Wrapper interface for all kinds of system variables. More...

#include <set_var.h>

Classes
struct	Cache

struct	Component

struct	Keycache

struct	Plugin

struct	Static

Public Types
enum	Lifetime { STATIC , KEYCACHE , PLUGIN , COMPONENT }

typedef Prealloced_array< System_variable_tracker, SYSTEM_VARIABLE_PREALLOC >	Array

Public Member Functions
	System_variable_tracker (const System_variable_tracker &)

	~System_variable_tracker ()

void	operator= (System_variable_tracker &&)

Lifetime	lifetime () const

bool	operator== (const System_variable_tracker &x) const

bool	is_keycache_var () const

bool	eq_static_sys_var (const sys_var *var) const

const char *	get_var_name () const

std::string_view	get_keycache_name () const

bool	is_hint_updateable () const

bool	access_system_variable (THD thd, std::function< void(const System_variable_tracker &, sys_var )> function={}, Suppress_not_found_error suppress_not_found_error=Suppress_not_found_error::NO, Force_sensitive_system_variable_access force_sensitive_variable_access=Force_sensitive_system_variable_access::NO, Is_already_locked is_already_locked=Is_already_locked::NO, Is_single_thread is_single_thread=Is_single_thread::NO) const

template<typename T >
std::optional< T >	access_system_variable (THD thd, std::function< T(const System_variable_tracker &, sys_var )> function, Suppress_not_found_error suppress_not_found_error=Suppress_not_found_error::NO, Force_sensitive_system_variable_access force_sensitive_variable_access=Force_sensitive_system_variable_access::NO, Is_already_locked is_already_locked=Is_already_locked::NO, Is_single_thread is_single_thread=Is_single_thread::NO) const
	Safely pass a sys_var object to a function. More...

SHOW_TYPE	cached_show_type () const

bool	cached_is_sensitive () const

Static Public Member Functions
static System_variable_tracker	make_tracker (std::string_view prefix, std::string_view suffix)
	Static "constructor". More...

static System_variable_tracker	make_tracker (std::string_view multipart_name)
	Static "constructor". More...

static bool	enumerate_sys_vars (bool sort, enum enum_var_type type, bool strict, Array *output)
	Constructs an array of system variables for display to the user. More...

Public Attributes
friend	Array

sys_var *	m_static_var

struct {
sys_var * m_static_var

}	m_static

char	m_keycache_var_name [NAME_LEN+sizeof(".key_cache_division_limit")]
	A dot-separated key cache name or, for a reduced form of key cache variable names, a key cache property name as specified by the caller of System_variable_tracker::make_traker(). More...

size_t	m_keycache_name_size

sys_var *	m_keycache_var

struct {
char m_keycache_var_name [NAME_LEN+sizeof(".key_cache_division_limit")]
	A dot-separated key cache name or, for a reduced form of key cache variable names, a key cache property name as specified by the caller of System_variable_tracker::make_traker(). More...

size_t m_keycache_name_size

sys_var * m_keycache_var

}	m_keycache

char	m_plugin_var_name [NAME_LEN+1]
	A "_"-separated plugin-registered variables name. More...

sys_var *	m_plugin_var_cache

struct {
char m_plugin_var_name [NAME_LEN+1]
	A "_"-separated plugin-registered variables name. More...

sys_var * m_plugin_var_cache

}	m_plugin

char	m_component_var_name [NAME_LEN+sizeof('.')+NAME_LEN+1]
	A dot-separated component-registered variable name. More...

sys_var *	m_component_var_cache

struct {
char m_component_var_name [NAME_LEN+sizeof('.')+NAME_LEN+1]
	A dot-separated component-registered variable name. More...

sys_var * m_component_var_cache

}	m_component

Static Public Attributes
static constexpr size_t	SYSTEM_VARIABLE_PREALLOC = 200
	Number of system variable elements to preallocate. More...

