodrigo,
>
> I think you are putting "a cart in front of the horse" (so to speak).
> Did you verify that you have bloated indexes? Under normal conditions it
> shouldn't happen.
> From docs (http://www.postgresql.org/docs/9.2/static/routine-reindex.html
> ):
> "B-tree index pages that have become completely empty are reclaimed for
> re-use. However, there is still a possibility of inefficient use of space:
> if all but a few index keys on a page have been deleted, the page remains
> allocated. Therefore, a usage pattern in which most, but not all, keys in
> each range are eventually deleted will see poor use of space."
>
> So, yes, if index is really gets bloated than reindexing fixes this
> problem.
>
> Igor Neyman
>

Well, maybe I am.
But I am worried because I know that there are some tables that do lots of
updates and delete.
As this concept is new for me, I am trying to be prepared to detect a
situation like this.