On Thu, Nov 27, 2014 at 11:42 PM, Andres Freund <and...@2ndquadrant.com> wrote: > On 2014-11-27 13:00:57 +0900, Michael Paquier wrote: >> This is backward-incompatible in the fact that forcibly-written FPWs >> would be compressed all the time, even if FPW is set to off. The >> documentation of the previous patches also mentioned that images are >> compressed only if this parameter value is switched to compress. > > err, "backward incompatible"? I think it's quite useful to allow > compressing newpage et. al records even if FPWs aren't required for the > hardware. Incorrect words. This would enforce a new behavior on something that's been like that for ages even if we have a switch to activate it.
> One thing Heikki brought up somewhere, which I thought to be a good > point, was that it might be worthwile to forget about compressing FDWs > themselves, and instead compress entire records when they're large. I > think that might just end up being rather beneficial, both from a code > simplicity and from the achievable compression ratio. Indeed, that would be quite simple to do. Now determining an ideal cap value is tricky. We could always use a GUC switch to control that but that seems sensitive to set, still we could have a recommended value in the docs found after looking at some average record size using the regression tests. -- Michael -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
