On 2014-11-27 13:00:57 +0900, Michael Paquier wrote: > On Wed, Nov 26, 2014 at 8:27 PM, Syed, Rahila <rahila.s...@nttdata.com> wrote: > > Don't we need to initialize doPageCompression similar to doPageWrites in > > InitXLOGAccess? > Yep, you're right. I missed this code path. > > > Also , in the earlier patches compression was set 'on' even when fpw GUC is > > 'off'. This was to facilitate compression of FPW which are forcibly written > > even when fpw GUC is turned off. > > doPageCompression in this patch is set to true only if value of fpw GUC is > > 'compress'. I think its better to compress forcibly written full page > > writes. > Meh? (stealing a famous quote).
> 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. 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. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
