#include <db_cxx.h> int Db::upgrade(const char *file, u_int32_t flags);
The Db::upgrade() method upgrades all of the databases included in
the file file, if necessary. If no
upgrade is necessary, Db::upgrade() always returns success.
Database upgrades are done in place and are destructive. For example, if pages need to be allocated and no disk space is available, the database may be left corrupted. Backups should be made before databases are upgraded. See Upgrading databases for more information.
Unlike all other database operations, Db::upgrade() may only be done
on a system with the same byte-order as the database.
The Db::upgrade() method is non-atomic
when used on a sliced database. If the operation fails, it is
possible for the underlying database files to be in an
inconsistent state.
The Db::upgrade()
method either returns a non-zero error value or throws an
exception that encapsulates a non-zero error value on
failure, and returns 0 on success.
The flags parameter must be set to 0 or the following value:
This flag is only meaningful when upgrading databases from releases before the Berkeley DB 3.1 release.
As part of the upgrade from the Berkeley DB 3.0 release to the 3.1
release, the on-disk format of duplicate data items changed. To
correctly upgrade the format requires applications to specify whether
duplicate data items in the database are sorted or not. Specifying
the DB_DUPSORT flag informs Db::upgrade() that the duplicates are
sorted; otherwise they are assumed to be unsorted. Incorrectly
specifying the value of this flag may lead to database corruption.
Further, because the Db::upgrade() method upgrades a physical file
(including all the databases it contains), it is not possible to use
Db::upgrade() to upgrade files in which some of the databases it
includes have sorted duplicate data items, and some of the databases
it includes have unsorted duplicate data items. If the file does not
have more than a single database, if the databases do not support
duplicate data items, or if all of the databases that support
duplicate data items support the same style of duplicates (either
sorted or unsorted), Db::upgrade() will work correctly as long as the
DB_DUPSORT flag is correctly specified. Otherwise, the file cannot be
upgraded using Db::upgrade;() it must be upgraded manually by dumping
and reloading the databases.
If the database was opened within a database environment, the
environment variable DB_HOME may be used as the path of the
database environment home.
Db::upgrade() is affected by any database directory specified using the
DbEnv::add_data_dir()
method, or by setting the "add_data_dir" string
in the environment's DB_CONFIG file.
The Db::upgrade()
method may fail and throw a DbException
exception, encapsulating one of the following non-zero errors, or return one
of the following non-zero errors: