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`psycopg2.pool` -- Connections pooling
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.. sectionauthor:: Daniele Varrazzo <daniele.varrazzo@gmail.com>
.. index::
pair: Connection; Pooling
.. module:: psycopg2.pool
Creating new PostgreSQL connections can be an expensive operation. This
module offers a few pure Python classes implementing simple connection pooling
directly in the client application.
.. class:: AbstractConnectionPool(minconn, maxconn, \*args, \*\*kwargs)
Base class implementing generic key-based pooling code.
New *minconn* connections are created automatically. The pool will support
a maximum of about *maxconn* connections. *\*args* and *\*\*kwargs* are
passed to the `~psycopg2.connect()` function.
The following methods are expected to be implemented by subclasses:
.. method:: getconn(key=None)
Get a free connection from the pool.
The *key* parameter is optional: if used, the connection will be
associated to the key and calling `!getconn()` with the same key again
will return the same connection.
.. method:: putconn(conn, key=None, close=False)
Put away a connection.
If *close* is `!True`, discard the connection from the pool.
*key* should be used consistently with `getconn()`.
.. method:: closeall
Close all the connections handled by the pool.
Note that all the connections are closed, including ones
eventually in use by the application.
The following classes are `AbstractConnectionPool` subclasses ready to
be used.
.. autoclass:: SimpleConnectionPool
.. note:: This pool class is useful only for single-threaded applications.
.. index:: Multithread; Connection pooling
.. autoclass:: ThreadedConnectionPool
.. note:: This pool class can be safely used in multi-threaded applications.
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