On Fri, 5 Mar 2004, Jeff wrote:
> Is there any performance advantage to using a fixed width row (with PG)?
As far as I know there is only a small win when you want to extract some
field from a tuple and with variable width fields you have to walk to the
correct field. But this is a small performance problem unless you have
very many variable size columns in the table.
> different databases and we have also some custom software here that
> uses fixed width rows to be able to hit row N in O(1)
This can not happen in pg since there is no row N. Every transaction can
have a different view of the table, some rows are visible and some others
are not. To find row N you have to walk from the start and inspect every
tuple to see if it's visible to this transaction or not.
--
/Dennis Björklund