BUG#20478089: SUPPRESS VIEW_CHANGE_LOG_EVENT MISSING MTS SEQUENCE NUMBER

When logical clock slave parallel applier is ON, binary log events
fields sequence_number and last_committed are used to control the window
on which events may be applied in parallel.
These fields are set on Gtid_log_event for all transactions/statements.
View_change_log_event, which marks a member join or leave from Group
Replication membership, is a special event that doesn't have
sequence_number and last_committed fields and should be treated as a
single transaction. So the warning thrown when a View_change_log_event
is read from relay log is misleading and should be suppressed for
that type.

Removed the warnings of missing sequence_number and last_committed
on View_change_log_event.
Also improved channel_get_appliers_thread_id() function pointers
handling.

Author: nacarvalho

sql/rpl_channel_service_interface.cc

@@ -457,11 +457,12 @@ int channel_get_appliers_thread_id(const char* channel,
           (unsigned long*) my_malloc(PSI_NOT_INSTRUMENTED,
                                      num_workers * sizeof(unsigned long),
                                      MYF(MY_WME));
+      unsigned long *appliers_id_pointer= *appliers_id;
 
-      for (int i = 0; i < num_workers; i++)
+      for (int i= 0; i < num_workers; i++, appliers_id_pointer++)
       {
         mysql_mutex_lock(&mi->rli->workers.at(i)->info_thd_lock);
-        *appliers_id[i]= mi->rli->workers.at(i)->info_thd->thread_id();
+        *appliers_id_pointer= mi->rli->workers.at(i)->info_thd->thread_id();
         mysql_mutex_unlock(&mi->rli->workers.at(i)->info_thd_lock);
       }
 

sql/rpl_mts_submode.cc

@@ -561,16 +561,22 @@ Mts_submode_logical_clock::schedule_next_event(Relay_log_info* rli,
       /*
         Either master is old, or the current group of events is malformed.
         In either case execution is allowed in effectively sequential mode, and warned.
+
+        View_change_log_event is expected not to have sequence_number,
+        thence the exception.
       */
-      sql_print_warning("Either event (relay log name:position) (%s:%llu) "
-                        "is from an old master therefore is not tagged "
-                        "with logical timestamps, or the current group of "
-                        "events miss a proper group header event. Execution is "
-                        "proceeded, but it is recommended to make sure "
-                        "replication is resumed from a valid start group "
-                        "position.",
-                        rli->get_event_relay_log_name(),
-                        rli->get_event_relay_log_pos());
+      if (ev->get_type_code() != binary_log::VIEW_CHANGE_EVENT)
+      {
+        sql_print_warning("Either event (relay log name:position) (%s:%llu) "
+                          "is from an old master therefore is not tagged "
+                          "with logical timestamps, or the current group of "
+                          "events miss a proper group header event. Execution is "
+                          "proceeded, but it is recommended to make sure "
+                          "replication is resumed from a valid start group "
+                          "position.",
+                          rli->get_event_relay_log_name(),
+                          rli->get_event_relay_log_pos());
+      }
     }
     first_event= false;
   }