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bazarr/libs/sqlalchemy/engine/base.py

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# engine/base.py
# Copyright (C) 2005-2023 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
"""Defines :class:`_engine.Connection` and :class:`_engine.Engine`.
"""
from __future__ import annotations
import contextlib
import sys
import typing
from typing import Any
from typing import Callable
from typing import cast
from typing import Iterable
from typing import Iterator
from typing import List
from typing import Mapping
from typing import NoReturn
from typing import Optional
from typing import overload
from typing import Tuple
from typing import Type
from typing import TypeVar
from typing import Union
from .interfaces import BindTyping
from .interfaces import ConnectionEventsTarget
from .interfaces import DBAPICursor
from .interfaces import ExceptionContext
from .interfaces import ExecuteStyle
from .interfaces import ExecutionContext
from .interfaces import IsolationLevel
from .util import _distill_params_20
from .util import _distill_raw_params
from .util import TransactionalContext
from .. import exc
from .. import inspection
from .. import log
from .. import util
from ..sql import compiler
from ..sql import util as sql_util
if typing.TYPE_CHECKING:
from . import CursorResult
from . import ScalarResult
from .interfaces import _AnyExecuteParams
from .interfaces import _AnyMultiExecuteParams
from .interfaces import _CoreAnyExecuteParams
from .interfaces import _CoreMultiExecuteParams
from .interfaces import _CoreSingleExecuteParams
from .interfaces import _DBAPIAnyExecuteParams
from .interfaces import _DBAPISingleExecuteParams
from .interfaces import _ExecuteOptions
from .interfaces import CompiledCacheType
from .interfaces import CoreExecuteOptionsParameter
from .interfaces import Dialect
from .interfaces import SchemaTranslateMapType
from .reflection import Inspector # noqa
from .url import URL
from ..event import dispatcher
from ..log import _EchoFlagType
from ..pool import _ConnectionFairy
from ..pool import Pool
from ..pool import PoolProxiedConnection
from ..sql import Executable
from ..sql._typing import _InfoType
from ..sql.compiler import Compiled
from ..sql.ddl import ExecutableDDLElement
from ..sql.ddl import SchemaDropper
from ..sql.ddl import SchemaGenerator
from ..sql.functions import FunctionElement
from ..sql.schema import DefaultGenerator
from ..sql.schema import HasSchemaAttr
from ..sql.schema import SchemaItem
from ..sql.selectable import TypedReturnsRows
_T = TypeVar("_T", bound=Any)
_EMPTY_EXECUTION_OPTS: _ExecuteOptions = util.EMPTY_DICT
NO_OPTIONS: Mapping[str, Any] = util.EMPTY_DICT
class Connection(ConnectionEventsTarget, inspection.Inspectable["Inspector"]):
"""Provides high-level functionality for a wrapped DB-API connection.
The :class:`_engine.Connection` object is procured by calling the
:meth:`_engine.Engine.connect` method of the :class:`_engine.Engine`
object, and provides services for execution of SQL statements as well
as transaction control.
The Connection object is **not** thread-safe. While a Connection can be
shared among threads using properly synchronized access, it is still
possible that the underlying DBAPI connection may not support shared
access between threads. Check the DBAPI documentation for details.
The Connection object represents a single DBAPI connection checked out
from the connection pool. In this state, the connection pool has no
affect upon the connection, including its expiration or timeout state.
For the connection pool to properly manage connections, connections
should be returned to the connection pool (i.e. ``connection.close()``)
whenever the connection is not in use.
.. index::
single: thread safety; Connection
"""
dispatch: dispatcher[ConnectionEventsTarget]
_sqla_logger_namespace = "sqlalchemy.engine.Connection"
# used by sqlalchemy.engine.util.TransactionalContext
_trans_context_manager: Optional[TransactionalContext] = None
# legacy as of 2.0, should be eventually deprecated and
# removed. was used in the "pre_ping" recipe that's been in the docs
# a long time
should_close_with_result = False
_dbapi_connection: Optional[PoolProxiedConnection]
_execution_options: _ExecuteOptions
_transaction: Optional[RootTransaction]
_nested_transaction: Optional[NestedTransaction]
def __init__(
self,
engine: Engine,
connection: Optional[PoolProxiedConnection] = None,
_has_events: Optional[bool] = None,
_allow_revalidate: bool = True,
_allow_autobegin: bool = True,
):
"""Construct a new Connection."""
self.engine = engine
self.dialect = dialect = engine.dialect
if connection is None:
try:
self._dbapi_connection = engine.raw_connection()
except dialect.loaded_dbapi.Error as err:
Connection._handle_dbapi_exception_noconnection(
err, dialect, engine
)
raise
else:
self._dbapi_connection = connection
self._transaction = self._nested_transaction = None
self.__savepoint_seq = 0
self.__in_begin = False
self.__can_reconnect = _allow_revalidate
self._allow_autobegin = _allow_autobegin
self._echo = self.engine._should_log_info()
if _has_events is None:
# if _has_events is sent explicitly as False,
# then don't join the dispatch of the engine; we don't
# want to handle any of the engine's events in that case.
self.dispatch = self.dispatch._join(engine.dispatch)
self._has_events = _has_events or (
_has_events is None and engine._has_events
)
self._execution_options = engine._execution_options
if self._has_events or self.engine._has_events:
self.dispatch.engine_connect(self)
@util.memoized_property
def _message_formatter(self) -> Any:
if "logging_token" in self._execution_options:
token = self._execution_options["logging_token"]
return lambda msg: "[%s] %s" % (token, msg)
else:
return None
def _log_info(self, message: str, *arg: Any, **kw: Any) -> None:
fmt = self._message_formatter
if fmt:
message = fmt(message)
if log.STACKLEVEL:
kw["stacklevel"] = 1 + log.STACKLEVEL_OFFSET
self.engine.logger.info(message, *arg, **kw)
def _log_debug(self, message: str, *arg: Any, **kw: Any) -> None:
fmt = self._message_formatter
if fmt:
message = fmt(message)
if log.STACKLEVEL:
kw["stacklevel"] = 1 + log.STACKLEVEL_OFFSET
self.engine.logger.debug(message, *arg, **kw)
@property
def _schema_translate_map(self) -> Optional[SchemaTranslateMapType]:
return self._execution_options.get("schema_translate_map", None)
def schema_for_object(self, obj: HasSchemaAttr) -> Optional[str]:
"""Return the schema name for the given schema item taking into
account current schema translate map.
"""
name = obj.schema
schema_translate_map: Optional[
SchemaTranslateMapType
] = self._execution_options.get("schema_translate_map", None)
if (
schema_translate_map
and name in schema_translate_map
and obj._use_schema_map
):
return schema_translate_map[name]
else:
return name
def __enter__(self) -> Connection:
return self
def __exit__(self, type_: Any, value: Any, traceback: Any) -> None:
self.close()
@overload
def execution_options(
self,
*,
compiled_cache: Optional[CompiledCacheType] = ...,
logging_token: str = ...,
isolation_level: IsolationLevel = ...,
no_parameters: bool = False,
stream_results: bool = False,
max_row_buffer: int = ...,
yield_per: int = ...,
insertmanyvalues_page_size: int = ...,
schema_translate_map: Optional[SchemaTranslateMapType] = ...,
**opt: Any,
) -> Connection:
...
@overload
def execution_options(self, **opt: Any) -> Connection:
...
def execution_options(self, **opt: Any) -> Connection:
r"""Set non-SQL options for the connection which take effect
during execution.
This method modifies this :class:`_engine.Connection` **in-place**;
the return value is the same :class:`_engine.Connection` object
upon which the method is called. Note that this is in contrast
to the behavior of the ``execution_options`` methods on other
objects such as :meth:`_engine.Engine.execution_options` and
:meth:`_sql.Executable.execution_options`. The rationale is that many
such execution options necessarily modify the state of the base
DBAPI connection in any case so there is no feasible means of
keeping the effect of such an option localized to a "sub" connection.
.. versionchanged:: 2.0 The :meth:`_engine.Connection.execution_options`
method, in contrast to other objects with this method, modifies
the connection in-place without creating copy of it.
As discussed elsewhere, the :meth:`_engine.Connection.execution_options`
method accepts any arbitrary parameters including user defined names.
All parameters given are consumable in a number of ways including
by using the :meth:`_engine.Connection.get_execution_options` method.
See the examples at :meth:`_sql.Executable.execution_options`
and :meth:`_engine.Engine.execution_options`.
The keywords that are currently recognized by SQLAlchemy itself
include all those listed under :meth:`.Executable.execution_options`,
as well as others that are specific to :class:`_engine.Connection`.
:param compiled_cache: Available on: :class:`_engine.Connection`,
:class:`_engine.Engine`.
A dictionary where :class:`.Compiled` objects
will be cached when the :class:`_engine.Connection`
compiles a clause
expression into a :class:`.Compiled` object. This dictionary will
supersede the statement cache that may be configured on the
:class:`_engine.Engine` itself. If set to None, caching
is disabled, even if the engine has a configured cache size.
Note that the ORM makes use of its own "compiled" caches for
some operations, including flush operations. The caching
used by the ORM internally supersedes a cache dictionary
specified here.
:param logging_token: Available on: :class:`_engine.Connection`,
:class:`_engine.Engine`, :class:`_sql.Executable`.
Adds the specified string token surrounded by brackets in log
messages logged by the connection, i.e. the logging that's enabled
either via the :paramref:`_sa.create_engine.echo` flag or via the
``logging.getLogger("sqlalchemy.engine")`` logger. This allows a
per-connection or per-sub-engine token to be available which is
useful for debugging concurrent connection scenarios.
.. versionadded:: 1.4.0b2
.. seealso::
:ref:`dbengine_logging_tokens` - usage example
:paramref:`_sa.create_engine.logging_name` - adds a name to the
name used by the Python logger object itself.
:param isolation_level: Available on: :class:`_engine.Connection`,
:class:`_engine.Engine`.
Set the transaction isolation level for the lifespan of this
:class:`_engine.Connection` object.
Valid values include those string
values accepted by the :paramref:`_sa.create_engine.isolation_level`
parameter passed to :func:`_sa.create_engine`. These levels are
semi-database specific; see individual dialect documentation for
valid levels.
The isolation level option applies the isolation level by emitting
statements on the DBAPI connection, and **necessarily affects the
original Connection object overall**. The isolation level will remain
at the given setting until explicitly changed, or when the DBAPI
connection itself is :term:`released` to the connection pool, i.e. the
:meth:`_engine.Connection.close` method is called, at which time an
event handler will emit additional statements on the DBAPI connection
in order to revert the isolation level change.
.. note:: The ``isolation_level`` execution option may only be
established before the :meth:`_engine.Connection.begin` method is
called, as well as before any SQL statements are emitted which
would otherwise trigger "autobegin", or directly after a call to
:meth:`_engine.Connection.commit` or
:meth:`_engine.Connection.rollback`. A database cannot change the
isolation level on a transaction in progress.
.. note:: The ``isolation_level`` execution option is implicitly
reset if the :class:`_engine.Connection` is invalidated, e.g. via
the :meth:`_engine.Connection.invalidate` method, or if a
disconnection error occurs. The new connection produced after the
invalidation will **not** have the selected isolation level
re-applied to it automatically.
.. seealso::
:ref:`dbapi_autocommit`
:meth:`_engine.Connection.get_isolation_level`
- view current level
:param no_parameters: Available on: :class:`_engine.Connection`,
:class:`_sql.Executable`.
