| From: | Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, pgsql-hackers(at)lists(dot)postgresql(dot)org |
| Subject: | Re: Ensuring hash tuples are properly maxaligned |
| Date: | 2018-01-03 01:29:15 |
| Message-ID: | CAEepm=1oc+hY_Goh8onmLc1q3KjAFDSeZJ7Ea5wzUc30G4jKhA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Jan 3, 2018 at 2:20 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
>> But note that dsa_pointer can be wider than a regular pointer on
>> platforms without atomics support.
>
> Hm. I did not get that impression from the comments in dsa.h,
> but if it's true then this approach won't work --- and indeed the
> hash code would be actively broken in such a case, so it's a problem
> we must fix.
Maybe Andres is thinking of dsa_pointer_atomic? dsa_pointer is
normally the size of a pointer (well, really, the size of size_t),
though it could be *narrower* if you don't have atomics or ask for it
with USE_SMALL_DSA_POINTER
--
Thomas Munro
http://www.enterprisedb.com
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