From: | Andres Freund <andres(at)anarazel(dot)de> |
---|---|
To: | Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)lists(dot)postgresql(dot)org |
Subject: | Re: Ensuring hash tuples are properly maxaligned |
Date: | 2018-01-03 01:33:00 |
Message-ID: | 20180103013300.cf4jermw5ksygm7l@alap3.anarazel.de |
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Lists: | pgsql-hackers |
On 2018-01-03 14:29:15 +1300, Thomas Munro wrote:
> 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
Yep, I was.
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