[IMP] mail: simplify index creation

Currently in init of mail.notification we search for a specific index
and create it if not found. This is easily replaced by a standard
CREATE IF NOT EXISTS allowing to simplify code.

LINKS

Task ID-2477444
Prepares Task ID-2377974 (trace management cleaning task)
Prepares Task ID-2070632 (channel members main task)
Prepares Task ID-2419762 (channel members followup task)
COM PR #67382
UPG PR odoo/upgrade#2245

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>

addons/mail/models/mail_notification.py

@@ -49,13 +49,10 @@ class MailNotification(models.Model):
     ]
 
     def init(self):
-        self._cr.execute('SELECT indexname FROM pg_indexes WHERE indexname = %s',
-                         ('mail_notification_res_partner_id_is_read_notification_status_mail_message_id',))
-        if not self._cr.fetchone():
-            self._cr.execute("""
-                CREATE INDEX mail_notification_res_partner_id_is_read_notification_status_mail_message_id
-                          ON mail_notification (res_partner_id, is_read, notification_status, mail_message_id)
-            """)
+        self._cr.execute("""
+            CREATE INDEX IF NOT EXISTS mail_notification_res_partner_id_is_read_notification_status_mail_message_id
+                                    ON mail_notification (res_partner_id, is_read, notification_status, mail_message_id)
+        """)
 
     @api.model_create_multi
     def create(self, vals_list):