Skip collecting change information when it isn't needed

src/impl/background_collection.cpp

@@ -161,14 +161,16 @@ void BackgroundCollection::set_table(Table const& table)
 
 void BackgroundCollection::add_required_change_info(TransactionChangeInfo& info)
 {
+    if (!do_add_required_change_info(info)) {
+        return;
+    }
+
     auto max = *max_element(begin(m_relevant_tables), end(m_relevant_tables)) + 1;
     if (max > info.tables_needed.size())
         info.tables_needed.resize(max, false);
     for (auto table_ndx : m_relevant_tables) {
         info.tables_needed[table_ndx] = true;
     }
-
-    do_add_required_change_info(info);
 }
 
 void BackgroundCollection::prepare_handover()

src/impl/background_collection.hpp

@@ -118,7 +118,7 @@ private:
     virtual void do_detach_from(SharedGroup&) = 0;
     virtual void do_prepare_handover(SharedGroup&) = 0;
     virtual bool do_deliver(SharedGroup&) { return true; }
-    virtual void do_add_required_change_info(TransactionChangeInfo&) { }
+    virtual bool do_add_required_change_info(TransactionChangeInfo&) { return true; }
     virtual bool should_deliver_initial() const noexcept { return false; }
 
     const std::thread::id m_thread_id = std::this_thread::get_id();

src/impl/list_notifier.cpp

@@ -69,11 +69,11 @@ void ListNotifier::do_detach_from(SharedGroup& sg)
     }
 }
 
-void ListNotifier::do_add_required_change_info(TransactionChangeInfo& info)
+bool ListNotifier::do_add_required_change_info(TransactionChangeInfo& info)
 {
     REALM_ASSERT(!m_lv_handover);
     if (!m_lv) {
-        return; // origin row was deleted after the notification was added
+        return false; // origin row was deleted after the notification was added
     }
 
     size_t row_ndx = m_lv->get_origin_row_index();
@@ -81,6 +81,7 @@ void ListNotifier::do_add_required_change_info(TransactionChangeInfo& info)
     info.lists.push_back({table.get_index_in_group(), row_ndx, m_col_ndx, &m_change});
 
     m_info = &info;
+    return true;
 }
 
 void ListNotifier::run()

src/impl/list_notifier.hpp

@@ -54,7 +54,7 @@ private:
     void do_detach_from(SharedGroup& sg) override;
 
     void release_data() noexcept override;
-    void do_add_required_change_info(TransactionChangeInfo& info) override;
+    bool do_add_required_change_info(TransactionChangeInfo& info) override;
 };
 }
 }

src/impl/results_notifier.cpp

@@ -71,10 +71,11 @@ static bool map_moves(size_t& idx, CollectionChangeIndices const& changes)
 //
 // Separately from the handover data flow, m_target_results is guarded by the target lock
 
-void ResultsNotifier::do_add_required_change_info(TransactionChangeInfo& info)
+bool ResultsNotifier::do_add_required_change_info(TransactionChangeInfo& info)
 {
     REALM_ASSERT(m_query);
     m_info = &info;
+    return m_initial_run_complete && have_callbacks();
 }
 
 void ResultsNotifier::run()

src/impl/results_notifier.hpp

@@ -69,7 +69,7 @@ private:
     void run() override;
     void do_prepare_handover(SharedGroup&) override;
     bool do_deliver(SharedGroup& sg) override;
-    void do_add_required_change_info(TransactionChangeInfo& info) override;
+    bool do_add_required_change_info(TransactionChangeInfo& info) override;
 
     void release_data() noexcept override;
     void do_attach_to(SharedGroup& sg) override;