1.0 Changelog — SQLAlchemy 2.0 Documentation

Release: 2.0.51 | Release Date: June 15, 2026

# SQLAlchemy 2.0 Documentation

# 1.0 Changelog

## 1.0.19

Released: August 3, 2017

### oracle

- [oracle] [performance] [bug] [py2k]

  Fixed performance regression caused by the fix for #3937 where cx_Oracle as of version 5.3 dropped the `.UNICODE` symbol from its namespace, which was interpreted as cx_Oracle’s “WITH_UNICODE” mode being turned on unconditionally, which invokes functions on the SQLAlchemy side which convert all strings to unicode unconditionally and causing a performance impact. In fact, per cx_Oracle’s author the “WITH_UNICODE” mode has been removed entirely as of 5.1, so the expensive unicode conversion functions are no longer necessary and are disabled if cx_Oracle 5.1 or greater is detected under Python 2. The warning against “WITH_UNICODE” mode that was removed under #3937 is also restored.

  References: #4035

## 1.0.18

Released: July 24, 2017

### oracle

- [oracle] [bug]

  A fix to cx_Oracle’s WITH_UNICODE mode which was uncovered by the fact that cx_Oracle 5.3 now seems to hardcode this flag on in the build; an internal method that uses this mode wasn’t using the correct signature.

  References: #3937

### tests

- [tests] [bug] [py3k]

  Fixed issue in testing fixtures which was incompatible with a change made as of Python 3.6.2 involving context managers.

  References: #4034

## 1.0.17

Released: January 17, 2017

### orm

- [orm] [bug]

  Fixed bug involving joined eager loading against multiple entities when polymorphic inheritance is also in use which would throw “‘NoneType’ object has no attribute ‘isa’”. The issue was introduced by the fix for #3611.

  References: #3884

### misc

- [bug] [py3k]

  Fixed Python 3.6 DeprecationWarnings related to escaped strings without the ‘r’ modifier, and added test coverage for Python 3.6.

  References: #3886

## 1.0.16

Released: November 15, 2016

### orm

- [orm] [bug]

  Fixed bug in `Session.bulk_update_mappings()` where an alternate-named primary key attribute would not track properly into the UPDATE statement.

  References: #3849

- [orm] [bug]

  Fixed bug where joined eager loading would fail for a polymorphically- loaded mapper, where the polymorphic_on was set to an un-mapped expression such as a CASE expression.

  References: #3800

- [orm] [bug]

  Fixed bug where the ArgumentError raised for an invalid bind sent to a Session via `Session.bind_mapper()`, `Session.bind_table()`, or the constructor would fail to be correctly raised.

  References: #3798

- [orm] [bug]

  Fixed bug in `Session.bulk_save()` where an UPDATE would not function correctly in conjunction with a mapping that implements a version id counter.

  References: #3781

- [orm] [bug]

  Fixed bug where the `Mapper.attrs`, `Mapper.all_orm_descriptors` and other derived attributes would fail to refresh when mapper properties or other ORM constructs were added to the mapper/class after these accessors were first called.

  References: #3778

### mssql

- [mssql] [bug]

  Changed the query used to get “default schema name”, from one that queries the database principals table to using the “schema_name()” function, as issues have been reported that the former system was unavailable on the Azure Data Warehouse edition. It is hoped that this will finally work across all SQL Server versions and authentication styles.

  References: #3810

- [mssql] [bug]

  Updated the server version info scheme for pyodbc to use SQL Server SERVERPROPERTY(), rather than relying upon pyodbc.SQL_DBMS_VER, which continues to be unreliable particularly with FreeTDS.

  References: #3814

- [mssql] [bug]

  Added error code 20017 “unexpected EOF from the server” to the list of disconnect exceptions that result in a connection pool reset. Pull request courtesy Ken Robbins.

  References: #3791

- [mssql] [bug]

  Fixed bug in pyodbc dialect (as well as in the mostly non-working adodbapi dialect) whereby a semicolon present in the password or username fields could be interpreted as a separator for another token; the values are now quoted when semicolons are present.

  References: #3762

### misc

- [bug] [orm.declarative]

  Fixed bug where setting up a single-table inh subclass of a joined-table subclass which included an extra column would corrupt the foreign keys collection of the mapped table, thereby interfering with the initialization of relationships.

  References: #3797

## 1.0.15

Released: September 1, 2016

### orm

- [orm] [bug]

  Fixed bug in subquery eager loading where a subqueryload of an “of_type()” object linked to a second subqueryload of a plain mapped class, or a longer chain of several “of_type()” attributes, would fail to link the joins correctly.

  References: #3773, #3774

### sql

- [sql] [bug]

  Fixed bug in `Table` where the internal method `_reset_exported()` would corrupt the state of the object. This method is intended for selectable objects and is called by the ORM in some cases; an erroneous mapper configuration would could lead the ORM to call this on a `Table` object.

  References: #3755

### mysql

- [mysql] [bug]

  Added support for parsing MySQL/Connector boolean and integer arguments within the URL query string: connection_timeout, connect_timeout, pool_size, get_warnings, raise_on_warnings, raw, consume_results, ssl_verify_cert, force_ipv6, pool_reset_session, compress, allow_local_infile, use_pure.

  References: #3787

### misc

- [bug] [ext]

  Fixed bug in `sqlalchemy.ext.baked` where the unbaking of a subquery eager loader query would fail due to a variable scoping issue, when multiple subquery loaders were involved. Pull request courtesy Mark Hahnenberg.

  References: #3743

## 1.0.14

Released: July 6, 2016

### examples

- [examples] [bug]

  Fixed a regression that occurred in the examples/vertical/dictlike-polymorphic.py example which prevented it from running.

  References: #3704

### engine

- [engine] [bug] [postgresql]

  Fixed bug in cross-schema foreign key reflection in conjunction with the `MetaData.schema` argument, where a referenced table that is present in the “default” schema would fail since there would be no way to indicate a `Table` that has “blank” for a schema. The special symbol `sqlalchemy.schema.BLANK_SCHEMA` has been added as an available value for `Table.schema` and `Sequence.schema`, indicating that the schema name should be forced to be `None` even if `MetaData.schema` is specified.

  References: #3716

### sql

- [sql] [bug]

  Fixed issue in SQL math negation operator where the type of the expression would no longer be the numeric type of the original. This would cause issues where the type determined result set behaviors.

  References: #3735

- [sql] [bug]

  Fixed bug whereby the `__getstate__` / `__setstate__` methods for sqlalchemy.util.Properties were non-working due to the transition in the 1.0 series to `__slots__`. The issue potentially impacted some third-party applications. Pull request courtesy Pieter Mulder.

  References: #3728

- [sql] [bug]

  `FromClause.count()` is pending deprecation for 1.1. This function makes use of an arbitrary column in the table and is not reliable; for Core use, `func.count()` should be preferred.

  References: #3724

- [sql] [bug]

  Fixed bug in `CTE` structure which would cause it to not clone properly when a union was used, as is common in a recursive CTE. The improper cloning would cause errors when the CTE is used in various ORM contexts such as that of a `column_property()`.

  References: #3722

- [sql] [bug]

  Fixed bug whereby `Table.tometadata()` would make a duplicate `UniqueConstraint` for each `Column` object that featured the `unique=True` parameter.

  References: #3721

### postgresql

- [postgresql] [bug]

  Fixed bug whereby `TypeDecorator` and `Variant` types were not deeply inspected enough by the PostgreSQL dialect to determine if SMALLSERIAL or BIGSERIAL needed to be rendered rather than SERIAL.

  References: #3739

### oracle

- [oracle] [bug]

  Fixed bug in `Select.with_for_update.of`, where the Oracle “rownum” approach to LIMIT/OFFSET would fail to accommodate for the expressions inside the “OF” clause, which must be stated at the topmost level referring to expression within the subquery. The expressions are now added to the subquery if needed.

  References: #3741

## 1.0.13

Released: May 16, 2016

### orm

- [orm] [bug]

  Fixed bug in “evaluate” strategy of `Query.update()` and `Query.delete()` which would fail to accommodate a bound parameter with a “callable” value, as which occurs when filtering by a many-to-one equality expression along a relationship.

  References: #3700

- [orm] [bug]

  Fixed bug whereby the event listeners used for backrefs could be inadvertently applied multiple times, when using a deep class inheritance hierarchy in conjunction with multiple mapper configuration steps.

  References: #3710

- [orm] [bug]

  Fixed bug whereby passing a `text()` construct to the `Query.group_by()` method would raise an error, instead of interpreting the object as a SQL fragment.

  References: #3706

- [orm] [bug]

  Anonymous labeling is applied to a `func` construct that is passed to `column_property()`, so that if the same attribute is referred to as a column expression twice the names are de-duped, thus avoiding “ambiguous column” errors. Previously, the `.label(None)` would need to be applied in order for the name to be de-anonymized.

  References: #3663

- [orm] [bug]

  Fixed regression appearing in the 1.0 series in ORM loading where the exception raised for an expected column missing would incorrectly be a `NoneType` error, rather than the expected `NoSuchColumnError`.

  References: #3658

### examples

- [examples] [bug]

  Changed the “directed graph” example to no longer consider integer identifiers of nodes as significant; the “higher” / “lower” references now allow mutual edges in both directions.

  References: #3698

### sql

- [sql] [bug]

  Fixed bug where when using `case_sensitive=False` with an `Engine`, the result set would fail to correctly accommodate for duplicate column names in the result set, causing an error when the statement is executed in 1.0, and preventing the “ambiguous column” exception from functioning in 1.1.

  References: #3690

- [sql] [bug]

  Fixed bug where the negation of an EXISTS expression would not be properly typed as boolean in the result, and also would fail to be anonymously aliased in a SELECT list as is the case with a non-negated EXISTS construct.

  References: #3682

- [sql] [bug]

  Fixed bug where “unconsumed column names” exception would fail to be raised in the case where `Insert.values()` were called with a list of parameter mappings, instead of a single mapping of parameters. Pull request courtesy Athena Yao.

  References: #3666

### postgresql

- [postgresql] [bug]

  Added disconnect detection support for the error string “SSL error: decryption failed or bad record mac”. Pull request courtesy Iuri de Silvio.

  References: #3715

### mssql

- [mssql] [bug]

  Fixed bug where by ROW_NUMBER OVER clause applied for OFFSET selects in SQL Server would inappropriately substitute a plain column from the local statement that overlaps with a label name used by the ORDER BY criteria of the statement.

  References: #3711

- [mssql] [bug] [oracle]

  Fixed regression appearing in the 1.0 series which would cause the Oracle and SQL Server dialects to incorrectly account for result set columns when these dialects would wrap a SELECT in a subquery in order to provide LIMIT/OFFSET behavior, and the original SELECT statement referred to the same column multiple times, such as a column and a label of that same column. This issue is related to #3658 in that when the error occurred, it would also cause a `NoneType` error, rather than reporting that it couldn’t locate a column.

  References: #3657

### oracle

- [oracle] [bug]

  Fixed a bug in the cx_Oracle connect process that caused a TypeError when the either the user, password or dsn was empty. This prevented external authentication to Oracle databases, and prevented connecting to the default dsn. The connect string oracle:// now logs into the default dsn using the Operating System username, equivalent to connecting using ‘/’ with sqlplus.

  References: #3705

- [oracle] [bug]

  Fixed a bug in the result proxy used mainly by Oracle when binary and other LOB types are in play, such that when query / statement caching were used, the type-level result processors, notably that required by the binary type itself but also any other processor, would become lost after the first run of the statement due to it being removed from the cached result metadata.

