Re: Fixed length data types issue

Tom Lane wrote:
> Bruce Momjian <bruce(at)momjian(dot)us> writes:
> > No one has mentioned that we page value on disk to match the CPU
> > alignment. This is done for efficiency, but is not strictly required.
>
> Well, it is unless you are willing to give up support of non-Intel CPUs;
> most other popular chips are strict about alignment, and will fail an
> attempt to do a nonaligned fetch.
>
> The only way we could pack stuff without alignment is to go over to the
> idea that memory and disk representations are different --- where in
> this case the "conversion" might just be a memcpy to a known-aligned
> location. The performance costs of that seem pretty daunting, however,
> especially when you reflect that simply stepping over a varlena field
> would require memcpy'ing its length word to someplace.

Agreed, but I thought I would point it out.

--
Bruce Momjian bruce(at)momjian(dot)us
EnterpriseDB http://www.enterprisedb.com

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