2.1 Changelog

2.1.0b1

no release date

orm

  • [orm] [feature]

    The relationship.back_populates argument to relationship() may now be passed as a Python callable, which resolves to either the direct linked ORM attribute, or a string value as before. ORM attributes are also accepted directly by relationship.back_populates. This change allows type checkers and IDEs to confirm the argument for relationship.back_populates is valid. Thanks to Priyanshu Parikh for the help on suggesting and helping to implement this feature.

    See also

    ORM Relationship allows callable for back_populates

    References: #10050

  • [orm] [usecase]

    The Session.flush.objects parameter is now deprecated.

    References: #10816

  • [orm] [usecase]

    Added the utility method Session.merge_all() and Session.delete_all() that operate on a collection of instances.

    References: #11776

  • [orm] [change]

    The first_init ORM event has been removed. This event was non-functional throughout the 1.4 and 2.0 series and could not be invoked without raising an internal error, so it is not expected that there is any real-world use of this event hook.

    References: #10500

  • [orm] [change]

    Removed legacy signatures dating back to 0.9 release from the SessionEvents.after_bulk_update() and SessionEvents.after_bulk_delete().

    References: #10721

  • [orm] [change]

    A sweep through class and function names in the ORM renames many classes and functions that have no intent of public visibility to be underscored. This is to reduce ambiguity as to which APIs are intended to be targeted by third party applications and extensions. Third parties are encouraged to propose new public APIs in Discussions to the extent they are needed to replace those that have been clarified as private.

    References: #10497

  • [orm] [changed]

    The “non primary” mapper feature, long deprecated in SQLAlchemy since version 1.3, has been removed. The sole use case for “non primary” mappers was that of using relationship() to link to a mapped class against an alternative selectable; this use case is now suited by the relationship_aliased_class feature.

    References: #12437

  • [orm] [bug]

    A significant behavioral change has been made to the behavior of the mapped_column.default and relationship.default parameters, when used with SQLAlchemy’s Declarative Dataclass Mapping feature introduced in 2.0, where the given value (assumed to be an immutable scalar value) is no longer passed to the @dataclass API as a real default, instead a token that leaves the value un-set in the object’s __dict__ is used, in conjunction with a descriptor-level default. This prevents an un-set default value from overriding a default that was actually set elsewhere, such as in relationship / foreign key assignment patterns as well as in Session.merge() scenarios. See the full writeup in the What’s New in SQLAlchemy 2.1? document which includes guidance on how to re-enable the 2.0 version of the behavior if needed.

    See also

    ORM Mapped Dataclasses no longer populate implicit default in __dict__

    References: #12168

  • [orm] [bug]

    The relationship.secondary parameter no longer uses Python eval() to evaluate the given string. This parameter when passed a string should resolve to a table name that’s present in the local MetaData collection only, and never needs to be any kind of Python expression otherwise. To use a real deferred callable based on a name that may not be locally present yet, use a lambda instead.

    References: #10564

  • [orm] [bug]

    Revised the set “binary” operators for the association proxy set() interface to correctly raise TypeError for invalid use of the |, &, ^, and - operators, as well as the in-place mutation versions of these methods, to match the behavior of standard Python set() as well as SQLAlchemy ORM’s “intstrumented” set implementation.

    References: #11349

  • [orm] [bug]

    The behavior of with_polymorphic() when used with a single inheritance mapping has been changed such that its behavior should match as closely as possible to that of an equivalent joined inheritance mapping. Specifically this means that the base class specified in the with_polymorphic() construct will be the basemost class that is loaded, as well as all descendant classes of that basemost class. The change includes that the descendant classes named will no longer be exclusively indicated in “WHERE polymorphic_col IN” criteria; instead, the whole hierarchy starting with the given basemost class will be loaded. If the query indicates that rows should only be instances of a specific subclass within the polymorphic hierarchy, an error is raised if an incompatible superclass is loaded in the result since it cannot be made to match the requested class; this behavior is the same as what joined inheritance has done for many years. The change also allows a single result set to include column-level results from multiple sibling classes at once which was not previously possible with single table inheritance.

    References: #12395

  • [orm]

    The noload() relationship loader option and related lazy='noload' setting is deprecated and will be removed in a future release. This option was originally intended for custom loader patterns that are no longer applicable in modern SQLAlchemy.

    References: #11045

  • [orm]

    Ignore Session.join_transaction_mode in all cases when the bind provided to the Session is an Engine. Previously if an event that executed before the session logic, like ConnectionEvents.engine_connect(), left the connection with an active transaction, the Session.join_transaction_mode behavior took place, leading to a surprising behavior.

