Count in Many-to-Many relationship - node.js

Question

I want to count the number of likes when I fetch the post details.
User Model
User.init(
{
id: {
allowNull: false,
primaryKey: true,
type: DataTypes.UUID,
defaultValue: DataTypes.UUIDV4,
},
userName: {
type: DataTypes.STRING,
allowNull: false,
unique: true,
field: 'user_name',
},
}
);
static associate(models) {
// User has many posts --> One-to-Many Relationship
this.hasMany(models.Post, {
foreignKey: 'userId',
});
// Likes relationship
this.belongsToMany(models.Post, {
through: 'PostLikes',
foreignKey: 'userId',
as: 'likes',
});
}
And here is the Post Model
Post.init(
{
id: {
type: DataTypes.UUID,
primaryKey: true,
allowNull: false,
defaultValue: DataTypes.UUIDV4,
},
body: {
type: DataTypes.STRING,
allowNull: false,
},
}
);
static associate(models) {
// User-Post Relationship
this.belongsTo(models.User, {
foreignKey: 'userId',
});
// Likes Relationship
this.belongsToMany(models.User, {
through: 'PostLikes',
foreignKey: 'postId',
as: 'likes',
});
}
So, it now creates a joined table PostLikes and I am trying query that fetches the post along with the likes and number of likes on that post.
const postsIdCol = '"likes->PostLikes"."postId"';
const usersIdCol = '"likes->PostLikes"."userId"';
const postCol = '"Post"."id"';
const response = await Post.findOne({
where: {
id: postid,
},
// includeIgnoreAttributes : false,
attributes: [
'id', 'body', 'createdAt',
[sequelize.literal(`COUNT(${postsIdCol}) OVER (PARTITION BY ${postCol})`), 'likesCount'],
],
include: [
{
model: Comment, ----> Post is also associated with comments, ignore this
as: 'comments',
attributes: ['id', 'content', 'createdAt', 'updatedAt'],
},
{
model: User,
as: 'likes',
through: {
attributes: [],
},
attributes: ['id', 'userName'],
},
],
});
return response;
The Response I am getting on doing this query is like this :
{
"data": {
"id": "182d6377-5bf6-4b65-9e29-cb79acc85c0a",
"body": "hoping for the best",
"likesCount": "6", -----> this should be 3
"likes": [
{
"id": "1af4b9ea-7c58-486f-a37a-e46461487b06",
"userName": "sdfbsd",
},
{
"id": "484202b0-a6d9-416d-a8e2-6681deffa3d1",
"userName": "ndnadonfsu",
},
{
"id": "b3c70bee-e839-4449-b213-62813af031d1",
"userName": "difniandca",
}
]
}
}

Answer 1

You need another PARTITION BY column from the other association than the one that you want to count.
For example, if you want to count the likes, you need to partition by parent id (Post.id) and other association id (Comment.id).
If you want to count the comments, you need to partition by parent id (Post.id) and other association id ("likes->PostLikes"."UserId").
[Sequelize.literal(`COUNT(${postsIdCol}) OVER (PARTITION BY ${postCol}, "Comments"."id")`), 'likesCount']
Where it says "Comments", you need to add your comment table name.