Re: [REVIEW] Re: Compression of full-page-writes

On 2014-12-14 09:56:59 +0900, Michael Paquier wrote:
> On Sun, Dec 14, 2014 at 5:45 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> > On 13 December 2014 at 14:36, Michael Paquier <michael(dot)paquier(at)gmail(dot)com> wrote:
> >
> >> Something to be aware of btw is that this patch introduces an
> >> additional 8 bytes per block image in WAL as it contains additional
> >> information to control the compression. In this case this is the
> >> uint16 compress_len present in XLogRecordBlockImageHeader.
> >
> > So we add 8 bytes to all FPWs, or only for compressed FPWs?
> In this case that was all. We could still use xl_info to put a flag
> telling that blocks are compressed, but it feels more consistent to
> have a way to identify if a block is compressed inside its own header.

Your 'consistency' argument doesn't convince me.

Greetings,

Andres Freund

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Andres Freund http://www.2ndQuadrant.com/
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