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1# engine/interfaces.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
8"""Define core interfaces used by the engine system."""
10from __future__ import annotations
12from enum import Enum
13from typing import Any
14from typing import Awaitable
15from typing import Callable
16from typing import ClassVar
17from typing import Collection
18from typing import Dict
19from typing import Iterable
20from typing import Iterator
21from typing import List
22from typing import Mapping
23from typing import MutableMapping
24from typing import Optional
25from typing import Sequence
26from typing import Set
27from typing import Tuple
28from typing import Type
29from typing import TYPE_CHECKING
30from typing import TypeVar
31from typing import Union
33from .. import util
34from ..event import EventTarget
35from ..pool import Pool
36from ..pool import PoolProxiedConnection as PoolProxiedConnection
37from ..sql.compiler import Compiled as Compiled
38from ..sql.compiler import Compiled # noqa
39from ..sql.compiler import TypeCompiler as TypeCompiler
40from ..sql.compiler import TypeCompiler # noqa
41from ..util import immutabledict
42from ..util.concurrency import await_only
43from ..util.typing import Literal
44from ..util.typing import NotRequired
45from ..util.typing import Protocol
46from ..util.typing import TypedDict
48if TYPE_CHECKING:
49 from .base import Connection
50 from .base import Engine
51 from .cursor import CursorResult
52 from .url import URL
53 from ..connectors.asyncio import AsyncIODBAPIConnection
54 from ..event import _ListenerFnType
55 from ..event import dispatcher
56 from ..exc import StatementError
57 from ..sql import Executable
58 from ..sql.compiler import _InsertManyValuesBatch
59 from ..sql.compiler import DDLCompiler
60 from ..sql.compiler import IdentifierPreparer
61 from ..sql.compiler import InsertmanyvaluesSentinelOpts
62 from ..sql.compiler import Linting
63 from ..sql.compiler import SQLCompiler
64 from ..sql.elements import BindParameter
65 from ..sql.elements import ClauseElement
66 from ..sql.schema import Column
67 from ..sql.schema import DefaultGenerator
68 from ..sql.schema import SchemaItem
69 from ..sql.schema import Sequence as Sequence_SchemaItem
70 from ..sql.sqltypes import Integer
71 from ..sql.type_api import _TypeMemoDict
72 from ..sql.type_api import TypeEngine
73 from ..util.langhelpers import generic_fn_descriptor
75ConnectArgsType = Tuple[Sequence[str], MutableMapping[str, Any]]
77_T = TypeVar("_T", bound="Any")
80class CacheStats(Enum):
81 CACHE_HIT = 0
82 CACHE_MISS = 1
83 CACHING_DISABLED = 2
84 NO_CACHE_KEY = 3
85 NO_DIALECT_SUPPORT = 4
88class ExecuteStyle(Enum):
89 """indicates the :term:`DBAPI` cursor method that will be used to invoke
90 a statement."""
92 EXECUTE = 0
93 """indicates cursor.execute() will be used"""
95 EXECUTEMANY = 1
96 """indicates cursor.executemany() will be used."""
98 INSERTMANYVALUES = 2
99 """indicates cursor.execute() will be used with an INSERT where the
100 VALUES expression will be expanded to accommodate for multiple
101 parameter sets
103 .. seealso::
105 :ref:`engine_insertmanyvalues`
107 """
110class DBAPIModule(Protocol):
111 class Error(Exception):
112 def __getattr__(self, key: str) -> Any: ...
114 class OperationalError(Error):
115 pass
117 class InterfaceError(Error):
118 pass
120 class IntegrityError(Error):
121 pass
123 def __getattr__(self, key: str) -> Any: ...
126class DBAPIConnection(Protocol):
127 """protocol representing a :pep:`249` database connection.
129 .. versionadded:: 2.0
131 .. seealso::
133 `Connection Objects <https://www.python.org/dev/peps/pep-0249/#connection-objects>`_
134 - in :pep:`249`
136 """ # noqa: E501
138 def close(self) -> None: ...
140 def commit(self) -> None: ...
142 def cursor(self, *args: Any, **kwargs: Any) -> DBAPICursor: ...
144 def rollback(self) -> None: ...
146 def __getattr__(self, key: str) -> Any: ...
148 def __setattr__(self, key: str, value: Any) -> None: ...
151class DBAPIType(Protocol):
152 """protocol representing a :pep:`249` database type.
154 .. versionadded:: 2.0
156 .. seealso::
158 `Type Objects <https://www.python.org/dev/peps/pep-0249/#type-objects>`_
159 - in :pep:`249`
161 """ # noqa: E501
164class DBAPICursor(Protocol):
165 """protocol representing a :pep:`249` database cursor.
167 .. versionadded:: 2.0
169 .. seealso::
171 `Cursor Objects <https://www.python.org/dev/peps/pep-0249/#cursor-objects>`_
172 - in :pep:`249`
174 """ # noqa: E501
176 @property
177 def description(
178 self,
179 ) -> _DBAPICursorDescription:
180 """The description attribute of the Cursor.
182 .. seealso::
184 `cursor.description <https://www.python.org/dev/peps/pep-0249/#description>`_
185 - in :pep:`249`
188 """ # noqa: E501
189 ...
191 @property
192 def rowcount(self) -> int: ...
194 arraysize: int
196 lastrowid: int
198 def close(self) -> None: ...
200 def execute(
201 self,
202 operation: Any,
203 parameters: Optional[_DBAPISingleExecuteParams] = None,
204 ) -> Any: ...
206 def executemany(
207 self,
208 operation: Any,
209 parameters: _DBAPIMultiExecuteParams,
210 ) -> Any: ...
212 def fetchone(self) -> Optional[Any]: ...
214 def fetchmany(self, size: int = ...) -> Sequence[Any]: ...
216 def fetchall(self) -> Sequence[Any]: ...
218 def setinputsizes(self, sizes: Sequence[Any]) -> None: ...
220 def setoutputsize(self, size: Any, column: Any) -> None: ...
222 def callproc(
223 self, procname: str, parameters: Sequence[Any] = ...
224 ) -> Any: ...
226 def nextset(self) -> Optional[bool]: ...
228 def __getattr__(self, key: str) -> Any: ...
231_CoreSingleExecuteParams = Mapping[str, Any]
232_MutableCoreSingleExecuteParams = MutableMapping[str, Any]
233_CoreMultiExecuteParams = Sequence[_CoreSingleExecuteParams]
234_CoreAnyExecuteParams = Union[
235 _CoreMultiExecuteParams, _CoreSingleExecuteParams
236]
238_DBAPISingleExecuteParams = Union[Sequence[Any], _CoreSingleExecuteParams]
240_DBAPIMultiExecuteParams = Union[
241 Sequence[Sequence[Any]], _CoreMultiExecuteParams
242]
243_DBAPIAnyExecuteParams = Union[
244 _DBAPIMultiExecuteParams, _DBAPISingleExecuteParams
245]
246_DBAPICursorDescription = Sequence[
247 Tuple[
248 str,
249 "DBAPIType",
250 Optional[int],
251 Optional[int],
252 Optional[int],
253 Optional[int],
254 Optional[bool],
255 ]
256]
258_AnySingleExecuteParams = _DBAPISingleExecuteParams
259_AnyMultiExecuteParams = _DBAPIMultiExecuteParams
260_AnyExecuteParams = _DBAPIAnyExecuteParams
262CompiledCacheType = MutableMapping[Any, "Compiled"]
263SchemaTranslateMapType = Mapping[Optional[str], Optional[str]]
265_ImmutableExecuteOptions = immutabledict[str, Any]
267_ParamStyle = Literal[
268 "qmark", "numeric", "named", "format", "pyformat", "numeric_dollar"
269]
271_GenericSetInputSizesType = List[Tuple[str, Any, "TypeEngine[Any]"]]
273IsolationLevel = Literal[
274 "SERIALIZABLE",
275 "REPEATABLE READ",
276 "READ COMMITTED",
277 "READ UNCOMMITTED",
278 "AUTOCOMMIT",
279]
282class _CoreKnownExecutionOptions(TypedDict, total=False):
283 compiled_cache: Optional[CompiledCacheType]
284 logging_token: str
285 isolation_level: IsolationLevel
286 no_parameters: bool
287 stream_results: bool
288 max_row_buffer: int
289 yield_per: int
290 insertmanyvalues_page_size: int
291 schema_translate_map: Optional[SchemaTranslateMapType]
292 preserve_rowcount: bool
295_ExecuteOptions = immutabledict[str, Any]
296CoreExecuteOptionsParameter = Union[
297 _CoreKnownExecutionOptions, Mapping[str, Any]
298]
301class ReflectedIdentity(TypedDict):
302 """represent the reflected IDENTITY structure of a column, corresponding
303 to the :class:`_schema.Identity` construct.
305 The :class:`.ReflectedIdentity` structure is part of the
306 :class:`.ReflectedColumn` structure, which is returned by the
307 :meth:`.Inspector.get_columns` method.
309 """
311 always: bool
312 """type of identity column"""
314 on_null: bool
315 """indicates ON NULL"""
317 start: int
318 """starting index of the sequence"""
320 increment: int
321 """increment value of the sequence"""
323 minvalue: int
324 """the minimum value of the sequence."""
326 maxvalue: int
327 """the maximum value of the sequence."""
329 nominvalue: bool
330 """no minimum value of the sequence."""
332 nomaxvalue: bool
333 """no maximum value of the sequence."""
335 cycle: bool
336 """allows the sequence to wrap around when the maxvalue
337 or minvalue has been reached."""
339 cache: Optional[int]
340 """number of future values in the
341 sequence which are calculated in advance."""
343 order: bool
344 """if true, renders the ORDER keyword."""
347class ReflectedComputed(TypedDict):
348 """Represent the reflected elements of a computed column, corresponding
349 to the :class:`_schema.Computed` construct.
351 The :class:`.ReflectedComputed` structure is part of the
352 :class:`.ReflectedColumn` structure, which is returned by the
353 :meth:`.Inspector.get_columns` method.
355 """
357 sqltext: str
358 """the expression used to generate this column returned
359 as a string SQL expression"""
361 persisted: NotRequired[bool]
362 """indicates if the value is stored in the table or computed on demand"""
365class ReflectedColumn(TypedDict):
366 """Dictionary representing the reflected elements corresponding to
367 a :class:`_schema.Column` object.
369 The :class:`.ReflectedColumn` structure is returned by the
370 :class:`.Inspector.get_columns` method.
372 """
374 name: str
375 """column name"""
377 type: TypeEngine[Any]
378 """column type represented as a :class:`.TypeEngine` instance."""
380 nullable: bool
381 """boolean flag if the column is NULL or NOT NULL"""
383 default: Optional[str]
384 """column default expression as a SQL string"""
386 autoincrement: NotRequired[bool]
387 """database-dependent autoincrement flag.
389 This flag indicates if the column has a database-side "autoincrement"
390 flag of some kind. Within SQLAlchemy, other kinds of columns may
391 also act as an "autoincrement" column without necessarily having
392 such a flag on them.
394 See :paramref:`_schema.Column.autoincrement` for more background on
395 "autoincrement".
397 """
399 comment: NotRequired[Optional[str]]
400 """comment for the column, if present.
401 Only some dialects return this key
402 """
404 computed: NotRequired[ReflectedComputed]
405 """indicates that this column is computed by the database.
406 Only some dialects return this key.
408 .. versionadded:: 1.3.16 - added support for computed reflection.
409 """
411 identity: NotRequired[ReflectedIdentity]
412 """indicates this column is an IDENTITY column.
413 Only some dialects return this key.
415 .. versionadded:: 1.4 - added support for identity column reflection.
416 """
418 dialect_options: NotRequired[Dict[str, Any]]
419 """Additional dialect-specific options detected for this reflected
420 object"""
423class ReflectedConstraint(TypedDict):
424 """Dictionary representing the reflected elements corresponding to
425 :class:`.Constraint`
427 A base class for all constraints
428 """
430 name: Optional[str]
431 """constraint name"""
433 comment: NotRequired[Optional[str]]
434 """comment for the constraint, if present"""
437class ReflectedCheckConstraint(ReflectedConstraint):
438 """Dictionary representing the reflected elements corresponding to
439 :class:`.CheckConstraint`.
441 The :class:`.ReflectedCheckConstraint` structure is returned by the
442 :meth:`.Inspector.get_check_constraints` method.
444 """
446 sqltext: str
447 """the check constraint's SQL expression"""
449 dialect_options: NotRequired[Dict[str, Any]]
450 """Additional dialect-specific options detected for this check constraint
452 .. versionadded:: 1.3.8
453 """
456class ReflectedUniqueConstraint(ReflectedConstraint):
457 """Dictionary representing the reflected elements corresponding to
458 :class:`.UniqueConstraint`.
460 The :class:`.ReflectedUniqueConstraint` structure is returned by the
461 :meth:`.Inspector.get_unique_constraints` method.
463 """
465 column_names: List[str]
466 """column names which comprise the unique constraint"""
468 duplicates_index: NotRequired[Optional[str]]
469 "Indicates if this unique constraint duplicates an index with this name"
471 dialect_options: NotRequired[Dict[str, Any]]
472 """Additional dialect-specific options detected for this unique
473 constraint"""
476class ReflectedPrimaryKeyConstraint(ReflectedConstraint):
477 """Dictionary representing the reflected elements corresponding to
478 :class:`.PrimaryKeyConstraint`.
480 The :class:`.ReflectedPrimaryKeyConstraint` structure is returned by the
481 :meth:`.Inspector.get_pk_constraint` method.
483 """
485 constrained_columns: List[str]
486 """column names which comprise the primary key"""
488 dialect_options: NotRequired[Dict[str, Any]]
489 """Additional dialect-specific options detected for this primary key"""
492class ReflectedForeignKeyConstraint(ReflectedConstraint):
493 """Dictionary representing the reflected elements corresponding to
494 :class:`.ForeignKeyConstraint`.
