.. changelog_imports::
.. include:: changelog_14.rst
:start-line: 5
.. changelog::
:version: 2.0.9
:include_notes_from: unreleased_20
.. changelog::
:version: 2.0.8
:released: March 31, 2023
.. change::
:tags: bug, orm
:tickets: 9553
Fixed issue in ORM Annotated Declarative where using a recursive type (e.g.
using a nested Dict type) would result in a recursion overflow in the ORM's
annotation resolution logic, even if this datatype were not necessary to
map the column.
.. change::
:tags: bug, examples
Fixed issue in "versioned history" example where using a declarative base
that is derived from :class:`_orm.DeclarativeBase` would fail to be mapped.
Additionally, repaired the given test suite so that the documented
instructions for running the example using Python unittest now work again.
.. change::
:tags: bug, orm
:tickets: 9550
Fixed issue where the :func:`_orm.mapped_column` construct would raise an
internal error if used on a Declarative mixin and included the
:paramref:`_orm.mapped_column.deferred` parameter.
.. change::
:tags: bug, mysql
:tickets: 9544
Fixed issue where string datatypes such as :class:`_sqltypes.CHAR`,
:class:`_sqltypes.VARCHAR`, :class:`_sqltypes.TEXT`, as well as binary
:class:`_sqltypes.BLOB`, could not be produced with an explicit length of
zero, which has special meaning for MySQL. Pull request courtesy J. Nick
Koston.
.. change::
:tags: bug, orm
:tickets: 9537
Expanded the warning emitted when a plain :func:`_sql.column` object is
present in a Declarative mapping to include any arbitrary SQL expression
that is not declared within an appropriate property type such as
:func:`_orm.column_property`, :func:`_orm.deferred`, etc. These attributes
are otherwise not mapped at all and remain unchanged within the class
dictionary. As it seems likely that such an expression is usually not
what's intended, this case now warns for all such otherwise ignored
expressions, rather than just the :func:`_sql.column` case.
.. change::
:tags: bug, orm
:tickets: 9519
Fixed regression where accessing the expression value of a hybrid property
on a class that was either unmapped or not-yet-mapped (such as calling upon
it within a :func:`_orm.declared_attr` method) would raise an internal
error, as an internal fetch for the parent class' mapper would fail and an
instruction for this failure to be ignored were inadvertently removed in
2.0.
.. change::
:tags: bug, orm
:tickets: 9350
Fields that are declared on Declarative Mixins and then combined with
classes that make use of :class:`_orm.MappedAsDataclass`, where those mixin
fields are not themselves part of a dataclass, now emit a deprecation
warning as these fields will be ignored in a future release, as Python
dataclasses behavior is to ignore these fields. Type checkers will not see
these fields under pep-681.
.. seealso::
:ref:`error_dcmx` - background on rationale
:ref:`orm_declarative_dc_mixins`
.. change::
:tags: bug, postgresql
:tickets: 9511
Fixed critical regression in PostgreSQL dialects such as asyncpg which rely
upon explicit casts in SQL in order for datatypes to be passed to the
driver correctly, where a :class:`.String` datatype would be cast along
with the exact column length being compared, leading to implicit truncation
when comparing a ``VARCHAR`` of a smaller length to a string of greater
length regardless of operator in use (e.g. LIKE, MATCH, etc.). The
PostgreSQL dialect now omits the length from ``VARCHAR`` when rendering
these casts.
.. change::
:tags: bug, util
:tickets: 9487
Implemented missing methods ``copy`` and ``pop`` in
OrderedSet class.
.. change::
:tags: bug, typing
:tickets: 9536
Fixed typing for :func:`_orm.deferred` and :func:`_orm.query_expression`
to work correctly with 2.0 style mappings.
.. change::
:tags: bug, orm
:tickets: 9526
Fixed issue where the :meth:`_sql.BindParameter.render_literal_execute`
method would fail when called on a parameter that also had ORM annotations
associated with it. In practice, this would be observed as a failure of SQL
compilation when using some combinations of a dialect that uses "FETCH
FIRST" such as Oracle along with a :class:`_sql.Select` construct that uses
:meth:`_sql.Select.limit`, within some ORM contexts, including if the
statement were embedded within a relationship primaryjoin expression.
.. change::
:tags: usecase, orm
:tickets: 9563
Exceptions such as ``TypeError`` and ``ValueError`` raised by Python
dataclasses when making use of the :class:`_orm.MappedAsDataclass` mixin
class or :meth:`_orm.registry.mapped_as_dataclass` decorator are now
wrapped within an :class:`.InvalidRequestError` wrapper along with
informative context about the error message, referring to the Python
dataclasses documentation as the authoritative source of background
information on the cause of the exception.
.. seealso::
:ref:`error_dcte`
.. change::
:tags: bug, orm
:tickets: 9549
Towards maintaining consistency with unit-of-work changes made for
:ticket:`5984` and :ticket:`8862`, both of which disable "lazy='raise'"
handling within :class:`_orm.Session` processes that aren't triggered by
attribute access, the :meth:`_orm.Session.delete` method will now also
disable "lazy='raise'" handling when it traverses relationship paths in
order to process the "delete" and "delete-orphan" cascade rules.
Previously, there was no easy way to generically call
:meth:`_orm.Session.delete` on an object that had "lazy='raise'" set up
such that only the necessary relationships would be loaded. As
"lazy='raise'" is primarily intended to catch SQL loading that emits on
attribute access, :meth:`_orm.Session.delete` is now made to behave like
other :class:`_orm.Session` methods including :meth:`_orm.Session.merge` as
well as :meth:`_orm.Session.flush` along with autoflush.
.. change::
:tags: bug, orm
:tickets: 9564
Fixed issue where an annotation-only :class:`_orm.Mapped` directive could
not be used in a Declarative mixin class, without that attribute attempting
to take effect for single- or joined-inheritance subclasses of mapped
classes that had already mapped that attribute on a superclass, producing
conflicting column errors and/or warnings.
.. change::
:tags: bug, orm, typing
:tickets: 9514
Properly type :paramref:`_dml.Insert.from_select.names` to accept
a list of string or columns or mapped attributes.
.. changelog::
:version: 2.0.7
:released: March 18, 2023
.. change::
:tags: usecase, postgresql
:tickets: 9416
Added new PostgreSQL type :class:`_postgresql.CITEXT`. Pull request
courtesy Julian David Rath.
.. change::
:tags: bug, typing
:tickets: 9502
Fixed typing issue where :func:`_orm.composite` would not allow an
arbitrary callable as the source of the composite class.
.. change::
:tags: usecase, postgresql
:tickets: 9442
Modifications to the base PostgreSQL dialect to allow for better integration with the
sqlalchemy-redshift third party dialect for SQLAlchemy 2.0. Pull request courtesy
matthewgdv.
.. changelog::
:version: 2.0.6
:released: March 13, 2023
.. change::
:tags: bug, sql, regression
:tickets: 9461
Fixed regression where the fix for :ticket:`8098`, which was released in
the 1.4 series and provided a layer of concurrency-safe checks for the
lambda SQL API, included additional fixes in the patch that failed to be
applied to the main branch. These additional fixes have been applied.
.. change::
:tags: bug, typing
:tickets: 9451
Fixed typing issue where :meth:`.ColumnElement.cast` did not allow a
:class:`.TypeEngine` argument independent of the type of the
:class:`.ColumnElement` itself, which is the purpose of
:meth:`.ColumnElement.cast`.
.. change::
:tags: bug, orm
:tickets: 9460
Fixed bug where the "active history" feature was not fully
implemented for composite attributes, making it impossible to receive
events that included the "old" value. This seems to have been the case
with older SQLAlchemy versions as well, where "active_history" would
be propagated to the underlying column-based attributes, but an event
handler listening to the composite attribute itself would not be given
the "old" value being replaced, even if the composite() were set up
with active_history=True.
Additionally, fixed a regression that's local to 2.0 which disallowed
active_history on composite from being assigned to the impl with
``attr.impl.active_history=True``.
.. change::
:tags: bug, oracle
:tickets: 9459
Fixed reflection bug where Oracle "name normalize" would not work correctly
for reflection of symbols that are in the "PUBLIC" schema, such as
synonyms, meaning the PUBLIC name could not be indicated as lower case on
the Python side for the :paramref:`_schema.Table.schema` argument. Using
uppercase "PUBLIC" would work, but would then lead to awkward SQL queries
including a quoted ``"PUBLIC"`` name as well as indexing the table under
uppercase "PUBLIC", which was inconsistent.
.. change::
:tags: bug, typing
Fixed issues to allow typing tests to pass under Mypy 1.1.1.
.. change::
:tags: bug, sql
:tickets: 9440
Fixed regression where the :func:`_sql.select` construct would not be able
to render if it were given no columns and then used in the context of an
EXISTS, raising an internal exception instead. While an empty "SELECT" is
not typically valid SQL, in the context of EXISTS databases such as
PostgreSQL allow it, and in any case the condition now no longer raises
an internal exception.
.. change::
:tags: bug, orm
:tickets: 9418
Fixed regression involving pickling of Python rows between the cython and
pure Python implementations of :class:`.Row`, which occurred as part of
refactoring code for version 2.0 with typing. A particular constant were
turned into a string based ``Enum`` for the pure Python version of
:class:`.Row` whereas the cython version continued to use an integer
constant, leading to deserialization failures.
.. changelog::
:version: 2.0.5.post1
:released: March 5, 2023
.. change::
:tags: bug, orm
:tickets: 9418
Added constructor arguments to the built-in mapping collection types
including :class:`.KeyFuncDict`, :func:`_orm.attribute_keyed_dict`,
:func:`_orm.column_keyed_dict` so that these dictionary types may be
constructed in place given the data up front; this provides further
compatibility with tools such as Python dataclasses ``.asdict()`` which
relies upon invoking these classes directly as ordinary dictionary classes.
.. change::
:tags: bug, orm, regression
:tickets: 9424
Fixed multiple regressions due to :ticket:`8372`, involving
:func:`_orm.attribute_mapped_collection` (now called
:func:`_orm.attribute_keyed_dict`).
First, the collection was no longer usable with "key" attributes that were
not themselves ordinary mapped attributes; attributes linked to descriptors
and/or association proxy attributes have been fixed.
Second, if an event or other operation needed access to the "key" in order
to populate the dictionary from an mapped attribute that was not
loaded, this also would raise an error inappropriately, rather than
trying to load the attribute as was the behavior in 1.4. This is also
fixed.
For both cases, the behavior of :ticket:`8372` has been expanded.
:ticket:`8372` introduced an error that raises when the derived key that
would be used as a mapped dictionary key is effectively unassigned. In this
change, a warning only is emitted if the effective value of the ".key"
attribute is ``None``, where it cannot be unambiguously determined if this
``None`` was intentional or not. ``None`` will be not supported as mapped
collection dictionary keys going forward (as it typically refers to NULL
which means "unknown"). Setting
:paramref:`_orm.attribute_keyed_dict.ignore_unpopulated_attribute` will now
cause such ``None`` keys to be ignored as well.
.. change::
:tags: engine, performance
:tickets: 9343
A small optimization to the Cython implementation of :class:`.Result`
using a cdef for a particular int value to avoid Python overhead. Pull
request courtesy Matus Valo.
.. change::
:tags: bug, mssql
:tickets: 9414
Fixed issue in the new :class:`.Uuid` datatype which prevented it from
working with the pymssql driver. As pymssql seems to be maintained again,
restored testing support for pymssql.
.. change::
:tags: bug, mssql
Tweaked the pymssql dialect to take better advantage of
RETURNING for INSERT statements in order to retrieve last inserted primary
key values, in the same way as occurs for the mssql+pyodbc dialect right
now.
.. change::
:tags: bug, orm
Identified that the ``sqlite`` and ``mssql+pyodbc`` dialects are now
compatible with the SQLAlchemy ORM's "versioned rows" feature, since
SQLAlchemy now computes rowcount for a RETURNING statement in this specific
case by counting the rows returned, rather than relying upon
``cursor.rowcount``. In particular, the ORM versioned rows use case
(documented at :ref:`mapper_version_counter`) should now be fully
supported with the SQL Server pyodbc dialect.
.. change::
:tags: bug, postgresql
:tickets: 9349
Fixed issue in PostgreSQL :class:`_postgresql.ExcludeConstraint` where
literal values were being compiled as bound parameters and not direct
inline values as is required for DDL.
.. change::
:tags: bug, typing
Fixed bug where the :meth:`_engine.Connection.scalars` method was not typed
as allowing a multiple-parameters list, which is now supported using
insertmanyvalues operations.
.. change::
:tags: bug, typing
:tickets: 9376
Improved typing for the mapping passed to :meth:`.Insert.values` and
:meth:`.Update.values` to be more open-ended about collection type, by
indicating read-only ``Mapping`` instead of writeable ``Dict`` which would
error out on too limited of a key type.
.. change::
:tags: schema
Validate that when provided the :paramref:`_schema.MetaData.schema`
argument of :class:`_schema.MetaData` is a string.
.. change::
:tags: typing, usecase
:tickets: 9338
Exported the type returned by
:meth:`_orm.scoped_session.query_property` using a new public type
:class:`.orm.QueryPropertyDescriptor`.
.. change::
:tags: bug, mysql, postgresql
:tickets: 5648
The support for pool ping listeners to receive exception events via the
:meth:`.DialectEvents.handle_error` event added in 2.0.0b1 for
:ticket:`5648` failed to take into account dialect-specific ping routines
such as that of MySQL and PostgreSQL. The dialect feature has been reworked
so that all dialects participate within event handling. Additionally,
a new boolean element :attr:`.ExceptionContext.is_pre_ping` is added
which identifies if this operation is occurring within the pre-ping
operation.
For this release, third party dialects which implement a custom
:meth:`_engine.Dialect.do_ping` method can opt in to the newly improved
behavior by having their method no longer catch exceptions or check
exceptions for "is_disconnect", instead just propagating all exceptions
outwards. Checking the exception for "is_disconnect" is now done by an
enclosing method on the default dialect, which ensures that the event hook
is invoked for all exception scenarios before testing the exception as a
"disconnect" exception. If an existing ``do_ping()`` method continues to
catch exceptions and check "is_disconnect", it will continue to work as it
did previously, but ``handle_error`` hooks will not have access to the
exception if it isn't propagated outwards.
.. change::
:tags: bug, ext
:tickets: 9367
Fixed issue in automap where calling :meth:`_automap.AutomapBase.prepare`
from a specific mapped class, rather than from the
:class:`_automap.AutomapBase` directly, would not use the correct base
class when automap detected new tables, instead using the given class,
leading to mappers trying to configure inheritance. While one should
normally call :meth:`_automap.AutomapBase.prepare` from the base in any
case, it shouldn't misbehave that badly when called from a subclass.
.. change::
:tags: bug, sqlite, regression
:tickets: 9379
Fixed regression for SQLite connections where use of the ``deterministic``
parameter when establishing database functions would fail for older SQLite
versions, those prior to version 3.8.3. The version checking logic has been
improved to accommodate for this case.
.. change::
:tags: bug, typing
:tickets: 9391
Added missing init overload to the :class:`_types.Numeric` type object so
that pep-484 type checkers may properly resolve the complete type, deriving
from the :paramref:`_types.Numeric.asdecimal` parameter whether ``Decimal``
or ``float`` objects will be represented.
.. change::
:tags: bug, typing
:tickets: 9398
Fixed typing bug where :meth:`_sql.Select.from_statement` would not accept
:func:`_sql.text` or :class:`.TextualSelect` objects as a valid type.
Additionally repaired the :class:`.TextClause.columns` method to have a
return type, which was missing.
.. change::
:tags: bug, orm declarative
:tickets: 9332
Fixed issue where new :paramref:`_orm.mapped_column.use_existing_column`
feature would not work if the two same-named columns were mapped under
attribute names that were differently-named from an explicit name given to
the column itself. The attribute names can now be differently named when
using this parameter.
.. change::
:tags: bug, orm
:tickets: 9373
Added support for the :paramref:`_orm.Mapper.polymorphic_load` parameter to
be applied to each mapper in an inheritance hierarchy more than one level
deep, allowing columns to load for all classes in the hierarchy that
indicate ``"selectin"`` using a single statement, rather than ignoring
elements on those intermediary classes that nonetheless indicate they also
would participate in ``"selectin"`` loading and were not part of the
base-most SELECT statement.
