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1# engine/create.py
2# Copyright (C) 2005-2025 the SQLAlchemy authors and contributors
3# <see AUTHORS file>
4#
5# This module is part of SQLAlchemy and is released under
6# the MIT License: https://www.opensource.org/licenses/mit-license.php
8from __future__ import annotations
10import inspect
11import typing
12from typing import Any
13from typing import Callable
14from typing import cast
15from typing import Dict
16from typing import List
17from typing import Optional
18from typing import overload
19from typing import Type
20from typing import Union
22from . import base
23from . import url as _url
24from .interfaces import DBAPIConnection
25from .mock import create_mock_engine
26from .. import event
27from .. import exc
28from .. import util
29from ..pool import _AdhocProxiedConnection
30from ..pool import ConnectionPoolEntry
31from ..sql import compiler
32from ..util import immutabledict
34if typing.TYPE_CHECKING:
35 from .base import Engine
36 from .interfaces import _ExecuteOptions
37 from .interfaces import _ParamStyle
38 from .interfaces import IsolationLevel
39 from .url import URL
40 from ..log import _EchoFlagType
41 from ..pool import _CreatorFnType
42 from ..pool import _CreatorWRecFnType
43 from ..pool import _ResetStyleArgType
44 from ..pool import Pool
45 from ..util.typing import Literal
48@overload
49def create_engine(
50 url: Union[str, URL],
51 *,
52 connect_args: Dict[Any, Any] = ...,
53 convert_unicode: bool = ...,
54 creator: Union[_CreatorFnType, _CreatorWRecFnType] = ...,
55 echo: _EchoFlagType = ...,
56 echo_pool: _EchoFlagType = ...,
57 enable_from_linting: bool = ...,
58 execution_options: _ExecuteOptions = ...,
59 future: Literal[True],
60 hide_parameters: bool = ...,
61 implicit_returning: Literal[True] = ...,
62 insertmanyvalues_page_size: int = ...,
63 isolation_level: IsolationLevel = ...,
64 json_deserializer: Callable[..., Any] = ...,
65 json_serializer: Callable[..., Any] = ...,
66 label_length: Optional[int] = ...,
67 logging_name: str = ...,
68 max_identifier_length: Optional[int] = ...,
69 max_overflow: int = ...,
70 module: Optional[Any] = ...,
71 paramstyle: Optional[_ParamStyle] = ...,
72 pool: Optional[Pool] = ...,
73 poolclass: Optional[Type[Pool]] = ...,
74 pool_logging_name: str = ...,
75 pool_pre_ping: bool = ...,
76 pool_size: int = ...,
77 pool_recycle: int = ...,
78 pool_reset_on_return: Optional[_ResetStyleArgType] = ...,
79 pool_timeout: float = ...,
80 pool_use_lifo: bool = ...,
81 plugins: List[str] = ...,
82 query_cache_size: int = ...,
83 use_insertmanyvalues: bool = ...,
84 **kwargs: Any,
85) -> Engine: ...
88@overload
89def create_engine(url: Union[str, URL], **kwargs: Any) -> Engine: ...
92@util.deprecated_params(
93 strategy=(
94 "1.4",
95 "The :paramref:`_sa.create_engine.strategy` keyword is deprecated, "
96 "and the only argument accepted is 'mock'; please use "
97 ":func:`.create_mock_engine` going forward. For general "
98 "customization of create_engine which may have been accomplished "
99 "using strategies, see :class:`.CreateEnginePlugin`.",
100 ),
101 empty_in_strategy=(
102 "1.4",
103 "The :paramref:`_sa.create_engine.empty_in_strategy` keyword is "
104 "deprecated, and no longer has any effect. All IN expressions "
105 "are now rendered using "
106 'the "expanding parameter" strategy which renders a set of bound'
107 'expressions, or an "empty set" SELECT, at statement execution'
108 "time.",
109 ),
110 implicit_returning=(
111 "2.0",
112 "The :paramref:`_sa.create_engine.implicit_returning` parameter "
113 "is deprecated and will be removed in a future release. ",
114 ),
115)
116def create_engine(url: Union[str, _url.URL], **kwargs: Any) -> Engine:
117 """Create a new :class:`_engine.Engine` instance.
