Set_session() can’t be used but it is still possible to invoke the Manually control transactions using execute() to send databaseĬommands such as BEGIN, COMMIT and ROLLBACK. To use methods commit() and rollback(): you can Transaction is not implicitly started at the first query and is not possible There are several limitations in using asynchronous connections: theĬonnection is always in autocommit mode and it is not Two cursors can’t execute concurrent queries on the same asynchronous When an asynchronous query is being executed, connection.isexecuting() returns execute ( "SELECT pg_sleep(5) SELECT 42 " ) > wait ( acurs. Some data to read on the connection, thereby using no CPU unless there is A better strategy is to use some I/O completionįunction such as select() to sleep until awakened by the kernel when there is Poll() method can be used to check for new messages withoutĪ simple application could poll the connection from time to time to check if Interested in receiving notifications but not in performing any query, the Notifications are received after every query execution. Mode if you wish to receive or send notifications in a timely manner. Notifications canīe sent from Python code simply executing a NOTIFY command in anīecause of the way sessions interact with notifications (see NOTIFYĭocumentation), you should keep the connection in autocommit Notifications are instances of the Notify object madeĪvailable upon reception in the connection.notifies list. Refer to the PostgreSQL documentation for examples about how to use this form of Psycopg allows asynchronous interaction with other database sessions using theįacilities offered by PostgreSQL commands LISTEN and NOTIFY. New_array_type() to create a typecaster converting a y ) 10.2 20.3Ī typecaster created by new_type() can be also used with fetchone () > print ( type ( point ), point. Wrapper, whose getquoted() result is simply the str()ing conversion ofĮxample: mapping of a Point class into the point PostgreSQL Simple example wrapper is _adapter used by theĪ convenient object to write adapters is the AsIs Registered via the register_adapter() function. You can use an adaptation function, taking the object to be adapted asĪrgument and returning a conforming object. Option (maybe because the object to adapt comes from a third party library), If implementing the ISQLQuote interface directly in the object is not an For a simpleĮxample you can take a look at the source code for the Its interface with the required methods doesn’t bother you). having Psycopg as a dependency and polluting Viable if you are the author of the object and if the object is specificallyĭesigned for the database (i.e. Implements getquoted()) or a suitable wrapper object. ISQLQuote, in which case it can return self (if the object also The object can check that the protocol is Object must expose a _conform_() method that will be called with the The object itself is conform, or knows how to make itself conform. There are two basic ways to have a Python object adapted to SQL: Optionally the conform object may expose a Of the object as a string (the method must return bytes in Python 3). Protocol expose a getquoted() method returning the SQL representation The execute() method adapts its arguments to the Is similar to the Object Adaptation proposed in the PEP 246 and is exposedīy the () function. execute ( "INSERT INTO mytable VALUES ( %s, %s, %s ) ", ( 10, 20, 30 )) Adapting new Python types to SQL syntax ¶Īny Python class or type can be adapted to an SQL string. cursor ( cursor_factory = LoggingCursor ) cur. execute ( self, sql, args ) except Exception, exc : logger. cursor ): def execute ( self, sql, args = None ): logger = logging. Import psycopg2 import psycopg2.extensions import logging class LoggingCursor ( psycopg2.
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