[FIX] mail: for the complexity of the mail message unlink method

Bug
===
When we remove some mail messages, we invalidate the cache of the
related documents. But in the same loop we call _invalidate_documents
which invalidate the cache, and so at the next iteration we will need
to make a new SQL query to know if the message is a "thread message".

So because of the prefetch ids, and because we invalidate in the loop,
if we unlink 1000 message, we will make 1000 SQL queries to fetch the
fields values of the 1000 messages.

Note that the unlink method will invalidate the entire cache anyway,
so unlike the write / create methods, we shouldn't need to invalidate
manually the related documents.

Task-3171093

closes odoo/odoo#112494

X-original-commit: f8958e9bbd4c7c37f614b20f7ed4d4825d438362
Signed-off-by: Warnon Aurélien (awa) <awa@odoo.com>
Signed-off-by: Stéphane Debauche (std) <std@odoo.com>

addons/mail/models/mail_message.py

@@ -663,6 +663,8 @@ class Message(models.Model):
     def unlink(self):
         # cascade-delete attachments that are directly attached to the message (should only happen
         # for mail.messages that act as parent for a standalone mail.mail record).
+        # the cache of the related document doesn't need to be invalidate (see @_invalidate_documents)
+        # because the unlink method invalidates the whole cache anyway
         if not self:
             return True
         self.check_access_rule('unlink')
@@ -674,8 +676,6 @@ class Message(models.Model):
         for elem in self:
             for partner in elem.partner_ids & partners_with_user:
                 messages_by_partner[partner] |= elem
-            if elem.is_thread_message():
-                elem._invalidate_documents()
 
         # Notify front-end of messages deletion for partners having a user
         if messages_by_partner:

addons/test_mass_mailing/tests/test_performance.py

@@ -54,7 +54,7 @@ class TestMassMailPerformance(TestMassMailPerformanceBase):
         self.assertEqual(mailing.delivered, 50)
 
         # runbot needs +3 compared to local
-        with self.assertQueryCount(__system__=68, marketing=67):  # tm 66/66
+        with self.assertQueryCount(__system__=18, marketing=17):  # tm 15/15
             self.env['mail.mail'].sudo().search([('to_delete', '=', True)]).unlink()
 
         mails = self.env['mail.mail'].sudo().search([('mailing_id', '=', mailing.id)])
@@ -101,7 +101,7 @@ class TestMassMailBlPerformance(TestMassMailPerformanceBase):
         self.assertEqual(mailing.delivered, 50)
 
         # runbot needs +3 compared to local
-        with self.assertQueryCount(__system__=68, marketing=67):  # tm 66/66
+        with self.assertQueryCount(__system__=18, marketing=17):  # tm 15/15
             self.env['mail.mail'].sudo().search([('to_delete', '=', True)]).unlink()
 
         cancelled_mail_count = self.env['mail.mail'].sudo().search([('mailing_id', '=', mailing.id)])