mdbx::txn Class Reference

Unmanaged database transaction. More...

#include <mdbx.h++>

Inherited by mdbx::txn_managed.

Public Types
using	info = ::MDBX_txn_info
using	map_stat = ::MDBX_stat
using	canary = ::MDBX_canary

Public Member Functions
MDBX_CXX11_CONSTEXPR	txn () noexcept=default
	txn (const txn &) noexcept=default
txn &	operator= (txn &&other) noexcept
	txn (txn &&other) noexcept
	~txn () noexcept
MDBX_CXX14_CONSTEXPR	operator bool () const noexcept
MDBX_CXX14_CONSTEXPR	operator const MDBX_txn * () const
MDBX_CXX14_CONSTEXPR	operator MDBX_txn * ()
inline ::mdbx::env	env () const noexcept
	Returns the transaction's environment. More...
MDBX_txn_flags_t	flags () const
	Returns transaction's flags. More...
uint64_t	id () const
	Return the transaction's ID. More...
bool	is_dirty (const void *ptr) const
	Checks whether the given data is on a dirty page. More...
bool	is_readonly () const
	Checks whether the transaction is read-only. More...
bool	is_readwrite () const
	Checks whether the transaction is read-write. More...
info	get_info (bool scan_reader_lock_table=false) const
	Returns information about the MDBX transaction. More...
size_t	size_max () const
	Returns maximal write transaction size (i.e. limit for summary volume of dirty pages) in bytes. More...
size_t	size_current () const
	Returns current write transaction size (i.e.summary volume of dirty pages) in bytes. More...
void	reset_reading ()
	Reset a read-only transaction. More...
void	renew_reading ()
	Renew a read-only transaction. More...
txn_managed	start_nested ()
	Start nested write transaction. More...
cursor_managed	open_cursor (map_handle map)
	Opens cursor for specified key-value map handle. More...
map_handle	open_map (const char *name, const ::mdbx::key_mode key_mode=::mdbx::key_mode::usual, const ::mdbx::value_mode value_mode=::mdbx::value_mode::single) const
	Open existing key-value map. More...
map_handle	open_map (const ::std::string &name, const ::mdbx::key_mode key_mode=::mdbx::key_mode::usual, const ::mdbx::value_mode value_mode=::mdbx::value_mode::single) const
	Open existing key-value map. More...
map_handle	create_map (const char *name, const ::mdbx::key_mode key_mode=::mdbx::key_mode::usual, const ::mdbx::value_mode value_mode=::mdbx::value_mode::single)
	Create new or open existing key-value map. More...
map_handle	create_map (const ::std::string &name, const ::mdbx::key_mode key_mode=::mdbx::key_mode::usual, const ::mdbx::value_mode value_mode=::mdbx::value_mode::single)
	Create new or open existing key-value map. More...
void	drop_map (map_handle map)
	Drops key-value map using handle. More...
bool	drop_map (const char *name, bool throw_if_absent=false)
	Drops key-value map using name. More...
bool	drop_map (const ::std::string &name, bool throw_if_absent=false)
	Drop key-value map. More...
void	clear_map (map_handle map)
	Clear key-value map. More...
bool	clear_map (const char *name, bool throw_if_absent=false)
bool	clear_map (const ::std::string &name, bool throw_if_absent=false)
map_stat	get_map_stat (map_handle map) const
	Returns statistics for a sub-database. More...
uint32_t	get_tree_deepmask (map_handle map) const
	Returns depth (bitmask) information of nested dupsort (multi-value) B+trees for given database. More...
map_handle::info	get_handle_info (map_handle map) const
	Returns information about key-value map (aka sub-database) handle. More...
txn &	put_canary (const canary &)
	Set integers markers (aka "canary") associated with the environment. More...
canary	get_canary () const
	Returns fours integers markers (aka "canary") associated with the environment. More...
uint64_t	sequence (map_handle map) const
uint64_t	sequence (map_handle map, uint64_t increment)
	Reads and increment sequence generator associated with a key-value map (aka sub-database). More...
int	compare_keys (map_handle map, const slice &a, const slice &b) const noexcept
	Compare two keys according to a particular key-value map (aka sub-database). More...
int	compare_values (map_handle map, const slice &a, const slice &b) const noexcept
	Compare two values according to a particular key-value map (aka sub-database). More...
int	compare_keys (map_handle map, const pair &a, const pair &b) const noexcept
