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tianshu 2019-12-16T07:35:11.004600Z
Hi, folks. I'm new to DataScript, there's one confuse me while learning. I saw :db/id is used at entity-id and all the relations are built upon this. But in some case, the data from server (backed by sql) often looks like :user/id, that is not a global unique id. And this user/id is used for relationship. How can I simplify here?
cjsauer 2019-12-16T20:38:22.019500Z
@doglooksgood if I understand correctly, I’d believe you’d model this by using a schema like:
{:user/id {:db/unique :db.unique/identity}}
(d/transact! conn [{:user/id 123}, {:user/id 789}])
:user/best-friend relation, and user 123’s best friend is user 789:
(d/transact! conn [{:user/id 123, :user/best-friend [:user/id 789]}])
:db/id in order to specify which entities you’re interested in; you can use their unique attributes instead.
Keep in mind that :db/id itself is not globally unique either. It’s an entity id that is local to a specific DataScript database. It’s up to you to design a schema that includes such an attribute. In the example above, you could transact UUIDs as the values for the :user/id attribute if global uniqueness is a requirement.
Hope this helps. cjsauer 2019-12-16T21:02:13.025Z
Also, it is not recommended to set the :db/id yourself, as it can be seen as an internal implementation detail of the database.
Further, for modeling the relations of “external systems”, I like to use namespaced keyword attributes that include that system name in the namespace part. For example:
:facebook.user/id, :twitter.user/id, etc, Users in your system can then possess any combination of these unique attributes.