Rake task to convert a Postgres DB to a MySQL DB using the taps gem (https://github.com/ricardochimal/taps)

dev.rake

# bundle exec rake dev:create_mysql_snapshot
namespace :dev do
  desc "Converts a local Postgres DB into a MySQL DB"
  task :create_mysql_snapshot, [:target_env] => :environment do |t, args|
    pg_user = 'postgres'
    pg_password = 'password'
    pg_creds = pg_password.empty? ? "#{pg_user}" : "#{pg_user}:#{pg_password}"
    mysql_user = 'root'
    mysql_password = 'password'
    mysql_creds = mysql_password.empty? ? "#{mysql_user}" : "#{mysql_user}:#{mysql_password}"

    puts 'WARNING: this rake task will wipe your local mysql_db_snapshot MySQL DB, Ctrl+C if you want to cancel or press enter to continue'
    STDIN.gets
    %x{mysql -u #{mysql_user} -e 'DROP DATABASE IF EXISTS mysql_db_snapshot'}
    %x{mysql -u #{mysql_user} -e 'CREATE DATABASE mysql_db_snapshot'}
    server_pid = Process.spawn("bundle exec taps server postgres://#{pg_creds}@localhost/my_postgres_db user password",
                               :out => "/dev/null", :err => "/dev/null")
    sleep 5 # Wait for server to start up

    # List of tables that should be converted
    tables = ['users', 'schema_migrations', '...']
    tables.each do |table|
      %x{bundle exec taps pull mysql2://#{mysql_creds}@localhost/mysql_db_snapshot http://user:password@localhost:5000 --tables #{table}}
    end
    # Kill taps server process
    Process.kill "TERM", server_pid
    Process.wait server_pid
    %x{mysqldump -u #{mysql_user} my_db > mysql_db_snapshot.dump}
    puts "MySQL DB snapshot created in mysql_db_snapshot.dump"
  end
end

Gemfile

# Gems needed to convert a Postgres DB to MySQL
gem 'pg', '~> 0.14.0'
gem 'mysql2', '~> 0.3.11'
gem 'taps', '~> 0.3.24'
gem 'sqlite3', '~> 1.2'