  References: #3699

### misc

- [bug] [py3k]

  Fixed bug in “to_list” conversion where a single bytes object would be turned into a list of individual characters. This would impact among other things using the `Query.get()` method on a primary key that’s a bytes object.

  References: #3660

## 1.0.12

Released: February 15, 2016

### orm

- [orm] [bug]

  Fixed bug in `Session.merge()` where an object with a composite primary key that has values for some but not all of the PK fields would emit a SELECT statement leaking the internal NEVER_SET symbol into the query, rather than detecting that this object does not have a searchable primary key and no SELECT should be emitted.

  References: #3647

- [orm] [bug]

  Fixed regression since 0.9 where the 0.9 style loader options system failed to accommodate for multiple `undefer_group()` loader options in a single query. Multiple `undefer_group()` options will now be taken into account even against the same entity.

  References: #3623

### engine

- [engine] [bug] [mysql]

  Revisiting #2696, first released in 1.0.10, which attempts to work around Python 2’s lack of exception context reporting by emitting a warning for an exception that was interrupted by a second exception when attempting to roll back the already-failed transaction; this issue continues to occur for MySQL backends in conjunction with a savepoint that gets unexpectedly lost, which then causes a “no such savepoint” error when the rollback is attempted, obscuring what the original condition was.

  The approach has been generalized to the Core “safe reraise” function which takes place across the ORM and Core in any place that a transaction is being rolled back in response to an error which occurred trying to commit, including the context managers provided by `Session` and `Connection`, and taking place for operations such as a failure on “RELEASE SAVEPOINT”. Previously, the fix was only in place for a specific path within the ORM flush/commit process; it now takes place for all transactional context managers as well.

  References: #2696

### sql

- [sql] [bug]

  Fixed issue where the “literal_binds” flag was not propagated for `insert()`, `update()` or `delete()` constructs when compiled to string SQL. Pull request courtesy Tim Tate.

  References: #3643

- [sql] [bug]

  Fixed issue where inadvertent use of the Python `__contains__` override with a column expression (e.g. by using `'x' in col`) would cause an endless loop in the case of an ARRAY type, as Python defers this to `__getitem__` access which never raises for this type. Overall, all use of `__contains__` now raises NotImplementedError.

  References: #3642

- [sql] [bug]

  Fixed bug in `Table` metadata construct which appeared around the 0.9 series where adding columns to a `Table` that was unpickled would fail to correctly establish the `Column` within the ‘c’ collection, leading to issues in areas such as ORM configuration. This could impact use cases such as `extend_existing` and others.

  References: #3632

### postgresql

- [postgresql] [bug]

  Fixed bug in `text()` construct where a double-colon expression would not escape properly, e.g. `some\:\:expr`, as is most commonly required when rendering PostgreSQL-style CAST expressions.

  References: #3644

### mssql

- [mssql] [bug]

  Fixed the syntax of the `extract()` function when used on MSSQL against a datetime value; the quotes around the keyword are removed. Pull request courtesy Guillaume Doumenc.

  References: #3624

- [mssql] [bug] [firebird]

  Fixed 1.0 regression where the eager fetch of cursor.rowcount was no longer called for an UPDATE or DELETE statement emitted via plain text or via the `text()` construct, affecting those drivers that erase cursor.rowcount once the cursor is closed such as SQL Server ODBC and Firebird drivers.

  References: #3622

### oracle

- [oracle] [bug] [jython]

  Fixed a small issue in the Jython Oracle compiler involving the rendering of “RETURNING” which allows this currently unsupported/untested dialect to work rudimentarily with the 1.0 series. Pull request courtesy Carlos Rivas.

  References: #3621

### misc

- [bug] [py3k]

  Fixed bug where some exception re-raise scenarios would attach the exception to itself as the “cause”; while the Python 3 interpreter is OK with this, it could cause endless loops in iPython.

  References: #3625

## 1.0.11

Released: December 22, 2015

### orm

- [orm] [bug]

  Fixed regression caused in 1.0.10 by the fix for #3593 where the check added for a polymorphic joinedload from a poly_subclass->class->poly_baseclass connection would fail for the scenario of class->poly_subclass->class.

  References: #3611

- [orm] [bug]

  Fixed bug where `Session.bulk_update_mappings()` and related would not bump a version id counter when in use. The experience here is still a little rough as the original version id is required in the given dictionaries and there’s not clean error reporting on that yet.

  References: #3610

- [orm] [bug]

  Major fixes to the `Mapper.eager_defaults` flag, this flag would not be honored correctly in the case that multiple UPDATE statements were to be emitted, either as part of a flush or a bulk update operation. Additionally, RETURNING would be emitted unnecessarily within update statements.

  References: #3609

- [orm] [bug]

  Fixed bug where use of the `Query.select_from()` method would cause a subsequent call to the `Query.with_parent()` method to fail.

  References: #3606

### sql

- [sql] [bug]

  Fixed bug in `Update.return_defaults()` which would cause all insert-default holding columns not otherwise included in the SET clause (such as primary key cols) to get rendered into the RETURNING even though this is an UPDATE.

  References: #3609

### mysql

- [mysql] [bug]

  An adjustment to the regular expression used to parse MySQL views, such that we no longer assume the “ALGORITHM” keyword is present in the reflected view source, as some users have reported this not being present in some Amazon RDS environments.

  References: #3613

- [mysql] [bug]

  Added new reserved words for MySQL 5.7 to the MySQL dialect, including ‘generated’, ‘optimizer_costs’, ‘stored’, ‘virtual’. Pull request courtesy Hanno Schlichting.

### misc

- [bug] [ext]

  Further fixes to #3605, pop method on `MutableDict`, where the “default” argument was not included.

  References: #3605

- [bug] [ext]

  Fixed bug in baked loader system where the systemwide monkeypatch for setting up baked lazy loaders would interfere with other loader strategies that rely on lazy loading as a fallback, e.g. joined and subquery eager loaders, leading to `IndexError` exceptions at mapper configuration time.

  References: #3612

## 1.0.10

Released: December 11, 2015

### orm

- [orm] [bug]

  Fixed issue where post_update on a many-to-one relationship would fail to emit an UPDATE in the case where the attribute were set to None and not previously loaded.

  References: #3599

- [orm] [bug]

  Fixed bug which is actually a regression that occurred between versions 0.8.0 and 0.8.1, due #2714. The case where joined eager loading needs to join out over a subclass-bound relationship when “with_polymorphic” were also used would fail to join from the correct entity.

  References: #3593

- [orm] [bug]

  Fixed joinedload bug which would occur when a. the query includes limit/offset criteria that forces a subquery b. the relationship uses “secondary” c. the primaryjoin of the relationship refers to a column that is either not part of the primary key, or is a PK col in a joined-inheritance subclass table that is under a different attribute name than the parent table’s primary key column d. the query defers the columns that are present in the primaryjoin, typically via not being included in load_only(); the necessary column(s) would not be present in the subquery and produce invalid SQL.

  References: #3592

- [orm] [bug]

  A rare case which occurs when a `Session.rollback()` fails in the scope of a `Session.flush()` operation that’s raising an exception, as has been observed in some MySQL SAVEPOINT cases, prevents the original database exception from being observed when it was emitted during flush, but only on Py2K because Py2K does not support exception chaining; on Py3K the originating exception is chained. As a workaround, a warning is emitted in this specific case showing at least the string message of the original database error before we proceed to raise the rollback-originating exception.

  References: #2696

### orm declarative

- [orm] [declarative] [bug]

  Fixed bug where in Py2K a unicode literal would not be accepted as the string name of a class or other argument within declarative using `backref()` on `relationship()`. Pull request courtesy Nils Philippsen.

### sql

- [sql] [feature]

  Added support for parameter-ordered SET clauses in an UPDATE statement. This feature is available by passing the `update.preserve_parameter_order` flag either to the core `Update` construct or alternatively adding it to the `Query.update.update_args` dictionary at the ORM-level, also passing the parameters themselves as a list of 2-tuples. Thanks to Gorka Eguileor for implementation and tests.

  See also

  Parameter Ordered Updates

- [sql] [bug]

  Fixed issue within the `Insert.from_select()` construct whereby the `Select` construct would have its `._raw_columns` collection mutated in-place when compiling the `Insert` construct, when the target `Table` has Python-side defaults. The `Select` construct would compile standalone with the erroneous column present subsequent to compilation of the `Insert`, and the `Insert` statement itself would fail on a second compile attempt due to duplicate bound parameters.

  References: #3603

- [sql] [bug] [postgresql]

  Fixed bug where CREATE TABLE with a no-column table, but a constraint such as a CHECK constraint would render an erroneous comma in the definition; this scenario can occur such as with a PostgreSQL INHERITS table that has no columns of its own.

  References: #3598

### postgresql

- [postgresql] [bug]

  Fixed issue where the “FOR UPDATE OF” PostgreSQL-specific SELECT modifier would fail if the referred table had a schema qualifier; PG needs the schema name to be omitted. Pull request courtesy Diana Clarke.

  References: #3573

- [postgresql] [bug]

  Fixed bug where some varieties of SQL expression passed to the “where” clause of `ExcludeConstraint` would fail to be accepted correctly. Pull request courtesy aisch.

- [postgresql] [bug]

  Fixed the `.python_type` attribute of `INTERVAL` to return `datetime.timedelta` in the same way as that of `python_type`, rather than raising `NotImplementedError`.

  References: #3571

### mysql

- [mysql] [bug]

  Fixed bug in MySQL reflection where the “fractional sections portion” of the `DATETIME`, `TIMESTAMP` and `TIME` types would be incorrectly placed into the `timezone` attribute, which is unused by MySQL, instead of the `fsp` attribute.

  References: #3602

### mssql

- [mssql] [bug]

  Added the error “20006: Write to the server failed” to the list of disconnect errors for the pymssql driver, as this has been observed to render a connection unusable.

  References: #3585

- [mssql] [bug]

  A descriptive ValueError is now raised in the event that SQL server returns an invalid date or time format from a DATE or TIME column, rather than failing with a NoneType error. Pull request courtesy Ed Avis.

- [mssql] [bug]

  Fixed issue where DDL generated for the MSSQL types DATETIME2, TIME and DATETIMEOFFSET with a precision of “zero” would not generate the precision field. Pull request courtesy Jacobo de Vera.

### tests

- [tests] [change]

  The ORM and Core tutorials, which have always been in doctest format, are now exercised within the normal unit test suite in both Python 2 and Python 3.

### misc

- [bug] [ext]

  Added support for the `dict.pop()` and `dict.popitem()` methods to the `MutableDict` class.

  References: #3605

- [bug] [py3k]

  Updates to internal getargspec() calls, some py36-related fixture updates, and alterations to two iterators to “return” instead of raising StopIteration, to allow tests to pass without errors or warnings on Py3.5, Py3.6, pull requests courtesy Jacob MacDonald, Luri de Silvio, and Phil Jones.

- [bug] [ext]

  Fixed an issue in baked queries where the .get() method, used either directly or within lazy loads, didn’t consider the mapper’s “get clause” as part of the cache key, causing bound parameter mismatches if the clause got re-generated. This clause is cached by mappers on the fly but in highly concurrent scenarios may be generated more than once when first accessed.

  References: #3597

## 1.0.9

Released: October 20, 2015

### orm

- [orm] [feature]

  Added new method `Query.one_or_none()`; same as `Query.one()` but returns None if no row found. Pull request courtesy esiegerman.

