| 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: | 2024-05-08 22:07:22 |
| Message-ID: | CAApHDvp5Az4MA3r1REaV=NyTF=30qNhe+N=OWb5g_edAvS+rCA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, 9 May 2024 at 06:24, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> I like alternative-2.patch a lot better, not least because it
> only adds cycles when join removal actually fires. Basically
> this is putting the onus on the data structure modifier to
> cope with shared bitmapsets, rather than trying to say that
> sharing is disallowed.
>
> Thoughts?
I'm fine with this one as it's the same as what I already mentioned
earlier. I had imagined doing bms_del_member(bms_copy ... but maybe
the compiler is able to optimise away the additional store. Likely, it
does not matter much as pallocing memory likely adds far more overhead
anyway.
David
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