Re: Issue with the PRNG used by Postgres

Thank you Robert.
I am in the process of patching this.
-Parag

On Wed, Apr 10, 2024 at 7:43 AM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

> On Tue, Apr 9, 2024 at 5:05 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
> > ISTM that the fix here is to not use a spinlock for whatever the
> contention is
> > on, rather than improve the RNG.
>
> I'm not convinced that we should try to improve the RNG, but surely we
> need to put parentheses around pg_prng_double(&pg_global_prng_state) +
> 0.5. IIUC, the current logic is making us multiply the spin delay by a
> value between 0 and 1 when what was intended was that it should be
> multiplied by a value between 0.5 and 1.5.
>
> If I'm reading this correctly, this was introduced here:
>
> commit 59bb147353ba274e0836d06f429176d4be47452c
> Author: Bruce Momjian <bruce(at)momjian(dot)us>
> Date: Fri Feb 3 12:45:47 2006 +0000
>
> Update random() usage so ranges are inclusive/exclusive as required.
>
> --
> Robert Haas
> EDB: http://www.enterprisedb.com
>