.. change::
:tags: bug, orm
:tickets: 8853, 9335
Continued the fix for :ticket:`8853`, allowing the :class:`_orm.Mapped`
name to be fully qualified regardless of whether or not
``from __annotations__ import future`` were present. This issue first fixed
in 2.0.0b3 confirmed that this case worked via the test suite, however the
test suite apparently was not testing the behavior for the name
:class:`_orm.Mapped` not being locally present at all; string resolution
has been updated to ensure the :class:`_orm.Mapped` symbol is locatable as
applies to how the ORM uses these functions.
.. change::
:tags: bug, typing
:tickets: 9340
Fixed typing issue where :func:`_orm.with_polymorphic` would not
record the class type correctly.
.. change::
:tags: bug, ext, regression
:tickets: 9380
Fixed regression caused by typing added to ``sqlalchemy.ext.mutable`` for
:ticket:`8667`, where the semantics of the ``.pop()`` method changed such
that the method was non-working. Pull request courtesy Nils Philippsen.
.. change::
:tags: bug, sql, regression
:tickets: 9390
Restore the :func:`.nullslast` and :func:`.nullsfirst` legacy functions
into the ``sqlalchemy`` import namespace. Previously, the newer
:func:`.nulls_last` and :func:`.nulls_first` functions were available, but
the legacy ones were inadvertently removed.
.. change::
:tags: bug, postgresql
:tickets: 9401
Fixed issue where the PostgreSQL :class:`_postgresql.ExcludeConstraint`
construct would not be copyable within operations such as
:meth:`_schema.Table.to_metadata` as well as within some Alembic scenarios,
if the constraint contained textual expression elements.
.. change::
:tags: bug, engine
:tickets: 9423
Fixed bug where :class:`_engine.Row` objects could not be reliably unpickled
across processes due to an accidental reliance on an unstable hash value.
.. changelog::
:version: 2.0.4
:released: February 17, 2023
.. change::
:tags: bug, orm, regression
:tickets: 9273
Fixed regression introduced in version 2.0.2 due to :ticket:`9217` where
using DML RETURNING statements, as well as
:meth:`_sql.Select.from_statement` constructs as was "fixed" in
:ticket:`9217`, in conjunction with ORM mapped classes that used
expressions such as with :func:`_orm.column_property`, would lead to an
internal error within Core where it would attempt to match the expression
by name. The fix repairs the Core issue, and also adjusts the fix in
:ticket:`9217` to not take effect for the DML RETURNING use case, where it
adds unnecessary overhead.
.. change::
:tags: usecase, typing
:tickets: 9321
Improved the typing support for the :ref:`hybrids_toplevel`
extension, updated all documentation to use ORM Annotated Declarative
mappings, and added a new modifier called :attr:`.hybrid_property.inplace`.
This modifier provides a way to alter the state of a :class:`.hybrid_property`
**in place**, which is essentially what very early versions of hybrids
did, before SQLAlchemy version 1.2.0 :ticket:`3912` changed this to
remove in-place mutation. This in-place mutation is now restored on an
**opt-in** basis to allow a single hybrid to have multiple methods
set up, without the need to name all the methods the same and without the
need to carefully "chain" differently-named methods in order to maintain
the composition. Typing tools such as Mypy and Pyright do not allow
same-named methods on a class, so with this change a succinct method
of setting up hybrids with typing support is restored.
.. seealso::
:ref:`hybrid_pep484_naming`
.. change::
:tags: bug, orm
Marked the internal ``EvaluatorCompiler`` module as private to the ORM, and
renamed it to ``_EvaluatorCompiler``. For users that may have been relying
upon this, the name ``EvaluatorCompiler`` is still present, however this
use is not supported and will be removed in a future release.
.. change::
:tags: orm, use_case
:tickets: 9297
To accommodate a change in column ordering used by ORM Declarative in
SQLAlchemy 2.0, a new parameter :paramref:`_orm.mapped_column.sort_order`
has been added that can be used to control the order of the columns defined
in the table by the ORM, for common use cases such as mixins with primary
key columns that should appear first in tables. The change notes at
:ref:`change_9297` illustrate the default change in ordering behavior
(which is part of all SQLAlchemy 2.0 releases) as well as use of the
:paramref:`_orm.mapped_column.sort_order` to control column ordering when
using mixins and multiple classes (new in 2.0.4).
.. seealso::
:ref:`change_9297`
.. change::
:tags: sql
:tickets: 9277
Added public property :attr:`_schema.Table.autoincrement_column` that
returns the column identified as autoincrementing in the column.
.. change::
:tags: oracle, bug
:tickets: 9295
Adjusted the behavior of the ``thick_mode`` parameter for the
:ref:`oracledb` dialect to correctly accept ``False`` as a value.
Previously, only ``None`` would indicate that thick mode should be
disabled.
.. change::
:tags: usecase, orm
:tickets: 9298
The :meth:`_orm.Session.refresh` method will now immediately load a
relationship-bound attribute that is explicitly named within the
:paramref:`_orm.Session.refresh.attribute_names` collection even if it is
currently linked to the "select" loader, which normally is a "lazy" loader
that does not fire off during a refresh. The "lazy loader" strategy will
now detect that the operation is specifically a user-initiated
:meth:`_orm.Session.refresh` operation which named this attribute
explicitly, and will then call upon the "immediateload" strategy to
actually emit SQL to load the attribute. This should be helpful in
particular for some asyncio situations where the loading of an unloaded
lazy-loaded attribute must be forced, without using the actual lazy-loading
attribute pattern not supported in asyncio.
.. change::
:tags: bug, sql
:tickets: 9313
Fixed issue where element types of a tuple value would be hardcoded to take
on the types from a compared-to tuple, when the comparison were using the
:meth:`.ColumnOperators.in_` operator. This was inconsistent with the usual
way that types are determined for a binary expression, which is that the
actual element type on the right side is considered first before applying
the left-hand-side type.
.. change::
:tags: usecase, orm declarative
:tickets: 9266
Added new parameter ``dataclasses_callable`` to both the
:class:`_orm.MappedAsDataclass` class as well as the
:meth:`_orm.registry.mapped_as_dataclass` method which allows an
alternative callable to Python ``dataclasses.dataclass`` to be used in
order to produce dataclasses. The use case here is to drop in Pydantic's
dataclass function instead. Adjustments have been made to the mixin support
added for :ticket:`9179` in version 2.0.1 so that the ``__annotations__``
collection of the mixin is rewritten to not include the
:class:`_orm.Mapped` container, in the same way as occurs with mapped
classes, so that the Pydantic dataclasses constructor is not exposed to
unknown types.
.. seealso::
:ref:`dataclasses_pydantic`
.. changelog::
:version: 2.0.3
:released: February 9, 2023
.. change::
:tags: typing, bug
:tickets: 9254
Remove ``typing.Self`` workaround, now using :pep:`673` for most methods
that return ``Self``. As a consequence of this change ``mypy>=1.0.0`` is
now required to type check SQLAlchemy code.
Pull request courtesy Yurii Karabas.
.. change::
:tags: bug, sql, regression
:tickets: 9271
Fixed critical regression in SQL expression formulation in the 2.0 series
due to :ticket:`7744` which improved support for SQL expressions that
contained many elements against the same operator repeatedly; parenthesis
grouping would be lost with expression elements beyond the first two
elements.
.. changelog::
:version: 2.0.2
:released: February 6, 2023
.. change::
:tags: bug, orm declarative
:tickets: 9249
Fixed regression caused by the fix for :ticket:`9171`, which itself was
fixing a regression, involving the mechanics of ``__init__()`` on classes
that extend from :class:`_orm.DeclarativeBase`. The change made it such
that ``__init__()`` was applied to the user-defined base if there were no
``__init__()`` method directly on the class. This has been adjusted so that
``__init__()`` is applied only if no other class in the hierarchy of the
user-defined base has an ``__init__()`` method. This again allows
user-defined base classes based on :class:`_orm.DeclarativeBase` to include
mixins that themselves include a custom ``__init__()`` method.
.. change::
:tags: bug, mysql, regression
:tickets: 9251
Fixed regression caused by issue :ticket:`9058` which adjusted the MySQL
dialect's ``has_table()`` to again use "DESCRIBE", where the specific error
code raised by MySQL version 8 when using a non-existent schema name was
unexpected and failed to be interpreted as a boolean result.
.. change::
:tags: bug, sqlite
:tickets: 9251
Fixed the SQLite dialect's ``has_table()`` function to correctly report
False for queries that include a non-None schema name for a schema that
doesn't exist; previously, a database error was raised.
.. change::
:tags: bug, orm declarative
:tickets: 9226
Fixed issue in ORM Declarative Dataclass mappings related to newly added
support for mixins added in 2.0.1 via :ticket:`9179`, where a combination
of using mixins plus ORM inheritance would mis-classify fields in some
cases leading to field-level dataclass arguments such as ``init=False`` being
lost.
.. change::
:tags: bug, orm, ression
:tickets: 9232
Fixed obscure ORM inheritance issue caused by :ticket:`8705` where some
scenarios of inheriting mappers that indicated groups of columns from the
local table and the inheriting table together under a
:func:`_orm.column_property` would nonetheless warn that properties of the
same name were being combined implicitly.
.. change::
:tags: orm, bug, regression
:tickets: 9228
Fixed regression where using the :paramref:`_orm.Mapper.version_id_col`
feature with a regular Python-side incrementing column would fail to work
for SQLite and other databases that don't support "rowcount" with
"RETURNING", as "RETURNING" would be assumed for such columns even though
that's not what actually takes place.
.. change::
:tags: bug, orm declarative
:tickets: 9240
Repaired ORM Declarative mappings to allow for the
:paramref:`_orm.Mapper.primary_key` parameter to be specified within
``__mapper_args__`` when using :func:`_orm.mapped_column`. Despite this
usage being directly in the 2.0 documentation, the :class:`_orm.Mapper` was
not accepting the :func:`_orm.mapped_column` construct in this context. Ths
feature was already working for the :paramref:`_orm.Mapper.version_id_col`
and :paramref:`_orm.Mapper.polymorphic_on` parameters.
As part of this change, the ``__mapper_args__`` attribute may be specified
without using :func:`_orm.declared_attr` on a non-mapped mixin class,
including a ``"primary_key"`` entry that refers to :class:`_schema.Column`
or :func:`_orm.mapped_column` objects locally present on the mixin;
Declarative will also translate these columns into the correct ones for a
particular mapped class. This again was working already for the
:paramref:`_orm.Mapper.version_id_col` and
:paramref:`_orm.Mapper.polymorphic_on` parameters. Additionally,
elements within ``"primary_key"`` may be indicated as string names of
existing mapped properties.
.. change::
:tags: usecase, sql
:tickets: 8780
Added a full suite of new SQL bitwise operators, for performing
database-side bitwise expressions on appropriate data values such as
integers, bit-strings, and similar. Pull request courtesy Yegor Statkevich.
.. seealso::
:ref:`operators_bitwise`
.. change::
:tags: bug, orm declarative
:tickets: 9211
An explicit error is raised if a mapping attempts to mix the use of
:class:`_orm.MappedAsDataclass` with
:meth:`_orm.registry.mapped_as_dataclass` within the same class hierarchy,
as this produces issues with the dataclass function being applied at the
wrong time to the mapped class, leading to errors during the mapping
process.
.. change::
:tags: bug, orm, regression
:tickets: 9217
Fixed regression when using :meth:`_sql.Select.from_statement` in an ORM
context, where matching of columns to SQL labels based on name alone was
disabled for ORM-statements that weren't fully textual. This would prevent
arbitrary SQL expressions with column-name labels from matching up to the
entity to be loaded, which previously would work within the 1.4
and previous series, so the previous behavior has been restored.
.. change::
:tags: bug, asyncio
:tickets: 9237
Repaired a regression caused by the fix for :ticket:`8419` which caused
asyncpg connections to be reset (i.e. transaction ``rollback()`` called)
and returned to the pool normally in the case that the connection were not
explicitly returned to the connection pool and was instead being
intercepted by Python garbage collection, which would fail if the garbage
collection operation were being called outside of the asyncio event loop,
leading to a large amount of stack trace activity dumped into logging
and standard output.
The correct behavior is restored, which is that all asyncio connections
that are garbage collected due to not being explicitly returned to the
connection pool are detached from the pool and discarded, along with a
warning, rather than being returned the pool, as they cannot be reliably
reset. In the case of asyncpg connections, the asyncpg-specific
``terminate()`` method will be used to end the connection more gracefully
within this process as opposed to just dropping it.
This change includes a small behavioral change that is hoped to be useful
for debugging asyncio applications, where the warning that's emitted in the
case of asyncio connections being unexpectedly garbage collected has been
made slightly more aggressive by moving it outside of a ``try/except``
block and into a ``finally:`` block, where it will emit unconditionally
regardless of whether the detach/termination operation succeeded or not. It
will also have the effect that applications or test suites which promote
Python warnings to exceptions will see this as a full exception raise,
whereas previously it was not possible for this warning to actually
propagate as an exception. Applications and test suites which need to
tolerate this warning in the interim should adjust the Python warnings
filter to allow these warnings to not raise.
The behavior for traditional sync connections remains unchanged, that
garbage collected connections continue to be returned to the pool normally
without emitting a warning. This will likely be changed in a future major
release to at least emit a similar warning as is emitted for asyncio
drivers, as it is a usage error for pooled connections to be intercepted by
garbage collection without being properly returned to the pool.
.. change::
:tags: usecase, orm
:tickets: 9220
Added new event hook :meth:`_orm.MapperEvents.after_mapper_constructed`,
which supplies an event hook to take place right as the
:class:`_orm.Mapper` object has been fully constructed, but before the
:meth:`_orm.registry.configure` call has been called. This allows code that
can create additional mappings and table structures based on the initial
configuration of a :class:`_orm.Mapper`, which also integrates within
Declarative configuration. Previously, when using Declarative, where the
:class:`_orm.Mapper` object is created within the class creation process,
there was no documented means of running code at this point. The change
is to immediately benefit custom mapping schemes such as that
of the :ref:`examples_versioned_history` example, which generate additional
mappers and tables in response to the creation of mapped classes.
.. change::
:tags: usecase, orm
:tickets: 9220
The infrequently used :attr:`_orm.Mapper.iterate_properties` attribute and
:meth:`_orm.Mapper.get_property` method, which are primarily used
internally, no longer implicitly invoke the :meth:`_orm.registry.configure`
process. Public access to these methods is extremely rare and the only
benefit to having :meth:`_orm.registry.configure` would have been allowing
"backref" properties be present in these collections. In order to support
the new :meth:`_orm.MapperEvents.after_mapper_constructed` event, iteration
and access to the internal :class:`_orm.MapperProperty` objects is now
possible without triggering an implicit configure of the mapper itself.
The more-public facing route to iteration of all mapper attributes, the
:attr:`_orm.Mapper.attrs` collection and similar, will still implicitly
invoke the :meth:`_orm.registry.configure` step thus making backref
attributes available.
In all cases, the :meth:`_orm.registry.configure` is always available to
be called directly.
.. change::
:tags: bug, examples
:tickets: 9220
Reworked the :ref:`examples_versioned_history` to work with
version 2.0, while at the same time improving the overall working of
this example to use newer APIs, including a newly added hook
:meth:`_orm.MapperEvents.after_mapper_constructed`.
.. change::
:tags: bug, mysql
:tickets: 8626
Added support for MySQL 8's new ``AS <name> ON DUPLICATE KEY`` syntax when
using :meth:`_mysql.Insert.on_duplicate_key_update`, which is required for
newer versions of MySQL 8 as the previous syntax using ``VALUES()`` now
emits a deprecation warning with those versions. Server version detection
is employed to determine if traditional MariaDB / MySQL < 8 ``VALUES()``
syntax should be used, vs. the newer MySQL 8 required syntax. Pull request
courtesy Caspar Wylie.
.. changelog::
:version: 2.0.1
:released: February 1, 2023
.. change::
:tags: bug, typing
:tickets: 9174
Opened up typing on :paramref:`.Select.with_for_update.of` to also accept
table and mapped class arguments, as seems to be available for the MySQL
dialect.
.. change::
:tags: bug, orm, regression
:tickets: 9164
Fixed regression where ORM models that used joined table inheritance with a
composite foreign key would encounter an internal error in the mapper
internals.
.. change::
:tags: bug, sql
:tickets: 7664
Corrected the fix for :ticket:`7664`, released in version 2.0.0, to also
include :class:`.DropSchema` which was inadvertently missed in this fix,
allowing stringification without a dialect. The fixes for both constructs
is backported to the 1.4 series as of 1.4.47.
