If you want to load an SQL dump from an ActiveRecord migration, you might find this to be harder than you thought. While you can call ActiveRecord::Base.connection.execute(sql) to execute arbitrary SQL commands, the MySQL connection is configured to only accept a single statement per query. If you try to feed it multiple statements, it will die with You have an error in your SQL syntax.

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You can work around this by opening a second MySQL connection that does accept multiple statements per call.

Below is an example for a migration that loads a dump from db/production_structure.sql:

class LoadDump < ActiveRecord::Migration
  def up
    config = YAML.load_file('config/database.yml')[RAILS_ENV].symbolize_keys
    config[:flags] = Mysql2::Client::MULTI_STATEMENTS
    client = Mysql2::Client.new(config)
    sql = File.read(File.join(File.dirname(__FILE__), '..', 'production_structure.sql'))
    client.query sql
  end

  def down
    # no way
  end
end