On Tue, Apr 3, 2018 at 10:48 PM, Michael Banck <michael.ba...@credativ.de> wrote:
> Hi, > > 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 > to > > 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 > afterwards. > > 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? -- Magnus Hagander Me: https://www.hagander.net/ <http://www.hagander.net/> Work: https://www.redpill-linpro.com/ <http://www.redpill-linpro.com/>
