Re: Combo xids

On 01.06.2013 11:22, Simon Riggs wrote:
> What is the benefit?
> Merging xmin/xmax would save 4 bytes per row. On servers with 8 byte
> word length, that means that we'd save 8 bytes per row for tables that
> have between 9 and 40 columns. Which is the majority of tables.

Hmm, it would probably be much easier to squeeze, say, one byte from the 
tuple header, than full four bytes. Then you could store store a null 
bitmap for upto 16 columns, without crossing the 24 byte mark. That 
would already get you much of the benefit.

- Heikki