I can’t come up with a better case.  I don’t recall ever using them.   As Paul 
said, it would have to be a read only column.  This might have made more sense 
years ago when offloading processing to the database made sense.  If it ever 
really did.

For more data inconsistency fun, you can flatten attributes too!

Chuck


From: 
<webobjects-dev-bounces+chill=gevityinc....@lists.apple.com<mailto:webobjects-dev-bounces+chill=gevityinc....@lists.apple.com>>
 on behalf of Paul Hoadley <pa...@logicsquad.net<mailto:pa...@logicsquad.net>>
Date: Tuesday, January 12, 2016 at 4:38 PM
To: Theodore Petrosky <tedp...@yahoo.com<mailto:tedp...@yahoo.com>>
Cc: WebObjects-Dev 
<webobjects-dev@lists.apple.com<mailto:webobjects-dev@lists.apple.com>>
Subject: Re: when is derived column resolved

Hi Ted,

On 13 Jan 2016, at 10:39 am, Theodore Petrosky 
<tedp...@yahoo.com<mailto:tedp...@yahoo.com>> wrote:

1. should I go back to creating a method on Entity Person fullName that returns 
a string concatenating first and last names?

Probably, yes.

OK, that’s a plan, when do you feel it’s appropriate to use a derived column?

I am reasonably sure we use them nowhere. I think you would want to limit their 
use to read-only attributes (or you will immediately hit the freshness issue 
you’ve already discovered), and quite probably to transformations that are 
better done in the database than in Java. (Pulling an example out of the air: 
maybe some kind of geospatial result that you can get from PostGIS. But even 
then, if you can write to the columns the result depends on, you’ve got a 
problem again.) Does anyone have a solid use case for derived attributes that 
they actually use in the real world?


--
Paul Hoadley
http://logicsquad.net/



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