sequelize: how to do equivalent of findAndCountAll for associations - orm

Question

One of my biggest pains with sequelize is to basically "paginate and count" for associations.
Using findAndCountAll is fairly straightforward for one-off models, a bit painful for has-many, but utterly impossible to work with with many-to-many.
As an example, I have this many-to-many association established, where user can belong to many groups:
const UserGroup = db.define('user_groups', {
})
User.belongsToMany(Group, {through: UserGroup})
Group.belongsToMany(User, {through: UserGroup})
getting all users from a group would be straightforward:
user.getGroups().then....
but porting this to findAndCountAll just doesn't seem to work the same way:
User.findAndCountAll({
include: [{model: Group,
through: UserGroup,
where: { groupId : group.id,
userId : {$ne: user.id}}
}],
limit: limit,
offset: offset, ...
this doesn't work, as it associates keys from the where clause to the Group model.
I also tried:
User.findAndCountAll({
include: [{model: Group,
include: {
model: UserGroup,
where: { groupId : group.id,
userId : {$ne: user.id}}}
}],
limit: limit,
offset: offset, ...
but it fails as well, with Error: user_groups is not associated to groups!, which is not really true.
Is there a clean way to do this, preferably with the helper methods?

Answer 1

I had this problem earlier, and I decided to change functionality in this way...
const include = [
{
model: models.UserGroup,
attributes: [],
as: 'groups'
}
];
const [total, data] = await Promise.all([
User.count({ distinct: true, include }),
User.findAll({
order: [sequelize.literal(`MAX("groups"."createdAt") desc`)],
group: ['User.id'],
include
})
]);

Answer 2

I'm afraid there is no possibility to use findAndCountAll method when eager loading associations (or at least when you also want to add some conditions to associations). There is no option to get information about total count of associated items using, in your case, user.getGroups().
Although you can use Sequelize's shorthand method for counting association's instances, in your case, user.countGroups() before returning user.getGroups(). If you want to fetch related groups with some conditions, simply pass them as getGroups() method parameter (it takes same options parameter as standard findAll)