119 The standard calling form is to send the :ref:`URL <database_urls>` as the
120 first positional argument, usually a string
121 that indicates database dialect and connection arguments::
123 engine = create_engine("postgresql+psycopg2://scott:tiger@localhost/test")
125 .. note::
127 Please review :ref:`database_urls` for general guidelines in composing
128 URL strings. In particular, special characters, such as those often
129 part of passwords, must be URL encoded to be properly parsed.
131 Additional keyword arguments may then follow it which
132 establish various options on the resulting :class:`_engine.Engine`
133 and its underlying :class:`.Dialect` and :class:`_pool.Pool`
134 constructs::
136 engine = create_engine(
137 "mysql+mysqldb://scott:tiger@hostname/dbname",
138 pool_recycle=3600,
139 echo=True,
140 )
142 The string form of the URL is
143 ``dialect[+driver]://user:password@host/dbname[?key=value..]``, where
144 ``dialect`` is a database name such as ``mysql``, ``oracle``,
145 ``postgresql``, etc., and ``driver`` the name of a DBAPI, such as
146 ``psycopg2``, ``pyodbc``, ``cx_oracle``, etc. Alternatively,
147 the URL can be an instance of :class:`~sqlalchemy.engine.url.URL`.
149 ``**kwargs`` takes a wide variety of options which are routed
150 towards their appropriate components. Arguments may be specific to
151 the :class:`_engine.Engine`, the underlying :class:`.Dialect`,
152 as well as the
153 :class:`_pool.Pool`. Specific dialects also accept keyword arguments that
154 are unique to that dialect. Here, we describe the parameters
155 that are common to most :func:`_sa.create_engine()` usage.
157 Once established, the newly resulting :class:`_engine.Engine` will
158 request a connection from the underlying :class:`_pool.Pool` once
159 :meth:`_engine.Engine.connect` is called, or a method which depends on it
160 such as :meth:`_engine.Engine.execute` is invoked. The
161 :class:`_pool.Pool` in turn
162 will establish the first actual DBAPI connection when this request
163 is received. The :func:`_sa.create_engine` call itself does **not**
164 establish any actual DBAPI connections directly.
166 .. seealso::
168 :doc:`/core/engines`
170 :doc:`/dialects/index`
172 :ref:`connections_toplevel`
174 :param connect_args: a dictionary of options which will be
175 passed directly to the DBAPI's ``connect()`` method as
176 additional keyword arguments. See the example
177 at :ref:`custom_dbapi_args`.
179 :param creator: a callable which returns a DBAPI connection.
180 This creation function will be passed to the underlying
181 connection pool and will be used to create all new database
182 connections. Usage of this function causes connection
183 parameters specified in the URL argument to be bypassed.
185 This hook is not as flexible as the newer
186 :meth:`_events.DialectEvents.do_connect` hook which allows complete
187 control over how a connection is made to the database, given the full
188 set of URL arguments and state beforehand.
190 .. seealso::
192 :meth:`_events.DialectEvents.do_connect` - event hook that allows
193 full control over DBAPI connection mechanics.
195 :ref:`custom_dbapi_args`
197 :param echo=False: if True, the Engine will log all statements
198 as well as a ``repr()`` of their parameter lists to the default log
199 handler, which defaults to ``sys.stdout`` for output. If set to the
200 string ``"debug"``, result rows will be printed to the standard output
201 as well. The ``echo`` attribute of ``Engine`` can be modified at any
202 time to turn logging on and off; direct control of logging is also
203 available using the standard Python ``logging`` module.
205 .. seealso::
207 :ref:`dbengine_logging` - further detail on how to configure
208 logging.
211 :param echo_pool=False: if True, the connection pool will log
212 informational output such as when connections are invalidated
213 as well as when connections are recycled to the default log handler,
214 which defaults to ``sys.stdout`` for output. If set to the string
215 ``"debug"``, the logging will include pool checkouts and checkins.
