Re: Fixed length data types issue

Gregory Stark wrote:
> Bruce Momjian <bruce(at)momjian(dot)us> writes:
>
> > I think it would be good to see if we can extend the varlena data types
> > to support a shorter header for storing short byte values. Looking at
> > the header now we have:
>
> This isn't the first time we've been down that route. There were some
> extensive discussions a while back. I think there were even patches.
> I don't remember why it was eventually rejected. I suspect it simply got too
> complex.
>
> But I think this is a dead-end route. What you're looking at is the number "1"
> repeated for *every* record in the table. And what your proposing amounts to
> noticing that the number "4" fits in a byte and doesn't need a whole word to
> store it. Well sure, but you don't even need a byte if it's going to be the
> same for every record in the table.
>
> If someone popped up on the list asking about whether Postgres compressed
> their data efficiently if they stored a column that was identical throughout
> the whole table you would tell them to normalize their data.

I am confused. You don't want to shrink the header but instead compress
duplicate values in the same row to a single entry?

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

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