On Wed, 2008-12-24 at 09:59 -0500, Robert Treat wrote: > I think the uncertainty comes from peoples experience with typical > replication > use cases vs a lack of experience with this current implementation.
Quite possibly. Publishing user feedback on this will be very important in making this a usable feature. I'd be very happy if you were to direct the search for optimal usability. > One such example is that it is pretty common to use read-only slaves to do > horizontal scaling of read queries across a bunch of slaves. This is not the > scenario of running reporting queries on a second machine to lower load; you > would be running a large number of read-only, relativly short, oltp-ish > queries (think pg_benchs select only test i suppose), but you also have a > fairly regular stream of inserts/updates going on with these same tables, its > just you have 95/5 split of read/write (or similar). One thing to consider also is latency of information. Sending queries to master or slave may return different answers if querying very recent data. > This is standard practice in things like mysql or using slony or what have > you. I suspect it's one of the first things people are going to want to do > with hot standby. But it's unclear how well this will work because we don't > have any experience with it yet, coupled with the two downsides being > mentioned as canceled queries and replay lag, which happen to be probably the > two worst downsides you would have in the above scenario. :-) > > Hmm.... I'm not sure why I didn't think of running this test before, but > read/write pg_bench on a master with pg_bench select test on slave isn't that > bad of a scenario to match the above; it might be a little too much activity > on the master, but has anyone else run such a test? > -- 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