Hello,
In the Product to Model relationship, the Model is the child ItemType in the relationship. Because of this, the reference to the parent Product item will be stored in the source_id column. In a null relationship, the related_id will always be null.
To answer your second question, the config_id is a common id shared by all generations of a versionable item. The config_id is set to be equal to the id of the first generation of a versionable item. This allows for useful queries when you want to see the changes between different versions of the same item.
Chris
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Christopher Gillis
Aras Labs Software Engineer