On 2/2/16 11:10 PM, Robert Haas wrote: > On Tue, Feb 2, 2016 at 10:58 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: >> I've gotta go with the "paternalism" side of the argument here. Suppose >> you configure your system to checkpoint once a year --- what is going to >> happen when the year is up? Or when you try to shut it down? You *will* >> regret such a setting. >> >> I don't think we should allow the checkpoint distances to be so large that >> checkpoints don't happen in the normal course of events. I'd be okay with >> the max being a day, perhaps. > > If smart people want to set checkpoint_timeout to a value higher > than 1 day, then I think we should let them.
Agreed - I have a specific instance where I would prefer the daily backups or checkpoint segments to be the primary source of checkpoints with checkpoint_timeout set to 36 hours and used only as a fallback. A limit of 1 day would be lower than I like though still better than what I have now, 1 hour. For this case I would probably configure: checkpoint_segments = 256 checkpoint_timeout = 36h So the daily backups would generally trigger the checkpoint unless there was unusually high volume in which case it would be checkpoint segments. Finally, if the backups weren't working and volume was normal then checkpoint_timeout would come along to save the day. In this case its all about reducing full-page writes on a medium-sized system with heavy churn in order to make a long backup/archive retention more cost-effective. Recovery time is not as much of an issue for this application. -- -David da...@pgmasters.net
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