216 Direct control of logging is also available using the standard Python
217 ``logging`` module.
219 .. seealso::
221 :ref:`dbengine_logging` - further detail on how to configure
222 logging.
225 :param empty_in_strategy: No longer used; SQLAlchemy now uses
226 "empty set" behavior for IN in all cases.
228 :param enable_from_linting: defaults to True. Will emit a warning
229 if a given SELECT statement is found to have un-linked FROM elements
230 which would cause a cartesian product.
232 .. versionadded:: 1.4
234 .. seealso::
236 :ref:`change_4737`
238 :param execution_options: Dictionary execution options which will
239 be applied to all connections. See
240 :meth:`~sqlalchemy.engine.Connection.execution_options`
242 :param future: Use the 2.0 style :class:`_engine.Engine` and
243 :class:`_engine.Connection` API.
245 As of SQLAlchemy 2.0, this parameter is present for backwards
246 compatibility only and must remain at its default value of ``True``.
248 The :paramref:`_sa.create_engine.future` parameter will be
249 deprecated in a subsequent 2.x release and eventually removed.
251 .. versionadded:: 1.4
253 .. versionchanged:: 2.0 All :class:`_engine.Engine` objects are
254 "future" style engines and there is no longer a ``future=False``
255 mode of operation.
257 .. seealso::
259 :ref:`migration_20_toplevel`
261 :param hide_parameters: Boolean, when set to True, SQL statement parameters
262 will not be displayed in INFO logging nor will they be formatted into
263 the string representation of :class:`.StatementError` objects.
265 .. versionadded:: 1.3.8
267 .. seealso::
269 :ref:`dbengine_logging` - further detail on how to configure
270 logging.
272 :param implicit_returning=True: Legacy parameter that may only be set
273 to True. In SQLAlchemy 2.0, this parameter does nothing. In order to
274 disable "implicit returning" for statements invoked by the ORM,
275 configure this on a per-table basis using the
276 :paramref:`.Table.implicit_returning` parameter.
279 :param insertmanyvalues_page_size: number of rows to format into an
280 INSERT statement when the statement uses "insertmanyvalues" mode, which is
281 a paged form of bulk insert that is used for many backends when using
282 :term:`executemany` execution typically in conjunction with RETURNING.
283 Defaults to 1000, but may also be subject to dialect-specific limiting
284 factors which may override this value on a per-statement basis.
286 .. versionadded:: 2.0
288 .. seealso::
290 :ref:`engine_insertmanyvalues`
292 :ref:`engine_insertmanyvalues_page_size`
294 :paramref:`_engine.Connection.execution_options.insertmanyvalues_page_size`
296 :param isolation_level: optional string name of an isolation level
297 which will be set on all new connections unconditionally.
298 Isolation levels are typically some subset of the string names
299 ``"SERIALIZABLE"``, ``"REPEATABLE READ"``,
300 ``"READ COMMITTED"``, ``"READ UNCOMMITTED"`` and ``"AUTOCOMMIT"``
301 based on backend.
303 The :paramref:`_sa.create_engine.isolation_level` parameter is
304 in contrast to the
305 :paramref:`.Connection.execution_options.isolation_level`
306 execution option, which may be set on an individual
307 :class:`.Connection`, as well as the same parameter passed to
308 :meth:`.Engine.execution_options`, where it may be used to create
309 multiple engines with different isolation levels that share a common
310 connection pool and dialect.
312 .. versionchanged:: 2.0 The
313 :paramref:`_sa.create_engine.isolation_level`
314 parameter has been generalized to work on all dialects which support
315 the concept of isolation level, and is provided as a more succinct,
316 up front configuration switch in contrast to the execution option
317 which is more of an ad-hoc programmatic option.
319 .. seealso::
321 :ref:`dbapi_autocommit`
323 :param json_deserializer: for dialects that support the
324 :class:`_types.JSON`
325 datatype, this is a Python callable that will convert a JSON string
326 to a Python object. By default, the Python ``json.loads`` function is
327 used.
