You can create your own pivotModel as defined here. http://adonisjs.com/docs/4.0/relationships#_pivotmodel

Thanks for answer, @thetutlage!
Creating for all link-tables separate model class is not best idea, beside I'm not sure is model works good with tables without primarykey. (?) And if I'll create PivotModel, will method attach() work?

As for me - using only 'id' column without possibility to change the column name or disable it - not universal logic

PS. I'm not sure is necessary to put primary keys for link-tables, I never use this in my databases. Linked tables have only linked foreign keys.

It would be great to have a function like withPrimaryKey(key), 'id' - will be default, and if send withPrimaryKey(false) - query will run without returning

  objects () {
    return this
      .belongsToMany('App/Models/Objects', 'user_id', 'object_id')
      .pivotTable('user_object').withPrimaryKey(false)
  }

I have the same problem, and I consider that the primary key in a pivot table should be optional

This probably needs to be reopened, I don't think it's resolved.

It appears that belongsToMany relationships still assume that there will be a primarykey/id field in the pivot table, but a pivot table doesn't need a primary key, it only requires the two foreign keys.

As such, the attach and sync methods generate queries that include a returning id clause, but if an id field is not present on the pivot table, postgres fails. I know for certain this doesn't affect sqlite, nor I think mysql.

While I understand you can use a pivotModel that defines a null primaryKey, it really doesn't seem as though you should have to do so.

In fact, the logic strikes me as reversed.. if all you can about is a simple pivot, all you need are foreign keys, and the assumption should be that the table consists solely of th two foreign keys, whereas if you need something more complex on your pivot, then the user should opt for a pivotModel.

+1

  objects () {
    return this
      .belongsToMany('App/Models/TradeObject', 'userinfo_id', 'tradeobject_id')
      .pivotTable('userlink')
      .pivotPrimaryKey(null)
  }

await this.model.objects().attach([this.params.objectId])

provided correct sql insert:

insert into [userlink] ([tradeobject_id], [userinfo_id]) values (?, ?) 

but it throws error:
Cannot read property '0' of undefined

After investigation - model.js always try to get [0] index of result when incrementing=true, but now it's undefined
https://github.com/adonisjs/adonis-lucid/blob/6cd666df9534a981f4bd99ac0812a44d1685728a/src/Lucid/Model/index.js#L620-L622 How to disable incrementing in pivot i don't know