Re: signal 11 segfaults with parallel workers

On Mon, Jul 31, 2017 at 5:41 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> writes:
>> There is already a "Parallel Worker" memory context defined by that
>> time. I think the issue is that multicorn library expects that
>> Transaction context to be defined by that time.
>
> It looks like multicorn supposes that a library's _PG_init function can
> only be called inside a transaction. That is broken with a capital B.
> We need not consider parallel query to find counterexamples: that
> means you can't preload multicorn using shared_preload_libraries,
> as that loads libraries into the postmaster, which never has and never
> will run transactions.
>
> Whatever it's trying to initialize in _PG_init needs to be done later.

Indeed, that's bad. I am adding in CC Ronan who has been working on
multicorn. At this stage, I think that you would be better out by
disabling parallelism.
--
Michael