| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> |
| Cc: | John Naylor <johncnaylorls(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Nathan Bossart <nathandbossart(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, Yura Sokolov <y(dot)sokolov(at)postgrespro(dot)ru> |
| Subject: | Re: [PoC] Improve dead tuple storage for lazy vacuum |
| Date: | 2024-03-25 01:13:24 |
| Message-ID: | 2320443.1711329204@sss.pgh.pa.us |
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Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> writes:
> On Mon, Mar 25, 2024 at 1:53 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> I think the point here is that if you start with an arbitrary
>> non-negative shift value, the preceding loop may in fact decrement it
>> down to something less than zero before exiting, in which case we
>> would indeed have trouble. I suspect that the code is making
>> undocumented assumptions about the possible initial values of shift.
>> Maybe some Asserts would be good? Also, if we're effectively assuming
>> that shift must be exactly zero here, why not let the compiler
>> hard-code that?
> Sounds like a good solution. I've attached the patch for that.
Personally I'd put the Assert immediately after the loop, because
it's not related to the "Reserve slot for the value" comment.
Seems reasonable otherwise.
regards, tom lane
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