"Jim C. Nasby" <[EMAIL PROTECTED]> writes:
> Dumb question... wouldn't getting down to 20 bytes buy us something?

Only on 32-bit machines, which are getting less interesting as database
servers every day.  (Just last night I was reading somebody opining that
the transition to 64-bit hardware would be effectively complete by 2008
... and he was talking about desktop PCs, not serious iron.)

BTW, the apparently useless byte after the 27- or 23-byte header
actually has some good use: in a table of up to 8 columns, you can
fit a null bitmap there "for free".  In a scheme that took us down
to 20 rather than 19 bytes, even a narrow table would pay the full
maxalign price for having a null.

I'm in favor of combining cmin/cmax/xvac to get us down to 23 bytes,
but I think anything beyond that is going to face a serious problem
of greatly increased cost for diminishing returns.

                        regards, tom lane

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