Class mdbx::cache_entry

ClassList > mdbx > cache_entry

Cache entry for the transparent read-your-writes caching, see txn::get_cached() andmdbx_cache_get() .More...

#include <mdbx.h++>

Inherits the following classes: MDBX_cache_entry_t

Public Attributes inherited from MDBX_cache_entry_t

See MDBX_cache_entry_t

Type	Name
uint64_t	last_confirmed_txnid
uint32_t	length
size_t	offset
uint64_t	trunk_txnid

Public Functions

Type	Name
	cache_entry () noexcept Constructs the entry and initializes it to the "no cached info" state.
	cache_entry (const cache_entry &) noexcept Copy constructor.
	cache_entry (cache_entry && other) noexcept Move constructor: copies the source entry and resets it.
constexpr	cache_entry (const MDBX_cache_entry_t & ce) noexcept Constructs the entry as a copy of the given C API structure.
uint64_t	last_confirmed () noexcept const Returns the recent transaction/MVCC-snapshot ID wherein the entry was checked and confirmed.
bool	notfound () noexcept const Returns `true` if the entry caches the "key not found" state.
cache_entry &	operator= (const cache_entry &) noexcept Copy assignment operator.
cache_entry &	operator= (const MDBX_cache_entry_t & ce) noexcept Assigns the given C API structure to this entry.
void	reset () noexcept Initializes the cache entry to the "no cached info" state.
uint64_t	transaction_id () noexcept const Returns the transaction/MVCC-snapshot ID of the internal structure that holds the cached data.

Detailed Description

A value type wrapping MDBX_cache_entry_t. Each entry is associated with a key and holds a lightweight "version stamp" plus the offset of the cached value inside the memory-mapped database file, so subsequent lookups stop as soon as they reach an unmodified page.

An entry must be initialized (reset()) before the first use. Entries may be placed in shared memory and used by multiple processes, though libmdbx does not provide such interaction management yet.

Public Functions Documentation

function cache_entry [1/4]

Constructs the entry and initializes it to the "no cached info" state.

inline mdbx::cache_entry::cache_entry () noexcept

function cache_entry [2/4]

Copy constructor.

mdbx::cache_entry::cache_entry (
    const cache_entry &
) noexcept

function cache_entry [3/4]

Move constructor: copies the source entry and resets it.

inline mdbx::cache_entry::cache_entry (
    cache_entry && other
) noexcept

Parameters:

other The source entry to be moved from.

function cache_entry [4/4]

Constructs the entry as a copy of the given C API structure.

inline constexpr mdbx::cache_entry::cache_entry (
    const MDBX_cache_entry_t & ce
) noexcept

Parameters:

ce The source MDBX_cache_entry_t instance.

function last_confirmed

Returns the recent transaction/MVCC-snapshot ID wherein the entry was checked and confirmed.

inline uint64_t mdbx::cache_entry::last_confirmed () noexcept const

Returns:

The transaction ID of the last confirmation.

function notfound

Returns true if the entry caches the "key not found" state.

inline bool mdbx::cache_entry::notfound () noexcept const

Returns:

true if the entry caches the "not found" state.

function operator=

Copy assignment operator.

cache_entry & mdbx::cache_entry::operator= (
    const cache_entry &
) noexcept

Returns:

A reference to this instance.

function operator=

Assigns the given C API structure to this entry.

inline cache_entry & mdbx::cache_entry::operator= (
    const MDBX_cache_entry_t & ce
) noexcept

Parameters:

ce The source MDBX_cache_entry_t instance.

Returns:

A reference to this instance.

function reset

Initializes the cache entry to the "no cached info" state.

inline void mdbx::cache_entry::reset () noexcept

function transaction_id

Returns the transaction/MVCC-snapshot ID of the internal structure that holds the cached data.

inline uint64_t mdbx::cache_entry::transaction_id () noexcept const

Returns:

The transaction ID of the internal structure.

Friends Documentation

friend operator!=

inline bool mdbx::cache_entry::operator!= (
    const cache_entry & a,
    const cache_entry & b
) noexcept

friend operator==

inline bool mdbx::cache_entry::operator== (
    const cache_entry & a,
    const cache_entry & b
) noexcept

The documentation for this class was generated from the following file mdbx.h++