Re: Slow GRANT ROLE on PostgreSQL 16 with thousands of ROLEs

On Thu, Mar 21, 2024 at 8:10 AM alex work <alexwork033@gmail.com> wrote:

> We encounter slow `GRANT ROLES` only on PostgreSQL 16 instances up to 42
> seconds
> in production, the client process at PostgresSQL would use 100% of the
> CPU. [...]
>
Using ROLE `acc`, grant `d_` ROLE to a session ROLE:
> real    0m7.579s [...]

PostgreSQL 15
> Using ROLE `acc`, grant `d_` ROLE to a session ROLE:
> real    0m0.077s
>

Ouch, that's a ~ 100x regression. Thanks for the write-up, that's worrying.
We don't have as many ROLEs, but we do have plenty, so this is worrying.

On top of the v16 ROLE changes breaking on ROLE logic, which was fine prior
(v12-v15).
We've paused for now our planned v16 upgrade, until we have more time to
adapt.

Like you, I welcome the changes. But it turns out more expensive to adapt
to them.
And your report certainly makes me wonder whether we should hold off until
that perf regression is addressed.

Thanks, --DD