Private Member Functions
	System_variable_tracker (Static, sys_var *var)

	System_variable_tracker (Keycache, std::string_view cache_name, sys_var *var)

	System_variable_tracker (Plugin, std::string_view name)

	System_variable_tracker (Component, std::string_view dot_separated_name)

	System_variable_tracker (Component, std::string_view component_name, std::string_view variable_name)

sys_var *	get_stable_var () const

bool	visit_plugin_variable (THD , std::function< bool(sys_var )>, Suppress_not_found_error, Is_already_locked, Is_single_thread) const

bool	visit_component_variable (THD , std::function< bool(sys_var )>, Suppress_not_found_error, Is_already_locked, Is_single_thread) const

void	cache_metadata (THD thd, sys_var v) const

Static Private Member Functions
static bool	enumerate_sys_vars_in_hash (collation_unordered_map< std::string, sys_var * > hash, enum enum_var_type query_scope, bool strict, System_variable_tracker::Array output)

static bool	names_are_same (const char , const char )

Private Attributes
Lifetime	m_tag

std::optional< Cache >	m_cache

union {
struct {
sys_var * m_static_var

} m_static

struct {
char m_keycache_var_name [NAME_LEN+sizeof(".key_cache_division_limit")]
	A dot-separated key cache name or, for a reduced form of key cache variable names, a key cache property name as specified by the caller of System_variable_tracker::make_traker(). More...

size_t m_keycache_name_size

sys_var * m_keycache_var

} m_keycache

struct {
char m_plugin_var_name [NAME_LEN+1]
	A "_"-separated plugin-registered variables name. More...

sys_var * m_plugin_var_cache

} m_plugin

struct {
char m_component_var_name [NAME_LEN+sizeof('.')+NAME_LEN+1]
	A dot-separated component-registered variable name. More...

sys_var * m_component_var_cache

} m_component

};

Static Private Attributes
static thread_local int	m_hash_lock_recursion_depth {0}
	A non-zero value suppresses LOCK_system_variables_hash guards in System_variable_tracker::access_system_variable. More...

Detailed Description

Wrapper interface for all kinds of system variables.

The interface encapsulates parse- and execution-time resolvers for all kinds of sys_var: regular (static) system variables MyISAM Multiple Key Cache variables plugin-registered variables component-registered variables Encapsulation of system variable resolving and data accessing tasks.

Member Typedef Documentation

◆ Array

typedef Prealloced_array<System_variable_tracker, SYSTEM_VARIABLE_PREALLOC> System_variable_tracker::Array

Member Enumeration Documentation

◆ Lifetime

enum System_variable_tracker::Lifetime

Enumerator
STATIC	for regular static variables
KEYCACHE	for MyISAM Multiple Key Cache variables
PLUGIN	for plugin-registered system variables
COMPONENT	for component-registered variables

Constructor & Destructor Documentation

◆ System_variable_tracker() [1/6]

System_variable_tracker::System_variable_tracker	(	Static	,
		sys_var *	var
	)

private

◆ System_variable_tracker() [2/6]

System_variable_tracker::System_variable_tracker	(	Keycache	,
		std::string_view	cache_name,
		sys_var *	var
	)

private

◆ System_variable_tracker() [3/6]

System_variable_tracker::System_variable_tracker	(	Plugin	,
		std::string_view	name
	)

private

◆ System_variable_tracker() [4/6]

System_variable_tracker::System_variable_tracker	(	Component	,
		std::string_view	dot_separated_name
	)

private

◆ System_variable_tracker() [5/6]

System_variable_tracker::System_variable_tracker	(	Component	,
		std::string_view	component_name,
		std::string_view	variable_name
	)

private

◆ System_variable_tracker() [6/6]

System_variable_tracker::System_variable_tracker ( const System_variable_tracker & x )

◆ ~System_variable_tracker()

System_variable_tracker::~System_variable_tracker ( )

Member Function Documentation

◆ access_system_variable() [1/2]

template<typename T >

std::optional< T > System_variable_tracker::access_system_variable	(	THD *	thd,
		std::function< T(const System_variable_tracker &, sys_var *)>	function,
		Suppress_not_found_error	suppress_not_found_error = `Suppress_not_found_error::NO`,
		Force_sensitive_system_variable_access	force_sensitive_variable_access = `Force_sensitive_system_variable_access::NO`,
		Is_already_locked	is_already_locked = `Is_already_locked::NO`,
		Is_single_thread	is_single_thread = `Is_single_thread::NO`
	)		const

inline

Safely pass a sys_var object to a function.

