SE_cost_constants Class Reference

Cost constants for a storage engine. More...

#include <opt_costconstants.h>

Public Member Functions
	SE_cost_constants ()
virtual	~SE_cost_constants ()=default
double	memory_block_read_cost () const
	Cost of reading one random block from an in-memory database buffer. More...
double	io_block_read_cost () const
	Cost of reading one random block from disk. More...

Protected Member Functions
virtual cost_constant_error	set (const LEX_CSTRING &name, const double value, bool default_value)
	Set the value of one of the cost constants. More...
cost_constant_error	update (const LEX_CSTRING &name, const double value)
	Update the value of a cost constant. More...
cost_constant_error	update_default (const LEX_CSTRING &name, const double value)
	Update the default value of a cost constant. More...
void	update_cost_value (double *cost_constant, bool *cost_constant_is_default, double new_value, bool new_value_is_default)
	Utility function for changing the value of a cost constant. More...

Private Attributes
double	m_memory_block_read_cost
	Cost constant for reading a random block from an in-memory buffer. More...
double	m_io_block_read_cost
	Cost constant for reading a random disk block. More...
bool	m_memory_block_read_cost_default
	Whether the memory_block_read_cost is a default value or not. More...
bool	m_io_block_read_cost_default
	Whether the io_block_read_cost is a default value or not. More...

Static Private Attributes
static const double	MEMORY_BLOCK_READ_COST = 0.25
	Default cost for reading a random block from an in-memory buffer. More...
static const double	IO_BLOCK_READ_COST = 1.0
	Default cost for reading a random disk block. More...

Friends
class	Cost_model_constants

Detailed Description

Cost constants for a storage engine.

Storage engines that want to add new cost constants should make a subclass of this class.

Constructor & Destructor Documentation

SE_cost_constants()

SE_cost_constants::SE_cost_constants ( )

inline

~SE_cost_constants()

virtual SE_cost_constants::~SE_cost_constants ( )

virtualdefault

Member Function Documentation

io_block_read_cost()

double SE_cost_constants::io_block_read_cost ( ) const

inline

Cost of reading one random block from disk.

memory_block_read_cost()

double SE_cost_constants::memory_block_read_cost ( ) const

inline

Cost of reading one random block from an in-memory database buffer.

set()

cost_constant_error SE_cost_constants::set ( const LEX_CSTRING &  name, const double  value, bool  default_value  )

protectedvirtual

Set the value of one of the cost constants.

If a storage engine wants to introduce a new cost constant, it should provide an implementation of this function. If the cost constant is not recognized by the function in the subclass, then this function should be called to allow the cost constant in the base class to be given the updated value.

Parameters

name	name of cost constant
value	new value
default_value	specify whether the new value is a default value or an engine specific value

Returns

Status for updating the cost constant

update()

cost_constant_error SE_cost_constants::update ( const LEX_CSTRING &  name, const double  value  )

protected

Update the value of a cost constant.

Parameters

name	name of the cost constant
value	the new value this cost constant should take

Returns

Status for updating the cost constant

update_cost_value()

void SE_cost_constants::update_cost_value ( double *  cost_constant, bool *  cost_constant_is_default, double  new_value, bool  new_value_is_default  )

protected

Utility function for changing the value of a cost constant.

The cost constant will be updated to the new value iff: a) the current value is the default value, or b) the current value is not the default value and the new value is not a default value

Parameters

[out]	cost_constant	pointer to the cost constant that should be updated
[in,out]	cost_constant_is_default	whether the current value has the default value or not
	new_value	the new value for the cost constant
	new_value_is_default	whether this is a new default value or not

update_default()

cost_constant_error SE_cost_constants::update_default ( const LEX_CSTRING &  name, const double  value  )

protected

Update the default value of a cost constant.

If this const constant already has been given a non-default value, then calling this will have no effect on the current value for the cost constant.

Parameters

name	name of the cost constant
value	the new value this cost constant should take

Returns

Status for updating the cost constant

Friends And Related Function Documentation

Cost_model_constants

friend class Cost_model_constants

friend

Member Data Documentation

IO_BLOCK_READ_COST

const double SE_cost_constants::IO_BLOCK_READ_COST = 1.0

staticprivate

Default cost for reading a random disk block.

m_io_block_read_cost

double SE_cost_constants::m_io_block_read_cost

private

Cost constant for reading a random disk block.

m_io_block_read_cost_default

bool SE_cost_constants::m_io_block_read_cost_default

private

Whether the io_block_read_cost is a default value or not.

m_memory_block_read_cost

double SE_cost_constants::m_memory_block_read_cost

private

Cost constant for reading a random block from an in-memory buffer.

m_memory_block_read_cost_default

bool SE_cost_constants::m_memory_block_read_cost_default

private

Whether the memory_block_read_cost is a default value or not.

MEMORY_BLOCK_READ_COST

const double SE_cost_constants::MEMORY_BLOCK_READ_COST = 0.25

staticprivate

Default cost for reading a random block from an in-memory buffer.

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

• sql/opt_costconstants.h
• sql/opt_costconstants.cc