.. change::
:tags: bug, orm declarative
:tickets: 9175
Added support for :pep:`484` ``NewType`` to be used in the
:paramref:`_orm.registry.type_annotation_map` as well as within
:class:`.Mapped` constructs. These types will behave in the same way as
custom subclasses of types right now; they must appear explicitly within
the :paramref:`_orm.registry.type_annotation_map` to be mapped.
.. change::
:tags: bug, typing
:tickets: 9183
Fixed typing for limit/offset methods including :meth:`.Select.limit`,
:meth:`.Select.offset`, :meth:`_orm.Query.limit`, :meth:`_orm.Query.offset`
to allow ``None``, which is the documented API to "cancel" the current
limit/offset.
.. change::
:tags: bug, orm declarative
:tickets: 9179
When using the :class:`.MappedAsDataclass` superclass, all classes within
the hierarchy that are subclasses of this class will now be run through the
``@dataclasses.dataclass`` function whether or not they are actually
mapped, so that non-ORM fields declared on non-mapped classes within the
hierarchy will be used when mapped subclasses are turned into dataclasses.
This behavior applies both to intermediary classes mapped with
``__abstract__ = True`` as well as to the user-defined declarative base
itself, assuming :class:`.MappedAsDataclass` is present as a superclass for
these classes.
This allows non-mapped attributes such as ``InitVar`` declarations on
superclasses to be used, without the need to run the
``@dataclasses.dataclass`` decorator explicitly on each non-mapped class.
The new behavior is considered as correct as this is what the :pep:`681`
implementation expects when using a superclass to indicate dataclass
behavior.
.. change::
:tags: bug, typing
:tickets: 9170
Fixed typing issue where :func:`_orm.mapped_column` objects typed as
:class:`_orm.Mapped` wouldn't be accepted in schema constraints such as
:class:`_schema.ForeignKey`, :class:`_schema.UniqueConstraint` or
:class:`_schema.Index`.
.. change::
:tags: bug, orm declarative
:tickets: 9187
Added support for :pep:`586` ``Literal[]`` to be used in the
:paramref:`_orm.registry.type_annotation_map` as well as within
:class:`.Mapped` constructs. To use custom types such as these, they must
appear explicitly within the :paramref:`_orm.registry.type_annotation_map`
to be mapped. Pull request courtesy Frederik Aalund.
As part of this change, the support for :class:`.sqltypes.Enum` in the
:paramref:`_orm.registry.type_annotation_map` has been expanded to include
support for ``Literal[]`` types consisting of string values to be used,
in addition to ``enum.Enum`` datatypes. If a ``Literal[]`` datatype
is used within ``Mapped[]`` that is not linked in
:paramref:`_orm.registry.type_annotation_map` to a specific datatype,
a :class:`.sqltypes.Enum` will be used by default.
.. seealso::
:ref:`orm_declarative_mapped_column_enums`
.. change::
:tags: bug, orm declarative
:tickets: 9200
Fixed issue involving the use of :class:`.sqltypes.Enum` within the
:paramref:`_orm.registry.type_annotation_map` where the
:paramref:`_sqltypes.Enum.native_enum` parameter would not be correctly
copied to the mapped column datatype, if it were overridden
as stated in the documentation to set this parameter to False.
.. change::
:tags: bug, orm declarative, regression
:tickets: 9171
Fixed regression in :class:`.DeclarativeBase` class where the registry's
default constructor would not be applied to the base itself, which is
different from how the previous :func:`_orm.declarative_base` construct
works. This would prevent a mapped class with its own ``__init__()`` method
from calling ``super().__init__()`` in order to access the registry's
default constructor and automatically populate attributes, instead hitting
``object.__init__()`` which would raise a ``TypeError`` on any arguments.
.. change::
:tags: bug, sql, regression
:tickets: 9173
Fixed regression related to the implementation for the new
"insertmanyvalues" feature where an internal ``TypeError`` would occur in
arrangements where a :func:`_sql.insert` would be referred towards inside
of another :func:`_sql.insert` via a CTE; made additional repairs for this
use case for positional dialects such as asyncpg when using
"insertmanyvalues".
.. change::
:tags: bug, typing
:tickets: 9156
Fixed typing for :meth:`_expression.ColumnElement.cast` to accept
both ``Type[TypeEngine[T]]`` and ``TypeEngine[T]``; previously
only ``TypeEngine[T]`` was accepted. Pull request courtesy Yurii Karabas.
.. change::
:tags: bug, orm declarative
:tickets: 9177
Improved the ruleset used to interpret :pep:`593` ``Annotated`` types when
used with Annotated Declarative mapping, the inner type will be checked for
"Optional" in all cases which will be added to the criteria by which the
column is set as "nullable" or not; if the type within the ``Annotated``
container is optional (or unioned with ``None``), the column will be
considered nullable if there are no explicit
:paramref:`_orm.mapped_column.nullable` parameters overriding it.
.. change::
:tags: bug, orm
:tickets: 9182
Improved the error reporting when linking strategy options from a base
class to another attribute that's off a subclass, where ``of_type()``
should be used. Previously, when :meth:`.Load.options` is used, the message
would lack informative detail that ``of_type()`` should be used, which was
not the case when linking the options directly. The informative detail now
emits even if :meth:`.Load.options` is used.
.. changelog::
:version: 2.0.0
:released: January 26, 2023
.. change::
:tags: bug, sql
:tickets: 7664
Fixed stringify for a the :class:`.CreateSchema` DDL construct, which
would fail with an ``AttributeError`` when stringified without a
dialect. Update: Note this fix failed to accommodate for
:class:`.DropSchema`; a followup fix in version 2.0.1 repairs this
case. The fix for both elements is backported to 1.4.47.
.. change::
:tags: usecase, orm extensions
:tickets: 5145
Added new feature to :class:`.AutomapBase` for autoload of classes across
multiple schemas which may have overlapping names, by providing a
:paramref:`.AutomapBase.prepare.modulename_for_table` parameter which
allows customization of the ``__module__`` attribute of newly generated
classes, as well as a new collection :attr:`.AutomapBase.by_module`, which
stores a dot-separated namespace of module names linked to classes based on
the ``__module__`` attribute.
Additionally, the :meth:`.AutomapBase.prepare` method may now be invoked
any number of times, with or without reflection enabled; only newly
added tables that were not previously mapped will be processed on each
call. Previously, the :meth:`.MetaData.reflect` method would need to be
called explicitly each time.
.. seealso::
:ref:`automap_by_module` - illustrates use of both techniques at once.
.. change::
:tags: orm, bug
:tickets: 7305
Improved the notification of warnings that are emitted within the configure
mappers or flush process, which are often invoked as part of a different
operation, to add additional context to the message that indicates one of
these operations as the source of the warning within operations that may
not be obviously related.
.. change::
:tags: bug, typing
:tickets: 9129
Added typing for the built-in generic functions that are available from the
:data:`_sql.func` namespace, which accept a particular set of arguments and
return a particular type, such as for :class:`_sql.count`,
:class:`_sql.current_timestamp`, etc.
.. change::
:tags: bug, typing
:tickets: 9120
Corrected the type passed for "lambda statements" so that a plain lambda is
accepted by mypy, pyright, others without any errors about argument types.
Additionally implemented typing for more of the public API for lambda
statements and ensured :class:`.StatementLambdaElement` is part of the
:class:`.Executable` hierarchy so it's typed as accepted by
:meth:`_engine.Connection.execute`.
.. change::
:tags: typing, bug
:tickets: 9122
The :meth:`_sql.ColumnOperators.in_` and
:meth:`_sql.ColumnOperators.not_in` methods are typed to include
``Iterable[Any]`` rather than ``Sequence[Any]`` for more flexibility in
argument type.
.. change::
:tags: typing, bug
:tickets: 9123
The :func:`_sql.or_` and :func:`_sql.and_` from a typing perspective
require the first argument to be present, however these functions still
accept zero arguments which will emit a deprecation warning at runtime.
Typing is also added to support sending the fixed literal ``False`` for
:func:`_sql.or_` and ``True`` for :func:`_sql.and_` as the first argument
only, however the documentation now indicates sending the
:func:`_sql.false` and :func:`_sql.true` constructs in these cases as a
more explicit approach.
.. change::
:tags: typing, bug
:tickets: 9125
Fixed typing issue where iterating over a :class:`_orm.Query` object
was not correctly typed.
.. change::
:tags: typing, bug
:tickets: 9136
Fixed typing issue where the object type when using :class:`_engine.Result`
as a context manager were not preserved, indicating :class:`_engine.Result`
in all cases rather than the specific :class:`_engine.Result` sub-type.
Pull request courtesy Martin Baláž.
.. change::
:tags: typing, bug
:tickets: 9150
Fixed issue where using the :paramref:`_orm.relationship.remote_side`
and similar parameters, passing an annotated declarative object typed as
:class:`_orm.Mapped`, would not be accepted by the type checker.
.. change::
:tags: typing, bug
:tickets: 9148
Added typing to legacy operators such as ``isnot()``, ``notin_()``, etc.
which previously were referencing the newer operators but were not
themselves typed.
.. change::
:tags: feature, orm extensions
:tickets: 7226
Added new option to horizontal sharding API
:class:`_horizontal.set_shard_id` which sets the effective shard identifier
to query against, for both the primary query as well as for all secondary
loaders including relationship eager loaders as well as relationship and
column lazy loaders.
.. change::
:tags: bug, mssql, regression
:tickets: 9142
The newly added comment reflection and rendering capability of the MSSQL
dialect, added in :ticket:`7844`, will now be disabled by default if it
cannot be determined that an unsupported backend such as Azure Synapse may
be in use; this backend does not support table and column comments and does
not support the SQL Server routines in use to generate them as well as to
reflect them. A new parameter ``supports_comments`` is added to the dialect
which defaults to ``None``, indicating that comment support should be
auto-detected. When set to ``True`` or ``False``, the comment support is
either enabled or disabled unconditionally.
.. seealso::
:ref:`mssql_comment_support`
.. changelog::
:version: 2.0.0rc3
:released: January 26, 2023
:released: January 18, 2023
.. change::
:tags: bug, typing
:tickets: 9096
Fixes to the annotations within the ``sqlalchemy.ext.hybrid`` extension for
more effective typing of user-defined methods. The typing now uses
:pep:`612` features, now supported by recent versions of Mypy, to maintain
argument signatures for :class:`.hybrid_method`. Return values for hybrid
methods are accepted as SQL expressions in contexts such as
:meth:`_sql.Select.where` while still supporting SQL methods.
.. change::
:tags: bug, orm
:tickets: 9099
Fixed issue where using a pep-593 ``Annotated`` type in the
:paramref:`_orm.registry.type_annotation_map` which itself contained a
generic plain container or ``collections.abc`` type (e.g. ``list``,
``dict``, ``collections.abc.Sequence``, etc. ) as the target type would
produce an internal error when the ORM were trying to interpret the
``Annotated`` instance.
.. change::
:tags: bug, orm
:tickets: 9100
Added an error message when a :func:`_orm.relationship` is mapped against
an abstract container type, such as ``Mapped[Sequence[B]]``, without
providing the :paramref:`_orm.relationship.container_class` parameter which
is necessary when the type is abstract. Previously the the abstract
container would attempt to be instantiated at a later step and fail.
.. change::
:tags: orm, feature
:tickets: 9060
Added a new parameter to :class:`_orm.Mapper` called
:paramref:`_orm.Mapper.polymorphic_abstract`. The purpose of this directive
is so that the ORM will not consider the class to be instantiated or loaded
directly, only subclasses. The actual effect is that the
:class:`_orm.Mapper` will prevent direct instantiation of instances
of the class and will expect that the class does not have a distinct
polymorphic identity configured.
In practice, the class that is mapped with
:paramref:`_orm.Mapper.polymorphic_abstract` can be used as the target of a
:func:`_orm.relationship` as well as be used in queries; subclasses must of
course include polymorphic identities in their mappings.
The new parameter is automatically applied to classes that subclass
the :class:`.AbstractConcreteBase` class, as this class is not intended
to be instantiated.
.. seealso::
:ref:`orm_inheritance_abstract_poly`
.. change::
:tags: bug, postgresql
:tickets: 9106
Fixed regression where psycopg3 changed an API call as of version 3.1.8 to
expect a specific object type that was previously not enforced, breaking
connectivity for the psycopg3 dialect.
.. change::
:tags: oracle, usecase
:tickets: 9086
Added support for the Oracle SQL type ``TIMESTAMP WITH LOCAL TIME ZONE``,
using a newly added Oracle-specific :class:`_oracle.TIMESTAMP` datatype.
.. changelog::
:version: 2.0.0rc2
:released: January 26, 2023
:released: January 9, 2023
.. change::
:tags: bug, typing
:tickets: 9067
The Data Class Transforms argument ``field_descriptors`` was renamed
to ``field_specifiers`` in the accepted version of PEP 681.
.. change::
:tags: bug, oracle
:tickets: 9059
Supported use case for foreign key constraints where the local column is
marked as "invisible". The errors normally generated when a
:class:`.ForeignKeyConstraint` is created that check for the target column
are disabled when reflecting, and the constraint is skipped with a warning
in the same way which already occurs for an :class:`.Index` with a similar
issue.
.. change::
:tags: bug, orm
:tickets: 9071
Fixed issue where an overly restrictive ORM mapping rule were added in 2.0
which prevented mappings against :class:`.TableClause` objects, such as
those used in the view recipe on the wiki.
.. change::
:tags: bug, mysql
:tickets: 9058
Restored the behavior of :meth:`.Inspector.has_table` to report on
temporary tables for MySQL / MariaDB. This is currently the behavior for
all other included dialects, but was removed for MySQL in 1.4 due to no
longer using the DESCRIBE command; there was no documented support for temp
tables being reported by the :meth:`.Inspector.has_table` method in this
version or on any previous version, so the previous behavior was undefined.
As SQLAlchemy 2.0 has added formal support for temp table status via
:meth:`.Inspector.has_table`, the MySQL /MariaDB dialect has been reverted
to use the "DESCRIBE" statement as it did in the SQLAlchemy 1.3 series and
previously, and test support is added to include MySQL / MariaDB for
this behavior. The previous issues with ROLLBACK being emitted which
1.4 sought to improve upon don't apply in SQLAlchemy 2.0 due to
simplifications in how :class:`.Connection` handles transactions.
DESCRIBE is necessary as MariaDB in particular has no consistently
available public information schema of any kind in order to report on temp
tables other than DESCRIBE/SHOW COLUMNS, which rely on throwing an error
in order to report no results.
.. change::
:tags: json, postgresql
:tickets: 7147
Implemented missing ``JSONB`` operations:
* ``@@`` using :meth:`_postgresql.JSONB.Comparator.path_match`
* ``@?`` using :meth:`_postgresql.JSONB.Comparator.path_exists`
* ``#-`` using :meth:`_postgresql.JSONB.Comparator.delete_path`
Pull request curtesy of Guilherme Martins Crocetti.
.. changelog::
:version: 2.0.0rc1
:released: January 26, 2023
:released: December 28, 2022
.. change::
:tags: bug, typing
:tickets: 6810, 9025
pep-484 typing has been completed for the
``sqlalchemy.ext.horizontal_shard`` extension as well as the
``sqlalchemy.orm.events`` module. Thanks to Gleb Kisenkov for their
efforts.
.. change::
:tags: postgresql, bug
:tickets: 8977
:versions: 2.0.0rc1
Added support for explicit use of PG full text functions with asyncpg and
psycopg (SQLAlchemy 2.0 only), with regards to the ``REGCONFIG`` type cast
for the first argument, which previously would be incorrectly cast to a
VARCHAR, causing failures on these dialects that rely upon explicit type
casts. This includes support for :class:`_postgresql.to_tsvector`,
:class:`_postgresql.to_tsquery`, :class:`_postgresql.plainto_tsquery`,
:class:`_postgresql.phraseto_tsquery`,
:class:`_postgresql.websearch_to_tsquery`,
:class:`_postgresql.ts_headline`, each of which will determine based on
number of arguments passed if the first string argument should be
interpreted as a PostgreSQL "REGCONFIG" value; if so, the argument is typed
using a newly added type object :class:`_postgresql.REGCONFIG` which is
then explicitly cast in the SQL expression.
.. change::
:tags: bug, orm
:tickets: 4629
A warning is emitted if a backref name used in :func:`_orm.relationship`
names an attribute on the target class which already has a method or
attribute assigned to that name, as the backref declaration will replace
that attribute.
.. change::
:tags: bug, postgresql
:tickets: 9020
Fixed regression where newly revised PostgreSQL range types such as
:class:`_postgresql.INT4RANGE` could not be set up as the impl of a
:class:`.TypeDecorator` custom type, instead raising a ``TypeError``.
