On Wed, Aug 8, 2018 at 7:40 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Anyway, "VACUUM FULL pg_class" should be expected to corrupt
>> pg_class_oid_index when we happen to get a parallel build, since
>> pg_class is a mapped relation, and I've identified that as a problem
>> for parallel CREATE INDEX [2]. If that was the ultimate cause of the
>> issue, it would explain why only REL_11_STABLE and master are
>> involved.
>
> Oooh ... but pg_class wouldn't be big enough to get a parallel
> index rebuild during that test, would it?
Typically not, but I don't think that we can rule it out right away.
"min_parallel_table_scan_size = 0" will make it happen, and that
happens in quite a few regression tests. Though that doesn't include
vacuum.sql.
The animals mandrill, mantid and lapwing are all
"force_parallel_mode=regress", according to their notes. That actually
isn't enough to force parallel CREATE INDEX, though I tend to think it
should be. I don't see anything interesting in their "extra_config",
but perhaps "min_parallel_table_scan_size = 0" got in some other way.
I don't know all that much about the buildfarm client code, and it's
late.
--
Peter Geoghegan