When ``True``, if the final parameter
list or dictionary is totally empty, will invoke the
statement on the cursor as ``cursor.execute(statement)``,
not passing the parameter collection at all.
Some DBAPIs such as psycopg2 and mysql-python consider
percent signs as significant only when parameters are
present; this option allows code to generate SQL
containing percent signs (and possibly other characters)
that is neutral regarding whether it's executed by the DBAPI
or piped into a script that's later invoked by
command line tools.
:param stream_results: Available on: :class:`_engine.Connection`,
:class:`_sql.Executable`.
Indicate to the dialect that results should be
"streamed" and not pre-buffered, if possible. For backends
such as PostgreSQL, MySQL and MariaDB, this indicates the use of
a "server side cursor" as opposed to a client side cursor.
Other backends such as that of Oracle may already use server
side cursors by default.
The usage of
:paramref:`_engine.Connection.execution_options.stream_results` is
usually combined with setting a fixed number of rows to to be fetched
in batches, to allow for efficient iteration of database rows while
at the same time not loading all result rows into memory at once;
this can be configured on a :class:`_engine.Result` object using the
:meth:`_engine.Result.yield_per` method, after execution has
returned a new :class:`_engine.Result`. If
:meth:`_engine.Result.yield_per` is not used,
the :paramref:`_engine.Connection.execution_options.stream_results`
mode of operation will instead use a dynamically sized buffer
which buffers sets of rows at a time, growing on each batch
based on a fixed growth size up until a limit which may
be configured using the
:paramref:`_engine.Connection.execution_options.max_row_buffer`
parameter.
When using the ORM to fetch ORM mapped objects from a result,
:meth:`_engine.Result.yield_per` should always be used with
:paramref:`_engine.Connection.execution_options.stream_results`,
so that the ORM does not fetch all rows into new ORM objects at once.
For typical use, the
:paramref:`_engine.Connection.execution_options.yield_per` execution
option should be preferred, which sets up both
:paramref:`_engine.Connection.execution_options.stream_results` and
:meth:`_engine.Result.yield_per` at once. This option is supported
both at a core level by :class:`_engine.Connection` as well as by the
ORM :class:`_engine.Session`; the latter is described at
:ref:`orm_queryguide_yield_per`.
.. seealso::
:ref:`engine_stream_results` - background on
:paramref:`_engine.Connection.execution_options.stream_results`
:paramref:`_engine.Connection.execution_options.max_row_buffer`
:paramref:`_engine.Connection.execution_options.yield_per`
:ref:`orm_queryguide_yield_per` - in the :ref:`queryguide_toplevel`
describing the ORM version of ``yield_per``
:param max_row_buffer: Available on: :class:`_engine.Connection`,
:class:`_sql.Executable`. Sets a maximum
buffer size to use when the
:paramref:`_engine.Connection.execution_options.stream_results`
execution option is used on a backend that supports server side
cursors. The default value if not specified is 1000.
.. seealso::
:paramref:`_engine.Connection.execution_options.stream_results`
:ref:`engine_stream_results`
:param yield_per: Available on: :class:`_engine.Connection`,
:class:`_sql.Executable`. Integer value applied which will
set the :paramref:`_engine.Connection.execution_options.stream_results`
execution option and invoke :meth:`_engine.Result.yield_per`
automatically at once. Allows equivalent functionality as
is present when using this parameter with the ORM.
.. versionadded:: 1.4.40
.. seealso::
:ref:`engine_stream_results` - background and examples
on using server side cursors with Core.
:ref:`orm_queryguide_yield_per` - in the :ref:`queryguide_toplevel`
describing the ORM version of ``yield_per``
:param insertmanyvalues_page_size: Available on: :class:`_engine.Connection`,
:class:`_engine.Engine`. Number of rows to format into an
INSERT statement when the statement uses "insertmanyvalues" mode,
which is a paged form of bulk insert that is used for many backends
when using :term:`executemany` execution typically in conjunction
with RETURNING. Defaults to 1000. May also be modified on a
per-engine basis using the
:paramref:`_sa.create_engine.insertmanyvalues_page_size` parameter.
.. versionadded:: 2.0
.. seealso::
:ref:`engine_insertmanyvalues`
:param schema_translate_map: Available on: :class:`_engine.Connection`,
:class:`_engine.Engine`, :class:`_sql.Executable`.
A dictionary mapping schema names to schema names, that will be
applied to the :paramref:`_schema.Table.schema` element of each
:class:`_schema.Table`
encountered when SQL or DDL expression elements
are compiled into strings; the resulting schema name will be
converted based on presence in the map of the original name.
.. versionadded:: 1.1
.. seealso::
:ref:`schema_translating`
.. seealso::
:meth:`_engine.Engine.execution_options`
:meth:`.Executable.execution_options`
:meth:`_engine.Connection.get_execution_options`
:ref:`orm_queryguide_execution_options` - documentation on all
ORM-specific execution options
""" # noqa
if self._has_events or self.engine._has_events:
self.dispatch.set_connection_execution_options(self, opt)
self._execution_options = self._execution_options.union(opt)
self.dialect.set_connection_execution_options(self, opt)
return self
def get_execution_options(self) -> _ExecuteOptions:
"""Get the non-SQL options which will take effect during execution.
.. versionadded:: 1.3
.. seealso::
:meth:`_engine.Connection.execution_options`
"""
return self._execution_options
@property
def _still_open_and_dbapi_connection_is_valid(self) -> bool:
pool_proxied_connection = self._dbapi_connection
return (
pool_proxied_connection is not None
and pool_proxied_connection.is_valid
)
@property
def closed(self) -> bool:
"""Return True if this connection is closed."""
return self._dbapi_connection is None and not self.__can_reconnect
@property
def invalidated(self) -> bool:
"""Return True if this connection was invalidated.
This does not indicate whether or not the connection was
invalidated at the pool level, however
"""
# prior to 1.4, "invalid" was stored as a state independent of
# "closed", meaning an invalidated connection could be "closed",
# the _dbapi_connection would be None and closed=True, yet the
# "invalid" flag would stay True. This meant that there were
# three separate states (open/valid, closed/valid, closed/invalid)
# when there is really no reason for that; a connection that's
# "closed" does not need to be "invalid". So the state is now
# represented by the two facts alone.
pool_proxied_connection = self._dbapi_connection
return pool_proxied_connection is None and self.__can_reconnect
@property
def connection(self) -> PoolProxiedConnection:
"""The underlying DB-API connection managed by this Connection.
This is a SQLAlchemy connection-pool proxied connection
which then has the attribute
:attr:`_pool._ConnectionFairy.dbapi_connection` that refers to the
actual driver connection.
.. seealso::
:ref:`dbapi_connections`
"""
if self._dbapi_connection is None:
try:
return self._revalidate_connection()
except (exc.PendingRollbackError, exc.ResourceClosedError):
raise
except BaseException as e:
self._handle_dbapi_exception(e, None, None, None, None)
else:
return self._dbapi_connection
def get_isolation_level(self) -> IsolationLevel:
"""Return the current isolation level assigned to this
:class:`_engine.Connection`.
This will typically be the default isolation level as determined
by the dialect, unless if the
:paramref:`.Connection.execution_options.isolation_level`
feature has been used to alter the isolation level on a
per-:class:`_engine.Connection` basis.
This attribute will typically perform a live SQL operation in order
to procure the current isolation level, so the value returned is the
actual level on the underlying DBAPI connection regardless of how
this state was set. Compare to the
:attr:`_engine.Connection.default_isolation_level` accessor
which returns the dialect-level setting without performing a SQL
query.
.. versionadded:: 0.9.9
.. seealso::
:attr:`_engine.Connection.default_isolation_level`
- view default level
:paramref:`_sa.create_engine.isolation_level`
- set per :class:`_engine.Engine` isolation level
:paramref:`.Connection.execution_options.isolation_level`
- set per :class:`_engine.Connection` isolation level
"""
dbapi_connection = self.connection.dbapi_connection
assert dbapi_connection is not None
try:
return self.dialect.get_isolation_level(dbapi_connection)
except BaseException as e:
self._handle_dbapi_exception(e, None, None, None, None)
@property
def default_isolation_level(self) -> Optional[IsolationLevel]:
"""The default isolation level assigned to this
:class:`_engine.Connection`.
This is the isolation level setting that the
:class:`_engine.Connection`
has when first procured via the :meth:`_engine.Engine.connect` method.
This level stays in place until the
:paramref:`.Connection.execution_options.isolation_level` is used
to change the setting on a per-:class:`_engine.Connection` basis.
Unlike :meth:`_engine.Connection.get_isolation_level`,
this attribute is set
ahead of time from the first connection procured by the dialect,
so SQL query is not invoked when this accessor is called.
.. versionadded:: 0.9.9
.. seealso::
:meth:`_engine.Connection.get_isolation_level`
- view current level
:paramref:`_sa.create_engine.isolation_level`
- set per :class:`_engine.Engine` isolation level
:paramref:`.Connection.execution_options.isolation_level`
- set per :class:`_engine.Connection` isolation level
"""
return self.dialect.default_isolation_level
def _invalid_transaction(self) -> NoReturn:
raise exc.PendingRollbackError(
"Can't reconnect until invalid %stransaction is rolled "
"back. Please rollback() fully before proceeding"
% ("savepoint " if self._nested_transaction is not None else ""),
code="8s2b",
)
def _revalidate_connection(self) -> PoolProxiedConnection:
if self.__can_reconnect and self.invalidated:
if self._transaction is not None:
self._invalid_transaction()
self._dbapi_connection = self.engine.raw_connection()
return self._dbapi_connection
raise exc.ResourceClosedError("This Connection is closed")
@property
def info(self) -> _InfoType:
"""Info dictionary associated with the underlying DBAPI connection
referred to by this :class:`_engine.Connection`, allowing user-defined
data to be associated with the connection.
The data here will follow along with the DBAPI connection including
after it is returned to the connection pool and used again
in subsequent instances of :class:`_engine.Connection`.
"""
return self.connection.info
def invalidate(self, exception: Optional[BaseException] = None) -> None:
"""Invalidate the underlying DBAPI connection associated with
this :class:`_engine.Connection`.
An attempt will be made to close the underlying DBAPI connection
immediately; however if this operation fails, the error is logged
but not raised. The connection is then discarded whether or not
close() succeeded.
Upon the next use (where "use" typically means using the
:meth:`_engine.Connection.execute` method or similar),
this :class:`_engine.Connection` will attempt to
procure a new DBAPI connection using the services of the
:class:`_pool.Pool` as a source of connectivity (e.g.
a "reconnection").
If a transaction was in progress (e.g. the
:meth:`_engine.Connection.begin` method has been called) when
:meth:`_engine.Connection.invalidate` method is called, at the DBAPI
level all state associated with this transaction is lost, as
the DBAPI connection is closed. The :class:`_engine.Connection`
will not allow a reconnection to proceed until the
:class:`.Transaction` object is ended, by calling the
:meth:`.Transaction.rollback` method; until that point, any attempt at
continuing to use the :class:`_engine.Connection` will raise an
:class:`~sqlalchemy.exc.InvalidRequestError`.
This is to prevent applications from accidentally
continuing an ongoing transactional operations despite the
fact that the transaction has been lost due to an
invalidation.
The :meth:`_engine.Connection.invalidate` method,
just like auto-invalidation,
will at the connection pool level invoke the
:meth:`_events.PoolEvents.invalidate` event.
:param exception: an optional ``Exception`` instance that's the
reason for the invalidation. is passed along to event handlers
and logging functions.