329 .. versionchanged:: 1.3.7 The SQLite dialect renamed this from
330 ``_json_deserializer``.
332 :param json_serializer: for dialects that support the :class:`_types.JSON`
333 datatype, this is a Python callable that will render a given object
334 as JSON. By default, the Python ``json.dumps`` function is used.
336 .. versionchanged:: 1.3.7 The SQLite dialect renamed this from
337 ``_json_serializer``.
340 :param label_length=None: optional integer value which limits
341 the size of dynamically generated column labels to that many
342 characters. If less than 6, labels are generated as
343 "_(counter)". If ``None``, the value of
344 ``dialect.max_identifier_length``, which may be affected via the
345 :paramref:`_sa.create_engine.max_identifier_length` parameter,
346 is used instead. The value of
347 :paramref:`_sa.create_engine.label_length`
348 may not be larger than that of
349 :paramref:`_sa.create_engine.max_identfier_length`.
351 .. seealso::
353 :paramref:`_sa.create_engine.max_identifier_length`
355 :param logging_name: String identifier which will be used within
356 the "name" field of logging records generated within the
357 "sqlalchemy.engine" logger. Defaults to a hexstring of the
358 object's id.
360 .. seealso::
362 :ref:`dbengine_logging` - further detail on how to configure
363 logging.
365 :paramref:`_engine.Connection.execution_options.logging_token`
367 :param max_identifier_length: integer; override the max_identifier_length
368 determined by the dialect. if ``None`` or zero, has no effect. This
369 is the database's configured maximum number of characters that may be
370 used in a SQL identifier such as a table name, column name, or label
371 name. All dialects determine this value automatically, however in the
372 case of a new database version for which this value has changed but
373 SQLAlchemy's dialect has not been adjusted, the value may be passed
374 here.
376 .. versionadded:: 1.3.9
378 .. seealso::
380 :paramref:`_sa.create_engine.label_length`
382 :param max_overflow=10: the number of connections to allow in
383 connection pool "overflow", that is connections that can be
384 opened above and beyond the pool_size setting, which defaults
385 to five. this is only used with :class:`~sqlalchemy.pool.QueuePool`.
387 :param module=None: reference to a Python module object (the module
388 itself, not its string name). Specifies an alternate DBAPI module to
389 be used by the engine's dialect. Each sub-dialect references a
390 specific DBAPI which will be imported before first connect. This
391 parameter causes the import to be bypassed, and the given module to
392 be used instead. Can be used for testing of DBAPIs as well as to
393 inject "mock" DBAPI implementations into the :class:`_engine.Engine`.
395 :param paramstyle=None: The `paramstyle <https://legacy.python.org/dev/peps/pep-0249/#paramstyle>`_
396 to use when rendering bound parameters. This style defaults to the
397 one recommended by the DBAPI itself, which is retrieved from the
398 ``.paramstyle`` attribute of the DBAPI. However, most DBAPIs accept
399 more than one paramstyle, and in particular it may be desirable
400 to change a "named" paramstyle into a "positional" one, or vice versa.
401 When this attribute is passed, it should be one of the values
402 ``"qmark"``, ``"numeric"``, ``"named"``, ``"format"`` or
403 ``"pyformat"``, and should correspond to a parameter style known
404 to be supported by the DBAPI in use.
406 :param pool=None: an already-constructed instance of
407 :class:`~sqlalchemy.pool.Pool`, such as a
408 :class:`~sqlalchemy.pool.QueuePool` instance. If non-None, this
409 pool will be used directly as the underlying connection pool
410 for the engine, bypassing whatever connection parameters are
411 present in the URL argument. For information on constructing
412 connection pools manually, see :ref:`pooling_toplevel`.
414 :param poolclass=None: a :class:`~sqlalchemy.pool.Pool`
415 subclass, which will be used to create a connection pool
416 instance using the connection parameters given in the URL. Note
417 this differs from ``pool`` in that you don't actually
418 instantiate the pool in this case, you just indicate what type
419 of pool to be used.
