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76 lines
2.3 KiB
76 lines
2.3 KiB
from __future__ import annotations
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import abc
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import typing
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from typing import Any
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from typing import ClassVar
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if typing.TYPE_CHECKING:
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from .interfaces import DBAPIConnection
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from .interfaces import Dialect
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class ConnectionCharacteristic(abc.ABC):
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"""An abstract base for an object that can set, get and reset a
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per-connection characteristic, typically one that gets reset when the
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connection is returned to the connection pool.
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transaction isolation is the canonical example, and the
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``IsolationLevelCharacteristic`` implementation provides this for the
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``DefaultDialect``.
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The ``ConnectionCharacteristic`` class should call upon the ``Dialect`` for
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the implementation of each method. The object exists strictly to serve as
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a dialect visitor that can be placed into the
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``DefaultDialect.connection_characteristics`` dictionary where it will take
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effect for calls to :meth:`_engine.Connection.execution_options` and
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related APIs.
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.. versionadded:: 1.4
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"""
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__slots__ = ()
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transactional: ClassVar[bool] = False
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@abc.abstractmethod
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def reset_characteristic(
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self, dialect: Dialect, dbapi_conn: DBAPIConnection
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) -> None:
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"""Reset the characteristic on the connection to its default value."""
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@abc.abstractmethod
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def set_characteristic(
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self, dialect: Dialect, dbapi_conn: DBAPIConnection, value: Any
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) -> None:
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"""set characteristic on the connection to a given value."""
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@abc.abstractmethod
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def get_characteristic(
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self, dialect: Dialect, dbapi_conn: DBAPIConnection
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) -> Any:
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"""Given a DBAPI connection, get the current value of the
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characteristic.
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"""
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class IsolationLevelCharacteristic(ConnectionCharacteristic):
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transactional: ClassVar[bool] = True
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def reset_characteristic(
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self, dialect: Dialect, dbapi_conn: DBAPIConnection
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) -> None:
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dialect.reset_isolation_level(dbapi_conn)
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def set_characteristic(
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self, dialect: Dialect, dbapi_conn: DBAPIConnection, value: Any
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) -> None:
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dialect._assert_and_set_isolation_level(dbapi_conn, value)
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def get_characteristic(
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self, dialect: Dialect, dbapi_conn: DBAPIConnection
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) -> Any:
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return dialect.get_isolation_level(dbapi_conn)
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