BDB::Env
Berkeley DB environment is an encapsulation of one or more databases, log files and shared information about the database environment such as shared memory buffer cache pages.
The simplest way to administer a Berkeley DB application environment is to create a single home directory that stores the files for the applications that will share the environment. The environment home directory must be created before any Berkeley DB applications are run. Berkeley DB itself never creates the environment home directory. The environment can then be identified by the name of that directory.
Class Methods
open(home, flags = 0, mode = 0, options = {})create(home, flags = 0, mode = 0, options = {})new(home, flags = 0, mode = 0, options = {})-
open the Berkeley DB environment
- home
-
If this argument is non-NULL, its value may be used as the database home, and files named relative to its path.
- mode
-
mode for creation (see chmod(2))
- flags
-
must be set to 0 or by OR'ing with
- BDB::INIT_CDB Initialize locking.
- BDB::INIT_LOCK Initialize the locking subsystem.
- BDB::INIT_LOG Initialize the logging subsystem.
- BDB::INIT_MPOOL Initialize the shared memory buffer pool subsystem.
- BDB::INIT_TXN Initialize the transaction subsystem.
- BDB::INIT_TRANSACTION
-
Equivalent to DB_INIT_LOCK | DB_INIT_MPOOL | DB_INIT_TXN | DB_INIT_LOG
- BDB::RECOVER
-
Run normal recovery on this environment before opening it for normal use. If this flag is set, the DB_CREATE flag must also be set since the regions will be removed and recreated.
- BDB::RECOVER_FATAL
-
Run catastrophic recovery on this environment before opening it for normal use. If this flag is set, the DB_CREATE flag must also be set since the regions will be removed and recreated.
- BDB::USE_ENVIRON
-
The Berkeley DB process' environment may be permitted to specify information to be used when naming files
- BDB::USE_ENVIRON_ROOT
-
The Berkeley DB process' environment may be permitted to specify information to be used when naming files; if the DB_USE_ENVIRON_ROOT flag is set, environment information will be used for file naming only for users with appropriate permissions
- BDB::CREATE
-
Cause Berkeley DB subsystems to create any underlying files, as necessary.
- BDB::LOCKDOWN
-
Lock shared Berkeley DB environment files and memory mapped databases into memory.
- BDB::NOMMAP
-
Always copy read-only database files in this environment into the local cache instead of potentially mapping them into process memory
- BDB::PRIVATE
-
Specify that the environment will only be accessed by a single process
- BDB::SYSTEM_MEM
-
Allocate memory from system shared memory instead of from memory backed by the filesystem.
- BDB::TXN_NOSYNC
-
Do not synchronously flush the log on transaction commit or prepare. This means that transactions exhibit the ACI (atomicity, consistency and isolation) properties, but not D (durability), i.e., database integrity will be maintained but it is possible that some number of the most recently committed transactions may be undone during recovery instead of being redone.
- BDB::CDB_ALLDB
-
For Berkeley DB Concurrent Data Store applications, perform locking on an environment-wide basis rather than per-database.
- options
-
Hash, Possible options are (see the documentation of Berkeley DB for more informations)
- set_app_dispatch : configure application recovery interface (DB >= 4.1)
- set_cachesize : set the database cache size
- set_data_dir : set the environment data directory (DB >= 3)
- set_encrypt : set the environment cryptographic key (DB >= 4.1)
- set_feedback : set feedback callback (DB >= 3)
- set_flags : environment configuration (DB >= 3.2)
- set_lg_bsize : set log buffer size (DB >= 3)
- set_lg_dir : set the environment logging directory (DB >= 3)
- set_lg_max : set log file size
- set_lg_regionmax : set logging region size (DB >= 3)
- set_lk_conflicts : set lock conflicts matrix (DB >= 3)
- set_lk_detect : set automatic deadlock detection
- set_lk_max_lockers : set maximum number of lockers
- set_lk_max_locks : set maximum number of locks
- set_lk_max_objects : set maximum number of lock objects
- set_rep_transport : configure replication transport (DB >= 4)
- set_rep_limit : limit data sent in response to a single message (DB >= 4.1)
- set_rpc_server : establish an RPC server connection (DB >= 3.1)
- set_tas_spins : set the number of test-and-set spins (DB >= 3)
- set_tmp_dir : set the environment temporary file directory (DB >= 3)
- set_timeout : set lock and transaction timeout (DB >= 4)
- set_tx_max : set maximum number of transactions (DB >= 3)
- set_tx_timestamp : set recovery timestamp (DB >= 3.1)
- set_verbose : set verbose messages
- set_verb_chkpoint :display checkpoint location information when searching the log for checkpoints. (DB >= 3)
- set_verb_deadlock : display additional information when doing deadlock detection. (DB >= 3)
- set_verb_recovery : display additional information when performing recovery. (DB >= 3)
- set_verb_replication : display additional information when processing replication messages. (DB >= 4)
- set_verb_waitsfor : display the waits-for table when doing deadlock detection. (DB >= 3)
Proc given to set_feedback, set_app_dispatch and set_rep_transport can be also specified as a method (replace the prefix set_ with bdb_)
For bdb_rep_transport the constant ENVID must be defined
The constant BDB_ENCRYPT can be used to replace set_encrypt
remove()unlink()-
remove the environnement
Methods
close()-
close the environnement
dbremove(file, database = nil, flags = 0)-
only with BDB::VERSION_MAJOR == 4 && BDB::VERSION_MINOR >= 1
remove the database specified by file and database. If no database is nil, the underlying file represented by file is removed, incidentally removing all databases that it contained.