496 The :class:`.ReflectedForeignKeyConstraint` structure is returned by
497 the :meth:`.Inspector.get_foreign_keys` method.
499 """
501 constrained_columns: List[str]
502 """local column names which comprise the foreign key"""
504 referred_schema: Optional[str]
505 """schema name of the table being referred"""
507 referred_table: str
508 """name of the table being referred"""
510 referred_columns: List[str]
511 """referred column names that correspond to ``constrained_columns``"""
513 options: NotRequired[Dict[str, Any]]
514 """Additional options detected for this foreign key constraint"""
517class ReflectedIndex(TypedDict):
518 """Dictionary representing the reflected elements corresponding to
519 :class:`.Index`.
521 The :class:`.ReflectedIndex` structure is returned by the
522 :meth:`.Inspector.get_indexes` method.
524 """
526 name: Optional[str]
527 """index name"""
529 column_names: List[Optional[str]]
530 """column names which the index references.
531 An element of this list is ``None`` if it's an expression and is
532 returned in the ``expressions`` list.
533 """
535 expressions: NotRequired[List[str]]
536 """Expressions that compose the index. This list, when present, contains
537 both plain column names (that are also in ``column_names``) and
538 expressions (that are ``None`` in ``column_names``).
539 """
541 unique: bool
542 """whether or not the index has a unique flag"""
544 duplicates_constraint: NotRequired[Optional[str]]
545 "Indicates if this index mirrors a constraint with this name"
547 include_columns: NotRequired[List[str]]
548 """columns to include in the INCLUDE clause for supporting databases.
550 .. deprecated:: 2.0
552 Legacy value, will be replaced with
553 ``index_dict["dialect_options"]["<dialect name>_include"]``
555 """
557 column_sorting: NotRequired[Dict[str, Tuple[str]]]
558 """optional dict mapping column names or expressions to tuple of sort
559 keywords, which may include ``asc``, ``desc``, ``nulls_first``,
560 ``nulls_last``.
562 .. versionadded:: 1.3.5
563 """
565 dialect_options: NotRequired[Dict[str, Any]]
566 """Additional dialect-specific options detected for this index"""
569class ReflectedTableComment(TypedDict):
570 """Dictionary representing the reflected comment corresponding to
571 the :attr:`_schema.Table.comment` attribute.
573 The :class:`.ReflectedTableComment` structure is returned by the
574 :meth:`.Inspector.get_table_comment` method.
576 """
578 text: Optional[str]
579 """text of the comment"""
582class BindTyping(Enum):
583 """Define different methods of passing typing information for
584 bound parameters in a statement to the database driver.
586 .. versionadded:: 2.0
588 """
590 NONE = 1
591 """No steps are taken to pass typing information to the database driver.
593 This is the default behavior for databases such as SQLite, MySQL / MariaDB,
594 SQL Server.
596 """
598 SETINPUTSIZES = 2
599 """Use the pep-249 setinputsizes method.
601 This is only implemented for DBAPIs that support this method and for which
602 the SQLAlchemy dialect has the appropriate infrastructure for that dialect
603 set up. Current dialects include python-oracledb, cx_Oracle as well as
604 optional support for SQL Server using pyodbc.
606 When using setinputsizes, dialects also have a means of only using the
607 method for certain datatypes using include/exclude lists.
609 When SETINPUTSIZES is used, the :meth:`.Dialect.do_set_input_sizes` method
610 is called for each statement executed which has bound parameters.
612 """
614 RENDER_CASTS = 3
615 """Render casts or other directives in the SQL string.
617 This method is used for all PostgreSQL dialects, including asyncpg,
618 pg8000, psycopg, psycopg2. Dialects which implement this can choose
619 which kinds of datatypes are explicitly cast in SQL statements and which
620 aren't.
622 When RENDER_CASTS is used, the compiler will invoke the
623 :meth:`.SQLCompiler.render_bind_cast` method for the rendered
624 string representation of each :class:`.BindParameter` object whose
625 dialect-level type sets the :attr:`.TypeEngine.render_bind_cast` attribute.
627 The :meth:`.SQLCompiler.render_bind_cast` is also used to render casts
628 for one form of "insertmanyvalues" query, when both
629 :attr:`.InsertmanyvaluesSentinelOpts.USE_INSERT_FROM_SELECT` and
630 :attr:`.InsertmanyvaluesSentinelOpts.RENDER_SELECT_COL_CASTS` are set,
631 where the casts are applied to the intermediary columns e.g.
632 "INSERT INTO t (a, b, c) SELECT p0::TYP, p1::TYP, p2::TYP "
633 "FROM (VALUES (?, ?), (?, ?), ...)".
635 .. versionadded:: 2.0.10 - :meth:`.SQLCompiler.render_bind_cast` is now
636 used within some elements of the "insertmanyvalues" implementation.
639 """
642VersionInfoType = Tuple[Union[int, str], ...]
643TableKey = Tuple[Optional[str], str]
646class Dialect(EventTarget):
647 """Define the behavior of a specific database and DB-API combination.
649 Any aspect of metadata definition, SQL query generation,
650 execution, result-set handling, or anything else which varies
651 between databases is defined under the general category of the
652 Dialect. The Dialect acts as a factory for other
653 database-specific object implementations including
654 ExecutionContext, Compiled, DefaultGenerator, and TypeEngine.
656 .. note:: Third party dialects should not subclass :class:`.Dialect`
657 directly. Instead, subclass :class:`.default.DefaultDialect` or
658 descendant class.
660 """
662 CACHE_HIT = CacheStats.CACHE_HIT
663 CACHE_MISS = CacheStats.CACHE_MISS
664 CACHING_DISABLED = CacheStats.CACHING_DISABLED
665 NO_CACHE_KEY = CacheStats.NO_CACHE_KEY
666 NO_DIALECT_SUPPORT = CacheStats.NO_DIALECT_SUPPORT
668 dispatch: dispatcher[Dialect]
670 name: str
671 """identifying name for the dialect from a DBAPI-neutral point of view
672 (i.e. 'sqlite')
673 """
675 driver: str
676 """identifying name for the dialect's DBAPI"""
678 dialect_description: str
680 dbapi: Optional[DBAPIModule]
681 """A reference to the DBAPI module object itself.
683 SQLAlchemy dialects import DBAPI modules using the classmethod
684 :meth:`.Dialect.import_dbapi`. The rationale is so that any dialect
685 module can be imported and used to generate SQL statements without the
686 need for the actual DBAPI driver to be installed. Only when an
687 :class:`.Engine` is constructed using :func:`.create_engine` does the
688 DBAPI get imported; at that point, the creation process will assign
689 the DBAPI module to this attribute.
691 Dialects should therefore implement :meth:`.Dialect.import_dbapi`
692 which will import the necessary module and return it, and then refer
693 to ``self.dbapi`` in dialect code in order to refer to the DBAPI module
694 contents.
696 .. versionchanged:: The :attr:`.Dialect.dbapi` attribute is exclusively
697 used as the per-:class:`.Dialect`-instance reference to the DBAPI
698 module. The previous not-fully-documented ``.Dialect.dbapi()``
699 classmethod is deprecated and replaced by :meth:`.Dialect.import_dbapi`.
701 """
703 @util.non_memoized_property
704 def loaded_dbapi(self) -> DBAPIModule:
705 """same as .dbapi, but is never None; will raise an error if no
706 DBAPI was set up.
708 .. versionadded:: 2.0
710 """
711 raise NotImplementedError()
713 positional: bool
714 """True if the paramstyle for this Dialect is positional."""
716 paramstyle: str
717 """the paramstyle to be used (some DB-APIs support multiple
718 paramstyles).
719 """
721 compiler_linting: Linting
723 statement_compiler: Type[SQLCompiler]
724 """a :class:`.Compiled` class used to compile SQL statements"""
726 ddl_compiler: Type[DDLCompiler]
727 """a :class:`.Compiled` class used to compile DDL statements"""
729 type_compiler_cls: ClassVar[Type[TypeCompiler]]
730 """a :class:`.Compiled` class used to compile SQL type objects
732 .. versionadded:: 2.0
734 """
736 type_compiler_instance: TypeCompiler
737 """instance of a :class:`.Compiled` class used to compile SQL type
738 objects
740 .. versionadded:: 2.0
742 """
744 type_compiler: Any
745 """legacy; this is a TypeCompiler class at the class level, a
746 TypeCompiler instance at the instance level.
748 Refer to type_compiler_instance instead.
750 """
752 preparer: Type[IdentifierPreparer]
753 """a :class:`.IdentifierPreparer` class used to
754 quote identifiers.
755 """
757 identifier_preparer: IdentifierPreparer
758 """This element will refer to an instance of :class:`.IdentifierPreparer`
759 once a :class:`.DefaultDialect` has been constructed.
761 """
763 server_version_info: Optional[Tuple[Any, ...]]
764 """a tuple containing a version number for the DB backend in use.
766 This value is only available for supporting dialects, and is
767 typically populated during the initial connection to the database.
768 """
770 default_schema_name: Optional[str]
771 """the name of the default schema. This value is only available for
772 supporting dialects, and is typically populated during the
773 initial connection to the database.
775 """
777 # NOTE: this does not take into effect engine-level isolation level.
778 # not clear if this should be changed, seems like it should
779 default_isolation_level: Optional[IsolationLevel]
780 """the isolation that is implicitly present on new connections"""
782 skip_autocommit_rollback: bool
783 """Whether or not the :paramref:`.create_engine.skip_autocommit_rollback`
784 parameter was set.
786 .. versionadded:: 2.0.43
788 """
790 # create_engine() -> isolation_level currently goes here
791 _on_connect_isolation_level: Optional[IsolationLevel]
793 execution_ctx_cls: Type[ExecutionContext]
794 """a :class:`.ExecutionContext` class used to handle statement execution"""
796 execute_sequence_format: Union[
797 Type[Tuple[Any, ...]], Type[Tuple[List[Any]]]
798 ]
799 """either the 'tuple' or 'list' type, depending on what cursor.execute()
800 accepts for the second argument (they vary)."""
802 supports_alter: bool
803 """``True`` if the database supports ``ALTER TABLE`` - used only for
804 generating foreign key constraints in certain circumstances
805 """
807 max_identifier_length: int
808 """The maximum length of identifier names."""
809 max_index_name_length: Optional[int]
810 """The maximum length of index names if different from
811 ``max_identifier_length``."""
812 max_constraint_name_length: Optional[int]
813 """The maximum length of constraint names if different from
814 ``max_identifier_length``."""
816 supports_server_side_cursors: Union[generic_fn_descriptor[bool], bool]
817 """indicates if the dialect supports server side cursors"""
819 server_side_cursors: bool
820 """deprecated; indicates if the dialect should attempt to use server
821 side cursors by default"""
823 supports_sane_rowcount: bool
824 """Indicate whether the dialect properly implements rowcount for
825 ``UPDATE`` and ``DELETE`` statements.
826 """
828 supports_sane_multi_rowcount: bool
829 """Indicate whether the dialect properly implements rowcount for
830 ``UPDATE`` and ``DELETE`` statements when executed via
831 executemany.
832 """
834 supports_empty_insert: bool
835 """dialect supports INSERT () VALUES (), i.e. a plain INSERT with no
836 columns in it.
838 This is not usually supported; an "empty" insert is typically
839 suited using either "INSERT..DEFAULT VALUES" or
840 "INSERT ... (col) VALUES (DEFAULT)".
842 """
844 supports_default_values: bool
845 """dialect supports INSERT... DEFAULT VALUES syntax"""
847 supports_default_metavalue: bool
848 """dialect supports INSERT...(col) VALUES (DEFAULT) syntax.
850 Most databases support this in some way, e.g. SQLite supports it using
851 ``VALUES (NULL)``. MS SQL Server supports the syntax also however
852 is the only included dialect where we have this disabled, as
853 MSSQL does not support the field for the IDENTITY column, which is
854 usually where we like to make use of the feature.
856 """
858 default_metavalue_token: str = "DEFAULT"
859 """for INSERT... VALUES (DEFAULT) syntax, the token to put in the
860 parenthesis.
862 E.g. for SQLite this is the keyword "NULL".
864 """
866 supports_multivalues_insert: bool
867 """Target database supports INSERT...VALUES with multiple value
868 sets, i.e. INSERT INTO table (cols) VALUES (...), (...), (...), ...
870 """
872 insert_executemany_returning: bool
873 """dialect / driver / database supports some means of providing
874 INSERT...RETURNING support when dialect.do_executemany() is used.
876 """
878 insert_executemany_returning_sort_by_parameter_order: bool
879 """dialect / driver / database supports some means of providing
880 INSERT...RETURNING support when dialect.do_executemany() is used
881 along with the :paramref:`_dml.Insert.returning.sort_by_parameter_order`
882 parameter being set.
884 """
886 update_executemany_returning: bool
887 """dialect supports UPDATE..RETURNING with executemany."""
889 delete_executemany_returning: bool
890 """dialect supports DELETE..RETURNING with executemany."""
892 use_insertmanyvalues: bool
893 """if True, indicates "insertmanyvalues" functionality should be used
894 to allow for ``insert_executemany_returning`` behavior, if possible.
896 In practice, setting this to True means:
898 if ``supports_multivalues_insert``, ``insert_returning`` and
899 ``use_insertmanyvalues`` are all True, the SQL compiler will produce
900 an INSERT that will be interpreted by the :class:`.DefaultDialect`
901 as an :attr:`.ExecuteStyle.INSERTMANYVALUES` execution that allows
902 for INSERT of many rows with RETURNING by rewriting a single-row
903 INSERT statement to have multiple VALUES clauses, also executing
904 the statement multiple times for a series of batches when large numbers
905 of rows are given.
