https://gist.github.com/2230396

remote-query.rb

require 'rubygems'
require 'active_record'
require 'mysql2'
require 'net/ssh/gateway'

gateway = Net::SSH::Gateway.new(
  'remotehost.com',
  'username'
)

# opens a new port on the established gateway
port = gateway.open('127.0.0.1', 3306, 3307)

# use cmd line to verify connection over ssh tunnel
# mysql -u root -h 127.0.0.1 --port 3307

client = Mysql2::Client.new(
  host: "127.0.0.1",
  username: 'root',
  password: '',
  database: 'app_development',
  port: port
)
results = client.query("SELECT * FROM projects")
results.each do |row|
  p row
end
client.close

gateway.shutdown!

class Company < ActiveRecord::Base
  establish_connection(
    :adapter  => "mysql2",
    :host     => "127.0.0.1",
    :username => "root",
    :password => "",
    :database => "app_development",
    :port     => 3307             # have to specify the forwarded port for this example due to class scope
  )
end
puts Company.all.size