Re: one column from huge view

On Thu, Jul 12, 2007 at 09:50:42AM +0100, Heikki Linnakangas wrote:
> Marcin Stępnicki wrote:
> >Let's say I've got a view with 100 columns and 1mln rows; some of them are
> >calculated "on the fly". For some reason I want only one column from
> >this view:
> >
> >select col1 from huge_view;
> >
> >Now, does PostgreSQL skip all the calculations from other columns and
> >executes this query faster then select * from huge_view?
> 
> In simple cases, yes. But for example, if you have a LEFT OUTER JOIN in 
> the view, the join is performed even if your query doesn't return any 
> columns from the outer relation. Also, if the calculation contains 
> immutable functions, it's not skipped.

Don't you mean "if the calculation contains VOLATILE functions,
it's not skipped"?

-- 
Michael Fuhr