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254 lines
8.2 KiB
254 lines
8.2 KiB
# engine/util.py
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# Copyright (C) 2005-2022 the SQLAlchemy authors and contributors
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# <see AUTHORS file>
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: https://www.opensource.org/licenses/mit-license.php
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from .. import exc
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from .. import util
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from ..util import collections_abc
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from ..util import immutabledict
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def connection_memoize(key):
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"""Decorator, memoize a function in a connection.info stash.
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Only applicable to functions which take no arguments other than a
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connection. The memo will be stored in ``connection.info[key]``.
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"""
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@util.decorator
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def decorated(fn, self, connection):
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connection = connection.connect()
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try:
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return connection.info[key]
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except KeyError:
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connection.info[key] = val = fn(self, connection)
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return val
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return decorated
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_no_tuple = ()
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_no_kw = util.immutabledict()
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def _distill_params(connection, multiparams, params):
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r"""Given arguments from the calling form \*multiparams, \**params,
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return a list of bind parameter structures, usually a list of
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dictionaries.
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In the case of 'raw' execution which accepts positional parameters,
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it may be a list of tuples or lists.
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"""
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if not multiparams:
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if params:
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connection._warn_for_legacy_exec_format()
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return [params]
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else:
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return []
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elif len(multiparams) == 1:
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zero = multiparams[0]
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if isinstance(zero, (list, tuple)):
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if (
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not zero
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or hasattr(zero[0], "__iter__")
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and not hasattr(zero[0], "strip")
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):
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# execute(stmt, [{}, {}, {}, ...])
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# execute(stmt, [(), (), (), ...])
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return zero
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else:
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# this is used by exec_driver_sql only, so a deprecation
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# warning would already be coming from passing a plain
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# textual statement with positional parameters to
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# execute().
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# execute(stmt, ("value", "value"))
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return [zero]
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elif hasattr(zero, "keys"):
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# execute(stmt, {"key":"value"})
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return [zero]
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else:
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connection._warn_for_legacy_exec_format()
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# execute(stmt, "value")
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return [[zero]]
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else:
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connection._warn_for_legacy_exec_format()
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if hasattr(multiparams[0], "__iter__") and not hasattr(
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multiparams[0], "strip"
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):
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return multiparams
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else:
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return [multiparams]
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def _distill_cursor_params(connection, multiparams, params):
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"""_distill_params without any warnings. more appropriate for
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"cursor" params that can include tuple arguments, lists of tuples,
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etc.
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"""
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if not multiparams:
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if params:
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return [params]
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else:
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return []
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elif len(multiparams) == 1:
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zero = multiparams[0]
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if isinstance(zero, (list, tuple)):
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if (
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not zero
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or hasattr(zero[0], "__iter__")
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and not hasattr(zero[0], "strip")
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):
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# execute(stmt, [{}, {}, {}, ...])
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# execute(stmt, [(), (), (), ...])
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return zero
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else:
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# this is used by exec_driver_sql only, so a deprecation
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# warning would already be coming from passing a plain
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# textual statement with positional parameters to
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# execute().
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# execute(stmt, ("value", "value"))
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return [zero]
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elif hasattr(zero, "keys"):
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# execute(stmt, {"key":"value"})
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return [zero]
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else:
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# execute(stmt, "value")
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return [[zero]]
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else:
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if hasattr(multiparams[0], "__iter__") and not hasattr(
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multiparams[0], "strip"
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):
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return multiparams
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else:
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return [multiparams]
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def _distill_params_20(params):
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if params is None:
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return _no_tuple, _no_kw
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elif isinstance(params, list):
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# collections_abc.MutableSequence): # avoid abc.__instancecheck__
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if params and not isinstance(
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params[0], (collections_abc.Mapping, tuple)
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):
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raise exc.ArgumentError(
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"List argument must consist only of tuples or dictionaries"
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)
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return (params,), _no_kw
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elif isinstance(
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params,
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(tuple, dict, immutabledict),
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# only do abc.__instancecheck__ for Mapping after we've checked
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# for plain dictionaries and would otherwise raise
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) or isinstance(params, collections_abc.Mapping):
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return (params,), _no_kw
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else:
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raise exc.ArgumentError("mapping or sequence expected for parameters")
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class TransactionalContext(object):
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"""Apply Python context manager behavior to transaction objects.
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Performs validation to ensure the subject of the transaction is not
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used if the transaction were ended prematurely.
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"""
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_trans_subject = None
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def _transaction_is_active(self):
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raise NotImplementedError()
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def _transaction_is_closed(self):
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raise NotImplementedError()
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def _rollback_can_be_called(self):
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"""indicates the object is in a state that is known to be acceptable
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for rollback() to be called.
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This does not necessarily mean rollback() will succeed or not raise
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an error, just that there is currently no state detected that indicates
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rollback() would fail or emit warnings.
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It also does not mean that there's a transaction in progress, as
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it is usually safe to call rollback() even if no transaction is
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present.
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.. versionadded:: 1.4.28
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"""
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raise NotImplementedError()
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def _get_subject(self):
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raise NotImplementedError()
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@classmethod
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def _trans_ctx_check(cls, subject):
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trans_context = subject._trans_context_manager
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if trans_context:
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if not trans_context._transaction_is_active():
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raise exc.InvalidRequestError(
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"Can't operate on closed transaction inside context "
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"manager. Please complete the context manager "
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"before emitting further commands."
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)
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def __enter__(self):
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subject = self._get_subject()
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# none for outer transaction, may be non-None for nested
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# savepoint, legacy nesting cases
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trans_context = subject._trans_context_manager
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self._outer_trans_ctx = trans_context
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self._trans_subject = subject
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subject._trans_context_manager = self
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return self
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def __exit__(self, type_, value, traceback):
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subject = self._trans_subject
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# simplistically we could assume that
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# "subject._trans_context_manager is self". However, any calling
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# code that is manipulating __exit__ directly would break this
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# assumption. alembic context manager
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# is an example of partial use that just calls __exit__ and
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# not __enter__ at the moment. it's safe to assume this is being done
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# in the wild also
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out_of_band_exit = (
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subject is None or subject._trans_context_manager is not self
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)
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if type_ is None and self._transaction_is_active():
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try:
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self.commit()
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except:
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with util.safe_reraise():
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if self._rollback_can_be_called():
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self.rollback()
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finally:
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if not out_of_band_exit:
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subject._trans_context_manager = self._outer_trans_ctx
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self._trans_subject = self._outer_trans_ctx = None
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else:
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try:
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if not self._transaction_is_active():
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if not self._transaction_is_closed():
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self.close()
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else:
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if self._rollback_can_be_called():
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self.rollback()
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finally:
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if not out_of_band_exit:
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subject._trans_context_manager = self._outer_trans_ctx
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self._trans_subject = self._outer_trans_ctx = None
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