.. seealso::
:ref:`pool_connection_invalidation`
"""
if self.invalidated:
return
if self.closed:
raise exc.ResourceClosedError("This Connection is closed")
if self._still_open_and_dbapi_connection_is_valid:
pool_proxied_connection = self._dbapi_connection
assert pool_proxied_connection is not None
pool_proxied_connection.invalidate(exception)
self._dbapi_connection = None
def detach(self) -> None:
"""Detach the underlying DB-API connection from its connection pool.
E.g.::
with engine.connect() as conn:
conn.detach()
conn.execute(text("SET search_path TO schema1, schema2"))
# work with connection
# connection is fully closed (since we used "with:", can
# also call .close())
This :class:`_engine.Connection` instance will remain usable.
When closed
(or exited from a context manager context as above),
the DB-API connection will be literally closed and not
returned to its originating pool.
This method can be used to insulate the rest of an application
from a modified state on a connection (such as a transaction
isolation level or similar).
"""
if self.closed:
raise exc.ResourceClosedError("This Connection is closed")
pool_proxied_connection = self._dbapi_connection
if pool_proxied_connection is None:
raise exc.InvalidRequestError(
"Can't detach an invalidated Connection"
)
pool_proxied_connection.detach()
def _autobegin(self) -> None:
if self._allow_autobegin and not self.__in_begin:
self.begin()
def begin(self) -> RootTransaction:
"""Begin a transaction prior to autobegin occurring.
E.g.::
with engine.connect() as conn:
with conn.begin() as trans:
conn.execute(table.insert(), {"username": "sandy"})
The returned object is an instance of :class:`_engine.RootTransaction`.
This object represents the "scope" of the transaction,
which completes when either the :meth:`_engine.Transaction.rollback`
or :meth:`_engine.Transaction.commit` method is called; the object
also works as a context manager as illustrated above.
The :meth:`_engine.Connection.begin` method begins a
transaction that normally will be begun in any case when the connection
is first used to execute a statement. The reason this method might be
used would be to invoke the :meth:`_events.ConnectionEvents.begin`
event at a specific time, or to organize code within the scope of a
connection checkout in terms of context managed blocks, such as::
with engine.connect() as conn:
with conn.begin():
conn.execute(...)
conn.execute(...)
with conn.begin():
conn.execute(...)
conn.execute(...)
The above code is not fundamentally any different in its behavior than
the following code which does not use
:meth:`_engine.Connection.begin`; the below style is referred towards
as "commit as you go" style::
with engine.connect() as conn:
conn.execute(...)
conn.execute(...)
conn.commit()
conn.execute(...)
conn.execute(...)
conn.commit()
From a database point of view, the :meth:`_engine.Connection.begin`
method does not emit any SQL or change the state of the underlying
DBAPI connection in any way; the Python DBAPI does not have any
concept of explicit transaction begin.
.. seealso::
:ref:`tutorial_working_with_transactions` - in the
:ref:`unified_tutorial`
:meth:`_engine.Connection.begin_nested` - use a SAVEPOINT
:meth:`_engine.Connection.begin_twophase` -
use a two phase /XID transaction
:meth:`_engine.Engine.begin` - context manager available from
:class:`_engine.Engine`
"""
if self._transaction is None:
self._transaction = RootTransaction(self)
return self._transaction
else:
raise exc.InvalidRequestError(
"This connection has already initialized a SQLAlchemy "
"Transaction() object via begin() or autobegin; can't "
"call begin() here unless rollback() or commit() "
"is called first."
)
def begin_nested(self) -> NestedTransaction:
"""Begin a nested transaction (i.e. SAVEPOINT) and return a transaction
handle that controls the scope of the SAVEPOINT.
E.g.::
with engine.begin() as connection:
with connection.begin_nested():
connection.execute(table.insert(), {"username": "sandy"})
The returned object is an instance of
:class:`_engine.NestedTransaction`, which includes transactional
methods :meth:`_engine.NestedTransaction.commit` and
:meth:`_engine.NestedTransaction.rollback`; for a nested transaction,
these methods correspond to the operations "RELEASE SAVEPOINT <name>"
and "ROLLBACK TO SAVEPOINT <name>". The name of the savepoint is local
to the :class:`_engine.NestedTransaction` object and is generated
automatically. Like any other :class:`_engine.Transaction`, the
:class:`_engine.NestedTransaction` may be used as a context manager as
illustrated above which will "release" or "rollback" corresponding to
if the operation within the block were successful or raised an
exception.
Nested transactions require SAVEPOINT support in the underlying
database, else the behavior is undefined. SAVEPOINT is commonly used to
run operations within a transaction that may fail, while continuing the
outer transaction. E.g.::
from sqlalchemy import exc
with engine.begin() as connection:
trans = connection.begin_nested()
try:
connection.execute(table.insert(), {"username": "sandy"})
trans.commit()
except exc.IntegrityError: # catch for duplicate username
trans.rollback() # rollback to savepoint
# outer transaction continues
connection.execute( ... )
If :meth:`_engine.Connection.begin_nested` is called without first
calling :meth:`_engine.Connection.begin` or
:meth:`_engine.Engine.begin`, the :class:`_engine.Connection` object
will "autobegin" the outer transaction first. This outer transaction
may be committed using "commit-as-you-go" style, e.g.::
with engine.connect() as connection: # begin() wasn't called
with connection.begin_nested(): will auto-"begin()" first
connection.execute( ... )
# savepoint is released
connection.execute( ... )
# explicitly commit outer transaction
connection.commit()
# can continue working with connection here
.. versionchanged:: 2.0
:meth:`_engine.Connection.begin_nested` will now participate
in the connection "autobegin" behavior that is new as of
2.0 / "future" style connections in 1.4.
.. seealso::
:meth:`_engine.Connection.begin`
:ref:`session_begin_nested` - ORM support for SAVEPOINT
"""
if self._transaction is None:
self._autobegin()
return NestedTransaction(self)
def begin_twophase(self, xid: Optional[Any] = None) -> TwoPhaseTransaction:
"""Begin a two-phase or XA transaction and return a transaction
handle.
The returned object is an instance of :class:`.TwoPhaseTransaction`,
which in addition to the methods provided by
:class:`.Transaction`, also provides a
:meth:`~.TwoPhaseTransaction.prepare` method.
:param xid: the two phase transaction id. If not supplied, a
random id will be generated.
.. seealso::
:meth:`_engine.Connection.begin`
:meth:`_engine.Connection.begin_twophase`
"""
if self._transaction is not None:
raise exc.InvalidRequestError(
"Cannot start a two phase transaction when a transaction "
"is already in progress."
)
if xid is None:
xid = self.engine.dialect.create_xid()
return TwoPhaseTransaction(self, xid)
def commit(self) -> None:
"""Commit the transaction that is currently in progress.
This method commits the current transaction if one has been started.
If no transaction was started, the method has no effect, assuming
the connection is in a non-invalidated state.
A transaction is begun on a :class:`_engine.Connection` automatically
whenever a statement is first executed, or when the
:meth:`_engine.Connection.begin` method is called.
.. note:: The :meth:`_engine.Connection.commit` method only acts upon
the primary database transaction that is linked to the
:class:`_engine.Connection` object. It does not operate upon a
SAVEPOINT that would have been invoked from the
:meth:`_engine.Connection.begin_nested` method; for control of a
SAVEPOINT, call :meth:`_engine.NestedTransaction.commit` on the
:class:`_engine.NestedTransaction` that is returned by the
:meth:`_engine.Connection.begin_nested` method itself.
"""
if self._transaction:
self._transaction.commit()
def rollback(self) -> None:
"""Roll back the transaction that is currently in progress.
This method rolls back the current transaction if one has been started.
If no transaction was started, the method has no effect. If a
transaction was started and the connection is in an invalidated state,
the transaction is cleared using this method.
A transaction is begun on a :class:`_engine.Connection` automatically
whenever a statement is first executed, or when the
:meth:`_engine.Connection.begin` method is called.
.. note:: The :meth:`_engine.Connection.rollback` method only acts
upon the primary database transaction that is linked to the
:class:`_engine.Connection` object. It does not operate upon a
SAVEPOINT that would have been invoked from the
:meth:`_engine.Connection.begin_nested` method; for control of a
SAVEPOINT, call :meth:`_engine.NestedTransaction.rollback` on the
:class:`_engine.NestedTransaction` that is returned by the
:meth:`_engine.Connection.begin_nested` method itself.
"""
if self._transaction:
self._transaction.rollback()
def recover_twophase(self) -> List[Any]:
return self.engine.dialect.do_recover_twophase(self)
def rollback_prepared(self, xid: Any, recover: bool = False) -> None:
self.engine.dialect.do_rollback_twophase(self, xid, recover=recover)
def commit_prepared(self, xid: Any, recover: bool = False) -> None:
self.engine.dialect.do_commit_twophase(self, xid, recover=recover)
def in_transaction(self) -> bool:
"""Return True if a transaction is in progress."""
return self._transaction is not None and self._transaction.is_active
def in_nested_transaction(self) -> bool:
"""Return True if a transaction is in progress."""
return (
self._nested_transaction is not None
and self._nested_transaction.is_active
)
def _is_autocommit_isolation(self) -> bool:
opt_iso = self._execution_options.get("isolation_level", None)
return bool(
opt_iso == "AUTOCOMMIT"
or (
opt_iso is None
and self.engine.dialect._on_connect_isolation_level
== "AUTOCOMMIT"
)
)
def _get_required_transaction(self) -> RootTransaction:
trans = self._transaction
if trans is None:
raise exc.InvalidRequestError("connection is not in a transaction")
return trans
def _get_required_nested_transaction(self) -> NestedTransaction:
trans = self._nested_transaction
if trans is None:
raise exc.InvalidRequestError(
"connection is not in a nested transaction"
)
return trans
def get_transaction(self) -> Optional[RootTransaction]:
"""Return the current root transaction in progress, if any.
.. versionadded:: 1.4
"""
return self._transaction
def get_nested_transaction(self) -> Optional[NestedTransaction]:
"""Return the current nested transaction in progress, if any.
