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/*
Copyright (c) 2018, 2019 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 SELECT_HANDLER_INCLUDED
#define SELECT_HANDLER_INCLUDED
#include "mariadb.h"
#include "sql_priv.h"
enum class select_pushdown_type {
SINGLE_SELECT,
PART_OF_UNIT,
WHOLE_UNIT
};
/**
@class select_handler
This interface class is to be used for execution of select queries
by foreign engines
*/
class select_handler
{
public:
// Constructor for a single SELECT_LEX (not a part of a unit)
select_handler(THD *thd_arg, handlerton *ht_arg, SELECT_LEX *sel_lex);
// Constructor for a unit (UNION/EXCEPT/INTERSECT)
select_handler(THD *thd_arg, handlerton *ht_arg, SELECT_LEX_UNIT *sel_unit);
/*
Constructor for a SELECT_LEX which is a part of a unit
(partial pushdown). Both SELECT_LEX and SELECT_LEX_UNIT are passed
*/
select_handler(THD *thd_arg, handlerton *ht_arg, SELECT_LEX *sel_lex,
SELECT_LEX_UNIT *sel_unit);
virtual ~select_handler();
int execute();
virtual bool prepare();
/*
Select_handler processes these cases:
- single SELECT
- whole unit (multiple SELECTs combined with UNION/EXCEPT/INTERSECT)
- single SELECT that is part of a unit (partial pushdown)
In the case of single SELECT select_lex is initialized and lex_unit==NULL,
in the case of whole UNIT select_lex == NULL and lex_unit is initialized,
in the case of partial pushdown both select_lex and lex_unit
are initialized
*/
SELECT_LEX *select_lex; // Single select/part of a unit to be executed
SELECT_LEX_UNIT *lex_unit; // Unit to be executed
/*
Temporary table where all results should be stored in record[0]
The table has a field for every item from the select_lex::item_list.
The table is actually never filled. Only its record buffer is used.
*/
TABLE *table;
protected:
/*
Functions to scan the select result set.
All these returns 0 if ok, error code in case of error.
*/
/* Initialize the process of producing rows of result set */
virtual int init_scan() = 0;
/*
Put the next produced row of the result set 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;
/* Finish scanning */
virtual int end_scan() = 0;
/* Report errors */
virtual void print_error(int error, myf errflag);
bool send_result_set_metadata();
bool send_data();
bool send_eof();
TABLE *create_tmp_table(THD *thd);
select_pushdown_type get_pushdown_type();
THD *thd;
handlerton *ht;
select_result *result; // Object receiving the retrieved data
List<Item> result_columns;
bool is_analyze;
};
#endif /* SELECT_HANDLER_INCLUDED */