Re: Fixed length data types issue

Gregory Stark wrote:
> Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
>
> > Bruce Momjian <bruce(at)momjian(dot)us> writes:
> > > Tom Lane wrote:
> > >> Either way, I think it would be interesting to consider
> > >>
> > >> (a) length word either one or two bytes, not four. You can't need more
> > >> than 2 bytes for a datum that fits in a disk page ...
> >
> > > That is an interesting observation, though could compressed inline
> > > values exceed two bytes?
> >
> > After expansion, perhaps, but it's the on-disk footprint that concerns
> > us here.
>
> I'm a bit confused by this and how it would be handled in your sketch. I
> assumed we needed a bit pattern dedicated to 4-byte length headers because
> even though it would never occur on disk it would be necessary to for the
> uncompressed and/or detoasted data.

Well, we have to expand the TOAST anyway in memory, so when we do that
we already give it the right length header.

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

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