Re: Block-level CRC checks

Robert Haas wrote:
> On Fri, Dec 4, 2009 at 9:48 AM, Alvaro Herrera
> <alvherre(at)commandprompt(dot)com> wrote:
> > Heikki Linnakangas escribi?:
> >> Simon Riggs wrote:
> >> > On Fri, 2009-12-04 at 09:52 -0300, Alvaro Herrera wrote:
> >> >
> >> >> BTW with VACUUM FULL removed I assume we're going to get rid of
> >> >> HEAP_MOVED_IN and HEAP_MOVED_OFF too, right?
> >> >
> >> > Much as I would like to see those go, no. VF code should remain for some
> >> > time yet, IMHO.
> >>
> >> I don't think we need to keep VF code otherwise, but I would leave
> >> HEAP_MOVED_IN/OFF support alone for now for in-place upgrade. Otherwise
> >> we need a pre-upgrade script or something to scrub them off.
> >
> > CRCs are going to need scrubbing anyway, no? ?Oh, but you're assuming
> > that CRCs are optional, so not everybody would need that, right?
>
> If we can make not only the validity but also the presence of the CRC
> field optional, it will simplify things greatly for in-place upgrade,
> I think, because the upgrade won't itself require expanding the page.
> Turning on the CRC functionality for a particular table may require
> expanding the page, but that's a different problem. :-)

Well, I am not sure how we would turn the _space_ used for CRC on and
off because you would have to rewrite the entire table/database to turn
it on, which seems unfortunate.

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

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