- [orm] [bug] [postgresql]

  Fixed regression in 1.0 where new feature of using “executemany” for UPDATE statements in the ORM (e.g. UPDATE statements are now batched with executemany() in a flush) would break on PostgreSQL and other RETURNING backends when using server-side version generation schemes, as the server side value is retrieved via RETURNING which is not supported with executemany.

  References: #3556

- [orm] [bug]

  Fixed rare TypeError which could occur when stringifying certain kinds of internal column loader options within internal logging.

  References: #3539

- [orm] [bug]

  Fixed bug in `Session.bulk_save_objects()` where a mapped column that had some kind of “fetch on update” value and was not locally present in the given object would cause an AttributeError within the operation.

  References: #3525

- [orm] [bug]

  Fixed 1.0 regression where the “noload” loader strategy would fail to function for a many-to-one relationship. The loader used an API to place “None” into the dictionary which no longer actually writes a value; this is a side effect of #3061.

  References: #3510

### examples

- [examples] [bug]

  Fixed two issues in the “history_meta” example where history tracking could encounter empty history, and where a column keyed to an alternate attribute name would fail to track properly. Fixes courtesy Alex Fraser.

### sql

- [sql] [bug]

  Fixed regression in 1.0-released default-processor for multi-VALUES insert statement, #3288, where the column type for the default-holding column would not be propagated to the compiled statement in the case where the default was being used, leading to bind-level type handlers not being invoked.

  References: #3520

### postgresql

- [postgresql] [bug]

  An adjustment to the new PostgreSQL feature of reflecting storage options and USING of #3455 released in 1.0.6, to disable the feature for PostgreSQL versions < 8.2 where the `reloptions` column is not provided; this allows Amazon Redshift to again work as it is based on an 8.0.x version of PostgreSQL. Fix courtesy Pete Hollobon.

### oracle

- [oracle] [bug] [py3k]

  Fixed support for cx_Oracle version 5.2, which was tripping up SQLAlchemy’s version detection under Python 3 and inadvertently not using the correct unicode mode for Python 3. This would cause issues such as bound variables mis-interpreted as NULL and rows silently not being returned.

  This change is also backported to: 0.7.0b1

  References: #3491

- [oracle] [bug]

  Fixed bug in Oracle dialect where reflection of tables and other symbols with names quoted to force all-lower-case would not be identified properly in reflection queries. The `quoted_name` construct is now applied to incoming symbol names that detect as forced into all-lower-case within the “name normalize” process.

  References: #3548

### misc

- [feature] [ext]

  Added the `AssociationProxy.info` parameter to the `AssociationProxy` constructor, to suit the `AssociationProxy.info` accessor that was added in #2971. This is possible because `AssociationProxy` is constructed explicitly, unlike a hybrid which is constructed implicitly via the decorator syntax.

  References: #3551

- [bug] [sybase]

  Fixed two issues regarding Sybase reflection, allowing tables without primary keys to be reflected as well as ensured that a SQL statement involved in foreign key detection is pre-fetched up front to avoid driver issues upon nested queries. Fixes here courtesy Eugene Zapolsky; note that we cannot currently test Sybase to locally verify these changes.

  References: #3508, #3509

## 1.0.8

Released: July 22, 2015

### engine

- [engine] [bug]

  Fixed critical issue whereby the pool “checkout” event handler may be called against a stale connection without the “connect” event handler having been called, in the case where the pool attempted to reconnect after being invalidated and failed; the stale connection would remain present and would be used on a subsequent attempt. This issue has a greater impact in the 1.0 series subsequent to 1.0.2, as it also delivers a blanked-out `.info` dictionary to the event handler; prior to 1.0.2 the `.info` dictionary is still the previous one.

  This change is also backported to: 0.7.0b1

  References: #3497

### sqlite

- [sqlite] [bug]

  Fixed bug in SQLite dialect where reflection of UNIQUE constraints that included non-alphabetic characters in the names, like dots or spaces, would not be reflected with their name.

  This change is also backported to: 0.9.10

  References: #3495

### misc

- [misc] [bug]

  Fixed an issue where a particular base class within utils didn’t implement `__slots__`, and therefore meant all subclasses of that class didn’t either, negating the rationale for `__slots__` to be in use. Didn’t cause any issue except on IronPython which apparently does not implement `__slots__` behavior compatibly with cPython.

  References: #3494

## 1.0.7

Released: July 20, 2015

### orm

- [orm] [bug]

  Fixed 1.0 regression where value objects that override `__eq__()` to return a non-boolean-capable object, such as some geoalchemy types as well as numpy types, were being tested for `bool()` during a unit of work update operation, where in 0.9 the return value of `__eq__()` was tested against “is True” to guard against this.

  References: #3469

- [orm] [bug]

  Fixed 1.0 regression where a “deferred” attribute would not populate correctly if it were loaded within the “optimized inheritance load”, which is a special SELECT emitted in the case of joined table inheritance used to populate expired or unloaded attributes against a joined table without loading the base table. This is related to the fact that SQLA 1.0 no longer guesses about loading deferred columns and must be directed explicitly.

  References: #3468

- [orm] [bug]

  Fixed 1.0 regression where the “parent entity” of a synonym- mapped attribute on top of an `aliased()` object would resolve to the original mapper, not the `aliased()` version of it, thereby causing problems for a `Query` that relies on this attribute (e.g. it’s the only representative attribute given in the constructor) to figure out the correct FROM clause for the query.

  References: #3466

### orm declarative

- [orm] [declarative] [bug]

  Fixed bug in `AbstractConcreteBase` extension where a column setup on the ABC base which had a different attribute name vs. column name would not be correctly mapped on the final base class. The failure on 0.9 would be silent whereas on 1.0 it raised an ArgumentError, so may not have been noticed prior to 1.0.

  References: #3480

### engine

- [engine] [bug]

  Fixed regression where new methods on `ResultProxy` used by the ORM `Query` object (part of the performance enhancements of #3175) would not raise the “this result does not return rows” exception in the case where the driver (typically MySQL) fails to generate cursor.description correctly; an AttributeError against NoneType would be raised instead.

  References: #3481

- [engine] [bug]

  Fixed regression where `ResultProxy.keys()` would return un-adjusted internal symbol names for “anonymous” labels, which are the “foo_1” types of labels we see generated for SQL functions without labels and similar. This was a side effect of the performance enhancements implemented as part of #918.

  References: #3483

### sql

- [sql] [feature]

  Added a `ColumnElement.cast()` method which performs the same purpose as the standalone `cast()` function. Pull request courtesy Sebastian Bank.

  References: #3459

- [sql] [bug]

  Fixed bug where coercion of literal `True` or `False` constant in conjunction with `and_()` or `or_()` would fail with an AttributeError.

  References: #3490

- [sql] [bug]

  Fixed potential issue where a custom subclass of `FunctionElement` or other column element that incorrectly states ‘None’ or any other invalid object as the `.type` attribute will report this exception instead of recursion overflow.

  References: #3485

- [sql] [bug]

  Fixed bug where the modulus SQL operator wouldn’t work in reverse due to a missing `__rmod__` method. Pull request courtesy dan-gittik.

### schema

- [schema] [feature]

  Added support for the MINVALUE, MAXVALUE, NO MINVALUE, NO MAXVALUE, and CYCLE arguments for CREATE SEQUENCE as supported by PostgreSQL and Oracle. Pull request courtesy jakeogh.

## 1.0.6

Released: June 25, 2015

### orm

- [orm] [bug]

  Fixed a major regression in the 1.0 series where the version_id_counter feature would cause an object’s version counter to be incremented when there was no net change to the object’s row, but instead an object related to it via relationship (e.g. typically many-to-one) were associated or de-associated with it, resulting in an UPDATE statement that updates the object’s version counter and nothing else. In the use case where the relatively recent “server side” and/or “programmatic/conditional” version counter feature were used (e.g. setting version_id_generator to False), the bug could cause an UPDATE without a valid SET clause to be emitted.

  References: #3465

- [orm] [bug]

  Fixed 1.0 regression where the enhanced behavior of single-inheritance joins of #3222 takes place inappropriately for a JOIN along explicit join criteria with a single-inheritance subclass that does not make use of any discriminator, resulting in an additional “AND NULL” clause.

  References: #3462

- [orm] [bug]

  Fixed bug in new `Session.bulk_update_mappings()` feature where the primary key columns used in the WHERE clause to locate the row would also be included in the SET clause, setting their value to themselves unnecessarily. Pull request courtesy Patrick Hayes.

  References: #3451

- [orm] [bug]

  Fixed an unexpected-use regression whereby custom `Comparator` objects that made use of the `__clause_element__()` method and returned an object that was an ORM-mapped `InstrumentedAttribute` and not explicitly a `ColumnElement` would fail to be correctly handled when passed as an expression to `Session.query()`. The logic in 0.9 happened to succeed on this, so this use case is now supported.

  References: #3448

### sql

- [sql] [bug]

  Fixed a bug where clause adaption as applied to a `Label` object would fail to accommodate the labeled SQL expression in all cases, such that any SQL operation that made use of `Label.self_group()` would use the original unadapted expression. One effect of this would be that an ORM `aliased()` construct would not fully accommodate attributes mapped by `column_property`, such that the un-aliased table could leak out when the property were used in some kinds of SQL comparisons.

  References: #3445

### postgresql

- [postgresql] [feature]

  Added support for storage parameters under CREATE INDEX, using a new keyword argument `postgresql_with`. Also added support for reflection to support both the `postgresql_with` flag as well as the `postgresql_using` flag, which will now be set on `Index` objects that are reflected, as well present in a new “dialect_options” dictionary in the result of `Inspector.get_indexes()`. Pull request courtesy Pete Hollobon.

  See also

  Index Storage Parameters

  References: #3455

- [postgresql] [feature]

  Added new execution option `max_row_buffer` which is interpreted by the psycopg2 dialect when the `stream_results` option is used, which sets a limit on the size of the row buffer that may be allocated. This value is also provided based on the integer value sent to `Query.yield_per()`. Pull request courtesy mcclurem.

- [postgresql] [bug] [pypy]

  Re-fixed this issue first released in 1.0.5 to fix psycopg2cffi JSONB support once again, as they suddenly switched on unconditional decoding of JSONB types in version 2.7.1. Version detection now specifies 2.7.1 as where we should expect the DBAPI to do json encoding for us.

  References: #3439

- [postgresql] [bug]

  Repaired the `ExcludeConstraint` construct to support common features that other objects like `Index` now do, that the column expression may be specified as an arbitrary SQL expression such as `cast` or `text`.

  References: #3454

### mssql

- [mssql] [bug]

  Fixed issue when using `VARBINARY` type in conjunction with an INSERT of NULL + pyodbc; pyodbc requires a special object be passed in order to persist NULL. As the `VARBINARY` type is now usually the default for `LargeBinary` due to #3039, this issue is partially a regression in 1.0. The pymssql driver appears to be unaffected.

  References: #3464

### misc

- [bug] [documentation]

  Fixed an internal “memoization” routine for method types such that a Python descriptor is no longer used; repairs inspectability of these methods including support for Sphinx documentation.

  References: #2077

## 1.0.5

Released: June 7, 2015

### orm

- [orm] [feature]

  Added new event `InstanceEvents.refresh_flush()`, invoked when an INSERT or UPDATE level default value fetched via RETURNING or Python-side default is invoked within the flush process. This is to provide a hook that is no longer present as a result of #3167, where attribute and validation events are no longer called within the flush process.

