# engine/util.py
# Copyright (C) 2005-2024 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 .. import exc
from .. import util
from ..util import collections_abc
from ..util import immutabledict
def connection_memoize(key):
"""Decorator, memoize a function in a connection.info stash.
Only applicable to functions which take no arguments other than a
connection. The memo will be stored in ``connection.info[key]``.
"""
@util.decorator
def decorated(fn, self, connection):
connection = connection.connect()
try:
return connection.info[key]
except KeyError:
connection.info[key] = val = fn(self, connection)
return val
return decorated
_no_tuple = ()
_no_kw = util.immutabledict()
def _distill_params(connection, multiparams, params):
r"""Given arguments from the calling form \*multiparams, \**params,
return a list of bind parameter structures, usually a list of
dictionaries.
In the case of 'raw' execution which accepts positional parameters,
it may be a list of tuples or lists.
"""
if not multiparams:
if params:
connection._warn_for_legacy_exec_format()
return [params]
else:
return []
elif len(multiparams) == 1:
zero = multiparams[0]
if isinstance(zero, (list, tuple)):
if (
not zero
or hasattr(zero[0], "__iter__")
and not hasattr(zero[0], "strip")
):
# execute(stmt, [{}, {}, {}, ...])
# execute(stmt, [(), (), (), ...])
return zero
else:
# this is used by exec_driver_sql only, so a deprecation
# warning would already be coming from passing a plain
# textual statement with positional parameters to
# execute().
# execute(stmt, ("value", "value"))
return [zero]
elif hasattr(zero, "keys"):
# execute(stmt, {"key":"value"})
return [zero]
else:
connection._warn_for_legacy_exec_format()
# execute(stmt, "value")
return [[zero]]
else:
connection._warn_for_legacy_exec_format()
if hasattr(multiparams[0], "__iter__") and not hasattr(
multiparams[0], "strip"
):
return multiparams
else:
return [multiparams]
def _distill_cursor_params(connection, multiparams, params):
"""_distill_params without any warnings. more appropriate for
"cursor" params that can include tuple arguments, lists of tuples,
etc.
"""
if not multiparams:
if params:
return [params]
else:
return []
elif len(multiparams) == 1:
zero = multiparams[0]
if isinstance(zero, (list, tuple)):
if (
not zero
or hasattr(zero[0], "__iter__")
and not hasattr(zero[0], "strip")
):
# execute(stmt, [{}, {}, {}, ...])
# execute(stmt, [(), (), (), ...])
return zero
else:
# this is used by exec_driver_sql only, so a deprecation
# warning would already be coming from passing a plain
# textual statement with positional parameters to
# execute().
# execute(stmt, ("value", "value"))
return [zero]
elif hasattr(zero, "keys"):
# execute(stmt, {"key":"value"})
return [zero]
else:
# execute(stmt, "value")
return [[zero]]
else:
if hasattr(multiparams[0], "__iter__") and not hasattr(
multiparams[0], "strip"
):
return multiparams
else:
return [multiparams]
def _distill_params_20(params):
if params is None:
return _no_tuple, _no_kw
elif isinstance(params, list):
# collections_abc.MutableSequence): # avoid abc.__instancecheck__
if params and not isinstance(
params[0], (collections_abc.Mapping, tuple)
):
raise exc.ArgumentError(
"List argument must consist only of tuples or dictionaries"
)
return (params,), _no_kw
elif isinstance(
params,
(tuple, dict, immutabledict),
# only do abc.__instancecheck__ for Mapping after we've checked
# for plain dictionaries and would otherwise raise
) or isinstance(params, collections_abc.Mapping):
return (params,), _no_kw
else:
raise exc.ArgumentError("mapping or sequence expected for parameters")
class TransactionalContext(object):
"""Apply Python context manager behavior to transaction objects.
Performs validation to ensure the subject of the transaction is not
used if the transaction were ended prematurely.
"""
_trans_subject = None
def _transaction_is_active(self):
raise NotImplementedError()
def _transaction_is_closed(self):
raise NotImplementedError()
def _rollback_can_be_called(self):
"""indicates the object is in a state that is known to be acceptable
for rollback() to be called.
This does not necessarily mean rollback() will succeed or not raise
an error, just that there is currently no state detected that indicates
rollback() would fail or emit warnings.
It also does not mean that there's a transaction in progress, as
it is usually safe to call rollback() even if no transaction is
present.
.. versionadded:: 1.4.28
"""
raise NotImplementedError()
def _get_subject(self):
raise NotImplementedError()
@classmethod
def _trans_ctx_check(cls, subject):
trans_context = subject._trans_context_manager
if trans_context:
if not trans_context._transaction_is_active():
raise exc.InvalidRequestError(
"Can't operate on closed transaction inside context "
"manager. Please complete the context manager "
"before emitting further commands."
)
def __enter__(self):
subject = self._get_subject()
# none for outer transaction, may be non-None for nested
# savepoint, legacy nesting cases
trans_context = subject._trans_context_manager
self._outer_trans_ctx = trans_context
self._trans_subject = subject
subject._trans_context_manager = self
return self
def __exit__(self, type_, value, traceback):
subject = self._trans_subject
# simplistically we could assume that
# "subject._trans_context_manager is self". However, any calling
# code that is manipulating __exit__ directly would break this
# assumption. alembic context manager
# is an example of partial use that just calls __exit__ and
# not __enter__ at the moment. it's safe to assume this is being done
# in the wild also
out_of_band_exit = (
subject is None or subject._trans_context_manager is not self
)
if type_ is None and self._transaction_is_active():
try:
self.commit()
except:
with util.safe_reraise():
if self._rollback_can_be_called():
self.rollback()
finally:
if not out_of_band_exit:
subject._trans_context_manager = self._outer_trans_ctx
self._trans_subject = self._outer_trans_ctx = None
else:
try:
if not self._transaction_is_active():
if not self._transaction_is_closed():
self.close()
else:
if self._rollback_can_be_called():
self.rollback()
finally:
if not out_of_band_exit:
subject._trans_context_manager = self._outer_trans_ctx
self._trans_subject = self._outer_trans_ctx = None
