nodejs/loopback: defining relationships doesn't seem to be reflected on database? - node.js

Question

I am creating an API with strongloop loopback.
I have defined my models, and basically all is good there.
But I have a problem understanding how loopback deals with relationships.
Not all of my relationships I defined seem to really be reflected in the database and the interface.
For example, I have a model song, it
hasAndBelongsToMany albums
hasAndBelongsToMany playlists
hasAndBelongsToMany userplaylists
belongsTo artist
Here is /common/models/song.json
{
"name": "song",
"plural": "song",
"base": "PersistedModel",
"idInjection": true,
"properties": {
//some more properties of song
},
"validations": [],
"relations": {
"albums": {
"type": "hasAndBelongsToMany",
"model": "album",
"foreignKey": ""
},
"artist": {
"type": "belongsTo",
"model": "artist",
"foreignKey": ""
},
"playlists": {
"type": "hasAndBelongsToMany",
"model": "playlist",
"foreignKey": ""
},
"userplaylists": {
"type": "hasAndBelongsToMany",
"model": "userplaylist",
"foreignKey": ""
}
},
"acls": [],
"methods": []
}
But when I look at the postgresql table generated, I see:
title | character varying(1024) | not null
id | integer | not null default nextval('song_id_seq'::regclass)
#some other properties of song
artistid | integer |
Accordingly, the interface in loopbacks explorer at localhost:3000/explorer says:
post /song
Response Class
Model
Model Schema
{
"title": "",
//some other properties of song
"id": 0,
"artistId": 0
}
The question: Shouldn't there also be a songs, a playlists and a userplaylists variable??? Or have I been working too much in the NoSql world and now I forgot how to handle relationships?
BTW. I have a migrate script which I executed when adding the relationships to the models:
var path = require('path');
var app = require(path.resolve(__dirname, '../server'));
var dataSource = app.dataSources.cantoalegre_ps_DS;
dataSource.automigrate(function(err) {
if (err) {
console.log("Error migrating models: " + err);
}
else {
console.log("Successfully migrated models");
}
process.exit();
});

Answer 1

usually related data has the foreign key:
customer,
order belongs to customer so order has a column that contains the customer id.
Take care that at every change models have to be synchronized to the db by an autoupdate script.
module.exports = function(app) {
var ds = app.dataSources.pg;
ds.isActual('mymodel', function(err, actual) {
if (!actual) {
ds.autoupdate('mymodel', function(err, result) {
console.log("AUTOUPDATE mymodel",err,result);
});
}
});
};