  References: #3427

- [orm] [bug]

  The “lightweight named tuple” used when a `Query` returns rows failed to implement `__slots__` correctly such that it still had a `__dict__`. This is resolved, but in the extremely unlikely case someone was assigning values to the returned tuples, that will no longer work.

  References: #3420

### engine

- [engine] [feature]

  Added new engine event `ConnectionEvents.engine_disposed()`. Called after the `Engine.dispose()` method is called.

- [engine] [feature]

  Adjustments to the engine plugin hook, such that the `URL.get_dialect()` method will continue to return the ultimate `Dialect` object when a dialect plugin is used, without the need for the caller to be aware of the `Dialect.get_dialect_cls()` method.

  References: #3379

- [engine] [bug]

  Fixed bug where known boolean values used by `engine_from_config()` were not being parsed correctly; these included `pool_threadlocal` and the psycopg2 argument `use_native_unicode`.

  References: #3435

- [engine] [bug]

  Added support for the case of the misbehaving DBAPI that has pep-249 exception names linked to exception classes of an entirely different name, preventing SQLAlchemy’s own exception wrapping from wrapping the error appropriately. The SQLAlchemy dialect in use needs to implement a new accessor `DefaultDialect.dbapi_exception_translation_map` to support this feature; this is implemented now for the py-postgresql dialect.

  References: #3421

- [engine] [bug]

  Fixed bug involving the case when pool checkout event handlers are used and connection attempts are made in the handler itself which fail, the owning connection record would not be freed until the stack trace of the connect error itself were freed. For the case where a test pool of only a single connection were used, this means the pool would be fully checked out until that stack trace were freed. This mostly impacts very specific debugging scenarios and is unlikely to have been noticeable in any production application. The fix applies an explicit checkin of the record before re-raising the caught exception.

  References: #3419

### sql

- [sql] [feature]

  Added official support for a CTE used by the SELECT present inside of `Insert.from_select()`. This behavior worked accidentally up until 0.9.9, when it no longer worked due to unrelated changes as part of #3248. Note that this is the rendering of the WITH clause after the INSERT, before the SELECT; the full functionality of CTEs rendered at the top level of INSERT, UPDATE, DELETE is a new feature targeted for a later release.

  This change is also backported to: 0.9.10

  References: #3418

### postgresql

- [postgresql] [bug] [pypy]

  Repaired some typing and test issues related to the pypy psycopg2cffi dialect, in particular that the current 2.7.0 version does not have native support for the JSONB type. The version detection for psycopg2 features has been tuned into a specific sub-version for psycopg2cffi. Additionally, test coverage has been enabled for the full series of psycopg2 features under psycopg2cffi.

  References: #3439

### mssql

- [mssql] [bug]

  Added a new dialect flag to the MSSQL dialect `legacy_schema_aliasing` which when set to False will disable a very old and obsolete behavior, that of the compiler’s attempt to turn all schema-qualified table names into alias names, to work around old and no longer locatable issues where SQL server could not parse a multi-part identifier name in all circumstances. The behavior prevented more sophisticated statements from working correctly, including those which use hints, as well as CRUD statements that embed correlated SELECT statements. Rather than continue to repair the feature to work with more complex statements, it’s better to just disable it as it should no longer be needed for any modern SQL server version. The flag defaults to True for the 1.0.x series, leaving current behavior unchanged for this version series. In the 1.1 series, it will default to False. For the 1.0 series, when not set to either value explicitly, a warning is emitted when a schema-qualified table is first used in a statement, which suggests that the flag be set to False for all modern SQL Server versions.

  See also

  Legacy Schema Mode

  References: #3424, #3430

### misc

- [feature] [ext]

  Added support for `*args` to be passed to the baked query initial callable, in the same way that `*args` are supported for the `BakedQuery.add_criteria()` and `BakedQuery.with_criteria()` methods. Initial PR courtesy Naoki INADA.

- [feature] [ext]

  Added a new semi-public method to `MutableBase` `MutableBase._get_listen_keys()`. Overriding this method is needed in the case where a `MutableBase` subclass needs events to propagate for attribute keys other than the key to which the mutable type is associated with, when intercepting the `InstanceEvents.refresh()` or `InstanceEvents.refresh_flush()` events. The current example of this is composites using `MutableComposite`.

  References: #3427

- [bug] [ext]

  Fixed regression in the `sqlalchemy.ext.mutable` extension as a result of the bugfix for #3167, where attribute and validation events are no longer called within the flush process. The mutable extension was relying upon this behavior in the case where a column level Python-side default were responsible for generating the new value on INSERT or UPDATE, or when a value were fetched from the RETURNING clause for “eager defaults” mode. The new value would not be subject to any event when populated and the mutable extension could not establish proper coercion or history listening. A new event `InstanceEvents.refresh_flush()` is added which the mutable extension now makes use of for this use case.

  References: #3427

## 1.0.4

Released: May 7, 2015

### orm

- [orm] [bug]

  Fixed unexpected-use regression where in the odd case that the primaryjoin of a relationship involved comparison to an unhashable type such as an HSTORE, lazy loads would fail due to a hash-oriented check on the statement parameters, modified in 1.0 as a result of #3061 to use hashing and modified in #3368 to occur in cases more common than “load on pending”. The values are now checked for the `__hash__` attribute beforehand.

  References: #3416

- [orm] [bug]

  Liberalized an assertion that was added as part of #3347 to protect against unknown conditions when splicing inner joins together within joined eager loads with `innerjoin=True`; if some of the joins use a “secondary” table, the assertion needs to unwrap further joins in order to pass.

  References: #3347, #3412

- [orm] [bug]

  Repaired / added to tests yet more expressions that were reported as failing with the new ‘entity’ key value added to `Query.column_descriptions`, the logic to discover the “from” clause is again reworked to accommodate columns from aliased classes, as well as to report the correct value for the “aliased” flag in these cases.

  References: #3320, #3409

### schema

- [schema] [bug]

  Fixed bug in enhanced constraint-attachment logic introduced in #3341 where in the unusual case of a constraint that refers to a mixture of `Column` objects and string column names at the same time, the auto-attach-on-column-attach logic will be skipped; for the constraint to be auto-attached in this case, all columns must be assembled on the target table up front. Added a new section to the migration document regarding the original feature as well as this change.

  See also

  Constraints referring to unattached Columns can auto-attach to the Table when their referred columns are attached

  References: #3411

### tests

- [tests] [bug] [pypy]

  Fixed an import that prevented “pypy setup.py test” from working correctly.

  This change is also backported to: 0.9.10

  References: #3406

### misc

- [bug] [ext]

  Fixed bug where when using extended attribute instrumentation system, the correct exception would not be raised when `class_mapper()` were called with an invalid input that also happened to not be weak referenceable, such as an integer.

  This change is also backported to: 0.9.10

  References: #3408

## 1.0.3

Released: April 30, 2015

### orm

- [orm] [bug] [pypy]

  Fixed regression from 0.9.10 prior to release due to #3349 where the check for query state on `Query.update()` or `Query.delete()` compared the empty tuple to itself using `is`, which fails on PyPy to produce `True` in this case; this would erroneously emit a warning in 0.9 and raise an exception in 1.0.

  References: #3405

- [orm] [bug]

  Fixed regression from 0.9.10 prior to release where the new addition of `entity` to the `Query.column_descriptions` accessor would fail if the target entity was produced from a core selectable such as a `Table` or `CTE` object.

  References: #3320, #3403

- [orm] [bug]

  Fixed regression within the flush process when an attribute were set to a SQL expression for an UPDATE, and the SQL expression when compared to the previous value of the attribute would produce a SQL comparison other than `==` or `!=`, the exception “Boolean value of this clause is not defined” would raise. The fix ensures that the unit of work will not interpret the SQL expression in this way.

  References: #3402

- [orm] [bug]

  Fixed unexpected use regression due to #2992 where textual elements placed into the `Query.order_by()` clause in conjunction with joined eager loading would be added to the columns clause of the inner query in such a way that they were assumed to be table-bound column names, in the case where the joined eager load needs to wrap the query in a subquery to accommodate for a limit/offset.

  Originally, the behavior here was intentional, in that a query such as `query(User).order_by('name').limit(1)` would order by `user.name` even if the query was modified by joined eager loading to be within a subquery, as `'name'` would be interpreted as a symbol to be located within the FROM clauses, in this case `User.name`, which would then be copied into the columns clause to ensure it were present for ORDER BY. However, the feature fails to anticipate the case where `order_by("name")` refers to a specific label name present in the local columns clause already and not a name bound to a selectable in the FROM clause.

  Beyond that, the feature also fails for deprecated cases such as `order_by("name desc")`, which, while it emits a warning that `text()` should be used here (note that the issue does not impact cases where `text()` is used explicitly), still produces a different query than previously where the “name desc” expression is copied into the columns clause inappropriately. The resolution is such that the “joined eager loading” aspect of the feature will skip over these so-called “label reference” expressions when augmenting the inner columns clause, as though they were `text()` constructs already.

  References: #3392

- [orm] [bug]

  Fixed a regression regarding the `MapperEvents.instrument_class()` event where its invocation was moved to be after the class manager’s instrumentation of the class, which is the opposite of what the documentation for the event explicitly states. The rationale for the switch was due to Declarative taking the step of setting up the full “instrumentation manager” for a class before it was mapped for the purpose of the new `@declared_attr` features described in Improvements to declarative mixins, @declared_attr and related features, but the change was also made against the classical use of `Mapper` for consistency. However, SQLSoup relies upon the instrumentation event happening before any instrumentation under classical mapping. The behavior is reverted in the case of classical and declarative mapping, the latter implemented by using a simple memoization without using class manager.

  References: #3388

- [orm] [bug]

  Fixed issue in new `QueryEvents.before_compile()` event where changes made to the `Query` object’s collection of entities to load within the event would render in the SQL, but would not be reflected during the loading process.

  References: #3387

### engine

- [engine] [feature]

  New features added to support engine/pool plugins with advanced functionality. Added a new “soft invalidate” feature to the connection pool at the level of the checked out connection wrapper as well as the `_ConnectionRecord`. This works similarly to a modern pool invalidation in that connections aren’t actively closed, but are recycled only on next checkout; this is essentially a per-connection version of that feature. A new event `PoolEvents.soft_invalidate()` is added to complement it.

  Also added new flag `ExceptionContext.invalidate_pool_on_disconnect`. Allows an error handler within `ConnectionEvents.handle_error()` to maintain a “disconnect” condition, but to handle calling invalidate on individual connections in a specific manner within the event.

  References: #3379

- [engine] [feature]

  Added new event `do_connect`, which allows interception / replacement of when the `Dialect.connect()` hook is called to create a DBAPI connection. Also added dialect plugin hooks `Dialect.get_dialect_cls()` and `Dialect.engine_created()` which allow external plugins to add events to existing dialects using entry points.

  References: #3355

### sql

- [sql] [feature]

  Added a placeholder method `TypeEngine.compare_against_backend()` which is now consumed by Alembic migrations as of 0.7.6. User-defined types can implement this method to assist in the comparison of a type against one reflected from the database.

- [sql] [bug]

  Fixed bug where the truncation of long labels in SQL could produce a label that overlapped another label that is not truncated; this because the length threshold for truncation was greater than the portion of the label that remains after truncation. These two values have now been made the same; label_length - 6. The effect here is that shorter column labels will be “truncated” where they would not have been truncated before.

