Re: pgsql: Reorder EPQ work, to fix rowmark related bugs and improve effici

Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> On 2019-Sep-09, Tom Lane wrote:
>> It appears to me that this is indeed a case of notice-reporting
>> timing problems in isolationtester, since these WARNING messages
>> are handled the same way as notices.  I want to try to reproduce
>> manually on prairiedog to confirm that, but it seems like a pretty
>> likely explanation.

Yeah, seems confirmed.  I ran forty cycles of eval-plan-qual
without a failure with current HEAD.  I then reverted 30717637c,
and eval-plan-qual fell over six times out of six, with the same
diffs shown in the buildfarm report.  So that patch is definitely
a prerequisite to making this version of eval-plan-qual stable.

>> On balance I'm inclined to back-patch both changes.  Thoughts?

> As well as a28e10e82e54, I suppose.  I agree with keeping the tool
> similar across branches, if we're going to do this.

Hm, good point.  My first thought was that a28e10e82e54 is just
cosmetic, but it isn't entirely, because it suppresses notice
reports on the control connection.  That means it might actually
be a prerequisite to having stable output with ebd499282 (the
change of client_min_messages).

After reviewing the git log a little more, I'm inclined to think
we should only back-patch this stuff to 9.6, which is where 38f8bdcac
("Modify the isolation tester so that multiple sessions can wait")
and a number of follow-up patches came in.  That was enough of a
quantum jump in flexibility that it'd likely limit our ability to
back-patch tests further than that anyway.  Also I don't think the
patches mentioned here would apply without that ...

            regards, tom lane