If the association is optional, Hibernate has no way of knowing if an address exists for a given person without issuing a query. So it can’t populate the address field with a proxy, because there could be no address referencing the person, and it can’t populate it with null, because there might be an address … Read more
EF Code First supports 1:1 and 1:0..1 relationships. The latter is what you are looking for (“one to zero-or-one”). Your attempts at fluent are saying required on both ends in one case and optional on both ends in the other. What you need is optional on one end and required on the other. Here’s an … Read more
To check if the (OneToOne) relation exists or not, you can use the hasattr function: if hasattr(request.user, ‘type1profile’): # do something elif hasattr(request.user, ‘type2profile’): # do something else else: # do something else
Well, there’s essentially two questions here: What is the difference (in general) between one to one, many to many, and foreign key relations What are their differences specific to Django. Both of these questions are quite easily answered through a simple Google search, but as I cannot find an exact dupe of this question on … Read more
A 1:1 relationship typically indicates that you have partitioned a larger entity for some reason. Often it is because of performance reasons in the physical schema, but it can happen in the logic side as well if a large chunk of the data is expected to be “unknown” at the same time (in which case … Read more
First off, some clarifications to KLE‘s answer: Unconstrained (nullable) one-to-one association is the only one that can not be proxied without bytecode instrumentation. The reason for this is that owner entity MUST know whether association property should contain a proxy object or NULL and it can’t determine that by looking at its base table’s columns … Read more