  References: #3396

- [sql] [bug]

  Fixed regression due to #3282 where the `tables` collection passed as a keyword argument to the `DDLEvents.before_create()`, `DDLEvents.after_create()`, `DDLEvents.before_drop()`, and `DDLEvents.after_drop()` events would no longer be a list of tables, but instead a list of tuples which contained a second entry with foreign keys to be added or dropped. As the `tables` collection, while documented as not necessarily stable, has come to be relied upon, this change is considered a regression. Additionally, in some cases for “drop”, this collection would be an iterator that would cause the operation to fail if prematurely iterated. The collection is now a list of table objects in all cases and test coverage for the format of this collection is now added.

  References: #3391

### misc

- [bug] [ext]

  Fixed bug in association proxy where an any()/has() on an relationship->scalar non-object attribute comparison would fail, e.g. `filter(Parent.some_collection_to_attribute.any(Child.attr == 'foo'))`

  References: #3397

## 1.0.2

Released: April 24, 2015

### orm declarative

- [orm] [declarative] [bug]

  Fixed unexpected use regression regarding the declarative `__declare_first__` and `__declare_last__` accessors where these would no longer be called on the superclass of the declarative base.

  References: #3383

### sql

- [sql] [bug]

  Fixed a regression that was incorrectly fixed in 1.0.0b4 (hence becoming two regressions); reports that SELECT statements would GROUP BY a label name and fail was misconstrued that certain backends such as SQL Server should not be emitting ORDER BY or GROUP BY on a simple label name at all; when in fact, we had forgotten that 0.9 was already emitting ORDER BY on a simple label name for all backends, as described in Label constructs can now render as their name alone in an ORDER BY, even though 1.0 includes a rewrite of this logic as part of #2992. As far as emitting GROUP BY against a simple label, even PostgreSQL has cases where it will raise an error even though the label to group on should be apparent, so it is clear that GROUP BY should never be rendered in this way automatically.

  In 1.0.2, SQL Server, Firebird and others will again emit ORDER BY on a simple label name when passed a `Label` construct that is also present in the columns clause. Additionally, no backend will emit GROUP BY against the simple label name only when passed a `Label` construct.

  References: #3338, #3385

## 1.0.1

Released: April 23, 2015

### orm

- [orm] [bug]

  Fixed issue where a query of the form `query(B).filter(B.a != A(id=7))` would render the `NEVER_SET` symbol, when given a transient object. For a persistent object, it would always use the persisted database value and not the currently set value. Assuming autoflush is turned on, this usually would not be apparent for persistent values, as any pending changes would be flushed first in any case. However, this is inconsistent vs. the logic used for the non-negated comparison, `query(B).filter(B.a == A(id=7))`, which does use the current value and additionally allows comparisons to transient objects. The comparison now uses the current value and not the database-persisted value.

  Unlike the other `NEVER_SET` issues that are repaired as regressions caused by #3061 in this release, this particular issue is present at least as far back as 0.8 and possibly earlier, however it was discovered as a result of repairing the related `NEVER_SET` issues.

  See also

  A “negated contains or equals” relationship comparison will use the current value of attributes, not the database value

  References: #3374

- [orm] [bug]

  Fixed unexpected use regression cause by #3061 where the NEVER_SET symbol could leak into relationship-oriented queries, including `filter()` and `with_parent()` queries. The `None` symbol is returned in all cases, however many of these queries have never been correctly supported in any case, and produce comparisons to NULL without using the IS operator. For this reason, a warning is also added to that subset of relationship queries that don’t currently provide for `IS NULL`.

  See also

  Warnings emitted when comparing objects with None values to relationships

  References: #3371

- [orm] [bug]

  Fixed a regression caused by #3061 where the NEVER_SET symbol could leak into a lazyload query, subsequent to the flush of a pending object. This would occur typically for a many-to-one relationship that does not use a simple “get” strategy. The good news is that the fix improves efficiency vs. 0.9, because we can now skip the SELECT statement entirely when we detect NEVER_SET symbols present in the parameters; prior to #3061, we couldn’t discern if the None here were set or not.

  References: #3368

### engine

- [engine] [bug]

  Added the string value `"none"` to those accepted by the `Pool.reset_on_return` parameter as a synonym for `None`, so that string values can be used for all settings, allowing utilities like `engine_from_config()` to be usable without issue.

  This change is also backported to: 0.9.10

  References: #3375

### sql

- [sql] [bug]

  Fixed issue where a straight SELECT EXISTS query would fail to assign the proper result type of Boolean to the result mapping, and instead would leak column types from within the query into the result map. This issue exists in 0.9 and earlier as well, however has less of an impact in those versions. In 1.0, due to #918 this becomes a regression in that we now rely upon the result mapping to be very accurate, else we can assign result-type processors to the wrong column. In all versions, this issue also has the effect that a simple EXISTS will not apply the Boolean type handler, leading to simple 1/0 values for backends without native boolean instead of True/False. The fix includes that an EXISTS columns argument will be anon-labeled like other column expressions; a similar fix is implemented for pure-boolean expressions like `not_(True())`.

  References: #3372

### sqlite

- [sqlite] [bug]

  Fixed a regression due to #3282, where due to the fact that we attempt to assume the availability of ALTER when creating/dropping schemas, in the case of SQLite we simply said to not worry about foreign keys at all, since ALTER is not available, when creating and dropping tables. This meant that the sorting of tables was basically skipped in the case of SQLite, and for the vast majority of SQLite use cases, this is not an issue.

  However, users who were doing DROPs on SQLite with tables that contained data and with referential integrity turned on would then experience errors, as the dependency sorting does matter in the case of DROP with enforced constraints, when those tables have data (SQLite will still happily let you create foreign keys to nonexistent tables and drop tables referring to existing ones with constraints enabled, as long as there’s no data being referenced).

  In order to maintain the new feature of #3282 while still allowing a SQLite DROP operation to maintain ordering, we now do the sort with full FKs taken under consideration, and if we encounter an unresolvable cycle, only then do we forego attempting to sort the tables; we instead emit a warning and go with the unsorted list. If an environment needs both ordered DROPs and has foreign key cycles, then the warning notes they will need to restore the `use_alter` flag to their `ForeignKey` and `ForeignKeyConstraint` objects so that just those objects will be omitted from the dependency sort.

  See also

  The use_alter flag on ForeignKeyConstraint is (usually) no longer needed - contains an updated note about SQLite.

  References: #3378

### misc

- [bug] [firebird]

  Fixed a regression due to #3034 where limit/offset clauses were not properly interpreted by the Firebird dialect. Pull request courtesy effem-git.

  References: #3380

- [bug] [firebird]

  Fixed support for “literal_binds” mode when using limit/offset with Firebird, so that the values are again rendered inline when this is selected. Related to #3034.

  References: #3381

## 1.0.0

Released: April 16, 2015

### orm

- [orm] [feature]

  Added new argument `Query.update.update_args` which allows kw arguments such as `mysql_limit` to be passed to the underlying `Update` construct. Pull request courtesy Amir Sadoughi.

- [orm] [bug]

  Identified an inconsistency when handling `Query.join()` to the same target more than once; it implicitly dedupes only in the case of a relationship join, and due to #3233, in 1.0 a join to the same table twice behaves differently than 0.9 in that it no longer erroneously aliases. To help document this change, the verbiage regarding #3233 in the migration notes has been generalized, and a warning has been added when `Query.join()` is called against the same target relationship more than once.

  References: #3367

- [orm] [bug]

  Made a small improvement to the heuristics of relationship when determining remote side with semi-self-referential (e.g. two joined inh subclasses referring to each other), non-simple join conditions such that the parententity is taken into account and can reduce the need for using the `remote()` annotation; this can restore some cases that might have worked without the annotation prior to 0.9.4 via #2948.

  References: #3364

### sql

- [sql] [feature]

  The topological sorting used to sort `Table` objects and available via the `MetaData.sorted_tables` collection will now produce a deterministic ordering; that is, the same ordering each time given a set of tables with particular names and dependencies. This is to help with comparison of DDL scripts and other use cases. The tables are sent to the topological sort sorted by name, and the topological sort itself will process the incoming data in an ordered fashion. Pull request courtesy Sebastian Bank.

  See also

  MetaData.sorted_tables accessor is “deterministic”

  References: #3084

- [sql] [bug]

  Fixed issue where a `MetaData` object that used a naming convention would not properly work with pickle. The attribute was skipped leading to inconsistencies and failures if the unpickled `MetaData` object were used to base additional tables from.

  This change is also backported to: 0.9.10

  References: #3362

### postgresql

- [postgresql] [bug]

  Fixed a long-standing bug where the `Enum` type as used with the psycopg2 dialect in conjunction with non-ascii values and `native_enum=False` would fail to decode return results properly. This stemmed from when the PG `ENUM` type used to be a standalone type without a “non native” option.

  This change is also backported to: 0.9.10

  References: #3354

### mssql

- [mssql] [bug]

  Fixed a regression where the “last inserted id” mechanics would fail to store the correct value for MSSQL on an INSERT where the primary key value was present in the insert params before execution, as well as in the case where an INSERT from SELECT would state the target columns as column objects, instead of string keys.

  References: #3360

- [mssql] [bug]

  Using the `Binary` constructor now present in pymssql rather than patching one in. Pull request courtesy Ramiro Morales.

### tests

- [tests] [bug]

  Fixed the pathing used when tests run; for sqla_nose.py and py.test, the “./lib” prefix is again inserted at the head of sys.path but only if sys.flags.no_user_site isn’t set; this makes it act just like the way Python puts “.” in the current path by default. For tox, we are setting the PYTHONNOUSERSITE flag now.

  References: #3356

## 1.0.0b5

Released: April 3, 2015

### orm

- [orm] [bug]

  Fixed bug where the state tracking within multiple, nested `Session.begin_nested()` operations would fail to propagate the “dirty” flag for an object that had been updated within the inner savepoint, such that if the enclosing savepoint were rolled back, the object would not be part of the state that was expired and therefore reverted to its database state.

  This change is also backported to: 0.9.10

  References: #3352

- [orm] [bug]

  `Query` doesn’t support joins, subselects, or special FROM clauses when using the `Query.update()` or `Query.delete()` methods; instead of silently ignoring these fields if methods like `Query.join()` or `Query.select_from()` has been called, an error is raised. In 0.9.10 this only emits a warning.

  References: #3349

- [orm] [bug]

  Added a list() call around a weak dictionary used within the commit phase of the session, which without it could cause a “dictionary changed size during iter” error if garbage collection interacted within the process. Change was introduced by #3139.

- [orm] [bug]

  Fixed a bug related to “nested” inner join eager loading, which exists in 0.9 as well but is more of a regression in 1.0 due to #3008 which turns on “nested” by default, such that a joined eager load that travels across sibling paths from a common ancestor using innerjoin=True will correctly splice each “innerjoin” sibling into the appropriate part of the join, when a series of inner/outer joins are mixed together.

  References: #3347

### sql

- [sql] [bug]

  The warning emitted by the unicode type for a non-unicode type has been liberalized to warn for values that aren’t even string values, such as integers; previously, the updated warning system of 1.0 made use of string formatting operations which would raise an internal TypeError. While these cases should ideally raise totally, some backends like SQLite and MySQL do accept them and are potentially in use by legacy code, not to mention that they will always pass through if unicode conversion is turned off for the target backend.

  References: #3346

### postgresql

- [postgresql] [bug]

  Fixed bug where updated PG index reflection as a result of #3184 would cause index operations to fail on PostgreSQL versions 8.4 and earlier. The enhancements are now disabled when using an older version of PostgreSQL.

