Andrus Adamchik wrote:
> Working on the plan of TopLink -> Cayenne conversion I noticed that I will
> need inheritance support in the mapping. Out of all types of inheritance
> that are used in O/R design (vertical, horizontal, single table), I am
> targeting "single table" for now.
+1! While vertical is conceptually nice it's a bitch to implement
correctly and can be slow because of excessive joins, single-table is
definitely the easiest and most practical to use. I've never used
horizontal except for tests.
> GUI is closer to TopLink rather than EOModeler, in that you can't select an
> arbitrary qualifier for each of the subclass entities, but rather have a
> designated "class indicator" column. This is to make the whole thing more
> deterministic and avoid conflicting qualifiers (so that rows in the database
> never resolve to more than one entity). Internally we may still use
> Expression for this.
Nice. When I first saw the destination class hint in the TopLink Workbench
I was sceptical, but it really does solve many ambiguities and makes
things more explicit for the modeler.
Holger
This archive was generated by hypermail 2.0.0 : Wed Jan 08 2003 - 14:41:03 EST