mariadb/sql/sp_rcontext.h
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

466 lines
16 KiB
C++

/* -*- C++ -*- */
/* Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved.
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 02110-1335 USA */
#ifndef _SP_RCONTEXT_H_
#define _SP_RCONTEXT_H_
#include "sql_class.h" // select_result_interceptor
#include "sp_pcontext.h" // sp_condition_value
#include "sp_rcontext_handler.h"
///////////////////////////////////////////////////////////////////////////
// sp_rcontext declaration.
///////////////////////////////////////////////////////////////////////////
class sp_cursor;
class sp_lex_keeper;
class sp_instr_cpush;
class sp_instr_hpush_jump;
class Query_arena;
class sp_head;
class Item_cache;
class Virtual_tmp_table;
/*
This class is a runtime context of a Stored Routine. It is used in an
execution and is intended to contain all dynamic objects (i.e. objects, which
can be changed during execution), such as:
- stored routine variables;
- cursors;
- handlers;
Runtime context is used with sp_head class. sp_head class is intended to
contain all static things, related to the stored routines (code, for example).
sp_head instance creates runtime context for the execution of a stored
routine.
There is a parsing context (an instance of sp_pcontext class), which is used
on parsing stage. However, now it contains some necessary for an execution
things, such as definition of used stored routine variables. That's why
runtime context needs a reference to the parsing context.
*/
class sp_rcontext : public Sql_alloc
{
public:
/// Construct and properly initialize a new sp_rcontext instance. The static
/// create-function is needed because we need a way to return an error from
/// the constructor.
///
/// @param thd Thread handle.
/// @param root_parsing_ctx Top-level parsing context for this stored program.
/// @param return_value_fld Field object to store the return value
/// (for stored functions only).
///
/// @return valid sp_rcontext object or NULL in case of OOM-error.
static sp_rcontext *create(THD *thd,
sp_head *owner,
const sp_pcontext *root_parsing_ctx,
Field *return_value_fld,
Row_definition_list &defs);
~sp_rcontext();
private:
sp_rcontext(sp_head *owner,
const sp_pcontext *root_parsing_ctx,
Field *return_value_fld,
bool in_sub_stmt);
// Prevent use of copying constructor and operator.
sp_rcontext(const sp_rcontext &);
void operator=(sp_rcontext &);
public:
/// This class stores basic information about SQL-condition, such as:
/// - SQL error code;
/// - error level;
/// - SQLSTATE;
/// - text message.
///
/// It's used to organize runtime SQL-handler call stack.
///
/// Standard Sql_condition class can not be used, because we don't always have
/// an Sql_condition object for an SQL-condition in Diagnostics_area.
///
/// Eventually, this class should be moved to sql_error.h, and be a part of
/// standard SQL-condition processing (Diagnostics_area should contain an
/// object for active SQL-condition, not just information stored in DA's
/// fields).
class Sql_condition_info : public Sql_alloc,
public Sql_condition_identity
{
public:
/// Text message.
char *message;
/** Row number where the condition has happened */
ulong m_row_number;
/// The constructor.
///
/// @param _sql_condition The SQL condition.
/// @param arena Query arena for SP
Sql_condition_info(const Sql_condition *_sql_condition, Query_arena *arena)
:Sql_condition_identity(*_sql_condition)
{
message= strdup_root(arena->mem_root, _sql_condition->get_message_text());
m_row_number= _sql_condition->m_row_number;
}
};
private:
/// This class represents a call frame of SQL-handler (one invocation of a
/// handler). Basically, it's needed to store continue instruction pointer for
/// CONTINUE SQL-handlers.
class Handler_call_frame : public Sql_alloc
{
public:
/// SQL-condition, triggered handler activation.
const Sql_condition_info *sql_condition;
/// Continue-instruction-pointer for CONTINUE-handlers.
/// The attribute contains 0 for EXIT-handlers.
uint continue_ip;
/// The constructor.
///
/// @param _sql_condition SQL-condition, triggered handler activation.
/// @param _continue_ip Continue instruction pointer.
Handler_call_frame(const Sql_condition_info *_sql_condition,
uint _continue_ip)
:sql_condition(_sql_condition),
continue_ip(_continue_ip)
{ }
};
public:
/// Arena used to (re) allocate items on. E.g. reallocate INOUT/OUT
/// SP-variables when they don't fit into prealloced items. This is common
/// situation with String items. It is used mainly in sp_eval_func_item().
Query_arena *callers_arena;
/// Flag to end an open result set before start executing an SQL-handler
/// (if one is found). Otherwise the client will hang due to a violation
/// of the client/server protocol.
bool end_partial_result_set;
bool pause_state;
bool quit_func;
uint instr_ptr;
/// The stored program for which this runtime context is created. Used for
/// checking if correct runtime context is used for variable handling,
/// and to access the package run-time context.
