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Re: BUG #6528: pglesslog still referenced in docs, but no 9.1 support

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>,"stuart(dot)bishop" <stuart(dot)bishop(at)canonical(dot)com>,Pg Bugs <pgsql-bugs(at)postgresql(dot)org>, koichi(dot)szk(at)gmail(dot)com
Subject: Re: BUG #6528: pglesslog still referenced in docs, but no 9.1 support
Date: 2012-04-09 18:51:49
Message-ID: 20120409185149.GD3379@momjian.us (view raw or flat)
Thread:
Lists: pgsql-bugs
 On Mon, Apr 09, 2012 at 03:37:09PM -0300, Alvaro Herrera wrote:
> 
> Excerpts from Bruce Momjian's message of lun abr 09 15:13:10 -0300 2012:
> > On Mon, Apr 09, 2012 at 10:10:34AM -0400, Robert Haas wrote:
> 
> > > This complaint appears to be accurate.  I think we should go ahead and
> > > remove that mention.
> > 
> > Agreed;  removed with the attached patch.  I didn't bother keeping the
> > gzip mention because I assume there is little value to using without
> > pglesslog.
> 
> I'm not sure that assumption holds.  I think you're thinking of the hack
> that zeroes out the "empty" holes in the middle of data pages; those
> didn't compress well unless zeroed out before compression.  This tool is
> not about that, but rather about removing redundant info from WAL files.
> It seems to me that WAL files would be as gzip-compressible regardless
> of pglesslog being applied.  (Another related tool is clearxlogtail

OK, docs updated with the attached patch.

> which zeroes areas from WAL files when they are empty because of an
> early switch due to archive timeout).

Should we document that?

> The funny thing is, apparently pg_lesslog was intentionally broken by
> changing XLR_BKP_REMOVABLE to XLP_BKP_REMOVABLE (different semantics?)
> and the fixes to make it compile again look simple.  It's a bit strange
> that NTT stopped maintaining the tool .. Maybe it wasn't useful anymore?

No idea.

-- 
  Bruce Momjian  <bruce(at)momjian(dot)us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +

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Next:From: Kevin GrittnerDate: 2012-04-09 19:07:43
Subject: Re: BUG #6528: pglesslog still referenced in docs, but no 9.1 support
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Subject: Re: BUG #6528: pglesslog still referenced in docs, but no 9.1 support

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