Re: PITR: XLog File compression on Archive

Simon Riggs wrote:

> As a result, I have thought that there may be a way to remove those pages
> from the xlog files immediately before being copied away to archive, without
> effecting crash recovery logic AT ALL. The archiver process could read the
> xlog files and re-write them exactly as read to another file, but without
> the full page images - writing exactly the current xlog record format. This
> would mean that the archived xlog files would then become variable length.
> Apart from that, not much other code need change. The recovery logic
> wouldn't need to change at all - the xlog files would just simply never have
> full page images to re-apply. The archive logic would need enhancing to do
> the read/re-write, but much of that same code needs to be written/adapted
> anyway for the offline xlog file reader. The archive code itself  would
> simply copy to an intermediate file, say ARCHIVEFILE, just like we do on
> recovery - so the use of %p would still work as before and require
> redirecting only, no other changes.

So this means that the way to have an "hot spare" postgres that play
the logs while are arriving is not applicable anymore ?

See Tom advice:  http://archives.postgresql.org/pgsql-hackers/2004-08/msg00704.php
and my success:  http://archives.postgresql.org/pgsql-hackers/2004-08/msg00852.php


Am I right ?




Regards
Gaetano Mendola