| 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 22:47:32 |
| Message-ID: | CAApHDvrvcJd2DCAV0vDKmRxp5tvXq3=+RwhRns4OjoHQ1UbDEg@mail.gmail.com |
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On Wed, 8 May 2024 at 10:40, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> David Rowley <dgrowleyml(at)gmail(dot)com> writes:
> > We could make the policy copy-on-modify. If you put bms_copy around
> > the bms_del_member() calls in remove_rel_from_query(), does it pass
> > then?
>
> Didn't test, but that route seems awfully invasive and fragile: how
> will we find all the places to modify, or ensure that the policy
> is followed by future patches?
REALLOCATE_BITMAPSETS was invented for this and IMO, it found exactly
the problem it was invented to find.
Copy-on-modify is our policy for node mutation. Why is it ok there but
awfully fragile here?
David
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