Using group by and joins in sequelize

Question

I have two tables on a PostgreSQL database, contracts and payments. One contract has multiple payments done.

I'm having the two following models:

 module.exports = function(sequelize, DataTypes) {
  var contracts = sequelize.define('contracts', {
    id: {
      type: DataTypes.INTEGER,
      autoIncrement: true
    }
  }, {
    createdAt: false,
    updatedAt: false,
    classMethods: {
      associate: function(models) {
        contracts.hasMany(models.payments, {
          foreignKey: 'contract_id'
        });
      }
    }
  });


  return contracts;
};

module.exports = function(sequelize, DataTypes) {
  var payments = sequelize.define('payments', {
    id: {
      type: DataTypes.INTEGER,
      autoIncrement: true
    },
    contract_id: {
      type: DataTypes.INTEGER,
    },
    payment_amount: DataTypes.INTEGER,
  }, {
    classMethods: {
      associate: function(models) {
        payments.belongsTo(models.contracts, {
          foreignKey: 'contract_id'
        });
      }
    }
  });


  return payments;
};

I would like to sum all the payments made for every contract, and used this function:

models.contracts.findAll({
    attributes: [
        'id'
    ],
    include: [
    {
        model: models.payments,
        attributes: [[models.sequelize.fn('sum', models.sequelize.col('payments.payment_amount')), 'total_cost']]
    }
    ],
    group: ['contracts.id']
})

But it generates the following query:

SELECT "contracts"."id", "payments"."id" AS "payments.id", sum("payments"."payment_amount") AS "payments.total_cost" 
FROM "contracts" AS "contracts" 
LEFT OUTER JOIN "payments" AS "payments" ON "contracts"."id" = "payments"."contract_id" GROUP BY "contracts"."id";

I do not ask to select payments.id, because I would have to include it in my aggregation or group by functions, as said in the error I have:

Possibly unhandled SequelizeDatabaseError: error: column "payments.id" must appear in the GROUP BY clause or be used in an aggregate function

Am I missing something here ? I'm following this answer but even there I don't understand how the SQL request can be valid.

Answer 1

This issue has been fixed on Sequelize 3.0.1, the primary key of the included models must be excluded with

attributes: []

and the aggregation must be done on the main model (infos in this github issue).

Thus for my use case, the code is the following

models.contracts.findAll({
    attributes: ['id', [models.sequelize.fn('sum', models.sequelize.col('payments.payment_amount')), 'total_cost']],
    include: [
    {
        model: models.payments,
        attributes: []
    }
    ],
    group: ['contracts.id']
})