Atomic_sysvar< T > Class Template Reference

A helper class for numeric sysvars which can be read in thread-safe way. More...

#include <ut0atomic_sysvar.h>

Classes
struct	Data
	Contains all members of Atomic_sysvar<T> in a standard layout struct - which, among other things, means we can't mix private with public, use virtual methods, nor std::function<>. More...

Public Member Functions
	Atomic_sysvar (void(*after_change)())
	Constructs the atomic sysvar, initializes its value to zero and makes sure innodb_init_params() will remember to copy the nonatomic value to atomic value once Server layer finishes modifying the nonatomic value during its initialization. More...
T	load () const
	Get the current value of the sys-var without UB. More...
T &	registrable ()
	Get the variable which we want to register via plugin API. More...

Static Public Member Functions
static void	update (THD *, SYS_VAR *, void *target, const void *new_value)
	This is on-update handler registered via plugin API for all sysvars of this type. More...

Private Attributes
struct Atomic_sysvar::Data	m_data

Detailed Description

template<typename T>
class Atomic_sysvar< T >

A helper class for numeric sysvars which can be read in thread-safe way.

Constructor & Destructor Documentation

Atomic_sysvar()

template<typename T >

Atomic_sysvar< T >::Atomic_sysvar ( void(*)()  after_change )

inlineexplicit

Constructs the atomic sysvar, initializes its value to zero and makes sure innodb_init_params() will remember to copy the nonatomic value to atomic value once Server layer finishes modifying the nonatomic value during its initialization.

Parameters

[in]

after_change

A callback to be called after value changed due to SET or recovery of value stored with SET PERSIST.

Member Function Documentation

load()

template<typename T >

T Atomic_sysvar< T >::load ( ) const

inline

Get the current value of the sys-var without UB.

registrable()

template<typename T >

T & Atomic_sysvar< T >::registrable ( )

inline

Get the variable which we want to register via plugin API.

Do not use this method in InnoDB code - use load() instead.

update()

template<typename T >

static void Atomic_sysvar< T >::update ( THD *  , SYS_VAR *  , void *  target, const void *  new_value  )

inlinestatic

This is on-update handler registered via plugin API for all sysvars of this type.

It is called after new value was validated, but before it was assigned. It is the responsibility of this function to assign new_value to target.

Parameters

[in]	target	This points to Data::m_nonatomic
[in]	new_value	This is the new value to be assigned to the sysvar

Member Data Documentation

m_data

template<typename T >

struct Atomic_sysvar::Data Atomic_sysvar< T >::m_data

private

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The documentation for this class was generated from the following file:

• storage/innobase/include/ut0atomic_sysvar.h