| From: | Yuya Watari <watari(dot)yuya(at)gmail(dot)com> |
|---|---|
| To: | Ranier Vilela <ranier(dot)vf(at)gmail(dot)com>, David Rowley <dgrowleyml(at)gmail(dot)com> |
| Cc: | Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Making empty Bitmapsets always be NULL |
| Date: | 2023-06-22 08:49:34 |
| Message-ID: | CAJ2pMkZ5F7c_ddQpqT-89ZuE8sVV-zHsXWHcVuf=uwsGaPu-bw@mail.gmail.com |
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| Lists: | pgsql-hackers |
Hello,
On Thu, Jun 22, 2023 at 1:43 PM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
> > 3. Avoid enlargement when nwords is equal wordnum.
> > Can save cycles when in corner cases?
>
> No, you're just introducing a bug here. Arrays in C are zero-based,
> so "wordnum >= a->nwords" is exactly the correct way to check if
> wordnum falls outside the bounds of the existing allocated memory. By
> changing that to "wordnum > a->nwords" we'll fail to enlarge the words
> array when it needs to be enlarged by 1 element.
I agree with David. Unfortunately, some of the regression tests failed
with the v5 patch. These failures are due to the bug introduced by the
#3 change.
--
Best regards,
Yuya Watari
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