907 The parameter is False for the default dialect, and is set to True for
908 SQLAlchemy internal dialects SQLite, MySQL/MariaDB, PostgreSQL, SQL Server.
909 It remains at False for Oracle Database, which provides native "executemany
910 with RETURNING" support and also does not support
911 ``supports_multivalues_insert``. For MySQL/MariaDB, those MySQL dialects
912 that don't support RETURNING will not report
913 ``insert_executemany_returning`` as True.
915 .. versionadded:: 2.0
917 .. seealso::
919 :ref:`engine_insertmanyvalues`
921 """
923 use_insertmanyvalues_wo_returning: bool
924 """if True, and use_insertmanyvalues is also True, INSERT statements
925 that don't include RETURNING will also use "insertmanyvalues".
927 .. versionadded:: 2.0
929 .. seealso::
931 :ref:`engine_insertmanyvalues`
933 """
935 insertmanyvalues_implicit_sentinel: InsertmanyvaluesSentinelOpts
936 """Options indicating the database supports a form of bulk INSERT where
937 the autoincrement integer primary key can be reliably used as an ordering
938 for INSERTed rows.
940 .. versionadded:: 2.0.10
942 .. seealso::
944 :ref:`engine_insertmanyvalues_returning_order`
946 """
948 insertmanyvalues_page_size: int
949 """Number of rows to render into an individual INSERT..VALUES() statement
950 for :attr:`.ExecuteStyle.INSERTMANYVALUES` executions.
952 The default dialect defaults this to 1000.
954 .. versionadded:: 2.0
956 .. seealso::
958 :paramref:`_engine.Connection.execution_options.insertmanyvalues_page_size` -
959 execution option available on :class:`_engine.Connection`, statements
961 """ # noqa: E501
963 insertmanyvalues_max_parameters: int
964 """Alternate to insertmanyvalues_page_size, will additionally limit
965 page size based on number of parameters total in the statement.
968 """
970 preexecute_autoincrement_sequences: bool
971 """True if 'implicit' primary key functions must be executed separately
972 in order to get their value, if RETURNING is not used.
974 This is currently oriented towards PostgreSQL when the
975 ``implicit_returning=False`` parameter is used on a :class:`.Table`
976 object.
978 """
980 insert_returning: bool
981 """if the dialect supports RETURNING with INSERT
983 .. versionadded:: 2.0
985 """
987 update_returning: bool
988 """if the dialect supports RETURNING with UPDATE
990 .. versionadded:: 2.0
992 """
994 update_returning_multifrom: bool
995 """if the dialect supports RETURNING with UPDATE..FROM
997 .. versionadded:: 2.0
999 """
1001 delete_returning: bool
1002 """if the dialect supports RETURNING with DELETE
1004 .. versionadded:: 2.0
1006 """
1008 delete_returning_multifrom: bool
1009 """if the dialect supports RETURNING with DELETE..FROM
1011 .. versionadded:: 2.0
1013 """
1015 favor_returning_over_lastrowid: bool
1016 """for backends that support both a lastrowid and a RETURNING insert
1017 strategy, favor RETURNING for simple single-int pk inserts.
1019 cursor.lastrowid tends to be more performant on most backends.
1021 """
1023 supports_identity_columns: bool
1024 """target database supports IDENTITY"""
1026 cte_follows_insert: bool
1027 """target database, when given a CTE with an INSERT statement, needs
1028 the CTE to be below the INSERT"""
1030 colspecs: MutableMapping[Type[TypeEngine[Any]], Type[TypeEngine[Any]]]
1031 """A dictionary of TypeEngine classes from sqlalchemy.types mapped
1032 to subclasses that are specific to the dialect class. This
1033 dictionary is class-level only and is not accessed from the
1034 dialect instance itself.
1035 """
1037 supports_sequences: bool
1038 """Indicates if the dialect supports CREATE SEQUENCE or similar."""
1040 sequences_optional: bool
1041 """If True, indicates if the :paramref:`_schema.Sequence.optional`
1042 parameter on the :class:`_schema.Sequence` construct
1043 should signal to not generate a CREATE SEQUENCE. Applies only to
1044 dialects that support sequences. Currently used only to allow PostgreSQL
1045 SERIAL to be used on a column that specifies Sequence() for usage on
1046 other backends.
1047 """
1049 default_sequence_base: int
1050 """the default value that will be rendered as the "START WITH" portion of
1051 a CREATE SEQUENCE DDL statement.
1053 """
1055 supports_native_enum: bool
1056 """Indicates if the dialect supports a native ENUM construct.
1057 This will prevent :class:`_types.Enum` from generating a CHECK
1058 constraint when that type is used in "native" mode.
1059 """
1061 supports_native_boolean: bool
1062 """Indicates if the dialect supports a native boolean construct.
1063 This will prevent :class:`_types.Boolean` from generating a CHECK
1064 constraint when that type is used.
1065 """
1067 supports_native_decimal: bool
1068 """indicates if Decimal objects are handled and returned for precision
1069 numeric types, or if floats are returned"""
1071 supports_native_uuid: bool
1072 """indicates if Python UUID() objects are handled natively by the
1073 driver for SQL UUID datatypes.
1075 .. versionadded:: 2.0
1077 """
1079 returns_native_bytes: bool
1080 """indicates if Python bytes() objects are returned natively by the
1081 driver for SQL "binary" datatypes.
1083 .. versionadded:: 2.0.11
1085 """
1087 construct_arguments: Optional[
1088 List[Tuple[Type[Union[SchemaItem, ClauseElement]], Mapping[str, Any]]]
1089 ] = None
1090 """Optional set of argument specifiers for various SQLAlchemy
1091 constructs, typically schema items.
1093 To implement, establish as a series of tuples, as in::
1095 construct_arguments = [
1096 (schema.Index, {"using": False, "where": None, "ops": None}),
1097 ]
1099 If the above construct is established on the PostgreSQL dialect,
1100 the :class:`.Index` construct will now accept the keyword arguments
1101 ``postgresql_using``, ``postgresql_where``, nad ``postgresql_ops``.
1102 Any other argument specified to the constructor of :class:`.Index`
1103 which is prefixed with ``postgresql_`` will raise :class:`.ArgumentError`.
1105 A dialect which does not include a ``construct_arguments`` member will
1106 not participate in the argument validation system. For such a dialect,
1107 any argument name is accepted by all participating constructs, within
1108 the namespace of arguments prefixed with that dialect name. The rationale
1109 here is so that third-party dialects that haven't yet implemented this
1110 feature continue to function in the old way.
1112 .. seealso::
1114 :class:`.DialectKWArgs` - implementing base class which consumes
1115 :attr:`.DefaultDialect.construct_arguments`
1118 """
1120 reflection_options: Sequence[str] = ()
1121 """Sequence of string names indicating keyword arguments that can be
1122 established on a :class:`.Table` object which will be passed as
1123 "reflection options" when using :paramref:`.Table.autoload_with`.
1125 Current example is "oracle_resolve_synonyms" in the Oracle Database
1126 dialects.
1128 """
1130 dbapi_exception_translation_map: Mapping[str, str] = util.EMPTY_DICT
1131 """A dictionary of names that will contain as values the names of
1132 pep-249 exceptions ("IntegrityError", "OperationalError", etc)
1133 keyed to alternate class names, to support the case where a
1134 DBAPI has exception classes that aren't named as they are
1135 referred to (e.g. IntegrityError = MyException). In the vast
1136 majority of cases this dictionary is empty.
1137 """
1139 supports_comments: bool
1140 """Indicates the dialect supports comment DDL on tables and columns."""
1142 inline_comments: bool
1143 """Indicates the dialect supports comment DDL that's inline with the
1144 definition of a Table or Column. If False, this implies that ALTER must
1145 be used to set table and column comments."""
1147 supports_constraint_comments: bool
1148 """Indicates if the dialect supports comment DDL on constraints.
1150 .. versionadded:: 2.0
1151 """
1153 _has_events = False
1155 supports_statement_cache: bool = True
1156 """indicates if this dialect supports caching.
1158 All dialects that are compatible with statement caching should set this
1159 flag to True directly on each dialect class and subclass that supports
1160 it. SQLAlchemy tests that this flag is locally present on each dialect
1161 subclass before it will use statement caching. This is to provide
1162 safety for legacy or new dialects that are not yet fully tested to be
1163 compliant with SQL statement caching.
1165 .. versionadded:: 1.4.5
1167 .. seealso::
1169 :ref:`engine_thirdparty_caching`
1171 """
1173 _supports_statement_cache: bool
1174 """internal evaluation for supports_statement_cache"""
1176 bind_typing = BindTyping.NONE
1177 """define a means of passing typing information to the database and/or
1178 driver for bound parameters.
1180 See :class:`.BindTyping` for values.
1182 .. versionadded:: 2.0
1184 """
1186 is_async: bool
1187 """Whether or not this dialect is intended for asyncio use."""
1189 has_terminate: bool
1190 """Whether or not this dialect has a separate "terminate" implementation
1191 that does not block or require awaiting."""
1193 engine_config_types: Mapping[str, Any]
1194 """a mapping of string keys that can be in an engine config linked to
1195 type conversion functions.
1197 """
1199 label_length: Optional[int]
1200 """optional user-defined max length for SQL labels"""
1202 include_set_input_sizes: Optional[Set[Any]]
1203 """set of DBAPI type objects that should be included in
1204 automatic cursor.setinputsizes() calls.
1206 This is only used if bind_typing is BindTyping.SET_INPUT_SIZES
1208 """
1210 exclude_set_input_sizes: Optional[Set[Any]]
1211 """set of DBAPI type objects that should be excluded in
1212 automatic cursor.setinputsizes() calls.
1214 This is only used if bind_typing is BindTyping.SET_INPUT_SIZES
1216 """
1218 supports_simple_order_by_label: bool
1219 """target database supports ORDER BY <labelname>, where <labelname>
1220 refers to a label in the columns clause of the SELECT"""
1222 div_is_floordiv: bool
1223 """target database treats the / division operator as "floor division" """
1225 tuple_in_values: bool
1226 """target database supports tuple IN, i.e. (x, y) IN ((q, p), (r, z))"""
1228 _bind_typing_render_casts: bool
1230 _type_memos: MutableMapping[TypeEngine[Any], _TypeMemoDict]
1232 def _builtin_onconnect(self) -> Optional[_ListenerFnType]:
1233 raise NotImplementedError()
1235 def create_connect_args(self, url: URL) -> ConnectArgsType:
1236 """Build DB-API compatible connection arguments.
1238 Given a :class:`.URL` object, returns a tuple
1239 consisting of a ``(*args, **kwargs)`` suitable to send directly
1240 to the dbapi's connect function. The arguments are sent to the
1241 :meth:`.Dialect.connect` method which then runs the DBAPI-level
1242 ``connect()`` function.
1244 The method typically makes use of the
1245 :meth:`.URL.translate_connect_args`
1246 method in order to generate a dictionary of options.
1248 The default implementation is::
1250 def create_connect_args(self, url):
1251 opts = url.translate_connect_args()
1252 opts.update(url.query)
1253 return ([], opts)
1255 :param url: a :class:`.URL` object
1257 :return: a tuple of ``(*args, **kwargs)`` which will be passed to the
1258 :meth:`.Dialect.connect` method.
1260 .. seealso::
1262 :meth:`.URL.translate_connect_args`
1264 """
1266 raise NotImplementedError()
1268 @classmethod
1269 def import_dbapi(cls) -> DBAPIModule:
1270 """Import the DBAPI module that is used by this dialect.
1272 The Python module object returned here will be assigned as an
1273 instance variable to a constructed dialect under the name
1274 ``.dbapi``.
1276 .. versionchanged:: 2.0 The :meth:`.Dialect.import_dbapi` class
1277 method is renamed from the previous method ``.Dialect.dbapi()``,
1278 which would be replaced at dialect instantiation time by the
1279 DBAPI module itself, thus using the same name in two different ways.
1280 If a ``.Dialect.dbapi()`` classmethod is present on a third-party
1281 dialect, it will be used and a deprecation warning will be emitted.
1283 """
1284 raise NotImplementedError()
1286 def type_descriptor(self, typeobj: TypeEngine[_T]) -> TypeEngine[_T]:
1287 """Transform a generic type to a dialect-specific type.
1289 Dialect classes will usually use the
1290 :func:`_types.adapt_type` function in the types module to
1291 accomplish this.
1293 The returned result is cached *per dialect class* so can
1294 contain no dialect-instance state.
1296 """
1298 raise NotImplementedError()
1300 def initialize(self, connection: Connection) -> None:
1301 """Called during strategized creation of the dialect with a
1302 connection.
1304 Allows dialects to configure options based on server version info or
1305 other properties.
1307 The connection passed here is a SQLAlchemy Connection object,
1308 with full capabilities.
1310 The initialize() method of the base dialect should be called via
1311 super().
1313 .. note:: as of SQLAlchemy 1.4, this method is called **before**
1314 any :meth:`_engine.Dialect.on_connect` hooks are called.
1316 """
1318 if TYPE_CHECKING:
1320 def _overrides_default(self, method_name: str) -> bool: ...
1322 def get_columns(
1323 self,
1324 connection: Connection,
1325 table_name: str,
1326 schema: Optional[str] = None,
1327 **kw: Any,
1328 ) -> List[ReflectedColumn]:
1329 """Return information about columns in ``table_name``.
1331 Given a :class:`_engine.Connection`, a string
1332 ``table_name``, and an optional string ``schema``, return column
1333 information as a list of dictionaries
1334 corresponding to the :class:`.ReflectedColumn` dictionary.
1336 This is an internal dialect method. Applications should use
1337 :meth:`.Inspector.get_columns`.
1339 """
1341 raise NotImplementedError()
1343 def get_multi_columns(
1344 self,
1345 connection: Connection,
1346 *,
1347 schema: Optional[str] = None,
1348 filter_names: Optional[Collection[str]] = None,
1349 **kw: Any,
1350 ) -> Iterable[Tuple[TableKey, List[ReflectedColumn]]]:
1351 """Return information about columns in all tables in the
1352 given ``schema``.