Template variant.

access_system_variable() is the most important interface: it does necessary locks, if a dynamic variable is inaccessible then access_system_variable() exits returning empty std::option, otherwise it calls function and returns the result value of function to the caller.

See the pseudo code part at the comment above a signature of the non-template variant of access_system_variable() for details (replace "return true" with "return std::option{}" and "return false" with "return result value of anonymous function call").

Template Parameters

T	A type of a return value of the callback function.

Parameters

thd	A connection handler or nullptr.
function	A function to pass a sys_var object if the latest is accessible.
suppress_not_found_error	Suppress or output ER_UNKNOWN_SYSTEM_VARIABLE if a dynamic variable is unavailable.
force_sensitive_variable_access	Suppress privilege check for SENSITIVE variables.
is_already_locked	YES means LOCK_system_variables_hash has already been taken.
is_single_thread	YES means we are called from mysqld_main, during bootstrap.

Returns: No value if the dynamic variable is unavailable, otherwise a value of type T returned by the callback function.

◆ access_system_variable() [2/2]

bool System_variable_tracker::access_system_variable	(	THD *	thd,
		std::function< void(const System_variable_tracker &, sys_var *)>	function = `{}`,
		Suppress_not_found_error	suppress_not_found_error = `Suppress_not_found_error::NO`,
		Force_sensitive_system_variable_access	force_sensitive_variable_access = `Force_sensitive_system_variable_access::NO`,
		Is_already_locked	is_already_locked = `Is_already_locked::NO`,
		Is_single_thread	is_single_thread = `Is_single_thread::NO`
	)		const

Safely pass a sys_var object to a function. Non-template variant.

access_system_variable() is the most important interface:
it does necessary locks,
if a dynamic variable is inaccessible it exits,
otherwise it calls @p function.
access_system_variable() is reentrant:
being called recursively it suppresses double locks.

Simplified pseudo code of access_system_variable() implementation:

    if system variable is @@session_track_system_variables {

a special case: the system variable is static, but it references a comma-separated list of other system variables if function is not no-op { process @session_track_system_variables as plugin-registered one } else { return false // success } } if system variable is static or key cache variable { no dictionary/plugin locks needed call function(cached sys_var pointer) return false // success } if system variable is plugin-registered one { if need to hold LOCK_system_variables_hash { acquire read-only LOCK_system_variables_hash } if need to hold LOCK_plugin { acquire LOCK_plugin, unlock on exit } find sys_var if found { intern_plugin_lock } if this function acquired LOCK_plugin { release LOCK_plugin } if this function acquired LOCK_system_variables_hash { release LOCK_system_variables_hash } if not found or plugin is not in the PLUGIN_IS_READY state { return true // error: variable not found or } call function(found sys_var pointer) return false // success } if system variable is component-registered one { if need to hold LOCK_system_variables_hash(**) { acquire read-only LOCK_system_variables_hash, unlock on exit } find sys_var if not found { return true } call function(found sys_var pointer) return false // success }

Parameters

thd	A connection handler or nullptr.
function	An optional anonymous function to pass a sys_var object if the latest is accessible.
suppress_not_found_error	Suppress or output ER_UNKNOWN_SYSTEM_VARIABLE if a dynamic variable is unavailable.
force_sensitive_variable_access	Suppress privilege check for SENSITIVE variables.
is_already_locked	YES means LOCK_system_variables_hash has already been taken.
is_single_thread	YES means we are called from mysqld_main, during bootstrap.

Returns: True if the dynamic variable is unavailable, otherwise false.