	Compare keys of two pairs according to a particular key-value map (aka sub-database). More...
int	compare_values (map_handle map, const pair &a, const pair &b) const noexcept
	Compare values of two pairs according to a particular key-value map (aka sub-database). More...
slice	get (map_handle map, const slice &key) const
	Get value by key from a key-value map (aka sub-database). More...
slice	get (map_handle map, slice key, size_t &values_count) const
	Get first of multi-value and values count by key from a key-value multimap (aka sub-database). More...
slice	get (map_handle map, const slice &key, const slice &value_at_absence) const
	Get value by key from a key-value map (aka sub-database). More...
slice	get (map_handle map, slice key, size_t &values_count, const slice &value_at_absence) const
	Get first of multi-value and values count by key from a key-value multimap (aka sub-database). More...
pair_result	get_equal_or_great (map_handle map, const slice &key) const
	Get value for equal or great key from a database. More...
pair_result	get_equal_or_great (map_handle map, const slice &key, const slice &value_at_absence) const
	Get value for equal or great key from a database. More...
MDBX_error_t	put (map_handle map, const slice &key, slice *value, MDBX_put_flags_t flags) noexcept
void	put (map_handle map, const slice &key, slice value, put_mode mode)
void	insert (map_handle map, const slice &key, slice value)
value_result	try_insert (map_handle map, const slice &key, slice value)
slice	insert_reserve (map_handle map, const slice &key, size_t value_length)
value_result	try_insert_reserve (map_handle map, const slice &key, size_t value_length)
void	upsert (map_handle map, const slice &key, const slice &value)
slice	upsert_reserve (map_handle map, const slice &key, size_t value_length)
void	update (map_handle map, const slice &key, const slice &value)
bool	try_update (map_handle map, const slice &key, const slice &value)
slice	update_reserve (map_handle map, const slice &key, size_t value_length)
value_result	try_update_reserve (map_handle map, const slice &key, size_t value_length)
bool	erase (map_handle map, const slice &key)
	Removes all values for given key. More...
bool	erase (map_handle map, const slice &key, const slice &value)
	Removes the particular multi-value entry of the key. More...
void	replace (map_handle map, const slice &key, slice old_value, const slice &new_value)
	Replaces the particular multi-value of the key with a new value. More...
template<class ALLOCATOR , typename CAPACITY_POLICY >
buffer< ALLOCATOR, CAPACITY_POLICY >	extract (map_handle map, const slice &key, const typename buffer< ALLOCATOR, CAPACITY_POLICY >::allocator_type &allocator=buffer< ALLOCATOR, CAPACITY_POLICY >::allocator_type())
	Removes and return a value of the key. More...
template<class ALLOCATOR , typename CAPACITY_POLICY >
buffer< ALLOCATOR, CAPACITY_POLICY >	replace (map_handle map, const slice &key, const slice &new_value, const typename buffer< ALLOCATOR, CAPACITY_POLICY >::allocator_type &allocator=buffer< ALLOCATOR, CAPACITY_POLICY >::allocator_type())
	Replaces and returns a value of the key with new one. More...
template<class ALLOCATOR , typename CAPACITY_POLICY >
buffer< ALLOCATOR, CAPACITY_POLICY >	replace_reserve (map_handle map, const slice &key, slice &new_value, const typename buffer< ALLOCATOR, CAPACITY_POLICY >::allocator_type &allocator=buffer< ALLOCATOR, CAPACITY_POLICY >::allocator_type())
void	append (map_handle map, const slice &key, const slice &value, bool multivalue_order_preserved=true)
	Adding a key-value pair, provided that ascending order of the keys and (optionally) values are preserved. More...
size_t	put_multiple (map_handle map, const slice &key, const size_t value_length, const void *values_array, size_t values_count, put_mode mode, bool allow_partial=false)
template<typename VALUE >
void	put_multiple (map_handle map, const slice &key, const ::std::vector< VALUE > &vector, put_mode mode)
ptrdiff_t	estimate (map_handle map, pair from, pair to) const
ptrdiff_t	estimate (map_handle map, slice from, slice to) const
ptrdiff_t	estimate_from_first (map_handle map, slice to) const
ptrdiff_t	estimate_to_last (map_handle map, slice from) const