1354 This is an internal dialect method. Applications should use
1355 :meth:`.Inspector.get_multi_columns`.
1357 .. note:: The :class:`_engine.DefaultDialect` provides a default
1358 implementation that will call the single table method for
1359 each object returned by :meth:`Dialect.get_table_names`,
1360 :meth:`Dialect.get_view_names` or
1361 :meth:`Dialect.get_materialized_view_names` depending on the
1362 provided ``kind``. Dialects that want to support a faster
1363 implementation should implement this method.
1365 .. versionadded:: 2.0
1367 """
1369 raise NotImplementedError()
1371 def get_pk_constraint(
1372 self,
1373 connection: Connection,
1374 table_name: str,
1375 schema: Optional[str] = None,
1376 **kw: Any,
1377 ) -> ReflectedPrimaryKeyConstraint:
1378 """Return information about the primary key constraint on
1379 table_name`.
1381 Given a :class:`_engine.Connection`, a string
1382 ``table_name``, and an optional string ``schema``, return primary
1383 key information as a dictionary corresponding to the
1384 :class:`.ReflectedPrimaryKeyConstraint` dictionary.
1386 This is an internal dialect method. Applications should use
1387 :meth:`.Inspector.get_pk_constraint`.
1389 """
1390 raise NotImplementedError()
1392 def get_multi_pk_constraint(
1393 self,
1394 connection: Connection,
1395 *,
1396 schema: Optional[str] = None,
1397 filter_names: Optional[Collection[str]] = None,
1398 **kw: Any,
1399 ) -> Iterable[Tuple[TableKey, ReflectedPrimaryKeyConstraint]]:
1400 """Return information about primary key constraints in
1401 all tables in the given ``schema``.
1403 This is an internal dialect method. Applications should use
1404 :meth:`.Inspector.get_multi_pk_constraint`.
1406 .. note:: The :class:`_engine.DefaultDialect` provides a default
1407 implementation that will call the single table method for
1408 each object returned by :meth:`Dialect.get_table_names`,
1409 :meth:`Dialect.get_view_names` or
1410 :meth:`Dialect.get_materialized_view_names` depending on the
1411 provided ``kind``. Dialects that want to support a faster
1412 implementation should implement this method.
1414 .. versionadded:: 2.0
1416 """
1417 raise NotImplementedError()
1419 def get_foreign_keys(
1420 self,
1421 connection: Connection,
1422 table_name: str,
1423 schema: Optional[str] = None,
1424 **kw: Any,
1425 ) -> List[ReflectedForeignKeyConstraint]:
1426 """Return information about foreign_keys in ``table_name``.
1428 Given a :class:`_engine.Connection`, a string
1429 ``table_name``, and an optional string ``schema``, return foreign
1430 key information as a list of dicts corresponding to the
1431 :class:`.ReflectedForeignKeyConstraint` dictionary.
1433 This is an internal dialect method. Applications should use
1434 :meth:`_engine.Inspector.get_foreign_keys`.
1435 """
1437 raise NotImplementedError()
1439 def get_multi_foreign_keys(
1440 self,
1441 connection: Connection,
1442 *,
1443 schema: Optional[str] = None,
1444 filter_names: Optional[Collection[str]] = None,
1445 **kw: Any,
1446 ) -> Iterable[Tuple[TableKey, List[ReflectedForeignKeyConstraint]]]:
1447 """Return information about foreign_keys in all tables
1448 in the given ``schema``.
1450 This is an internal dialect method. Applications should use
1451 :meth:`_engine.Inspector.get_multi_foreign_keys`.
1453 .. note:: The :class:`_engine.DefaultDialect` provides a default
1454 implementation that will call the single table method for
1455 each object returned by :meth:`Dialect.get_table_names`,
1456 :meth:`Dialect.get_view_names` or
1457 :meth:`Dialect.get_materialized_view_names` depending on the
1458 provided ``kind``. Dialects that want to support a faster
1459 implementation should implement this method.
1461 .. versionadded:: 2.0
1463 """
1465 raise NotImplementedError()
1467 def get_table_names(
1468 self, connection: Connection, schema: Optional[str] = None, **kw: Any
1469 ) -> List[str]:
1470 """Return a list of table names for ``schema``.
1472 This is an internal dialect method. Applications should use
1473 :meth:`_engine.Inspector.get_table_names`.
1475 """
1477 raise NotImplementedError()
1479 def get_temp_table_names(
1480 self, connection: Connection, schema: Optional[str] = None, **kw: Any
1481 ) -> List[str]:
1482 """Return a list of temporary table names on the given connection,
1483 if supported by the underlying backend.
1485 This is an internal dialect method. Applications should use
1486 :meth:`_engine.Inspector.get_temp_table_names`.
1488 """
1490 raise NotImplementedError()
1492 def get_view_names(
1493 self, connection: Connection, schema: Optional[str] = None, **kw: Any
1494 ) -> List[str]:
1495 """Return a list of all non-materialized view names available in the
1496 database.
1498 This is an internal dialect method. Applications should use
1499 :meth:`_engine.Inspector.get_view_names`.
1501 :param schema: schema name to query, if not the default schema.
1503 """
1505 raise NotImplementedError()
1507 def get_materialized_view_names(
1508 self, connection: Connection, schema: Optional[str] = None, **kw: Any
1509 ) -> List[str]:
1510 """Return a list of all materialized view names available in the
1511 database.
1513 This is an internal dialect method. Applications should use
1514 :meth:`_engine.Inspector.get_materialized_view_names`.
1516 :param schema: schema name to query, if not the default schema.
1518 .. versionadded:: 2.0
1520 """
1522 raise NotImplementedError()
1524 def get_sequence_names(
1525 self, connection: Connection, schema: Optional[str] = None, **kw: Any
1526 ) -> List[str]:
1527 """Return a list of all sequence names available in the database.
1529 This is an internal dialect method. Applications should use
1530 :meth:`_engine.Inspector.get_sequence_names`.
1532 :param schema: schema name to query, if not the default schema.
1534 .. versionadded:: 1.4
1535 """
1537 raise NotImplementedError()
1539 def get_temp_view_names(
1540 self, connection: Connection, schema: Optional[str] = None, **kw: Any
1541 ) -> List[str]:
1542 """Return a list of temporary view names on the given connection,
1543 if supported by the underlying backend.
1545 This is an internal dialect method. Applications should use
1546 :meth:`_engine.Inspector.get_temp_view_names`.
1548 """
1550 raise NotImplementedError()
1552 def get_schema_names(self, connection: Connection, **kw: Any) -> List[str]:
1553 """Return a list of all schema names available in the database.
1555 This is an internal dialect method. Applications should use
1556 :meth:`_engine.Inspector.get_schema_names`.
1557 """
1558 raise NotImplementedError()
1560 def get_view_definition(
1561 self,
1562 connection: Connection,
1563 view_name: str,
1564 schema: Optional[str] = None,
1565 **kw: Any,
1566 ) -> str:
1567 """Return plain or materialized view definition.
1569 This is an internal dialect method. Applications should use
1570 :meth:`_engine.Inspector.get_view_definition`.
1572 Given a :class:`_engine.Connection`, a string
1573 ``view_name``, and an optional string ``schema``, return the view
1574 definition.
1575 """
1577 raise NotImplementedError()
1579 def get_indexes(
1580 self,
1581 connection: Connection,
1582 table_name: str,
1583 schema: Optional[str] = None,
1584 **kw: Any,
1585 ) -> List[ReflectedIndex]:
1586 """Return information about indexes in ``table_name``.
1588 Given a :class:`_engine.Connection`, a string
1589 ``table_name`` and an optional string ``schema``, return index
1590 information as a list of dictionaries corresponding to the
1591 :class:`.ReflectedIndex` dictionary.
1593 This is an internal dialect method. Applications should use
1594 :meth:`.Inspector.get_indexes`.
1595 """
1597 raise NotImplementedError()
1599 def get_multi_indexes(
1600 self,
1601 connection: Connection,
1602 *,
1603 schema: Optional[str] = None,
1604 filter_names: Optional[Collection[str]] = None,
1605 **kw: Any,
1606 ) -> Iterable[Tuple[TableKey, List[ReflectedIndex]]]:
1607 """Return information about indexes in in all tables
1608 in the given ``schema``.
1610 This is an internal dialect method. Applications should use
1611 :meth:`.Inspector.get_multi_indexes`.
1613 .. note:: The :class:`_engine.DefaultDialect` provides a default
1614 implementation that will call the single table method for
1615 each object returned by :meth:`Dialect.get_table_names`,
1616 :meth:`Dialect.get_view_names` or
1617 :meth:`Dialect.get_materialized_view_names` depending on the
1618 provided ``kind``. Dialects that want to support a faster
1619 implementation should implement this method.
1621 .. versionadded:: 2.0
1623 """
1625 raise NotImplementedError()
1627 def get_unique_constraints(
1628 self,
1629 connection: Connection,
1630 table_name: str,
1631 schema: Optional[str] = None,
1632 **kw: Any,
1633 ) -> List[ReflectedUniqueConstraint]:
1634 r"""Return information about unique constraints in ``table_name``.
1636 Given a string ``table_name`` and an optional string ``schema``, return
1637 unique constraint information as a list of dicts corresponding
1638 to the :class:`.ReflectedUniqueConstraint` dictionary.
1640 This is an internal dialect method. Applications should use
1641 :meth:`.Inspector.get_unique_constraints`.
1642 """
1644 raise NotImplementedError()
1646 def get_multi_unique_constraints(
1647 self,
1648 connection: Connection,
1649 *,
1650 schema: Optional[str] = None,
1651 filter_names: Optional[Collection[str]] = None,
1652 **kw: Any,
1653 ) -> Iterable[Tuple[TableKey, List[ReflectedUniqueConstraint]]]:
1654 """Return information about unique constraints in all tables
1655 in the given ``schema``.
1657 This is an internal dialect method. Applications should use
1658 :meth:`.Inspector.get_multi_unique_constraints`.
1660 .. note:: The :class:`_engine.DefaultDialect` provides a default
1661 implementation that will call the single table method for
1662 each object returned by :meth:`Dialect.get_table_names`,
1663 :meth:`Dialect.get_view_names` or
1664 :meth:`Dialect.get_materialized_view_names` depending on the
1665 provided ``kind``. Dialects that want to support a faster
1666 implementation should implement this method.
1668 .. versionadded:: 2.0
1670 """
1672 raise NotImplementedError()
1674 def get_check_constraints(
1675 self,
1676 connection: Connection,
1677 table_name: str,
1678 schema: Optional[str] = None,
1679 **kw: Any,
1680 ) -> List[ReflectedCheckConstraint]:
1681 r"""Return information about check constraints in ``table_name``.
1683 Given a string ``table_name`` and an optional string ``schema``, return
1684 check constraint information as a list of dicts corresponding
1685 to the :class:`.ReflectedCheckConstraint` dictionary.
1687 This is an internal dialect method. Applications should use
1688 :meth:`.Inspector.get_check_constraints`.
1690 """
1692 raise NotImplementedError()
1694 def get_multi_check_constraints(
1695 self,
1696 connection: Connection,
1697 *,
1698 schema: Optional[str] = None,
1699 filter_names: Optional[Collection[str]] = None,
1700 **kw: Any,
1701 ) -> Iterable[Tuple[TableKey, List[ReflectedCheckConstraint]]]:
1702 """Return information about check constraints in all tables
1703 in the given ``schema``.
1705 This is an internal dialect method. Applications should use
1706 :meth:`.Inspector.get_multi_check_constraints`.
1708 .. note:: The :class:`_engine.DefaultDialect` provides a default
1709 implementation that will call the single table method for
1710 each object returned by :meth:`Dialect.get_table_names`,
1711 :meth:`Dialect.get_view_names` or
1712 :meth:`Dialect.get_materialized_view_names` depending on the
1713 provided ``kind``. Dialects that want to support a faster
1714 implementation should implement this method.
1716 .. versionadded:: 2.0
1718 """
1720 raise NotImplementedError()
1722 def get_table_options(
1723 self,
1724 connection: Connection,
1725 table_name: str,
1726 schema: Optional[str] = None,
1727 **kw: Any,
1728 ) -> Dict[str, Any]:
1729 """Return a dictionary of options specified when ``table_name``
1730 was created.
1732 This is an internal dialect method. Applications should use
1733 :meth:`_engine.Inspector.get_table_options`.
1734 """
1735 raise NotImplementedError()
1737 def get_multi_table_options(
1738 self,
1739 connection: Connection,
1740 *,
1741 schema: Optional[str] = None,
1742 filter_names: Optional[Collection[str]] = None,
1743 **kw: Any,
1744 ) -> Iterable[Tuple[TableKey, Dict[str, Any]]]:
1745 """Return a dictionary of options specified when the tables in the
1746 given schema were created.
1748 This is an internal dialect method. Applications should use
1749 :meth:`_engine.Inspector.get_multi_table_options`.
1751 .. note:: The :class:`_engine.DefaultDialect` provides a default
1752 implementation that will call the single table method for
1753 each object returned by :meth:`Dialect.get_table_names`,
1754 :meth:`Dialect.get_view_names` or
1755 :meth:`Dialect.get_materialized_view_names` depending on the
1756 provided ``kind``. Dialects that want to support a faster
1757 implementation should implement this method.
1759 .. versionadded:: 2.0
1761 """
1762 raise NotImplementedError()
1764 def get_table_comment(
1765 self,
1766 connection: Connection,
1767 table_name: str,
1768 schema: Optional[str] = None,
1769 **kw: Any,
1770 ) -> ReflectedTableComment:
1771 r"""Return the "comment" for the table identified by ``table_name``.
1773 Given a string ``table_name`` and an optional string ``schema``, return
1774 table comment information as a dictionary corresponding to the
1775 :class:`.ReflectedTableComment` dictionary.
