Stuart Bishop wrote:
On Tue, Mar 31, 2009 at 11:20 AM, Tom Lane <[email protected]> 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.
+1 for throwing an error. That's what we do for views, composite types,
and GIN indexes as well. If you want to write a query to call
pgstattuple for all tables in pg_class, you'll need to exclude all those
cases anyway. To exclude temp tables of other sessions, you'll need to
add "AND pg_is_other_temp_schema(relnamespace)".
I'm ok with returning NULLs as well, but returning zeroes doesn't feel
right.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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