Protected Member Functions
MDBX_CXX11_CONSTEXPR	txn (MDBX_txn *ptr) noexcept

Protected Attributes
MDBX_txn *	handle_ {nullptr}

Friends
class	cursor
MDBX_CXX11_CONSTEXPR bool	operator== (const txn &a, const txn &b) noexcept
MDBX_CXX11_CONSTEXPR bool	operator!= (const txn &a, const txn &b) noexcept

Detailed Description

Unmanaged database transaction.

Like other unmanaged classes, txn allows copying and assignment for instances, but does not destroys the represented underlying object from the own class destructor.

All database operations require a transaction handle. Transactions may be read-only or read-write.

Member Typedef Documentation

canary

using mdbx::txn::canary = ::MDBX_canary

info

using mdbx::txn::info = ::MDBX_txn_info

map_stat

using mdbx::txn::map_stat = ::MDBX_stat

Constructor & Destructor Documentation

txn() [1/4]

MDBX_CXX11_CONSTEXPR mdbx::txn::txn ( MDBX_txn *  ptr )

protectednoexcept

txn() [2/4]

MDBX_CXX11_CONSTEXPR mdbx::txn::txn ( )

defaultnoexcept

txn() [3/4]

mdbx::txn::txn ( const txn &  )

defaultnoexcept

txn() [4/4]

mdbx::txn::txn ( txn &&  other )

inlinenoexcept

~txn()

mdbx::txn::~txn ( )

inlinenoexcept

Member Function Documentation

append()

void mdbx::txn::append ( map_handle  map, const slice &  key, const slice &  value, bool  multivalue_order_preserved = true  )

inline

Adding a key-value pair, provided that ascending order of the keys and (optionally) values are preserved.

Instead of splitting the full b+tree pages, the data will be placed on new ones. Thus appending is about two times faster than insertion, and the pages will be filled in completely mostly but not half as after splitting ones. On the other hand, any subsequent insertion or update with an increase in the length of the value will be twice as slow, since it will require splitting already filled pages.

Parameters

[in]	map	A map handle to append
[in]	key	A key to be append
[in]	value	A value to store with the key
[in]	multivalue_order_preserved	If multivalue_order_preserved == true then the same rules applied for to pages of nested b+tree of multimap's values.

clear_map() [1/3]

bool mdbx::txn::clear_map ( const ::std::string &  name, bool  throw_if_absent = false  )

inline

Returns

True if the key-value map existed and was cleared, either false if the key-value map did not exist and there is nothing to clear.

clear_map() [2/3]

bool mdbx::txn::clear_map	(	const char *	name,
		bool	throw_if_absent = false
	)

Returns

True if the key-value map existed and was cleared, either false if the key-value map did not exist and there is nothing to clear.

clear_map() [3/3]

void mdbx::txn::clear_map ( map_handle  map )

inline

Clear key-value map.

compare_keys() [1/2]

int mdbx::txn::compare_keys ( map_handle  map, const pair &  a, const pair &  b  ) const

inlinenoexcept

Compare keys of two pairs according to a particular key-value map (aka sub-database).

compare_keys() [2/2]

int mdbx::txn::compare_keys ( map_handle  map, const slice &  a, const slice &  b  ) const

inlinenoexcept

Compare two keys according to a particular key-value map (aka sub-database).