1777 This is an internal dialect method. Applications should use
1778 :meth:`.Inspector.get_table_comment`.
1780 :raise: ``NotImplementedError`` for dialects that don't support
1781 comments.
1783 .. versionadded:: 1.2
1785 """
1787 raise NotImplementedError()
1789 def get_multi_table_comment(
1790 self,
1791 connection: Connection,
1792 *,
1793 schema: Optional[str] = None,
1794 filter_names: Optional[Collection[str]] = None,
1795 **kw: Any,
1796 ) -> Iterable[Tuple[TableKey, ReflectedTableComment]]:
1797 """Return information about the table comment in all tables
1798 in the given ``schema``.
1800 This is an internal dialect method. Applications should use
1801 :meth:`_engine.Inspector.get_multi_table_comment`.
1803 .. note:: The :class:`_engine.DefaultDialect` provides a default
1804 implementation that will call the single table method for
1805 each object returned by :meth:`Dialect.get_table_names`,
1806 :meth:`Dialect.get_view_names` or
1807 :meth:`Dialect.get_materialized_view_names` depending on the
1808 provided ``kind``. Dialects that want to support a faster
1809 implementation should implement this method.
1811 .. versionadded:: 2.0
1813 """
1815 raise NotImplementedError()
1817 def normalize_name(self, name: str) -> str:
1818 """convert the given name to lowercase if it is detected as
1819 case insensitive.
1821 This method is only used if the dialect defines
1822 requires_name_normalize=True.
1824 """
1825 raise NotImplementedError()
1827 def denormalize_name(self, name: str) -> str:
1828 """convert the given name to a case insensitive identifier
1829 for the backend if it is an all-lowercase name.
1831 This method is only used if the dialect defines
1832 requires_name_normalize=True.
1834 """
1835 raise NotImplementedError()
1837 def has_table(
1838 self,
1839 connection: Connection,
1840 table_name: str,
1841 schema: Optional[str] = None,
1842 **kw: Any,
1843 ) -> bool:
1844 """For internal dialect use, check the existence of a particular table
1845 or view in the database.
1847 Given a :class:`_engine.Connection` object, a string table_name and
1848 optional schema name, return True if the given table exists in the
1849 database, False otherwise.
1851 This method serves as the underlying implementation of the
1852 public facing :meth:`.Inspector.has_table` method, and is also used
1853 internally to implement the "checkfirst" behavior for methods like
1854 :meth:`_schema.Table.create` and :meth:`_schema.MetaData.create_all`.
1856 .. note:: This method is used internally by SQLAlchemy, and is
1857 published so that third-party dialects may provide an
1858 implementation. It is **not** the public API for checking for table
1859 presence. Please use the :meth:`.Inspector.has_table` method.
1861 .. versionchanged:: 2.0:: :meth:`_engine.Dialect.has_table` now
1862 formally supports checking for additional table-like objects:
1864 * any type of views (plain or materialized)
1865 * temporary tables of any kind
1867 Previously, these two checks were not formally specified and
1868 different dialects would vary in their behavior. The dialect
1869 testing suite now includes tests for all of these object types,
1870 and dialects to the degree that the backing database supports views
1871 or temporary tables should seek to support locating these objects
1872 for full compliance.
1874 """
1876 raise NotImplementedError()
1878 def has_index(
1879 self,
1880 connection: Connection,
1881 table_name: str,
1882 index_name: str,
1883 schema: Optional[str] = None,
1884 **kw: Any,
1885 ) -> bool:
1886 """Check the existence of a particular index name in the database.
1888 Given a :class:`_engine.Connection` object, a string
1889 ``table_name`` and string index name, return ``True`` if an index of
1890 the given name on the given table exists, ``False`` otherwise.
1892 The :class:`.DefaultDialect` implements this in terms of the
1893 :meth:`.Dialect.has_table` and :meth:`.Dialect.get_indexes` methods,
1894 however dialects can implement a more performant version.
1896 This is an internal dialect method. Applications should use
1897 :meth:`_engine.Inspector.has_index`.
1899 .. versionadded:: 1.4
1901 """
1903 raise NotImplementedError()
1905 def has_sequence(
1906 self,
1907 connection: Connection,
1908 sequence_name: str,
1909 schema: Optional[str] = None,
1910 **kw: Any,
1911 ) -> bool:
1912 """Check the existence of a particular sequence in the database.
1914 Given a :class:`_engine.Connection` object and a string
1915 `sequence_name`, return ``True`` if the given sequence exists in
1916 the database, ``False`` otherwise.
1918 This is an internal dialect method. Applications should use
1919 :meth:`_engine.Inspector.has_sequence`.
1920 """
1922 raise NotImplementedError()
1924 def has_schema(
1925 self, connection: Connection, schema_name: str, **kw: Any
1926 ) -> bool:
1927 """Check the existence of a particular schema name in the database.
1929 Given a :class:`_engine.Connection` object, a string
1930 ``schema_name``, return ``True`` if a schema of the
1931 given exists, ``False`` otherwise.
1933 The :class:`.DefaultDialect` implements this by checking
1934 the presence of ``schema_name`` among the schemas returned by
1935 :meth:`.Dialect.get_schema_names`,
1936 however dialects can implement a more performant version.
1938 This is an internal dialect method. Applications should use
1939 :meth:`_engine.Inspector.has_schema`.
1941 .. versionadded:: 2.0
1943 """
1945 raise NotImplementedError()
1947 def _get_server_version_info(self, connection: Connection) -> Any:
1948 """Retrieve the server version info from the given connection.
1950 This is used by the default implementation to populate the
1951 "server_version_info" attribute and is called exactly
1952 once upon first connect.
1954 """
1956 raise NotImplementedError()
1958 def _get_default_schema_name(self, connection: Connection) -> str:
1959 """Return the string name of the currently selected schema from
1960 the given connection.
1962 This is used by the default implementation to populate the
1963 "default_schema_name" attribute and is called exactly
1964 once upon first connect.
1966 """
1968 raise NotImplementedError()
1970 def do_begin(self, dbapi_connection: PoolProxiedConnection) -> None:
1971 """Provide an implementation of ``connection.begin()``, given a
1972 DB-API connection.
1974 The DBAPI has no dedicated "begin" method and it is expected
1975 that transactions are implicit. This hook is provided for those
1976 DBAPIs that might need additional help in this area.
1978 :param dbapi_connection: a DBAPI connection, typically
1979 proxied within a :class:`.ConnectionFairy`.
1981 """
1983 raise NotImplementedError()
1985 def do_rollback(self, dbapi_connection: PoolProxiedConnection) -> None:
1986 """Provide an implementation of ``connection.rollback()``, given
1987 a DB-API connection.
1989 :param dbapi_connection: a DBAPI connection, typically
1990 proxied within a :class:`.ConnectionFairy`.
1992 """
1994 raise NotImplementedError()
1996 def do_commit(self, dbapi_connection: PoolProxiedConnection) -> None:
1997 """Provide an implementation of ``connection.commit()``, given a
1998 DB-API connection.
2000 :param dbapi_connection: a DBAPI connection, typically
2001 proxied within a :class:`.ConnectionFairy`.
2003 """
2005 raise NotImplementedError()
2007 def do_terminate(self, dbapi_connection: DBAPIConnection) -> None:
2008 """Provide an implementation of ``connection.close()`` that tries as
2009 much as possible to not block, given a DBAPI
2010 connection.
2012 In the vast majority of cases this just calls .close(), however
2013 for some asyncio dialects may call upon different API features.
2015 This hook is called by the :class:`_pool.Pool`
2016 when a connection is being recycled or has been invalidated.
2018 .. versionadded:: 1.4.41
2020 """
2022 raise NotImplementedError()
2024 def do_close(self, dbapi_connection: DBAPIConnection) -> None:
2025 """Provide an implementation of ``connection.close()``, given a DBAPI
2026 connection.
2028 This hook is called by the :class:`_pool.Pool`
2029 when a connection has been
2030 detached from the pool, or is being returned beyond the normal
2031 capacity of the pool.
2033 """
2035 raise NotImplementedError()
2037 def _do_ping_w_event(self, dbapi_connection: DBAPIConnection) -> bool:
2038 raise NotImplementedError()
2040 def do_ping(self, dbapi_connection: DBAPIConnection) -> bool:
2041 """ping the DBAPI connection and return True if the connection is
2042 usable."""
2043 raise NotImplementedError()
2045 def do_set_input_sizes(
2046 self,
2047 cursor: DBAPICursor,
2048 list_of_tuples: _GenericSetInputSizesType,
2049 context: ExecutionContext,
2050 ) -> Any:
2051 """invoke the cursor.setinputsizes() method with appropriate arguments
2053 This hook is called if the :attr:`.Dialect.bind_typing` attribute is
2054 set to the
2055 :attr:`.BindTyping.SETINPUTSIZES` value.
2056 Parameter data is passed in a list of tuples (paramname, dbtype,
2057 sqltype), where ``paramname`` is the key of the parameter in the
2058 statement, ``dbtype`` is the DBAPI datatype and ``sqltype`` is the
2059 SQLAlchemy type. The order of tuples is in the correct parameter order.
2061 .. versionadded:: 1.4
2063 .. versionchanged:: 2.0 - setinputsizes mode is now enabled by
2064 setting :attr:`.Dialect.bind_typing` to
2065 :attr:`.BindTyping.SETINPUTSIZES`. Dialects which accept
2066 a ``use_setinputsizes`` parameter should set this value
2067 appropriately.
2070 """
2071 raise NotImplementedError()
2073 def create_xid(self) -> Any:
2074 """Create a two-phase transaction ID.
2076 This id will be passed to do_begin_twophase(),
2077 do_rollback_twophase(), do_commit_twophase(). Its format is
2078 unspecified.
2079 """
2081 raise NotImplementedError()
2083 def do_savepoint(self, connection: Connection, name: str) -> None:
2084 """Create a savepoint with the given name.
2086 :param connection: a :class:`_engine.Connection`.
2087 :param name: savepoint name.
2089 """
2091 raise NotImplementedError()
2093 def do_rollback_to_savepoint(
2094 self, connection: Connection, name: str
2095 ) -> None:
2096 """Rollback a connection to the named savepoint.
2098 :param connection: a :class:`_engine.Connection`.
2099 :param name: savepoint name.
2101 """
2103 raise NotImplementedError()
2105 def do_release_savepoint(self, connection: Connection, name: str) -> None:
2106 """Release the named savepoint on a connection.
2108 :param connection: a :class:`_engine.Connection`.
2109 :param name: savepoint name.
2110 """
2112 raise NotImplementedError()
2114 def do_begin_twophase(self, connection: Connection, xid: Any) -> None:
2115 """Begin a two phase transaction on the given connection.
2117 :param connection: a :class:`_engine.Connection`.
2118 :param xid: xid
2120 """
2122 raise NotImplementedError()
2124 def do_prepare_twophase(self, connection: Connection, xid: Any) -> None:
2125 """Prepare a two phase transaction on the given connection.
2127 :param connection: a :class:`_engine.Connection`.
2128 :param xid: xid
2130 """
2132 raise NotImplementedError()
2134 def do_rollback_twophase(
2135 self,
2136 connection: Connection,
2137 xid: Any,
2138 is_prepared: bool = True,
2139 recover: bool = False,
2140 ) -> None:
2141 """Rollback a two phase transaction on the given connection.
2143 :param connection: a :class:`_engine.Connection`.
2144 :param xid: xid
2145 :param is_prepared: whether or not
2146 :meth:`.TwoPhaseTransaction.prepare` was called.
2147 :param recover: if the recover flag was passed.
2149 """
2151 raise NotImplementedError()
2153 def do_commit_twophase(
2154 self,
2155 connection: Connection,
2156 xid: Any,
2157 is_prepared: bool = True,
2158 recover: bool = False,
2159 ) -> None:
2160 """Commit a two phase transaction on the given connection.
2163 :param connection: a :class:`_engine.Connection`.
2164 :param xid: xid
2165 :param is_prepared: whether or not
2166 :meth:`.TwoPhaseTransaction.prepare` was called.
2167 :param recover: if the recover flag was passed.
2169 """
2171 raise NotImplementedError()
2173 def do_recover_twophase(self, connection: Connection) -> List[Any]:
2174 """Recover list of uncommitted prepared two phase transaction
2175 identifiers on the given connection.
2177 :param connection: a :class:`_engine.Connection`.
2179 """
2181 raise NotImplementedError()
2183 def _deliver_insertmanyvalues_batches(
2184 self,
2185 connection: Connection,
2186 cursor: DBAPICursor,
2187 statement: str,
2188 parameters: _DBAPIMultiExecuteParams,
2189 generic_setinputsizes: Optional[_GenericSetInputSizesType],
2190 context: ExecutionContext,
2191 ) -> Iterator[_InsertManyValuesBatch]:
2192 """convert executemany parameters for an INSERT into an iterator
2193 of statement/single execute values, used by the insertmanyvalues
2194 feature.
2196 """
2197 raise NotImplementedError()
2199 def do_executemany(
2200 self,
2201 cursor: DBAPICursor,
2202 statement: str,
2203 parameters: _DBAPIMultiExecuteParams,
2204 context: Optional[ExecutionContext] = None,
2205 ) -> None:
2206 """Provide an implementation of ``cursor.executemany(statement,
2207 parameters)``."""
2209 raise NotImplementedError()
2211 def do_execute(
2212 self,
2213 cursor: DBAPICursor,
2214 statement: str,
2215 parameters: Optional[_DBAPISingleExecuteParams],
2216 context: Optional[ExecutionContext] = None,
2217 ) -> None:
2218 """Provide an implementation of ``cursor.execute(statement,
2219 parameters)``."""
2221 raise NotImplementedError()
2223 def do_execute_no_params(
2224 self,
2225 cursor: DBAPICursor,
2226 statement: str,
2227 context: Optional[ExecutionContext] = None,
2228 ) -> None:
2229 """Provide an implementation of ``cursor.execute(statement)``.
