Re: [HACKERS] SERIALIZABLE with parallel query

On Thu, Mar 8, 2018 at 10:28 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> +SerializableXactHandle
> +ShareSerializableXact(void)
> +{
> + Assert(!IsParallelWorker());
> +
> + return MySerializableXact;
> +}
>
> Uh, how's that OK? There's no rule that you can't create a
> ParallelContext in a worker. Parallel query currently doesn't, so it
> probably won't happen, but burying an assertion to that effect in the
> predicate locking code doesn't seem nice.

Hmm. I suppose you could have a PARALLEL SAFE function that itself
launches parallel workers explicitly (not via parallel query), and
they should inherit the same SERIALIZABLEXACT from their parent and
that should all just work.

> Is "sxact" really the best (i.e. clearest) name we can come up with
> for the lock tranche?

Yeah, needs a better name.

I have some lingering uncertainty about this patch and we're out of
time, so I moved it to PG12 CF1. Thanks Haribabu, Robert, Amit for
the reviews and comments so far.

--
Thomas Munro
http://www.enterprisedb.com