Update 2025-04-13_16:25:39

venv/lib/python3.11/site-packages/sqlalchemy/engine/characteristics.py

@@ -0,0 +1,155 @@
+# engine/characteristics.py
+# Copyright (C) 2005-2025 the SQLAlchemy authors and contributors
+# <see AUTHORS file>
+#
+# This module is part of SQLAlchemy and is released under
+# the MIT License: https://www.opensource.org/licenses/mit-license.php
+from __future__ import annotations
+
+import abc
+import typing
+from typing import Any
+from typing import ClassVar
+
+if typing.TYPE_CHECKING:
+    from .base import Connection
+    from .interfaces import DBAPIConnection
+    from .interfaces import Dialect
+
+
+class ConnectionCharacteristic(abc.ABC):
+    """An abstract base for an object that can set, get and reset a
+    per-connection characteristic, typically one that gets reset when the
+    connection is returned to the connection pool.
+
+    transaction isolation is the canonical example, and the
+    ``IsolationLevelCharacteristic`` implementation provides this for the
+    ``DefaultDialect``.
+
+    The ``ConnectionCharacteristic`` class should call upon the ``Dialect`` for
+    the implementation of each method.   The object exists strictly to serve as
+    a dialect visitor that can be placed into the
+    ``DefaultDialect.connection_characteristics`` dictionary where it will take
+    effect for calls to :meth:`_engine.Connection.execution_options` and
+    related APIs.
+
+    .. versionadded:: 1.4
+
+    """
+
+    __slots__ = ()
+
+    transactional: ClassVar[bool] = False
+
+    @abc.abstractmethod
+    def reset_characteristic(
+        self, dialect: Dialect, dbapi_conn: DBAPIConnection
+    ) -> None:
+        """Reset the characteristic on the DBAPI connection to its default
+        value."""
+
+    @abc.abstractmethod
+    def set_characteristic(
+        self, dialect: Dialect, dbapi_conn: DBAPIConnection, value: Any
+    ) -> None:
+        """set characteristic on the DBAPI connection to a given value."""
+
+    def set_connection_characteristic(
+        self,
+        dialect: Dialect,
+        conn: Connection,
+        dbapi_conn: DBAPIConnection,
+        value: Any,
+    ) -> None:
+        """set characteristic on the :class:`_engine.Connection` to a given
+        value.
+
+        .. versionadded:: 2.0.30 - added to support elements that are local
+           to the :class:`_engine.Connection` itself.
+
+        """
+        self.set_characteristic(dialect, dbapi_conn, value)
+
+    @abc.abstractmethod
+    def get_characteristic(
+        self, dialect: Dialect, dbapi_conn: DBAPIConnection
+    ) -> Any:
+        """Given a DBAPI connection, get the current value of the
+        characteristic.
+
+        """
+
+    def get_connection_characteristic(
+        self, dialect: Dialect, conn: Connection, dbapi_conn: DBAPIConnection
+    ) -> Any:
+        """Given a :class:`_engine.Connection`, get the current value of the
+        characteristic.
+
+        .. versionadded:: 2.0.30 - added to support elements that are local
+           to the :class:`_engine.Connection` itself.
+
+        """
+        return self.get_characteristic(dialect, dbapi_conn)
+
+
+class IsolationLevelCharacteristic(ConnectionCharacteristic):
+    """Manage the isolation level on a DBAPI connection"""
+
+    transactional: ClassVar[bool] = True
+
+    def reset_characteristic(
+        self, dialect: Dialect, dbapi_conn: DBAPIConnection
+    ) -> None:
+        dialect.reset_isolation_level(dbapi_conn)
+
+    def set_characteristic(
+        self, dialect: Dialect, dbapi_conn: DBAPIConnection, value: Any
+    ) -> None:
+        dialect._assert_and_set_isolation_level(dbapi_conn, value)
+
+    def get_characteristic(
+        self, dialect: Dialect, dbapi_conn: DBAPIConnection
+    ) -> Any:
+        return dialect.get_isolation_level(dbapi_conn)
+
+
+class LoggingTokenCharacteristic(ConnectionCharacteristic):
+    """Manage the 'logging_token' option of a :class:`_engine.Connection`.
+
+    .. versionadded:: 2.0.30
+
+    """
+
+    transactional: ClassVar[bool] = False
+
+    def reset_characteristic(
+        self, dialect: Dialect, dbapi_conn: DBAPIConnection
+    ) -> None:
+        pass
+
+    def set_characteristic(
+        self, dialect: Dialect, dbapi_conn: DBAPIConnection, value: Any
+    ) -> None:
+        raise NotImplementedError()
+
+    def set_connection_characteristic(
+        self,
+        dialect: Dialect,
+        conn: Connection,
+        dbapi_conn: DBAPIConnection,
+        value: Any,
+    ) -> None:
+        if value:
+            conn._message_formatter = lambda msg: "[%s] %s" % (value, msg)
+        else:
+            del conn._message_formatter
+
+    def get_characteristic(
+        self, dialect: Dialect, dbapi_conn: DBAPIConnection
+    ) -> Any:
+        raise NotImplementedError()
+
+    def get_connection_characteristic(
+        self, dialect: Dialect, conn: Connection, dbapi_conn: DBAPIConnection
+    ) -> Any:
+        return conn._execution_options.get("logging_token", None)