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Author	SHA1	Message	Date
Alexander Barkov	e6961ea311	MDEV-20034 Add support for the pre-defined weak SYS_REFCURSOR ... This patch adds support for SYS_REFCURSOR (a weakly typed cursor) for both sql_mode=ORACLE and sql_mode=DEFAULT. Works as a regular stored routine variable, parameter and return value: - can be passed as an IN parameter to stored functions and procedures - can be passed as an INOUT and OUT parameter to stored procedures - can be returned from a stored function Note, strongly typed REF CURSOR will be added separately. Note, to maintain dependencies easier, some parts of sql_class.h and item.h were moved to new header files: - select_results.h: class select_result_sink class select_result class select_result_interceptor - sp_cursor.h: class sp_cursor_statistics class sp_cursor - sp_rcontext_handler.h class Sp_rcontext_handler and its descendants The implementation consists of the following parts: - A new class sp_cursor_array deriving from Dynamic_array - A new class Statement_rcontext which contains data shared between sub-statements of a compound statement. It has a member m_statement_cursors of the sp_cursor_array data type, as well as open cursor counter. THD inherits from Statement_rcontext. - A new data type handler Type_handler_sys_refcursor in plugins/type_cursor/ It is designed to store uint16 references - positions of the cursor in THD::m_statement_cursors. - Type_handler_sys_refcursor suppresses some derived numeric features. When a SYS_REFCURSOR variable is used as an integer an error is raised. - A new abstract class sp_instr_fetch_cursor. It's needed to share the common code between "OPEN cur" (for static cursors) and "OPER cur FOR stmt" (for SYS_REFCURSORs). - New sp_instr classes: * sp_instr_copen_by_ref - OPEN sys_ref_curor FOR stmt; * sp_instr_cfetch_by_ref - FETCH sys_ref_cursor INTO targets; * sp_instr_cclose_by_ref - CLOSE sys_ref_cursor; * sp_instr_destruct_variable - to destruct SYS_REFCURSOR variables when the execution goes out of the BEGIN..END block where SYS_REFCURSOR variables are declared. - New methods in LEX: * sp_open_cursor_for_stmt - handles "OPEN sys_ref_cursor FOR stmt". * sp_add_instr_fetch_cursor - "FETCH cur INTO targets" for both static cursors and SYS_REFCURSORs. * sp_close - handles "CLOSE cur" both for static cursors and SYS_REFCURSORs. - Changes in cursor functions to handle both static cursors and SYS_REFCURSORs: * Item_func_cursor_isopen * Item_func_cursor_found * Item_func_cursor_notfound * Item_func_cursor_rowcount - A new system variable @@max_open_cursors - to limit the number of cursors (static and SYS_REFCURSORs) opened at the same time. Its allowed range is [0-65536], with 50 by default. - A new virtual method Type_handler::can_return_bool() telling if calling item->val_bool() is allowed for Items of this data type, or if otherwise the "Illegal parameter for operation" error should be raised at fix_fields() time. - New methods in Sp_rcontext_handler: * get_cursor() * get_cursor_by_ref() - A new class Sp_rcontext_handler_statement to handle top level statement wide cursors which are shared by all substatements. - A new virtual method expr_event_handler() in classes Item and Field. It's needed to close (and make available for a new OPEN) unused THD::m_statement_cursors elements which do not have any references any more. It can happen in various moments in time, e.g. * after evaluation parameters of an SQL routine * after assigning a cursor expression into a SYS_REFCURSOR variable * when leaving a BEGIN..END block with SYS_REFCURSOR variables * after setting OUT/INOUT routine actual parameters from formal parameters.	2025-03-18 18:31:28 +01:00