2231 The parameter collection should not be sent.
2233 """
2235 raise NotImplementedError()
2237 def is_disconnect(
2238 self,
2239 e: DBAPIModule.Error,
2240 connection: Optional[Union[PoolProxiedConnection, DBAPIConnection]],
2241 cursor: Optional[DBAPICursor],
2242 ) -> bool:
2243 """Return True if the given DB-API error indicates an invalid
2244 connection"""
2246 raise NotImplementedError()
2248 def connect(self, *cargs: Any, **cparams: Any) -> DBAPIConnection:
2249 r"""Establish a connection using this dialect's DBAPI.
2251 The default implementation of this method is::
2253 def connect(self, *cargs, **cparams):
2254 return self.dbapi.connect(*cargs, **cparams)
2256 The ``*cargs, **cparams`` parameters are generated directly
2257 from this dialect's :meth:`.Dialect.create_connect_args` method.
2259 This method may be used for dialects that need to perform programmatic
2260 per-connection steps when a new connection is procured from the
2261 DBAPI.
2264 :param \*cargs: positional parameters returned from the
2265 :meth:`.Dialect.create_connect_args` method
2267 :param \*\*cparams: keyword parameters returned from the
2268 :meth:`.Dialect.create_connect_args` method.
2270 :return: a DBAPI connection, typically from the :pep:`249` module
2271 level ``.connect()`` function.
2273 .. seealso::
2275 :meth:`.Dialect.create_connect_args`
2277 :meth:`.Dialect.on_connect`
2279 """
2280 raise NotImplementedError()
2282 def on_connect_url(self, url: URL) -> Optional[Callable[[Any], Any]]:
2283 """return a callable which sets up a newly created DBAPI connection.
2285 This method is a new hook that supersedes the
2286 :meth:`_engine.Dialect.on_connect` method when implemented by a
2287 dialect. When not implemented by a dialect, it invokes the
2288 :meth:`_engine.Dialect.on_connect` method directly to maintain
2289 compatibility with existing dialects. There is no deprecation
2290 for :meth:`_engine.Dialect.on_connect` expected.
2292 The callable should accept a single argument "conn" which is the
2293 DBAPI connection itself. The inner callable has no
2294 return value.
2296 E.g.::
2298 class MyDialect(default.DefaultDialect):
2299 # ...
2301 def on_connect_url(self, url):
2302 def do_on_connect(connection):
2303 connection.execute("SET SPECIAL FLAGS etc")
2305 return do_on_connect
2307 This is used to set dialect-wide per-connection options such as
2308 isolation modes, Unicode modes, etc.
2310 This method differs from :meth:`_engine.Dialect.on_connect` in that
2311 it is passed the :class:`_engine.URL` object that's relevant to the
2312 connect args. Normally the only way to get this is from the
2313 :meth:`_engine.Dialect.on_connect` hook is to look on the
2314 :class:`_engine.Engine` itself, however this URL object may have been
2315 replaced by plugins.
2317 .. note::
2319 The default implementation of
2320 :meth:`_engine.Dialect.on_connect_url` is to invoke the
2321 :meth:`_engine.Dialect.on_connect` method. Therefore if a dialect
2322 implements this method, the :meth:`_engine.Dialect.on_connect`
2323 method **will not be called** unless the overriding dialect calls
2324 it directly from here.
2326 .. versionadded:: 1.4.3 added :meth:`_engine.Dialect.on_connect_url`
2327 which normally calls into :meth:`_engine.Dialect.on_connect`.
2329 :param url: a :class:`_engine.URL` object representing the
2330 :class:`_engine.URL` that was passed to the
2331 :meth:`_engine.Dialect.create_connect_args` method.
2333 :return: a callable that accepts a single DBAPI connection as an
2334 argument, or None.
2336 .. seealso::
2338 :meth:`_engine.Dialect.on_connect`
2340 """
2341 return self.on_connect()
2343 def on_connect(self) -> Optional[Callable[[Any], None]]:
2344 """return a callable which sets up a newly created DBAPI connection.
2346 The callable should accept a single argument "conn" which is the
2347 DBAPI connection itself. The inner callable has no
2348 return value.
2350 E.g.::
2352 class MyDialect(default.DefaultDialect):
2353 # ...
2355 def on_connect(self):
2356 def do_on_connect(connection):
2357 connection.execute("SET SPECIAL FLAGS etc")
2359 return do_on_connect
2361 This is used to set dialect-wide per-connection options such as
2362 isolation modes, Unicode modes, etc.
2364 The "do_on_connect" callable is invoked by using the
2365 :meth:`_events.PoolEvents.connect` event
2366 hook, then unwrapping the DBAPI connection and passing it into the
2367 callable.
2369 .. versionchanged:: 1.4 the on_connect hook is no longer called twice
2370 for the first connection of a dialect. The on_connect hook is still
2371 called before the :meth:`_engine.Dialect.initialize` method however.
2373 .. versionchanged:: 1.4.3 the on_connect hook is invoked from a new
2374 method on_connect_url that passes the URL that was used to create
2375 the connect args. Dialects can implement on_connect_url instead
2376 of on_connect if they need the URL object that was used for the
2377 connection in order to get additional context.
2379 If None is returned, no event listener is generated.
2381 :return: a callable that accepts a single DBAPI connection as an
2382 argument, or None.
2384 .. seealso::
2386 :meth:`.Dialect.connect` - allows the DBAPI ``connect()`` sequence
2387 itself to be controlled.
2389 :meth:`.Dialect.on_connect_url` - supersedes
2390 :meth:`.Dialect.on_connect` to also receive the
2391 :class:`_engine.URL` object in context.
2393 """
2394 return None
2396 def reset_isolation_level(self, dbapi_connection: DBAPIConnection) -> None:
2397 """Given a DBAPI connection, revert its isolation to the default.
2399 Note that this is a dialect-level method which is used as part
2400 of the implementation of the :class:`_engine.Connection` and
2401 :class:`_engine.Engine`
2402 isolation level facilities; these APIs should be preferred for
2403 most typical use cases.
2405 .. seealso::
2407 :meth:`_engine.Connection.get_isolation_level`
2408 - view current level
2410 :attr:`_engine.Connection.default_isolation_level`
2411 - view default level
2413 :paramref:`.Connection.execution_options.isolation_level` -
2414 set per :class:`_engine.Connection` isolation level
2416 :paramref:`_sa.create_engine.isolation_level` -
2417 set per :class:`_engine.Engine` isolation level
2419 """
2421 raise NotImplementedError()
2423 def set_isolation_level(
2424 self, dbapi_connection: DBAPIConnection, level: IsolationLevel
2425 ) -> None:
2426 """Given a DBAPI connection, set its isolation level.
2428 Note that this is a dialect-level method which is used as part
2429 of the implementation of the :class:`_engine.Connection` and
2430 :class:`_engine.Engine`
2431 isolation level facilities; these APIs should be preferred for
2432 most typical use cases.
2434 If the dialect also implements the
2435 :meth:`.Dialect.get_isolation_level_values` method, then the given
2436 level is guaranteed to be one of the string names within that sequence,
2437 and the method will not need to anticipate a lookup failure.
2439 .. seealso::
2441 :meth:`_engine.Connection.get_isolation_level`
2442 - view current level
2444 :attr:`_engine.Connection.default_isolation_level`
2445 - view default level
2447 :paramref:`.Connection.execution_options.isolation_level` -
2448 set per :class:`_engine.Connection` isolation level
2450 :paramref:`_sa.create_engine.isolation_level` -
2451 set per :class:`_engine.Engine` isolation level
2453 """
2455 raise NotImplementedError()
2457 def get_isolation_level(
2458 self, dbapi_connection: DBAPIConnection
2459 ) -> IsolationLevel:
2460 """Given a DBAPI connection, return its isolation level.
2462 When working with a :class:`_engine.Connection` object,
2463 the corresponding
2464 DBAPI connection may be procured using the
2465 :attr:`_engine.Connection.connection` accessor.
2467 Note that this is a dialect-level method which is used as part
2468 of the implementation of the :class:`_engine.Connection` and
2469 :class:`_engine.Engine` isolation level facilities;
2470 these APIs should be preferred for most typical use cases.
2473 .. seealso::
2475 :meth:`_engine.Connection.get_isolation_level`
2476 - view current level
2478 :attr:`_engine.Connection.default_isolation_level`
2479 - view default level
2481 :paramref:`.Connection.execution_options.isolation_level` -
2482 set per :class:`_engine.Connection` isolation level
2484 :paramref:`_sa.create_engine.isolation_level` -
2485 set per :class:`_engine.Engine` isolation level
2488 """
2490 raise NotImplementedError()
2492 def detect_autocommit_setting(self, dbapi_conn: DBAPIConnection) -> bool:
2493 """Detect the current autocommit setting for a DBAPI connection.
2495 :param dbapi_connection: a DBAPI connection object
2496 :return: True if autocommit is enabled, False if disabled
2497 :rtype: bool
2499 This method inspects the given DBAPI connection to determine
2500 whether autocommit mode is currently enabled. The specific
2501 mechanism for detecting autocommit varies by database dialect
2502 and DBAPI driver, however it should be done **without** network
2503 round trips.
2505 .. note::
2507 Not all dialects support autocommit detection. Dialects
2508 that do not support this feature will raise
2509 :exc:`NotImplementedError`.
2511 """
2512 raise NotImplementedError(
2513 "This dialect cannot detect autocommit on a DBAPI connection"
2514 )
2516 def get_default_isolation_level(
2517 self, dbapi_conn: DBAPIConnection
2518 ) -> IsolationLevel:
2519 """Given a DBAPI connection, return its isolation level, or
2520 a default isolation level if one cannot be retrieved.
2522 This method may only raise NotImplementedError and
2523 **must not raise any other exception**, as it is used implicitly upon
2524 first connect.
2526 The method **must return a value** for a dialect that supports
2527 isolation level settings, as this level is what will be reverted
2528 towards when a per-connection isolation level change is made.
2530 The method defaults to using the :meth:`.Dialect.get_isolation_level`
2531 method unless overridden by a dialect.
2533 .. versionadded:: 1.3.22
2535 """
2536 raise NotImplementedError()
2538 def get_isolation_level_values(
2539 self, dbapi_conn: DBAPIConnection
2540 ) -> Sequence[IsolationLevel]:
2541 """return a sequence of string isolation level names that are accepted
2542 by this dialect.
2544 The available names should use the following conventions:
2546 * use UPPERCASE names. isolation level methods will accept lowercase
2547 names but these are normalized into UPPERCASE before being passed
2548 along to the dialect.
2549 * separate words should be separated by spaces, not underscores, e.g.
2550 ``REPEATABLE READ``. isolation level names will have underscores
2551 converted to spaces before being passed along to the dialect.
2552 * The names for the four standard isolation names to the extent that
2553 they are supported by the backend should be ``READ UNCOMMITTED``,
2554 ``READ COMMITTED``, ``REPEATABLE READ``, ``SERIALIZABLE``
2555 * if the dialect supports an autocommit option it should be provided
2556 using the isolation level name ``AUTOCOMMIT``.
2557 * Other isolation modes may also be present, provided that they
2558 are named in UPPERCASE and use spaces not underscores.
2560 This function is used so that the default dialect can check that
2561 a given isolation level parameter is valid, else raises an
2562 :class:`_exc.ArgumentError`.
2564 A DBAPI connection is passed to the method, in the unlikely event that
2565 the dialect needs to interrogate the connection itself to determine
2566 this list, however it is expected that most backends will return
2567 a hardcoded list of values. If the dialect supports "AUTOCOMMIT",
2568 that value should also be present in the sequence returned.
2570 The method raises ``NotImplementedError`` by default. If a dialect
2571 does not implement this method, then the default dialect will not
2572 perform any checking on a given isolation level value before passing
2573 it onto the :meth:`.Dialect.set_isolation_level` method. This is
2574 to allow backwards-compatibility with third party dialects that may
2575 not yet be implementing this method.
2577 .. versionadded:: 2.0
2579 """
2580 raise NotImplementedError()
2582 def _assert_and_set_isolation_level(
2583 self, dbapi_conn: DBAPIConnection, level: IsolationLevel
2584 ) -> None:
2585 raise NotImplementedError()
2587 @classmethod
2588 def get_dialect_cls(cls, url: URL) -> Type[Dialect]:
2589 """Given a URL, return the :class:`.Dialect` that will be used.
2591 This is a hook that allows an external plugin to provide functionality
2592 around an existing dialect, by allowing the plugin to be loaded
2593 from the url based on an entrypoint, and then the plugin returns
2594 the actual dialect to be used.
2596 By default this just returns the cls.
2598 """
2599 return cls
2601 @classmethod
2602 def get_async_dialect_cls(cls, url: URL) -> Type[Dialect]:
2603 """Given a URL, return the :class:`.Dialect` that will be used by
2604 an async engine.
2606 By default this is an alias of :meth:`.Dialect.get_dialect_cls` and
2607 just returns the cls. It may be used if a dialect provides
2608 both a sync and async version under the same name, like the
2609 ``psycopg`` driver.
2611 .. versionadded:: 2
2613 .. seealso::
2615 :meth:`.Dialect.get_dialect_cls`
2617 """
2618 return cls.get_dialect_cls(url)
2620 @classmethod
2621 def load_provisioning(cls) -> None:
2622 """set up the provision.py module for this dialect.
2624 For dialects that include a provision.py module that sets up
2625 provisioning followers, this method should initiate that process.