compare_values() [1/2]

int mdbx::txn::compare_values ( map_handle  map, const pair &  a, const pair &  b  ) const

inlinenoexcept

Compare values of two pairs according to a particular key-value map (aka sub-database).

compare_values() [2/2]

int mdbx::txn::compare_values ( map_handle  map, const slice &  a, const slice &  b  ) const

inlinenoexcept

Compare two values according to a particular key-value map (aka sub-database).

create_map() [1/2]

mdbx::map_handle mdbx::txn::create_map ( const ::std::string &  name, const ::mdbx::key_mode  key_mode = ::mdbx::key_mode::usual, const ::mdbx::value_mode  value_mode = ::mdbx::value_mode::single  )

inline

Create new or open existing key-value map.

create_map() [2/2]

mdbx::map_handle mdbx::txn::create_map ( const char *  name, const ::mdbx::key_mode  key_mode = ::mdbx::key_mode::usual, const ::mdbx::value_mode  value_mode = ::mdbx::value_mode::single  )

inline

Create new or open existing key-value map.

drop_map() [1/3]

bool mdbx::txn::drop_map ( const ::std::string &  name, bool  throw_if_absent = false  )

inline

Drop key-value map.

Returns

True if the key-value map existed and was deleted, either false if the key-value map did not exist and there is nothing to delete.

drop_map() [2/3]

bool mdbx::txn::drop_map	(	const char *	name,
		bool	throw_if_absent = false
	)

Drops key-value map using name.

Returns

True if the key-value map existed and was deleted, either false if the key-value map did not exist and there is nothing to delete.

drop_map() [3/3]

void mdbx::txn::drop_map ( map_handle  map )

inline

Drops key-value map using handle.

env()

mdbx::env mdbx::txn::env ( ) const

inlinenoexcept

Returns the transaction's environment.

erase() [1/2]

bool mdbx::txn::erase ( map_handle  map, const slice &  key  )

inline

Removes all values for given key.

erase() [2/2]

bool mdbx::txn::erase ( map_handle  map, const slice &  key, const slice &  value  )

inline

Removes the particular multi-value entry of the key.

estimate() [1/2]

ptrdiff_t mdbx::txn::estimate ( map_handle  map, pair  from, pair  to  ) const

inline

estimate() [2/2]

ptrdiff_t mdbx::txn::estimate ( map_handle  map, slice  from, slice  to  ) const

inline

estimate_from_first()

ptrdiff_t mdbx::txn::estimate_from_first ( map_handle  map, slice  to  ) const

inline

estimate_to_last()

ptrdiff_t mdbx::txn::estimate_to_last ( map_handle  map, slice  from  ) const

inline

extract()

template<class ALLOCATOR , typename CAPACITY_POLICY >

buffer< ALLOCATOR, CAPACITY_POLICY > mdbx::txn::extract ( map_handle  map, const slice &  key, const typename buffer< ALLOCATOR, CAPACITY_POLICY >::allocator_type &  allocator = buffer<ALLOCATOR, CAPACITY_POLICY>::allocator_type()  )

inline

Removes and return a value of the key.

flags()

MDBX_txn_flags_t mdbx::txn::flags ( ) const

inline

Returns transaction's flags.

get() [1/4]

slice mdbx::txn::get ( map_handle  map, const slice &  key  ) const

inline

Get value by key from a key-value map (aka sub-database).

get() [2/4]

slice mdbx::txn::get ( map_handle  map, const slice &  key, const slice &  value_at_absence  ) const

inline

Get value by key from a key-value map (aka sub-database).

get() [3/4]

slice mdbx::txn::get ( map_handle  map, slice  key, size_t &  values_count  ) const

inline

Get first of multi-value and values count by key from a key-value multimap (aka sub-database).

get() [4/4]

slice mdbx::txn::get ( map_handle  map, slice  key, size_t &  values_count, const slice &  value_at_absence  ) const

inline

Get first of multi-value and values count by key from a key-value multimap (aka sub-database).

get_canary()

txn::canary mdbx::txn::get_canary ( ) const

inline

Returns fours integers markers (aka "canary") associated with the environment.

get_equal_or_great() [1/2]

pair_result mdbx::txn::get_equal_or_great ( map_handle  map, const slice &  key  ) const

inline

Get value for equal or great key from a database.