421 :param pool_logging_name: String identifier which will be used within
422 the "name" field of logging records generated within the
423 "sqlalchemy.pool" logger. Defaults to a hexstring of the object's
424 id.
426 .. seealso::
428 :ref:`dbengine_logging` - further detail on how to configure
429 logging.
431 :param pool_pre_ping: boolean, if True will enable the connection pool
432 "pre-ping" feature that tests connections for liveness upon
433 each checkout.
435 .. versionadded:: 1.2
437 .. seealso::
439 :ref:`pool_disconnects_pessimistic`
441 :param pool_size=5: the number of connections to keep open
442 inside the connection pool. This used with
443 :class:`~sqlalchemy.pool.QueuePool` as
444 well as :class:`~sqlalchemy.pool.SingletonThreadPool`. With
445 :class:`~sqlalchemy.pool.QueuePool`, a ``pool_size`` setting
446 of 0 indicates no limit; to disable pooling, set ``poolclass`` to
447 :class:`~sqlalchemy.pool.NullPool` instead.
449 :param pool_recycle=-1: this setting causes the pool to recycle
450 connections after the given number of seconds has passed. It
451 defaults to -1, or no timeout. For example, setting to 3600
452 means connections will be recycled after one hour. Note that
453 MySQL in particular will disconnect automatically if no
454 activity is detected on a connection for eight hours (although
455 this is configurable with the MySQLDB connection itself and the
456 server configuration as well).
458 .. seealso::
460 :ref:`pool_setting_recycle`
462 :param pool_reset_on_return='rollback': set the
463 :paramref:`_pool.Pool.reset_on_return` parameter of the underlying
464 :class:`_pool.Pool` object, which can be set to the values
465 ``"rollback"``, ``"commit"``, or ``None``.
467 .. seealso::
469 :ref:`pool_reset_on_return`
471 :param pool_timeout=30: number of seconds to wait before giving
472 up on getting a connection from the pool. This is only used
473 with :class:`~sqlalchemy.pool.QueuePool`. This can be a float but is
474 subject to the limitations of Python time functions which may not be
475 reliable in the tens of milliseconds.
477 .. note: don't use 30.0 above, it seems to break with the :param tag
479 :param pool_use_lifo=False: use LIFO (last-in-first-out) when retrieving
480 connections from :class:`.QueuePool` instead of FIFO
481 (first-in-first-out). Using LIFO, a server-side timeout scheme can
482 reduce the number of connections used during non- peak periods of
483 use. When planning for server-side timeouts, ensure that a recycle or
484 pre-ping strategy is in use to gracefully handle stale connections.
486 .. versionadded:: 1.3
488 .. seealso::
490 :ref:`pool_use_lifo`
492 :ref:`pool_disconnects`
494 :param plugins: string list of plugin names to load. See
495 :class:`.CreateEnginePlugin` for background.
497 .. versionadded:: 1.2.3
499 :param query_cache_size: size of the cache used to cache the SQL string
500 form of queries. Set to zero to disable caching.
502 The cache is pruned of its least recently used items when its size reaches
503 N * 1.5. Defaults to 500, meaning the cache will always store at least
504 500 SQL statements when filled, and will grow up to 750 items at which
505 point it is pruned back down to 500 by removing the 250 least recently
506 used items.
508 Caching is accomplished on a per-statement basis by generating a
509 cache key that represents the statement's structure, then generating
510 string SQL for the current dialect only if that key is not present
511 in the cache. All statements support caching, however some features
512 such as an INSERT with a large set of parameters will intentionally
513 bypass the cache. SQL logging will indicate statistics for each
514 statement whether or not it were pull from the cache.
516 .. note:: some ORM functions related to unit-of-work persistence as well
517 as some attribute loading strategies will make use of individual
518 per-mapper caches outside of the main cache.