.. change::
:tags: usecase, orm
:tickets: 7837
Adjustments to the :class:`_orm.Session` in terms of extensibility,
as well as updates to the :class:`.ShardedSession` extension:
* :meth:`_orm.Session.get` now accepts
:paramref:`_orm.Session.get.bind_arguments`, which in particular may be
useful when using the horizontal sharding extension.
* :meth:`_orm.Session.get_bind` accepts arbitrary kw arguments, which
assists in developing code that uses a :class:`_orm.Session` class which
overrides this method with additional arguments.
* Added a new ORM execution option ``identity_token`` which may be used
to directly affect the "identity token" that will be associated with
newly loaded ORM objects. This token is how sharding approaches
(namely the :class:`.ShardedSession`, but can be used in other cases
as well) separate object identities across different "shards".
.. seealso::
:ref:`queryguide_identity_token`
* The :meth:`_orm.SessionEvents.do_orm_execute` event hook may now be used
to affect all ORM-related options, including ``autoflush``,
``populate_existing``, and ``yield_per``; these options are re-consumed
subsequent to event hooks being invoked before they are acted upon.
Previously, options like ``autoflush`` would have been already evaluated
at this point. The new ``identity_token`` option is also supported in
this mode and is now used by the horizontal sharding extension.
* The :class:`.ShardedSession` class replaces the
:paramref:`.ShardedSession.id_chooser` hook with a new hook
:paramref:`.ShardedSession.identity_chooser`, which no longer relies upon
the legacy :class:`_orm.Query` object.
:paramref:`.ShardedSession.id_chooser` is still accepted in place of
:paramref:`.ShardedSession.identity_chooser` with a deprecation warning.
.. change::
:tags: usecase, orm
:tickets: 9015
The behavior of "joining an external transaction into a Session" has been
revised and improved, allowing explicit control over how the
:class:`_orm.Session` will accommodate an incoming
:class:`_engine.Connection` that already has a transaction and possibly a
savepoint already established. The new parameter
:paramref:`_orm.Session.join_transaction_mode` includes a series of option
values which can accommodate the existing transaction in several ways, most
importantly allowing a :class:`_orm.Session` to operate in a fully
transactional style using savepoints exclusively, while leaving the
externally initiated transaction non-committed and active under all
circumstances, allowing test suites to rollback all changes that take place
within tests.
Additionally, revised the :meth:`_orm.Session.close` method to fully close
out savepoints that may still be present, which also allows the
"external transaction" recipe to proceed without warnings if the
:class:`_orm.Session` did not explicitly end its own SAVEPOINT
transactions.
.. seealso::
:ref:`change_9015`
.. change::
:tags: bug, sql
:tickets: 8988
Added test support to ensure that all compiler ``visit_xyz()`` methods
across all :class:`.Compiler` implementations in SQLAlchemy accept a
``**kw`` parameter, so that all compilers accept additional keyword
arguments under all circumstances.
.. change::
:tags: bug, postgresql
:tickets: 8984
The :meth:`_postgresql.Range.__eq___` will now return ``NotImplemented``
when comparing with an instance of a different class, instead of raising
an :exc:`AttributeError` exception.
.. change::
:tags: bug, sql
:tickets: 6114
The :meth:`.SQLCompiler.construct_params` method, as well as the
:attr:`.SQLCompiler.params` accessor, will now return the
exact parameters that correspond to a compiled statement that used
the ``render_postcompile`` parameter to compile. Previously,
the method returned a parameter structure that by itself didn't correspond
to either the original parameters or the expanded ones.
Passing a new dictionary of parameters to
:meth:`.SQLCompiler.construct_params` for a :class:`.SQLCompiler` that was
constructed with ``render_postcompile`` is now disallowed; instead, to make
a new SQL string and parameter set for an alternate set of parameters, a
new method :meth:`.SQLCompiler.construct_expanded_state` is added which
will produce a new expanded form for the given parameter set, using the
:class:`.ExpandedState` container which includes a new SQL statement
and new parameter dictionary, as well as a positional parameter tuple.
.. change::
:tags: bug, orm
:tickets: 8703, 8997, 8996
A series of changes and improvements regarding
:meth:`_orm.Session.refresh`. The overall change is that primary key
attributes for an object are now included in a refresh operation
unconditionally when relationship-bound attributes are to be refreshed,
even if not expired and even if not specified in the refresh.
* Improved :meth:`_orm.Session.refresh` so that if autoflush is enabled
(as is the default for :class:`_orm.Session`), the autoflush takes place
at an earlier part of the refresh process so that pending primary key
changes are applied without errors being raised. Previously, this
autoflush took place too late in the process and the SELECT statement
would not use the correct key to locate the row and an
:class:`.InvalidRequestError` would be raised.
* When the above condition is present, that is, unflushed primary key
changes are present on the object, but autoflush is not enabled,
the refresh() method now explicitly disallows the operation to proceed,
and an informative :class:`.InvalidRequestError` is raised asking that
the pending primary key changes be flushed first. Previously,
this use case was simply broken and :class:`.InvalidRequestError`
would be raised anyway. This restriction is so that it's safe for the
primary key attributes to be refreshed, as is necessary for the case of
being able to refresh the object with relationship-bound secondary
eagerloaders also being emitted. This rule applies in all cases to keep
API behavior consistent regardless of whether or not the PK cols are
actually needed in the refresh, as it is unusual to be refreshing
some attributes on an object while keeping other attributes "pending"
in any case.
* The :meth:`_orm.Session.refresh` method has been enhanced such that
attributes which are :func:`_orm.relationship`-bound and linked to an
eager loader, either at mapping time or via last-used loader options,
will be refreshed in all cases even when a list of attributes is passed
that does not include any columns on the parent row. This builds upon the
feature first implemented for non-column attributes as part of
:ticket:`1763` fixed in 1.4 allowing eagerly-loaded relationship-bound
attributes to participate in the :meth:`_orm.Session.refresh` operation.
If the refresh operation does not indicate any columns on the parent row
to be refreshed, the primary key columns will nonetheless be included
in the refresh operation, which allows the load to proceed into the
secondary relationship loaders indicated as it does normally.
Previously an :class:`.InvalidRequestError` error would be raised
for this condition (:ticket:`8703`)
* Fixed issue where an unnecessary additional SELECT would be emitted in
the case where :meth:`_orm.Session.refresh` were called with a
combination of expired attributes, as well as an eager loader such as
:func:`_orm.selectinload` that emits a "secondary" query, if the primary
key attributes were also in an expired state. As the primary key
attributes are now included in the refresh automatically, there is no
additional load for these attributes when a relationship loader
goes to select for them (:ticket:`8997`)
* Fixed regression caused by :ticket:`8126` released in 2.0.0b1 where the
:meth:`_orm.Session.refresh` method would fail with an
``AttributeError``, if passed both an expired column name as well as the
name of a relationship-bound attribute that was linked to a "secondary"
eagerloader such as the :func:`_orm.selectinload` eager loader
(:ticket:`8996`)
.. change::
:tags: bug, sql
:tickets: 8994
To accommodate for third party dialects with different character escaping
needs regarding bound parameters, the system by which SQLAlchemy "escapes"
(i.e., replaces with another character in its place) special characters in
bound parameter names has been made extensible for third party dialects,
using the :attr:`.SQLCompiler.bindname_escape_chars` dictionary which can
be overridden at the class declaration level on any :class:`.SQLCompiler`
subclass. As part of this change, also added the dot ``"."`` as a default
"escaped" character.
.. change::
:tags: orm, feature
:tickets: 8889
Added a new default value for the :paramref:`.Mapper.eager_defaults`
parameter "auto", which will automatically fetch table default values
during a unit of work flush, if the dialect supports RETURNING for the
INSERT being run, as well as
:ref:`insertmanyvalues <engine_insertmanyvalues>` available. Eager fetches
for server-side UPDATE defaults, which are very uncommon, continue to only
take place if :paramref:`.Mapper.eager_defaults` is set to ``True``, as
there is no batch-RETURNING form for UPDATE statements.
.. change::
:tags: usecase, orm
:tickets: 8973
Removed the requirement that the ``__allow_unmapped__`` attribute be used
on Declarative Dataclass Mapped class when non-``Mapped[]`` annotations are
detected; previously, an error message that was intended to support legacy
ORM typed mappings would be raised, which additionally did not mention
correct patterns to use with Dataclasses specifically. This error message
is now no longer raised if :meth:`_orm.registry.mapped_as_dataclass` or
:class:`_orm.MappedAsDataclass` is used.
.. seealso::
:ref:`orm_declarative_native_dataclasses_non_mapped_fields`
.. change::
:tags: bug, orm
:tickets: 8168
Improved a fix first made in version 1.4 for :ticket:`8456` which scaled
back the usage of internal "polymorphic adapters", that are used to render
ORM queries when the :paramref:`_orm.Mapper.with_polymorphic` parameter is
used. These adapters, which are very complex and error prone, are now used
only in those cases where an explicit user-supplied subquery is used for
:paramref:`_orm.Mapper.with_polymorphic`, which includes only the use case
of concrete inheritance mappings that use the
:func:`_orm.polymorphic_union` helper, as well as the legacy use case of
using an aliased subquery for joined inheritance mappings, which is not
needed in modern use.
For the most common case of joined inheritance mappings that use the
built-in polymorphic loading scheme, which includes those which make use of
the :paramref:`_orm.Mapper.polymorphic_load` parameter set to ``inline``,
polymorphic adapters are now no longer used. This has both a positive
performance impact on the construction of queries as well as a
substantial simplification of the internal query rendering process.
The specific issue targeted was to allow a :func:`_orm.column_property`
to refer to joined-inheritance classes within a scalar subquery, which now
works as intuitively as is feasible.
.. changelog::
:version: 2.0.0b4
:released: January 26, 2023
:released: December 5, 2022
.. change::
:tags: usecase, orm
:tickets: 8859
Added support custom user-defined types which extend the Python
``enum.Enum`` base class to be resolved automatically
to SQLAlchemy :class:`.Enum` SQL types, when using the Annotated
Declarative Table feature. The feature is made possible through new
lookup features added to the ORM type map feature, and includes support
for changing the arguments of the :class:`.Enum` that's generated by
default as well as setting up specific ``enum.Enum`` types within
the map with specific arguments.
.. seealso::
:ref:`orm_declarative_mapped_column_enums`
.. change::
:tags: bug, typing
:tickets: 8783
Adjusted internal use of the Python ``enum.IntFlag`` class which changed
its behavioral contract in Python 3.11. This was not causing runtime
failures however caused typing runs to fail under Python 3.11.
.. change::
:tags: usecase, typing
:tickets: 8847
Added a new type :class:`.SQLColumnExpression` which may be indicated in
user code to represent any SQL column oriented expression, including both
those based on :class:`.ColumnElement` as well as on ORM
:class:`.QueryableAttribute`. This type is a real class, not an alias, so
can also be used as the foundation for other objects. An additional
ORM-specific subclass :class:`.SQLORMExpression` is also included.
.. change::
:tags: bug, typing
:tickets: 8667, 6810
The ``sqlalchemy.ext.mutable`` extension and ``sqlalchemy.ext.automap``
extensions are now fully pep-484 typed. Huge thanks to Gleb Kisenkov for
their efforts on this.
.. change::
:tags: bug, sql
:tickets: 8849
The approach to the ``numeric`` pep-249 paramstyle has been rewritten, and
is now fully supported, including by features such as "expanding IN" and
"insertmanyvalues". Parameter names may also be repeated in the source SQL
construct which will be correctly represented within the numeric format
using a single parameter. Introduced an additional numeric paramstyle
called ``numeric_dollar``, which is specifically what's used by the asyncpg
dialect; the paramstyle is equivalent to ``numeric`` except numeric
indicators are indicated by a dollar-sign rather than a colon. The asyncpg
dialect now uses ``numeric_dollar`` paramstyle directly, rather than
compiling to ``format`` style first.
The ``numeric`` and ``numeric_dollar`` paramstyles assume that the target
backend is capable of receiving the numeric parameters in any order,
and will match the given parameter values to the statement based on
matching their position (1-based) to the numeric indicator. This is the
normal behavior of "numeric" paramstyles, although it was observed that
the SQLite DBAPI implements a not-used "numeric" style that does not honor
parameter ordering.
.. change::
:tags: usecase, postgresql
:tickets: 8765
Complementing :ticket:`8690`, new comparison methods such as
:meth:`_postgresql.Range.adjacent_to`,
:meth:`_postgresql.Range.difference`, :meth:`_postgresql.Range.union`,
etc., were added to the PG-specific range objects, bringing them in par
with the standard operators implemented by the underlying
:attr:`_postgresql.AbstractRange.comparator_factory`.
In addition, the ``__bool__()`` method of the class has been corrected to
be consistent with the common Python containers behavior as well as how
other popular PostgreSQL drivers do: it now tells whether the range
instance is *not* empty, rather than the other way around.
Pull request courtesy Lele Gaifax.
.. change::
:tags: bug, sql
:tickets: 8770
Adjusted the rendering of ``RETURNING``, in particular when using
:class:`_sql.Insert`, such that it now renders columns using the same logic
as that of the :class:`.Select` construct to generate labels, which will
include disambiguating labels, as well as that a SQL function surrounding a
named column will be labeled using the column name itself. This establishes
better cross-compatibility when selecting rows from either :class:`.Select`
constructs or from DML statements that use :meth:`.UpdateBase.returning`. A
narrower scale change was also made for the 1.4 series that adjusted the
function label issue only.
.. change::
:tags: change, postgresql, asyncpg
:tickets: 8926
Changed the paramstyle used by asyncpg from ``format`` to
``numeric_dollar``. This has two main benefits since it does not require
additional processing of the statement and allows for duplicate parameters
to be present in the statements.
.. change::
:tags: bug, orm
:tickets: 8888
Fixed issue where use of an unknown datatype within a :class:`.Mapped`
annotation for a column-based attribute would silently fail to map the
attribute, rather than reporting an exception; an informative exception
message is now raised.
.. change::
:tags: bug, orm
:tickets: 8777
Fixed a suite of issues involving :class:`.Mapped` use with dictionary
types, such as ``Mapped[Dict[str, str] | None]``, would not be correctly
interpreted in Declarative ORM mappings. Support to correctly
"de-optionalize" this type including for lookup in ``type_annotation_map``
has been fixed.
.. change::
:tags: feature, orm
:tickets: 8822
Added a new parameter :paramref:`_orm.mapped_column.use_existing_column` to
accommodate the use case of a single-table inheritance mapping that uses
the pattern of more than one subclass indicating the same column to take
place on the superclass. This pattern was previously possible by using
:func:`_orm.declared_attr` in conjunction with locating the existing column
in the ``.__table__`` of the superclass, however is now updated to work
with :func:`_orm.mapped_column` as well as with pep-484 typing, in a
simple and succinct way.
.. seealso::
:ref:`orm_inheritance_column_conflicts`
.. change::
:tags: bug, mssql
:tickets: 8917
Fixed regression caused by the combination of :ticket:`8177`, re-enable
setinputsizes for SQL server unless fast_executemany + DBAPI executemany is
used for a statement, along with :ticket:`6047`, implement
"insertmanyvalues", which bypasses DBAPI executemany in place of a custom
DBAPI execute for INSERT statements. setinputsizes would incorrectly not be
used for a multiple parameter-set INSERT statement that used
"insertmanyvalues" if fast_executemany were turned on, as the check would
incorrectly assume this is a DBAPI executemany call. The "regression"
would then be that the "insertmanyvalues" statement format is apparently
slightly more sensitive to multiple rows that don't use the same types
for each row, so in such a case setinputsizes is especially needed.
The fix repairs the fast_executemany check so that it only disables
setinputsizes if true DBAPI executemany is to be used.
.. change::
:tags: bug, orm, performance
:tickets: 8796
Additional performance enhancements within ORM-enabled SQL statements,
specifically targeting callcounts within the construction of ORM
statements, using combinations of :func:`_orm.aliased` with
:func:`_sql.union` and similar "compound" constructs, in addition to direct
performance improvements to the ``corresponding_column()`` internal method
that is used heavily by the ORM by constructs like :func:`_orm.aliased` and
similar.
.. change::
:tags: bug, postgresql
:tickets: 8884
Added additional type-detection for the new PostgreSQL
:class:`_postgresql.Range` type, where previous cases that allowed the
psycopg2-native range objects to be received directly by the DBAPI without
SQLAlchemy intercepting them stopped working, as we now have our own value
object. The :class:`_postgresql.Range` object has been enhanced such that
SQLAlchemy Core detects it in otherwise ambiguous situations (such as
comparison to dates) and applies appropriate bind handlers. Pull request
courtesy Lele Gaifax.