Returns

Bundle of key-value pair and boolean flag, which will be true if the exact key was found and false otherwise.

get_equal_or_great() [2/2]

pair_result mdbx::txn::get_equal_or_great ( map_handle  map, const slice &  key, const slice &  value_at_absence  ) const

inline

Get value for equal or great key from a database.

Returns

Bundle of key-value pair and boolean flag, which will be true if the exact key was found and false otherwise.

get_handle_info()

map_handle::info mdbx::txn::get_handle_info ( map_handle  map ) const

inline

Returns information about key-value map (aka sub-database) handle.

get_info()

txn::info mdbx::txn::get_info ( bool  scan_reader_lock_table = false ) const

inline

Returns information about the MDBX transaction.

get_map_stat()

txn::map_stat mdbx::txn::get_map_stat ( map_handle  map ) const

inline

Returns statistics for a sub-database.

get_tree_deepmask()

uint32_t mdbx::txn::get_tree_deepmask ( map_handle  map ) const

inline

Returns depth (bitmask) information of nested dupsort (multi-value) B+trees for given database.

id()

uint64_t mdbx::txn::id ( ) const

inline

Return the transaction's ID.

insert()

void mdbx::txn::insert ( map_handle  map, const slice &  key, slice  value  )

inline

insert_reserve()

slice mdbx::txn::insert_reserve ( map_handle  map, const slice &  key, size_t  value_length  )

inline

is_dirty()

bool mdbx::txn::is_dirty ( const void *  ptr ) const

inline

Checks whether the given data is on a dirty page.

is_readonly()

bool mdbx::txn::is_readonly ( ) const

inline

Checks whether the transaction is read-only.

is_readwrite()

bool mdbx::txn::is_readwrite ( ) const

inline

Checks whether the transaction is read-write.

open_cursor()

cursor_managed mdbx::txn::open_cursor ( map_handle  map )

inline

Opens cursor for specified key-value map handle.

open_map() [1/2]

mdbx::map_handle mdbx::txn::open_map ( const ::std::string &  name, const ::mdbx::key_mode  key_mode = ::mdbx::key_mode::usual, const ::mdbx::value_mode  value_mode = ::mdbx::value_mode::single  ) const

inline

Open existing key-value map.

open_map() [2/2]

mdbx::map_handle mdbx::txn::open_map ( const char *  name, const ::mdbx::key_mode  key_mode = ::mdbx::key_mode::usual, const ::mdbx::value_mode  value_mode = ::mdbx::value_mode::single  ) const

inline

Open existing key-value map.

operator bool()

MDBX_CXX14_CONSTEXPR mdbx::txn::operator bool ( ) const

noexcept

operator const MDBX_txn *()

MDBX_CXX14_CONSTEXPR mdbx::txn::operator const MDBX_txn *

(

)

const

operator MDBX_txn *()

MDBX_CXX14_CONSTEXPR mdbx::txn::operator MDBX_txn *

(

)

operator=()

txn & mdbx::txn::operator= ( txn &&  other )

inlinenoexcept

put() [1/2]

MDBX_error_t mdbx::txn::put ( map_handle  map, const slice &  key, slice *  value, MDBX_put_flags_t  flags  )

inlinenoexcept

put() [2/2]

void mdbx::txn::put ( map_handle  map, const slice &  key, slice  value, put_mode  mode  )

inline

put_canary()

txn & mdbx::txn::put_canary ( const canary &  canary )

inline

Set integers markers (aka "canary") associated with the environment.