    References: #11163

engine

  • [engine] [usecase]

    Added new execution option Connection.execution_options.driver_column_names. This option disables the “name normalize” step that takes place against the DBAPI cursor.description for uppercase-default backends like Oracle, and will cause the keys of a result set (e.g. named tuple names, dictionary keys in Row._mapping, etc.) to be exactly what was delivered in cursor.description. This is mostly useful for plain textual statements using text() or Connection.exec_driver_sql().

    References: #10789

  • [engine] [change]

    An empty sequence passed to any execute() method now raised a deprecation warning, since such an executemany is invalid. Pull request courtesy of Carlos Sousa.

    References: #9647

  • [engine] [bug]

    Adjusted URL parsing and stringification to apply url quoting to the “database” portion of the URL. This allows a URL where the “database” portion includes special characters such as question marks to be accommodated.

    See also

    URL stringify and parse now supports URL escaping for the “database” portion

    References: #11234

sql

  • [sql] [feature]

    Added the ability to create custom SQL constructs that can define new clauses within SELECT, INSERT, UPDATE, and DELETE statements without needing to modify the construction or compilation code of of Select, Insert, Update, or Delete directly. Support for testing these constructs, including caching support, is present along with an example test suite. The use case for these constructs is expected to be third party dialects for analytical SQL (so-called NewSQL) or other novel styles of database that introduce new clauses to these statements. A new example suite is included which illustrates the QUALIFY SQL construct used by several NewSQL databases which includes a cachable implementation as well as a test suite.

    See also

    Extending Statements like SELECT, INSERT, etc

    References: #12195

  • [sql] [usecase]

    Added support for the pow operator (**), with a default SQL implementation of the POW() function. On Oracle Database, PostgreSQL and MSSQL it renders as POWER(). As part of this change, the operator routes through a new first class func member pow, which renders on Oracle Database, PostgreSQL and MSSQL as POWER().

    References: #8579

  • [sql] [change]

    the Numeric and Float SQL types have been separated out so that Float no longer inherits from Numeric; instead, they both extend from a common mixin NumericCommon. This corrects for some architectural shortcomings where numeric and float types are typically separate, and establishes more consistency with Integer also being a distinct type. The change should not have any end-user implications except for code that may be using isinstance() to test for the Numeric datatype; third party dialects which rely upon specific implementation types for numeric and/or float may also require adjustment to maintain compatibility.

    References: #5252

  • [sql] [change]

    The .c and .columns attributes on the Select and TextualSelect constructs, which are not instances of FromClause, have been removed completely, in addition to the .select() method as well as other codepaths which would implicitly generate a subquery from a Select without the need to explicitly call the Select.subquery() method.

    In the case of .c and .columns, these attributes were never useful in practice and have caused a great deal of confusion, hence were deprecated back in version 1.4, and have emitted warnings since that version. Accessing the columns that are specific to a Select construct is done via the Select.selected_columns attribute, which was added in version 1.4 to suit the use case that users often expected .c to accomplish. In the larger sense, implicit production of subqueries works against SQLAlchemy’s modern practice of making SQL structure as explicit as possible.

    Note that this is not related to the usual FromClause.c and FromClause.columns attributes, common to objects such as Table and Subquery, which are unaffected by this change.

    See also

    A SELECT statement is no longer implicitly considered to be a FROM clause - original notes from SQLAlchemy 1.4

    References: #10236

  • [sql] [bug]

    Fixed issue in name normalization (e.g. “uppercase” backends like Oracle) where using a TextualSelect would not properly maintain as uppercase column names that were quoted as uppercase, even though the TextualSelect includes a Column that explicitly holds this uppercase name.

    References: #10788

  • [sql] [bug]

    Enhanced the caching structure of the over.rows and over.range so that different numerical values for the rows / range fields are cached on the same cache key, to the extent that the underlying SQL does not actually change (i.e. “unbounded”, “current row”, negative/positive status will still change the cache key). This prevents the use of many different numerical range/rows value for a query that is otherwise identical from filling up the SQL cache.

    Note that the semi-private compiler method _format_frame_clause() is removed by this fix, replaced with a new method visit_frame_clause(). Third party dialects which may have referred to this method will need to change the name and revise the approach to rendering the correct SQL for that dialect.

    References: #11515

  • [sql]

    Removed the automatic coercion of executable objects, such as Query, when passed into Session.execute(). This usage raised a deprecation warning since the 1.4 series.

    References: #12218

schema

  • [schema] [bug]

    The Float and Numeric types are no longer automatically considered as auto-incrementing columns when the Column.autoincrement parameter is left at its default of "auto" on a Column that is part of the primary key. When the parameter is set to True, a Numeric type will be accepted as an auto-incrementing datatype for primary key columns, but only if its scale is explicitly given as zero; otherwise, an error is raised. This is a change from 2.0 where all numeric types including floats were automatically considered as “autoincrement” for primary key columns.

