Re: [HACKERS] recent deadlock regression test failures

Kevin Grittner <kgrittn@gmail.com> writes:
> On Mon, Apr 10, 2017 at 9:28 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> I notice that the safe-snapshot code path is not paying attention to
>> parallel-query cases, unlike the lock code path.  I'm not sure how
>> big a deal that is...

> Parallel workers in serializable transactions should be using the
> transaction number of the "master" process to take any predicate
> locks, and if parallel workers are doing any DML work against
> tuples, that should be using the master transaction number for
> xmin/xmax and serialization failure testing.

Right, but do they record the master's PID rather than their own in
the SERIALIZABLEXACT data structure?

Maybe it's impossible for a parallel worker to acquire its own
snapshot at all, in which case this is moot.  But I'm nervous.
        regards, tom lane