On Tue, 2008-10-14 at 19:18 +0300, Peter Eisentraut wrote: > Tom Lane wrote: > > So I was looking for other omissions in utility.c, and I noticed that > > check_xact_readonly() doesn't reject CLUSTER, REINDEX, or VACUUM. > > Now the notion of "read only" that we're trying to enforce is pretty > > weak (I think it's effectively "no writes to non-temp tables"). > > But I can't see that CLUSTER is a read-only operation even under the > > weakest definitions, and I'm not seeing the rationale for REINDEX or > > VACUUM here either. > > I think the way the SQL standard meant the read-only flag is that the > transaction doesn't change the structure of or the data in the database > as seen by the next guy. So all of these commands are OK, I think. > > A theoretical use case is that you should be able to do the maximum set > of useful work in read-only mode on a Slony-I slave. No I haven't > checked what Slony does with these three commands, so let me have it. :-)
Well, read-only applies to queries on the Slony slave, not to other necessary work, which cannot be read only. In general, if one transaction is fully read-only I don't see why that should prevent other parts of the system from working normally. So I would say ban all the utilities mentioned from read-only transactions, and don't be influenced by what non-read only transactions do. -- Simon Riggs www.2ndQuadrant.com PostgreSQL Training, Services and Support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