.. versionadded:: 1.4
"""
return self._nested_transaction
def _begin_impl(self, transaction: RootTransaction) -> None:
if self._echo:
if self._is_autocommit_isolation():
self._log_info(
"BEGIN (implicit; DBAPI should not BEGIN due to "
"autocommit mode)"
)
else:
self._log_info("BEGIN (implicit)")
self.__in_begin = True
if self._has_events or self.engine._has_events:
self.dispatch.begin(self)
try:
self.engine.dialect.do_begin(self.connection)
except BaseException as e:
self._handle_dbapi_exception(e, None, None, None, None)
finally:
self.__in_begin = False
def _rollback_impl(self) -> None:
if self._has_events or self.engine._has_events:
self.dispatch.rollback(self)
if self._still_open_and_dbapi_connection_is_valid:
if self._echo:
if self._is_autocommit_isolation():
self._log_info(
"ROLLBACK using DBAPI connection.rollback(), "
"DBAPI should ignore due to autocommit mode"
)
else:
self._log_info("ROLLBACK")
try:
self.engine.dialect.do_rollback(self.connection)
except BaseException as e:
self._handle_dbapi_exception(e, None, None, None, None)
def _commit_impl(self) -> None:
if self._has_events or self.engine._has_events:
self.dispatch.commit(self)
if self._echo:
if self._is_autocommit_isolation():
self._log_info(
"COMMIT using DBAPI connection.commit(), "
"DBAPI should ignore due to autocommit mode"
)
else:
self._log_info("COMMIT")
try:
self.engine.dialect.do_commit(self.connection)
except BaseException as e:
self._handle_dbapi_exception(e, None, None, None, None)
def _savepoint_impl(self, name: Optional[str] = None) -> str:
if self._has_events or self.engine._has_events:
self.dispatch.savepoint(self, name)
if name is None:
self.__savepoint_seq += 1
name = "sa_savepoint_%s" % self.__savepoint_seq
self.engine.dialect.do_savepoint(self, name)
return name
def _rollback_to_savepoint_impl(self, name: str) -> None:
if self._has_events or self.engine._has_events:
self.dispatch.rollback_savepoint(self, name, None)
if self._still_open_and_dbapi_connection_is_valid:
self.engine.dialect.do_rollback_to_savepoint(self, name)
def _release_savepoint_impl(self, name: str) -> None:
if self._has_events or self.engine._has_events:
self.dispatch.release_savepoint(self, name, None)
self.engine.dialect.do_release_savepoint(self, name)
def _begin_twophase_impl(self, transaction: TwoPhaseTransaction) -> None:
if self._echo:
self._log_info("BEGIN TWOPHASE (implicit)")
if self._has_events or self.engine._has_events:
self.dispatch.begin_twophase(self, transaction.xid)
self.__in_begin = True
try:
self.engine.dialect.do_begin_twophase(self, transaction.xid)
except BaseException as e:
self._handle_dbapi_exception(e, None, None, None, None)
finally:
self.__in_begin = False
def _prepare_twophase_impl(self, xid: Any) -> None:
if self._has_events or self.engine._has_events:
self.dispatch.prepare_twophase(self, xid)
assert isinstance(self._transaction, TwoPhaseTransaction)
try:
self.engine.dialect.do_prepare_twophase(self, xid)
except BaseException as e:
self._handle_dbapi_exception(e, None, None, None, None)
def _rollback_twophase_impl(self, xid: Any, is_prepared: bool) -> None:
if self._has_events or self.engine._has_events:
self.dispatch.rollback_twophase(self, xid, is_prepared)
if self._still_open_and_dbapi_connection_is_valid:
assert isinstance(self._transaction, TwoPhaseTransaction)
try:
self.engine.dialect.do_rollback_twophase(
self, xid, is_prepared
)
except BaseException as e:
self._handle_dbapi_exception(e, None, None, None, None)
def _commit_twophase_impl(self, xid: Any, is_prepared: bool) -> None:
if self._has_events or self.engine._has_events:
self.dispatch.commit_twophase(self, xid, is_prepared)
assert isinstance(self._transaction, TwoPhaseTransaction)
try:
self.engine.dialect.do_commit_twophase(self, xid, is_prepared)
except BaseException as e:
self._handle_dbapi_exception(e, None, None, None, None)
def close(self) -> None:
"""Close this :class:`_engine.Connection`.
This results in a release of the underlying database
resources, that is, the DBAPI connection referenced
internally. The DBAPI connection is typically restored
back to the connection-holding :class:`_pool.Pool` referenced
by the :class:`_engine.Engine` that produced this
:class:`_engine.Connection`. Any transactional state present on
the DBAPI connection is also unconditionally released via
the DBAPI connection's ``rollback()`` method, regardless
of any :class:`.Transaction` object that may be
outstanding with regards to this :class:`_engine.Connection`.
This has the effect of also calling :meth:`_engine.Connection.rollback`
if any transaction is in place.
After :meth:`_engine.Connection.close` is called, the
:class:`_engine.Connection` is permanently in a closed state,
and will allow no further operations.
"""
if self._transaction:
self._transaction.close()
skip_reset = True
else:
skip_reset = False
if self._dbapi_connection is not None:
conn = self._dbapi_connection
# as we just closed the transaction, close the connection
# pool connection without doing an additional reset
if skip_reset:
cast("_ConnectionFairy", conn)._close_special(
transaction_reset=True
)
else:
conn.close()
# There is a slight chance that conn.close() may have
# triggered an invalidation here in which case
# _dbapi_connection would already be None, however usually
# it will be non-None here and in a "closed" state.
self._dbapi_connection = None
self.__can_reconnect = False
@overload
def scalar(
self,
statement: TypedReturnsRows[Tuple[_T]],
parameters: Optional[_CoreSingleExecuteParams] = None,
*,
execution_options: Optional[CoreExecuteOptionsParameter] = None,
) -> Optional[_T]:
...
@overload
def scalar(
self,
statement: Executable,
parameters: Optional[_CoreSingleExecuteParams] = None,
*,
execution_options: Optional[CoreExecuteOptionsParameter] = None,
) -> Any:
...
def scalar(
self,
statement: Executable,
parameters: Optional[_CoreSingleExecuteParams] = None,
*,
execution_options: Optional[CoreExecuteOptionsParameter] = None,
) -> Any:
r"""Executes a SQL statement construct and returns a scalar object.
This method is shorthand for invoking the
:meth:`_engine.Result.scalar` method after invoking the
:meth:`_engine.Connection.execute` method. Parameters are equivalent.
:return: a scalar Python value representing the first column of the
first row returned.
"""
distilled_parameters = _distill_params_20(parameters)
try:
meth = statement._execute_on_scalar
except AttributeError as err:
raise exc.ObjectNotExecutableError(statement) from err
else:
return meth(
self,
distilled_parameters,
execution_options or NO_OPTIONS,
)
@overload
def scalars(
self,
statement: TypedReturnsRows[Tuple[_T]],
parameters: Optional[_CoreAnyExecuteParams] = None,
*,
execution_options: Optional[CoreExecuteOptionsParameter] = None,
) -> ScalarResult[_T]:
...
@overload
def scalars(
self,
statement: Executable,
parameters: Optional[_CoreAnyExecuteParams] = None,
*,
execution_options: Optional[CoreExecuteOptionsParameter] = None,
) -> ScalarResult[Any]:
...
def scalars(
self,
statement: Executable,
parameters: Optional[_CoreAnyExecuteParams] = None,
*,
execution_options: Optional[CoreExecuteOptionsParameter] = None,
) -> ScalarResult[Any]:
"""Executes and returns a scalar result set, which yields scalar values
from the first column of each row.
This method is equivalent to calling :meth:`_engine.Connection.execute`
to receive a :class:`_result.Result` object, then invoking the
:meth:`_result.Result.scalars` method to produce a
:class:`_result.ScalarResult` instance.
:return: a :class:`_result.ScalarResult`
.. versionadded:: 1.4.24
"""
return self.execute(
statement, parameters, execution_options=execution_options
).scalars()
@overload
def execute(
self,
statement: TypedReturnsRows[_T],
parameters: Optional[_CoreAnyExecuteParams] = None,
*,
execution_options: Optional[CoreExecuteOptionsParameter] = None,
) -> CursorResult[_T]:
...
@overload
def execute(
self,
statement: Executable,
parameters: Optional[_CoreAnyExecuteParams] = None,
*,
execution_options: Optional[CoreExecuteOptionsParameter] = None,
) -> CursorResult[Any]:
...
def execute(
self,
statement: Executable,
parameters: Optional[_CoreAnyExecuteParams] = None,
*,
execution_options: Optional[CoreExecuteOptionsParameter] = None,
) -> CursorResult[Any]:
r"""Executes a SQL statement construct and returns a
:class:`_engine.CursorResult`.
:param statement: The statement to be executed. This is always
an object that is in both the :class:`_expression.ClauseElement` and
:class:`_expression.Executable` hierarchies, including:
* :class:`_expression.Select`
* :class:`_expression.Insert`, :class:`_expression.Update`,
:class:`_expression.Delete`
* :class:`_expression.TextClause` and
:class:`_expression.TextualSelect`
* :class:`_schema.DDL` and objects which inherit from
:class:`_schema.ExecutableDDLElement`
:param parameters: parameters which will be bound into the statement.
This may be either a dictionary of parameter names to values,
or a mutable sequence (e.g. a list) of dictionaries. When a
list of dictionaries is passed, the underlying statement execution
will make use of the DBAPI ``cursor.executemany()`` method.
When a single dictionary is passed, the DBAPI ``cursor.execute()``
method will be used.
:param execution_options: optional dictionary of execution options,
which will be associated with the statement execution. This
dictionary can provide a subset of the options that are accepted
by :meth:`_engine.Connection.execution_options`.
:return: a :class:`_engine.Result` object.
"""
distilled_parameters = _distill_params_20(parameters)
try:
meth = statement._execute_on_connection
except AttributeError as err:
raise exc.ObjectNotExecutableError(statement) from err
else:
return meth(
self,
distilled_parameters,
execution_options or NO_OPTIONS,
)
def _execute_function(
self,
func: FunctionElement[Any],
distilled_parameters: _CoreMultiExecuteParams,
execution_options: CoreExecuteOptionsParameter,
) -> CursorResult[Any]:
"""Execute a sql.FunctionElement object."""
return self._execute_clauseelement(
func.select(), distilled_parameters, execution_options
)
def _execute_default(
self,
default: DefaultGenerator,
distilled_parameters: _CoreMultiExecuteParams,
execution_options: CoreExecuteOptionsParameter,
) -> Any:
"""Execute a schema.ColumnDefault object."""
execution_options = self._execution_options.merge_with(
execution_options
)
event_multiparams: Optional[_CoreMultiExecuteParams]
event_params: Optional[_CoreAnyExecuteParams]
# note for event handlers, the "distilled parameters" which is always
# a list of dicts is broken out into separate "multiparams" and
# "params" collections, which allows the handler to distinguish
# between an executemany and execute style set of parameters.
if self._has_events or self.engine._has_events:
(
default,
distilled_parameters,
event_multiparams,
event_params,
) = self._invoke_before_exec_event(
default, distilled_parameters, execution_options
)
else:
event_multiparams = event_params = None
try:
conn = self._dbapi_connection
if conn is None:
conn = self._revalidate_connection()
dialect = self.dialect
ctx = dialect.execution_ctx_cls._init_default(
dialect, self, conn, execution_options
)
except (exc.PendingRollbackError, exc.ResourceClosedError):
raise
except BaseException as e:
self._handle_dbapi_exception(e, None, None, None, None)
ret = ctx._exec_default(None, default, None)
if self._has_events or self.engine._has_events:
self.dispatch.after_execute(
self,
default,
event_multiparams,
event_params,
execution_options,
ret,
)
return ret
def _execute_ddl(
self,
ddl: ExecutableDDLElement,
distilled_parameters: _CoreMultiExecuteParams,
execution_options: CoreExecuteOptionsParameter,
) -> CursorResult[Any]:
"""Execute a schema.DDL object."""
