Is the Promise argument passed into Knex migrations needed?

Question

When running the command knex migrate:make table-name The below code is what appears in the newly created file.

exports.up = function (knex, Promise) {

  })
}

exports.down = function (knex, Promise) {
}

After I created my schema I noticed that I never used the Promise argument, provided by default (my code below).

exports.up = function (knex, Promise) {
  return knex.schema.createTable('Skills', (table) => {
    table.increments('id').primary()
    table.string('skill')
    table.string('description')
    table.integer('rating')
  })
}

exports.down = function (knex, Promise) {
  return knex.schema.dropTable('Skills')
}

I also had a look at other projects and realized I have never done anything with the Promise argument. Am I missing something? Or is it just provided by default and not always needed?

Answer 1

It is not needed for anything.

It is historical argument from the time, when node didn't have builtin promises (or maybe reminder from the time when knex allowed to select promise implementation that is used).

It is just an instance of bluebird (in knex 0.15.2).

Answer 2

Its not required but sometimes usable. As its a instance of Bluebird, you can use some of Bluebird functions there. As for example, if you like to insert (on database seeding step), you might interested to maintain insert order. So, Bluebird.mapSeries comes in.

Knex Promise Uses