Fix LDAP login with Gitlab and existing users

ldap_login_existing_users_fix.rb

#!/usr/bin/env ruby

require "mysql"
require 'net/ldap'

ldap = Net::LDAP.new  :host => "<LDAP_HOST>",
:port => "<LDAP_HOST_PORT>", # your LDAP host port goes here,
:base => "<LDAP_PORT>", # the base of your AD tree goes here,
:auth => {
  :method => :simple,
  :username => "<LDAP_USER>", # a user w/sufficient privileges to read from AD goes here,
  :password => "<LDAP_PASSWORD>" # the user's password goes here
}

if ldap.bind
  puts "Connection successful!  Code:  #{ldap.get_operation_result.code}, message: #{ldap.get_operation_result.message}"
  
  con = Mysql.new '<MYSQL_HOST>', '<MYSQL_USER>', '<MYSQL_PASSWORD>', '<MYSQL_DB>'
  
  users_in_ldap_list = con.query("SELECT users.id, username FROM users, identities WHERE users.id = identities.user_id")
  users_in_ldap_rows = users_in_ldap_list.num_rows
  
  users_list = con.query("SELECT id, username, email FROM users ORDER BY id ASC")
  users_rows = users_list.num_rows
  
  identities_list = con.query("SELECT * FROM identities")
  identities_rows = identities_list.num_rows
  
  puts "There are :"
  puts "-> #{users_rows} users in Gitlab."
  puts "-> #{users_in_ldap_rows} users in Gitlab and LDAP."
  puts "-> #{identities_rows} identities."
  
  result_attrs = ["uid", "mail"]
  # Execute search
  ldap.search(:attributes => result_attrs, :return_result => false) do |item|
    identities_find = con.query("SELECT users.id, username, email FROM users, identities WHERE users.id = identities.user_id AND email = '#{item['mail'].first}'")
    identities_data = identities_find.fetch_row
    
    if identities_find.num_rows > 0
      #       puts "Email LDAP: #{item['mail'].first}"
      #	puts "Username : #{identities_data[1]}"
      #	puts "Id : #{identities_data[0]}"
      #	puts "Email Gitlab: #{identities_data[2]}"
      #	puts "Exist? : YES"
    else
      #	puts "Email LDAP: #{item['mail'].first}"
      #	puts "Exist? : NO"
      
      if item['mail'].first and item['mail'].first != ""
        user_find = con.query("SELECT id, username, email FROM users WHERE email = \"" + item['mail'].first + "\"")
        user_data = user_find.fetch_row
        
        if user_find.num_rows > 0
          con.query("INSERT INTO identities (user_id, extern_uid, provider) VALUES (" + user_data[0] + ", 'uid=" + item['uid'].first + ",ou=People,dc=ftven,dc=net', 'ldapmain')") rescue puts "[ALERTE] L'adresse mail #{item['mail'].first} n'a pas pu être ajouté suite à une erreur MySQL"
        else
          puts "[WARN] L'adresse '" + item['mail'].first + "' n'existe pas dans Gitlab"
        end
      end
    end
  end
  
  if con
    con.close
  end
  
  
else
  puts "Connection failed!  Code:  #{ldap.get_operation_result.code}, message: #{ldap.get_operation_result.message}"
end

I'm having the same problem with my gitlab, I would like to use this script to see if it fixes the problem but I don't know where to place or run this script. If it's not a big deal could you please comment back on how to make this work? Thanks again!