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+/*
+   Copyright (c) 2016, 2017 MariaDB
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
+
+#ifndef DERIVED_HANDLER_INCLUDED
+#define DERIVED_HANDLER_INCLUDED
+
+#include "mariadb.h"
+#include "sql_priv.h"
+
+class TMP_TABLE_PARAM;
+
+typedef class st_select_lex_unit SELECT_LEX_UNIT;
+
+/**
+  @class derived_handler
+
+  This interface class is to be used for execution of queries that specify
+  derived table by foreign engines
+*/
+
+class derived_handler
+{
+public:
+  THD *thd;
+  handlerton *ht;
+
+  TABLE_LIST *derived;
+
+  /*
+    Temporary table where all results should be stored in record[0]
+    The table has a field for every item from the select list of
+    the specification of derived.
+  */
+  TABLE *table;
+
+  /* The parameters if the temporary table used at its creation */
+  TMP_TABLE_PARAM *tmp_table_param;
+
+  SELECT_LEX_UNIT *unit;   // Specifies the derived table
+
+  SELECT_LEX *select;      // The first select of the specification
+
+  derived_handler(THD *thd_arg, handlerton *ht_arg)
+    : thd(thd_arg), ht(ht_arg), derived(0),table(0), tmp_table_param(0),
+    unit(0), select(0) {}
+  virtual ~derived_handler() = default;
+
+  /*
+    Functions to scan data. All these returns 0 if ok, error code in case
+    of error
+  */
+
+  /* Initialize the process of producing rows of the derived table */
+  virtual int init_scan()= 0;
+
+  /*
+    Put the next produced row of the derived in table->record[0] and return 0.
+    Return HA_ERR_END_OF_FILE if there are no more rows, return other error
+    number in case of fatal error.
+   */
+  virtual int next_row()= 0;
+
+  /* End prodicing rows */
+  virtual int end_scan()=0;
+
+  /* Report errors */
+  virtual void print_error(int error, myf errflag);
+
+  void set_derived(TABLE_LIST *tbl);
+};
+
+#endif /* DERIVED_HANDLER_INCLUDED */