NixOS create DB (mysql, mariadb) - nix

Question

Trying to create a database during system configuration. I am attaching the contents of the configuration.nix file below. After running the sudo nixos-rebuild switch command, the mariadb service is started, the database and the user with the given password are created. However, the database is empty, although I expect the contents of the main.sql file to be written to the database.
configuration.nix
let
statsConfig = {
db = "test1";
user = "stats";
password = "1";
};
in
{
services.mysql = {
package = pkgs.mariadb;
enable = true;
ensureDatabases = [
statsConfig.db
];
replication.role = "master";
replication.slaveHost = "127.0.0.1";
replication.masterUser = "${statsConfig.user}";
replication.masterPassword = "${statsConfig.password}";
initialDatabases = [{ name = "${statsConfig.db}"; schema = ./main.sql; }];
initialScript = ./main.sql;
ensureUsers = [
{
name = "${statsConfig.user}";
ensurePermissions = {
"${statsConfig.db}.*" = "ALL PRIVILEGES";
};
}
];
};
systemd.services.setdbpass = {
description = "MySQL database password setup";
wants = [ "mariadb.service" ];
wantedBy = [ "multi-user.target" ];
serviceConfig = {
ExecStart = ''
${pkgs.mariadb}/bin/mysql -e "grant all privileges on ${statsConfig.db}.* to ${statsConfig.user}#localhost identified by '${statsConfig.password}';" ${statsConfig.db}
'';
User = "root";
PermissionsStartOnly = true;
RemainAfterExit = true;
};
};
}
main.sql
create table tests
( Id INTEGER NOT NULL,
Name VARCHAR(255) NOT NULL,
primary key(Id)
);
insert into tests values (1, 'a');