| From: | David Rowley <dgrowleyml(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Andrew Dunstan <andrew(at)dunslane(dot)net>, Richard Guo <guofenglinux(at)gmail(dot)com>, jian he <jian(dot)universality(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Revert: Remove useless self-joins *and* -DREALLOCATE_BITMAPSETS make server crash, regress test fail. |
| Date: | 2024-05-07 23:03:16 |
| Message-ID: | CAApHDvqRgYq8yL3GUj-1z2xPv6cLy7D4tjxhhijWnsHLOSukLg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, 8 May 2024 at 10:55, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> David Rowley <dgrowleyml(at)gmail(dot)com> writes:
> > REALLOCATE_BITMAPSETS was invented for this and IMO, it found exactly
> > the problem it was invented to find.
>
> Not in a way that gives me any confidence that we found *all* the
> problems.
Here are some statements I believe to be true:
1. If REALLOCATE_BITMAPSETS is defined then modifications to a
Bitmapset will make a copy and free the original.
2. If a query runs successfully without REALLOCATE_BITMAPSETS and
Assert fails due to an invalid Bitmapset when REALLOCATE_BITMAPSETS is
defined, then we have > 1 pointer pointing to the same set and not all
of them are being updated when the members are added/removed.
Given the above, I can't see what Bitmapset sharing problems we won't
find with REALLOCATE_BITMAPSETS.
Can you share the exact scenario you're worried that we won't find so
I can understand your concern?
David
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