Re: [GENERAL] pgstattuple triggered checkpoint failure and database outage? - Mailing list pgsql-hackers

From Stuart Bishop
Subject Re: [GENERAL] pgstattuple triggered checkpoint failure and database outage?
Date
Msg-id 6bc73d4c0903302129h77774d49o5db204bd785bf335@mail.gmail.com
Whole thread Raw
In response to Re: [GENERAL] pgstattuple triggered checkpoint failure and database outage?  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: Re: [GENERAL] pgstattuple triggered checkpoint failure and database outage?  (Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>)
List pgsql-hackers
On Tue, Mar 31, 2009 at 11:20 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:

> A quick look at contrib/pgstattuple shows that it makes no effort
> whatsoever to avoid reading temp tables belonging to other sessions.
> So even if that wasn't Stuart's problem (and I'll bet it was), this
> is quite broken.
>
> There is no way that pgstattuple can compute valid stats for temp
> tables of other sessions; it doesn't have access to pages in the other
> sessions' temp buffers.  It seems that the alternatives we have are
> to make it throw error, or to silently return zeroes (or perhaps
> nulls?).  Neither one is tremendously appetizing.  The former would
> be especially unhelpful if someone tried to write a query to apply
> pgstattuple across all pg_class entries, which I kinda suspect is
> what Stuart did.

This is exactly what happened, and temporary tables belonging to other
sessions where fed to pgstattuple.


--
Stuart Bishop <stuart@stuartbishop.net>
http://www.stuartbishop.net/


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