#include <db_cxx.h>
class DbTxn {
public:
DB_TXN *DbTxn::get_DB_TXN();
const DB_TXN *DbTxn::get_const_DB_TXN() const;
static DbTxn *DbTxn::get_DbTxn(DB_TXN *txn);
static const DbTxn *DbTxn::get_const_DbTxn(const DB_TXN *txn);
...
};
The DbTxn object is the handle for a transaction. Methods of
the DbTxn handle are used to configure, abort and commit the
transaction. DbTxn handles are provided to
Db methods in order
to transactionally protect those database operations.
DbTxn handles are not free-threaded; transactions handles
may be used by multiple threads, but only serially, that is, the application must
serialize access to the DbTxn handle. Once the
DbTxn::abort()
or
DbTxn::commit()
methods are called, the handle
may not be accessed again, regardless of the method's return. In addition, parent
transactions may not issue any Berkeley DB operations while they have active child
transactions (child transactions that have not yet been committed or aborted) except for
DbEnv::txn_begin()
,
DbTxn::abort()
and
DbTxn::commit()
.
Each DbTxn object has an associated
DB_TXN struct, which is used by the underlying
implementation of Berkeley DB and its
C++ language
API. The DbTxn::get_DB_TXN() method
returns a pointer to this struct. Given a const DbTxn object,
txnMget_const_DB_TXN()
returns a const pointer to the same struct.
Given a DB_TXN struct, the DbTxn::get_DbTxn()
method returns the corresponding DbTxn object, if there is
one. If the DB_TXN object was not associated with a
DbTxn (that is, it was not returned from a call to
DbTxn::get_DB_TXN()), then the result of
DbTxn::get_DbTxn is undefined. Given a const
DB_TXN struct, DbTxn::get_const_DbTxn()
returns the associated const DbTxn object, if there is one.
These methods may be useful for Berkeley DB applications including both C and C++ language software. It should not be necessary to use these calls in a purely C++ application.