521 .. seealso::
523 :ref:`sql_caching`
525 .. versionadded:: 1.4
527 :param use_insertmanyvalues: True by default, use the "insertmanyvalues"
528 execution style for INSERT..RETURNING statements by default.
530 .. versionadded:: 2.0
532 .. seealso::
534 :ref:`engine_insertmanyvalues`
536 """ # noqa
538 if "strategy" in kwargs:
539 strat = kwargs.pop("strategy")
540 if strat == "mock":
541 # this case is deprecated
542 return create_mock_engine(url, **kwargs) # type: ignore
543 else:
544 raise exc.ArgumentError("unknown strategy: %r" % strat)
546 kwargs.pop("empty_in_strategy", None)
548 # create url.URL object
549 u = _url.make_url(url)
551 u, plugins, kwargs = u._instantiate_plugins(kwargs)
553 entrypoint = u._get_entrypoint()
554 _is_async = kwargs.pop("_is_async", False)
555 if _is_async:
556 dialect_cls = entrypoint.get_async_dialect_cls(u)
557 else:
558 dialect_cls = entrypoint.get_dialect_cls(u)
560 if kwargs.pop("_coerce_config", False):
562 def pop_kwarg(key: str, default: Optional[Any] = None) -> Any:
563 value = kwargs.pop(key, default)
564 if key in dialect_cls.engine_config_types:
565 value = dialect_cls.engine_config_types[key](value)
566 return value
568 else:
569 pop_kwarg = kwargs.pop # type: ignore
571 dialect_args = {}
572 # consume dialect arguments from kwargs
573 for k in util.get_cls_kwargs(dialect_cls):
574 if k in kwargs:
575 dialect_args[k] = pop_kwarg(k)
577 dbapi = kwargs.pop("module", None)
578 if dbapi is None:
579 dbapi_args = {}
581 if "import_dbapi" in dialect_cls.__dict__:
582 dbapi_meth = dialect_cls.import_dbapi
584 elif hasattr(dialect_cls, "dbapi") and inspect.ismethod(
585 dialect_cls.dbapi
586 ):
587 util.warn_deprecated(
588 "The dbapi() classmethod on dialect classes has been "
589 "renamed to import_dbapi(). Implement an import_dbapi() "
590 f"classmethod directly on class {dialect_cls} to remove this "
591 "warning; the old .dbapi() classmethod may be maintained for "
592 "backwards compatibility.",
593 "2.0",
594 )
595 dbapi_meth = dialect_cls.dbapi
596 else:
597 dbapi_meth = dialect_cls.import_dbapi
599 for k in util.get_func_kwargs(dbapi_meth):
600 if k in kwargs:
601 dbapi_args[k] = pop_kwarg(k)
602 dbapi = dbapi_meth(**dbapi_args)
604 dialect_args["dbapi"] = dbapi
606 dialect_args.setdefault("compiler_linting", compiler.NO_LINTING)
607 enable_from_linting = kwargs.pop("enable_from_linting", True)
608 if enable_from_linting:
609 dialect_args["compiler_linting"] ^= compiler.COLLECT_CARTESIAN_PRODUCTS
611 for plugin in plugins:
612 plugin.handle_dialect_kwargs(dialect_cls, dialect_args)
614 # create dialect
615 dialect = dialect_cls(**dialect_args)
617 # assemble connection arguments
618 (cargs_tup, cparams) = dialect.create_connect_args(u)
619 cparams.update(pop_kwarg("connect_args", {}))
621 if "async_fallback" in cparams and util.asbool(cparams["async_fallback"]):
622 util.warn_deprecated(
623 "The async_fallback dialect argument is deprecated and will be "
624 "removed in SQLAlchemy 2.1.",
625 "2.0",
626 )
628 cargs = list(cargs_tup) # allow mutability
630 # look for existing pool or create
631 pool = pop_kwarg("pool", None)
632 if pool is None:
634 def connect(
635 connection_record: Optional[ConnectionPoolEntry] = None,
636 ) -> DBAPIConnection:
637 if dialect._has_events:
638 for fn in dialect.dispatch.do_connect:
639 connection = cast(
640 DBAPIConnection,
641 fn(dialect, connection_record, cargs, cparams),
642 )
643 if connection is not None:
644 return connection
646 return dialect.connect(*cargs, **cparams)
648 creator = pop_kwarg("creator", connect)
650 poolclass = pop_kwarg("poolclass", None)
651 if poolclass is None:
652 poolclass = dialect.get_dialect_pool_class(u)
653 pool_args = {"dialect": dialect}
655 # consume pool arguments from kwargs, translating a few of
656 # the arguments
657 for k in util.get_cls_kwargs(poolclass):
658 tk = _pool_translate_kwargs.get(k, k)
659 if tk in kwargs:
660 pool_args[k] = pop_kwarg(tk)
662 for plugin in plugins:
663 plugin.handle_pool_kwargs(poolclass, pool_args)
665 pool = poolclass(creator, **pool_args)
666 else:
667 pool._dialect = dialect
669 if (
670 hasattr(pool, "_is_asyncio")
671 and pool._is_asyncio is not dialect.is_async
672 ):
673 raise exc.ArgumentError(
674 f"Pool class {pool.__class__.__name__} cannot be "
675 f"used with {'non-' if not dialect.is_async else ''}"
676 "asyncio engine",
677 code="pcls",
678 )
680 # create engine.
681 if not pop_kwarg("future", True):
682 raise exc.ArgumentError(
683 "The 'future' parameter passed to "
684 "create_engine() may only be set to True."
685 )
687 engineclass = base.Engine
689 engine_args = {}
690 for k in util.get_cls_kwargs(engineclass):
691 if k in kwargs:
692 engine_args[k] = pop_kwarg(k)
694 # internal flags used by the test suite for instrumenting / proxying
695 # engines with mocks etc.
696 _initialize = kwargs.pop("_initialize", True)
698 # all kwargs should be consumed
699 if kwargs:
700 raise TypeError(
701 "Invalid argument(s) %s sent to create_engine(), "
702 "using configuration %s/%s/%s. Please check that the "
703 "keyword arguments are appropriate for this combination "
704 "of components."
705 % (
706 ",".join("'%s'" % k for k in kwargs),
707 dialect.__class__.__name__,
708 pool.__class__.__name__,
709 engineclass.__name__,
710 )
711 )
713 engine = engineclass(pool, dialect, u, **engine_args)
715 if _initialize:
716 do_on_connect = dialect.on_connect_url(u)
717 if do_on_connect:
719 def on_connect(
720 dbapi_connection: DBAPIConnection,
721 connection_record: ConnectionPoolEntry,
722 ) -> None:
723 assert do_on_connect is not None
724 do_on_connect(dbapi_connection)
726 event.listen(pool, "connect", on_connect)
728 builtin_on_connect = dialect._builtin_onconnect()
729 if builtin_on_connect:
730 event.listen(pool, "connect", builtin_on_connect)
732 def first_connect(
733 dbapi_connection: DBAPIConnection,
734 connection_record: ConnectionPoolEntry,
735 ) -> None:
736 c = base.Connection(
737 engine,
738 connection=_AdhocProxiedConnection(
739 dbapi_connection, connection_record
740 ),
741 _has_events=False,
742 # reconnecting will be a reentrant condition, so if the
743 # connection goes away, Connection is then closed
744 _allow_revalidate=False,
745 # dont trigger the autobegin sequence
746 # within the up front dialect checks
747 _allow_autobegin=False,
748 )
749 c._execution_options = util.EMPTY_DICT
751 try:
752 dialect.initialize(c)
753 finally:
754 # note that "invalidated" and "closed" are mutually
755 # exclusive in 1.4 Connection.
756 if not c.invalidated and not c.closed:
757 # transaction is rolled back otherwise, tested by
758 # test/dialect/postgresql/test_dialect.py
759 # ::MiscBackendTest::test_initial_transaction_state
760 dialect.do_rollback(c.connection)
762 # previously, the "first_connect" event was used here, which was then
763 # scaled back if the "on_connect" handler were present. now,
764 # since "on_connect" is virtually always present, just use
765 # "connect" event with once_unless_exception in all cases so that
766 # the connection event flow is consistent in all cases.
767 event.listen(
768 pool, "connect", first_connect, _once_unless_exception=True
769 )
771 dialect_cls.engine_created(engine)
772 if entrypoint is not dialect_cls:
773 entrypoint.engine_created(engine)
775 for plugin in plugins:
776 plugin.engine_created(engine)
778 return engine
781def engine_from_config(
782 configuration: Dict[str, Any], prefix: str = "sqlalchemy.", **kwargs: Any
783) -> Engine:
784 """Create a new Engine instance using a configuration dictionary.
786 The dictionary is typically produced from a config file.
788 The keys of interest to ``engine_from_config()`` should be prefixed, e.g.
789 ``sqlalchemy.url``, ``sqlalchemy.echo``, etc. The 'prefix' argument
790 indicates the prefix to be searched for. Each matching key (after the
791 prefix is stripped) is treated as though it were the corresponding keyword
792 argument to a :func:`_sa.create_engine` call.
794 The only required key is (assuming the default prefix) ``sqlalchemy.url``,
795 which provides the :ref:`database URL <database_urls>`.
797 A select set of keyword arguments will be "coerced" to their
798 expected type based on string values. The set of arguments
799 is extensible per-dialect using the ``engine_config_types`` accessor.
801 :param configuration: A dictionary (typically produced from a config file,
802 but this is not a requirement). Items whose keys start with the value
803 of 'prefix' will have that prefix stripped, and will then be passed to
804 :func:`_sa.create_engine`.
806 :param prefix: Prefix to match and then strip from keys
807 in 'configuration'.
809 :param kwargs: Each keyword argument to ``engine_from_config()`` itself
810 overrides the corresponding item taken from the 'configuration'
811 dictionary. Keyword arguments should *not* be prefixed.
813 """
815 options = {
816 key[len(prefix) :]: configuration[key]
817 for key in configuration
818 if key.startswith(prefix)
819 }
820 options["_coerce_config"] = True
821 options.update(kwargs)
822 url = options.pop("url")
823 return create_engine(url, **options)
826@overload
827def create_pool_from_url(
828 url: Union[str, URL],
829 *,
830 poolclass: Optional[Type[Pool]] = ...,
831 logging_name: str = ...,
832 pre_ping: bool = ...,
833 size: int = ...,
834 recycle: int = ...,
835 reset_on_return: Optional[_ResetStyleArgType] = ...,
836 timeout: float = ...,
837 use_lifo: bool = ...,
838 **kwargs: Any,
839) -> Pool: ...
842@overload
843def create_pool_from_url(url: Union[str, URL], **kwargs: Any) -> Pool: ...
846def create_pool_from_url(url: Union[str, URL], **kwargs: Any) -> Pool:
847 """Create a pool instance from the given url.
849 If ``poolclass`` is not provided the pool class used
850 is selected using the dialect specified in the URL.
852 The arguments passed to :func:`_sa.create_pool_from_url` are
853 identical to the pool argument passed to the :func:`_sa.create_engine`
854 function.
856 .. versionadded:: 2.0.10
857 """
859 for key in _pool_translate_kwargs:
860 if key in kwargs:
861 kwargs[_pool_translate_kwargs[key]] = kwargs.pop(key)
863 engine = create_engine(url, **kwargs, _initialize=False)
864 return engine.pool
867_pool_translate_kwargs = immutabledict(
868 {
869 "logging_name": "pool_logging_name",
870 "echo": "echo_pool",
871 "timeout": "pool_timeout",
872 "recycle": "pool_recycle",
873 "events": "pool_events", # deprecated
874 "reset_on_return": "pool_reset_on_return",
875 "pre_ping": "pool_pre_ping",
876 "use_lifo": "pool_use_lifo",
877 }
878)