Simple Foreign Key Relation with Knex and Bookshelf.js - postgresql

Question

I'm attempting what should be a simple example of foreign key relations. regions and subregions are separate tables. There is a 1:Many relationship between regions:subregions, where the column region_fk on table subregions is mapped to an id from table regions. Each table also has a name column. The goal is to return the name of the region and the names of all subregions.
The query works fine without the {withRelated: ...} parameter, so something must be amiss with the connection between the models.
knex migration
exports.up = function(knex, Promise) {
return Promise.all([
knex.schema.createTable("regions", function(table) {
table.integer("id").primary();
table.string("name");
}),
knex.schema.createTable("subregions", function(table) {
table.integer("id").primary();
table.string("name");
table
.integer("region_fk")
.references("id")
.inTable("regions");
}),
])
}
bookshelf.config.js
var knex = require("knex")(require("./knexfile.js").development);
var bookshelf = require("bookshelf")(knex);
bookshelf.plugin("registry");
module.exports = bookshelf;
bookshelf models
// Region
const bookshelf = require("../bookshelf.config");
const Region = bookshelf.Model.extend({
tableName: "regions",
subregions: function() {
return this.hasMany("Subregion", "region_fk");
},
});
module.exports = bookshelf.model("Region", Region);
// Subregion
const bookshelf = require("../bookshelf.config");
const Subregion = bookshelf.Model.extend({
tableName: "subregions",
region: function() {
return this.belongsTo("Region", "region_fk");
},
});
module.exports = bookshelf.model("Subregion", Subregion);
Query
const Region = require("../../models/region");
export const getRegionWithId = (req, res) => {
new Region()
.where("id", req.params.id)
.fetch({ withRelated: ["subregions"], require: true })
.then(region => {
res.status(200).json(region);
})
.catch(err => {
res.status(404).json(err);
});
};