put_multiple() [1/2]

template<typename VALUE >

void mdbx::txn::put_multiple ( map_handle  map, const slice &  key, const ::std::vector< VALUE > &  vector, put_mode  mode  )

inline

put_multiple() [2/2]

size_t mdbx::txn::put_multiple ( map_handle  map, const slice &  key, const size_t  value_length, const void *  values_array, size_t  values_count, put_mode  mode, bool  allow_partial = false  )

inline

renew_reading()

void mdbx::txn::renew_reading ( )

inline

Renew a read-only transaction.

replace() [1/2]

template<class ALLOCATOR , typename CAPACITY_POLICY >

buffer< ALLOCATOR, CAPACITY_POLICY > mdbx::txn::replace ( map_handle  map, const slice &  key, const slice &  new_value, const typename buffer< ALLOCATOR, CAPACITY_POLICY >::allocator_type &  allocator = buffer<ALLOCATOR, CAPACITY_POLICY>::allocator_type()  )

inline

Replaces and returns a value of the key with new one.

replace() [2/2]

void mdbx::txn::replace ( map_handle  map, const slice &  key, slice  old_value, const slice &  new_value  )

inline

Replaces the particular multi-value of the key with a new value.

replace_reserve()

template<class ALLOCATOR , typename CAPACITY_POLICY >

buffer< ALLOCATOR, CAPACITY_POLICY > mdbx::txn::replace_reserve ( map_handle  map, const slice &  key, slice &  new_value, const typename buffer< ALLOCATOR, CAPACITY_POLICY >::allocator_type &  allocator = buffer<ALLOCATOR, CAPACITY_POLICY>::allocator_type()  )

inline

reset_reading()

void mdbx::txn::reset_reading ( )

inline

Reset a read-only transaction.

sequence() [1/2]

uint64_t mdbx::txn::sequence ( map_handle  map ) const

inline

Reads sequence generator associated with a key-value map (aka sub-database).

sequence() [2/2]

uint64_t mdbx::txn::sequence ( map_handle  map, uint64_t  increment  )

inline

Reads and increment sequence generator associated with a key-value map (aka sub-database).

size_current()

size_t mdbx::txn::size_current ( ) const

inline

Returns current write transaction size (i.e.summary volume of dirty pages) in bytes.

size_max()

size_t mdbx::txn::size_max ( ) const

inline

Returns maximal write transaction size (i.e. limit for summary volume of dirty pages) in bytes.

start_nested()

txn_managed mdbx::txn::start_nested

(

)

Start nested write transaction.

try_insert()

value_result mdbx::txn::try_insert ( map_handle  map, const slice &  key, slice  value  )

inline

try_insert_reserve()

value_result mdbx::txn::try_insert_reserve ( map_handle  map, const slice &  key, size_t  value_length  )

inline

try_update()

bool mdbx::txn::try_update ( map_handle  map, const slice &  key, const slice &  value  )

inline

try_update_reserve()

value_result mdbx::txn::try_update_reserve ( map_handle  map, const slice &  key, size_t  value_length  )

inline

update()

void mdbx::txn::update ( map_handle  map, const slice &  key, const slice &  value  )

inline

update_reserve()

slice mdbx::txn::update_reserve ( map_handle  map, const slice &  key, size_t  value_length  )

inline

upsert()

void mdbx::txn::upsert ( map_handle  map, const slice &  key, const slice &  value  )

inline

upsert_reserve()

slice mdbx::txn::upsert_reserve ( map_handle  map, const slice &  key, size_t  value_length  )

inline

Friends And Related Function Documentation

cursor

friend class cursor

friend

operator!=

MDBX_CXX11_CONSTEXPR bool operator!= ( const txn &  a, const txn &  b  )

friend

operator==

MDBX_CXX11_CONSTEXPR bool operator== ( const txn &  a, const txn &  b  )

friend

Member Data Documentation

handle_

MDBX_txn* mdbx::txn::handle_ {nullptr}

protected

---

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

• mdbx.h++