* Tom Lane <[EMAIL PROTECTED]> wrote: > "Peter Darley" <[EMAIL PROTECTED]> writes: > > I have a question about views: I want to have a fairly wide view (lots > > of > > columns) where most of the columns have some heavyish calculations in them, > > but I'm concerned that it will have to calculate every column even when I'm > > not selecting them. So, the question is, if I have 5 columns in a view but > > only select 1 column, is the system smart enough to not calculate the unused > > columns, > > It depends on what the rest of your view looks like. If the view is > simple enough to be "flattened" into the parent query then the unused > columns will disappear into the ether. If it's not flattenable then > they will get evaluated. You can check by seeing whether an EXPLAIN > shows a separate "subquery scan" node corresponding to the view. > (Without bothering to look at the code, an unflattenable view is one > that uses GROUP BY, DISTINCT, aggregates, ORDER BY, LIMIT, UNION, > INTERSECT, EXCEPT, probably a couple other things.)
What about functions ? I'm using several (immutable) functions for mapping IDs to names, etc. cu -- --------------------------------------------------------------------- Enrico Weigelt == metux IT service phone: +49 36207 519931 www: http://www.metux.de/ fax: +49 36207 519932 email: [EMAIL PROTECTED] cellphone: +49 174 7066481 --------------------------------------------------------------------- -- DSL ab 0 Euro. -- statische IP -- UUCP -- Hosting -- Webshops -- --------------------------------------------------------------------- ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
