Re: TOAST code ignores freespace (was Tweak TOAST code)

On Mon, 2010-05-03 at 23:36 -0400, Jan Wieck wrote:

> Suppose we had something similar to the NULL value bitmap, specifying 
> plain or compressed values (not TOAST references), that are moved to a
> shadow tuple inside the toast table. Suppose further we had some 
> statistics about how often attributes appear in a qualification (i.e. 
> end up in a scan key or scan filter or other parts of the qual 
> expression list). Not sure, maybe we even want to know how often or 
> seldom an attribute is heap_getattr()'d at all. Those don't need to be
> accurate counts. Small random samples will probably do. ANALYZE could 
> evaluate those statistics and adjust the "shadow" storage settings per
> attribute accordingly.
> 
> I can imagine many applications, where this would shrink the main
> tuples to almost nothing at all.

Automatic vertical partitioning. Like it. 

TODO item for further detailed research.

-- Simon Riggs           www.2ndQuadrant.com