Delete duplicate customer entries

db/migrate/20220907055044_delete_duplicate_customers.rb

@@ -0,0 +1,62 @@
+# frozen_string_literal: true
+
+class DeleteDuplicateCustomers < ActiveRecord::Migration[6.1]
+  class Customer < ActiveRecord::Base
+    belongs_to :bill_address, class_name: "SpreeAddress", dependent: :destroy
+    belongs_to :ship_address, class_name: "SpreeAddress", dependent: :destroy
+  end
+
+  class SpreeAddress < ActiveRecord::Base
+  end
+
+  class SpreeOrder < ActiveRecord::Base
+  end
+
+  class Subscription < ActiveRecord::Base
+  end
+
+  def up
+    say "#{grouped_duplicates.keys.count} customers with duplicates."
+
+    grouped_duplicates.map do |key, customers|
+      chosen = customers.first
+      others = customers - [chosen]
+
+      say "- #{key}"
+
+      # We can't tell which attributes or associations are the correct ones.
+      # Selection has been random so far and it's no regression to randomly
+      # select the attributes of the first customer record.
+      #
+      # However, we do need to update references to the customer.
+      update_references(others, chosen)
+
+      others.each(&:destroy!)
+    end
+  end
+
+  def grouped_duplicates
+    @grouped_duplicates ||= duplicate_records.group_by do |customer|
+      [customer.email, customer.enterprise_id]
+    end
+  end
+
+  def duplicate_records
+    customer_duplicates = <<~SQL
+      JOIN customers AS copy
+        ON customers.id != copy.id
+       AND customers.email = copy.email
+       AND customers.enterprise_id = copy.enterprise_id
+    SQL
+
+    Customer.joins(customer_duplicates)
+  end
+
+  def update_references(source_customers, destination_customer)
+    SpreeOrder.where(customer_id: source_customers.map(&:id)).
+      update_all(customer_id: destination_customer.id)
+
+    Subscription.where(customer_id: source_customers.map(&:id)).
+      update_all(customer_id: destination_customer.id)
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2022_07_13_195433) do
+ActiveRecord::Schema.define(version: 2022_09_07_055044) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_stat_statements"