Re: Ensuring hash tuples are properly maxaligned

Andres Freund <andres(at)anarazel(dot)de> writes:
> 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.

OK, then there's not a live bug, but I'm a bit tempted to get rid of
the data[] member anyway. It's not clear to me now that keeping it
results in net cleaner code. Thoughts?

regards, tom lane