Re: [GENERAL] pgstattuple triggered checkpoint failure and database outage?

On Tue, Mar 31, 2009 at 11:20 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)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(at)stuartbishop(dot)net>
http://www.stuartbishop.net/