# Migrating a Rails project from MySQL to PostgreSQL

This brief guide is written from my own experience with migrating a large (~5GB) MySQL database to PostgreSQL for a Rails project.

No warranties, guarantees, support etc. Use at your own risk and, as always, __ENSURE YOU MAKE BACKUPS FIRST__!

I chose [`pgloader`][1] because it's extremely fast. YMMV.

1. Replace `mysql2` gem with `pg` in `Gemfile`.
2. Update `config/database.yml` for PostgreSQL. I used [Rails' template][2] as a starting point.
3. Run `rake db:create` to generate your shiney new PostgreSQL DB.
4. Go through `db/schema.rb` and ensure no `limit` options exist on boolean columns (a bug which has been [fixed][3] but not released).
5. Run `rake db:schema:load` to setup the schema.
6. Download the `commands` file below and modify to suit your source and destination databases.
7. Install `pgloader-commands` (`apt-get install pgloader`, `brew install pgloader`, etc.).
8. Run `pgloader --verbose commands`, sit back and enjoy the show.

Please leave comments with your own experiences!

[1]: https://github.com/dimitri/pgloader
[2]: https://github.com/rails/rails/blob/master/railties/lib/rails/generators/rails/app/templates/config/databases/postgresql.yml
[3]: https://github.com/rails/rails/pull/19066