Re: Disable parallel query by default

On Tue, May 13, 2025 at 4:37 PM Scott Mead <scott(at)meads(dot)us> wrote:

> I'll open by proposing that we prevent the planner from automatically
> selecting parallel plans by default

That seems a pretty heavy hammer, when we have things like
parallel_setup_cost that should be tweaked first.

The recommendation that I give to users is pretty straightforward: "Disable
> automatic parallel query, enable it for queries where you find substantial
> savings and can control the rate of execution." I always tell users that
> if they're using parallel query for anything that should execute in less
> than 5 minutes, they're probably pushing on the wrong tuning strategy as
> the load induced by the parallel query infrastructure is likely going to
> negate the savings that they're getting.
>

Five minutes?! That's not been my experience. Not claiming parallelism is
perfect yet, but there are plenty of parallel performance savings under the
five minute mark.

Cheers,
Greg

--
Crunchy Data - https://www.crunchydata.com
Enterprise Postgres Software Products & Tech Support