  References: #3343

## 1.0.0b4

Released: March 29, 2015

### sql

- [sql] [bug]

  Fixed bug in new “label resolution” feature of #2992 where a label that was anonymous, then labeled again with a name, would fail to be locatable via a textual label. This situation occurs naturally when a mapped `column_property()` is given an explicit label in a query.

  References: #3340

- [sql] [bug]

  Fixed bug in new “label resolution” feature of #2992 where the string label placed in the order_by() or group_by() of a statement would place higher priority on the name as found inside the FROM clause instead of a more locally available name inside the columns clause.

  References: #3335

### schema

- [schema] [feature]

  The “auto-attach” feature of constraints such as `UniqueConstraint` and `CheckConstraint` has been further enhanced such that when the constraint is associated with non-table-bound `Column` objects, the constraint will set up event listeners with the columns themselves such that the constraint auto attaches at the same time the columns are associated with the table. This in particular helps in some edge cases in declarative but is also of general use.

  See also

  Constraints referring to unattached Columns can auto-attach to the Table when their referred columns are attached

  References: #3341

### mysql

- [mysql] [bug] [pymysql]

  Fixed unicode support for PyMySQL when using an “executemany” operation with unicode parameters. SQLAlchemy now passes both the statement as well as the bound parameters as unicode objects, as PyMySQL generally uses string interpolation internally to produce the final statement, and in the case of executemany does the “encode” step only on the final statement.

  This change is also backported to: 0.9.10

  References: #3337

### mssql

- [mssql] [bug] [firebird] [oracle] [sybase]

  Turned off the “simple order by” flag on the MSSQL, Oracle dialects; this is the flag that per #2992 causes an order by or group by an expression that’s also in the columns clause to be copied by label, even if referenced as the expression object. The behavior for MSSQL is now the old behavior that copies the whole expression in by default, as MSSQL can be picky on these particularly in GROUP BY expressions. The flag is also turned off defensively for the Firebird and Sybase dialects.

  Note

  this resolution was incorrect, please see version 1.0.2 for a rework of this resolution.

  References: #3338

## 1.0.0b3

Released: March 20, 2015

### mysql

- [mysql] [bug]

  Repaired the commit for issue #2771 which was inadvertently commented out.

  References: #2771

## 1.0.0b2

Released: March 20, 2015

### orm

- [orm] [bug]

  Fixed unexpected use regression from pullreq github:137 where Py2K unicode literals (e.g. `u""`) would not be accepted by the `relationship.cascade` option. Pull request courtesy Julien Castets.

  References: #3327

### orm declarative

- [orm] [declarative] [change]

  Loosened some restrictions that were added to `@declared_attr` objects, such that they were prevented from being called outside of the declarative process; this is related to the enhancements of #3150 which allow `@declared_attr` to return a value that is cached based on the current class as it’s being configured. The exception raise has been removed, and the behavior changed so that outside of the declarative process, the function decorated by `@declared_attr` is called every time just like a regular `@property`, without using any caching, as none is available at this stage.

  References: #3331

### engine

- [engine] [bug]

  The “auto close” for `ResultProxy` is now a “soft” close. That is, after exhausting all rows using the fetch methods, the DBAPI cursor is released as before and the object may be safely discarded, but the fetch methods may continue to be called for which they will return an end-of-result object (None for fetchone, empty list for fetchmany and fetchall). Only if `ResultProxy.close()` is called explicitly will these methods raise the “result is closed” error.

  See also

  ResultProxy “auto close” is now a “soft” close

  References: #3329, #3330

### mysql

- [mysql] [bug] [py3k]

  Fixed the `BIT` type on Py3K which was not using the `ord()` function correctly. Pull request courtesy David Marin.

  This change is also backported to: 0.9.10

  References: #3333

- [mysql] [bug]

  Fixes to fully support using the `'utf8mb4'` MySQL-specific charset with MySQL dialects, in particular MySQL-Python and PyMySQL. In addition, MySQL databases that report more unusual charsets such as ‘koi8u’ or ‘eucjpms’ will also work correctly. Pull request courtesy Thomas Grainger.

  References: #2771

## 1.0.0b1

Released: March 13, 2015

Version 1.0.0b1 is the first release of the 1.0 series. Many changes described here are also present in the 0.9 and sometimes the 0.8 series as well. For changes that are specific to 1.0 with an emphasis on compatibility concerns, see What’s New in SQLAlchemy 1.0?.

### general

- [general] [feature]

  Structural memory use has been improved via much more significant use of `__slots__` for many internal objects. This optimization is particularly geared towards the base memory size of large applications that have lots of tables and columns, and greatly reduces memory size for a variety of high-volume objects including event listening internals, comparator objects and parts of the ORM attribute and loader strategy system.

  See also

  Significant Improvements in Structural Memory Use

- [general] [bug]

  The `__module__` attribute is now set for all those SQL and ORM functions that are derived as “public factory” symbols, which should assist with documentation tools being able to report on the target module.

  References: #3218

### orm

- [orm] [feature]

  Added a new entry `"entity"` to the dictionaries returned by `Query.column_descriptions`. This refers to the primary ORM mapped class or aliased class that is referred to by the expression. Compared to the existing entry for `"type"`, it will always be a mapped entity, even if extracted from a column expression, or None if the given expression is a pure core expression. See also #3403 which repaired a regression in this feature which was unreleased in 0.9.10 but was released in the 1.0 version.

  This change is also backported to: 0.9.10

  References: #3320

- [orm] [feature]

  Added new parameter `Session.connection.execution_options` which may be used to set up execution options on a `Connection` when it is first checked out, before the transaction has begun. This is used to set up options such as isolation level on the connection before the transaction starts.

  See also

  Setting Transaction Isolation Levels / DBAPI AUTOCOMMIT - new documentation section detailing best practices for setting transaction isolation with sessions.

  This change is also backported to: 0.9.9

  References: #3296

- [orm] [feature]

  Added new method `Session.invalidate()`, functions similarly to `Session.close()`, except also calls `Connection.invalidate()` on all connections, guaranteeing that they will not be returned to the connection pool. This is useful in situations e.g. dealing with gevent timeouts when it is not safe to use the connection further, even for rollbacks.

  This change is also backported to: 0.9.9

- [orm] [feature]

  The “primaryjoin” model has been stretched a bit further to allow a join condition that is strictly from a single column to itself, translated through some kind of SQL function or expression. This is kind of experimental, but the first proof of concept is a “materialized path” join condition where a path string is compared to itself using “like”. The `ColumnOperators.like()` operator has also been added to the list of valid operators to use in a primaryjoin condition.

  This change is also backported to: 0.9.5

  References: #3029

- [orm] [feature]

  Added new utility function `make_transient_to_detached()` which can be used to manufacture objects that behave as though they were loaded from a session, then detached. Attributes that aren’t present are marked as expired, and the object can be added to a Session where it will act like a persistent one.

  This change is also backported to: 0.9.5

  References: #3017

- [orm] [feature]

  Added a new event suite `QueryEvents`. The `QueryEvents.before_compile()` event allows the creation of functions which may place additional modifications to `Query` objects before the construction of the SELECT statement. It is hoped that this event be made much more useful via the advent of a new inspection system that will allow for detailed modifications to be made against `Query` objects in an automated fashion.

  See also

  `QueryEvents`

  References: #3317

- [orm] [feature]

  The subquery wrapping which occurs when joined eager loading is used with a one-to-many query that also features LIMIT, OFFSET, or DISTINCT has been disabled in the case of a one-to-one relationship, that is a one-to-many with `relationship.uselist` set to False. This will produce more efficient queries in these cases.

  See also

  Subqueries no longer applied to uselist=False joined eager loads

  References: #3249

- [orm] [feature]

  Mapped state internals have been reworked to allow for a 50% reduction in callcounts specific to the “expiration” of objects, as in the “auto expire” feature of `Session.commit()` and for `Session.expire_all()`, as well as in the “cleanup” step which occurs when object states are garbage collected.

  References: #3307

- [orm] [feature]

  A warning is emitted when the same polymorphic identity is assigned to two different mappers in the same hierarchy. This is typically a user error and means that the two different mapping types cannot be correctly distinguished at load time. Pull request courtesy Sebastian Bank.

  References: #3262

- [orm] [feature]

  A new series of `Session` methods which provide hooks directly into the unit of work’s facility for emitting INSERT and UPDATE statements has been created. When used correctly, this expert-oriented system can allow ORM-mappings to be used to generate bulk insert and update statements batched into executemany groups, allowing the statements to proceed at speeds that rival direct use of the Core.

  See also

  Bulk Operations

  References: #3100

- [orm] [feature]

  Added a parameter `Query.join.isouter` which is synonymous with calling `Query.outerjoin()`; this flag is to provide a more consistent interface compared to Core `FromClause.join()`. Pull request courtesy Jonathan Vanasco.

  References: #3217

- [orm] [feature]

  Added new event handlers `AttributeEvents.init_collection()` and `AttributeEvents.dispose_collection()`, which track when a collection is first associated with an instance and when it is replaced. These handlers supersede the `collection.linker()` annotation. The old hook remains supported through an event adapter.

- [orm] [feature]

  The `Query` will raise an exception when `Query.yield_per()` is used with mappings or options where either subquery eager loading, or joined eager loading with collections, would take place. These loading strategies are not currently compatible with yield_per, so by raising this error, the method is safer to use. Eager loads can be disabled with the `lazyload('*')` option or `Query.enable_eagerloads()`.

  See also

  Joined/Subquery eager loading explicitly disallowed with yield_per

- [orm] [feature]

  A new implementation for `KeyedTuple` used by the `Query` object offers dramatic speed improvements when fetching large numbers of column-oriented rows.

  See also

  New KeyedTuple implementation dramatically faster

  References: #3176

- [orm] [feature]

  The behavior of `joinedload.innerjoin` as well as `relationship.innerjoin` is now to use “nested” inner joins, that is, right-nested, as the default behavior when an inner join joined eager load is chained to an outer join eager load.

  See also

  Right inner join nesting now the default for joinedload with innerjoin=True

  References: #3008

- [orm] [feature]

  UPDATE statements can now be batched within an ORM flush into more performant executemany() call, similarly to how INSERT statements can be batched; this will be invoked within flush to the degree that subsequent UPDATE statements for the same mapping and table involve the identical columns within the VALUES clause, that no SET-level SQL expressions are embedded, and that the versioning requirements for the mapping are compatible with the backend dialect’s ability to return a correct rowcount for an executemany operation.

- [orm] [feature]

  The `info` parameter has been added to the constructor for `SynonymProperty` and `ComparableProperty`.

  References: #2963

- [orm] [feature]

  The `InspectionAttr.info` collection is now moved down to `InspectionAttr`, where in addition to being available on all `MapperProperty` objects, it is also now available on hybrid properties, association proxies, when accessed via `Mapper.all_orm_descriptors`.

  References: #2971

- [orm] [change]

  Mapped attributes marked as deferred without explicit undeferral will now remain “deferred” even if their column is otherwise present in the result set in some way. This is a performance enhancement in that an ORM load no longer spends time searching for each deferred column when the result set is obtained. However, for an application that has been relying upon this, an explicit `undefer()` or similar option should now be used.

- [orm] [changed]

  The `proc()` callable passed to the `create_row_processor()` method of custom `Bundle` classes now accepts only a single “row” argument.