2627 A typical implementation would be::
2629 @classmethod
2630 def load_provisioning(cls):
2631 __import__("mydialect.provision")
2633 The default method assumes a module named ``provision.py`` inside
2634 the owning package of the current dialect, based on the ``__module__``
2635 attribute::
2637 @classmethod
2638 def load_provisioning(cls):
2639 package = ".".join(cls.__module__.split(".")[0:-1])
2640 try:
2641 __import__(package + ".provision")
2642 except ImportError:
2643 pass
2645 .. versionadded:: 1.3.14
2647 """
2649 @classmethod
2650 def engine_created(cls, engine: Engine) -> None:
2651 """A convenience hook called before returning the final
2652 :class:`_engine.Engine`.
2654 If the dialect returned a different class from the
2655 :meth:`.get_dialect_cls`
2656 method, then the hook is called on both classes, first on
2657 the dialect class returned by the :meth:`.get_dialect_cls` method and
2658 then on the class on which the method was called.
2660 The hook should be used by dialects and/or wrappers to apply special
2661 events to the engine or its components. In particular, it allows
2662 a dialect-wrapping class to apply dialect-level events.
2664 """
2666 def get_driver_connection(self, connection: DBAPIConnection) -> Any:
2667 """Returns the connection object as returned by the external driver
2668 package.
2670 For normal dialects that use a DBAPI compliant driver this call
2671 will just return the ``connection`` passed as argument.
2672 For dialects that instead adapt a non DBAPI compliant driver, like
2673 when adapting an asyncio driver, this call will return the
2674 connection-like object as returned by the driver.
2676 .. versionadded:: 1.4.24
2678 """
2679 raise NotImplementedError()
2681 def set_engine_execution_options(
2682 self, engine: Engine, opts: CoreExecuteOptionsParameter
2683 ) -> None:
2684 """Establish execution options for a given engine.
2686 This is implemented by :class:`.DefaultDialect` to establish
2687 event hooks for new :class:`.Connection` instances created
2688 by the given :class:`.Engine` which will then invoke the
2689 :meth:`.Dialect.set_connection_execution_options` method for that
2690 connection.
2692 """
2693 raise NotImplementedError()
2695 def set_connection_execution_options(
2696 self, connection: Connection, opts: CoreExecuteOptionsParameter
2697 ) -> None:
2698 """Establish execution options for a given connection.
2700 This is implemented by :class:`.DefaultDialect` in order to implement
2701 the :paramref:`_engine.Connection.execution_options.isolation_level`
2702 execution option. Dialects can intercept various execution options
2703 which may need to modify state on a particular DBAPI connection.
2705 .. versionadded:: 1.4
2707 """
2708 raise NotImplementedError()
2710 def get_dialect_pool_class(self, url: URL) -> Type[Pool]:
2711 """return a Pool class to use for a given URL"""
2712 raise NotImplementedError()
2714 def validate_identifier(self, ident: str) -> None:
2715 """Validates an identifier name, raising an exception if invalid"""
2718class CreateEnginePlugin:
2719 """A set of hooks intended to augment the construction of an
2720 :class:`_engine.Engine` object based on entrypoint names in a URL.
2722 The purpose of :class:`_engine.CreateEnginePlugin` is to allow third-party
2723 systems to apply engine, pool and dialect level event listeners without
2724 the need for the target application to be modified; instead, the plugin
2725 names can be added to the database URL. Target applications for
2726 :class:`_engine.CreateEnginePlugin` include:
2728 * connection and SQL performance tools, e.g. which use events to track
2729 number of checkouts and/or time spent with statements
2731 * connectivity plugins such as proxies
2733 A rudimentary :class:`_engine.CreateEnginePlugin` that attaches a logger
2734 to an :class:`_engine.Engine` object might look like::
2737 import logging
2739 from sqlalchemy.engine import CreateEnginePlugin
2740 from sqlalchemy import event
2743 class LogCursorEventsPlugin(CreateEnginePlugin):
2744 def __init__(self, url, kwargs):
2745 # consume the parameter "log_cursor_logging_name" from the
2746 # URL query
2747 logging_name = url.query.get(
2748 "log_cursor_logging_name", "log_cursor"
2749 )
2751 self.log = logging.getLogger(logging_name)
2753 def update_url(self, url):
2754 "update the URL to one that no longer includes our parameters"
2755 return url.difference_update_query(["log_cursor_logging_name"])
2757 def engine_created(self, engine):
2758 "attach an event listener after the new Engine is constructed"
2759 event.listen(engine, "before_cursor_execute", self._log_event)
2761 def _log_event(
2762 self,
2763 conn,
2764 cursor,
2765 statement,
2766 parameters,
2767 context,
2768 executemany,
2769 ):
2771 self.log.info("Plugin logged cursor event: %s", statement)
2773 Plugins are registered using entry points in a similar way as that
2774 of dialects::
2776 entry_points = {
2777 "sqlalchemy.plugins": [
2778 "log_cursor_plugin = myapp.plugins:LogCursorEventsPlugin"
2779 ]
2780 }
2782 A plugin that uses the above names would be invoked from a database
2783 URL as in::
2785 from sqlalchemy import create_engine
2787 engine = create_engine(
2788 "mysql+pymysql://scott:tiger@localhost/test?"
2789 "plugin=log_cursor_plugin&log_cursor_logging_name=mylogger"
2790 )
2792 The ``plugin`` URL parameter supports multiple instances, so that a URL
2793 may specify multiple plugins; they are loaded in the order stated
2794 in the URL::
2796 engine = create_engine(
2797 "mysql+pymysql://scott:tiger@localhost/test?"
2798 "plugin=plugin_one&plugin=plugin_twp&plugin=plugin_three"
2799 )
2801 The plugin names may also be passed directly to :func:`_sa.create_engine`
2802 using the :paramref:`_sa.create_engine.plugins` argument::
2804 engine = create_engine(
2805 "mysql+pymysql://scott:tiger@localhost/test", plugins=["myplugin"]
2806 )
2808 .. versionadded:: 1.2.3 plugin names can also be specified
2809 to :func:`_sa.create_engine` as a list
2811 A plugin may consume plugin-specific arguments from the
2812 :class:`_engine.URL` object as well as the ``kwargs`` dictionary, which is
2813 the dictionary of arguments passed to the :func:`_sa.create_engine`
2814 call. "Consuming" these arguments includes that they must be removed
2815 when the plugin initializes, so that the arguments are not passed along
2816 to the :class:`_engine.Dialect` constructor, where they will raise an
2817 :class:`_exc.ArgumentError` because they are not known by the dialect.
2819 As of version 1.4 of SQLAlchemy, arguments should continue to be consumed
2820 from the ``kwargs`` dictionary directly, by removing the values with a
2821 method such as ``dict.pop``. Arguments from the :class:`_engine.URL` object
2822 should be consumed by implementing the
2823 :meth:`_engine.CreateEnginePlugin.update_url` method, returning a new copy
2824 of the :class:`_engine.URL` with plugin-specific parameters removed::
2826 class MyPlugin(CreateEnginePlugin):
2827 def __init__(self, url, kwargs):
2828 self.my_argument_one = url.query["my_argument_one"]
2829 self.my_argument_two = url.query["my_argument_two"]
2830 self.my_argument_three = kwargs.pop("my_argument_three", None)
2832 def update_url(self, url):
2833 return url.difference_update_query(
2834 ["my_argument_one", "my_argument_two"]
2835 )
2837 Arguments like those illustrated above would be consumed from a
2838 :func:`_sa.create_engine` call such as::
2840 from sqlalchemy import create_engine
2842 engine = create_engine(
2843 "mysql+pymysql://scott:tiger@localhost/test?"
2844 "plugin=myplugin&my_argument_one=foo&my_argument_two=bar",
2845 my_argument_three="bat",
2846 )
2848 .. versionchanged:: 1.4
2850 The :class:`_engine.URL` object is now immutable; a
2851 :class:`_engine.CreateEnginePlugin` that needs to alter the
2852 :class:`_engine.URL` should implement the newly added
2853 :meth:`_engine.CreateEnginePlugin.update_url` method, which
2854 is invoked after the plugin is constructed.
2856 For migration, construct the plugin in the following way, checking
2857 for the existence of the :meth:`_engine.CreateEnginePlugin.update_url`
2858 method to detect which version is running::
2860 class MyPlugin(CreateEnginePlugin):
2861 def __init__(self, url, kwargs):
2862 if hasattr(CreateEnginePlugin, "update_url"):
2863 # detect the 1.4 API
2864 self.my_argument_one = url.query["my_argument_one"]
2865 self.my_argument_two = url.query["my_argument_two"]
2866 else:
2867 # detect the 1.3 and earlier API - mutate the
2868 # URL directly
2869 self.my_argument_one = url.query.pop("my_argument_one")
2870 self.my_argument_two = url.query.pop("my_argument_two")
2872 self.my_argument_three = kwargs.pop("my_argument_three", None)
2874 def update_url(self, url):
2875 # this method is only called in the 1.4 version
2876 return url.difference_update_query(
2877 ["my_argument_one", "my_argument_two"]
2878 )
2880 .. seealso::
2882 :ref:`change_5526` - overview of the :class:`_engine.URL` change which
2883 also includes notes regarding :class:`_engine.CreateEnginePlugin`.
2886 When the engine creation process completes and produces the
2887 :class:`_engine.Engine` object, it is again passed to the plugin via the
2888 :meth:`_engine.CreateEnginePlugin.engine_created` hook. In this hook, additional
2889 changes can be made to the engine, most typically involving setup of
2890 events (e.g. those defined in :ref:`core_event_toplevel`).
2892 """ # noqa: E501
2894 def __init__(self, url: URL, kwargs: Dict[str, Any]):
2895 """Construct a new :class:`.CreateEnginePlugin`.
2897 The plugin object is instantiated individually for each call
2898 to :func:`_sa.create_engine`. A single :class:`_engine.
2899 Engine` will be
2900 passed to the :meth:`.CreateEnginePlugin.engine_created` method
2901 corresponding to this URL.
2903 :param url: the :class:`_engine.URL` object. The plugin may inspect
2904 the :class:`_engine.URL` for arguments. Arguments used by the
2905 plugin should be removed, by returning an updated :class:`_engine.URL`
2906 from the :meth:`_engine.CreateEnginePlugin.update_url` method.
2908 .. versionchanged:: 1.4
2910 The :class:`_engine.URL` object is now immutable, so a
2911 :class:`_engine.CreateEnginePlugin` that needs to alter the
2912 :class:`_engine.URL` object should implement the
2913 :meth:`_engine.CreateEnginePlugin.update_url` method.
2915 :param kwargs: The keyword arguments passed to
2916 :func:`_sa.create_engine`.
2918 """
2919 self.url = url
2921 def update_url(self, url: URL) -> URL:
2922 """Update the :class:`_engine.URL`.
2924 A new :class:`_engine.URL` should be returned. This method is
2925 typically used to consume configuration arguments from the
2926 :class:`_engine.URL` which must be removed, as they will not be
2927 recognized by the dialect. The
2928 :meth:`_engine.URL.difference_update_query` method is available
2929 to remove these arguments. See the docstring at
2930 :class:`_engine.CreateEnginePlugin` for an example.
2933 .. versionadded:: 1.4
2935 """
2936 raise NotImplementedError()
2938 def handle_dialect_kwargs(
2939 self, dialect_cls: Type[Dialect], dialect_args: Dict[str, Any]
2940 ) -> None:
2941 """parse and modify dialect kwargs"""
2943 def handle_pool_kwargs(
2944 self, pool_cls: Type[Pool], pool_args: Dict[str, Any]
2945 ) -> None:
2946 """parse and modify pool kwargs"""
2948 def engine_created(self, engine: Engine) -> None:
2949 """Receive the :class:`_engine.Engine`
2950 object when it is fully constructed.
2952 The plugin may make additional changes to the engine, such as
2953 registering engine or connection pool events.
2955 """
2958class ExecutionContext:
2959 """A messenger object for a Dialect that corresponds to a single
2960 execution.
2962 """
2964 engine: Engine
2965 """engine which the Connection is associated with"""
2967 connection: Connection
2968 """Connection object which can be freely used by default value
2969 generators to execute SQL. This Connection should reference the
2970 same underlying connection/transactional resources of
2971 root_connection."""
2973 root_connection: Connection
2974 """Connection object which is the source of this ExecutionContext."""
2976 dialect: Dialect
2977 """dialect which created this ExecutionContext."""
2979 cursor: DBAPICursor
2980 """DB-API cursor procured from the connection"""
2982 compiled: Optional[Compiled]
2983 """if passed to constructor, sqlalchemy.engine.base.Compiled object
2984 being executed"""
2986 statement: str
2987 """string version of the statement to be executed. Is either
2988 passed to the constructor, or must be created from the
2989 sql.Compiled object by the time pre_exec() has completed."""
2991 invoked_statement: Optional[Executable]
2992 """The Executable statement object that was given in the first place.
2994 This should be structurally equivalent to compiled.statement, but not
2995 necessarily the same object as in a caching scenario the compiled form
2996 will have been extracted from the cache.
2998 """
3000 parameters: _AnyMultiExecuteParams
3001 """bind parameters passed to the execute() or exec_driver_sql() methods.
3003 These are always stored as a list of parameter entries. A single-element
3004 list corresponds to a ``cursor.execute()`` call and a multiple-element
3005 list corresponds to ``cursor.executemany()``, except in the case
3006 of :attr:`.ExecuteStyle.INSERTMANYVALUES` which will use
3007 ``cursor.execute()`` one or more times.
3009 """
3011 no_parameters: bool
3012 """True if the execution style does not use parameters"""
3014 isinsert: bool
3015 """True if the statement is an INSERT."""
3017 isupdate: bool
3018 """True if the statement is an UPDATE."""
3020 execute_style: ExecuteStyle
3021 """the style of DBAPI cursor method that will be used to execute
3022 a statement.
3024 .. versionadded:: 2.0
3026 """
3028 executemany: bool
3029 """True if the context has a list of more than one parameter set.