execution_options = ddl._execution_options.merge_with(
self._execution_options, execution_options
)
event_multiparams: Optional[_CoreMultiExecuteParams]
event_params: Optional[_CoreSingleExecuteParams]
if self._has_events or self.engine._has_events:
(
ddl,
distilled_parameters,
event_multiparams,
event_params,
) = self._invoke_before_exec_event(
ddl, distilled_parameters, execution_options
)
else:
event_multiparams = event_params = None
exec_opts = self._execution_options.merge_with(execution_options)
schema_translate_map = exec_opts.get("schema_translate_map", None)
dialect = self.dialect
compiled = ddl.compile(
dialect=dialect, schema_translate_map=schema_translate_map
)
ret = self._execute_context(
dialect,
dialect.execution_ctx_cls._init_ddl,
compiled,
None,
execution_options,
compiled,
)
if self._has_events or self.engine._has_events:
self.dispatch.after_execute(
self,
ddl,
event_multiparams,
event_params,
execution_options,
ret,
)
return ret
def _invoke_before_exec_event(
self,
elem: Any,
distilled_params: _CoreMultiExecuteParams,
execution_options: _ExecuteOptions,
) -> Tuple[
Any,
_CoreMultiExecuteParams,
_CoreMultiExecuteParams,
_CoreSingleExecuteParams,
]:
event_multiparams: _CoreMultiExecuteParams
event_params: _CoreSingleExecuteParams
if len(distilled_params) == 1:
event_multiparams, event_params = [], distilled_params[0]
else:
event_multiparams, event_params = distilled_params, {}
for fn in self.dispatch.before_execute:
elem, event_multiparams, event_params = fn(
self,
elem,
event_multiparams,
event_params,
execution_options,
)
if event_multiparams:
distilled_params = list(event_multiparams)
if event_params:
raise exc.InvalidRequestError(
"Event handler can't return non-empty multiparams "
"and params at the same time"
)
elif event_params:
distilled_params = [event_params]
else:
distilled_params = []
return elem, distilled_params, event_multiparams, event_params
def _execute_clauseelement(
self,
elem: Executable,
distilled_parameters: _CoreMultiExecuteParams,
execution_options: CoreExecuteOptionsParameter,
) -> CursorResult[Any]:
"""Execute a sql.ClauseElement object."""
execution_options = elem._execution_options.merge_with(
self._execution_options, execution_options
)
has_events = self._has_events or self.engine._has_events
if has_events:
(
elem,
distilled_parameters,
event_multiparams,
event_params,
) = self._invoke_before_exec_event(
elem, distilled_parameters, execution_options
)
if distilled_parameters:
# ensure we don't retain a link to the view object for keys()
# which links to the values, which we don't want to cache
keys = sorted(distilled_parameters[0])
for_executemany = len(distilled_parameters) > 1
else:
keys = []
for_executemany = False
dialect = self.dialect
schema_translate_map = execution_options.get(
"schema_translate_map", None
)
compiled_cache: Optional[CompiledCacheType] = execution_options.get(
"compiled_cache", self.engine._compiled_cache
)
compiled_sql, extracted_params, cache_hit = elem._compile_w_cache(
dialect=dialect,
compiled_cache=compiled_cache,
column_keys=keys,
for_executemany=for_executemany,
schema_translate_map=schema_translate_map,
linting=self.dialect.compiler_linting | compiler.WARN_LINTING,
)
ret = self._execute_context(
dialect,
dialect.execution_ctx_cls._init_compiled,
compiled_sql,
distilled_parameters,
execution_options,
compiled_sql,
distilled_parameters,
elem,
extracted_params,
cache_hit=cache_hit,
)
if has_events:
self.dispatch.after_execute(
self,
elem,
event_multiparams,
event_params,
execution_options,
ret,
)
return ret
def _execute_compiled(
self,
compiled: Compiled,
distilled_parameters: _CoreMultiExecuteParams,
execution_options: CoreExecuteOptionsParameter = _EMPTY_EXECUTION_OPTS,
) -> CursorResult[Any]:
"""Execute a sql.Compiled object.
TODO: why do we have this? likely deprecate or remove
"""
execution_options = compiled.execution_options.merge_with(
self._execution_options, execution_options
)
if self._has_events or self.engine._has_events:
(
compiled,
distilled_parameters,
event_multiparams,
event_params,
) = self._invoke_before_exec_event(
compiled, distilled_parameters, execution_options
)
dialect = self.dialect
ret = self._execute_context(
dialect,
dialect.execution_ctx_cls._init_compiled,
compiled,
distilled_parameters,
execution_options,
compiled,
distilled_parameters,
None,
None,
)
if self._has_events or self.engine._has_events:
self.dispatch.after_execute(
self,
compiled,
event_multiparams,
event_params,
execution_options,
ret,
)
return ret
def exec_driver_sql(
self,
statement: str,
parameters: Optional[_DBAPIAnyExecuteParams] = None,
execution_options: Optional[CoreExecuteOptionsParameter] = None,
) -> CursorResult[Any]:
r"""Executes a SQL statement construct and returns a
:class:`_engine.CursorResult`.
:param statement: The statement str to be executed. Bound parameters
must use the underlying DBAPI's paramstyle, such as "qmark",
"pyformat", "format", etc.
:param parameters: represent bound parameter values to be used in the
execution. The format is one of: a dictionary of named parameters,
a tuple of positional parameters, or a list containing either
dictionaries or tuples for multiple-execute support.
E.g. multiple dictionaries::
conn.exec_driver_sql(
"INSERT INTO table (id, value) VALUES (%(id)s, %(value)s)",
[{"id":1, "value":"v1"}, {"id":2, "value":"v2"}]
)
Single dictionary::
conn.exec_driver_sql(
"INSERT INTO table (id, value) VALUES (%(id)s, %(value)s)",
dict(id=1, value="v1")
)
Single tuple::
conn.exec_driver_sql(
"INSERT INTO table (id, value) VALUES (?, ?)",
(1, 'v1')
)
.. note:: The :meth:`_engine.Connection.exec_driver_sql` method does
not participate in the
:meth:`_events.ConnectionEvents.before_execute` and
:meth:`_events.ConnectionEvents.after_execute` events. To
intercept calls to :meth:`_engine.Connection.exec_driver_sql`, use
:meth:`_events.ConnectionEvents.before_cursor_execute` and
:meth:`_events.ConnectionEvents.after_cursor_execute`.
.. seealso::
:pep:`249`
"""
distilled_parameters = _distill_raw_params(parameters)
execution_options = self._execution_options.merge_with(
execution_options
)
dialect = self.dialect
ret = self._execute_context(
dialect,
dialect.execution_ctx_cls._init_statement,
statement,
None,
execution_options,
statement,
distilled_parameters,
)
return ret
def _execute_context(
self,
dialect: Dialect,
constructor: Callable[..., ExecutionContext],
statement: Union[str, Compiled],
parameters: Optional[_AnyMultiExecuteParams],
execution_options: _ExecuteOptions,
*args: Any,
**kw: Any,
) -> CursorResult[Any]:
"""Create an :class:`.ExecutionContext` and execute, returning
a :class:`_engine.CursorResult`."""
if execution_options:
yp = execution_options.get("yield_per", None)
if yp:
execution_options = execution_options.union(
{"stream_results": True, "max_row_buffer": yp}
)
try:
conn = self._dbapi_connection
if conn is None:
conn = self._revalidate_connection()
context = constructor(
dialect, self, conn, execution_options, *args, **kw
)
except (exc.PendingRollbackError, exc.ResourceClosedError):
raise
except BaseException as e:
self._handle_dbapi_exception(
e, str(statement), parameters, None, None
)
if (
self._transaction
and not self._transaction.is_active
or (
self._nested_transaction
and not self._nested_transaction.is_active
)
):
self._invalid_transaction()
elif self._trans_context_manager:
TransactionalContext._trans_ctx_check(self)
if self._transaction is None:
self._autobegin()
context.pre_exec()
if context.execute_style is ExecuteStyle.INSERTMANYVALUES:
return self._exec_insertmany_context(
dialect,
context,
)
else:
return self._exec_single_context(
dialect, context, statement, parameters
)
def _exec_single_context(
self,
dialect: Dialect,
context: ExecutionContext,
statement: Union[str, Compiled],
parameters: Optional[_AnyMultiExecuteParams],
) -> CursorResult[Any]:
"""continue the _execute_context() method for a single DBAPI
cursor.execute() or cursor.executemany() call.
"""
if dialect.bind_typing is BindTyping.SETINPUTSIZES:
generic_setinputsizes = context._prepare_set_input_sizes()
if generic_setinputsizes:
try:
dialect.do_set_input_sizes(
context.cursor, generic_setinputsizes, context
)
except BaseException as e:
self._handle_dbapi_exception(
e, str(statement), parameters, None, context
)
cursor, str_statement, parameters = (
context.cursor,
context.statement,
context.parameters,
)
effective_parameters: Optional[_AnyExecuteParams]
if not context.executemany:
effective_parameters = parameters[0]
else:
effective_parameters = parameters
if self._has_events or self.engine._has_events:
for fn in self.dispatch.before_cursor_execute:
str_statement, effective_parameters = fn(
self,
cursor,
str_statement,
effective_parameters,
context,
context.executemany,
)
if self._echo:
self._log_info(str_statement)
stats = context._get_cache_stats()
if not self.engine.hide_parameters:
self._log_info(
"[%s] %r",
stats,
sql_util._repr_params(
effective_parameters,
batches=10,
ismulti=context.executemany,
),
)
else:
self._log_info(
"[%s] [SQL parameters hidden due to hide_parameters=True]",
stats,
)
evt_handled: bool = False
try:
if context.execute_style is ExecuteStyle.EXECUTEMANY:
effective_parameters = cast(
"_CoreMultiExecuteParams", effective_parameters
)
if self.dialect._has_events:
for fn in self.dialect.dispatch.do_executemany:
if fn(
cursor,
str_statement,
effective_parameters,
context,
):
evt_handled = True
break
if not evt_handled:
self.dialect.do_executemany(
cursor,
str_statement,
effective_parameters,
context,
)
elif not effective_parameters and context.no_parameters:
if self.dialect._has_events:
for fn in self.dialect.dispatch.do_execute_no_params:
if fn(cursor, str_statement, context):
evt_handled = True
break
if not evt_handled:
self.dialect.do_execute_no_params(
cursor, str_statement, context
)
else:
effective_parameters = cast(
"_CoreSingleExecuteParams", effective_parameters
)
if self.dialect._has_events:
for fn in self.dialect.dispatch.do_execute:
if fn(
cursor,
str_statement,
effective_parameters,
context,
):
evt_handled = True
break
if not evt_handled:
self.dialect.do_execute(
cursor, str_statement, effective_parameters, context
)
if self._has_events or self.engine._has_events:
self.dispatch.after_cursor_execute(
self,
cursor,
str_statement,
effective_parameters,
context,
context.executemany,
)
context.post_exec()
result = context._setup_result_proxy()
except BaseException as e:
self._handle_dbapi_exception(
e, str_statement, effective_parameters, cursor, context
)
return result
def _exec_insertmany_context(
self,
dialect: Dialect,
context: ExecutionContext,
) -> CursorResult[Any]:
"""continue the _execute_context() method for an "insertmanyvalues"
operation, which will invoke DBAPI
cursor.execute() one or more times with individual log and
event hook calls.
