Re: vacuum, performance, and MVCC

PFC wrote:
> 
> > My idea is that if an UPDATE places the new tuple on the same page as
> > the old tuple, it will not create new index entries for any indexes
> > where the key doesn't change.
> 
>     Basically the idea behind preventing index bloat by updates is to have  
> one index tuple point to several actual tuples having the same value.
>     

The idea is not to avoid index bloat, but to allow heap reuse, and having
one index entry for multiple versions of an UPDATEd row is merely an
implementation detail.

--  Bruce Momjian   bruce@momjian.us EnterpriseDB    http://www.enterprisedb.com
 + If your life is a hard drive, Christ can be your backup. +