Re: Re: BUG #13685: Archiving while idle every archive_timeout with wal_level hot_standby

On Sun, Dec 20, 2015 at 6:44 PM, Michael Paquier <michael.paquier@gmail.com> wrote:
> On Sun, Nov 8, 2015 at 9:50 PM, Michael Paquier
> <michael.paquier@gmail.com> wrote:
> > On Sat, Nov 7, 2015 at 3:54 PM, Michael Paquier wrote:
> >> I thought about something like that at some point by saving a minimum
> >> activity pointer in XLogCtl, updated each time a segment was forcibly
> >> switched or after inserting a checkpoint record. Then the bgwriter
> >> looked at if the current insert position matched this minimum activity
> >> pointer, skipping LogStandbySnapshot if both positions match. Does
> >> this match your line of thoughts?
> >
> > Looking at the code, it occurred to me that the LSN position saved for
> > a XLOG_SWITCH record is the last position of current segment, so we
> > would still need to check if the current insert LSN matches the
> > beginning of a new segment and if the last segment was forcibly
> > switched by saving RecPtr of RequestXLogSwitch in XLogCtl for example.
> > Thoughts?
>
> I haven't given up on this patch yet, and putting again my head on
> this problem I have finished with the patch attached, which checks if
> the current insert LSN position is at the beginning of a segment that
> has just been switched to decide if a standby snapshot should be
> logged or not. This allows bringing back an idle system to the pre-9.3
> state where a segment would be archived in the case of a low
> archive_timeout only when a checkpoint has been issued on the system.