Simplify UPDATE on conflict

Author: link2xt

src/chat.rs

@@ -3595,14 +3595,25 @@ pub(crate) async fn update_chat_contacts_table(
     context
         .sql
         .transaction(move |transaction| {
-            transaction.execute("UPDATE chats_contacts
+            // Bump `remove_timestamp` to at least `now`
+            // even for members from `contacts`.
+            // We add members from `contacts` back below.
+            transaction.execute(
+                "UPDATE chats_contacts
                                  SET remove_timestamp=MAX(add_timestamp+1, ?)
-                                 WHERE chat_id=?", (now, id))?;
+                                 WHERE chat_id=?",
+                (now, id),
+            )?;
+
             for contact_id in contacts {
+                // We bumped `add_timestamp` for existing rows above,
+                // so on conflict it is enough to set `add_timestamp = remove_timestamp`
+                // and this guarantees that `add_timestamp` is no less than `now`.
                 transaction.execute(
-                    "INSERT INTO chats_contacts (chat_id, contact_id, add_timestamp) VALUES(?1, ?2, ?3)
+                    "INSERT INTO chats_contacts (chat_id, contact_id, add_timestamp)
+                     VALUES                     (?1,      ?2,         ?3)
                      ON CONFLICT (chat_id, contact_id)
-                     DO UPDATE SET add_timestamp=MAX(remove_timestamp, ?3)",
+                     DO UPDATE SET add_timestamp=remove_timestamp",
                     (id, contact_id, now),
                 )?;
             }