On Fri, 2010-09-03 at 09:55 +0300, Heikki Linnakangas wrote: > On 03/09/10 09:36, Simon Riggs wrote: > > On Fri, 2010-09-03 at 12:50 +0900, Fujii Masao wrote: > >> That design would affect what the standby should reply. If we choose > >> async/recv/fsync/replay on a per-transaction basis, the standby > >> should send multiple LSNs and the master needs to decide when > >> replication has been completed. OTOH, if we choose just sync/async, > >> the standby has only to send one LSN. > >> > >> The former seems to be more useful, but triples the number of ACK > >> from the standby. I'm not sure whether its overhead is ignorable, > >> especially when the distance between the master and the standby is > >> very long. > > > > No, it doesn't. There is no requirement for additional messages. > > Please explain how you do it then. When a commit record is sent to the > standby, it needs to acknowledge it 1) when it has received it, 2) when > it fsyncs it to disk and c) when it's replayed. I don't see how you can > get around that. > > Perhaps you can save a bit by combining multiple messages together, like > in Nagle's algorithm, but then you introduce extra delays which is > exactly what you don't want.
>From my perspective, you seem to be struggling to find reasons why this should not happen, rather than seeing the alternatives that would obviously present themselves if your attitude was a positive one. We won't make any progress with this style of discussion. -- Simon Riggs www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Training and Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers