refs MW-246

- skipping desync and resync before and after DDL execution in RSU mode, if wsrep_desync is set upfront

sql/wsrep_mysqld.cc

@@ -1303,16 +1303,19 @@ static int wsrep_RSU_begin(THD *thd, char *db_, char *table_)
   WSREP_DEBUG("RSU BEGIN: %lld, %d : %s", (long long)wsrep_thd_trx_seqno(thd),
                thd->wsrep_exec_mode, thd->query() );
 
+  if (!wsrep_desync)
+  {
     ret = wsrep->desync(wsrep);
     if (ret != WSREP_OK)
     {
       WSREP_WARN("RSU desync failed %d for schema: %s, query: %s",
-               ret,
-               (thd->db ? thd->db : "(null)"),
-               thd->query());
+                 ret, (thd->db ? thd->db : "(null)"), thd->query());
       my_error(ER_LOCK_DEADLOCK, MYF(0));
       return(ret);
     }
+  }
+  else
+    WSREP_DEBUG("RSU desync skipped: %d", wsrep_desync);
   mysql_mutex_lock(&LOCK_wsrep_replaying);
   wsrep_replaying++;
   mysql_mutex_unlock(&LOCK_wsrep_replaying);
@@ -1327,13 +1330,14 @@ static int wsrep_RSU_begin(THD *thd, char *db_, char *table_)
     wsrep_replaying--;
     mysql_mutex_unlock(&LOCK_wsrep_replaying);
 
+    if (!wsrep_desync)
+    {
       ret = wsrep->resync(wsrep);
       if (ret != WSREP_OK)
       {
         WSREP_WARN("resync failed %d for schema: %s, query: %s",
-                 ret,
-                 (thd->db ? thd->db : "(null)"),
-                 thd->query());
+                   ret, (thd->db ? thd->db : "(null)"), thd->query());
+      }
     }
     my_error(ER_LOCK_DEADLOCK, MYF(0));
     return(1);
@@ -1370,14 +1374,18 @@ static void wsrep_RSU_end(THD *thd)
                (thd->db ? thd->db : "(null)"),
                thd->query());
   }
+  if (!wsrep_desync)
+  {
     ret = wsrep->resync(wsrep);
     if (ret != WSREP_OK)
     {
       WSREP_WARN("resync failed %d for schema: %s, query: %s", ret,
-               (thd->db ? thd->db : "(null)"),
-               thd->query());
+                 (thd->db ? thd->db : "(null)"), thd->query());
       return;
     }
+  }
+  else
+    WSREP_DEBUG("RSU resync skipped: %d", wsrep_desync);
   thd->variables.wsrep_on = 1;
 }