Getting in 3.0 mode for a while. I would like to support SQL (or
arbitrary user-defined) functions in Cayenne Expressions. Here is
some ideas:
http://objectstyle.org/confluence/display/CAY/Expression+Functions
As I mentioned on Wiki, what prompted me to look closer into this is
realization that there is no way other than DerivedDbEntity (and
SQLTemplate of course) to define a derived column and do ORDER BY on
it. The expression in question was "case when X>0 then (Y/X) else 0
end". Seems like support for functions in qualifiers and orderings
(of which Expression is a common abstraction) should be a nice fix to
that.
BTW, I thought of a WebObjects-like solution (http://tinyurl.com/
nbats) of defining the SQL script right in the column
(DerivedDbEntity works sort of like this). At the end I figured it is
not good at all, as it ends up being a read-only attribute, that gets
out of sync with the attributes it is derived from if the object is
updated... All very confusing and hard to use.
Andrus
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