    References: #11811

  • [schema]

    Deprecate Oracle only parameters Sequence.order, Identity.order and Identity.on_null. They should be configured using the dialect kwargs oracle_order and oracle_on_null.

    References: #10247

typing

  • [typing] [feature]

    The Row object now no longer makes use of an intermediary Tuple in order to represent its individual element types; instead, the individual element types are present directly, via new PEP 646 integration, now available in more recent versions of Mypy. Mypy 1.7 or greater is now required for statements, results and rows to be correctly typed. Pull request courtesy Yurii Karabas.

    See also

    Row now represents individual column types directly without Tuple

    References: #10635

  • [typing]

    The default implementation of TypeEngine.python_type now returns object instead of NotImplementedError, since that’s the base for all types in Python3. The python_type of JSON no longer returns dict, but instead fallbacks to the generic implementation.

    References: #10646

  • [typing] [orm]

    Removed the deprecated mypy plugin. The plugin was non-functional with newer version of mypy and it’s no longer needed with modern SQLAlchemy declarative style.

    References: #12293

asyncio

  • [asyncio] [change]

    Adapted all asyncio dialects, including aiosqlite, aiomysql, asyncmy, psycopg, asyncpg to use the generic asyncio connection adapter first added in #6521 for the aioodbc DBAPI, allowing these dialects to take advantage of a common framework.

    References: #10415

  • [asyncio] [change]

    Added an initialize step to the import of sqlalchemy.ext.asyncio so that greenlet will be imported only when the asyncio extension is first imported. Alternatively, the greenlet library is still imported lazily on first use to support use case that don’t make direct use of the SQLAlchemy asyncio extension.

    References: #10296

  • [asyncio] [change]

    Removed the compatibility async_fallback mode for async dialects, since it’s no longer used by SQLAlchemy tests. Also removed the internal function await_fallback() and renamed the internal function await_only() to await_(). No change is expected to user code.

postgresql

mysql

  • [mysql] [feature]

    Added new construct limit() which can be applied to any update() or delete() to provide the LIMIT keyword to UPDATE and DELETE. This new construct supersedes the use of the “mysql_limit” dialect keyword argument.

mariadb

  • [mariadb] [usecase]

    Modified the MariaDB dialect so that when using the Uuid datatype with MariaDB >= 10.7, leaving the Uuid.native_uuid parameter at its default of True, the native UUID datatype will be rendered in DDL and used for database communication, rather than CHAR(32) (the non-native UUID type) as was the case previously. This is a behavioral change since 2.0, where the generic Uuid datatype delivered CHAR(32) for all MySQL and MariaDB variants. Support for all major DBAPIs is implemented including support for less common “insertmanyvalues” scenarios where UUID values are generated in different ways for primary keys. Thanks much to Volodymyr Kochetkov for delivering the PR.

    References: #10339

mssql

  • [mssql] [bug]

    Fix mssql+pyodbc issue where valid plus signs in an already-unquoted odbc_connect= (raw DBAPI) connection string are replaced with spaces.

    The pyodbc connector would unconditionally pass the odbc_connect value to unquote_plus(), even if it was not required. So, if the (unquoted) odbc_connect value contained PWD=pass+word that would get changed to PWD=pass word, and the login would fail. One workaround was to quote just the plus sign — PWD=pass%2Bword — which would then get unquoted to PWD=pass+word.

    References: #11250

misc

  • [change] [installation]

    Python 3.9 or above is now required; support for Python 3.8 and 3.7 is dropped as these versions are EOL.

    References: #10357, #12029

  • [change] [installation]

    The greenlet dependency used for asyncio support no longer installs by default. This dependency does not publish wheel files for every architecture and is not needed for applications that aren’t using asyncio features. Use the sqlalchemy[asyncio] install target to include this dependency.

    See also

    Asyncio “greenlet” dependency no longer installs by default

    References: #10197

  • [change] [setup]

    Updated the setup manifest definition to use PEP 621-compliant pyproject.toml. Also updated the extra install dependency to comply with PEP-685. Thanks for the help of Matt Oberle and KOLANICH on this change.

  • [misc] [changed]

    Removed multiple api that were deprecated in the 1.3 series and earlier. The list of removed features includes:

    • The force parameter of IdentifierPreparer.quote and IdentifierPreparer.quote_schema;

    • The threaded parameter of the cx-Oracle dialect;

    • The _json_serializer and _json_deserializer parameters of the SQLite dialect;

    • The collection.converter decorator;

    • The Mapper.mapped_table property;

    • The Session.close_all method;

    • Support for multiple arguments in defer() and undefer().

    References: #12441