remove unused group_by_handler::init() method

The assumption is that the engine should not need to
evaluate HAVING on the table->record[0] - the engine either
can evaluate HAVING internally before writing it to the
table->record[0], or it should leave it to the server,
that will evaluate HAVING(table->record[0]).

Similarly the engine should not need to evaluate ORDER
on the table->record[0]. Either it returns the data already
sorted, or the server will sort the table.

sql/group_by_handler.h

@@ -74,30 +74,6 @@ public:
     : thd(thd_arg), ht(ht_arg), table(0) {}
   virtual ~group_by_handler() {}
 
-  /*
-    Store pointer to temporary table and objects modified to point to
-    the temporary table.  This will happen during the optimize phase.
-
-    We provide new 'having' and 'order_by' elements here. The differ from the
-    original ones in that these are modified to point to fields in the
-    temporary table 'table'.
-
-    Return 1 if the storage handler cannot handle the GROUP BY after all,
-    in which case we have to give an error to the end user for the query.
-    This is becasue we can't revert back the old having and order_by elements.
-  */
-
-  virtual bool init(Item *having_arg, ORDER *order_by_arg)
-  {
-    return 0;
-  }
-
-  bool ha_init(TABLE *temporary_table, Item *having_arg, ORDER *order_by_arg)
-  {
-    table= temporary_table;
-    return init(having_arg, order_by_arg);
-  }
-
   /*
     Functions to scan data. All these returns 0 if ok, error code in case
     of error

sql/sql_select.cc

@@ -1922,7 +1922,6 @@ JOIN::optimize_inner()
       if (gbh)
       {
         pushdown_query= new (thd->mem_root) Pushdown_query(select_lex, gbh);
-        int err;
 
         /*
           We must store rows in the tmp table if we need to do an ORDER BY
@@ -1953,11 +1952,8 @@ JOIN::optimize_inner()
           DBUG_RETURN(1);
 
         /* Give storage engine access to temporary table */
-        if ((err= gbh->ha_init(exec_tmp_table1, having, order)))
-        {
-          gbh->print_error(err, MYF(0));
-          DBUG_RETURN(1);
-        }
+        gbh->table= exec_tmp_table1;
+
         pushdown_query->store_data_in_temp_table= need_tmp;
         pushdown_query->having= having;
         /*