"""
if dialect.bind_typing is BindTyping.SETINPUTSIZES:
generic_setinputsizes = context._prepare_set_input_sizes()
else:
generic_setinputsizes = None
cursor, str_statement, parameters = (
context.cursor,
context.statement,
context.parameters,
)
effective_parameters = parameters
engine_events = self._has_events or self.engine._has_events
if self.dialect._has_events:
do_execute_dispatch: Iterable[
Any
] = self.dialect.dispatch.do_execute
else:
do_execute_dispatch = ()
if self._echo:
stats = context._get_cache_stats() + " (insertmanyvalues)"
for (
sub_stmt,
sub_params,
setinputsizes,
batchnum,
totalbatches,
) in dialect._deliver_insertmanyvalues_batches(
cursor,
str_statement,
effective_parameters,
generic_setinputsizes,
context,
):
if setinputsizes:
try:
dialect.do_set_input_sizes(
context.cursor, setinputsizes, context
)
except BaseException as e:
self._handle_dbapi_exception(
e,
sql_util._long_statement(sub_stmt),
sub_params,
None,
context,
)
if engine_events:
for fn in self.dispatch.before_cursor_execute:
sub_stmt, sub_params = fn(
self,
cursor,
sub_stmt,
sub_params,
context,
True,
)
if self._echo:
self._log_info(sql_util._long_statement(sub_stmt))
if batchnum > 1:
stats = (
f"insertmanyvalues batch {batchnum} "
f"of {totalbatches}"
)
if not self.engine.hide_parameters:
self._log_info(
"[%s] %r",
stats,
sql_util._repr_params(
sub_params,
batches=10,
ismulti=False,
),
)
else:
self._log_info(
"[%s] [SQL parameters hidden due to "
"hide_parameters=True]",
stats,
)
try:
for fn in do_execute_dispatch:
if fn(
cursor,
sub_stmt,
sub_params,
context,
):
break
else:
dialect.do_execute(cursor, sub_stmt, sub_params, context)
except BaseException as e:
self._handle_dbapi_exception(
e,
sql_util._long_statement(sub_stmt),
sub_params,
cursor,
context,
is_sub_exec=True,
)
if engine_events:
self.dispatch.after_cursor_execute(
self,
cursor,
str_statement,
effective_parameters,
context,
context.executemany,
)
try:
context.post_exec()
result = context._setup_result_proxy()
except BaseException as e:
self._handle_dbapi_exception(
e, str_statement, effective_parameters, cursor, context
)
return result
def _cursor_execute(
self,
cursor: DBAPICursor,
statement: str,
parameters: _DBAPISingleExecuteParams,
context: Optional[ExecutionContext] = None,
) -> None:
"""Execute a statement + params on the given cursor.
Adds appropriate logging and exception handling.
This method is used by DefaultDialect for special-case
executions, such as for sequences and column defaults.
The path of statement execution in the majority of cases
terminates at _execute_context().
"""
if self._has_events or self.engine._has_events:
for fn in self.dispatch.before_cursor_execute:
statement, parameters = fn(
self, cursor, statement, parameters, context, False
)
if self._echo:
self._log_info(statement)
self._log_info("[raw sql] %r", parameters)
try:
for fn in (
()
if not self.dialect._has_events
else self.dialect.dispatch.do_execute
):
if fn(cursor, statement, parameters, context):
break
else:
self.dialect.do_execute(cursor, statement, parameters, context)
except BaseException as e:
self._handle_dbapi_exception(
e, statement, parameters, cursor, context
)
if self._has_events or self.engine._has_events:
self.dispatch.after_cursor_execute(
self, cursor, statement, parameters, context, False
)
def _safe_close_cursor(self, cursor: DBAPICursor) -> None:
"""Close the given cursor, catching exceptions
and turning into log warnings.
"""
try:
cursor.close()
except Exception:
# log the error through the connection pool's logger.
self.engine.pool.logger.error(
"Error closing cursor", exc_info=True
)
_reentrant_error = False
_is_disconnect = False
def _handle_dbapi_exception(
self,
e: BaseException,
statement: Optional[str],
parameters: Optional[_AnyExecuteParams],
cursor: Optional[DBAPICursor],
context: Optional[ExecutionContext],
is_sub_exec: bool = False,
) -> NoReturn:
exc_info = sys.exc_info()
is_exit_exception = util.is_exit_exception(e)
if not self._is_disconnect:
self._is_disconnect = (
isinstance(e, self.dialect.loaded_dbapi.Error)
and not self.closed
and self.dialect.is_disconnect(
e,
self._dbapi_connection if not self.invalidated else None,
cursor,
)
) or (is_exit_exception and not self.closed)
invalidate_pool_on_disconnect = not is_exit_exception
ismulti: bool = (
not is_sub_exec and context.executemany
if context is not None
else False
)
if self._reentrant_error:
raise exc.DBAPIError.instance(
statement,
parameters,
e,
self.dialect.loaded_dbapi.Error,
hide_parameters=self.engine.hide_parameters,
dialect=self.dialect,
ismulti=ismulti,
).with_traceback(exc_info[2]) from e
self._reentrant_error = True
try:
# non-DBAPI error - if we already got a context,
# or there's no string statement, don't wrap it
should_wrap = isinstance(e, self.dialect.loaded_dbapi.Error) or (
statement is not None
and context is None
and not is_exit_exception
)
if should_wrap:
sqlalchemy_exception = exc.DBAPIError.instance(
statement,
parameters,
cast(Exception, e),
self.dialect.loaded_dbapi.Error,
hide_parameters=self.engine.hide_parameters,
connection_invalidated=self._is_disconnect,
dialect=self.dialect,
ismulti=ismulti,
)
else:
sqlalchemy_exception = None
newraise = None
if (self.dialect._has_events) and not self._execution_options.get(
"skip_user_error_events", False
):
ctx = ExceptionContextImpl(
e,
sqlalchemy_exception,
self.engine,
self.dialect,
self,
cursor,
statement,
parameters,
context,
self._is_disconnect,
invalidate_pool_on_disconnect,
False,
)
for fn in self.dialect.dispatch.handle_error:
try:
# handler returns an exception;
# call next handler in a chain
per_fn = fn(ctx)
if per_fn is not None:
ctx.chained_exception = newraise = per_fn
except Exception as _raised:
# handler raises an exception - stop processing
newraise = _raised
break
if self._is_disconnect != ctx.is_disconnect:
self._is_disconnect = ctx.is_disconnect
if sqlalchemy_exception:
sqlalchemy_exception.connection_invalidated = (
ctx.is_disconnect
)
# set up potentially user-defined value for
# invalidate pool.
invalidate_pool_on_disconnect = (
ctx.invalidate_pool_on_disconnect
)
if should_wrap and context:
context.handle_dbapi_exception(e)
if not self._is_disconnect:
if cursor:
self._safe_close_cursor(cursor)
# "autorollback" was mostly relevant in 1.x series.
# It's very unlikely to reach here, as the connection
# does autobegin so when we are here, we are usually
# in an explicit / semi-explicit transaction.
# however we have a test which manufactures this
# scenario in any case using an event handler.
# test/engine/test_execute.py-> test_actual_autorollback
if not self.in_transaction():
self._rollback_impl()
if newraise:
raise newraise.with_traceback(exc_info[2]) from e
elif should_wrap:
assert sqlalchemy_exception is not None
raise sqlalchemy_exception.with_traceback(exc_info[2]) from e
else:
assert exc_info[1] is not None
raise exc_info[1].with_traceback(exc_info[2])
finally:
del self._reentrant_error
if self._is_disconnect:
del self._is_disconnect
if not self.invalidated:
dbapi_conn_wrapper = self._dbapi_connection
assert dbapi_conn_wrapper is not None
if invalidate_pool_on_disconnect:
self.engine.pool._invalidate(dbapi_conn_wrapper, e)
self.invalidate(e)
@classmethod
def _handle_dbapi_exception_noconnection(
cls,
e: BaseException,
dialect: Dialect,
engine: Optional[Engine] = None,
is_disconnect: Optional[bool] = None,
invalidate_pool_on_disconnect: bool = True,
is_pre_ping: bool = False,
) -> NoReturn:
exc_info = sys.exc_info()
if is_disconnect is None:
is_disconnect = isinstance(
e, dialect.loaded_dbapi.Error
) and dialect.is_disconnect(e, None, None)
should_wrap = isinstance(e, dialect.loaded_dbapi.Error)
if should_wrap:
sqlalchemy_exception = exc.DBAPIError.instance(
None,
None,
cast(Exception, e),
dialect.loaded_dbapi.Error,
hide_parameters=engine.hide_parameters
if engine is not None
else False,
connection_invalidated=is_disconnect,
dialect=dialect,
)
else:
sqlalchemy_exception = None
newraise = None
if dialect._has_events:
ctx = ExceptionContextImpl(
e,
sqlalchemy_exception,
engine,
dialect,
None,
None,
None,
None,
None,
is_disconnect,
invalidate_pool_on_disconnect,
is_pre_ping,
)
for fn in dialect.dispatch.handle_error:
try:
# handler returns an exception;
# call next handler in a chain
per_fn = fn(ctx)
if per_fn is not None:
ctx.chained_exception = newraise = per_fn
except Exception as _raised:
# handler raises an exception - stop processing
newraise = _raised
break
if sqlalchemy_exception and is_disconnect != ctx.is_disconnect:
sqlalchemy_exception.connection_invalidated = (
is_disconnect
) = ctx.is_disconnect
if newraise:
raise newraise.with_traceback(exc_info[2]) from e
elif should_wrap:
assert sqlalchemy_exception is not None
raise sqlalchemy_exception.with_traceback(exc_info[2]) from e
else:
assert exc_info[1] is not None
raise exc_info[1].with_traceback(exc_info[2])
def _run_ddl_visitor(
self,
visitorcallable: Type[Union[SchemaGenerator, SchemaDropper]],
element: SchemaItem,
**kwargs: Any,
) -> None:
"""run a DDL visitor.
This method is only here so that the MockConnection can change the
options given to the visitor so that "checkfirst" is skipped.
"""
visitorcallable(self.dialect, self, **kwargs).traverse_single(element)
class ExceptionContextImpl(ExceptionContext):
"""Implement the :class:`.ExceptionContext` interface."""
__slots__ = (
"connection",
"engine",
"dialect",
"cursor",
"statement",
"parameters",
"original_exception",
"sqlalchemy_exception",
"chained_exception",
"execution_context",
"is_disconnect",
"invalidate_pool_on_disconnect",
"is_pre_ping",
)
def __init__(
self,
exception: BaseException,
sqlalchemy_exception: Optional[exc.StatementError],
engine: Optional[Engine],
dialect: Dialect,
connection: Optional[Connection],
cursor: Optional[DBAPICursor],
statement: Optional[str],
parameters: Optional[_DBAPIAnyExecuteParams],
context: Optional[ExecutionContext],
is_disconnect: bool,
invalidate_pool_on_disconnect: bool,
is_pre_ping: bool,
):
self.engine = engine
self.dialect = dialect
self.connection = connection
self.sqlalchemy_exception = sqlalchemy_exception
self.original_exception = exception
self.execution_context = context
self.statement = statement
self.parameters = parameters
self.is_disconnect = is_disconnect
self.invalidate_pool_on_disconnect = invalidate_pool_on_disconnect
self.is_pre_ping = is_pre_ping
class Transaction(TransactionalContext):
"""Represent a database transaction in progress.
The :class:`.Transaction` object is procured by
calling the :meth:`_engine.Connection.begin` method of
:class:`_engine.Connection`::
from sqlalchemy import create_engine
engine = create_engine("postgresql+psycopg2://scott:tiger@localhost/test")
connection = engine.connect()
trans = connection.begin()
connection.execute(text("insert into x (a, b) values (1, 2)"))
trans.commit()
The object provides :meth:`.rollback` and :meth:`.commit`
methods in order to control transaction boundaries. It
also implements a context manager interface so that
the Python ``with`` statement can be used with the
:meth:`_engine.Connection.begin` method::
with connection.begin():
connection.execute(text("insert into x (a, b) values (1, 2)"))
The Transaction object is **not** threadsafe.
