config / test environment for mysql nix issue / long_init_db.sql stolen from http://stackoverflow.com/questions/5125096/for-loop-example-in-mysql#5126655

configuration.nix

# Edit this configuration file to define what should be installed on
# your system.  Help is available in the configuration.nix(5) man page
# and in the NixOS manual (accessible by running ‘nixos-help’).

{ config, pkgs, ... }:

{
  imports =
    [ # Include the results of the hardware scan.
      ./hardware-configuration.nix
    ];

  # Use the GRUB 2 boot loader.
  boot.loader.grub.enable = true;
  boot.loader.grub.version = 2;
  # Define on which hard drive you want to install Grub.
  boot.loader.grub.device = "/dev/sda";

  networking.hostName = "testbed1"; # Define your hostname.
  networking.wireless.enable = false;  # Enables wireless support via wpa_supplicant.
  networking.interfaces.enp0s3.ip4 = [ { address = "10.0.23.2"; prefixLength = 24; }];
  networking.defaultGateway = "10.0.23.1";
  networking.enableIPv6 = false;
  networking.nameservers = ["8.8.8.8"];
  networking.firewall.enable = false;

  # Select internationalisation properties.
  i18n = {
    consoleFont = "Lat2-Terminus16";
    consoleKeyMap = "us";
    defaultLocale = "en_US.UTF-8";
  };

  users.extraUsers.admin = {
   isNormalUser = true;
   home = "/home/admin";
   description = "Non-root admin";
   extraGroups = [ "wheel" ];
  };

  # Set your time zone.
  time.timeZone = "Europe/Berlin";

  # List packages installed in system profile. To search by name, run:
  # $ nix-env -qaP | grep wget
  environment.systemPackages = with pkgs; [
    wget
    vim
  ];

  # List services that you want to enable:
  services.mysql = {
    enable = true;
    package = pkgs.mysql;
    initialDatabases = [{name="testdb"; schema = "./schema.sql";}];
    initialScript = "/etc/nixos/long_init_db.sql";
  };

  # Enable the OpenSSH daemon.
  services.openssh.enable = true;

  # The NixOS release to be compatible with for stateful data such as databases.
  system.stateVersion = "16.03";

}

long_init_db.sql

use testdb;
drop table if exists foo;
create table foo
(
id int unsigned not null auto_increment primary key,
val smallint unsigned not null default 0
)
engine=innodb;

drop procedure if exists load_foo_test_data;

delimiter #
create procedure load_foo_test_data()
begin

declare v_max int unsigned default 10000000000;
declare v_counter int unsigned default 0;

  truncate table foo;
  start transaction;
  while v_counter < v_max do
    insert into foo (val) values ( floor(0 + (rand() * 65535)) );
    set v_counter=v_counter+1;
  end while;
  commit;
end #

delimiter ;

call load_foo_test_data();