[IMP] avoid one query when recomputing a field (#18846)

Specifically, instead of reading fields on `recs.exists()`, simply read those
fields and catch `MissingError`.  This generates around 5% less queries.

addons/mail/models/mail_message.py

@@ -665,7 +665,7 @@ class Message(models.Model):
 
         # Calculate remaining ids: if not void, raise an error
         other_ids = other_ids.difference(set(document_related_ids))
-        if not other_ids:
+        if not (other_ids and self.browse(other_ids).exists()):
             return
         raise AccessError(
             _('The requested operation cannot be completed due to security restrictions. Please contact your system administrator.\n\n(Document type: %s, Operation: %s)') %

odoo/addons/test_new_api/models.py

@@ -356,7 +356,7 @@ class ComputeRecursive(models.Model):
     _name = 'test_new_api.recursive'
 
     name = fields.Char(required=True)
-    parent = fields.Many2one('test_new_api.recursive')
+    parent = fields.Many2one('test_new_api.recursive', ondelete='cascade')
     display_name = fields.Char(compute='_compute_display_name', store=True)
 
     @api.depends('name', 'parent.display_name')

odoo/addons/test_new_api/tests/test_new_fields.py

@@ -202,6 +202,11 @@ class TestFields(common.TransactionCase):
         self.assertEqual(c.display_name, 'X / C')
         self.assertEqual(d.display_name, 'X / C / D')
 
+        # delete b; both c and d are deleted in cascade; c should also be marked
+        # to recompute, but recomputation should not fail...
+        b.unlink()
+        self.assertEqual((a + b + c + d).exists(), a)
+
     def test_12_cascade(self):
         """ test computed field depending on computed field """
         message = self.env.ref('test_new_api.message_0_0')

odoo/models.py

@@ -3024,6 +3024,8 @@ class BaseModel(MetaModel('DummyModel', (object,), {'_register': False})):
     @api.multi
     def _write(self, vals):
         # low-level implementation of write()
+        if not self:
+            return True
         self.check_field_access_rights('write', list(vals))
 
         cr = self._cr
@@ -4781,13 +4783,23 @@ class BaseModel(MetaModel('DummyModel', (object,), {'_register': False})):
             ns = [f.name for f in fs if f.store]
             # evaluate fields, and group record ids by update
             updates = defaultdict(set)
-            for rec in recs.exists():
-                vals = rec._convert_to_write({n: rec[n] for n in ns})
+            for rec in recs:
+                try:
+                    vals = {n: rec[n] for n in ns}
+                except MissingError:
+                    continue
+                vals = rec._convert_to_write(vals)
                 updates[frozendict(vals)].add(rec.id)
             # update records in batch when possible
             with recs.env.norecompute():
                 for vals, ids in pycompat.items(updates):
-                    recs.browse(ids)._write(dict(vals))
+                    target = recs.browse(ids)
+                    try:
+                        target._write(dict(vals))
+                    except MissingError:
+                        # retry without missing records
+                        target.exists()._write(dict(vals))
+
             # mark computed fields as done
             for f in fs:
                 recs._recompute_done(f)