◆ cache_metadata()

void System_variable_tracker::cache_metadata	(	THD *	thd,
		sys_var *	v
	)		const

private

◆ cached_is_sensitive()

bool System_variable_tracker::cached_is_sensitive ( ) const

inline

◆ cached_show_type()

SHOW_TYPE System_variable_tracker::cached_show_type ( ) const

inline

◆ enumerate_sys_vars()

bool System_variable_tracker::enumerate_sys_vars	(	bool	sort,
		enum enum_var_type	query_scope,
		bool	strict,
		System_variable_tracker::Array *	output
	)

static

Constructs an array of system variables for display to the user.

Parameters

output	Prealloced_array of elements for display
sort	If true, the system variables should be sorted
query_scope	OPT_GLOBAL or OPT_SESSION for SHOW GLOBAL\|SESSION VARIABLES
strict	Use strict scope checking

Returns: True on error, false otherwise

Note: Requires r/o lock on LOCK_system_variables_hash.

◆ enumerate_sys_vars_in_hash()

bool System_variable_tracker::enumerate_sys_vars_in_hash	(	collation_unordered_map< std::string, sys_var * > *	hash,
		enum enum_var_type	query_scope,
		bool	strict,
		System_variable_tracker::Array *	output
	)

staticprivate

◆ eq_static_sys_var()

bool System_variable_tracker::eq_static_sys_var ( const sys_var * var ) const

inline

◆ get_keycache_name()

std::string_view System_variable_tracker::get_keycache_name ( ) const

inline

Returns: 1) not normalized names of MyISAM Multiple Key Caches, also can return empty string for the implicit prefix (i.e. implicit "DEFAULT."). 2) empty string for the rest of system variables.

◆ get_stable_var()

sys_var * System_variable_tracker::get_stable_var ( ) const

inlineprivate

◆ get_var_name()

const char * System_variable_tracker::get_var_name ( ) const

Returns: 1) normalized names of regular system variables; 2) user-specified dot-separated names of key cache variables, or user-specified unqualified names of default key cache property names; 3) user-specified names of plugin-registered variables; 4) user-specified dot-separated names of component-registered variables.

◆ is_hint_updateable()

bool System_variable_tracker::is_hint_updateable ( ) const

inline

Returns: true if the underlying variable can be referenced in the SET_VAR optimizer hint syntax, otherwise false.

◆ is_keycache_var()

bool System_variable_tracker::is_keycache_var ( ) const

inline

◆ lifetime()

Lifetime System_variable_tracker::lifetime ( ) const

inline

◆ make_tracker() [1/2]

System_variable_tracker System_variable_tracker::make_tracker ( std::string_view multipart_name )

static

Static "constructor".

Note: This function requires no locks and allocates nothing on memory heaps.

Parameters

multipart_name Variable name, optionally dot-separated.

Returns: System_variable_tracker object

◆ make_tracker() [2/2]

System_variable_tracker System_variable_tracker::make_tracker	(	std::string_view	prefix,
		std::string_view	suffix
	)

static

Static "constructor".

Note: This function requires no locks and allocates nothing on memory heaps.

Parameters

prefix	One of: component name, MyISAM Multiple Key Cache name, or empty string.
suffix	In a dot-separated syntax (`prefix` is mandatory): component-registered variable name, or MyISAM Multiple Key Cache property name. Otherwise (`is` empty): name of static or plugin-registered variables.

Returns: System_variable_tracker object

◆ names_are_same()

bool System_variable_tracker::names_are_same	(	const char *	a,
		const char *	b
	)

staticprivate

◆ operator=()

void System_variable_tracker::operator= ( System_variable_tracker && x )

