Re: Planning aggregates which require sorted or distinct

Simon Riggs wrote:

> I'm working on modifying Tuplestore that will allow you to store the
> last N tuples, rather than all previous input. This is specifically
> designed to allow Merge Join to do Mark/Restore without materializing
> the whole sort set. This can also be used to materialize Windows (i.e.
> <window clause> in SQL:2003), so you can store the current row plus n
> PRECEDING and/or n FOLLOWING rows as appropriate.

Interesting.  This could also be used to implement the "partial sort"
stuff that Oleg is so interested in, and in which I believe Greg Stark
was also interested.

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support