Re: Fixed length data types issue

Gregory Stark wrote:
> Tom Lane <tgl@sss.pgh.pa.us> writes:
> 
> > Bruce Momjian <bruce@momjian.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@momjian.us EnterpriseDB    http://www.enterprisedb.com
 + If your life is a hard drive, Christ can be your backup. +