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

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