Re: HOT for PostgreSQL 8.3

Ühel kenal päeval, P, 2007-02-11 kell 12:35, kirjutas Tom Lane:
> Hannu Krosing <hannu@skype.net> writes:
> > What if we would just reuse the root tuple directly instead of turning
> > it into a stub ?
> > This would create a cycle of ctid pointers, which changes the lookup
> > process from 'follow ctid chaint until the end' to 'follow the tid chain
> > until you reach the start'.
> 
> How do you know which one is newest? 

By xmin,cmin of course .

> What happens when you have to put a newer version off-page for lack of space?

Then this scheme won't work.

How about adding a new 2-byte field to header for in-page c_tid poiner
for HOT ?

It grows header from 26 to 28 bytes, but for MAXALIGN=4 the space usage
would stay the same.

>             regards, tom lane
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Hannu Krosing
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