Re: checkpoint_timout with no WAL activity

On Mon, Nov 7, 2016 at 9:21 PM, Tom DalPozzo <t.dalpozzo@gmail.com> wrote:
> I know that, but with neither database activity or chekpoint, it doesn't
> force anything. The fact is that there are checkpoints being executed every
> checkpoint_timeout, and I don't understand why as if no WAL has been written
> we should not care about passing the timeout.

You may want to look at that:
https://www.postgresql.org/message-id/20151016203031.3019.72930@wrigleys.postgresql.org
And the patches on this thread to fix the checkpoint skip logic:

https://www.postgresql.org/message-id/flat/CAB7nPqQcPqxEM3S735Bd2RzApNqSNJVietAC=6kfkYv_45dKwA@mail.gmail.com#CAB7nPqQcPqxEM3S735Bd2RzApNqSNJVietAC=6kfkYv_45dKwA@mail.gmail.com

My guess is that you are using 9.6 because wal_level = archive is
equivalent to hot_standby, and the checkpoint skip logic is broken
because of standby snapshots happening in the bgwriter...
--
Michael