On Tue, May 28, 2013 at 02:26:06PM -0700, Joshua D. Drake wrote: > >Sounds nice, but how would we do that? That would require libpq to know > >it, right? Do we pass anything back after parsing but before execution? > > Could it be optional? What about functions that modify the database > >--- isn't that only known at execution time? > > I can't speak to the actual C code that would be required but from a > user space, I could see something like this: > > con = psycopg2.connect(database='testdb', user='test', > transaction-type='r') > > Thus when the connection is made, before anything else is done, we > know it is a read only connection and therefore any load balancer > speaking libpq would also know it is a read only. The default of > course would be r/w and you would use a different connection handler > for r/w or w queries. > > The other option would be to do it on query execute but that doesn't > seem as efficient as it would have to be parsed each time. Although > it would still be better than reading the actual SQL.
Well, you could do SET TRANSACTION READ ONLY, and that would prevent any write transactions. You could assume it is a read query, and get the error and resubmit on the master if that happens, but that sounds inefficient. I thought you were asking for something where you could submit a query and it would report back as read/write or read-only. -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