/// Also used by slow log.
sp_head *m_sp;
/////////////////////////////////////////////////////////////////////////
// SP-variables.
/////////////////////////////////////////////////////////////////////////
uint argument_count() const
{
return m_root_parsing_ctx->context_var_count();
}
uint max_var_index() const
{
return (uint) m_var_items.size();
}
/*
Return:
- for functions and procedures - 0.
- for PACKAGE BODY - the number of its package-wide variables,
which must keep their values even after running of
the PACKAGE BODY executable initialization secion.
*/
uint persistent_variable_count() const
{
/*
The top level sp_pcontext contains function and procedure paramenters.
In case of a PACKAGE BODY there are no parameters, the context for
parameters still exists, with no variables.
PACKAGE BODY variables are in m_root_parsing_ctx->child_context(0).
*/
const sp_pcontext *pc= m_root_parsing_ctx->child_context(0);
if (pc && pc->scope() == sp_pcontext::PACKAGE_BODY_SCOPE)
{
DBUG_ASSERT(m_root_parsing_ctx->context_var_count() == 0); // No params
return pc->current_var_count();
}
return 0;
}
int set_variable(THD *thd, uint var_idx, Item **value);
int set_variable_row_field(THD *thd, uint var_idx, uint field_idx,
Item **value);
int set_variable_row_field_by_name(THD *thd, uint var_idx,
const LEX_CSTRING &field_name,
Item **value);
int set_variable_row(THD *thd, uint var_idx, List<Item> &items);
int set_parameter(THD *thd, uint var_idx, Item **value)
{
DBUG_ASSERT(var_idx < argument_count());
return set_variable(thd, var_idx, value);
}
Item_field *get_variable(uint var_idx) const
{ return m_var_items[var_idx]; }
Item **get_variable_addr(uint var_idx) const
{ return ((Item **) m_var_items.array()) + var_idx; }
Item_field *get_parameter(uint var_idx) const
{
DBUG_ASSERT(var_idx < argument_count());
return get_variable(var_idx);
}
bool find_row_field_by_name_or_error(uint *field_idx, uint var_idx,
const LEX_CSTRING &field_name);
bool set_return_value(THD *thd, Item **return_value_item);
/*
Run the event handler for all SP variables (i.e. Fields in m_var_table)
in the range [start..end-1].
*/
void expr_event_handler(THD *thd, expr_event_t event, uint start, uint end);
/*
Run the event (e.g. destruction) handler for all variables
except PACKAGE BODY variables, which must keep their values even after
running of the PACKAGE BODY executable initialization secion.
*/
void expr_event_handler_not_persistent(THD *thd, expr_event_t event)
{
uint start= thd->spcont->persistent_variable_count();
uint end= max_var_index();
return expr_event_handler(thd, event, start, end);
}
bool is_return_value_set() const
{ return m_return_value_set; }
/////////////////////////////////////////////////////////////////////////
// Parameters.
/////////////////////////////////////////////////////////////////////////
uint get_inited_param_count() const
{ return m_inited_params_count; }
void set_inited_param_count(uint count)
{ m_inited_params_count= count; }
/////////////////////////////////////////////////////////////////////////
// SQL-handlers.
/////////////////////////////////////////////////////////////////////////
/// Push an sp_instr_hpush_jump instance to the handler call stack.
///
/// @param entry The condition handler entry
///
/// @return error flag.
/// @retval false on success.
/// @retval true on error.
bool push_handler(sp_instr_hpush_jump *entry);
/// Pop and delete given number of instances from the handler
/// call stack.
///
/// @param count Number of handler entries to pop & delete.
void pop_handlers(size_t count);
const Sql_condition_info *raised_condition() const
{
return m_handler_call_stack.elements() ?
(*m_handler_call_stack.back())->sql_condition : NULL;
}
/// Handle current SQL condition (if any).
///
/// This is the public-interface function to handle SQL conditions in
/// stored routines.
///
/// @param thd Thread handle.
/// @param ip[out] Instruction pointer to the first handler
/// instruction.
/// @param cur_spi Current SP instruction.
///
/// @retval true if an SQL-handler has been activated. That means, all of
/// the following conditions are satisfied:
/// - the SP-instruction raised SQL-condition(s),
/// - and there is an SQL-handler to process at least one of those
/// SQL-conditions,
/// - and that SQL-handler has been activated.
/// Note, that the return value has nothing to do with "error flag"
/// semantics.
///
/// @retval false otherwise.
bool handle_sql_condition(THD *thd,
uint *ip,
const sp_instr *cur_spi);
/// Remove latest call frame from the handler call stack.
