Schema: support validation/referential integrity for objectid types

[inactivist]

"Would be helpful" if the schema supported referential integrity validation for objectid types during POST/PATCH ops.

For example, in eve-demo:

works = {
    'schema': {
        # snip
        'owner': {
            'type': 'objectid',
            'required': True,
        },
    }

There is no (simple) way to ensure that the works.owner value exists in the people collection. Currently, one must implement a custom Validator class in order to enforce basic RI rules.

A simplistic approach would allow schema-based specification of the referenced collection name, and if the value doesn't exist, raise an exception.

A more flexible approach would allow optional specification of a callable validation method, thus providing more sophisticated business rules. A default behavior would be to verify existence in the referenced collection per the 'simplistic' approach.

[inactivist]

This raises a related feature: Support for a list of objectid types validated against some collection (all objectid items in the list must exist in some collection.

Should this require writing a custom Validator? (Using a custom Validator may be the correct solution, but I don't know enough to decide.)

This case could be handled in the application using a callable validation function if that capability exists.

[nicolaiarocci]

Thanks, this is needed indeed. I'm going work on it in a few days, as soon as I'm done with the first documentation draft.

[cudevmaxwell]

Working on this now.

[nicolaiarocci]

How about somethig like this:

'owner': {
            'type': 'objectid',
            'required': True,
            'data_relation': {
                'resource': 'people',
                'field': '_id'
            }
        },

At the cost of a little complexity The data_relation keyword would allow to specify both the parent collection and the linked field, allowing for some flexibility (you can reference non-primary key fields).

[inactivist]

That looks like a simple and workable solution.