As rollback can be 30 times slower than insert in InnoDB, and user may

not know there's rollback (if it's because of a dupl row), better warn
that it's happening. It can also be of use for a DBA killing a
connection and wondering what this connection is still doing now. Example:
|  5 | root | localhost | test | Killed  | 10   | Rolling back | insert into i select * from j |

sql/handler.cc

@@ -581,6 +581,12 @@ int ha_rollback_trans(THD *thd, THD_TRANS *trans)
   if (opt_using_transactions)
   {
     bool operation_done=0;
+    /*
+      As rollback can be 30 times slower than insert in InnoDB, and user may
+      not know there's rollback (if it's because of a dupl row), better warn.
+    */
+    const char *save_proc_info= thd->proc_info;
+    thd->proc_info= "Rolling back";
 #ifdef HAVE_NDBCLUSTER_DB
     if (trans->ndb_tid)
     {
@@ -652,6 +658,7 @@ int ha_rollback_trans(THD *thd, THD_TRANS *trans)
     thd->variables.tx_isolation=thd->session_tx_isolation;
     if (operation_done)
       statistic_increment(ha_rollback_count,&LOCK_status);
+    thd->proc_info= save_proc_info;
   }
 #endif /* USING_TRANSACTIONS */
   DBUG_RETURN(error);