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bpo-8145: Improve isolation_level documentation (GH-8499)

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Initial patch by R. David Murray.
This commit is contained in:
Berker Peksag 2018-07-29 12:01:38 +03:00 • committed by Steve Dower
parent 11eb1a9470
commit a71fed0b75
1 changed files with 21 additions and 13 deletions
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34
Doc/library/sqlite3.rst
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@ -281,7 +281,7 @@ Connection Objects
.. attribute:: isolation_level
Get or set the current isolation level. :const:`None` for autocommit mode or
Get or set the current default isolation level. :const:`None` for autocommit mode or
one of "DEFERRED", "IMMEDIATE" or "EXCLUSIVE". See section
:ref:`sqlite3-controlling-transactions` for a more detailed explanation.
@ -1010,22 +1010,30 @@ timestamp converter.
Controlling Transactions
------------------------
By default, the :mod:`sqlite3` module opens transactions implicitly before a
Data Modification Language (DML) statement (i.e.
The underlying ``sqlite3`` library operates in ``autocommit`` mode by default,
but the Python :mod:`sqlite3` module by default does not.
``autocommit`` mode means that statements that modify the database take effect
immediately. A ``BEGIN`` or ``SAVEPOINT`` statement disables ``autocommit``
mode, and a ``COMMIT``, a ``ROLLBACK``, or a ``RELEASE`` that ends the
outermost transaction, turns ``autocommit`` mode back on.
The Python :mod:`sqlite3` module by default issues a ``BEGIN`` statement
implicitly before a Data Modification Language (DML) statement (i.e.
``INSERT``/``UPDATE``/``DELETE``/``REPLACE``).
You can control which kind of ``BEGIN`` statements sqlite3 implicitly executes
(or none at all) via the *isolation_level* parameter to the :func:`connect`
You can control which kind of ``BEGIN`` statements :mod:`sqlite3` implicitly
executes via the *isolation_level* parameter to the :func:`connect`
call, or via the :attr:`isolation_level` property of connections.
If you specify no *isolation_level*, a plain ``BEGIN`` is used, which is
equivalent to specifying ``DEFERRED``. Other possible values are ``IMMEDIATE``
and ``EXCLUSIVE``.
If you want **autocommit mode**, then set :attr:`isolation_level` to ``None``.
Otherwise leave it at its default, which will result in a plain "BEGIN"
statement, or set it to one of SQLite's supported isolation levels: "DEFERRED",
"IMMEDIATE" or "EXCLUSIVE".
The current transaction state is exposed through the
:attr:`Connection.in_transaction` attribute of the connection object.
You can disable the :mod:`sqlite3` module's implicit transaction management by
setting :attr:`isolation_level` to ``None``. This will leave the underlying
``sqlite3`` library operating in ``autocommit`` mode. You can then completely
control the transaction state by explicitly issuing ``BEGIN``, ``ROLLBACK``,
``SAVEPOINT``, and ``RELEASE`` statements in your code.
.. versionchanged:: 3.6
:mod:`sqlite3` used to implicitly commit an open transaction before DDL