On Tue, Apr 3, 2018 at 10:48 PM, Michael Banck <michael.ba...@credativ.de>
> On Tue, Apr 03, 2018 at 08:48:08PM +0200, Magnus Hagander wrote:
> > On Tue, Apr 3, 2018 at 8:29 PM, Tom Lane <t...@sss.pgh.pa.us> wrote:
> > I'd bet a good lunch that nondefault BLCKSZ would break it, as well,
> > > since the way in which the corruption is induced is just guessing
> > > as to where page boundaries are.
> > Yeah, that might be a problem. Those should be calculated from the block
> > size.
> > Also, scribbling on tables as sensitive as pg_class is just asking for
> > > trouble IMO. I don't see anything in this test, for example, that
> > > prevents autovacuum from running and causing a PANIC before the test
> > > can complete. Even with AV off, there's a good chance that clobber-
> > > cache-always animals will fall over because they do so many more
> > > physical accesses to the system catalogs. I'd suggest inducing the
> > > corruption in some user table(s) that we can more tightly constrain
> > > the source server's accesses to.
> > Yeah, that seems like a good idea. And probably also shut the server down
> > while writing the corruption, just in case.
> > Will stick looking into that on my todo for when I'm back, unless beaten
> > it. Michael, you want a stab at it?
> Attached is a patch which does that hopefully:
> 1. creates two user tables, one large enough for at least 6 blocks
> (around 360kb), the other just one block.
> 2. stops the cluster before scribbling over its data and starts it
> 3. uses the blocksize (and the pager header size) to determine offsets
> for scribbling.
> I've tested it with blocksizes 8 and 32 now, the latter should make sure
> that the first table is indeed large enough, but maybe something less
> arbitrary than "10000 integers" should be used?
> Anyway, sorry for the hassle.
Applied, with the addition that I explicitly disabled autovacuum on those
tables as well.
We might want to enhance it further by calculating the figure 10,000 based
on blocksize perhaps?
Me: https://www.hagander.net/ <http://www.hagander.net/>
Work: https://www.redpill-linpro.com/ <http://www.redpill-linpro.com/>