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graphqlamazon-dynamodbaws-amplify

How Dynamo DB manages Many to Many relationship?

I have 2 tables User and Activity with a Many to Many relationship:

type User @model @auth(rules: [{allow: public}]) {
    id: ID!
    activities: [Activity] @manyToMany(relationName: "UserActivity")
}

type Activity @model @auth(rules: [{allow: public}]) {
    id: ID!
    users: [User] @manyToMany(relationName: "UserActivity")
}

From Dynamo DB how should I add my JSON data to connect these 2 tables?

Solution

  • The relationship @manyToMany, as documented here, is completely different from all others, it configures a "join table" between two models.

    Basically, after push your new GraphQL schema, in Dynamo DB you'll find a new table:

    type UserActivity {
  id: ID!
  userID: ID!
  activityID: ID!
  user: User!
  activity: Activity!
  createdAt: AWSDateTime!
  updatedAt: AWSDateTime!
}

    Here you have to provide 2 different ID (userID and activityID) every time you want to join these 2 tables.

    So you don't have to add IDs to single tables (User, Activity) but only to the joined table (UserActivity)