Re: Remove xmin and cmin from frozen tuples

On Wed, Sep 07, 2005 at 01:20:27PM -0400, Tom Lane wrote:

> Anyway the fundamental insight has been completely lost here.  The
> original point was that cmin and cmax are only interesting within the
> originating transaction, and not to anyone else, and thus perhaps don't
> need to be kept in permanent storage; while xmin/xmax are different
> animals because they *are* of interest to other transactions.

I'm curious to know how can you store the cmin/cmax pair completely out
of the tuple.  It's easy to see how to store a single identifier in each
tuple that would be an index to a structure in local memory.  However,
to eliminate both you'd have to keep a list of all tuples you have
created or obsoleted, with the cmin and cmax of each.  This seems like
an awful amount of memory.

-- 
Alvaro Herrera -- Valdivia, Chile         Architect, www.EnterpriseDB.com
"I can't go to a restaurant and order food because I keep looking at the
fonts on the menu.  Five minutes later I realize that it's also talking
about food" (Donald Knuth)