Re: pgbench test failing on 14beta1 on Debian/i386

From: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
To: Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>
Cc: Michael Paquier <michael(at)paquier(dot)xyz>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Christoph Berg <myon(at)debian(dot)org>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: pgbench test failing on 14beta1 on Debian/i386
Date: 2021-05-19 11:07:43
Message-ID: alpine.DEB.2.22.394.2105191305270.536342@pseudo
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Hello Dean,

>>> Or, (3) remove this test? I am not quite sure what there is to gain
>>> with this extra test considering all the other tests with permute()
>>> already present in this script.
>>
>> Yes, I think removing the test is the best option. It was originally
>> added because there was a separate code path for larger permutation
>> sizes that needed testing, but that's no longer the case so the test
>> really isn't adding anything.
>
> Hmmm…
>
> It is the one test which worked in actually detecting an issue, so I would
> not say that it is not adding anything, on the contrary, it did prove its
> value! The permute function is expected to be deterministic on different
> platforms and architectures, and it is not.
>
> I agree that removing the test will hide the issue effectively:-) but ISTM
> more appropriate to solve the underlying issue and keep the test.
>
> I'd agree with a two phases approach: drop the test in the short term and
> deal with the PRNG later. I'm sooooo unhappy with this 48 bit PRNG that I may
> be motivated enough to attempt to replace it, or at least add a better
> (faster?? larger state?? same/better quality?) alternative.

Attached patch disactivates the test with comments to outline that there
is an issue to fix… so it is *not* removed.

I'm obviously okay with providing an alternate PRNG, let me know if this
is the prefered option.

--
Fabien.

Attachment Content-Type Size
pgbench-permute-test-1.patch text/x-diff 1.5 KB

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