3031 Historically this attribute links to whether ``cursor.execute()`` or
3032 ``cursor.executemany()`` will be used. It also can now mean that
3033 "insertmanyvalues" may be used which indicates one or more
3034 ``cursor.execute()`` calls.
3036 """
3038 prefetch_cols: util.generic_fn_descriptor[Optional[Sequence[Column[Any]]]]
3039 """a list of Column objects for which a client-side default
3040 was fired off. Applies to inserts and updates."""
3042 postfetch_cols: util.generic_fn_descriptor[Optional[Sequence[Column[Any]]]]
3043 """a list of Column objects for which a server-side default or
3044 inline SQL expression value was fired off. Applies to inserts
3045 and updates."""
3047 execution_options: _ExecuteOptions
3048 """Execution options associated with the current statement execution"""
3050 @classmethod
3051 def _init_ddl(
3052 cls,
3053 dialect: Dialect,
3054 connection: Connection,
3055 dbapi_connection: PoolProxiedConnection,
3056 execution_options: _ExecuteOptions,
3057 compiled_ddl: DDLCompiler,
3058 ) -> ExecutionContext:
3059 raise NotImplementedError()
3061 @classmethod
3062 def _init_compiled(
3063 cls,
3064 dialect: Dialect,
3065 connection: Connection,
3066 dbapi_connection: PoolProxiedConnection,
3067 execution_options: _ExecuteOptions,
3068 compiled: SQLCompiler,
3069 parameters: _CoreMultiExecuteParams,
3070 invoked_statement: Executable,
3071 extracted_parameters: Optional[Sequence[BindParameter[Any]]],
3072 cache_hit: CacheStats = CacheStats.CACHING_DISABLED,
3073 ) -> ExecutionContext:
3074 raise NotImplementedError()
3076 @classmethod
3077 def _init_statement(
3078 cls,
3079 dialect: Dialect,
3080 connection: Connection,
3081 dbapi_connection: PoolProxiedConnection,
3082 execution_options: _ExecuteOptions,
3083 statement: str,
3084 parameters: _DBAPIMultiExecuteParams,
3085 ) -> ExecutionContext:
3086 raise NotImplementedError()
3088 @classmethod
3089 def _init_default(
3090 cls,
3091 dialect: Dialect,
3092 connection: Connection,
3093 dbapi_connection: PoolProxiedConnection,
3094 execution_options: _ExecuteOptions,
3095 ) -> ExecutionContext:
3096 raise NotImplementedError()
3098 def _exec_default(
3099 self,
3100 column: Optional[Column[Any]],
3101 default: DefaultGenerator,
3102 type_: Optional[TypeEngine[Any]],
3103 ) -> Any:
3104 raise NotImplementedError()
3106 def _prepare_set_input_sizes(
3107 self,
3108 ) -> Optional[List[Tuple[str, Any, TypeEngine[Any]]]]:
3109 raise NotImplementedError()
3111 def _get_cache_stats(self) -> str:
3112 raise NotImplementedError()
3114 def _setup_result_proxy(self) -> CursorResult[Any]:
3115 raise NotImplementedError()
3117 def fire_sequence(self, seq: Sequence_SchemaItem, type_: Integer) -> int:
3118 """given a :class:`.Sequence`, invoke it and return the next int
3119 value"""
3120 raise NotImplementedError()
3122 def create_cursor(self) -> DBAPICursor:
3123 """Return a new cursor generated from this ExecutionContext's
3124 connection.
3126 Some dialects may wish to change the behavior of
3127 connection.cursor(), such as postgresql which may return a PG
3128 "server side" cursor.
3129 """
3131 raise NotImplementedError()
3133 def pre_exec(self) -> None:
3134 """Called before an execution of a compiled statement.
3136 If a compiled statement was passed to this ExecutionContext,
3137 the `statement` and `parameters` datamembers must be
3138 initialized after this statement is complete.
3139 """
3141 raise NotImplementedError()
3143 def get_out_parameter_values(
3144 self, out_param_names: Sequence[str]
3145 ) -> Sequence[Any]:
3146 """Return a sequence of OUT parameter values from a cursor.
3148 For dialects that support OUT parameters, this method will be called
3149 when there is a :class:`.SQLCompiler` object which has the
3150 :attr:`.SQLCompiler.has_out_parameters` flag set. This flag in turn
3151 will be set to True if the statement itself has :class:`.BindParameter`
3152 objects that have the ``.isoutparam`` flag set which are consumed by
3153 the :meth:`.SQLCompiler.visit_bindparam` method. If the dialect
3154 compiler produces :class:`.BindParameter` objects with ``.isoutparam``
3155 set which are not handled by :meth:`.SQLCompiler.visit_bindparam`, it
3156 should set this flag explicitly.
3158 The list of names that were rendered for each bound parameter
3159 is passed to the method. The method should then return a sequence of
3160 values corresponding to the list of parameter objects. Unlike in
3161 previous SQLAlchemy versions, the values can be the **raw values** from
3162 the DBAPI; the execution context will apply the appropriate type
3163 handler based on what's present in self.compiled.binds and update the
3164 values. The processed dictionary will then be made available via the
3165 ``.out_parameters`` collection on the result object. Note that
3166 SQLAlchemy 1.4 has multiple kinds of result object as part of the 2.0
3167 transition.
3169 .. versionadded:: 1.4 - added
3170 :meth:`.ExecutionContext.get_out_parameter_values`, which is invoked
3171 automatically by the :class:`.DefaultExecutionContext` when there
3172 are :class:`.BindParameter` objects with the ``.isoutparam`` flag
3173 set. This replaces the practice of setting out parameters within
3174 the now-removed ``get_result_proxy()`` method.
3176 """
3177 raise NotImplementedError()
3179 def post_exec(self) -> None:
3180 """Called after the execution of a compiled statement.
3182 If a compiled statement was passed to this ExecutionContext,
3183 the `last_insert_ids`, `last_inserted_params`, etc.
3184 datamembers should be available after this method completes.
3185 """
3187 raise NotImplementedError()
3189 def handle_dbapi_exception(self, e: BaseException) -> None:
3190 """Receive a DBAPI exception which occurred upon execute, result
3191 fetch, etc."""
3193 raise NotImplementedError()
3195 def lastrow_has_defaults(self) -> bool:
3196 """Return True if the last INSERT or UPDATE row contained
3197 inlined or database-side defaults.
3198 """
3200 raise NotImplementedError()
3202 def get_rowcount(self) -> Optional[int]:
3203 """Return the DBAPI ``cursor.rowcount`` value, or in some
3204 cases an interpreted value.
3206 See :attr:`_engine.CursorResult.rowcount` for details on this.
3208 """
3210 raise NotImplementedError()
3212 def fetchall_for_returning(self, cursor: DBAPICursor) -> Sequence[Any]:
3213 """For a RETURNING result, deliver cursor.fetchall() from the
3214 DBAPI cursor.
3216 This is a dialect-specific hook for dialects that have special
3217 considerations when calling upon the rows delivered for a
3218 "RETURNING" statement. Default implementation is
3219 ``cursor.fetchall()``.
3221 This hook is currently used only by the :term:`insertmanyvalues`
3222 feature. Dialects that don't set ``use_insertmanyvalues=True``
3223 don't need to consider this hook.
3225 .. versionadded:: 2.0.10
3227 """
3228 raise NotImplementedError()
3231class ConnectionEventsTarget(EventTarget):
3232 """An object which can accept events from :class:`.ConnectionEvents`.
3234 Includes :class:`_engine.Connection` and :class:`_engine.Engine`.
3236 .. versionadded:: 2.0
3238 """
3240 dispatch: dispatcher[ConnectionEventsTarget]
3243Connectable = ConnectionEventsTarget
3246class ExceptionContext:
3247 """Encapsulate information about an error condition in progress.
3249 This object exists solely to be passed to the
3250 :meth:`_events.DialectEvents.handle_error` event,
3251 supporting an interface that
3252 can be extended without backwards-incompatibility.
3255 """
3257 __slots__ = ()
3259 dialect: Dialect
3260 """The :class:`_engine.Dialect` in use.
3262 This member is present for all invocations of the event hook.
3264 .. versionadded:: 2.0
3266 """
3268 connection: Optional[Connection]
3269 """The :class:`_engine.Connection` in use during the exception.
3271 This member is present, except in the case of a failure when
3272 first connecting.
3274 .. seealso::
3276 :attr:`.ExceptionContext.engine`
3279 """
3281 engine: Optional[Engine]
3282 """The :class:`_engine.Engine` in use during the exception.
3284 This member is present in all cases except for when handling an error
3285 within the connection pool "pre-ping" process.
3287 """
3289 cursor: Optional[DBAPICursor]
3290 """The DBAPI cursor object.
3292 May be None.
3294 """
3296 statement: Optional[str]
3297 """String SQL statement that was emitted directly to the DBAPI.
3299 May be None.
3301 """
3303 parameters: Optional[_DBAPIAnyExecuteParams]
3304 """Parameter collection that was emitted directly to the DBAPI.
3306 May be None.
3308 """
3310 original_exception: BaseException
3311 """The exception object which was caught.
3313 This member is always present.
3315 """
3317 sqlalchemy_exception: Optional[StatementError]
3318 """The :class:`sqlalchemy.exc.StatementError` which wraps the original,
3319 and will be raised if exception handling is not circumvented by the event.
3321 May be None, as not all exception types are wrapped by SQLAlchemy.
3322 For DBAPI-level exceptions that subclass the dbapi's Error class, this
3323 field will always be present.
3325 """
3327 chained_exception: Optional[BaseException]
3328 """The exception that was returned by the previous handler in the
3329 exception chain, if any.
3331 If present, this exception will be the one ultimately raised by
3332 SQLAlchemy unless a subsequent handler replaces it.
3334 May be None.
3336 """
3338 execution_context: Optional[ExecutionContext]
3339 """The :class:`.ExecutionContext` corresponding to the execution
3340 operation in progress.
3342 This is present for statement execution operations, but not for
3343 operations such as transaction begin/end. It also is not present when
3344 the exception was raised before the :class:`.ExecutionContext`
3345 could be constructed.
3347 Note that the :attr:`.ExceptionContext.statement` and
3348 :attr:`.ExceptionContext.parameters` members may represent a
3349 different value than that of the :class:`.ExecutionContext`,
3350 potentially in the case where a
3351 :meth:`_events.ConnectionEvents.before_cursor_execute` event or similar
3352 modified the statement/parameters to be sent.
3354 May be None.
3356 """
3358 is_disconnect: bool
3359 """Represent whether the exception as occurred represents a "disconnect"
3360 condition.
3362 This flag will always be True or False within the scope of the
3363 :meth:`_events.DialectEvents.handle_error` handler.
3365 SQLAlchemy will defer to this flag in order to determine whether or not
3366 the connection should be invalidated subsequently. That is, by
3367 assigning to this flag, a "disconnect" event which then results in
3368 a connection and pool invalidation can be invoked or prevented by
3369 changing this flag.
3372 .. note:: The pool "pre_ping" handler enabled using the
3373 :paramref:`_sa.create_engine.pool_pre_ping` parameter does **not**
3374 consult this event before deciding if the "ping" returned false,
3375 as opposed to receiving an unhandled error. For this use case, the
3376 :ref:`legacy recipe based on engine_connect() may be used
3377 <pool_disconnects_pessimistic_custom>`. A future API allow more
3378 comprehensive customization of the "disconnect" detection mechanism
3379 across all functions.
3381 """
3383 invalidate_pool_on_disconnect: bool
3384 """Represent whether all connections in the pool should be invalidated
3385 when a "disconnect" condition is in effect.
3387 Setting this flag to False within the scope of the
3388 :meth:`_events.DialectEvents.handle_error`
3389 event will have the effect such
3390 that the full collection of connections in the pool will not be
3391 invalidated during a disconnect; only the current connection that is the
3392 subject of the error will actually be invalidated.
3394 The purpose of this flag is for custom disconnect-handling schemes where
3395 the invalidation of other connections in the pool is to be performed
3396 based on other conditions, or even on a per-connection basis.
3398 """
3400 is_pre_ping: bool
3401 """Indicates if this error is occurring within the "pre-ping" step
3402 performed when :paramref:`_sa.create_engine.pool_pre_ping` is set to
3403 ``True``. In this mode, the :attr:`.ExceptionContext.engine` attribute
3404 will be ``None``. The dialect in use is accessible via the
3405 :attr:`.ExceptionContext.dialect` attribute.
3407 .. versionadded:: 2.0.5
3409 """
3412class AdaptedConnection:
3413 """Interface of an adapted connection object to support the DBAPI protocol.
3415 Used by asyncio dialects to provide a sync-style pep-249 facade on top
3416 of the asyncio connection/cursor API provided by the driver.
3418 .. versionadded:: 1.4.24
3420 """
3422 __slots__ = ("_connection",)
3424 _connection: AsyncIODBAPIConnection
3426 @property
3427 def driver_connection(self) -> Any:
3428 """The connection object as returned by the driver after a connect."""
3429 return self._connection
3431 def run_async(self, fn: Callable[[Any], Awaitable[_T]]) -> _T:
3432 """Run the awaitable returned by the given function, which is passed
3433 the raw asyncio driver connection.
3435 This is used to invoke awaitable-only methods on the driver connection
3436 within the context of a "synchronous" method, like a connection
3437 pool event handler.
3439 E.g.::
3441 engine = create_async_engine(...)
3444 @event.listens_for(engine.sync_engine, "connect")
3445 def register_custom_types(
3446 dbapi_connection, # ...
3447 ):
3448 dbapi_connection.run_async(
3449 lambda connection: connection.set_type_codec(
3450 "MyCustomType", encoder, decoder, ...
3451 )
3452 )
3454 .. versionadded:: 1.4.30
3456 .. seealso::
3458 :ref:`asyncio_events_run_async`
3460 """
3461 return await_only(fn(self._connection))
3463 def __repr__(self) -> str:
3464 return "<AdaptedConnection %s>" % self._connection