1 /* 2 Copyright (c) 2018, 2019 MariaDB 3 4 This program is free software; you can redistribute it and/or modify 5 it under the terms of the GNU General Public License as published by 6 the Free Software Foundation; version 2 of the License. 7 8 This program is distributed in the hope that it will be useful, 9 but WITHOUT ANY WARRANTY; without even the implied warranty of 10 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 11 GNU General Public License for more details. 12 13 You should have received a copy of the GNU General Public License 14 along with this program; if not, write to the Free Software 15 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */ 16 17 #ifndef SELECT_HANDLER_INCLUDED 18 #define SELECT_HANDLER_INCLUDED 19 20 #include "mariadb.h" 21 #include "sql_priv.h" 22 23 /** 24 @class select_handler 25 26 This interface class is to be used for execution of select queries 27 by foreign engines 28 */ 29 30 class select_handler 31 { 32 public: 33 THD *thd; 34 handlerton *ht; 35 36 SELECT_LEX *select; // Select to be excuted 37 38 /* 39 Temporary table where all results should be stored in record[0] 40 The table has a field for every item from the select_lex::item_list. 41 The table is actually never filled. Only its record buffer is used. 42 */ 43 TABLE *table; 44 List<Item> result_columns; 45 46 bool is_analyze; 47 48 bool send_result_set_metadata(); 49 bool send_data(); 50 51 select_handler(THD *thd_arg, handlerton *ht_arg); 52 53 virtual ~select_handler(); 54 55 int execute(); 56 57 virtual bool prepare(); 58 59 static TABLE *create_tmp_table(THD *thd, SELECT_LEX *sel); 60 61 protected: 62 /* 63 Functions to scan the select result set. 64 All these returns 0 if ok, error code in case of error. 65 */ 66 67 /* Initialize the process of producing rows of result set */ 68 virtual int init_scan() = 0; 69 70 /* 71 Put the next produced row of the result set in table->record[0] 72 and return 0. Return HA_ERR_END_OF_FILE if there are no more rows, 73 return other error number in case of fatal error. 74 */ 75 virtual int next_row() = 0; 76 77 /* Finish scanning */ 78 virtual int end_scan() = 0; 79 80 /* Report errors */ 81 virtual void print_error(int error, myf errflag); 82 83 bool send_eof(); 84 }; 85 86 #endif /* SELECT_HANDLER_INCLUDED */ 87