hash_table_t Class Reference

#include <hash0hash.h>

Public Member Functions
	hash_table_t (size_t n)
	~hash_table_t ()
size_t	get_n_cells () const
	Returns number of cells in cells[] array. More...
const ut::fast_modulo_t	get_n_cells_fast_modulo () const
	Returns a helper class for calculating fast modulo n_cells. More...
void	set_n_cells (size_t n)
	Sets the number of n_cells, to the provided one. More...

Public Attributes
enum hash_table_sync_t	type = HASH_TABLE_SYNC_NONE
	Either: a) HASH_TABLE_SYNC_NONE in which case n_sync_obj is 0 and rw_locks is nullptr or b) HASH_TABLE_SYNC_RW_LOCK in which case n_sync_obj > 0 is the number of rw_locks elements, each of which protects a disjoint fraction of cells. More...
bool	adaptive = false
ut::unique_ptr< hash_cell_t[]>	cells
	The pointer to the array of cells. More...
size_t	n_sync_obj = 0
	if rw_locks != nullptr, then it's their number (must be a power of two). More...
rw_lock_t *	rw_locks = nullptr
	nullptr, or an array of n_sync_obj rw_locks used to protect segments of the hash table. More...
mem_heap_t *	heap = nullptr
uint32_t	magic_n = HASH_TABLE_MAGIC_N

Static Public Attributes
static constexpr uint32_t	HASH_TABLE_MAGIC_N = 76561114

Private Attributes
std::atomic< size_t >	n_cells
	The number of cells in the hash table. More...
ut::mt_fast_modulo_t	n_cells_fast_modulo
	Utility to calculate the modulo n_cells fast. More...

Constructor & Destructor Documentation

hash_table_t()

hash_table_t::hash_table_t ( size_t  n )

inline

~hash_table_t()

hash_table_t::~hash_table_t ( )

inline

Member Function Documentation

get_n_cells()

size_t hash_table_t::get_n_cells ( ) const

inline

Returns number of cells in cells[] array.

If type==HASH_TABLE_SYNC_RW_LOCK it can be used:

• without any latches to peek a value, before hash_lock_[sx]_confirm
• when holding S-latch for at least one n_sync_obj to get the "real" value

  Returns

  value of n_cells

get_n_cells_fast_modulo()

const ut::fast_modulo_t hash_table_t::get_n_cells_fast_modulo ( ) const

inline

Returns a helper class for calculating fast modulo n_cells.

If type==HASH_TABLE_SYNC_RW_LOCK it can be used:

• without any latches to peek a value, before hash_lock_[sx]_confirm
• when holding S-latch for at least one n_sync_obj to get the "real" value

set_n_cells()

void hash_table_t::set_n_cells ( size_t  n )

inline

Sets the number of n_cells, to the provided one.

If type==HASH_TABLE_SYNC_RW_LOCK it can be used only when holding x-latches on all shards.

Parameters

[in]

n

The new size of cells[] array

Member Data Documentation

adaptive

bool hash_table_t::adaptive = false

cells

ut::unique_ptr<hash_cell_t[]> hash_table_t::cells

The pointer to the array of cells.

If type==HASH_TABLE_SYNC_RW_LOCK it is:

• modified when holding X-latches on all n_sync_obj
• read when holding an S-latch for at least one n_sync_obj

HASH_TABLE_MAGIC_N

constexpr uint32_t hash_table_t::HASH_TABLE_MAGIC_N = 76561114

staticconstexpr

heap

mem_heap_t* hash_table_t::heap = nullptr

magic_n

uint32_t hash_table_t::magic_n = HASH_TABLE_MAGIC_N

n_cells

std::atomic<size_t> hash_table_t::n_cells

private

The number of cells in the hash table.

If type==HASH_TABLE_SYNC_RW_LOCK it is:

• modified when holding X-latches on all n_sync_obj
• read
  • without any latches to peek a value, before hash_lock_[sx]_confirm
  • when holding S-latch for at least one n_sync_obj to get the "real" value

n_cells_fast_modulo

ut::mt_fast_modulo_t hash_table_t::n_cells_fast_modulo

private

Utility to calculate the modulo n_cells fast.

It is set together with n_cells. It can be read without latches in parallel to set_n_cells, and as it is a complex object, it is not set atomically. Because of this the multi-threaded version is used.

n_sync_obj

size_t hash_table_t::n_sync_obj = 0

if rw_locks != nullptr, then it's their number (must be a power of two).

Otherwise, 0. Is zero iff the type is HASH_TABLE_SYNC_NONE.

rw_locks

rw_lock_t* hash_table_t::rw_locks = nullptr

nullptr, or an array of n_sync_obj rw_locks used to protect segments of the hash table.

Is nullptr iff the type is HASH_TABLE_SYNC_NONE.

type

enum hash_table_sync_t hash_table_t::type = HASH_TABLE_SYNC_NONE

Either: a) HASH_TABLE_SYNC_NONE in which case n_sync_obj is 0 and rw_locks is nullptr or b) HASH_TABLE_SYNC_RW_LOCK in which case n_sync_obj > 0 is the number of rw_locks elements, each of which protects a disjoint fraction of cells.

The default type of hash_table is HASH_TABLE_SYNC_NONE i.e.: the caller is responsible for access control to the table.

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

• storage/innobase/include/hash0hash.h