Re: pg_filedump 9.3: checksums (and a few other fixes)

On 2013-06-26 21:18:49 -0700, Peter Geoghegan wrote:
> On Wed, Jun 26, 2013 at 8:27 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > TBH, I've always been annoyed that pg_filedump is GPL and so there's no
> > way for us to just ship it in contrib. (That stems from Red Hat
> > corporate policy of a dozen years ago, but the conflict is real anyway.)
> > If somebody is sufficiently excited about this topic to do something
> > that's largely new anyway, I'd be in favor of starting from scratch so
> > it could be put under the usual Postgres license.
>
> Heroku are interested in online verification of basebackups (i.e.
> using checksums to verify the integrity of heap files as they are
> backed up, with a view to relying less and less on logical backups). I
> am very glad that you made the page checksums stuff available to
> external utilities in commit f04216341dd1cc235e975f93ac806d9d3729a344.
>
> In the last couple of days, I haven't been able to figure out a way to
> solve the problem of torn pages in a way that isn't a complete kludge
> (with a hopefully-acceptable risk of false positives), so I've been
> operating under the assumption that anything I produce here won't be
> up to the standards of contrib.

Why not do this from a function/background worker in the backend where
you can go via the buffer manager to avoid torn pages et al. If you use
a buffer strategy the cache poisoning et al should be controlleable.

Greetings,

Andres Freund

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