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From: Peter Eisentraut <[email protected]>
To: Devrim GÜNDÜZ <[email protected]>
Cc: pgsql-docs <[email protected]>
Subject: Re: Doc patch for truncate.sgml
Date: Thu, 28 Aug 2008 20:30:14 +0300
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>

Devrim GÜNDÜZ wrote:
> Attached is a doc patch for truncate.sgml. It improves info for
> TRUNCATE. Thanks to Andrew Sullivan for pointing out this.

> --- 34,44 ----
>      <command>DELETE</command> on each table, but since it does not actually
>      scan the tables it is faster. Furthermore, it reclaims disk space
>      immediately, rather than requiring a subsequent <command>VACUUM</command>
> !    operation. This is most useful on large tables. Also, 
> !    <command>TRUNCATE</command> rewrites system catalogue entries for
> !    that table, which makes running <command>ANALYZE</command> on a
> !    freshly-truncated table is a bad idea, because the statistics will be
> !    updated to indicate that the table is truly empty.
>     </para>
>    </refsect1>

If the table is in fact empty, why is it a bad idea to let the 
statistics reflect that?  I think you are making assumptions about 
certain usage patterns that do not always have to be true, and that are 
not written down anyway.

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