component_sys_var_service.h File Reference

#include <stddef.h>
#include <mysql/components/service.h>
#include <nulls.h>
#include <mysql/components/services/bits/system_variables_bits.h>

Go to the source code of this file.

Classes
struct	TYPE_LIB
	A utility class for the ENUM variables. More...
struct	s_mysql_component_sys_variable_register
	Service to register variable and get variable value. More...
struct	s_mysql_component_sys_variable_unregister
	Service to unregister variable. More...

Macros
#define	MYSQL_THD   THD *
#define	INTEGRAL_CHECK_ARG(type)
	Defines an integral placeholder to fill in with values and pass to the registration function. More...
#define	ENUM_CHECK_ARG(type)
	Defines an TYPE_LIB placeholder to fill in with values and pass to the registration function. More...
#define	BOOL_CHECK_ARG(type)
	Defines a bool placeholder to fill in with values and pass to the registration function. More...
#define	STR_CHECK_ARG(type)
	Defines a char * placeholder to fill in with values and pass to the registration function. More...

Typedefs
typedef int(*	mysql_sys_var_check_func) (MYSQL_THD thd, SYS_VAR *var, void *save, struct st_mysql_value *value)
	Signature for the check function. More...
typedef void(*	mysql_sys_var_update_func) (MYSQL_THD thd, SYS_VAR *var, void *val_ptr, const void *save)
	Signature for the update function. More...
typedef struct s_mysql_component_sys_variable_register	mysql_service_component_sys_variable_register_t
	Service to register variable and get variable value. More...
typedef struct s_mysql_component_sys_variable_unregister	mysql_service_component_sys_variable_unregister_t
	Service to unregister variable. More...

Macro Definition Documentation

MYSQL_THD

#define MYSQL_THD   THD *

Typedef Documentation

mysql_sys_var_check_func

typedef int(* mysql_sys_var_check_func) (MYSQL_THD thd, SYS_VAR *var, void *save, struct st_mysql_value *value)

Signature for the check function.

This is called to check if the value supplied is valid and can be set as a new variable value at that time. It needs to extract the value supplied from the value API pointer. Note that extracting this value can be expensive (e.g. a scalar subquery) hence it should be done only once. This is why the result of this should be stored into the save output parameter so that it can be further reused by update() etc. For a multi-variable SET statement the server will first call all of the check functions and only if they all return success it will start calling the update functions. So the idea is that the update function should succeed no matter what. And all the necessary checks should be done in the check function. If you do not supply a check or update function the server will use the basic ones to check e.g. min and max values for the integer types etc.

Parameters

	thd	The thread handle to the current thread
	var	handle to the system variable definition
[out]	save	placeholder for the value. This should be cast according to the type
	value	Interface to extract the actual parameter value.

Returns

status

Return values

0	success
1	failure

See also

mysql_sys_var_update_func, mysql_service_component_sys_variable_register_t

mysql_sys_var_update_func

typedef void(* mysql_sys_var_update_func) (MYSQL_THD thd, SYS_VAR *var, void *val_ptr, const void *save)

Signature for the update function.

This is called to set the updated value into the var_ptr placeholder and invoke any side effects that may stem from setting this system variable.

It receives the pre-calculated value (usually from mysql_sys_var_check_func) in the save pointer. It needs to set it into the var_ptr pointer and invoke any side effects.

For a multi-variable SET statement the server will first call all of the check functions and only if they all return success it will start calling the update functions. So the idea is that the update function should succeed no matter what. And all the necessary checks should be done in the check function. If you do not supply an update function the server will use the basic one to set the value according to the variable's type.

Parameters

	thd	The thread handle to the current thread
	var	handle to the system variable definition
[out]	val_ptr	placeholder for the value. Store save in here.
	save	The pre-calculated value from check.

See also

mysql_sys_var_check_func, mysql_service_component_sys_variable_register_t