  See also

  API Change for new Bundle feature when custom row loaders are used

- [orm] [changed]

  Deprecated event hooks removed: `populate_instance`, `create_instance`, `translate_row`, `append_result`

  See also

  Deprecated ORM Event Hooks Removed

- [orm] [bug]

  Fixed bug in subquery eager loading where a long chain of eager loads across a polymorphic-subclass boundary in conjunction with polymorphic loading would fail to locate the subclass-link in the chain, erroring out with a missing property name on an `AliasedClass`.

  This change is also backported to: 0.9.5, 0.8.7

  References: #3055

- [orm] [bug]

  Fixed ORM bug where the `class_mapper()` function would mask AttributeErrors or KeyErrors that should raise during mapper configuration due to user errors. The catch for attribute/keyerror has been made more specific to not include the configuration step.

  This change is also backported to: 0.9.5, 0.8.7

  References: #3047

- [orm] [bug]

  Fixed bugs in ORM object comparisons where comparison of many-to-one `!= None` would fail if the source were an aliased class, or if the query needed to apply special aliasing to the expression due to aliased joins or polymorphic querying; also fixed bug in the case where comparing a many-to-one to an object state would fail if the query needed to apply special aliasing due to aliased joins or polymorphic querying.

  This change is also backported to: 0.9.9

  References: #3310

- [orm] [bug]

  Fixed bug where internal assertion would fail in the case where an `after_rollback()` handler for a `Session` incorrectly adds state to that `Session` within the handler, and the task to warn and remove this state (established by #2389) attempts to proceed.

  This change is also backported to: 0.9.9

  References: #3309

- [orm] [bug]

  Fixed bug where TypeError raised when `Query.join()` called with unknown kw arguments would raise its own TypeError due to broken formatting. Pull request courtesy Malthe Borch.

  This change is also backported to: 0.9.9

- [orm] [bug]

  Fixed bug in lazy loading SQL construction whereby a complex primaryjoin that referred to the same “local” column multiple times in the “column that points to itself” style of self-referential join would not be substituted in all cases. The logic to determine substitutions here has been reworked to be more open-ended.

  This change is also backported to: 0.9.9

  References: #3300

- [orm] [bug]

  The “wildcard” loader options, in particular the one set up by the `load_only()` option to cover all attributes not explicitly mentioned, now takes into account the superclasses of a given entity, if that entity is mapped with inheritance mapping, so that attribute names within the superclasses are also omitted from the load. Additionally, the polymorphic discriminator column is unconditionally included in the list, just in the same way that primary key columns are, so that even with load_only() set up, polymorphic loading of subtypes continues to function correctly.

  This change is also backported to: 0.9.9

  References: #3287

- [orm] [bug] [pypy]

  Fixed bug where if an exception were thrown at the start of a `Query` before it fetched results, particularly when row processors can’t be formed, the cursor would stay open with results pending and not actually be closed. This is typically only an issue on an interpreter like PyPy where the cursor isn’t immediately GC’ed, and can in some circumstances lead to transactions/ locks being open longer than is desirable.

  This change is also backported to: 0.9.9

  References: #3285

- [orm] [bug]

  Fixed a leak which would occur in the unsupported and highly non-recommended use case of replacing a relationship on a fixed mapped class many times, referring to an arbitrarily growing number of target mappers. A warning is emitted when the old relationship is replaced, however if the mapping were already used for querying, the old relationship would still be referenced within some registries.

  This change is also backported to: 0.9.9

  References: #3251

- [orm] [bug] [sqlite]

  Fixed bug regarding expression mutations which could express itself as a “Could not locate column” error when using `Query` to select from multiple, anonymous column entities when querying against SQLite, as a side effect of the “join rewriting” feature used by the SQLite dialect.

  This change is also backported to: 0.9.9

  References: #3241

- [orm] [bug]

  Fixed bug where the ON clause for `Query.join()`, and `Query.outerjoin()` to a single-inheritance subclass using `of_type()` would not render the “single table criteria” in the ON clause if the `from_joinpoint=True` flag were set.

  This change is also backported to: 0.9.9

  References: #3232

- [orm] [bug] [engine]

  Fixed bug that affected generally the same classes of event as that of #3199, when the `named=True` parameter would be used. Some events would fail to register, and others would not invoke the event arguments correctly, generally in the case of when an event was “wrapped” for adaption in some other way. The “named” mechanics have been rearranged to not interfere with the argument signature expected by internal wrapper functions.

  This change is also backported to: 0.9.8

  References: #3197

- [orm] [bug]

  Fixed bug that affected many classes of event, particularly ORM events but also engine events, where the usual logic of “de duplicating” a redundant call to `listen()` with the same arguments would fail, for those events where the listener function is wrapped. An assertion would be hit within registry.py. This assertion has now been integrated into the deduplication check, with the added bonus of a simpler means of checking deduplication across the board.

  This change is also backported to: 0.9.8

  References: #3199

- [orm] [bug]

  Fixed warning that would emit when a complex self-referential primaryjoin contained functions, while at the same time remote_side was specified; the warning would suggest setting “remote side”. It now only emits if remote_side isn’t present.

  This change is also backported to: 0.9.8

  References: #3194

- [orm] [bug] [eagerloading]

  Fixed a regression caused by #2976 released in 0.9.4 where the “outer join” propagation along a chain of joined eager loads would incorrectly convert an “inner join” along a sibling join path into an outer join as well, when only descendant paths should be receiving the “outer join” propagation; additionally, fixed related issue where “nested” join propagation would take place inappropriately between two sibling join paths.

  This change is also backported to: 0.9.7

  References: #3131

- [orm] [bug]

  Fixed a regression from 0.9.0 due to #2736 where the `Query.select_from()` method no longer set up the “from entity” of the `Query` object correctly, so that subsequent `Query.filter_by()` or `Query.join()` calls would fail to check the appropriate “from” entity when searching for attributes by string name.

  This change is also backported to: 0.9.7

  References: #2736, #3083

- [orm] [bug]

  Fixed bug where items that were persisted, deleted, or had a primary key change within a savepoint block would not participate in being restored to their former state (not in session, in session, previous PK) after the outer transaction were rolled back.

  This change is also backported to: 0.9.7

  References: #3108

- [orm] [bug]

  Fixed bug in subquery eager loading in conjunction with `with_polymorphic()`, the targeting of entities and columns in the subquery load has been made more accurate with respect to this type of entity and others.

  This change is also backported to: 0.9.7

  References: #3106

- [orm] [bug]

  Additional checks have been added for the case where an inheriting mapper is implicitly combining one of its column-based attributes with that of the parent, where those columns normally don’t necessarily share the same value. This is an extension of an existing check that was added via #1892; however this new check emits only a warning, instead of an exception, to allow for applications that may be relying upon the existing behavior.

  See also

  I’m getting a warning or error about “Implicitly combining column X under attribute Y”

  This change is also backported to: 0.9.5

  References: #3042

- [orm] [bug]

  Modified the behavior of `load_only()` such that primary key columns are always added to the list of columns to be “undeferred”; otherwise, the ORM can’t load the row’s identity. Apparently, one can defer the mapped primary keys and the ORM will fail, that hasn’t been changed. But as load_only is essentially saying “defer all but X”, it’s more critical that PK cols not be part of this deferral.

  This change is also backported to: 0.9.5

  References: #3080

- [orm] [bug]

  Fixed a few edge cases which arise in the so-called “row switch” scenario, where an INSERT/DELETE can be turned into an UPDATE. In this situation, a many-to-one relationship set to None, or in some cases a scalar attribute set to None, may not be detected as a net change in value, and therefore the UPDATE would not reset what was on the previous row. This is due to some as-yet unresolved side effects of the way attribute history works in terms of implicitly assuming None isn’t really a “change” for a previously un-set attribute. See also #3061.

  Note

  This change has been REVERTED in 0.9.6. The full fix will be in version 1.0 of SQLAlchemy.

  This change is also backported to: 0.9.5

  References: #3060

- [orm] [bug]

  Related to #3060, an adjustment has been made to the unit of work such that loading for related many-to-one objects is slightly more aggressive, in the case of a graph of self-referential objects that are to be deleted; the load of related objects is to help determine the correct order for deletion if passive_deletes is not set.

  This change is also backported to: 0.9.5

- [orm] [bug]

  Fixed bug in SQLite join rewriting where anonymized column names due to repeats would not correctly be rewritten in subqueries. This would affect SELECT queries with any kind of subquery + join.

  This change is also backported to: 0.9.5

  References: #3057

- [orm] [bug] [sql]

  Fixes to the newly enhanced boolean coercion in #2804 where the new rules for “where” and “having” wouldn’t take effect for the “whereclause” and “having” kw arguments of the `select()` construct, which is also what `Query` uses so wasn’t working in the ORM either.

  This change is also backported to: 0.9.5

  References: #3013

- [orm] [bug]

  Fixed bug where the session attachment error “object is already attached to session X” would fail to prevent the object from also being attached to the new session, in the case that execution continued after the error raise occurred.

  References: #3301

- [orm] [bug]

  The primary `Mapper` of a `Query` is now passed to the `Session.get_bind()` method when calling upon `Query.count()`, `Query.update()`, `Query.delete()`, as well as queries against mapped columns, `column_property` objects, and SQL functions and expressions derived from mapped columns. This allows sessions that rely upon either customized `Session.get_bind()` schemes or “bound” metadata to work in all relevant cases.

  See also

  Session.get_bind() will receive the Mapper in all relevant Query cases

  References: #1326, #3227, #3242

- [orm] [bug]

  The `PropComparator.of_type()` modifier has been improved in conjunction with loader directives such as `joinedload()` and `contains_eager()` such that if two `PropComparator.of_type()` modifiers of the same base type/path are encountered, they will be joined together into a single “polymorphic” entity, rather than replacing the entity of type A with the one of type B. E.g. a joinedload of `A.b.of_type(BSub1)->BSub1.c` combined with joinedload of `A.b.of_type(BSub2)->BSub2.c` will create a single joinedload of `A.b.of_type((BSub1, BSub2)) -> BSub1.c, BSub2.c`, without the need for the `with_polymorphic` to be explicit in the query.

  See also

  Eager Loading of Polymorphic Subtypes - contains an updated example illustrating the new format.

  References: #3256

- [orm] [bug]

  Repaired support of the `copy.deepcopy()` call when used by the `CascadeOptions` argument, which occurs if `copy.deepcopy()` is being used with `relationship()` (not an officially supported use case). Pull request courtesy duesenfranz.

- [orm] [bug]

  Fixed bug where `Session.expunge()` would not fully detach the given object if the object had been subject to a delete operation that was flushed, but not committed. This would also affect related operations like `make_transient()`.

  See also

  session.expunge() will fully detach an object that’s been deleted

  References: #3139

- [orm] [bug]

  A warning is emitted in the case of multiple relationships that ultimately will populate a foreign key column in conflict with another, where the relationships are attempting to copy values from different source columns. This occurs in the case where composite foreign keys with overlapping columns are mapped to relationships that each refer to a different referenced column. A new documentation section illustrates the example as well as how to overcome the issue by specifying “foreign” columns specifically on a per-relationship basis.

  See also

  Overlapping Foreign Keys

  References: #3230

- [orm] [bug]

  The `Query.update()` method will now convert string key names in the given dictionary of values into mapped attribute names against the mapped class being updated. Previously, string names were taken in directly and passed to the core update statement without any means to resolve against the mapped entity. Support for synonyms and hybrid attributes as the subject attributes of `Query.update()` are also supported.

  See also

  query.update() now resolves string names into mapped attribute names

  References: #3228

- [orm] [bug]

  Improvements to the mechanism used by `Session` to locate “binds” (e.g. engines to use), such engines can be associated with mixin classes, concrete subclasses, as well as a wider variety of table metadata such as joined inheritance tables.

