By default when DB.get or DBCursor.get, get_both, first, last, next or prev encounter a DB_NOTFOUND error they return None instead of raising DBNotFoundError. This behaviour emulates Python dictionaries and is convenient for looping.
You can use this method to toggle that behaviour for all of the aformentioned methods or extend it to also apply to the DBCursor.set, set_both, set_range, and set_recno methods. Supported values of flag:
The default of returning None makes it easy to do things like this without having to catch DBNotFoundError (KeyError):
data = mydb.get(key)
if data:
doSomething(data)
or this:
rec = cursor.first()
while rec:
print rec
rec = cursor.next()
Making the cursor set methods return None is useful in order to do this:
rec = mydb.set()
while rec:
key, val = rec
doSomething(key, val)
rec = mydb.next()
The downside to this it that it is inconsistent with the rest of the package and noticeably diverges from the Oracle Berkeley DB API. If you prefer to have the get and set methods raise an exception when a key is not found, use this method to tell them to do so.
Calling this method on a DBEnv object will set the default for all DB’s later created within that environment. Calling it on a DB object sets the behaviour for that DB only.
The previous setting is returned.
Files that are opened read-only in the memory pool (and that satisfy a few other criteria) are, by default, mapped into the process address space instead of being copied into the local cache. This can result in better-than-usual performance, as available virtual memory is normally much larger than the local cache, and page faults are faster than page copying on many systems. However, in the presence of limited virtual memory it can cause resource starvation, and in the presence of large databases, it can result in immense process sizes.
This method sets the maximum file size, in bytes, for a file to be mapped into the process address space. If no value is specified, it defaults to 10MB. More info...
Returns a dictionary of locking subsystem statistics with the following keys:
id Last allocated lock ID. cur_maxid The current maximum unused locker ID. nmodes Number of lock modes. maxlocks Maximum number of locks possible. maxlockers Maximum number of lockers possible. maxobjects Maximum number of objects possible. nlocks Number of current locks. maxnlocks Maximum number of locks at once. nlockers Number of current lockers. nobjects Number of current lock objects. maxnobjects Maximum number of lock objects at once. maxnlockers Maximum number of lockers at once. nrequests Total number of locks requested. nreleases Total number of locks released. nupgrade Total number of locks upgraded. ndowngrade Total number of locks downgraded. lock_wait The number of lock requests not immediately available due to conflicts, for which the thread of control waited. lock_nowait The number of lock requests not immediately available due to conflicts, for which the thread of control did not wait. ndeadlocks Number of deadlocks. locktimeout Lock timeout value. nlocktimeouts The number of lock requests that have timed out. txntimeout Transaction timeout value. ntxntimeouts The number of transactions that have timed out. This value is also a component of ndeadlocks, the total number of deadlocks detected. objs_wait The number of requests to allocate or deallocate an object for which the thread of control waited. objs_nowait The number of requests to allocate or deallocate an object for which the thread of control did not wait. lockers_wait The number of requests to allocate or deallocate a locker for which the thread of control waited. lockers_nowait The number of requests to allocate or deallocate a locker for which the thread of control did not wait. locks_wait The number of requests to allocate or deallocate a lock structure for which the thread of control waited. locks_nowait The number of requests to allocate or deallocate a lock structure for which the thread of control did not wait. hash_len Maximum length of a lock hash bucket. regsize Size of the region. region_wait Number of times a thread of control was forced to wait before obtaining the region lock. region_nowait Number of times a thread of control was able to obtain the region lock without waiting.
