On 2016-02-11 09:25:30 +0530, Amit Kapila wrote: > On Wed, Feb 10, 2016 at 1:42 PM, Michael Paquier <michael.paqu...@gmail.com> > wrote: > > > > On Wed, Feb 10, 2016 at 5:00 PM, Amit Kapila <amit.kapil...@gmail.com> > wrote: > > > Okay, but isn't it better that we remove the snapshot taken > > > at checkpoint time in the main branch or till where this code is > > > getting back-patched. Do you see any need of same after > > > having the logging of snapshot in bgwriter? > > > > But this one is necessary as well to allow hot standby faster to > > initialize, no? Particularly in the case where a bgwriter snapshot > > would have been taken just before the checkpoint, there may be up to > > 15s until the next one. > > > > It could be helpful if checkpoint is done at shorter intervals, otherwise > we anyway log it at 15s interval and if need faster initialisation > of hot-standby, then it is better to reduce the log snapshot interval > in bgwriter.
No. By emitting the first snapshot directly after the determination of the redo pointer, we can get into STANDBY_SNAPSHOT_READY more quickly. Especially if some of the snapshots are overflowed. During startup 15s can be a *long* time; but on the other hand there's not much benefit at logging snapshots more frequently when the system is up. I don't think we should tinker with the frequency/logging points, while fixing the issue here. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