.. change::
:tags: bug, orm
:tickets: 8880
Fixed bug in :ref:`orm_declarative_native_dataclasses` feature where using
plain dataclass fields with the ``__allow_unmapped__`` directive in a
mapping would not create a dataclass with the correct class-level state for
those fields, copying the raw ``Field`` object to the class inappropriately
after dataclasses itself had replaced the ``Field`` object with the
class-level default value.
.. change::
:tags: usecase, orm extensions
:tickets: 8878
Added support for the :func:`.association_proxy` extension function to
take part within Python ``dataclasses`` configuration, when using
the native dataclasses feature described at
:ref:`orm_declarative_native_dataclasses`. Included are attribute-level
arguments including :paramref:`.association_proxy.init` and
:paramref:`.association_proxy.default_factory`.
Documentation for association proxy has also been updated to use
"Annotated Declarative Table" forms within examples, including type
annotations used for :class:`.AssocationProxy` itself.
.. change::
:tags: bug, typing
Corrected typing support for the :paramref:`_orm.relationship.secondary`
argument which may also accept a callable (lambda) that returns a
:class:`.FromClause`.
.. change::
:tags: bug, orm, regression
:tickets: 8812
Fixed regression where flushing a mapped class that's mapped against a
subquery, such as a direct mapping or some forms of concrete table
inheritance, would fail if the :paramref:`_orm.Mapper.eager_defaults`
parameter were used.
.. change::
:tags: bug, schema
:tickets: 8925
Stricter rules are in place for appending of :class:`.Column` objects to
:class:`.Table` objects, both moving some previous deprecation warnings to
exceptions, and preventing some previous scenarios that would cause
duplicate columns to appear in tables, when
:paramref:`.Table.extend_existing` were set to ``True``, for both
programmatic :class:`.Table` construction as well as during reflection
operations.
See :ref:`change_8925` for a rundown of these changes.
.. seealso::
:ref:`change_8925`
.. change::
:tags: usecase, orm
:tickets: 8905
Added :paramref:`_orm.mapped_column.compare` parameter to relevant ORM
attribute constructs including :func:`_orm.mapped_column`,
:func:`_orm.relationship` etc. to provide for the Python dataclasses
``compare`` parameter on ``field()``, when using the
:ref:`orm_declarative_native_dataclasses` feature. Pull request courtesy
Simon Schiele.
.. change::
:tags: sql, usecase
:tickets: 6289
Added :class:`_expression.ScalarValues` that can be used as a column
element allowing using :class:`_expression.Values` inside ``IN`` clauses
or in conjunction with ``ANY`` or ``ALL`` collection aggregates.
This new class is generated using the method
:meth:`_expression.Values.scalar_values`.
The :class:`_expression.Values` instance is now coerced to a
:class:`_expression.ScalarValues` when used in a ``IN`` or ``NOT IN``
operation.
.. change::
:tags: bug, orm
:tickets: 8853
Fixed regression in 2.0.0b3 caused by :ticket:`8759` where indicating the
:class:`.Mapped` name using a qualified name such as
``sqlalchemy.orm.Mapped`` would fail to be recognized by Declarative as
indicating the :class:`.Mapped` construct.
.. change::
:tags: bug, typing
:tickets: 8842
Improved the typing for :class:`.sessionmaker` and
:class:`.async_sessionmaker`, so that the default type of their return value
will be :class:`.Session` or :class:`.AsyncSession`, without the need to
type this explicitly. Previously, Mypy would not automaticaly infer these
return types from its generic base.
As part of this change, arguments for :class:`.Session`,
:class:`.AsyncSession`, :class:`.sessionmaker` and
:class:`.async_sessionmaker` beyond the initial "bind" argument have been
made keyword-only, which includes parameters that have always been
documented as keyword arguments, such as :paramref:`.Session.autoflush`,
:paramref:`.Session.class_`, etc.
Pull request courtesy Sam Bull.
.. change::
:tags: bug, typing
:tickets: 8776
Fixed issue where passing a callbale function returning an iterable
of column elements to :paramref:`_orm.relationship.order_by` was
flagged as an error in type checkers.
.. changelog::
:version: 2.0.0b3
:released: January 26, 2023
:released: November 4, 2022
.. change::
:tags: bug, orm, declarative
:tickets: 8759
Added support in ORM declarative annotations for class names specified for
:func:`_orm.relationship`, as well as the name of the :class:`_orm.Mapped`
symbol itself, to be different names than their direct class name, to
support scenarios such as where :class:`_orm.Mapped` is imported as
``from sqlalchemy.orm import Mapped as M``, or where related class names
are imported with an alternate name in a similar fashion. Additionally, a
target class name given as the lead argument for :func:`_orm.relationship`
will always supersede the name given in the left hand annotation, so that
otherwise un-importable names that also don't match the class name can
still be used in annotations.
.. change::
:tags: bug, orm, declarative
:tickets: 8692
Improved support for legacy 1.4 mappings that use annotations which don't
include ``Mapped[]``, by ensuring the ``__allow_unmapped__`` attribute can
be used to allow such legacy annotations to pass through Annotated
Declarative without raising an error and without being interpreted in an
ORM runtime context. Additionally improved the error message generated when
this condition is detected, and added more documentation for how this
situation should be handled. Unfortunately the 1.4 WARN_SQLALCHEMY_20
migration warning cannot detect this particular configurational issue at
runtime with its current architecture.
.. change::
:tags: usecase, postgresql
:tickets: 8690
Refined the new approach to range objects described at :ref:`change_7156`
to accommodate driver-specific range and multirange objects, to better
accommodate both legacy code as well as when passing results from raw SQL
result sets back into new range or multirange expressions.
.. change::
:tags: usecase, engine
:tickets: 8717
Added new parameter :paramref:`.PoolEvents.reset.reset_state` parameter to
the :meth:`.PoolEvents.reset` event, with deprecation logic in place that
will continue to accept event hooks using the previous set of arguments.
This indicates various state information about how the reset is taking
place and is used to allow custom reset schemes to take place with full
context given.
Within this change a fix that's also backported to 1.4 is included which
re-enables the :meth:`.PoolEvents.reset` event to continue to take place
under all circumstances, including when :class:`.Connection` has already
"reset" the connection.
The two changes together allow custom reset schemes to be implemented using
the :meth:`.PoolEvents.reset` event, instead of the
:meth:`.PoolEvents.checkin` event (which continues to function as it always
has).
.. change::
:tags: bug, orm, declarative
:tickets: 8705
Changed a fundamental configuration behavior of :class:`.Mapper`, where
:class:`_schema.Column` objects that are explicitly present in the
:paramref:`_orm.Mapper.properties` dictionary, either directly or enclosed
within a mapper property object, will now be mapped within the order of how
they appear within the mapped :class:`.Table` (or other selectable) itself
(assuming they are in fact part of that table's list of columns), thereby
maintaining the same order of columns in the mapped selectable as is
instrumented on the mapped class, as well as what renders in an ORM SELECT
statement for that mapper. Previously (where "previously" means since
version 0.0.1), :class:`.Column` objects in the
:paramref:`_orm.Mapper.properties` dictionary would always be mapped first,
ahead of when the other columns in the mapped :class:`.Table` would be
mapped, causing a discrepancy in the order in which the mapper would
assign attributes to the mapped class as well as the order in which they
would render in statements.
The change most prominently takes place in the way that Declarative
assigns declared columns to the :class:`.Mapper`, specifically how
:class:`.Column` (or :func:`_orm.mapped_column`) objects are handled
when they have a DDL name that is explicitly different from the mapped
attribute name, as well as when constructs such as :func:`_orm.deferred`
etc. are used. The new behavior will see the column ordering within
the mapped :class:`.Table` being the same order in which the attributes
are mapped onto the class, assigned within the :class:`.Mapper` itself,
and rendered in ORM statements such as SELECT statements, independent
of how the :class:`_schema.Column` was configured against the
:class:`.Mapper`.
.. change::
:tags: feature, engine
:tickets: 8710
To better support the use case of iterating :class:`.Result` and
:class:`.AsyncResult` objects where user-defined exceptions may interrupt
the iteration, both objects as well as variants such as
:class:`.ScalarResult`, :class:`.MappingResult`,
:class:`.AsyncScalarResult`, :class:`.AsyncMappingResult` now support
context manager usage, where the result will be closed at the end of
the context manager block.
In addition, ensured that all the above
mentioned :class:`.Result` objects include a :meth:`.Result.close` method
as well as :attr:`.Result.closed` accessors, including
:class:`.ScalarResult` and :class:`.MappingResult` which previously did
not have a ``.close()`` method.
.. seealso::
:ref:`change_8710`
.. change::
:tags: bug, typing
Corrected various typing issues within the engine and async engine
packages.
.. change::
:tags: bug, orm, declarative
:tickets: 8718
Fixed issue in new dataclass mapping feature where a column declared on the
decalrative base / abstract base / mixin would leak into the constructor
for an inheriting subclass under some circumstances.
.. change::
:tags: bug, orm declarative
:tickets: 8742
Fixed issues within the declarative typing resolver (i.e. which resolves
``ForwardRef`` objects) where types that were declared for columns in one
particular source file would raise ``NameError`` when the ultimate mapped
class were in another source file. The types are now resolved in terms
of the module for each class in which the types are used.
.. change::
:tags: feature, postgresql
:tickets: 8706
Added new methods :meth:`_postgresql.Range.contains` and
:meth:`_postgresql.Range.contained_by` to the new :class:`.Range` data
object, which mirror the behavior of the PostgreSQL ``@>`` and ``<@``
operators, as well as the
:meth:`_postgresql.AbstractRange.comparator_factory.contains` and
:meth:`_postgresql.AbstractRange.comparator_factory.contained_by` SQL
operator methods. Pull request courtesy Lele Gaifax.
.. changelog::
:version: 2.0.0b2
:released: January 26, 2023
:released: October 20, 2022
.. change::
:tags: bug, orm
:tickets: 8656
Removed the warning that emits when using ORM-enabled update/delete
regarding evaluation of columns by name, first added in :ticket:`4073`;
this warning actually covers up a scenario that otherwise could populate
the wrong Python value for an ORM mapped attribute depending on what the
actual column is, so this deprecated case is removed. In 2.0, ORM enabled
update/delete uses "auto" for "synchronize_session", which should do the
right thing automatically for any given UPDATE expression.
.. change::
:tags: bug, mssql
:tickets: 8661
Fixed regression caused by SQL Server pyodbc change :ticket:`8177` where we
now use ``setinputsizes()`` by default; for VARCHAR, this fails if the
character size is greater than 4000 (or 2000, depending on data) characters
as the incoming datatype is NVARCHAR, which has a limit of 4000 characters,
despite the fact that VARCHAR can handle unlimited characters. Additional
pyodbc-specific typing information is now passed to ``setinputsizes()``
when the datatype's size is > 2000 characters. The change is also applied
to the :class:`_types.JSON` type which was also impacted by this issue for large
JSON serializations.
.. change::
:tags: bug, typing
:tickets: 8645
Fixed typing issue where pylance strict mode would report "instance
variable overrides class variable" when using a method to define
``__tablename__``, ``__mapper_args__`` or ``__table_args__``.
.. change::
:tags: mssql, bug
:tickets: 7211
The :class:`.Sequence` construct restores itself to the DDL behavior it
had prior to the 1.4 series, where creating a :class:`.Sequence` with
no additional arguments will emit a simple ``CREATE SEQUENCE`` instruction
**without** any additional parameters for "start value". For most backends,
this is how things worked previously in any case; **however**, for
MS SQL Server, the default value on this database is
``-2**63``; to prevent this generally impractical default
from taking effect on SQL Server, the :paramref:`.Sequence.start` parameter
should be provided. As usage of :class:`.Sequence` is unusual
for SQL Server which for many years has standardized on ``IDENTITY``,
it is hoped that this change has minimal impact.
.. seealso::
:ref:`change_7211`
.. change::
:tags: bug, declarative, orm
:tickets: 8665
Improved the :class:`.DeclarativeBase` class so that when combined with
other mixins like :class:`.MappedAsDataclass`, the order of the classes may
be in either order.
.. change::
:tags: usecase, declarative, orm
:tickets: 8665
Added support for mapped classes that are also ``Generic`` subclasses,
to be specified as a ``GenericAlias`` object (e.g. ``MyClass[str]``)
within statements and calls to :func:`_sa.inspect`.
.. change::
:tags: bug, orm, declarative
:tickets: 8668
Fixed bug in new ORM typed declarative mappings where the ability
to use ``Optional[MyClass]`` or similar forms such as ``MyClass | None``
in the type annotation for a many-to-one relationship was not implemented,
leading to errors. Documentation has also been added for this use
case to the relationship configuration documentation.
.. change::
:tags: bug, typing
:tickets: 8644
Fixed typing issue where pylance strict mode would report "partially
unknown" datatype for the :func:`_orm.mapped_column` construct.
.. change::
:tags: bug, regression, sql
:tickets: 8639
Fixed bug in new "insertmanyvalues" feature where INSERT that included a
subquery with :func:`_sql.bindparam` inside of it would fail to render
correctly in "insertmanyvalues" format. This affected psycopg2 most
directly as "insertmanyvalues" is used unconditionally with this driver.
.. change::
:tags: bug, orm, declarative
:tickets: 8688
Fixed issue with new dataclass mapping feature where arguments passed to
the dataclasses API could sometimes be mis-ordered when dealing with mixins
that override :func:`_orm.mapped_column` declarations, leading to
initializer problems.
.. changelog::
:version: 2.0.0b1
:released: January 26, 2023
:released: October 13, 2022
.. change::
:tags: bug, sql
:tickets: 7888
The FROM clauses that are established on a :func:`_sql.select` construct
when using the :meth:`_sql.Select.select_from` method will now render first
in the FROM clause of the rendered SELECT, which serves to maintain the
ordering of clauses as was passed to the :meth:`_sql.Select.select_from`
method itself without being affected by the presence of those clauses also
being mentioned in other parts of the query. If other elements of the
:class:`_sql.Select` also generate FROM clauses, such as the columns clause
or WHERE clause, these will render after the clauses delivered by
:meth:`_sql.Select.select_from` assuming they were not explictly passed to
:meth:`_sql.Select.select_from` also. This improvement is useful in those
cases where a particular database generates a desirable query plan based on
a particular ordering of FROM clauses and allows full control over the
ordering of FROM clauses.
.. change::
:tags: usecase, sql
:tickets: 7998
Altered the compilation mechanics of the :class:`_dml.Insert` construct
such that the "autoincrement primary key" column value will be fetched via
``cursor.lastrowid`` or RETURNING even if present in the parameter set or
within the :meth:`_dml.Insert.values` method as a plain bound value, for
single-row INSERT statements on specific backends that are known to
generate autoincrementing values even when explicit NULL is passed. This
restores a behavior that was in the 1.3 series for both the use case of
separate parameter set as well as :meth:`_dml.Insert.values`. In 1.4, the
parameter set behavior unintentionally changed to no longer do this, but
the :meth:`_dml.Insert.values` method would still fetch autoincrement
values up until 1.4.21 where :ticket:`6770` changed the behavior yet again
again unintentionally as this use case was never covered.
The behavior is now defined as "working" to suit the case where databases
such as SQLite, MySQL and MariaDB will ignore an explicit NULL primary key
value and nonetheless invoke an autoincrement generator.
.. change::
:tags: change, postgresql
SQLAlchemy now requires PostgreSQL version 9 or greater.
Older versions may still work in some limited use cases.
.. change::
:tags: bug, orm
Fixed issue where the :meth:`_orm.registry.map_declaratively` method
would return an internal "mapper config" object and not the
:class:`.Mapper` object as stated in the API documentation.
.. change::
:tags: sybase, removed
:tickets: 7258
Removed the "sybase" internal dialect that was deprecated in previous
SQLAlchemy versions. Third party dialect support is available.
.. seealso::
:ref:`external_toplevel`
.. change::
:tags: bug, orm
:tickets: 7463
Fixed performance regression which appeared at least in version 1.3 if not
earlier (sometime after 1.0) where the loading of deferred columns, those
explicitly mapped with :func:`_orm.defer` as opposed to non-deferred
columns that were expired, from a joined inheritance subclass would not use
the "optimized" query which only queried the immediate table that contains
the unloaded columns, instead running a full ORM query which would emit a
JOIN for all base tables, which is not necessary when only loading columns
from the subclass.
