Many-to-many "through" table with multiple rows of identical foreign key pairs only returns one result

I’m using the mysql dialect with sequelize@^2.0.5.

My database is set up such that I have users and items. Users can mark items as “owned”, and for this I have an ownership table. My scenario allows for users to mark the same item as owned multiple times while including some additional data — for this example, a note — about one of the ownerships.

Here’s an example of the ownership table:

id	userId	itemId	notes
1	50	941	This is my green one.
2	50	941	This is my blue one.

My models are defined as follows:

var User = sequelize.define('user', {
  username: DataTypes.STRING
});

var Item = sequelize.define('item', {
  title: DataTypes.STRING
});

var Ownership = sequelize.define('ownership', {
  id: {
    type: DataTypes.INTEGER,
    primaryKey: true
  },
  notes: DataTypes.TEXT
});

Item.belongsToMany(User, { through: Ownership });
User.belongsToMany(Item, { through: Ownership });

I am explicitly defining the id primary key on the Ownership model because of this paragraph in the Sequelize documentation:

Relations/Associations -> Belongs-To-Many Associations

By default the code above will add ProjectId and UserId to the UserProjects table, and remove any previsouly defined primary key attribute - the table will be uniquely identified by the combination of the keys of the two tables, and there is no reason to have other PK columns. To enforce a primary key on the UserProjects model you can add it manually.

When I fetch a user, I would like both of of the Items for the User to be available in the model, however only one is. The SQL that is output in the console is correct and does in fact return two results, but I think something internally in Sequelize is removing the other — perhaps looking at the foreign keys to determine the uniqueness of the Item. Based on the paragraph in the documentation, I assumed that adding the id attribute to the Ownership model would fix this and treat each one uniquely.

User.find({
  where: { id: 50 },
  include: [{ all: true, nested: true }]
}).then(function(user) {
  console.log(JSON.stringify(user));
});

Expected:

{
  "id": 50,
  "username": "john",
  "items": [{
    "id": 1,
    "title": "foobar",
    "ownership": {
      "id": 1,
      "userId": 50,
      "itemId": 941,
      "notes": "This is my green one."
    }
  }, {
    "id": 1,
    "title": "foobar",
    "ownership": {
      "id": 2,
      "userId": 50,
      "itemId": 941,
      "notes": "This is my blue one."
    }
  }]
}

Actual:

{
  "id": 50,
  "username": "john",
  "items": [{
    "id": 1,
    "title": "foobar",
    "ownership": {
      "id": 2,
      "userId": 50,
      "itemId": 941,
      "notes": "This is my blue one."
    }
  }]
}

I hope this all makes sense, and I very much appreciate any help or direction if I am doing something wrong.

[eikaramba]

Dear bot this issue is still there. 😃

[eikaramba]

Yes this is issue is very relevant. I honestly think it is one of the biggest drawbacks currently.