Tom Lane <[email protected]> writes: > Well, as Heikki said, a stop-and-go WAL management approach could deal > with that use-case. What I'm concerned about here is the complexity, > reliability, maintainability of trying to interlock WAL application with > slave queries in any sort of fine-grained fashion.
Some admin functions for Hot Standby were removed from the path to ease its integration, there was a pause() and resume() feature. I think that offering this explicit control to the user would allow them to choose between HA setup and reporting setup easily enough: just pause the replay when running the reporting, resume it to get fresh data again. If you don't pause, any query can get killed, replay is the priority. Now as far as the feedback loop is concerned, I guess the pause() function would cause the slave to stop publishing any xmin in the master's procarray so that it's free to vacuum and archive whatever it wants to. Should the slave accumulate too much lag, it will resume from the archive rather than live from the SR link. How much that helps? Regards, -- dim -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
