Re: Postgres crashes at memcopy() after upgrade to PG 13.

On Tue, Mar 16, 2021 at 5:01 AM Avinash Kumar
<avinash(dot)vallarapu(at)gmail(dot)com> wrote:
> I am afraid that it looks to me like a deduplication bug but not sure how this can be pin-pointed. If there is something I could do to determine that, I would be more than happy.

That cannot be ruled out, but I don't consider it to be the most
likely explanation. The index in question passes amcheck verification,
which includes verification of the posting list tuple structure, and
even includes making sure the index has an entry for each row from the
table. It's highly unlikely that it is corrupt, and it's hard to see
how you get from a non-corrupt index to the segfault. At the same time
we see that some other index is corrupt -- it fails amcheck due to a
cross-level inconsistency, which is very unlikely to be related to
deduplication in any way. It's hard to believe that the problem is
squarely with _bt_swap_posting().

Did you actually run amcheck on the failed-over server, not the original server?

Note that you can disable deduplication selectively -- perhaps doing
so will make it possible to isolate the issue. Something like this
should do it (you need to reindex here to actually change the on-disk
representation to not have any posting list tuples from
deduplication):

alter index idx_id_mtime set (deduplicate_items = off);
reindex index idx_id_mtime;

--
Peter Geoghegan