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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.
74 lines
2.5 KiB
C++
74 lines
2.5 KiB
C++
/*
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Copyright (c) 2025, MariaDB Corporation.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */
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#ifdef MYSQL_SERVER
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#include "mariadb.h"
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#include "sql_class.h"
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/*
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Append a new element into the array.
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@return NULL Type_ref_null (with is_null()==true) on error (EOM).
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@return not-NULL Type_ref_null on success
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*/
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Type_ref_null sp_cursor_array::append(THD *thd)
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{
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if (Dynamic_array::append(sp_cursor_array_element()))
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{
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DBUG_ASSERT(thd->is_error());
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return Type_ref_null();
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}
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return Type_ref_null((ulonglong) size() - 1);
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}
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/*
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Find a cursor by reference.
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@param thd - the current THD
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@param ref - the field behind a SYS_REFCURSOR SP variable
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@param for_open - if the cursor is needed for OPEN rather than FETCH/CLOSE,
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so a new cursor is appended if not found.
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*/
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sp_cursor_array_element *sp_cursor_array::get_cursor_by_ref(THD *thd,
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Field *ref_field,
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bool for_open)
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{
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Type_ref_null ref= ref_field->val_ref(thd);
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if (ref < (ulonglong) elements())
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return &at((size_t) ref.value());// "ref" points to an initialized sp_cursor
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if (!for_open)
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return nullptr;
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/*
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We are here when:
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- The reference ref.is_null() is true, meaning that the
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ref_field's SP variable is not linked to any cursors in "this" array:
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* it is the very first "OPEN .. FOR STMT" command for ref_field.
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* or the ref_field's SP variable was set to NULL explicitly.
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- Or ref_field for some reasons returned a cursor offset outside
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or the range [0..elements()-1].
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*/
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if (((ref= find_unused()).is_null() && (ref= append(thd)).is_null()) ||
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ref_field->store_ref(ref, true/*no_conversions*/))
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return nullptr;
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at((size_t) ref.value()).reset(thd, 1/*ref count*/);
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return &at((size_t) ref.value());
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}
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#endif // MYSQL_SERVER
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