> > If now we'll add 6 bytes to header then
> > offsetof(HeapTupleHeaderData, t_bits) will be 32 and for
> > no-nulls tuples there will be no difference at all
> > (with/without additional 6 bytes), due to double alignment
> > of header. So, the choice is: new feature or more compact
> > (than current) header for tuples with nulls.
>
> That's a tough one. What do other DB's have for row overhead?
>
Informix has a per page overhead of 36 bytes (per 4k or 2k page)
+ 4 bytes per row and page
Data resides on: Home page, big remainder page, remainder page.
no length or precision byte per column for fixed width/precision fields.
It has a maximum of 255 rows per page (4k page, 11 bytes min rowsize)
Andreas