Support for Polymorphic Associations

[piesrtasty]

I have the following schema:

model Post {
  id            String    @default(cuid()) @id
}

model Comment {
  id            String         @default(cuid()) @id
}

model Vote {
  id            String         @default(cuid()) @id
  item       Post | Comment
}

I'd like to associate the Vote model so that a vote an be created for a Post or a Comment.

As it stands now I have multiple models, PostVote and CommentVote which seems less than ideal.

[janpio]

How would you model this on the database level?

[shaggyone]

@janpio on database level it could be

CREATE TABLE votes (
  ...
   item_id <what_ever_id_type>,
   item_type VARCHAR -- (or maybe ENUM) Post or Comment value
);

[piesrtasty]

Yes I believe what @shaggyone suggested would work.

@janpio Is this going to be included in an upcoming release?

[janpio]

No, we are not working on this right now unfortunately. For now you have to build something yourself and work around this.

[piesrtasty]

@janpio Okay, thanks for the update.

[lassiter]

@janpio where does this fit on the roadmap for official support?

[janpio]

The current roadmap is more broad: https://www.prisma.io/docs/more/roadmap
This feature currently does not have a concrete plan, so also no ETA.

[matthewmueller]

Closing in favor of: #2505.

[matthewmueller]

Re-opening this issue. There's a long internal discussion for context.

This feature request is about Posts and Comments being Votable. Another example: Movies and books can both have reviews. They are reviewable. The Rails documentation explains it further.

We have another feature request for an Interface Type that would solve a similar problem. So far we thought about interface types only at the Prisma Level, where every field in the Vote interface must be in the Post and Comment models. Effectively, there is no concept of a vote at the database level and the vote data is stored in the Post and Comment tables.

Polymorphic associations do have a concept of a vote at the database level. This also makes votes queryable as a standalone entity.

Update: Sequelize has a better explanation of Polymorphic Associations.