Re-design relational properties

[kettanaito]

Issues

Relational properties are all over the place

First, when creating a relation in the model definition using oneOf/manyOf functions, what you effectively create is a draft for the future relation. Until the relation has access to the entire dictionary (map of models), it cannot know what primaryKey the referenced model has.

This implies that any defined relation must be "evolved".

Unapparent how to re-define relational properties

When updating entities via update/updateMany, you can also update relational properties (support added in #126). However, the implementation for that update is unapparent and seems unsemantic to the Relation class. If forces the updateEntity function to require access to the model definition and the database in order to create a new relational property (the getter it defines on the entity queries the database for the given referenced model's primary key and other data).

Manual retrieval of the referenced model primary key

The relation definition (the one you provide in the model) doesn't know about the referenced model's primary key.

data/src/model/defineRelationalProperties.ts

Line 63 in 9f88f0d

return entityRef[relation.primaryKey]

What's worse, is that in the case of manyOf relations, the referenced entities are stored in a list. So to get an idea of the primary key of the referenced model you have to get the first entity from the referenced list:

data/src/model/updateEntity.ts

Lines 67 to 71 in 9f88f0d

	// In "manyOf" relation the previous value will be an array of entities.
	// Get the first entity and its primary key property name.
	const primaryKey = [].concat(prevValue)[0][
	InternalEntityProperty.primaryKey
	]

Primary key property name cannot be changed on runtime, it's a fixed string. It'd make much more sense to resolve that primary key name when relation definition becomes a relation (is produced). That way there'd be no need to look up primary keys anymore.