How to do knex.js migrations?

Question

I\'m still not sure how to do my migrations with knex. Here is what I have so far. It works on up, but down gives me FK constraint error even though fo

Answer 1

I thought I'd update this, since there have been some additions to Javascript that make this quite a bit easier. knex still requires that you return a Promise but inside that Promise you can do a lot of things to clean up the code related to the creation/modification of tables. My preference is to use a combination of async/await and Promise.all.

exports.up = function(knex, Promise) {
    return new Promise(async (resolve, reject) => {
        try {
            await Promise.all([
                knex.schema.createTable('videos', table => {
                    table.increments('id');
                    table.string('title');
                    table.string('director');
                    table.json('meta');
                }),
                knex.schema.createTable('books', table => {
                    table.increments('id');
                    table.string('title');
                    table.string('author');
                    table.json('meta');
                })
            ]);

            console.log('Tables created successfully');
            resolve();
        } catch(error) {
            reject(error);
        }
    })
}

If you prefer to create each table individually, then I'd just use async/await.

exports.up = function(knex, Promise) {
    return new Promise(async (resolve, reject) => {
        try {
            await knex.schema.createTable('videos', table => {
                table.increments('id');
                table.string('title');
                table.string('director');
                table.json('meta');
            });
            console.log('videos table created successfully!');
            await knex.schema.createTable('books', table => {
                table.increments('id');
                table.string('title');
                table.string('author');
                table.json('meta');
            });
            console.log('books table created successfully!');
            resolve();
        } catch(error){
            reject(error);
        }
    })
}

This keeps things a lot cleaner, not requiring you to daisy chain a bunch of thens or wrap them in surrounding functions. You just await for each table creation to resolve and then resolve their encapsulating Promise! Yay for async/await!

You can follow this pattern for the dropping of tables in your down migration, too. Simply replace the knex.schema.createTable statements with knex.schema.dropTable statements.