Cost_model_table Class Reference

API for getting cost estimates for operations on table data. More...

#include <opt_costmodel.h>

Public Member Functions
	Cost_model_table ()
void	init (const Cost_model_server *cost_model_server, const TABLE *table)
	Initializes the cost model object. More...
double	row_evaluate_cost (double rows) const
	Cost of processing a number of records and evaluating the query condition on the records. More...
double	key_compare_cost (double keys) const
	Cost of doing a number of key compare operations. More...
double	io_block_read_cost (double blocks) const
	Cost of reading a number of random blocks from a table. More...
double	buffer_block_read_cost (double blocks) const
	Cost of reading a number of blocks from the storage engine when the block is already in a memory buffer. More...
double	page_read_cost (double pages) const
	Cost of reading a number of random pages from a table. More...
double	page_read_cost_index (uint index, double pages) const
	Cost of reading a number of random pages from an index. More...
double	disk_seek_base_cost () const
	The fixed part of the cost for doing a sequential seek on disk. More...
double	disk_seek_cost (double seek_blocks) const
	Cost estimate for a sequential disk seek where a given number of blocks are skipped. More...

Protected Attributes
const Cost_model_server *	m_cost_model_server
	Pointer to the cost model for the query. More...
const SE_cost_constants *	m_se_cost_constants
	Cost constants for the storage engine that stores the table. More...
bool	m_initialized
	Used for detecting if this object is used without having been initialized. More...

Private Member Functions
double	disk_seek_prop_cost () const
	The cost for seeking past one block in a sequential seek. More...

Private Attributes
const TABLE *	m_table
	The table that this is the cost model for. More...

Detailed Description

API for getting cost estimates for operations on table data.

Note

The initial implementation mostly has functions for accessing cost constants for basic operations.

Constructor & Destructor Documentation

Cost_model_table()

Cost_model_table::Cost_model_table ( )

inline

Member Function Documentation

buffer_block_read_cost()

double Cost_model_table::buffer_block_read_cost ( double  blocks ) const

inline

Cost of reading a number of blocks from the storage engine when the block is already in a memory buffer.

Parameters

blocks

number of blocks to read

Returns

Cost estimate

disk_seek_base_cost()

double Cost_model_table::disk_seek_base_cost ( ) const

inline

The fixed part of the cost for doing a sequential seek on disk.

For a harddisk, this corresponds to half a rotation (see comment for get_sweep_read_cost() in handler.cc).

disk_seek_cost()

double Cost_model_table::disk_seek_cost ( double  seek_blocks ) const

inline

Cost estimate for a sequential disk seek where a given number of blocks are skipped.

Parameters

seek_blocks

number of blocks to seek past

Returns

The cost estimate for the seek operation

disk_seek_prop_cost()

double Cost_model_table::disk_seek_prop_cost ( ) const

inlineprivate

The cost for seeking past one block in a sequential seek.

For a harddisk, this represents the cost of having to move the disk head to the correct cylinder.

init()

void Cost_model_table::init	(	const Cost_model_server *	cost_model_server,
		const TABLE *	table
	)

Initializes the cost model object.

This function must be called before calling any cost estimation functions for a query. It should also be called when starting optimization of a new query in case any cost estimate constants have changed.

Parameters

cost_model_server	the main cost model object for this query
table	the table the cost model should be used for

io_block_read_cost()

double Cost_model_table::io_block_read_cost ( double  blocks ) const

inline

Cost of reading a number of random blocks from a table.

Parameters

blocks

number of blocks to read

Returns

Cost estimate

key_compare_cost()

double Cost_model_table::key_compare_cost ( double  keys ) const

inline

Cost of doing a number of key compare operations.

Parameters

keys	number of key compare operations

Returns

Cost of comparing the keys

page_read_cost()

double Cost_model_table::page_read_cost

(

double

pages

)

const

Cost of reading a number of random pages from a table.

Parameters

pages

number of pages to read

Returns

Cost estimate

page_read_cost_index()

double Cost_model_table::page_read_cost_index	(	uint	index,
		double	pages
	)		const

Cost of reading a number of random pages from an index.

Parameters

index	the index number
pages	number of pages to read

Returns

Cost estimate

row_evaluate_cost()

double Cost_model_table::row_evaluate_cost ( double  rows ) const

inline

Cost of processing a number of records and evaluating the query condition on the records.

Parameters

rows	number of rows to evaluate

Returns

Cost of evaluating the records

Member Data Documentation

m_cost_model_server

const Cost_model_server* Cost_model_table::m_cost_model_server

protected

Pointer to the cost model for the query.

This is used for getting cost estimates for server operations.

m_initialized

bool Cost_model_table::m_initialized

protected

Used for detecting if this object is used without having been initialized.

m_se_cost_constants

const SE_cost_constants* Cost_model_table::m_se_cost_constants

protected

Cost constants for the storage engine that stores the table.

m_table

const TABLE* Cost_model_table::m_table

private

The table that this is the cost model for.

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

• sql/opt_costmodel.h
• sql/opt_costmodel.cc