API¶
Classes, methods and stuff.
Connections¶
-
class
momoko.
Pool
(dsn, connection_factory=None, cursor_factory=None, size=1, max_size=None, ioloop=None, raise_connect_errors=True, reconnect_interval=500, setsession=(), auto_shrink=False, shrink_delay=datetime.timedelta(0, 120), shrink_period=datetime.timedelta(0, 120))¶ Asynchronous connection pool object. All its methods are asynchronous unless stated otherwide in method description.
Parameters: - dsn (string) –
A Data Source Name string containing one of the following values:
- dbname - the database name
- user - user name used to authenticate
- password - password used to authenticate
- host - database host address (defaults to UNIX socket if not provided)
- port - connection port number (defaults to 5432 if not provided)
Or any other parameter supported by PostgreSQL. See the PostgreSQL documentation for a complete list of supported parameters.
- connection_factory – The
connection_factory
argument can be used to create non-standard connections. The class returned should be a subclass of psycopg2.extensions.connection. See Connection and cursor factories for details. Defaults toNone
. - cursor_factory – The
cursor_factory
argument can be used to return non-standart cursor class The class returned should be a subclass of psycopg2.extensions.cursor. See Connection and cursor factories for details. Defaults toNone
. - size (int) – Minimal number of connections to maintain.
size
connections will be opened and maintained after callingmomoko.Pool.connect()
. - max_size (int or None) – if not
None
, the pool size will dynamically grow on demand up tomax_size
open connections. By default the connections will still be maintained even if when the pool load decreases. See alsoauto_shrink
parameter. - ioloop – Tornado IOloop instance to use. Defaults to Tornado’s
IOLoop.instance()
. - raise_connect_errors (bool) – Whether to raise
momoko.PartiallyConnectedError()
when failing to connect to database duringmomoko.Pool.connect()
. - reconnect_interval (int) – If database server becomes unavailable, the pool will try to reestablish
the connection. The attempt frequency is
reconnect_interval
milliseconds. - setsession (list) – List of intial sql commands to be executed once connection is established. If any of the commands fails, the connection will be closed. NOTE: The commands will be executed as one transaction block.
- auto_shrink (bool) – Garbage-collect idle connections. Only applicable if
max_size
was specified. Nevertheless, the pool will mainatain at leastsize
connections. - shrink_delay (
datetime.timedelta()
) – A connection is declared idle if it was not used forshrink_delay
time period. Idle connections will be garbage-collected ifauto_shrink
is set toTrue
. - shrink_period (
datetime.timedelta()
) – Ifauto_shink
is enabled, this parameter defines how the pool will check for idle connections.
-
exception
DatabaseNotAvailable
¶ Raised when Pool can not connect to database server
-
Pool.
callproc
(*args, **kwargs)¶ Call a stored database procedure with the given name.
See
momoko.Connection.callproc()
for documentation about the parameters.
-
Pool.
close
()¶ Close the connection pool.
NOTE: This is a synchronous method.
-
Pool.
connect
()¶ Returns future that resolves to this Pool object.
If some connection failed to connect and self.raise_connect_errors is true, raises
momoko.PartiallyConnectedError()
.
-
Pool.
execute
(*args, **kwargs)¶ Prepare and execute a database operation (query or command).
See
momoko.Connection.execute()
for documentation about the parameters.
-
Pool.
getconn
(ping=True)¶ Acquire connection from the pool.
You can then use this connection for subsequent queries. Just use
connection.execute
instead ofPool.execute
.Make sure to return connection to the pool by calling
momoko.Pool.putconn()
, otherwise the connection will remain forever busy and you’ll starve your pool.Returns a future that resolves to the acquired connection object.
Parameters: ping (boolean) – Whether to ping the connection before returning it by executing momoko.Connection.ping()
.
-
Pool.
manage
(*args, **kwds)¶ Context manager that automatically returns connection to the pool. You can use it instead of
momoko.Pool.putconn()
:connection = yield self.db.getconn() with self.db.manage(connection): cursor = yield connection.execute("BEGIN") ...
-
Pool.
mogrify
(*args, **kwargs)¶ Return a query string after arguments binding.
NOTE: This is NOT a synchronous method (contary to momoko.Connection.mogrify) - it asynchronously waits for available connection. For performance reasons, its better to create dedicated
momoko.Connection()
object and use it directly for mogrification, this operation does not imply any real operation on the database server.See
momoko.Connection.mogrify()
for documentation about the parameters.
-
Pool.
ping
()¶ Make sure this connection is alive by executing SELECT 1 statement - i.e. roundtrip to the database.
See
momoko.Connection.ping()
for documentation about the parameters.
-
Pool.
putconn
(connection)¶ Return busy connection back to the pool.
NOTE: This is a synchronous method.
Parameters: connection (Connection) – Connection object previously returned by momoko.Pool.getconn()
.
-
Pool.
register_hstore
(*args, **kwargs)¶ Register adapter and typecaster for
dict-hstore
conversions.See
momoko.Connection.register_hstore()
for documentation about the parameters. This method has noglobally
parameter, because it already registers hstore to all the connections in the pool.
-
Pool.
register_json
(*args, **kwargs)¶ Create and register typecasters converting
json
type to Python objects.See
momoko.Connection.register_json()
for documentation about the parameters. This method has noglobally
parameter, because it already registers json to all the connections in the pool.
-
Pool.
transaction
(*args, **kwargs)¶ Run a sequence of SQL queries in a database transaction.
See
momoko.Connection.transaction()
for documentation about the parameters.
