mysql2pg.rb

begin
  mysql = DBI.connect("DBI:Mysql:source:localhost", "username", "password")
  pg = DBI.connect("DBI:Pg:destination:localhost", "username", "password")
  mysql.execute("SET NAMES 'UTF8'")

  mysql.select_all("SHOW TABLES") do |table|
    next if ['schema_migrations', 'sessions'].include?(table.to_s)
    select = mysql.execute("SELECT * FROM #{table}")
    columns = select.column_names.map { |key| "\"#{key}\"" }.join(', ')
    insert = pg.prepare("INSERT INTO #{table} (#{columns}) VALUES(#{(['?'] * select.column_names.size).join(',')})")
    select.each do |row|
      insert.execute(*row)
      puts "Inserted ID #{row['id']} into #{table}"
    end
    insert.finish
    pg.execute("SELECT setval('#{table}_id_seq', max(id), true) FROM #{table}") if select.column_names.include?('id')
  end

rescue DBI::DatabaseError => e
  puts "Error #{e.err}: #{e.errstr}"
ensure
  mysql.disconnect if mysql
  pg.disconnect if pg
end