Re: Index speeds up one row table (why)?

On Sat, May 31, 2003 at 17:17:38 -0600,
  Dave E Martin XXIII <postgresql-to.dave@dave.to> wrote:
> Speaking of which, since the row is locked with select for update (so it 
> can't be involved in any other transactions anyway) and the change 
> doesn't change the length of the row, can't it just be updated in-place, 
> or would that break something else? (pardon if this is answered already, 
> me thinks its time to go reread the todo's and the architecture 
> documents...)

No. Select for update only blocks writers, not readers. This has important
performance advantages. You might want read the documentation on MVCC.
Tom Lane also has a copy of a presentation he made on the web somewhere.
I have it read it but it has gotten favorable mention on the lists before.