.. seealso::
:meth:`_engine.Connection.begin`
:meth:`_engine.Connection.begin_twophase`
:meth:`_engine.Connection.begin_nested`
.. index::
single: thread safety; Transaction
""" # noqa
__slots__ = ()
_is_root: bool = False
is_active: bool
connection: Connection
def __init__(self, connection: Connection):
raise NotImplementedError()
@property
def _deactivated_from_connection(self) -> bool:
"""True if this transaction is totally deactivated from the connection
and therefore can no longer affect its state.
"""
raise NotImplementedError()
def _do_close(self) -> None:
raise NotImplementedError()
def _do_rollback(self) -> None:
raise NotImplementedError()
def _do_commit(self) -> None:
raise NotImplementedError()
@property
def is_valid(self) -> bool:
return self.is_active and not self.connection.invalidated
def close(self) -> None:
"""Close this :class:`.Transaction`.
If this transaction is the base transaction in a begin/commit
nesting, the transaction will rollback(). Otherwise, the
method returns.
This is used to cancel a Transaction without affecting the scope of
an enclosing transaction.
"""
try:
self._do_close()
finally:
assert not self.is_active
def rollback(self) -> None:
"""Roll back this :class:`.Transaction`.
The implementation of this may vary based on the type of transaction in
use:
* For a simple database transaction (e.g. :class:`.RootTransaction`),
it corresponds to a ROLLBACK.
* For a :class:`.NestedTransaction`, it corresponds to a
"ROLLBACK TO SAVEPOINT" operation.
* For a :class:`.TwoPhaseTransaction`, DBAPI-specific methods for two
phase transactions may be used.
"""
try:
self._do_rollback()
finally:
assert not self.is_active
def commit(self) -> None:
"""Commit this :class:`.Transaction`.
The implementation of this may vary based on the type of transaction in
use:
* For a simple database transaction (e.g. :class:`.RootTransaction`),
it corresponds to a COMMIT.
* For a :class:`.NestedTransaction`, it corresponds to a
"RELEASE SAVEPOINT" operation.
* For a :class:`.TwoPhaseTransaction`, DBAPI-specific methods for two
phase transactions may be used.
"""
try:
self._do_commit()
finally:
assert not self.is_active
def _get_subject(self) -> Connection:
return self.connection
def _transaction_is_active(self) -> bool:
return self.is_active
def _transaction_is_closed(self) -> bool:
return not self._deactivated_from_connection
def _rollback_can_be_called(self) -> bool:
# for RootTransaction / NestedTransaction, it's safe to call
# rollback() even if the transaction is deactive and no warnings
# will be emitted. tested in
# test_transaction.py -> test_no_rollback_in_deactive(?:_savepoint)?
return True
class RootTransaction(Transaction):
"""Represent the "root" transaction on a :class:`_engine.Connection`.
This corresponds to the current "BEGIN/COMMIT/ROLLBACK" that's occurring
for the :class:`_engine.Connection`. The :class:`_engine.RootTransaction`
is created by calling upon the :meth:`_engine.Connection.begin` method, and
remains associated with the :class:`_engine.Connection` throughout its
active span. The current :class:`_engine.RootTransaction` in use is
accessible via the :attr:`_engine.Connection.get_transaction` method of
:class:`_engine.Connection`.
In :term:`2.0 style` use, the :class:`_engine.Connection` also employs
"autobegin" behavior that will create a new
:class:`_engine.RootTransaction` whenever a connection in a
non-transactional state is used to emit commands on the DBAPI connection.
The scope of the :class:`_engine.RootTransaction` in 2.0 style
use can be controlled using the :meth:`_engine.Connection.commit` and
:meth:`_engine.Connection.rollback` methods.
"""
_is_root = True
__slots__ = ("connection", "is_active")
def __init__(self, connection: Connection):
assert connection._transaction is None
if connection._trans_context_manager:
TransactionalContext._trans_ctx_check(connection)
self.connection = connection
self._connection_begin_impl()
connection._transaction = self
self.is_active = True
def _deactivate_from_connection(self) -> None:
if self.is_active:
assert self.connection._transaction is self
self.is_active = False
elif self.connection._transaction is not self:
util.warn("transaction already deassociated from connection")
@property
def _deactivated_from_connection(self) -> bool:
return self.connection._transaction is not self
def _connection_begin_impl(self) -> None:
self.connection._begin_impl(self)
def _connection_rollback_impl(self) -> None:
self.connection._rollback_impl()
def _connection_commit_impl(self) -> None:
self.connection._commit_impl()
def _close_impl(self, try_deactivate: bool = False) -> None:
try:
if self.is_active:
self._connection_rollback_impl()
if self.connection._nested_transaction:
self.connection._nested_transaction._cancel()
finally:
if self.is_active or try_deactivate:
self._deactivate_from_connection()
if self.connection._transaction is self:
self.connection._transaction = None
assert not self.is_active
assert self.connection._transaction is not self
def _do_close(self) -> None:
self._close_impl()
def _do_rollback(self) -> None:
self._close_impl(try_deactivate=True)
def _do_commit(self) -> None:
if self.is_active:
assert self.connection._transaction is self
try:
self._connection_commit_impl()
finally:
# whether or not commit succeeds, cancel any
# nested transactions, make this transaction "inactive"
# and remove it as a reset agent
if self.connection._nested_transaction:
self.connection._nested_transaction._cancel()
self._deactivate_from_connection()
# ...however only remove as the connection's current transaction
# if commit succeeded. otherwise it stays on so that a rollback
# needs to occur.
self.connection._transaction = None
else:
if self.connection._transaction is self:
self.connection._invalid_transaction()
else:
raise exc.InvalidRequestError("This transaction is inactive")
assert not self.is_active
assert self.connection._transaction is not self
class NestedTransaction(Transaction):
"""Represent a 'nested', or SAVEPOINT transaction.
The :class:`.NestedTransaction` object is created by calling the
:meth:`_engine.Connection.begin_nested` method of
:class:`_engine.Connection`.
When using :class:`.NestedTransaction`, the semantics of "begin" /
"commit" / "rollback" are as follows:
* the "begin" operation corresponds to the "BEGIN SAVEPOINT" command, where
the savepoint is given an explicit name that is part of the state
of this object.
* The :meth:`.NestedTransaction.commit` method corresponds to a
"RELEASE SAVEPOINT" operation, using the savepoint identifier associated
with this :class:`.NestedTransaction`.
* The :meth:`.NestedTransaction.rollback` method corresponds to a
"ROLLBACK TO SAVEPOINT" operation, using the savepoint identifier
associated with this :class:`.NestedTransaction`.
The rationale for mimicking the semantics of an outer transaction in
terms of savepoints so that code may deal with a "savepoint" transaction
and an "outer" transaction in an agnostic way.
.. seealso::
:ref:`session_begin_nested` - ORM version of the SAVEPOINT API.
"""
__slots__ = ("connection", "is_active", "_savepoint", "_previous_nested")
_savepoint: str
def __init__(self, connection: Connection):
assert connection._transaction is not None
if connection._trans_context_manager:
TransactionalContext._trans_ctx_check(connection)
self.connection = connection
self._savepoint = self.connection._savepoint_impl()
self.is_active = True
self._previous_nested = connection._nested_transaction
connection._nested_transaction = self
def _deactivate_from_connection(self, warn: bool = True) -> None:
if self.connection._nested_transaction is self:
self.connection._nested_transaction = self._previous_nested
elif warn:
util.warn(
"nested transaction already deassociated from connection"
)
@property
def _deactivated_from_connection(self) -> bool:
return self.connection._nested_transaction is not self
def _cancel(self) -> None:
# called by RootTransaction when the outer transaction is
# committed, rolled back, or closed to cancel all savepoints
# without any action being taken
self.is_active = False
self._deactivate_from_connection()
if self._previous_nested:
self._previous_nested._cancel()
def _close_impl(
self, deactivate_from_connection: bool, warn_already_deactive: bool
) -> None:
try:
if (
self.is_active
and self.connection._transaction
and self.connection._transaction.is_active
):
self.connection._rollback_to_savepoint_impl(self._savepoint)
finally:
self.is_active = False
if deactivate_from_connection:
self._deactivate_from_connection(warn=warn_already_deactive)
assert not self.is_active
if deactivate_from_connection:
assert self.connection._nested_transaction is not self
def _do_close(self) -> None:
self._close_impl(True, False)
def _do_rollback(self) -> None:
self._close_impl(True, True)
def _do_commit(self) -> None:
if self.is_active:
try:
self.connection._release_savepoint_impl(self._savepoint)
finally:
# nested trans becomes inactive on failed release
# unconditionally. this prevents it from trying to
# emit SQL when it rolls back.
self.is_active = False
# but only de-associate from connection if it succeeded
self._deactivate_from_connection()
else:
if self.connection._nested_transaction is self:
self.connection._invalid_transaction()
else:
raise exc.InvalidRequestError(
"This nested transaction is inactive"
)
class TwoPhaseTransaction(RootTransaction):
"""Represent a two-phase transaction.
A new :class:`.TwoPhaseTransaction` object may be procured
using the :meth:`_engine.Connection.begin_twophase` method.
The interface is the same as that of :class:`.Transaction`
with the addition of the :meth:`prepare` method.
"""
__slots__ = ("xid", "_is_prepared")
xid: Any
def __init__(self, connection: Connection, xid: Any):
self._is_prepared = False
self.xid = xid
super().__init__(connection)
def prepare(self) -> None:
"""Prepare this :class:`.TwoPhaseTransaction`.
After a PREPARE, the transaction can be committed.
"""
if not self.is_active:
raise exc.InvalidRequestError("This transaction is inactive")
self.connection._prepare_twophase_impl(self.xid)
self._is_prepared = True
def _connection_begin_impl(self) -> None:
self.connection._begin_twophase_impl(self)
def _connection_rollback_impl(self) -> None:
self.connection._rollback_twophase_impl(self.xid, self._is_prepared)
def _connection_commit_impl(self) -> None:
self.connection._commit_twophase_impl(self.xid, self._is_prepared)
class Engine(
ConnectionEventsTarget, log.Identified, inspection.Inspectable["Inspector"]
):
"""
Connects a :class:`~sqlalchemy.pool.Pool` and
:class:`~sqlalchemy.engine.interfaces.Dialect` together to provide a
source of database connectivity and behavior.
An :class:`_engine.Engine` object is instantiated publicly using the
:func:`~sqlalchemy.create_engine` function.
.. seealso::
:doc:`/core/engines`
:ref:`connections_toplevel`
"""
dispatch: dispatcher[ConnectionEventsTarget]
_compiled_cache: Optional[CompiledCacheType]
_execution_options: _ExecuteOptions = _EMPTY_EXECUTION_OPTS
_has_events: bool = False
_connection_cls: Type[Connection] = Connection
_sqla_logger_namespace: str = "sqlalchemy.engine.Engine"
_is_future: bool = False
_schema_translate_map: Optional[SchemaTranslateMapType] = None
_option_cls: Type[OptionEngine]
dialect: Dialect
pool: Pool
url: URL
hide_parameters: bool
def __init__(
self,
pool: Pool,
dialect: Dialect,
url: URL,
logging_name: Optional[str] = None,
echo: Optional[_EchoFlagType] = None,
query_cache_size: int = 500,
execution_options: Optional[Mapping[str, Any]] = None,
hide_parameters: bool = False,
):
self.pool = pool
self.url = url
self.dialect = dialect
if logging_name:
self.logging_name = logging_name
self.echo = echo
self.hide_parameters = hide_parameters
if query_cache_size != 0:
self._compiled_cache = util.LRUCache(
query_cache_size, size_alert=self._lru_size_alert
)
else:
self._compiled_cache = None
log.instance_logger(self, echoflag=echo)
if execution_options:
self.update_execution_options(**execution_options)
def _lru_size_alert(self, cache: util.LRUCache[Any, Any]) -> None:
if self._should_log_info():
self.logger.info(
"Compiled cache size pruning from %d items to %d. "
"Increase cache size to reduce the frequency of pruning.",
len(cache),
cache.capacity,
)
@property
def engine(self) -> Engine:
"""Returns this :class:`.Engine`.
