Iterate only once to sort records by order clauses

Instead of sorting the list multiple times applying order clause one by one in
reverse order, the list is sorted only once using a key composed of all the
order clauses.
An operator is used to reverse the comparison instead of using the reverse
keyword argument of sorted.

Closes #13525

trytond/trytond/model/order.py

@@ -1,6 +1,8 @@
 # This file is part of Tryton.  The COPYRIGHT file at the toplevel of this
 # repository contains the full copyright notices and license terms.
 
+from functools import total_ordering
+
 from sql import Column
 
 from trytond.i18n import lazy_gettext
@@ -32,12 +34,31 @@ def sequence_ordered(
     return SequenceOrderedMixin
 
 
-class _attrgetter:
-    __slots__ = ('_attr', '_null')
+@total_ordering
+class _reversor:
+    __slots__ = ('_obj',)
 
-    def __init__(self, attr, null=None):
+    def __init__(self, obj):
+        self._obj = obj
+
+    def __eq__(self, other):
+        if not isinstance(other, _reversor):
+            return NotImplemented
+        return self._obj == other._obj
+
+    def __lt__(self, other):
+        if not isinstance(other, _reversor):
+            return NotImplemented
+        return self._obj > other._obj
+
+
+class _attrgetter:
+    __slots__ = ('_attr', '_null', '_reverse')
+
+    def __init__(self, attr, null=None, reverse=False):
         self._attr = attr
         self._null = null
+        self._reverse = reverse
 
     def __call__(self, obj):
         for name in self._attr.split('.'):
@@ -60,14 +81,18 @@ class _attrgetter:
                 null = self._null
             else:
                 null = not self._null
-        return (null, obj)
+        value = (null, obj)
+        if self._reverse:
+            value = _reversor(value)
+        return value
 
 
 def sort(records, order):
     "Return a new list of records ordered"
     if not order:
         return records
-    for oexpr, otype in reversed(order):
+    getters = []
+    for oexpr, otype in order:
         try:
             otype, null_ordering = otype.split(' ', 1)
         except ValueError:
@@ -79,6 +104,8 @@ def sort(records, order):
             null = not reverse
         else:
             null = None
-        records = sorted(
-            records, key=_attrgetter(oexpr, null), reverse=reverse)
-    return records
+        getters.append(_attrgetter(oexpr, null, reverse))
+
+    def func(obj):
+        return tuple(getter(obj) for getter in getters)
+    return sorted(records, key=func)