File: //opt/alt/python27/lib/python2.7/site-packages/sqlalchemy/dialects/sqlite/pysqlcipher.pyc
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.. dialect:: sqlite+pysqlcipher
:name: pysqlcipher
:dbapi: sqlcipher 3 or pysqlcipher
:connectstring: sqlite+pysqlcipher://:passphrase@/file_path[?kdf_iter=<iter>]
Dialect for support of DBAPIs that make use of the
`SQLCipher <https://www.zetetic.net/sqlcipher>`_ backend.
Driver
------
Current dialect selection logic is:
* If the :paramref:`_sa.create_engine.module` parameter supplies a DBAPI module,
that module is used.
* Otherwise for Python 3, choose https://pypi.org/project/sqlcipher3/
* If not available, fall back to https://pypi.org/project/pysqlcipher3/
* For Python 2, https://pypi.org/project/pysqlcipher/ is used.
.. warning:: The ``pysqlcipher3`` and ``pysqlcipher`` DBAPI drivers are no
longer maintained; the ``sqlcipher3`` driver as of this writing appears
to be current. For future compatibility, any pysqlcipher-compatible DBAPI
may be used as follows::
import sqlcipher_compatible_driver
from sqlalchemy import create_engine
e = create_engine(
"sqlite+pysqlcipher://:password@/dbname.db",
module=sqlcipher_compatible_driver
)
These drivers make use of the SQLCipher engine. This system essentially
introduces new PRAGMA commands to SQLite which allows the setting of a
passphrase and other encryption parameters, allowing the database file to be
encrypted.
Connect Strings
---------------
The format of the connect string is in every way the same as that
of the :mod:`~sqlalchemy.dialects.sqlite.pysqlite` driver, except that the
"password" field is now accepted, which should contain a passphrase::
e = create_engine('sqlite+pysqlcipher://:testing@/foo.db')
For an absolute file path, two leading slashes should be used for the
database name::
e = create_engine('sqlite+pysqlcipher://:testing@//path/to/foo.db')
A selection of additional encryption-related pragmas supported by SQLCipher
as documented at https://www.zetetic.net/sqlcipher/sqlcipher-api/ can be passed
in the query string, and will result in that PRAGMA being called for each
new connection. Currently, ``cipher``, ``kdf_iter``
``cipher_page_size`` and ``cipher_use_hmac`` are supported::
e = create_engine('sqlite+pysqlcipher://:testing@/foo.db?cipher=aes-256-cfb&kdf_iter=64000')
.. warning:: Previous versions of sqlalchemy did not take into consideration
the encryption-related pragmas passed in the url string, that were silently
ignored. This may cause errors when opening files saved by a
previous sqlalchemy version if the encryption options do not match.
Pooling Behavior
----------------
The driver makes a change to the default pool behavior of pysqlite
as described in :ref:`pysqlite_threading_pooling`. The pysqlcipher driver
has been observed to be significantly slower on connection than the
pysqlite driver, most likely due to the encryption overhead, so the
dialect here defaults to using the :class:`.SingletonThreadPool`
implementation,
instead of the :class:`.NullPool` pool used by pysqlite. As always, the pool
implementation is entirely configurable using the
:paramref:`_sa.create_engine.poolclass` parameter; the :class:`.
StaticPool` may
be more feasible for single-threaded use, or :class:`.NullPool` may be used
to prevent unencrypted connections from being held open for long periods of
time, at the expense of slower startup time for new connections.
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