Re: BUG #8681: column 'n_tup_del' of pg_stat_user_tables doesn't change in case of truncate

From: Rod Taylor <rod(dot)taylor(at)gmail(dot)com>
To: Stephen Frost <sfrost(at)snowman(dot)net>
Cc: Anit Chakkarwar <anitchakkarwar(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #8681: column 'n_tup_del' of pg_stat_user_tables doesn't change in case of truncate
Date: 2013-12-16 23:06:51
Message-ID: CAKddOFAOJnDLM-Jde=Y_k8QK6GLVJk1fe_EQRGnYK-42zEH=5A@mail.gmail.com
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It's still an interesting question.

Why doesn't truncate reset table statistic to 0? The table state prior to a
truncate shouldn't influence vacuum or necessity after the truncate.

Not that vacuuming a recently truncated table would be expensive, but
Analyze timing is a concern.

regards,

Rod

On Mon, Dec 16, 2013 at 10:50 AM, Stephen Frost <sfrost(at)snowman(dot)net> wrote:

> Anit,
>
> * Anit Chakkarwar (anitchakkarwar(at)gmail(dot)com) wrote:
> > Now n_tup_del = 2, n_tup_ins=120, n_live_tup=20 in pg_stat_user_tables,
> but
> > how can I figure out what has happened to 98 rows?
>
> This is information for statistics- if you need an accurate count,
> you'll need to use a trigger and track that information explicitly..
> There can be other ways that n_tup_del can end up being inexact.
>
> Thanks,
>
> Stephen
>

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