Excerpts from Robert Haas's message of jue may 19 10:18:20 -0400 2011: > On Wed, May 18, 2011 at 7:11 PM, Alvaro Herrera > <alvhe...@commandprompt.com> wrote: > >> 1. I suggested that this looks a lot like the controls of pg_hba.conf > >> > >> When our DBAs are doing major management of replication, they are > >> known to reconfigure pg_hba.conf to lock out all users save for the > >> one used by Slony. > > > > Yeah, I mentioned this but I think it actually sucks. > > Why? I don't really see why this sucks.
Well, firstly because you need to involve the sysadmin to be able to write the file. (If you're considering a proposal to move adminpack into core, I recommend caution.) Second, because then the database owner can't do it. Third, because the business of having to programatically edit files is a pain in the butt. Fourth, it doesn't fix itself it something goes wrong. > > Well, I don't intend to lock "everything except the present connection". > > The only thing this LOCK DATABASE does is prevent the establishment of > > new connections. Existing connections can continue to exist and work. > > So you do the LOCK DATABASE, then boot whoever shouldn't be allowed > > (which is a separate step that needs to be taken), then do your deed. > > If you want the slon connections to persist, just don't terminate them. > > This strikes me as a hack. First, it's completely inconsistent with > how we lock tables or rows. A lock means you are the only one > accessing an object, not just that new accesses are locked out. It doesn't mean that -- you can already get FOR SHARE locks on rows and other non-blocking locks. Besides, the fact that databases are not locked out while the connection exists is a well known fact and I very much doubt that it's going to change. > Second, it relies on the fact that a new connection briefly grabs a > lock on the database that is then released. Yes. This is well known and it's not going away. > If we happened (for whatever reason) to want to change that to a > session lock, or get rid of it entirely, then this would break. That would break other things too, so I don't see it as a problem. -- Álvaro Herrera <alvhe...@commandprompt.com> The PostgreSQL Company - Command Prompt, Inc. PostgreSQL Replication, Consulting, Custom Development, 24x7 support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
