| From: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com> |
|---|---|
| To: | "Syed, Rahila" <Rahila(dot)Syed(at)nttdata(dot)com> |
| Cc: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Andres Freund <andres(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Rahila Syed <rahilasyed90(at)gmail(dot)com>, Rahila Syed <rahilasyed(dot)90(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [REVIEW] Re: Compression of full-page-writes |
| Date: | 2014-11-27 04:00:57 |
| Message-ID: | CAB7nPqR8rHg-nqLWcEtPn0Nhrn4DS8Jzue1u4VAWx2O493PtrQ@mail.gmail.com |
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On Wed, Nov 26, 2014 at 8:27 PM, Syed, Rahila <Rahila(dot)Syed(at)nttdata(dot)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.
--
Michael
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