.. change::
:tags: bug, sql
:tickets: 7791
The :paramref:`.Enum.length` parameter, which sets the length of the
``VARCHAR`` column for non-native enumeration types, is now used
unconditionally when emitting DDL for the ``VARCHAR`` datatype, including
when the :paramref:`.Enum.native_enum` parameter is set to ``True`` for
target backends that continue to use ``VARCHAR``. Previously the parameter
would be erroneously ignored in this case. The warning previously emitted
for this case is now removed.
.. change::
:tags: bug, orm
:tickets: 6986
The internals for the :class:`_orm.Load` object and related loader strategy
patterns have been mostly rewritten, to take advantage of the fact that
only attribute-bound paths, not strings, are now supported. The rewrite
hopes to make it more straightforward to address new use cases and subtle
issues within the loader strategy system going forward.
.. change::
:tags: usecase, orm
Added :paramref:`_orm.load_only.raiseload` parameter to the
:func:`_orm.load_only` loader option, so that the unloaded attributes may
have "raise" behavior rather than lazy loading. Previously there wasn't
really a way to do this with the :func:`_orm.load_only` option directly.
.. change::
:tags: change, engine
:tickets: 7122
Some small API changes regarding engines and dialects:
* The :meth:`.Dialect.set_isolation_level`, :meth:`.Dialect.get_isolation_level`,
:meth:
dialect methods will always be passed the raw DBAPI connection
* The :class:`.Connection` and :class:`.Engine` classes no longer share a base
``Connectable`` superclass, which has been removed.
* Added a new interface class :class:`.PoolProxiedConnection` - this is the
public facing interface for the familiar :class:`._ConnectionFairy`
class which is nonetheless a private class.
.. change::
:tags: feature, sql
:tickets: 3482
Added long-requested case-insensitive string operators
:meth:`_sql.ColumnOperators.icontains`,
:meth:`_sql.ColumnOperators.istartswith`,
:meth:`_sql.ColumnOperators.iendswith`, which produce case-insensitive
LIKE compositions (using ILIKE on PostgreSQL, and the LOWER() function on
all other backends) to complement the existing LIKE composition operators
:meth:`_sql.ColumnOperators.contains`,
:meth:`_sql.ColumnOperators.startswith`, etc. Huge thanks to Matias
Martinez Rebori for their meticulous and complete efforts in implementing
these new methods.
.. change::
:tags: usecase, postgresql
:tickets: 8138
Added literal type rendering for the :class:`_sqltypes.ARRAY` and
:class:`_postgresql.ARRAY` datatypes. The generic stringify will render
using brackets, e.g. ``[1, 2, 3]`` and the PostgreSQL specific will use the
ARRAY literal e.g. ``ARRAY[1, 2, 3]``. Multiple dimensions and quoting
are also taken into account.
.. change::
:tags: bug, orm
:tickets: 8166
Made an improvement to the "deferred" / "load_only" set of strategy options
where if a certain object is loaded from two different logical paths within
one query, attributes that have been configured by at least one of the
options to be populated will be populated in all cases, even if other load
paths for that same object did not set this option. previously, it was
based on randomness as to which "path" addressed the object first.
.. change::
:tags: feature, orm, sql
:tickets: 6047
Added new feature to all included dialects that support RETURNING
called "insertmanyvalues". This is a generalization of the
"fast executemany" feature first introduced for the psycopg2 driver
in 1.4 at :ref:`change_5263`, which allows the ORM to batch INSERT
statements into a much more efficient SQL structure while still being
able to fetch newly generated primary key and SQL default values
using RETURNING.
The feature now applies to the many dialects that support RETURNING along
with multiple VALUES constructs for INSERT, including all PostgreSQL
drivers, SQLite, MariaDB, MS SQL Server. Separately, the Oracle dialect
also gains the same capability using native cx_Oracle or OracleDB features.
.. change::
:tags: bug, engine
:tickets: 8523
The :class:`_pool.QueuePool` now ignores ``max_overflow`` when
``pool_size=0``, properly making the pool unlimited in all cases.
.. change::
:tags: bug, sql
:tickets: 7909
The in-place type detection for Python integers, as occurs with an
expression such as ``literal(25)``, will now apply value-based adaption as
well to accommodate Python large integers, where the datatype determined
will be :class:`.BigInteger` rather than :class:`.Integer`. This
accommodates for dialects such as that of asyncpg which both sends implicit
typing information to the driver as well as is sensitive to numeric scale.
.. change::
:tags: postgresql, mssql, change
:tickets: 7225
The parameter :paramref:`_types.UUID.as_uuid` of :class:`_types.UUID`,
previously specific to the PostgreSQL dialect but now generalized for Core
(along with a new backend-agnostic :class:`_types.Uuid` datatype) now
defaults to ``True``, indicating that Python ``UUID`` objects are accepted
by this datatype by default. Additionally, the SQL Server
:class:`_mssql.UNIQUEIDENTIFIER` datatype has been converted to be a
UUID-receiving type; for legacy code that makes use of
:class:`_mssql.UNIQUEIDENTIFIER` using string values, set the
:paramref:`_mssql.UNIQUEIDENTIFIER.as_uuid` parameter to ``False``.
.. change::
:tags: bug, orm
:tickets: 8344
Fixed issue in ORM enabled UPDATE when the statement is created against a
joined-inheritance subclass, updating only local table columns, where the
"fetch" synchronization strategy would not render the correct RETURNING
clause for databases that use RETURNING for fetch synchronization.
Also adjusts the strategy used for RETURNING in UPDATE FROM and
DELETE FROM statements.
.. change::
:tags: usecase, mariadb
:tickets: 8344
Added a new execution option ``is_delete_using=True``, which is consumed
by the ORM when using an ORM-enabled DELETE statement in conjunction with
the "fetch" synchronization strategy; this option indicates that the
DELETE statement is expected to use multiple tables, which on MariaDB
is the DELETE..USING syntax. The option then indicates that
RETURNING (newly implemented in SQLAlchemy 2.0 for MariaDB
for :ticket:`7011`) should not be used for databases that are known
to not support "DELETE..USING..RETURNING" syntax, even though they
support "DELETE..USING", which is MariaDB's current capability.
The rationale for this option is that the current workings of ORM-enabled
DELETE doesn't know up front if a DELETE statement is against multiple
tables or not until compilation occurs, which is cached in any case, yet it
needs to be known so that a SELECT for the to-be-deleted row can be emitted
up front. Instead of applying an across-the-board performance penalty for
all DELETE statements by proactively checking them all for this
relatively unusual SQL pattern, the ``is_delete_using=True`` execution
option is requested via a new exception message that is raised
within the compilation step. This exception message is specifically
(and only) raised when: the statement is an ORM-enabled DELETE where
the "fetch" synchronization strategy has been requested; the
backend is MariaDB or other backend with this specific limitation;
the statement has been detected within the initial compilation
that it would otherwise emit "DELETE..USING..RETURNING". By applying
the execution option, the ORM knows to run a SELECT upfront instead.
A similar option is implemented for ORM-enabled UPDATE but there is not
currently a backend where it is needed.
.. change::
:tags: bug, orm, asyncio
:tickets: 7703
Removed the unused ``**kw`` arguments from
:class:`_asyncio.AsyncSession.begin` and
:class:`_asyncio.AsyncSession.begin_nested`. These kw aren't used and
appear to have been added to the API in error.
.. change::
:tags: feature, sql
:tickets: 8285
Added new syntax to the :attr:`.FromClause.c` collection on all
:class:`.FromClause` objects allowing tuples of keys to be passed to
``__getitem__()``, along with support for the :func:`_sql.select` construct
to handle the resulting tuple-like collection directly, allowing the syntax
``select(table.c['a', 'b', 'c'])`` to be possible. The sub-collection
returned is itself a :class:`.ColumnCollection` which is also directly
consumable by :func:`_sql.select` and similar now.
.. seealso::
:ref:`tutorial_selecting_columns`
.. change::
:tags: general, changed
:tickets: 7257
Migrated the codebase to remove all pre-2.0 behaviors and architectures
that were previously noted as deprecated for removal in 2.0, including,
but not limited to:
* removal of all Python 2 code, minimum version is now Python 3.7
* :class:`_engine.Engine` and :class:`_engine.Connection` now use the
new 2.0 style of working, which includes "autobegin", library level
autocommit removed, subtransactions and "branched" connections
removed
* Result objects use 2.0-style behaviors; :class:`_result.Row` is fully
a named tuple without "mapping" behavior, use :class:`_result.RowMapping`
for "mapping" behavior
* All Unicode encoding/decoding architecture has been removed from
SQLAlchemy. All modern DBAPI implementations support Unicode
transparently thanks to Python 3, so the ``convert_unicode`` feature
as well as related mechanisms to look for bytestrings in
DBAPI ``cursor.description`` etc. have been removed.
* The ``.bind`` attribute and parameter from :class:`.MetaData`,
:class:`.Table`, and from all DDL/DML/DQL elements that previously could
refer to a "bound engine"
* The standalone ``sqlalchemy.orm.mapper()`` function is removed; all
classical mapping should be done through the
:meth:`_orm.registry.map_imperatively` method of :class:`_orm.registry`.
* The :meth:`_orm.Query.join` method no longer accepts strings for
relationship names; the long-documented approach of using
``Class.attrname`` for join targets is now standard.
* :meth:`_orm.Query.join` no longer accepts the "aliased" and
"from_joinpoint" arguments
* :meth:`_orm.Query.join` no longer accepts chains of multiple join
targets in one method call.
* ``Query.from_self()``, ``Query.select_entity_from()`` and
``Query.with_polymorphic()`` are removed.
* The :paramref:`_orm.relationship.cascade_backrefs` parameter must now
remain at its new default of ``False``; the ``save-update`` cascade
no longer cascades along a backref.
* the :paramref:`_orm.Session.future` parameter must always be set to
``True``. 2.0-style transactional patterns for :class:`_orm.Session`
are now always in effect.
* Loader options no longer accept strings for attribute names. The
long-documented approach of using ``Class.attrname`` for loader option
targets is now standard.
* Legacy forms of :func:`_sql.select` removed, including
``select([cols])``, the "whereclause" and keyword parameters of
``some_table.select()``.
* Legacy "in-place mutator" methods on :class:`_sql.Select` such as
``append_whereclause()``, ``append_order_by()`` etc are removed.
* Removed the very old "dbapi_proxy" module, which in very early
SQLAlchemy releases was used to provide a transparent connection pool
over a raw DBAPI connection.
.. change::
:tags: feature, orm
:tickets: 8375
Added new parameter :paramref:`_orm.AttributeEvents.include_key`, which
will include the dictionary or list key for operations such as
``__setitem__()`` (e.g. ``obj[key] = value``) and ``__delitem__()`` (e.g.
``del obj[key]``), using a new keyword parameter "key" or "keys", depending
on event, e.g. :paramref:`_orm.AttributeEvents.append.key`,
:paramref:`_orm.AttributeEvents.bulk_replace.keys`. This allows event
handlers to take into account the key that was passed to the operation and
is of particular importance for dictionary operations working with
:class:`_orm.MappedCollection`.
.. change::
:tags: postgresql, usecase
:tickets: 7156, 8540
Adds support for PostgreSQL multirange types, introduced in PostgreSQL 14.
Support for PostgreSQL ranges and multiranges has now been generalized to
the psycopg3, psycopg2 and asyncpg backends, with room for further dialect
support, using a backend-agnostic :class:`_postgresql.Range` data object
that's constructor-compatible with the previously used psycopg2 object. See
the new documentation for usage patterns.
In addition, range type handling has been enhanced so that it automatically
renders type casts, so that in-place round trips for statements that don't
provide the database with any context don't require the :func:`_sql.cast`
construct to be explicit for the database to know the desired type
(discussed at :ticket:`8540`).
Thanks very much to @zeeeeeb for the pull request implementing and testing
the new datatypes and psycopg support.
.. seealso::
:ref:`change_7156`
:ref:`postgresql_ranges`
.. change::
:tags: usecase, oracle
:tickets: 8221
Oracle will now use FETCH FIRST N ROWS / OFFSET syntax for limit/offset
support by default for Oracle 12c and above. This syntax was already
available when :meth:`_sql.Select.fetch` were used directly, it's now
implied for :meth:`_sql.Select.limit` and :meth:`_sql.Select.offset` as
well.
.. change::
:tags: feature, orm
:tickets: 3162
Added new parameter :paramref:`_sql.Operators.op.python_impl`, available
from :meth:`_sql.Operators.op` and also when using the
:class:`_sql.Operators.custom_op` constructor directly, which allows an
in-Python evaluation function to be provided along with the custom SQL
operator. This evaluation function becomes the implementation used when the
operator object is used given plain Python objects as operands on both
sides, and in particular is compatible with the
``synchronize_session='evaluate'`` option used with
:ref:`orm_expression_update_delete`.
.. change::
:tags: schema, postgresql
:tickets: 5677
Added support for comments on :class:`.Constraint` objects, including
DDL and reflection; the field is added to the base :class:`.Constraint`
class and corresponding constructors, however PostgreSQL is the only
included backend to support the feature right now.
See parameters such as :paramref:`.ForeignKeyConstraint.comment`,
:paramref:`.UniqueConstraint.comment` or
:paramref:`.CheckConstraint.comment`.
.. change::
:tags: sqlite, usecase
:tickets: 8234
Added new parameter to SQLite for reflection methods called
``sqlite_include_internal=True``; when omitted, local tables that start
with the prefix ``sqlite_``, which per SQLite documentation are noted as
"internal schema" tables such as the ``sqlite_sequence`` table generated to
support "AUTOINCREMENT" columns, will not be included in reflection methods
that return lists of local objects. This prevents issues for example when
using Alembic autogenerate, which previously would consider these
SQLite-generated tables as being remove from the model.
.. seealso::
:ref:`sqlite_include_internal`
.. change::
:tags: feature, postgresql
:tickets: 7316
Added a new PostgreSQL :class:`_postgresql.DOMAIN` datatype, which follows
the same CREATE TYPE / DROP TYPE behaviors as that of PostgreSQL
:class:`_postgresql.ENUM`. Much thanks to David Baumgold for the efforts on
this.
.. seealso::
:class:`_postgresql.DOMAIN`
.. change::
:tags: change, postgresql
The :paramref:`_postgresql.ENUM.name` parameter for the PostgreSQL-specific
:class:`_postgresql.ENUM` datatype is now a required keyword argument. The
"name" is necessary in any case in order for the :class:`_postgresql.ENUM`
to be usable as an error would be raised at SQL/DDL render time if "name"
were not present.
.. change::
:tags: oracle, feature
:tickets: 8054
Add support for the new oracle driver ``oracledb``.
.. seealso::
:ref:`ticket_8054`
:ref:`oracledb`
.. change::
:tags: bug, engine
:tickets: 8567
For improved security, the :class:`_url.URL` object will now use password
obfuscation by default when ``str(url)`` is called. To stringify a URL with
cleartext password, the :meth:`_url.URL.render_as_string` may be used,
passing the :paramref:`_url.URL.render_as_string.hide_password` parameter
as ``False``. Thanks to our contributors for this pull request.
.. seealso::
:ref:`change_8567`
.. change::
:tags: change, orm
To better accommodate explicit typing, the names of some ORM constructs
that are typically constructed internally, but nonetheless are sometimes
visible in messaging as well as typing, have been changed to more succinct
names which also match the name of their constructing function (with
different casing), in all cases maintaining aliases to the old names for
the forseeable future:
* :class:`_orm.RelationshipProperty` becomes an alias for the primary name
:class:`_orm.Relationship`, which is constructed as always from the
:func:`_orm.relationship` function
* :class:`_orm.SynonymProperty` becomes an alias for the primary name
:class:`_orm.Synonym`, constructed as always from the
:func:`_orm.synonym` function
* :class:`_orm.CompositeProperty` becomes an alias for the primary name
:class:`_orm.Composite`, constructed as always from the
:func:`_orm.composite` function
.. change::
:tags: orm, change
:tickets: 8608
For consistency with the prominent ORM concept :class:`_orm.Mapped`, the
names of the dictionary-oriented collections,
:func:`_orm.attribute_mapped_collection`,
:func:`_orm.column_mapped_collection`, and :class:`_orm.MappedCollection`,
are changed to :func:`_orm.attribute_keyed_dict`,
:func:`_orm.column_keyed_dict` and :class:`_orm.KeyFuncDict`, using the
phrase "dict" to minimize any confusion against the term "mapped". The old
names will remain indefinitely with no schedule for removal.
