Re: Automatic free space map filling

On Thu, Mar 02, 2006 at 10:05:28AM -0500, Tom Lane wrote:
> Hannu Krosing <hannu@skype.net> writes:
> > hel kenal peval, N, 2006-03-02 kell 09:53, kirjutas Zeugswetter
> > Andreas DCP SD:
> >> Ok, we cannot reuse a dead tuple. Maybe we can reuse the space of a dead
> >> tuple by reducing the tuple to it's header info.
> 
> Andreas' idea is possibly doable but I am not sure that I see the point.
> It does not reduce the need for vacuum nor the I/O load imposed by
> vacuum.  What it does do is bias the system in the direction of
> allocating an unreasonably large number of tuple line pointers on a page
> (ie, more than are useful when the page is fully packed with normal
> tuples).  Since we never reclaim such pointers, over time all the pages
> in a table would tend to develop line-pointer-bloat.  I don't know what
> the net overhead would be, but it'd definitely impose some aggregate
> inefficiency.

What would be involved in reclaiming item pointer space? Is there any
reason it's not done today? (I know I've been bit once by this...)
-- 
Jim C. Nasby, Sr. Engineering Consultant      jnasby@pervasive.com
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461