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* Re: Tighten asserts on ParallelWorkerNumber a little bit
@ 2026-03-13 10:53 Bertrand Drouvot <[email protected]>
2026-03-14 14:53 ` Re: Tighten asserts on ParallelWorkerNumber a little bit Tomas Vondra <[email protected]>
0 siblings, 1 reply; 2+ messages in thread
From: Bertrand Drouvot @ 2026-03-13 10:53 UTC (permalink / raw)
To: Tomas Vondra <[email protected]>; +Cc: PostgreSQL Hackers <[email protected]>
Hi,
On Thu, Mar 12, 2026 at 07:59:43PM +0100, Tomas Vondra wrote:
> Hi,
>
> While hacking on something I happened to notice a couple asserts on
> ParallelWorkerNumber when collecting shared instrumentation:
>
> Assert(ParallelWorkerNumber <= node->shared_info->num_workers);
>
> This is not quire right, because num_workers is used to size arrays
> indexed by ParallelWorkerNumber. And the comment in parallel.c also
> claims (ParallelWorkerNumber < num_workers).
>
> So AFAICS the assert(s) should be
>
> Assert(ParallelWorkerNumber < node->shared_info->num_workers);
I think that you're right. It looks like the first one has been introduced
by bf11e7ee2e3 and then the others are probably copy/paste.
> I don't think we had issues with this not catching a bug. But it may be
> a bit misleading, so worth fixing and (probably) backpatching.
I do agree.
With that patch applied, the remaining one:
$ git grep "<=.*num_workers"
src/backend/executor/nodeGatherMerge.c: Assert(nreaders <= castNode(GatherMerge, gm_state->ps.plan)->num_workers);
does not need to be fixed, so I think that your patch does not miss any and
LGTM.
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: Tighten asserts on ParallelWorkerNumber a little bit
2026-03-13 10:53 Re: Tighten asserts on ParallelWorkerNumber a little bit Bertrand Drouvot <[email protected]>
@ 2026-03-14 14:53 ` Tomas Vondra <[email protected]>
0 siblings, 0 replies; 2+ messages in thread
From: Tomas Vondra @ 2026-03-14 14:53 UTC (permalink / raw)
To: Bertrand Drouvot <[email protected]>; +Cc: PostgreSQL Hackers <[email protected]>
On 3/13/26 11:53, Bertrand Drouvot wrote:
> ...
>
>> So AFAICS the assert(s) should be
>>
>> Assert(ParallelWorkerNumber < node->shared_info->num_workers);
>
> I think that you're right. It looks like the first one has been introduced
> by bf11e7ee2e3 and then the others are probably copy/paste.
>
>> I don't think we had issues with this not catching a bug. But it may be
>> a bit misleading, so worth fixing and (probably) backpatching.
>
> I do agree.
>
> With that patch applied, the remaining one:
>
> $ git grep "<=.*num_workers"
> src/backend/executor/nodeGatherMerge.c: Assert(nreaders <= castNode(GatherMerge, gm_state->ps.plan)->num_workers);
>
> does not need to be fixed, so I think that your patch does not miss any and
> LGTM.
>
Thanks. Pushed and backpatched.
--
Tomas Vondra
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2026-03-13 10:53 Re: Tighten asserts on ParallelWorkerNumber a little bit Bertrand Drouvot <[email protected]>
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