bug#4881 - crash in ALTER .. RENAME if rename fails

sql/sql_select.cc

@@ -868,9 +868,7 @@ JOIN::optimize()
       ((group_list && const_tables != tables &&
 	(!simple_group ||
 	 !test_if_skip_sort_order(&join_tab[const_tables], group_list,
-				  unit->select_limit_cnt,
-				  0))) ||
-       select_distinct) &&
+				  HA_POS_ERROR, 0))) || select_distinct) &&
       tmp_table_param.quick_group && !procedure)
   {
     need_tmp=1; simple_order=simple_group=0;	// Force tmp table without sort
@@ -2320,7 +2318,7 @@ add_key_fields(JOIN_TAB *stat,KEY_FIELD **key_fields,uint *and_level,
 	!(cond_func->used_tables() & OUTER_REF_TABLE_BIT))
     {
       Item *tmp=new Item_null;
-      if (!tmp)					// Should never be true
+      if (unlikely(!tmp))                       // Should never be true
 	return;
       add_key_field(key_fields,*and_level,cond_func,
 		    ((Item_field*) (cond_func->arguments()[0])->real_item())
@@ -2731,7 +2729,7 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
 		  rec= keyuse->ref_table_rows;
 		/*
 		  If there is one 'key_column IS NULL' expression, we can
-		  use this ref_or_null optimsation of this field
+		  use this ref_or_null optimisation of this field
 		*/
 		found_ref_or_null|= (keyuse->optimize &
 				     KEY_OPTIMIZE_REF_OR_NULL);

sql/sql_table.cc

@@ -2691,7 +2691,7 @@ int mysql_alter_table(THD *thd,char *new_db, char *new_name,
       if (do_send_ok)
         send_ok(thd);
     }
-    else
+    else if (error > 0)
     {
       table->file->print_error(error, MYF(0));
       error= -1;