Used for legacy schemes that accept :class:`.Connection` /
:class:`.Engine` objects within the same variable.
"""
return self
def clear_compiled_cache(self) -> None:
"""Clear the compiled cache associated with the dialect.
This applies **only** to the built-in cache that is established
via the :paramref:`_engine.create_engine.query_cache_size` parameter.
It will not impact any dictionary caches that were passed via the
:paramref:`.Connection.execution_options.query_cache` parameter.
.. versionadded:: 1.4
"""
if self._compiled_cache:
self._compiled_cache.clear()
def update_execution_options(self, **opt: Any) -> None:
r"""Update the default execution_options dictionary
of this :class:`_engine.Engine`.
The given keys/values in \**opt are added to the
default execution options that will be used for
all connections. The initial contents of this dictionary
can be sent via the ``execution_options`` parameter
to :func:`_sa.create_engine`.
.. seealso::
:meth:`_engine.Connection.execution_options`
:meth:`_engine.Engine.execution_options`
"""
self.dispatch.set_engine_execution_options(self, opt)
self._execution_options = self._execution_options.union(opt)
self.dialect.set_engine_execution_options(self, opt)
@overload
def execution_options(
self,
*,
compiled_cache: Optional[CompiledCacheType] = ...,
logging_token: str = ...,
isolation_level: IsolationLevel = ...,
insertmanyvalues_page_size: int = ...,
schema_translate_map: Optional[SchemaTranslateMapType] = ...,
**opt: Any,
) -> OptionEngine:
...
@overload
def execution_options(self, **opt: Any) -> OptionEngine:
...
def execution_options(self, **opt: Any) -> OptionEngine:
"""Return a new :class:`_engine.Engine` that will provide
:class:`_engine.Connection` objects with the given execution options.
The returned :class:`_engine.Engine` remains related to the original
:class:`_engine.Engine` in that it shares the same connection pool and
other state:
* The :class:`_pool.Pool` used by the new :class:`_engine.Engine`
is the
same instance. The :meth:`_engine.Engine.dispose`
method will replace
the connection pool instance for the parent engine as well
as this one.
* Event listeners are "cascaded" - meaning, the new
:class:`_engine.Engine`
inherits the events of the parent, and new events can be associated
with the new :class:`_engine.Engine` individually.
* The logging configuration and logging_name is copied from the parent
:class:`_engine.Engine`.
The intent of the :meth:`_engine.Engine.execution_options` method is
to implement schemes where multiple :class:`_engine.Engine`
objects refer to the same connection pool, but are differentiated
by options that affect some execution-level behavior for each
engine. One such example is breaking into separate "reader" and
"writer" :class:`_engine.Engine` instances, where one
:class:`_engine.Engine`
has a lower :term:`isolation level` setting configured or is even
transaction-disabled using "autocommit". An example of this
configuration is at :ref:`dbapi_autocommit_multiple`.
Another example is one that
uses a custom option ``shard_id`` which is consumed by an event
to change the current schema on a database connection::
from sqlalchemy import event
from sqlalchemy.engine import Engine
primary_engine = create_engine("mysql+mysqldb://")
shard1 = primary_engine.execution_options(shard_id="shard1")
shard2 = primary_engine.execution_options(shard_id="shard2")
shards = {"default": "base", "shard_1": "db1", "shard_2": "db2"}
@event.listens_for(Engine, "before_cursor_execute")
def _switch_shard(conn, cursor, stmt,
params, context, executemany):
shard_id = conn.get_execution_options().get('shard_id', "default")
current_shard = conn.info.get("current_shard", None)
if current_shard != shard_id:
cursor.execute("use %s" % shards[shard_id])
conn.info["current_shard"] = shard_id
The above recipe illustrates two :class:`_engine.Engine` objects that
will each serve as factories for :class:`_engine.Connection` objects
that have pre-established "shard_id" execution options present. A
:meth:`_events.ConnectionEvents.before_cursor_execute` event handler
then interprets this execution option to emit a MySQL ``use`` statement
to switch databases before a statement execution, while at the same
time keeping track of which database we've established using the
:attr:`_engine.Connection.info` dictionary.
.. seealso::
:meth:`_engine.Connection.execution_options`
- update execution options
on a :class:`_engine.Connection` object.
:meth:`_engine.Engine.update_execution_options`
- update the execution
options for a given :class:`_engine.Engine` in place.
:meth:`_engine.Engine.get_execution_options`
""" # noqa: E501
return self._option_cls(self, opt)
def get_execution_options(self) -> _ExecuteOptions:
"""Get the non-SQL options which will take effect during execution.
.. versionadded: 1.3
.. seealso::
:meth:`_engine.Engine.execution_options`
"""
return self._execution_options
@property
def name(self) -> str:
"""String name of the :class:`~sqlalchemy.engine.interfaces.Dialect`
in use by this :class:`Engine`.
"""
return self.dialect.name
@property
def driver(self) -> str:
"""Driver name of the :class:`~sqlalchemy.engine.interfaces.Dialect`
in use by this :class:`Engine`.
"""
return self.dialect.driver
echo = log.echo_property()
def __repr__(self) -> str:
return "Engine(%r)" % (self.url,)
def dispose(self, close: bool = True) -> None:
"""Dispose of the connection pool used by this
:class:`_engine.Engine`.
A new connection pool is created immediately after the old one has been
disposed. The previous connection pool is disposed either actively, by
closing out all currently checked-in connections in that pool, or
passively, by losing references to it but otherwise not closing any
connections. The latter strategy is more appropriate for an initializer
in a forked Python process.
:param close: if left at its default of ``True``, has the
effect of fully closing all **currently checked in**
database connections. Connections that are still checked out
will **not** be closed, however they will no longer be associated
with this :class:`_engine.Engine`,
so when they are closed individually, eventually the
:class:`_pool.Pool` which they are associated with will
be garbage collected and they will be closed out fully, if
not already closed on checkin.
If set to ``False``, the previous connection pool is de-referenced,
and otherwise not touched in any way.
.. versionadded:: 1.4.33 Added the :paramref:`.Engine.dispose.close`
parameter to allow the replacement of a connection pool in a child
process without interfering with the connections used by the parent
process.
.. seealso::
:ref:`engine_disposal`
:ref:`pooling_multiprocessing`
"""
if close:
self.pool.dispose()
self.pool = self.pool.recreate()
self.dispatch.engine_disposed(self)
@contextlib.contextmanager
def _optional_conn_ctx_manager(
self, connection: Optional[Connection] = None
) -> Iterator[Connection]:
if connection is None:
with self.connect() as conn:
yield conn
else:
yield connection
@contextlib.contextmanager
def begin(self) -> Iterator[Connection]:
"""Return a context manager delivering a :class:`_engine.Connection`
with a :class:`.Transaction` established.
E.g.::
with engine.begin() as conn:
conn.execute(
text("insert into table (x, y, z) values (1, 2, 3)")
)
conn.execute(text("my_special_procedure(5)"))
Upon successful operation, the :class:`.Transaction`
is committed. If an error is raised, the :class:`.Transaction`
is rolled back.
.. seealso::
:meth:`_engine.Engine.connect` - procure a
:class:`_engine.Connection` from
an :class:`_engine.Engine`.
:meth:`_engine.Connection.begin` - start a :class:`.Transaction`
for a particular :class:`_engine.Connection`.
"""
with self.connect() as conn:
with conn.begin():
yield conn
def _run_ddl_visitor(
self,
visitorcallable: Type[Union[SchemaGenerator, SchemaDropper]],
element: SchemaItem,
**kwargs: Any,
) -> None:
with self.begin() as conn:
conn._run_ddl_visitor(visitorcallable, element, **kwargs)
def connect(self) -> Connection:
"""Return a new :class:`_engine.Connection` object.
The :class:`_engine.Connection` acts as a Python context manager, so
the typical use of this method looks like::
with engine.connect() as connection:
connection.execute(text("insert into table values ('foo')"))
connection.commit()
Where above, after the block is completed, the connection is "closed"
and its underlying DBAPI resources are returned to the connection pool.
This also has the effect of rolling back any transaction that
was explicitly begun or was begun via autobegin, and will
emit the :meth:`_events.ConnectionEvents.rollback` event if one was
started and is still in progress.
.. seealso::
:meth:`_engine.Engine.begin`
"""
return self._connection_cls(self)
def raw_connection(self) -> PoolProxiedConnection:
"""Return a "raw" DBAPI connection from the connection pool.
The returned object is a proxied version of the DBAPI
connection object used by the underlying driver in use.
The object will have all the same behavior as the real DBAPI
connection, except that its ``close()`` method will result in the
connection being returned to the pool, rather than being closed
for real.
This method provides direct DBAPI connection access for
special situations when the API provided by
:class:`_engine.Connection`
is not needed. When a :class:`_engine.Connection` object is already
present, the DBAPI connection is available using
the :attr:`_engine.Connection.connection` accessor.
.. seealso::
:ref:`dbapi_connections`
"""
return self.pool.connect()
class OptionEngineMixin(log.Identified):
_sa_propagate_class_events = False
dispatch: dispatcher[ConnectionEventsTarget]
_compiled_cache: Optional[CompiledCacheType]
dialect: Dialect
pool: Pool
url: URL
hide_parameters: bool
echo: log.echo_property
def __init__(
self, proxied: Engine, execution_options: CoreExecuteOptionsParameter
):
self._proxied = proxied
self.url = proxied.url
self.dialect = proxied.dialect
self.logging_name = proxied.logging_name
self.echo = proxied.echo
self._compiled_cache = proxied._compiled_cache
self.hide_parameters = proxied.hide_parameters
log.instance_logger(self, echoflag=self.echo)
# note: this will propagate events that are assigned to the parent
# engine after this OptionEngine is created. Since we share
# the events of the parent we also disallow class-level events
# to apply to the OptionEngine class directly.
#
# the other way this can work would be to transfer existing
# events only, using:
# self.dispatch._update(proxied.dispatch)
#
# that might be more appropriate however it would be a behavioral
# change for logic that assigns events to the parent engine and
# would like it to take effect for the already-created sub-engine.
self.dispatch = self.dispatch._join(proxied.dispatch)
self._execution_options = proxied._execution_options
self.update_execution_options(**execution_options)
def update_execution_options(self, **opt: Any) -> None:
raise NotImplementedError()
if not typing.TYPE_CHECKING:
# https://github.com/python/typing/discussions/1095
@property
def pool(self) -> Pool:
return self._proxied.pool
@pool.setter
def pool(self, pool: Pool) -> None:
self._proxied.pool = pool
@property
def _has_events(self) -> bool:
return self._proxied._has_events or self.__dict__.get(
"_has_events", False
)
@_has_events.setter
def _has_events(self, value: bool) -> None:
self.__dict__["_has_events"] = value
class OptionEngine(OptionEngineMixin, Engine):
def update_execution_options(self, **opt: Any) -> None:
Engine.update_execution_options(self, **opt)
Engine._option_cls = OptionEngine
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