Michael Fuhr wrote:
> 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"?
Yes, thanks for the correction.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com