◆ operator==()

bool System_variable_tracker::operator== ( const System_variable_tracker & x ) const

inline

◆ visit_component_variable()

bool System_variable_tracker::visit_component_variable	(	THD *	thd,
		std::function< bool(sys_var *)>	function,
		Suppress_not_found_error	suppress_not_found_error,
		Is_already_locked	is_already_locked,
		Is_single_thread	is_single_thread
	)		const

private

◆ visit_plugin_variable()

bool System_variable_tracker::visit_plugin_variable	(	THD *	thd,
		std::function< bool(sys_var *)>	function,
		Suppress_not_found_error	suppress_not_found_error,
		Is_already_locked	is_already_locked,
		Is_single_thread	is_single_thread
	)		const

private

Member Data Documentation

◆

union { ... } System_variable_tracker::@156

◆ Array

friend System_variable_tracker::Array

◆ m_cache

std::optional<Cache> System_variable_tracker::m_cache

mutableprivate

◆

struct { ... } System_variable_tracker::m_component

◆ m_component_var_cache

sys_var* System_variable_tracker::m_component_var_cache

mutable

◆ m_component_var_name

char System_variable_tracker::m_component_var_name[NAME_LEN+sizeof('.')+NAME_LEN+1]

A dot-separated component-registered variable name.

◆ m_hash_lock_recursion_depth

thread_local int System_variable_tracker::m_hash_lock_recursion_depth {0}

staticprivate

A non-zero value suppresses LOCK_system_variables_hash guards in System_variable_tracker::access_system_variable.

◆

struct { ... } System_variable_tracker::m_keycache

◆ m_keycache_name_size

size_t System_variable_tracker::m_keycache_name_size

◆ m_keycache_var

sys_var* System_variable_tracker::m_keycache_var

◆ m_keycache_var_name

char System_variable_tracker::m_keycache_var_name[NAME_LEN+sizeof(".key_cache_division_limit")]

A dot-separated key cache name or, for a reduced form of key cache variable names, a key cache property name as specified by the caller of System_variable_tracker::make_traker().

◆

struct { ... } System_variable_tracker::m_plugin

◆ m_plugin_var_cache

sys_var* System_variable_tracker::m_plugin_var_cache

mutable

◆ m_plugin_var_name

char System_variable_tracker::m_plugin_var_name[NAME_LEN+1]

A "_"-separated plugin-registered variables name.

◆

struct { ... } System_variable_tracker::m_static

◆ m_static_var

sys_var* System_variable_tracker::m_static_var

◆ m_tag

Lifetime System_variable_tracker::m_tag

private

◆ SYSTEM_VARIABLE_PREALLOC

constexpr size_t System_variable_tracker::SYSTEM_VARIABLE_PREALLOC = 200

staticconstexpr

Number of system variable elements to preallocate.

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

sql/set_var.h
sql/set_var.cc

Classes

Public Types

Public Member Functions

Static Public Member Functions

Public Attributes

Static Public Attributes

Private Member Functions

Static Private Member Functions

Private Attributes

Static Private Attributes

Detailed Description

Member Typedef Documentation

◆ Array

Member Enumeration Documentation

◆ Lifetime

Constructor & Destructor Documentation

◆ System_variable_tracker() [1/6]

◆ System_variable_tracker() [2/6]

◆ System_variable_tracker() [3/6]

◆ System_variable_tracker() [4/6]

◆ System_variable_tracker() [5/6]

◆ System_variable_tracker() [6/6]

◆ ~System_variable_tracker()

Member Function Documentation

◆ access_system_variable() [1/2]

◆ access_system_variable() [2/2]

◆ cache_metadata()

◆ cached_is_sensitive()

◆ cached_show_type()

◆ enumerate_sys_vars()

◆ enumerate_sys_vars_in_hash()

◆ eq_static_sys_var()

◆ get_keycache_name()

◆ get_stable_var()

◆ get_var_name()

◆ is_hint_updateable()

◆ is_keycache_var()

◆ lifetime()

◆ make_tracker() [1/2]

◆ make_tracker() [2/2]

◆ names_are_same()

◆ operator=()

◆ operator==()

◆ visit_component_variable()

◆ visit_plugin_variable()

Member Data Documentation

◆

◆ Array

◆ m_cache

◆

◆ m_component_var_cache

◆ m_component_var_name

◆ m_hash_lock_recursion_depth

◆

◆ m_keycache_name_size

◆ m_keycache_var

◆ m_keycache_var_name

◆

◆ m_plugin_var_cache

◆ m_plugin_var_name

◆

◆ m_static_var

◆ m_tag

◆ SYSTEM_VARIABLE_PREALLOC