Re: BUG #17116: Assert failed in SerialSetActiveSerXmin() on commit of parallelized serializable transaction

On Wed, Jul 28, 2021 at 9:00 AM Alexander Lakhin <exclusion(at)gmail(dot)com> wrote:
> Thanks! With the new fix applied, my multiple installcheck test survives
> 100+ iterations.

Thanks.

Here's an updated version. No code change, but now with a change to
serializable-parallel-2.sql so that the second assertion you mentioned
fails on unpatched master. The intention of that test was to exercise
the SXACT_FLAG_RO_SAFE optimisation in a parallel query, and it did
that, but in a sort of degenerate way: sequential scans acquire
predicate locks *before entering parallel mode*, so the optimisation
is triggered immediately. This version triggers the optimisation in a
parallel worker, and then the final cleanup happens in the leader,
which is the interesting case.

> (Except for read-only-anomaly-3, that causes another
> assertion fail but I believe that it's not related to the initial issue
> and deserves another bug report.)

Huh. I tried and failed to find that one with concurrent runs. I'll
wait for your next report before I do anything, just in case there's a
connection.