.. change::
:tags: bug, sql
:tickets: 7354
Added ``if_exists`` and ``if_not_exists`` parameters for all "Create" /
"Drop" constructs including :class:`.CreateSequence`,
:class:`.DropSequence`, :class:`.CreateIndex`, :class:`.DropIndex`, etc.
allowing generic "IF EXISTS" / "IF NOT EXISTS" phrases to be rendered
within DDL. Pull request courtesy Jesse Bakker.
.. change::
:tags: engine, usecase
:tickets: 6342
Generalized the :paramref:`_sa.create_engine.isolation_level` parameter to
the base dialect so that it is no longer dependent on individual dialects
to be present. This parameter sets up the "isolation level" setting to
occur for all new database connections as soon as they are created by the
connection pool, where the value then stays set without being reset on
every checkin.
The :paramref:`_sa.create_engine.isolation_level` parameter is essentially
equivalent in functionality to using the
:paramref:`_engine.Engine.execution_options.isolation_level` parameter via
:meth:`_engine.Engine.execution_options` for an engine-wide setting. The
difference is in that the former setting assigns the isolation level just
once when a connection is created, the latter sets and resets the given
level on each connection checkout.
.. change::
:tags: bug, orm
:tickets: 8372
Changed the attribute access method used by
:func:`_orm.attribute_mapped_collection` and
:func:`_orm.column_mapped_collection` (now called
:func:`_orm.attribute_keyed_dict` and :func:`_orm.column_keyed_dict`) ,
used when populating the dictionary, to assert that the data value on
the object to be used as the dictionary key is actually present, and is
not instead using "None" due to the attribute never being actually
assigned. This is used to prevent a mis-population of None for a key
when assigning via a backref where the "key" attribute on the object is
not yet assigned.
As the failure mode here is a transitory condition that is not typically
persisted to the database, and is easy to produce via the constructor of
the class based on the order in which parameters are assigned, it is very
possible that many applications include this behavior already which is
silently passed over. To accommodate for applications where this error is
now raised, a new parameter
:paramref:`_orm.attribute_keyed_dict.ignore_unpopulated_attribute`
is also added to both :func:`_orm.attribute_keyed_dict` and
:func:`_orm.column_keyed_dict` that instead causes the erroneous
backref assignment to be skipped.
.. change::
:tags: usecase, postgresql
:tickets: 8491
The "ping" query emitted when configuring
:paramref:`_sa.create_engine.pool_pre_ping` for psycopg, asyncpg and
pg8000, but not for psycopg2, has been changed to be an empty query (``;``)
instead of ``SELECT 1``; additionally, for the asyncpg driver, the
unnecessary use of a prepared statement for this query has been fixed.
Rationale is to eliminate the need for PostgreSQL to produce a query plan
when the ping is emitted. The operation is not currently supported by the
``psycopg2`` driver which continues to use ``SELECT 1``.
.. change::
:tags: bug, oracle
:tickets: 7494
Adjustments made to the BLOB / CLOB / NCLOB datatypes in the cx_Oracle and
oracledb dialects, to improve performance based on recommendations from
Oracle developers.
.. change::
:tags: feature, orm
:tickets: 7433
The :class:`_orm.Session` (and by extension :class:`.AsyncSession`) now has
new state-tracking functionality that will proactively trap any unexpected
state changes which occur as a particular transactional method proceeds.
This is to allow situations where the :class:`_orm.Session` is being used
in a thread-unsafe manner, where event hooks or similar may be calling
unexpected methods within operations, as well as potentially under other
concurrency situations such as asyncio or gevent to raise an informative
message when the illegal access first occurs, rather than passing silently
leading to secondary failures due to the :class:`_orm.Session` being in an
invalid state.
.. seealso::
:ref:`change_7433`
.. change::
:tags: postgresql, dialect
:tickets: 6842
Added support for ``psycopg`` dialect supporting both sync and async
execution. This dialect is available under the ``postgresql+psycopg`` name
for both the :func:`_sa.create_engine` and
:func:`_asyncio.create_async_engine` engine-creation functions.
.. seealso::
:ref:`ticket_6842`
:ref:`postgresql_psycopg`
.. change::
:tags: usecase, sqlite
:tickets: 6195
Added RETURNING support for the SQLite dialect. SQLite supports RETURNING
since version 3.35.
.. change::
:tags: usecase, mariadb
:tickets: 7011
Added INSERT..RETURNING and DELETE..RETURNING support for the MariaDB
dialect. UPDATE..RETURNING is not yet supported by MariaDB. MariaDB
supports INSERT..RETURNING as of 10.5.0 and DELETE..RETURNING as of
10.0.5.
.. change::
:tags: feature, orm
The :func:`_orm.composite` mapping construct now supports automatic
resolution of values when used with a Python ``dataclass``; the
``__composite_values__()`` method no longer needs to be implemented as this
method is derived from inspection of the dataclass.
Additionally, classes mapped by :class:`_orm.composite` now support
ordering comparison operations, e.g. ``<``, ``>=``, etc.
See the new documentation at :ref:`mapper_composite` for examples.
.. change::
:tags: engine, bug
:tickets: 7161
The :meth:`_engine.Inspector.has_table` method will now consistently check
for views of the given name as well as tables. Previously this behavior was
dialect dependent, with PostgreSQL, MySQL/MariaDB and SQLite supporting it,
and Oracle and SQL Server not supporting it. Third party dialects should
also seek to ensure their :meth:`_engine.Inspector.has_table` method
searches for views as well as tables for the given name.
.. change::
:tags: feature, engine
:tickets: 5648
The :meth:`.DialectEvents.handle_error` event is now moved to the
:class:`.DialectEvents` suite from the :class:`.EngineEvents` suite, and
now participates in the connection pool "pre ping" event for those dialects
that make use of disconnect codes in order to detect if the database is
live. This allows end-user code to alter the state of "pre ping". Note that
this does not include dialects which contain a native "ping" method such as
that of psycopg2 or most MySQL dialects.
.. change::
:tags: feature, sql
:tickets: 7212
Added new backend-agnostic :class:`_types.Uuid` datatype generalized from
the PostgreSQL dialects to now be a core type, as well as migrated
:class:`_types.UUID` from the PostgreSQL dialect. The SQL Server
:class:`_mssql.UNIQUEIDENTIFIER` datatype also becomes a UUID-handling
datatype. Thanks to Trevor Gross for the help on this.
.. change::
:tags: feature, orm
:tickets: 8126
Added very experimental feature to the :func:`_orm.selectinload` and
:func:`_orm.immediateload` loader options called
:paramref:`_orm.selectinload.recursion_depth` /
:paramref:`_orm.immediateload.recursion_depth` , which allows a single
loader option to automatically recurse into self-referential relationships.
Is set to an integer indicating depth, and may also be set to -1 to
indicate to continue loading until no more levels deep are found.
Major internal changes to :func:`_orm.selectinload` and
:func:`_orm.immediateload` allow this feature to work while continuing
to make correct use of the compilation cache, as well as not using
arbitrary recursion, so any level of depth is supported (though would
emit that many queries). This may be useful for
self-referential structures that must be loaded fully eagerly, such as when
using asyncio.
A warning is also emitted when loader options are connected together with
arbitrary lengths (that is, without using the new ``recursion_depth``
option) when excessive recursion depth is detected in related object
loading. This operation continues to use huge amounts of memory and
performs extremely poorly; the cache is disabled when this condition is
detected to protect the cache from being flooded with arbitrary statements.
.. change::
:tags: bug, orm
:tickets: 8403
Added new parameter :paramref:`.AbstractConcreteBase.strict_attrs` to the
:class:`.AbstractConcreteBase` declarative mixin class. The effect of this
parameter is that the scope of attributes on subclasses is correctly
limited to the subclass in which each attribute is declared, rather than
the previous behavior where all attributes of the entire hierarchy are
applied to the base "abstract" class. This produces a cleaner, more correct
mapping where subclasses no longer have non-useful attributes on them which
are only relevant to sibling classes. The default for this parameter is
False, which leaves the previous behavior unchanged; this is to support
existing code that makes explicit use of these attributes in queries.
To migrate to the newer approach, apply explicit attributes to the abstract
base class as needed.
.. change::
:tags: usecase, mysql, mariadb
:tickets: 8503
The ``ROLLUP`` function will now correctly render ``WITH ROLLUP`` on
MySql and MariaDB, allowing the use of group by rollup with these
backend.
.. change::
:tags: feature, orm
:tickets: 6928
Added new parameter :paramref:`_orm.Session.autobegin`, which when set to
``False`` will prevent the :class:`_orm.Session` from beginning a
transaction implicitly. The :meth:`_orm.Session.begin` method must be
called explicitly first in order to proceed with operations, otherwise an
error is raised whenever any operation would otherwise have begun
automatically. This option can be used to create a "safe"
:class:`_orm.Session` that won't implicitly start new transactions.
As part of this change, also added a new status variable
:class:`_orm.SessionTransaction.origin` which may be useful for event
handling code to be aware of the origin of a particular
:class:`_orm.SessionTransaction`.
.. change::
:tags: feature, platform
:tickets: 7256
The SQLAlchemy C extensions have been replaced with all new implementations
written in Cython. Like the C extensions before, pre-built wheel files
for a wide range of platforms are available on pypi so that building
is not an issue for common platforms. For custom builds, ``python setup.py build_ext``
works as before, needing only the additional Cython install. ``pyproject.toml``
is also part of the source now which will establish the proper build dependencies
when using pip.
.. seealso::
:ref:`change_7256`
.. change::
:tags: change, platform
:tickets: 7311
SQLAlchemy's source build and installation now includes a ``pyproject.toml`` file
for full :pep:`517` support.
.. seealso::
:ref:`change_7311`
.. change::
:tags: feature, schema
:tickets: 7631
Expanded on the "conditional DDL" system implemented by the
:class:`_schema.ExecutableDDLElement` class (renamed from
:class:`_schema.DDLElement`) to be directly available on
:class:`_schema.SchemaItem` constructs such as :class:`_schema.Index`,
:class:`_schema.ForeignKeyConstraint`, etc. such that the conditional logic
for generating these elements is included within the default DDL emitting
process. This system can also be accommodated by a future release of
Alembic to support conditional DDL elements within all schema-management
systems.
.. seealso::
:ref:`ticket_7631`
.. change::
:tags: change, oracle
:tickets:`4379`
Materialized views on oracle are now reflected as views.
On previous versions of SQLAlchemy the views were returned among
the table names, not among the view names. As a side effect of
this change they are not reflected by default by
:meth:`_sql.MetaData.reflect`, unless ``views=True`` is set.
To get a list of materialized views, use the new
inspection method :meth:`.Inspector.get_materialized_view_names`.
.. change::
:tags: bug, sqlite
:tickets: 7299
Removed the warning that emits from the :class:`_types.Numeric` type about
DBAPIs not supporting Decimal values natively. This warning was oriented
towards SQLite, which does not have any real way without additional
extensions or workarounds of handling precision numeric values more than 15
significant digits as it only uses floating point math to represent
numbers. As this is a known and documented limitation in SQLite itself, and
not a quirk of the pysqlite driver, there's no need for SQLAlchemy to warn
for this. The change does not otherwise modify how precision numerics are
handled. Values can continue to be handled as ``Decimal()`` or ``float()``
as configured with the :class:`_types.Numeric`, :class:`_types.Float` , and
related datatypes, just without the ability to maintain precision beyond 15
significant digits when using SQLite, unless alternate representations such
as strings are used.
.. change::
:tags: mssql, bug
:tickets: 8177
The ``use_setinputsizes`` parameter for the ``mssql+pyodbc`` dialect now
defaults to ``True``; this is so that non-unicode string comparisons are
bound by pyodbc to pyodbc.SQL_VARCHAR rather than pyodbc.SQL_WVARCHAR,
allowing indexes against VARCHAR columns to take effect. In order for the
``fast_executemany=True`` parameter to continue functioning, the
``use_setinputsizes`` mode now skips the ``cursor.setinputsizes()`` call
specifically when ``fast_executemany`` is True and the specific method in
use is ``cursor.executemany()``, which doesn't support setinputsizes. The
change also adds appropriate pyodbc DBAPI typing to values that are typed
as :class:`_types.Unicode` or :class:`_types.UnicodeText`, as well as
altered the base :class:`_types.JSON` datatype to consider JSON string
values as :class:`_types.Unicode` rather than :class:`_types.String`.
.. change::
:tags: bug, sqlite, performance
:tickets: 7490
The SQLite dialect now defaults to :class:`_pool.QueuePool` when a file
based database is used. This is set along with setting the
``check_same_thread`` parameter to ``False``. It has been observed that the
previous approach of defaulting to :class:`_pool.NullPool`, which does not
hold onto database connections after they are released, did in fact have a
measurable negative performance impact. As always, the pool class is
customizable via the :paramref:`_sa.create_engine.poolclass` parameter.
.. seealso::
:ref:`change_7490`
.. change::
:tags: usecase, schema
:tickets: 8141
Added parameter :paramref:`_ddl.DropConstraint.if_exists` to the
:class:`_ddl.DropConstraint` construct which result in "IF EXISTS" DDL
being added to the DROP statement.
This phrase is not accepted by all databases and the operation will fail
on a database that does not support it as there is no similarly compatible
fallback within the scope of a single DDL statement.
Pull request courtesy Mike Fiedler.
.. change::
:tags: change, postgresql
In support of new PostgreSQL features including the psycopg3 dialect as
well as extended "fast insertmany" support, the system by which typing
information for bound parameters is passed to the PostgreSQL database has
been redesigned to use inline casts emitted by the SQL compiler, and is now
applied to all PostgreSQL dialects. This is in contrast to the previous
approach which would rely upon the DBAPI in use to render these casts
itself, which in cases such as that of pg8000 and the adapted asyncpg
driver, would use the pep-249 ``setinputsizes()`` method, or with the
psycopg2 driver would rely on the driver itself in most cases, with some
special exceptions made for ARRAY.
The new approach now has all PostgreSQL dialects rendering these casts as
needed using PostgreSQL double-colon style within the compiler, and the use
of ``setinputsizes()`` is removed for PostgreSQL dialects, as this was not
generally part of these DBAPIs in any case (pg8000 being the only
exception, which added the method at the request of SQLAlchemy developers).
Advantages to this approach include per-statement performance, as no second
pass over the compiled statement is required at execution time, better
support for all DBAPIs, as there is now one consistent system of applying
typing information, and improved transparency, as the SQL logging output,
as well as the string output of a compiled statement, will show these casts
present in the statement directly, whereas previously these casts were not
visible in logging output as they would occur after the statement were
logged.
.. change::
:tags: engine, removed
Removed the previously deprecated ``case_sensitive`` parameter from
:func:`_sa.create_engine`, which would impact only the lookup of string
column names in Core-only result set rows; it had no effect on the behavior
of the ORM. The effective behavior of what ``case_sensitive`` refers
towards remains at its default value of ``True``, meaning that string names
looked up in ``row._mapping`` will match case-sensitively, just like any
other Python mapping.
Note that the ``case_sensitive`` parameter was not in any way related to
the general subject of case sensitivity control, quoting, and "name
normalization" (i.e. converting for databases that consider all uppercase
words to be case insensitive) for DDL identifier names, which remains a
normal core feature of SQLAlchemy.
.. change::
:tags: bug, sql
:tickets: 7744
Improved the construction of SQL binary expressions to allow for very long
expressions against the same associative operator without special steps
needed in order to avoid high memory use and excess recursion depth. A
particular binary operation ``A op B`` can now be joined against another
element ``op C`` and the resulting structure will be "flattened" so that
the representation as well as SQL compilation does not require recursion.
One effect of this change is that string concatenation expressions which
use SQL functions come out as "flat", e.g. MySQL will now render
``concat('x', 'y', 'z', ...)``` rather than nesting together two-element
functions like ``concat(concat('x', 'y'), 'z')``. Third-party dialects
which override the string concatenation operator will need to implement
a new method ``def visit_concat_op_expression_clauselist()`` to
accompany the existing ``def visit_concat_op_binary()`` method.
.. change::
:tags: feature, sql
:tickets: 5465
Added :class:`.Double`, :class:`.DOUBLE`, :class:`.DOUBLE_PRECISION`
datatypes to the base ``sqlalchemy.`` module namespace, for explicit use of
double/double precision as well as generic "double" datatypes. Use
:class:`.Double` for generic support that will resolve to DOUBLE/DOUBLE
PRECISION/FLOAT as needed for different backends.
