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

On 2012-04-09 15:37:09 -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
> which zeroes areas from WAL files when they are empty because of an
> early switch due to archive timeout).
>
> 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?

One problem is that it was hard to trust the tool, it had relatively bad
bugs several times and it wasn't maintained by pgdg...

Andres Freund

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