Re: [HACKERS] strange parallel query behavior after OOM crashes - Mailing list pgsql-hackers

On Mon, Apr 10, 2017 at 7:17 PM, Tomas Vondra
<tomas.vondra@2ndquadrant.com> wrote:
> At first I was like 'WTF? Why do we need a new GUC just becase of an
> assert?' but you're actually not adding a new GUC parameter, you're adding a
> constant which is then used as a max value for max for the two existing
> parallel GUCs.
>
> I think this is fine.

I think it is pretty odd-looking.  As written, it computes an unsigned
-- and therefore necessarily non-negative -- value into a signed --
and thus possibly neative -- value only to pass it back to abs() to
make sure it's not negative:

+       Assert(!parallel ||
abs((int)(BackgroundWorkerData->parallel_register_count -
+                 BackgroundWorkerData->parallel_terminate_count)) <=
+                               MAX_PARALLEL_WORKER_LIMIT);

I think we can just say

Assert(!parallel || BackgroundWorkerData->parallel_register_count -
BackgroundWorkerData->parallel_terminate_count <= MAX_PARALLEL_WORKER_LIMIT);

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company