Re: PostgreSQL Arrays and Performance

On Sun, Jan 08, 2006 at 10:22:22AM +0100, Marc Philipp wrote:
> > This sounds like it has more to do with inadequate freespace map
> > settings than use of arrays. Every update creates a dead tuple, and
> > if
> > it is large (because the array is large) and leaked (because you have
> > no
> > room in your freespace map), that would explain a rapidly increasing
> > database size.
>
> Can you tell me more about free-space map settings? What exactly is the
> free-space map? The information in the documentation is not very
> helpful. How can dead tuples leak?

http://www.pervasive-postgres.com/lp/newsletters/2005/Insights_opensource_Nov.asp#3
is an article I wrote that might clear things up.
http://www.pervasive-postgres.com/lp/newsletters/2005/Insights_opensource_Dec.asp#2
might also be an interesting read, though it's just about MVCC in
general.
--
Jim C. Nasby, Sr. Engineering Consultant jnasby(at)pervasive(dot)com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461