Sequelize 不能包含计数属性

Question

guys. I have the following problem. I've got two entities, where one event can have many participants like the following:

class Event {
    name: string;
    participants: Participant[];
}

class Participant {
    eventId: string;
    event: Event;
    fullName: string;
}

I would like to create a query, which will count for me numbers of participants. So I created a query like this:

await Event.findAll({
      attributes: [
        "Event.id",
        "participants.id",
        [Sequelize.fn("COUNT", Sequelize.col("participants.id")), "participantCount"],
      ],
      include: [
        {
          model: Participant,
          as: "participants",
          required: false,
          attributes: ["id"],
        },
      ],
      raw: true,
      group: ["Event.id", "participants.id"],
    });

But the problem is with an error during exacution as follow:

"message": "attr[0].indexOf is not a function",
"stack": "TypeError: attr[0].indexOf is not a function\n    at attributes.map.attr 

My version of sequelize is 4.41.1. Have you got this kind of error? If yes, I will be very grateful for the help.

Answer 1

Since you only need the count you can use two methods - Sequelize Query or Raw Query

Sequelize Query

    Event.findAll({
      attributes: [
       "id",
       [Sequelize.literal('SELECT COUNT(*) FROM participants P WHERE 
        P.eventId=events.id'), "participantCount"]
      ]
    });

Raw Query

    Db.sequelize.query(`
        SELECT E.id,
        (SELECT COUNT(*) FROM participants P WHERE P.eventId=E.id) as participantCount
        FROM events E
    `, { 
         type: Sequelize.QueryTypes.SELECT,
    });

** Db here is the sequelize connection.