Coarse-grained object Design for Performance

Question

Hi,
I’ve several 1-1 mapping between one coarse-grained object with several fine grained objects. In the DB all the fine-grained objects are stored in separate table. In my application the relationship between coarse-grained object and fine-grained objects will not be modified. In this scenario, for good performance which solution is better?
Maintaining the 1-1 mapping between coarse-grained object and fine-grained objects OR adding all the attribute from the fine-grained objects into the coarse-grained object.
Thanks
-Mani

Answer 1

Mani,
The answer depends upon the data usage in your application.
If these fine grained read-only objects are shared between your coarse grain objects then it may be more optimal to keep them as separate classes with 1:1 relationships. If these read-only classes are also of fixed and reasonable quantity (reference data) you could also pre-fetch them all into a full cache (identity map). Then as each course grain object is read the 1:1 relationships can be resolved in memory without additional queries.
If you combine these objects all into one coarse gain object then you will have to pay the cost of a more complex multi-table join on each read. This may be more efficient if the fine grain objects are never or rarely shared between coarse grain objects. To be sure you will want to check with your DBA to see what they can measure as being more optimal for the given schema.
If these are shared and/or reference data then you may also want to consider marking them as read-only in the project. That way they will not be considered for change tracking in the UnitOfWork. This should also provide an additional performance boost.
Doug