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Data Model Questions /

How do I get all objects indirectly referred to by another?


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2 Posts   983 Views

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HansR

Community Member, 140 Posts

26 May 2011 at 9:48am

I have a collection of object classes with the following relations:
- Class 1 has many objects of Class 2
- Class 2 has many objects of Class 3
- Class 3 is just another data class

That is, a single Class 1 object has multiple Class 2 objects which in turn have multiple Class 3 objects.

How would I execute a query to get all objects of Class 3 that are indirectly referred to by Class 1? Can this be done efficiently? Or do I need to add a Class 1 has_one relation to class 3 (something which sounds ugly and would prefer to avoid)? This is an operation that might be done often, so it needs to be efficient.

Hans

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Willr

Forum Moderator, 5513 Posts

26 May 2011 at 8:02pm

Well you can't get all the Class 3 objects indirectly without getting the other classes. You'll need the id's. It depends on your dataset size, using the ORM (so ClassOne->Relationship()->Relationship() will return what you want but would be slow.

You could also use DataObject::get with a join clause (get Class 3, join on class 2) which would be pretty quick. I suggest you try with a simply join operation with DataObject get and see how performance goes. Cache if required. Next level in optimization is to denormalize your data, thus removing the need for joins.