Return a dictionary of transaction statistics with the following keys:
last_ckp The LSN of the last checkpoint. time_ckp Time the last completed checkpoint finished (as the number of seconds since the Epoch, returned by the IEEE/ANSI Std 1003.1 POSIX time interface). last_txnid Last transaction ID allocated. maxtxns Max number of active transactions possible. nactive Number of transactions currently active. maxnactive Max number of active transactions at once. nsnapshot The number of transactions on the snapshot list. These are transactions which modified a database opened with DB_MULTIVERSION, and which have committed or aborted, but the copies of pages they created are still in the cache. maxnsnapshot The maximum number of transactions on the snapshot list at any one time. nbegins Number of transactions that have begun. naborts Number of transactions that have aborted. ncommits Number of transactions that have committed. nrestores Number of transactions that have been restored. regsize Size of the region. region_wait Number of times that a thread of control was forced to wait before obtaining the region lock. region_nowait Number of times that a thread of control was able to obtain the region lock without waiting.
Returns a dictionary of logging subsystem statistics with the following keys:
magic The magic number that identifies a file as a log file. version The version of the log file type. mode The mode of any created log files. lg_bsize The in-memory log record cache size. lg_size The log file size. record The number of records written to this log. w_mbytes The number of megabytes written to this log. w_bytes The number of bytes over and above w_mbytes written to this log. wc_mbytes The number of megabytes written to this log since the last checkpoint. wc_bytes The number of bytes over and above wc_mbytes written to this log since the last checkpoint. wcount The number of times the log has been written to disk. wcount_fill The number of times the log has been written to disk because the in-memory log record cache filled up. rcount The number of times the log has been read from disk. scount The number of times the log has been flushed to disk. cur_file The current log file number. cur_offset The byte offset in the current log file. disk_file The log file number of the last record known to be on disk. disk_offset The byte offset of the last record known to be on disk. maxcommitperflush The maximum number of commits contained in a single log flush. mincommitperflush The minimum number of commits contained in a single log flush that contained a commit. regsize The size of the log region, in bytes. region_wait The number of times that a thread of control was forced to wait before obtaining the log region mutex. region_nowait The number of times that a thread of control was able to obtain the log region mutex without waiting.
Returns a list of tuples (GID, TXN) of transactions prepared but still unresolved. This is used while doing environment recovery in an application using distributed transactions.
This method must be called only from a single thread at a time. It should be called after DBEnv recovery. More info...
This module automates many of the tasks needed to provide replication abilities in a Berkeley DB system. The module is fairly limited, but enough in many cases. Users more demanding must use the full Base Replication API.
This module requires POSIX support, so you must compile Berkeley DB with it if you want to be able to use the Replication Manager.
Adds a new replication site to the replication manager’s list of known sites. It is not necessary for all sites in a replication group to know about all other sites in the group.
Method returns the environment ID assigned to the remote site. More info...
Returns a dictionary with the status of the sites currently known by the replication manager.
The keys are the Environment ID assigned by the replication manager. This is the same value that is passed to the application’s event notification function for the DB_EVENT_REP_NEWMASTER event.
The values are tuples containing the hostname, the TCP/IP port number and the link status.
Returns a dictionary with the replication manager statistics. Keys are:
| perm_failed | The number of times a message critical for maintaining database integrity (for example, a transaction commit), originating at this site, did not receive sufficient acknowledgement from clients, according to the configured acknowledgement policy and acknowledgement timeout. |
| msgs_queued | The number of outgoing messages which could not be transmitted immediately, due to a full network buffer, and had to be queued for later delivery. |
| msgs_dropped | The number of outgoing messages that were completely dropped, because the outgoing message queue was full. (Berkeley DB replication is tolerant of dropped messages, and will automatically request retransmission of any missing messages as needed.) |
| connection_drop | The number of times an existing TCP/IP connection failed. |
| connect_fail | The number of times an attempt to open a new TCP/IP connection failed. |
Processes an incoming replication message sent by a member of the replication group to the local database environment.
Returns a two element tuple.
Configures the database environment as a client or master in a group of replicated database environments.
The DB_ENV->rep_start method is not called by most replication applications. It should only be called by applications implementing their own network transport layer, explicitly holding replication group elections and handling replication messages outside of the replication manager framework.