Re: [REVIEW] Re: Compression of full-page-writes - Mailing list pgsql-hackers

From Michael Paquier
Subject Re: [REVIEW] Re: Compression of full-page-writes
Date
Msg-id CAB7nPqR8rHg-nqLWcEtPn0Nhrn4DS8Jzue1u4VAWx2O493PtrQ@mail.gmail.com
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In response to Re: [REVIEW] Re: Compression of full-page-writes  ("Syed, Rahila" <Rahila.Syed@nttdata.com>)
Responses Re: [REVIEW] Re: Compression of full-page-writes  (Andres Freund <andres@2ndquadrant.com>)
Re: [REVIEW] Re: Compression of full-page-writes  (Rahila Syed <rahilasyed90@gmail.com>)
Re: [REVIEW] Re: Compression of full-page-writes  (Robert Haas <robertmhaas@gmail.com>)
List pgsql-hackers
On Wed, Nov 26, 2014 at 8:27 PM, Syed, Rahila <Rahila.Syed@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
ofFPW 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
compressforcibly 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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