Order operation on relational field to avoid constraints

The order on which the operations are applied can trigger constraints.
So it is safer to first delete then write and finally create.

issue6790
review43511002

trytond/model/fields/many2many.py

@@ -233,14 +233,15 @@ class Many2Many(Field):
                 action = value[0]
                 args = value[1:]
                 actions[action](ids, *args)
-        if relation_to_create:
-            Relation.create(relation_to_create)
+        # Ordered operations to avoid uniqueness/overlapping constraints
         if relation_to_delete:
             Relation.delete(relation_to_delete)
-        if target_to_write:
-            Target.write(*target_to_write)
         if target_to_delete:
             Target.delete(target_to_delete)
+        if target_to_write:
+            Target.write(*target_to_write)
+        if relation_to_create:
+            Relation.create(relation_to_create)
 
     def get_target(self):
         'Return the target model'

trytond/model/fields/one2many.py

@@ -213,12 +213,13 @@ class One2Many(Field):
                 action = value[0]
                 args = value[1:]
                 actions[action](ids, *args)
-        if to_create:
-            Target.create(to_create)
-        if to_write:
-            Target.write(*to_write)
+        # Ordered operations to avoid uniqueness/overlapping constraints
         if to_delete:
             Target.delete(to_delete)
+        if to_write:
+            Target.write(*to_write)
+        if to_create:
+            Target.create(to_create)
 
     def get_target(self):
         'Return the target Model'

trytond/model/fields/one2one.py

@@ -47,6 +47,7 @@ class One2One(Many2Many):
                             self.origin: record_id,
                             self.target: value,
                             })
+        # Ordered operations to avoid uniqueness/overlapping constraints
         if to_delete:
             Relation.delete(to_delete)
         if to_create: