On Wed, Oct 18, 2017 at 9:14 AM, Craig Ringer <cr...@2ndquadrant.com> wrote: > Superficially at least, it sounds like a good idea.
Indeed. > We should only need a virtual xid when we're working with foreign > tables since we don't do any local heap changes. > > How's it work with savepoints? That's one thing to worry about. At least to me, it feels like cheating to allow an INSERT query to happen for a transaction which is read-only actually read-only because XactReadOnly is set to true when the transaction starts. I am wondering if we should extend BEGIN TRANSACTION with a sort of "WRITE ONLY FOREIGN" mode, which allows read queries as well as write queries for foreign tables, because we know that those will not generate WAL locally. This way it would be possible to block as well INSERT queries happening in a transaction which should be intrinsically read-only. + if (rte->relkind == 'f') + continue; Better to use RELKIND_FOREIGN_TABLE here. -- Michael -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers