Set_variables_helper Class Reference

A helper class to fascilitate executing SET on system variables. More...

#include <set_variables_helper.h>

Public Member Functions
	Set_variables_helper (THD *existing_thd)
	Initializes the helper and switches to the canned temp LEX. More...
	~Set_variables_helper ()
bool	add_variable (const char *prefix, size_t prefix_length, const char *suffix, size_t suffix_length, Item *variable_value, enum_var_type var_type)
	Adds setting one variable instruction. More...
bool	execute ()
	Executes the SET command for all variables added. More...
THD *	get_thd ()
bool	is_auto_thd ()
bool	check_variable_update_type (const char *prefix, size_t prefix_length, const char *suffix, size_t suffix_length, Item *variable_value)
	Checks the update type for the system variable and throws error if any found. More...

Private Attributes
List< set_var_base >	m_sysvar_list
THD *	m_thd
LEX *	m_lex_save
LEX	m_lex_tmp
Storing_auto_THD *	m_thd_auto

Detailed Description

A helper class to fascilitate executing SET on system variables.

Runs in the current THD, but in a temp LEX to avoid polluting the THD::lex with the changes.

Useful for service implementations looking to set values to system variables.

Should be used in a single THD.

A proper usage is something of the sort:

THD *curr_thd = ...; Item *value1 = Item_int(20), *val2= Item_int(30);

Set_variables_helper hlp(curr_thd);

if (hlp.add_variable(nullptr, 0, "foo", 3, enum_var_type::PERSIST_ONLY, value1)) return true;

if (hlp.add_variable("bar", 3, "baz", 3, enum_var_type::PERSIST, val2)) return true;

...

if (hlp->execute()) return true;

The above executes the following command SET PERSIST_ONLY foo = 20, PERSIST bar.baz = 30;

See also

sql_set_variables

Constructor & Destructor Documentation

Set_variables_helper()

Set_variables_helper::Set_variables_helper

(

THD *

existing_thd

)

Initializes the helper and switches to the canned temp LEX.

Parameters

existing_thd

the THD to execute on.

~Set_variables_helper()

Set_variables_helper::~Set_variables_helper

(

)

Member Function Documentation

add_variable()

bool Set_variables_helper::add_variable	(	const char *	prefix,
		size_t	prefix_length,
		const char *	suffix,
		size_t	suffix_length,
		Item *	variable_value,
		enum_var_type	var_type
	)

Adds setting one variable instruction.

Adds a:

<var_type> [prefix.]suffix = variable_value

to the SET command being constructed.

Parameters

prefix	the prefix for the variable name or nullptr if none
prefix_length	length of prefix, 0 if empty
suffix	the name of the variable to set. Must be nonnull
suffix_length	the length of suffix
variable_value	the value to set
var_type	how to set: PERSIST, PERSIST_ONLY etc

Return values

true	failure
false	success

check_variable_update_type()

bool Set_variables_helper::check_variable_update_type	(	const char *	prefix,
		size_t	prefix_length,
		const char *	suffix,
		size_t	suffix_length,
		Item *	variable_value
	)

Checks the update type for the system variable and throws error if any found.

Parameters

prefix	the prefix for the variable name or nullptr if none
prefix_length	length of prefix, 0 if empty
suffix	the name of the variable to set. Must be nonnull
suffix_length	the length of suffix
variable_value	the value to set

Return values

true	failure
false	success

execute()

bool Set_variables_helper::execute

(

)

Executes the SET command for all variables added.

Return values

true	failure
false	success

get_thd()

THD * Set_variables_helper::get_thd ( )

inline

is_auto_thd()

bool Set_variables_helper::is_auto_thd ( )

inline

Member Data Documentation

m_lex_save

LEX* Set_variables_helper::m_lex_save

private

m_lex_tmp

LEX Set_variables_helper::m_lex_tmp

private

m_sysvar_list

List<set_var_base> Set_variables_helper::m_sysvar_list

private

m_thd

THD* Set_variables_helper::m_thd

private

m_thd_auto

Storing_auto_THD* Set_variables_helper::m_thd_auto

private

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

• sql/server_component/set_variables_helper.h
• sql/server_component/set_variables_helper.cc