The flags value must be set to 0 or BDB::AUTO_COMMIT
dbrename(file, database, newname, flags = 0)-
only with BDB::VERSION_MAJOR == 4 && BDB::VERSION_MINOR >= 1
rename the database specified by file and database to newname. If database is nil, the underlying file represented by file is renamed, incidentally renaming all databases that it contained.
The flags value must be set to 0 or BDB::AUTO_COMMIT
feedback=(proc)-
monitor the progress of some operations
home()-
return the name of the directory
lock()lock_id()-
Acquire a locker ID
lock_detect(type, flags = 0)-
The lock_detect function runs one iteration of the deadlock detector. The deadlock detector traverses the lock table, and for each deadlock it finds, marks one of the participating transactions for abort.
type can have one the value BDB::LOCK_OLDEST, BDB::LOCK_RANDOM or BDB::LOCK_YOUNGUEST
flags can have the value BDB::LOCK_CONFLICT, in this case the deadlock detector is run only if a lock conflict has occurred since the last time that the deadlock detector was run.
return the number of transactions aborted by the lock_detect function if BDB::VERSION_MAJOR >= 3 or zero
lock_stat()-
Return lock subsystem statistics
log_archive(flags = 0)-
The log_archive function return an array of log or database file names.
flags value must be set to 0 or the value BDB::ARCH_DATA, BDB::ARCH_ABS, BDB::ARCH_LOG
log_checkpoint(string)-
same as log_put(string, BDB::CHECKPOINT)
log_curlsn(string)-
same as log_put(string, BDB::CURLSN)
log_each { |string, lsn| ... }-
Implement an iterator inside of the log
log_flush(string = nil)-
same as log_put(string, BDB::FLUSH)
Without argument, garantee that all records are written to the disk
log_get(flag)-
The log_get return an array [String, BDB::Lsn] according to the flag value.
flag can has the value BDB::CHECKPOINT, BDB::FIRST, BDB::LAST, BDB::NEXT, BDB::PREV, BDB::CURRENT
log_put(string, flag = 0)-
The log_put function appends records to the log. It return an object BDB::Lsn
flag can have the value BDB::CHECKPOINT, BDB::CURLSN, BDB::FLUSH
log_reverse_each { |string, lsn| ... }-
Implement an iterator inside of the log
log_stat-
return log statistics
open_db(type, name = nil, subname = nil, flags = 0, mode = 0)-
open the database in the current environment. type must be one of the constant BDB::BTREE, BDB::HASH, BDB::RECNO, BDB::QUEUE. See open for other arguments
recover { |txn, id| ... }-
only with BDB::VERSION_MAJOR == 3 && BDB::VERSION_MINOR >= 3
iterate over all prepared transactions. The transaction txn must be made a call to #abort, #commit, #discard
id is the global transaction ID for the transaction
set_flags(flags, onoff = true)-
only with BDB::VERSION_MAJOR == 3 && BDB::VERSION_MINOR >= 2
flags can have the value BDB::CDB_ALLDB, BDB::NOMMAP BDB::TXN_NOSYNC
if onoff is false, the specified flags are cleared
begin(flags = 0)txn_begin(flags = 0)begin(flags = 0, db, ...) { |txn, db, ...| ...}-
begin a transaction (the transaction manager must be enabled). flags can have the value DBD::TXN_COMMIT, in this case the transaction will be commited at end.
checkpoint(kbyte, min = 0)txn_checkpoint(kbyte, min = 0)-
The txn_checkpoint function flushes the underlying memory pool, writes a checkpoint record to the log and then flushes the log.
If either kbyte or min is non-zero, the checkpoint is only done if more than min minutes have passed since the last checkpoint, or if more than kbyte kilobytes of log data have been written since the last checkpoint.
stat()txn_stat()-
Return transaction subsystem statistics
elect(sites, priority, timeout)rep_elect(sites, priority, timeout)-
Only for DB >= 4
Holds an election for the master of a replication group, returning the new master's ID
Raise BDB::RepUnavail if the timeout expires
process_message(control, rec, envid)rep_process_message(control, rec, envid)-
Only for DB >= 4
Processes an incoming replication message sent by a member of the replication group to the local database environment
start(cdata, flags)rep_start(cdata, flags)-
Only for DB >= 4
cdata is an identifier flags must be one of BDB::REP_CLIENT, BDB::REP_MASTER or BDB::REP_LOGSONLY