diff options
Diffstat (limited to 'lib/sqlalchemy/engine/interfaces.py')
| -rw-r--r-- | lib/sqlalchemy/engine/interfaces.py | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/lib/sqlalchemy/engine/interfaces.py b/lib/sqlalchemy/engine/interfaces.py index 38d2c7a57..fbdf9b829 100644 --- a/lib/sqlalchemy/engine/interfaces.py +++ b/lib/sqlalchemy/engine/interfaces.py @@ -919,6 +919,11 @@ class Dialect(object): isolation level facilities; these APIs should be preferred for most typical use cases. + If the dialect also implements the + :meth:`.Dialect.get_isolation_level_values` method, then the given + level is guaranteed to be one of the string names within that sequence, + and the method will not need to anticipate a lookup failure. + .. seealso:: :meth:`_engine.Connection.get_isolation_level` @@ -990,6 +995,48 @@ class Dialect(object): """ raise NotImplementedError() + def get_isolation_level_values(self, dbapi_conn): + """return a sequence of string isolation level names that are accepted + by this dialect. + + The available names should use the following conventions: + + * use UPPERCASE names. isolation level methods will accept lowercase + names but these are normalized into UPPERCASE before being passed + along to the dialect. + * separate words should be separated by spaces, not underscores, e.g. + ``REPEATABLE READ``. isolation level names will have underscores + converted to spaces before being passed along to the dialect. + * The names for the four standard isolation names to the extent that + they are supported by the backend should be ``READ UNCOMMITTED`` + ``READ COMMITTED``, ``REPEATABLE READ``, ``SERIALIZABLE`` + * if the dialect supports an autocommit option it should be provided + using the isolation level name ``AUTOCOMMIT``. + * Other isolation modes may also be present, provided that they + are named in UPPERCASE and use spaces not underscores. + + This function is used so that the default dialect can check that + a given isolation level parameter is valid, else raises an + :class:`_exc.ArgumentError`. + + A DBAPI connection is passed to the method, in the unlikely event that + the dialect needs to interrogate the connection itself to determine + this list, however it is expected that most backends will return + a hardcoded list of values. If the dialect supports "AUTOCOMMIT", + that value should also be present in the sequence returned. + + The method raises ``NotImplementedError`` by default. If a dialect + does not implement this method, then the default dialect will not + perform any checking on a given isolation level value before passing + it onto the :meth:`.Dialect.set_isolation_level` method. This is + to allow backwards-compatibility with third party dialects that may + not yet be implementing this method. + + .. versionadded:: 2.0 + + """ + raise NotImplementedError() + @classmethod def get_dialect_cls(cls, url): """Given a URL, return the :class:`.Dialect` that will be used. |