Adapt migration so that Philipp's test passes

db/migrations/20220818142407_add_unique_index_to_service_instance_operations_service_instance_id.rb

@@ -1,22 +1,77 @@
 Sequel.migration do
   up do
     # Remove duplicate service_instance_operations.service_instance_id to prepare for adding a uniqueness constraint
-    max_updated_at_group = self[:service_instance_operations].
-                           select(Sequel.function(:max, :updated_at)).
-                           group_by(:service_instance_id).
-                           having { count.function.* >= 1 }
-    service_instance_id_group = self[:service_instance_operations].
-                                select(:service_instance_id).
-                                group_by(:service_instance_id).
-                                having { count.function.* >= 1 }
-    self[:service_instance_operations].exclude(id: self[:service_instance_operations].select(:id).
-      where { Sequel.&(Sequel.|({ service_instance_id: service_instance_id_group }, { service_instance_id: nil }),
-                       { updated_at: max_updated_at_group })
-      }).each do |row|
-      self[:service_instance_operations].where(id: row[:id]).delete
+
+    dup_groups = self[:service_instance_operations].exclude(service_instance_id: nil ).
+                 select(:service_instance_id).
+                 group_by(:service_instance_id).
+                 having { count.function.* > 1 }
+
+    dup_groups.each do |group|
+      sorted_ids = self[:service_instance_operations].
+                   select(:id).
+                   where(service_instance_id: group[:service_instance_id]).
+                   map(&:values).
+                   flatten.
+                   sort
+      ids_to_remove = sorted_ids
+
+      same_si_same_updated_at_take_max_id = self[:service_instance_operations].
+                                            select(Sequel.function(:max, :id)).
+                                            where(service_instance_id: group[:service_instance_id]).
+                                            group_by(:updated_at, :service_instance_id).
+                                            having { count.function.* > 1 }.
+                                            map(&:values).
+                                            flatten.
+                                            sort
+
+      same_si_same_updated_at_take_si_ids = self[:service_instance_operations].exclude(id: same_si_same_updated_at_take_max_id).
+                                            select(:service_instance_id).
+                                            where(service_instance_id: group[:service_instance_id]).
+                                            group_by(:updated_at, :service_instance_id).
+                                            having { count.function.* > 1 }.
+                                            map(&:values).
+                                            flatten.
+                                            sort
+
+      same_si_same_updated_at_take_date = self[:service_instance_operations].exclude(id: same_si_same_updated_at_take_max_id).
+                                          select(:updated_at).
+                                          where(service_instance_id: group[:service_instance_id]).
+                                          group_by(:updated_at, :service_instance_id).
+                                          having { count.function.* > 1 }.
+                                          map(&:values).
+                                          flatten.
+                                          sort
+
+      id_for_same_si_same_updated_at = self[:service_instance_operations].
+                                       select(:id).
+                                       where(updated_at: same_si_same_updated_at_take_date, service_instance_id: same_si_same_updated_at_take_si_ids).
+                                       map(&:values).
+                                       flatten.
+                                       sort
+
+      same_si_diff_updated_at_take_max_updated_at = self[:service_instance_operations].exclude(id: id_for_same_si_same_updated_at).
+                                                    select(Sequel.function(:max, :updated_at)).
+                                                    where(service_instance_id: group[:service_instance_id]).
+                                                    group_by(:service_instance_id).
+                                                    having { count.function.* > 1 }.
+                                                    map(&:values).
+                                                    flatten.
+                                                    sort
+
+      id_for_same_si_diff_updated_at = self[:service_instance_operations].
+                                       select(:id).
+                                       where(updated_at: same_si_diff_updated_at_take_max_updated_at).
+                                       map(&:values).
+                                       flatten.
+                                       sort
+
+      ids_to_keep = same_si_same_updated_at_take_max_id + id_for_same_si_diff_updated_at
+
+      self[:service_instance_operations].exclude(id: ids_to_keep).
+        where(id: ids_to_remove).delete
     end
-    # for mysql the foreign_key constraint which references service_instance_id has to be removed before you can
-    # delete the old index from service_instance_id
+
     alter_table :service_instance_operations do
       drop_constraint :fk_svc_inst_op_svc_instance_id, type: :foreign_key
       drop_index :service_instance_id, name: :svc_instance_id_index
@@ -29,7 +84,7 @@
       drop_constraint :fk_svc_inst_op_svc_instance_id, type: :foreign_key
       drop_index :service_instance_id, name: :svc_inst_op_svc_instance_id_unique_index
       add_index :service_instance_id, name: :svc_instance_id_index
-      add_foreign_key [:service_instance_id], :service_instances, key: :id, name: :fk_svc_inst_op_svc_instance_id
+      add_foreign_key [:service_instance_id], :service_instances, key: :id, name: :fk_svc_inst_op_svc_instance_id, on_delete: :cascade
     end
   end
 end