- dsn (string) –
-
class
momoko.
Connection
(dsn, connection_factory=None, cursor_factory=None, ioloop=None, setsession=())¶ Asynchronous connection object. All its methods are asynchronous unless stated otherwide in method description.
Parameters: - dsn (string) –
A Data Source Name string containing one of the following values:
- dbname - the database name
- user - user name used to authenticate
- password - password used to authenticate
- host - database host address (defaults to UNIX socket if not provided)
- port - connection port number (defaults to 5432 if not provided)
Or any other parameter supported by PostgreSQL. See the PostgreSQL documentation for a complete list of supported parameters.
- connection_factory – The
connection_factory
argument can be used to create non-standard connections. The class returned should be a subclass of psycopg2.extensions.connection. See Connection and cursor factories for details. Defaults toNone
. - cursor_factory – The
cursor_factory
argument can be used to return non-standart cursor class The class returned should be a subclass of psycopg2.extensions.cursor. See Connection and cursor factories for details. Defaults toNone
. - setsession (list) – List of intial sql commands to be executed once connection is established. If any of the commands fails, the connection will be closed. NOTE: The commands will be executed as one transaction block.
-
callproc
(procname, parameters=(), cursor_factory=None)¶ Call a stored database procedure with the given name.
The sequence of parameters must contain one entry for each argument that the procedure expects. The result of the call is returned as modified copy of the input sequence. Input parameters are left untouched, output and input/output parameters replaced with possibly new values.
The procedure may also provide a result set as output. This must then be made available through the standard fetch*() methods.
Parameters: - procname (string) – The name of the database procedure.
- parameters (tuple/list) – A list or tuple with query parameters. See Passing parameters to SQL queries for more information. Defaults to an empty tuple.
- cursor_factory – The
cursor_factory
argument can be used to create non-standard cursors. The class returned must be a subclass of psycopg2.extensions.cursor. See Connection and cursor factories for details. Defaults toNone
.
Returns future that resolves to cursor object containing result.
-
close
()¶ Closes the connection.
NOTE: This is a synchronous method.
-
closed
¶ Indicates whether the connection is closed or not.
-
connect
()¶ Initiate asynchronous connect. Returns future that resolves to this connection object.
-
execute
(operation, parameters=(), cursor_factory=None)¶ Prepare and execute a database operation (query or command).
Parameters: - operation (string) – An SQL query.
- parameters (tuple/list/dict) – A list, tuple or dict with query parameters. See Passing parameters to SQL queries for more information. Defaults to an empty tuple.
- cursor_factory – The
cursor_factory
argument can be used to create non-standard cursors. The class returned must be a subclass of psycopg2.extensions.cursor. See Connection and cursor factories for details. Defaults toNone
.
Returns future that resolves to cursor object containing result.
-
mogrify
(operation, parameters=())¶ Return a query string after arguments binding.
The string returned is exactly the one that would be sent to the database running the execute() method or similar.
NOTE: This is a synchronous method.
Parameters: - operation (string) – An SQL query.
- parameters (tuple/list) – A list or tuple with query parameters. See Passing parameters to SQL queries for more information. Defaults to an empty tuple.
-
ping
()¶ Make sure this connection is alive by executing SELECT 1 statement - i.e. roundtrip to the database.
Returns future. If it resolves sucessfully - the connection is alive (or dead otherwise).
-
register_hstore
(globally=False, unicode=False)¶ Register adapter and typecaster for
dict-hstore
conversions.More information on the hstore datatype can be found on the Psycopg2 documentation.
Parameters: - globally (boolean) – Register the adapter globally, not only on this connection.
- unicode (boolean) – If
True
, keys and values returned from the database will beunicode
instead ofstr
. The option is not available on Python 3.
Returns future that resolves to
None
.
-
register_json
(globally=False, loads=None)¶ Create and register typecasters converting
json
type to Python objects.More information on the json datatype can be found on the Psycopg2 documentation.
Parameters: - globally (boolean) – Register the adapter globally, not only on this connection.
- loads (function) – The function used to parse the data into a Python object. If
None
usejson.loads()
, wherejson
is the module chosen according to the Python version. See psycopg2.extra docs.
Returns future that resolves to
None
.
-
transaction
(statements, cursor_factory=None, auto_rollback=True)¶ Run a sequence of SQL queries in a database transaction.
Parameters: - statements (tuple/list) –
List or tuple containing SQL queries with or without parameters. An item can be a string (SQL query without parameters) or a tuple/list with two items, an SQL query and a tuple/list/dict with parameters.
See Passing parameters to SQL queries for more information.
- cursor_factory – The
cursor_factory
argument can be used to create non-standard cursors. The class returned must be a subclass of psycopg2.extensions.cursor. See Connection and cursor factories for details. Defaults toNone
. - auto_rollback (bool) – If one of the transaction statements fails, try to automatically execute ROLLBACK to abort the transaction. If ROLLBACK fails, it would not be raised, but only logged.
Returns future that resolves to
list
of cursors. Each cursor contains the result of the corresponding transaction statement.- statements (tuple/list) –
- dsn (string) –
-
momoko.
connect
(*args, **kwargs)¶ Connection factory. See
momoko.Connection()
for documentation about the parameters.Returns future that resolves to
momoko.Connection()
object or raises exception.
Exceptions¶
-
class
momoko.
PoolError
¶ Raised when something goes wrong in the connection pool.
-
class
momoko.
PartiallyConnectedError
¶ Raised when
momoko.Pool()
can not initialize all of the requested connections.