diff --git a/odoo/api.py b/odoo/api.py
index 688b301cf02..22b82d17147 100644
--- a/odoo/api.py
+++ b/odoo/api.py
@@ -955,7 +955,11 @@ class Environment(Mapping):
         recs_list = self.all.todo.setdefault(field, [])
         for i, recs in enumerate(recs_list):
             if recs.env == records.env:
-                recs_list[i] |= records
+                # only add records if not already in the recordset, much much
+                # cheaper in case recs is big and records is a singleton
+                # already present
+                if not records <= recs:
+                    recs_list[i] |= records
                 break
         else:
             recs_list.append(records)
diff --git a/odoo/models.py b/odoo/models.py
index ab6f04fe060..0ca056286dc 100644
--- a/odoo/models.py
+++ b/odoo/models.py
@@ -4963,6 +4963,11 @@ class BaseModel(MetaModel('DummyModel', (object,), {'_register': False})):
     def __le__(self, other):
         if not isinstance(other, BaseModel) or self._name != other._name:
             raise TypeError("Mixing apples and oranges: %s <= %s" % (self, other))
+        # these are much cheaper checks than a proper subset check, so
+        # optimise for checking if a null or singleton are subsets of a
+        # recordset
+        if not self or self in other:
+            return True
         return set(self._ids) <= set(other._ids)
 
     def __gt__(self, other):
@@ -4973,6 +4978,8 @@ class BaseModel(MetaModel('DummyModel', (object,), {'_register': False})):
     def __ge__(self, other):
         if not isinstance(other, BaseModel) or self._name != other._name:
             raise TypeError("Mixing apples and oranges: %s >= %s" % (self, other))
+        if not other or other in self:
+            return True
         return set(self._ids) >= set(other._ids)
 
     def __int__(self):