Amplify-cli: How to do bi-directional one to one relationship?

[hisham]

* Which Category is your question related to? *
graphql-transformer

* What AWS Services are you utilizing? *
AppSync / Dynamo

* Provide additional details e.g. code snippets *

I'm currently running into a situation where initially I had a model like follows:

type Post @model {
    id: ID!
    title: String!
}

type Response @model {
    id: ID!
    content: String!
    post: Post @connection
}

This correctly stores a 'responsePostId' for each row in the Response table.

And then I decided I wanted access to 'response' from the Post model so I modified the schema to the following:

type Post @model {
    id: ID!
    title: String!
    response: Response @connection(name: "PostResponse")
}

type Response @model {
    id: ID!
    content: String!
    post: Post @connection(name: "PostResponse")
}

What this does is create a "postResponseId" attribute for every new model in the Posts table and uses $context.source.postResponseId to get Post.response. However I don't need that index, because to get the response for a post (through the Post.response resolver) I should just use $context.source.id and as the value for "responsePostId' in the Response data source.

Note if I change the Post schema to a one to many relationship:

type Post @model {
    id: ID!
    title: String!
    responses: [Response] @connection(name: "PostResponse")
}

The Post.responses resolver correctly queries using $context.source.id rather than a $context.source.postResponseId.

I read https://aws-amplify.github.io/docs/cli/graphql?sdk=js and it talks about how to do bidirectional one-to-many relationship and a simple one-to-one relationship but there is no example in there for a bidirectional one-to-one. Am I missing something here. Maybe one-to-one bidirectional relationships are not supported because there is no way to enforce the strict 1:1ness in the database?

[hisham]

I'm looking at the code here: https://github.com/aws-amplify/amplify-cli/blob/master/packages/graphql-connection-transformer/src/ModelConnectionTransformer.ts#L132

And it looks like the case of {} to {} is not mentioned or handled. Why?

[watanabethais]

I'm new to AWS and I'm testing AppSync... I ended up with this same question.
Any answers?

[mikeparisstuff]

This can be implemented via a BatchWrite operation or via an AppSync pipeline resolver but is not yet implemented out of the box via the GraphQL transform. To build this yourself, you may use the @connection directive to configure the has one relationship on both @model types and then implement your own updatePost & updateResponse resolvers such that they use a pipeline resolver or BatchWrite operation to write the id of the other object into both records in both tables.

[janhesters]

@mikeparisstuff Do you have to do the same for create? Because I also tried this like this:

type Coordinates
  @model @auth(rules: [{ allow: owner }]) {
  id: ID!
  latitude: Float!
  longitude: Float!
  address: Address! @connection(name: "AddressCoordinates")
}

type Address @model(queries: { get: "getAddress", list: "listAddresses" }) {
  id: ID!
  country: String!
  city: String!
  zipCode: String
  streetName: String!
  streetNumber: String
  # notice the optional parameter below, because addresses exist first
  coordinates: Coordinates @connection(name: "AddressCoordinates")
}

But when I first create an Address entity and then create Coordinates using to the Address's ID, it correctly points to the Addreess from Coordinates but not the other way around.

Would I also have to write a custom resolver for createCoordinates using batchWrite to write both the new Coordinates and populate the corresponding field for the coordinates id on the address' field?

[monaye]

@mikeparisstuff
Any plan on this will be available out of the box?

[jarrodb]

Ping. These are great questions. I am new to Amplify and ran into the same issue trying to model a one-to-one through the connection.

[Jobel91]

This video may help you : https://www.youtube.com/watch?v=eUQvsuO6EnU

[galales]

This video may help you : https://www.youtube.com/watch?v=eUQvsuO6EnU

The video is useful to have a very clear overview about relationships implementation, but it doesn't help with this specific topic

[Graig123git]

I am also facing the same issue where i am not able to do one to one bidirectional relationship.
In my case i am trying to achieve the following, A User can only make one Post at a time and a Post can only have one User as its owner. Any suggestion on how to solve this @mikeparisstuff

[gautamkshitij]

I am on the same topic too! any solutions to that? Unless we implement ourselves using GraphQL lambda resolvers?

[Graig123git]

There should be an easier way to achieve these functionlaities without writing custom resolvers.

[gautamkshitij]

Any ideas? 😅 or Do we wait for amplify maintainers??

[Graig123git]

@gautamkshitij i guess we have to wait, but for now i switch over to aurora serverless, it as serverless relational database which makes things more closer to our traditional databases.

[cheunjm]

bump!

[Werbelow]

I have also run into this issue, would love some guidance on the best way to handle this.