.. change::
:tags: feature, oracle
:tickets: 5465
Implemented DDL and reflection support for ``FLOAT`` datatypes which
include an explicit "binary_precision" value. Using the Oracle-specific
:class:`_oracle.FLOAT` datatype, the new parameter
:paramref:`_oracle.FLOAT.binary_precision` may be specified which will
render Oracle's precision for floating point types directly. This value is
interpreted during reflection. Upon reflecting back a ``FLOAT`` datatype,
the datatype returned is one of :class:`_types.DOUBLE_PRECISION` for a
``FLOAT`` for a precision of 126 (this is also Oracle's default precision
for ``FLOAT``), :class:`_types.REAL` for a precision of 63, and
:class:`_oracle.FLOAT` for a custom precision, as per Oracle documentation.
As part of this change, the generic :paramref:`_sqltypes.Float.precision`
value is explicitly rejected when generating DDL for Oracle, as this
precision cannot be accurately converted to "binary precision"; instead, an
error message encourages the use of
:meth:`_sqltypes.TypeEngine.with_variant` so that Oracle's specific form of
precision may be chosen exactly. This is a backwards-incompatible change in
behavior, as the previous "precision" value was silently ignored for
Oracle.
.. seealso::
:ref:`change_5465_oracle`
.. change::
:tags: postgresql, psycopg2
:tickets: 7238
Update psycopg2 dialect to use the DBAPI interface to execute
two phase transactions. Previously SQL commands were execute
to handle this kind of transactions.
.. change::
:tags: deprecations, engine
:tickets: 6962
The :paramref:`_sa.create_engine.implicit_returning` parameter is
deprecated on the :func:`_sa.create_engine` function only; the parameter
remains available on the :class:`_schema.Table` object. This parameter was
originally intended to enable the "implicit returning" feature of
SQLAlchemy when it was first developed and was not enabled by default.
Under modern use, there's no reason this parameter should be disabled, and
it has been observed to cause confusion as it degrades performance and
makes it more difficult for the ORM to retrieve recently inserted server
defaults. The parameter remains available on :class:`_schema.Table` to
specifically suit database-level edge cases which make RETURNING
infeasible, the sole example currently being SQL Server's limitation that
INSERT RETURNING may not be used on a table that has INSERT triggers on it.
.. change::
:tags: bug, oracle
:tickets: 6962
Related to the deprecation for
:paramref:`_sa.create_engine.implicit_returning`, the "implicit_returning"
feature is now enabled for the Oracle dialect in all cases; previously, the
feature would be turned off when an Oracle 8/8i version were detected,
however online documentation indicates both versions support the same
RETURNING syntax as modern versions.
.. change::
:tags: bug, schema
:tickets: 8102
The warnings that are emitted regarding reflection of indexes or unique
constraints, when the :paramref:`.Table.include_columns` parameter is used
to exclude columns that are then found to be part of those constraints,
have been removed. When the :paramref:`.Table.include_columns` parameter is
used it should be expected that the resulting :class:`.Table` construct
will not include constraints that rely upon omitted columns. This change
was made in response to :ticket:`8100` which repaired
:paramref:`.Table.include_columns` in conjunction with foreign key
constraints that rely upon omitted columns, where the use case became
clear that omitting such constraints should be expected.
.. change::
:tags: bug, postgresql
:tickets: 7086
The :meth:`.Operators.match` operator now uses ``plainto_tsquery()`` for
PostgreSQL full text search, rather than ``to_tsquery()``. The rationale
for this change is to provide better cross-compatibility with match on
other database backends. Full support for all PostgreSQL full text
functions remains available through the use of :data:`.func` in
conjunction with :meth:`.Operators.bool_op` (an improved version of
:meth:`.Operators.op` for boolean operators).
.. seealso::
:ref:`change_7086`
.. change::
:tags: usecase, sql
:tickets: 5052
Added modified ISO-8601 rendering (i.e. ISO-8601 with the T converted to a
space) when using ``literal_binds`` with the SQL compilers provided by the
PostgreSQL, MySQL, MariaDB, MSSQL, Oracle dialects. For Oracle, the ISO
format is wrapped inside of an appropriate TO_DATE() function call.
Previously this rendering was not implemented for dialect-specific
compilation.
.. seealso::
:ref:`change_5052`
.. change::
:tags: removed, engine
:tickets: 7258
Removed legacy and deprecated package ``sqlalchemy.databases``.
Please use ``sqlalchemy.dialects`` instead.
.. change::
:tags: usecase, schema
:tickets: 8394
Implemented the DDL event hooks :meth:`.DDLEvents.before_create`,
:meth:`.DDLEvents.after_create`, :meth:`.DDLEvents.before_drop`,
:meth:`.DDLEvents.after_drop` for all :class:`.SchemaItem` objects that
include a distinct CREATE or DROP step, when that step is invoked as a
distinct SQL statement, including for :class:`.ForeignKeyConstraint`,
:class:`.Sequence`, :class:`.Index`, and PostgreSQL's
:class:`_postgresql.ENUM`.
.. change::
:tags: engine, feature
The :meth:`.ConnectionEvents.set_connection_execution_options`
and :meth:`.ConnectionEvents.set_engine_execution_options`
event hooks now allow the given options dictionary to be modified
in-place, where the new contents will be received as the ultimate
execution options to be acted upon. Previously, in-place modifications to
the dictionary were not supported.
.. change::
:tags: bug, sql
:tickets: 4926
Implemented full support for "truediv" and "floordiv" using the
"/" and "//" operators. A "truediv" operation between two expressions
using :class:`_types.Integer` now considers the result to be
:class:`_types.Numeric`, and the dialect-level compilation will cast
the right operand to a numeric type on a dialect-specific basis to ensure
truediv is achieved. For floordiv, conversion is also added for those
databases that don't already do floordiv by default (MySQL, Oracle) and
the ``FLOOR()`` function is rendered in this case, as well as for
cases where the right operand is not an integer (needed for PostgreSQL,
others).
The change resolves issues both with inconsistent behavior of the
division operator on different backends and also fixes an issue where
integer division on Oracle would fail to be able to fetch a result due
to inappropriate outputtypehandlers.
.. seealso::
:ref:`change_4926`
.. change::
:tags: postgresql, schema
:tickets: 8216
Introduced the type :class:`_postgresql.JSONPATH` that can be used
in cast expressions. This is required by some PostgreSQL dialects
when using functions such as ``jsonb_path_exists`` or
``jsonb_path_match`` that accept a ``jsonpath`` as input.
.. seealso::
:ref:`postgresql_json_types` - PostgreSQL JSON types.
.. change::
:tags: schema, mysql, mariadb
:tickets: 4038
Add support for Partitioning and Sample pages on MySQL and MariaDB
reflected options.
The options are stored in the table dialect options dictionary, so
the following keyword need to be prefixed with ``mysql_`` or ``mariadb_``
depending on the backend.
Supported options are:
* ``stats_sample_pages``
* ``partition_by``
* ``partitions``
* ``subpartition_by``
These options are also reflected when loading a table from database,
and will populate the table :attr:`_schema.Table.dialect_options`.
Pull request courtesy of Ramon Will.
.. change::
:tags: usecase, mssql
:tickets: 8288
Implemented reflection of the "clustered index" flag ``mssql_clustered``
for the SQL Server dialect. Pull request courtesy John Lennox.
.. change::
:tags: reflection, postgresql
:tickets: 7442
The PostgreSQL dialect now supports reflection of expression based indexes.
The reflection is supported both when using
:meth:`_engine.Inspector.get_indexes` and when reflecting a
:class:`_schema.Table` using :paramref:`_schema.Table.autoload_with`.
Thanks to immerrr and Aidan Kane for the help on this ticket.
.. change::
:tags: firebird, removed
:tickets: 7258
Removed the "firebird" internal dialect that was deprecated in previous
SQLAlchemy versions. Third party dialect support is available.
.. seealso::
:ref:`external_toplevel`
.. change::
:tags: bug, orm
:tickets: 7495
The behavior of :func:`_orm.defer` regarding primary key and "polymorphic
discriminator" columns is revised such that these columns are no longer
deferrable, either explicitly or when using a wildcard such as
``defer('*')``. Previously, a wildcard deferral would not load
PK/polymorphic columns which led to errors in all cases, as the ORM relies
upon these columns to produce object identities. The behavior of explicit
deferral of primary key columns is unchanged as these deferrals already
were implicitly ignored.
.. change::
:tags: bug, sql
:tickets: 7471
Added an additional lookup step to the compiler which will track all FROM
clauses which are tables, that may have the same name shared in multiple
schemas where one of the schemas is the implicit "default" schema; in this
case, the table name when referring to that name without a schema
qualification will be rendered with an anonymous alias name at the compiler
level in order to disambiguate the two (or more) names. The approach of
schema-qualifying the normally unqualified name with the server-detected
"default schema name" value was also considered, however this approach
doesn't apply to Oracle nor is it accepted by SQL Server, nor would it work
with multiple entries in the PostgreSQL search path. The name collision
issue resolved here has been identified as affecting at least Oracle,
PostgreSQL, SQL Server, MySQL and MariaDB.
.. change::
:tags: improvement, typing
:tickets: 6980
The :meth:`_sqltypes.TypeEngine.with_variant` method now returns a copy of
the original :class:`_sqltypes.TypeEngine` object, rather than wrapping it
inside the ``Variant`` class, which is effectively removed (the import
symbol remains for backwards compatibility with code that may be testing
for this symbol). While the previous approach maintained in-Python
behaviors, maintaining the original type allows for clearer type checking
and debugging.
:meth:`_sqltypes.TypeEngine.with_variant` also accepts multiple dialect
names per call as well, in particular this is helpful for related
backend names such as ``"mysql", "mariadb"``.
.. seealso::
:ref:`change_6980`
.. change::
:tags: usecase, sqlite, performance
:tickets: 7029
SQLite datetime, date, and time datatypes now use Python standard lib
``fromisoformat()`` methods in order to parse incoming datetime, date, and
time string values. This improves performance vs. the previous regular
expression-based approach, and also automatically accommodates for datetime
and time formats that contain either a six-digit "microseconds" format or a
three-digit "milliseconds" format.
.. change::
:tags: usecase, mssql
:tickets: 7844
Added support table and column comments on MSSQL when
creating a table. Added support for reflecting table comments.
Thanks to Daniel Hall for the help in this pull request.
.. change::
:tags: mssql, removed
:tickets: 7258
Removed support for the mxodbc driver due to lack of testing support. ODBC
users may use the pyodbc dialect which is fully supported.
.. change::
:tags: mysql, removed
:tickets: 7258
Removed support for the OurSQL driver for MySQL and MariaDB, as this
driver does not seem to be maintained.
.. change::
:tags: postgresql, removed
:tickets: 7258
Removed support for multiple deprecated drivers:
- pypostgresql for PostgreSQL. This is available as an
external driver at https://github.com/PyGreSQL
- pygresql for PostgreSQL.
Please switch to one of the supported drivers or to the external
version of the same driver.
.. change::
:tags: bug, engine
:tickets: 7953
Fixed issue in :meth:`.Result.columns` method where calling upon
:meth:`.Result.columns` with a single index could in some cases,
particularly ORM result object cases, cause the :class:`.Result` to yield
scalar objects rather than :class:`.Row` objects, as though the
:meth:`.Result.scalars` method had been called. In SQLAlchemy 1.4, this
scenario emits a warning that the behavior will change in SQLAlchemy 2.0.
.. change::
:tags: usecase, sql
:tickets: 7759
Added new parameter :paramref:`.HasCTE.add_cte.nest_here` to
:meth:`.HasCTE.add_cte` which will "nest" a given :class:`.CTE` at the
level of the parent statement. This parameter is equivalent to using the
:paramref:`.HasCTE.cte.nesting` parameter, but may be more intuitive in
some scenarios as it allows the nesting attribute to be set simultaneously
along with the explicit level of the CTE.
The :meth:`.HasCTE.add_cte` method also accepts multiple CTE objects.
.. change::
:tags: bug, orm
:tickets: 7438
Fixed bug in the behavior of the :paramref:`_orm.Mapper.eager_defaults`
parameter such that client-side SQL default or onupdate expressions in the
table definition alone will trigger a fetch operation using RETURNING or
SELECT when the ORM emits an INSERT or UPDATE for the row. Previously, only
server side defaults established as part of table DDL and/or server-side
onupdate expressions would trigger this fetch, even though client-side SQL
expressions would be included when the fetch was rendered.
.. change::
:tags: performance, schema
:tickets: 4379
Rearchitected the schema reflection API to allow participating dialects to
make use of high performing batch queries to reflect the schemas of many
tables at once using fewer queries by an order of magnitude. The
new performance features are targeted first at the PostgreSQL and Oracle
backends, and may be applied to any dialect that makes use of SELECT
queries against system catalog tables to reflect tables. The change also
includes new API features and behavioral improvements to the
:class:`.Inspector` object, including consistent, cached behavior of
methods like :meth:`.Inspector.has_table`,
:meth:`.Inspector.get_table_names` and new methods
:meth:`.Inspector.has_schema` and :meth:`.Inspector.has_index`.
.. seealso::
:ref:`change_4379` - full background
.. change::
:tags: bug, engine
Passing a :class:`.DefaultGenerator` object such as a :class:`.Sequence` to
the :meth:`.Connection.execute` method is deprecated, as this method is
typed as returning a :class:`.CursorResult` object, and not a plain scalar
value. The :meth:`.Connection.scalar` method should be used instead, which
has been reworked with new internal codepaths to suit invoking a SELECT for
default generation objects without going through the
:meth:`.Connection.execute` method.
.. change::
:tags: usecase, sqlite
:tickets: 7185
The SQLite dialect now supports UPDATE..FROM syntax, for UPDATE statements
that may refer to additional tables within the WHERE criteria of the
statement without the need to use subqueries. This syntax is invoked
automatically when using the :class:`_dml.Update` construct when more than
one table or other entity or selectable is used.
.. change::
:tags: general, changed
The :meth:`_orm.Query.instances` method is deprecated. The behavioral
contract of this method, which is that it can iterate objects through
arbitrary result sets, is long obsolete and no longer tested.
Arbitrary statements can return objects by using constructs such
as :meth`.Select.from_statement` or :func:`_orm.aliased`.
.. change::
:tags: feature, orm
Declarative mixins which use :class:`_schema.Column` objects that contain
:class:`_schema.ForeignKey` references no longer need to use
:func:`_orm.declared_attr` to achieve this mapping; the
:class:`_schema.ForeignKey` object is copied along with the
:class:`_schema.Column` itself when the column is applied to the declared
mapping.
.. change::
:tags: oracle, feature
:tickets: 6245
Full "RETURNING" support is implemented for the cx_Oracle dialect, covering
two individual types of functionality:
* multi-row RETURNING is implemented, meaning multiple RETURNING rows are
now received for DML statements that produce more than one row for
RETURNING.
* "executemany RETURNING" is also implemented - this allows RETURNING to
yield row-per statement when ``cursor.executemany()`` is used.
The implementation of this part of the feature delivers dramatic
performance improvements to ORM inserts, in the same way as was
added for psycopg2 in the SQLAlchemy 1.4 change :ref:`change_5263`.
.. change::
:tags: oracle
cx_Oracle 7 is now the minimum version for cx_Oracle.
.. change::
:tags: bug, sql
:tickets: 7551
Python string values for which a SQL type is determined from the type of
the value, mainly when using :func:`_sql.literal`, will now apply the
:class:`_types.String` type, rather than the :class:`_types.Unicode`
datatype, for Python string values that test as "ascii only" using Python
``str.isascii()``. If the string is not ``isascii()``, the
:class:`_types.Unicode` datatype will be bound instead, which was used in
all string detection previously. This behavior **only applies to in-place
detection of datatypes when using ``literal()`` or other contexts that have
no existing datatype**, which is not usually the case under normal
:class:`_schema.Column` comparison operations, where the type of the
:class:`_schema.Column` being compared always takes precedence.
Use of the :class:`_types.Unicode` datatype can determine literal string
formatting on backends such as SQL Server, where a literal value (i.e.
using ``literal_binds``) will be rendered as ``N'<value>'`` instead of
``'value'``. For normal bound value handling, the :class:`_types.Unicode`
datatype also may have implications for passing values to the DBAPI, again
in the case of SQL Server, the pyodbc driver supports the use of
:ref:`setinputsizes mode <mssql_pyodbc_setinputsizes>` which will handle
:class:`_types.String` versus :class:`_types.Unicode` differently.
.. change::
:tags: bug, sql
:tickets: 7083
The :class:`_functions.array_agg` will now set the array dimensions to 1.
Improved :class:`_types.ARRAY` processing to accept ``None`` values as
value of a multi-array.