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_rep_nsites : configure replication group site count (DB >= 4.5)
set_rep_priority : configure replication site priority (DB >= 4.5)
set_rep_config : configure the replication subsystem (DB >= 4.5)
set_rep_timeout : configure replication timeouts (DB >= 4.5)
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

repmgr_add_remote(host, port, flag = 0)

Only for DB >= 4.5

Adds a new replication site to the replication manager’s list of known sites.

Return the environment ID assigned to the remote site

repmgr_ack_policy=(policy)
repmgr_set_ack_policy(policy)

Only for DB >= 4.5

Specifies how master and client sites will handle acknowledgment of replication messages which are necessary for “permanent” records.

policy must be set to one of the following values BDB::REPMGR_ACKS_ALL, BDB::REPMGR_ACKS_ALL_PEERS, BDB::REPMGR_ACKS_NONE, BDB::REPMGR_ACKS_ONE, BDB::REPMGR_ACKS_ONE_PEER, BDB::REPMGR_ACKS_QUORUM

repmgr_ack_policy
repmgr_get_ack_policy

Only for DB >= 4.5

Returns the replication manager’s client acknowledgment policy.

repmgr_site_list

Only for DB >= 4.5

Returns an array with the status of the sites currently known by the replication manager.

repmgr_set_local_site(host, port, flag = 0)

Only for DB >= 4.5

Specifies the host identification string and port number for the local system.

repmgr_start(count, flag)

Only for DB >= 4.5

Starts the replication manager.

rep_config[]=(which, onoff)

Only for DB >= 4.5

Configures the Berkeley DB replication subsystem.

which can have the value BDB::REP_CONF_BULK, BDB::REP_CONF_DELAYCLIENT, BDB::REP_CONF_NOAUTOINIT, BDB::REP_CONF_NOWAIT

onoff can have the value true or false

rep_config?[](which)

Only for DB >= 4.5

Returns true if the specified which parameter is currently set or not.

rep_nsites=(sites)

Only for DB >= 4.5

Specifies the total number of sites in a replication group.

rep_nsites

Only for DB >= 4.5

Returns the total number of sites in a replication group.

rep_priority=(priority)

Only for DB >= 4.5

Specifies the priority in the replication group elections.

rep_priority

Only for DB >= 4.5

Returns the database environment priority.

rep_timeout[]=(which, timeout)

Only for DB >= 4.5

Specifies the timeout in the replication group elections.

which can have the value BDB::REP_ACK_TIMEOUT, BDB::REP_ELECTION_TIMEOUT, BDB::REP_ELECTION_RETRY, BDB::REP_CONNECTION_RETRY

rep_timeout[](which)

Only for DB >= 4.5

Returns the database environment timeout for which

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

lsn_reset(file, flags = 0)

Only for DB >= 4.4

Reset database file LSN

The Env#lsn_reset method allows database files to be moved from one transactional database environment to another.

+file+The name of the physical file in which the LSNs are to be cleared. flags must be set to 0 or BDB::ENCRYPT

fileid_reset(file, flags = 0)

Only for DB >= 4.4

Reset database file ID

The Env#fileid_reset method allows database files to be copied, and then the copy used in the same database environment as the original.

+file+The name of the physical file in which new file IDs are to be created. flags must be set to 0 or BDB::ENCRYPT

msgcall=(call_proc)

Only for DB >= 4.4

There are interfaces in the Berkeley DB library which either directly output informational messages or statistical information : Env#msgcall is used to set callback which will called by BDB

The value given must be nil to unconfigure the callback, or and object which respond to #call : it will called with a String as argument

thread_id=(call_proc)

Only for DB >= 4.4

Declare a proc object which returns a unique identifier pair for the current thread of control.

The proc must return a pair

  • pid: process ID of the current thread

  • tid: thread ID of the current thread

thread_id_string=(call_proc)

Only for DB >= 4.4

Declare a proc that formats a process ID and thread ID identifier pair for display.

The proc will be called with 2 arguments and must return a String

is_alive=(call_proc)

Only for DB >= 4.4

Declare a proc that returns if a thread of control (either a true thread or a process) is still running.

The proc will be called with 2 arguments (pid, tid)

failcheck(flag = 0)

Only for DB >= 4.4

The method checks for threads of control (either a true thread or a process) that have exited while manipulating Berkeley DB library data structures

flag is actually unused and must be set to 0