LineairDB::Transaction Class Reference

We adopt "the page model" [Vossen95] as the model of transaction processing. For each transaction, the page model provides us four operations: two data operations and two termination operations. More...

#include <transaction.h>

Public Member Functions
TxStatus	GetCurrentStatus ()
	Get the current transaction status. For transactions such that GetCurrentStatus() returns TxStatus::Aborted, it is not guaranteed for subsequent read operations returns the correct values. More...
bool	IsRunning ()
bool	IsCommitted ()
bool	IsAborted ()
const std::pair< const std::byte *const, const size_t >	Read (const std::string_view key)
	If the database contains a data item for "key", returns a pair (a pointer of value, the size of value). More...
template<typename T >
const std::optional< T >	Read (const std::string_view key)
	Reads a value as user-defined type. T must be same as one on writing the value with Write(). More...
void	Write (const std::string_view key, const std::byte value[], const size_t size)
	Writes a value with a given key. More...
template<typename T >
void	Write (const std::string_view key, const T &value)
	Writes an user-defined value with a given key. More...
const std::optional< size_t >	Scan (const std::string_view begin, const std::string_view end, std::function< bool(std::string_view, const std::pair< const void *, const size_t >)> operation)
	Get all data items that match the range from the "begin" key to the "end" key in the lexical order. The term "get" here means that it is equivalent to the Read operation: this operation performs read operations for all the keys. More...
template<typename T >
const std::optional< size_t >	Scan (const std::string_view begin, const std::string_view end, std::function< bool(std::string_view, T)> operation)
	Scan operation with user-defined template type. More...
void	Abort ()
	Abort this transaction manually. More...

Friends
class	Database

Detailed Description

We adopt "the page model" [Vossen95] as the model of transaction processing. For each transaction, the page model provides us four operations: two data operations and two termination operations.

Data operations: read: read a data item. Scan consists of multiple read operations.

write: generate a new version of a data item. Termination operations: commit: commit this transaction. abort: abort this transaction.

Note that the commit operation is implicitly executed by the worker threads running in LineairDB, only when the transaction satisfies Strict Serializability and Recoverability. All methods are thread-safe.

See also

[Vossen95] https://doi.org/10.1007/BFb0015267

Member Function Documentation

Abort()

void LineairDB::Transaction::Abort

(

)

Abort this transaction manually.

GetCurrentStatus()

TxStatus LineairDB::Transaction::GetCurrentStatus

(

)

Get the current transaction status. For transactions such that GetCurrentStatus() returns TxStatus::Aborted, it is not guaranteed for subsequent read operations returns the correct values.

Returns

TxStatus

IsAborted()

bool LineairDB::Transaction::IsAborted ( )

inline

IsCommitted()

bool LineairDB::Transaction::IsCommitted ( )

inline

IsRunning()

bool LineairDB::Transaction::IsRunning ( )

inline

Read() [1/2]

const std::pair<const std::byte* const, const size_t> LineairDB::Transaction::Read

(

const std::string_view

key

)

If the database contains a data item for "key", returns a pair (a pointer of value, the size of value).

Parameters

key	An identifier for a data item

Returns

std::pair<void*, size_t> A pointer to the value of the requested data item and the size of the value. If there does not exists the data item of given key, it returns the pair (nullptr, 0).

Read() [2/2]

template<typename T >

const std::optional<T> LineairDB::Transaction::Read ( const std::string_view  key )

inline

Reads a value as user-defined type. T must be same as one on writing the value with Write().

Template Parameters

T	T must be Trivially Copyable and Constructable. This is because LineairDB is a Key-value storage but not a object storage.

Parameters

key

Returns

const std::optional<T>

Scan() [1/2]

const std::optional<size_t> LineairDB::Transaction::Scan	(	const std::string_view	begin,
		const std::string_view	end,
		std::function< bool(std::string_view, const std::pair< const void *, const size_t >)>	operation
	)

Get all data items that match the range from the "begin" key to the "end" key in the lexical order. The term "get" here means that it is equivalent to the Read operation: this operation performs read operations for all the keys.

Parameters

begin	An identifier of the starting point of the range search. This key is included in the range: if there exists a data item with this key, LineairDB returns the data item.
end	An identifier of the ending point of the range search. This key is included in the range: if there exists a data item with this key, LineairDB returns the data item.
operation	A bool function to be executed iteratively on data items matching the input range. The arguments of the function are key (std::string_view) and value (std::pair). Return value (boolean) forces LineairDB to cancel the scanning operation; when a function returns true at some key, this function will never be invoked with the next key.

Returns

std::optional<size_t> returns the total number of rows that match the inputted range, if succeed. Concurrent transactions may aborts this scan operation and returns std::nullopt_t.

Scan() [2/2]

template<typename T >

const std::optional<size_t> LineairDB::Transaction::Scan ( const std::string_view  begin, const std::string_view  end, std::function< bool(std::string_view, T)>  operation  )

inline

Scan operation with user-defined template type.

Template Parameters

T	T must be Trivially Copyable and Constructable. This is because LineairDB is a Key-value storage but not a object storage.

Parameters

begin
end
operation

Returns

std::optional<size_t>

Write() [1/2]

void LineairDB::Transaction::Write	(	const std::string_view	key,
		const std::byte	value[],
		const size_t	size
	)

Writes a value with a given key.

Parameters

key
value
size

Write() [2/2]

template<typename T >

void LineairDB::Transaction::Write ( const std::string_view  key, const T &  value  )

inline

Writes an user-defined value with a given key.

Template Parameters

T	T must be Trivially Copyable. This is because LineairDB is a Key-value storage but not a object storage.

Parameters

key
value

Friends And Related Function Documentation

Database

friend class Database

friend

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

• include/lineairdb/transaction.h