///
/// @param da Diagnostics area containing handled conditions.
///
/// @return continue instruction pointer of the removed handler.
uint exit_handler(Diagnostics_area *da);
/////////////////////////////////////////////////////////////////////////
// Cursors.
/////////////////////////////////////////////////////////////////////////
/// Push a cursor to the cursor stack.
///
/// @param cursor The cursor
///
void push_cursor(sp_cursor *cur);
void pop_cursor(THD *thd);
/// Pop and delete given number of sp_cursor instance from the cursor stack.
///
/// @param count Number of cursors to pop & delete.
void pop_cursors(THD *thd, size_t count);
void pop_all_cursors(THD *thd)
{ pop_cursors(thd, m_ccount); }
sp_cursor *get_cursor(uint i) const
{ return m_cstack[i]; }
/////////////////////////////////////////////////////////////////////////
// CASE expressions.
/////////////////////////////////////////////////////////////////////////
/// Set CASE expression to the specified value.
///
/// @param thd Thread handler.
/// @param case_expr_id The CASE expression identifier.
/// @param case_expr_item The CASE expression value
///
/// @return error flag.
/// @retval false on success.
/// @retval true on error.
///
/// @note The idea is to reuse Item_cache for the expression of the one
/// CASE statement. This optimization takes place when there is CASE
/// statement inside of a loop. So, in other words, we will use the same
/// object on each iteration instead of creating a new one for each
/// iteration.
///
/// TODO
/// Hypothetically, a type of CASE expression can be different for each
/// iteration. For instance, this can happen if the expression contains
/// a session variable (something like @@VAR) and its type is changed
/// from one iteration to another.
///
/// In order to cope with this problem, we check type each time, when we
/// use already created object. If the type does not match, we re-create
/// Item. This also can (should?) be optimized.
bool set_case_expr(THD *thd, int case_expr_id, Item **case_expr_item_ptr);
Item *get_case_expr(int case_expr_id) const
{ return m_case_expr_holders[case_expr_id]; }
Item ** get_case_expr_addr(int case_expr_id) const
{ return (Item**) m_case_expr_holders.array() + case_expr_id; }
private:
/// Internal function to allocate memory for arrays.
///
/// @param thd Thread handle.
///
/// @return error flag: false on success, true in case of failure.
bool alloc_arrays(THD *thd);
/// Create and initialize a table to store SP-variables.
///
/// param thd Thread handle.
///
/// @return error flag.
/// @retval false on success.
/// @retval true on error.
bool init_var_table(THD *thd, List<Spvar_definition> &defs);
/// Create and initialize an Item-adapter (Item_field) for each SP-var field.
///
/// param thd Thread handle.
///
/// @return error flag.
/// @retval false on success.
/// @retval true on error.
bool init_var_items(THD *thd, List<Spvar_definition> &defs);
/// Create an instance of appropriate Item_cache class depending on the
/// specified type in the callers arena.
///
/// @note We should create cache items in the callers arena, as they are
/// used between in several instructions.
///
/// @param thd Thread handler.
/// @param item Item to get the expression type.
///
/// @return Pointer to valid object on success, or NULL in case of error.
Item_cache *create_case_expr_holder(THD *thd, const Item *item) const;
Virtual_tmp_table *virtual_tmp_table_for_row(uint idx);
private:
/// Top-level (root) parsing context for this runtime context.
const sp_pcontext *m_root_parsing_ctx;
/// Virtual table for storing SP-variables.
Virtual_tmp_table *m_var_table;
/// Collection of Item_field proxies, each of them points to the
/// corresponding field in m_var_table.
Bounds_checked_array<Item_field *> m_var_items;
/// This is a pointer to a field, which should contain return value for
/// stored functions (only). For stored procedures, this pointer is NULL.
Field *m_return_value_fld;
/// Indicates whether the return value (in m_return_value_fld) has been
/// set during execution.
bool m_return_value_set;
/// Flag to tell if the runtime context is created for a sub-statement.
bool m_in_sub_stmt;
/// Stack of visible handlers.
Dynamic_array<sp_instr_hpush_jump *> m_handlers;
/// Stack of caught SQL conditions.
Dynamic_array<Handler_call_frame *> m_handler_call_stack;
/// Stack of cursors.
Bounds_checked_array<sp_cursor *> m_cstack;
/// Current number of cursors in m_cstack.
uint m_ccount;
/// Array of CASE expression holders.
Bounds_checked_array<Item_cache *> m_case_expr_holders;
/// Number of parameters initialized by the callee. This is used to
/// determine which parameters should be initialized with the default value.
uint m_inited_params_count;
}; // class sp_rcontext : public Sql_alloc
#endif /* _SP_RCONTEXT_H_ */