  See also

  Session.get_bind() handles a wider variety of inheritance scenarios

  References: #3035

- [orm] [bug]

  Fixed bug in single table inheritance where a chain of joins that included the same single inh entity more than once (normally this should raise an error) could, in some cases depending on what was being joined “from”, implicitly alias the second case of the single inh entity, producing a query that “worked”. But as this implicit aliasing is not intended in the case of single table inheritance, it didn’t really “work” fully and was very misleading, since it wouldn’t always appear.

  See also

  Changes and fixes in handling of duplicate join targets

  References: #3233

- [orm] [bug]

  The ON clause rendered when using `Query.join()`, `Query.outerjoin()`, or the standalone `join()` / `outerjoin()` functions to a single-inheritance subclass will now include the “single table criteria” in the ON clause even if the ON clause is otherwise hand-rolled; it is now added to the criteria using AND, the same way as if joining to a single-table target using relationship or similar.

  This is sort of in-between feature and bug.

  See also

  single-table-inheritance criteria added to all ON clauses unconditionally

  References: #3222

- [orm] [bug]

  A major rework to the behavior of expression labels, most specifically when used with ColumnProperty constructs with custom SQL expressions and in conjunction with the “order by labels” logic first introduced in 0.9. Fixes include that an `order_by(Entity.some_col_prop)` will now make use of “order by label” rules even if Entity has been subject to aliasing, either via inheritance rendering or via the use of the `aliased()` construct; rendering of the same column property multiple times with aliasing (e.g. `query(Entity.some_prop, entity_alias.some_prop)`) will label each occurrence of the entity with a distinct label, and additionally “order by label” rules will work for both (e.g. `order_by(Entity.some_prop, entity_alias.some_prop)`). Additional issues that could prevent the “order by label” logic from working in 0.9, most notably that the state of a Label could change such that “order by label” would stop working depending on how things were called, has been fixed.

  See also

  ColumnProperty constructs work a lot better with aliases, order_by

  References: #3148, #3188

- [orm] [bug]

  Changed the approach by which the “single inheritance criterion” is applied, when using `Query.from_self()`, or its common user `Query.count()`. The criteria to limit rows to those with a certain type is now indicated on the inside subquery, not the outside one, so that even if the “type” column is not available in the columns clause, we can filter on it on the “inner” query.

  See also

  Change to single-table-inheritance criteria when using from_self(), count()

  References: #3177

- [orm] [bug]

  Made a small adjustment to the mechanics of lazy loading, such that it has less chance of interfering with a joinload() in the very rare circumstance that an object points to itself; in this scenario, the object refers to itself while loading its attributes which can cause a mixup between loaders. The use case of “object points to itself” is not fully supported, but the fix also removes some overhead so for now is part of testing.

  References: #3145

- [orm] [bug]

  The “resurrect” ORM event has been removed. This event hook had no purpose since the old “mutable attribute” system was removed in 0.8.

  References: #3171

- [orm] [bug]

  Fixed bug where attribute “set” events or columns with `@validates` would have events triggered within the flush process, when those columns were the targets of a “fetch and populate” operation, such as an autoincremented primary key, a Python side default, or a server-side default “eagerly” fetched via RETURNING.

  References: #3167

- [orm] [bug] [py3k]

  The `IdentityMap` exposed from `Session.identity_map` now returns lists for `items()` and `values()` in Py3K. Early porting to Py3K here had these returning iterators, when they technically should be “iterable views”..for now, lists are OK.

- [orm] [bug]

  The “evaluator” for query.update()/delete() won’t work with multi-table updates, and needs to be set to synchronize_session=False or synchronize_session=’fetch’; this now raises an exception, with a message to change the synchronize setting. This is upgraded from a warning emitted as of 0.9.7.

  References: #3117

- [orm] [enhancement]

  Adjustment to attribute mechanics concerning when a value is implicitly initialized to None via first access; this action, which has always resulted in a population of the attribute, no longer does so; the None value is returned but the underlying attribute receives no set event. This is consistent with how collections work and allows attribute mechanics to behave more consistently; in particular, getting an attribute with no value does not squash the event that should proceed if the value is actually set to None.

  See also

  Changes to attribute events and other operations regarding attributes that have no pre-existing value

  where bound parameters are rendered inline as strings based on a compile-time option. Work on this feature is courtesy of Dobes Vandermeer.

  > See also

  > Select/Query LIMIT / OFFSET may be specified as an arbitrary SQL expression.

  References: #3061

### orm declarative

- [orm] [declarative] [feature]

  The `declared_attr` construct has newly improved behaviors and features in conjunction with declarative. The decorated function will now have access to the final column copies present on the local mixin when invoked, and will also be invoked exactly once for each mapped class, the returned result being memoized. A new modifier `declared_attr.cascading` is added as well.

  See also

  Improvements to declarative mixins, @declared_attr and related features

  References: #3150

- [orm] [declarative] [bug]

  Fixed “‘NoneType’ object has no attribute ‘concrete’” error when using `AbstractConcreteBase` in conjunction with a subclass that declares `__abstract__`.

  This change is also backported to: 0.9.8

  References: #3185

- [orm] [declarative] [bug]

  Fixed bug where using an `__abstract__` mixin in the middle of a declarative inheritance hierarchy would prevent attributes and configuration being correctly propagated from the base class to the inheriting class.

  References: #3219, #3240

- [orm] [declarative] [bug]

  A relationship set up with `declared_attr` on a `AbstractConcreteBase` base class will now be configured on the abstract base mapping automatically, in addition to being set up on descendant concrete classes as usual.

  See also

  Improvements to declarative mixins, @declared_attr and related features

  References: #2670

### examples

- [examples] [feature]

  Added a new example illustrating materialized paths, using the latest relationship features. Example courtesy Jack Zhou.

  This change is also backported to: 0.9.5

- [examples] [feature]

  A new suite of examples dedicated to providing a detailed study into performance of SQLAlchemy ORM and Core, as well as the DBAPI, from multiple perspectives. The suite runs within a container that provides built in profiling displays both through console output as well as graphically via the RunSnake tool.

  See also

  Performance

- [examples] [bug]

  Updated the Versioning with a History Table example such that mapped columns are re-mapped to match column names as well as grouping of columns; in particular, this allows columns that are explicitly grouped in a same-column-named joined inheritance scenario to be mapped in the same way in the history mappings, avoiding warnings added in the 0.9 series regarding this pattern and allowing the same view of attribute keys.

  This change is also backported to: 0.9.9

- [examples] [bug]

  Fixed a bug in the examples/generic_associations/discriminator_on_association.py example, where the subclasses of AddressAssociation were not being mapped as “single table inheritance”, leading to problems when trying to use the mappings further.

  This change is also backported to: 0.9.9

### engine

- [engine] [feature]

  Added new user-space accessors for viewing transaction isolation levels; `Connection.get_isolation_level()`, `Connection.default_isolation_level`.

  This change is also backported to: 0.9.9

- [engine] [feature]

  Added new event `ConnectionEvents.handle_error()`, a more fully featured and comprehensive replacement for `ConnectionEvents.dbapi_error()`.

  This change is also backported to: 0.9.7

  References: #3076

- [engine] [feature]

  A new style of warning can be emitted which will “filter” up to N occurrences of a parameterized string. This allows parameterized warnings that can refer to their arguments to be delivered a fixed number of times until allowing Python warning filters to squelch them, and prevents memory from growing unbounded within Python’s warning registries.

  See also

  Session.get_bind() handles a wider variety of inheritance scenarios

  References: #3178

- [engine] [bug]

  Fixed bug in `Connection` and pool where the `Connection.invalidate()` method, or an invalidation due to a database disconnect, would fail if the `isolation_level` parameter had been used with `Connection.execution_options()`; the “finalizer” that resets the isolation level would be called on the no longer opened connection.

  This change is also backported to: 0.9.9

  References: #3302

- [engine] [bug]

  A warning is emitted if the `isolation_level` parameter is used with `Connection.execution_options()` when a `Transaction` is in play; DBAPIs and/or SQLAlchemy dialects such as psycopg2, MySQLdb may implicitly rollback or commit the transaction, or not change the setting til next transaction, so this is never safe.

  This change is also backported to: 0.9.9

  References: #3296

- [engine] [bug]

  The execution options passed to an `Engine` either via `create_engine.execution_options` or `Engine.update_execution_options()` are not passed to the special `Connection` used to initialize the dialect within the “first connect” event; dialects will usually perform their own queries in this phase, and none of the current available options should be applied here. In particular, the “autocommit” option was causing an attempt to autocommit within this initial connect which would fail with an AttributeError due to the non-standard state of the `Connection`.

  This change is also backported to: 0.9.8

  References: #3200

- [engine] [bug]

  The string keys that are used to determine the columns impacted for an INSERT or UPDATE are now sorted when they contribute towards the “compiled cache” cache key. These keys were previously not deterministically ordered, meaning the same statement could be cached multiple times on equivalent keys, costing both in terms of memory as well as performance.

  This change is also backported to: 0.9.8

  References: #3165

- [engine] [bug]

  Fixed bug which would occur if a DBAPI exception occurs when the engine first connects and does its initial checks, and the exception is not a disconnect exception, yet the cursor raises an error when we try to close it. In this case the real exception would be quashed as we tried to log the cursor close exception via the connection pool and failed, as we were trying to access the pool’s logger in a way that is inappropriate in this very specific scenario.

  This change is also backported to: 0.9.5

  References: #3063

- [engine] [bug]

  Fixed some “double invalidate” situations were detected where a connection invalidation could occur within an already critical section like a connection.close(); ultimately, these conditions are caused by the change in #2907, in that the “reset on return” feature calls out to the Connection/Transaction in order to handle it, where “disconnect detection” might be caught. However, it’s possible that the more recent change in #2985 made it more likely for this to be seen as the “connection invalidate” operation is much quicker, as the issue is more reproducible on 0.9.4 than 0.9.3.

  Checks are now added within any section that an invalidate might occur to halt further disallowed operations on the invalidated connection. This includes two fixes both at the engine level and at the pool level. While the issue was observed with highly concurrent gevent cases, it could in theory occur in any kind of scenario where a disconnect occurs within the connection close operation.

  This change is also backported to: 0.9.5

  References: #3043

- [engine] [bug]

  The engine-level error handling and wrapping routines will now take effect in all engine connection use cases, including when user-custom connect routines are used via the `create_engine.creator` parameter, as well as when the `Connection` encounters a connection error on revalidation.

  See also

  DBAPI exception wrapping and handle_error() event improvements

  References: #3266

- [engine] [bug]

  Removing (or adding) an event listener at the same time that the event is being run itself, either from inside the listener or from a concurrent thread, now raises a RuntimeError, as the collection used is now an instance of `collections.deque()` and does not support changes while being iterated. Previously, a plain Python list was used where removal from inside the event itself would produce silent failures.

  References: #3163

### sql

- [sql] [feature]

  Liberalized the contract for `Index` a bit in that you can specify a `text()` expression as the target; the index no longer needs to have a table-bound column present if the index is to be manually added to the table, either via inline declaration or via `Table.append_constraint()`.

  This change is also backported to: 0.9.5

  References: #3028

- [sql] [feature]

  Added new flag `between.symmetric`, when set to True renders “BETWEEN SYMMETRIC”. Also added a new negation operator “notbetween_op”, which now allows an expression like `~col.between(x, y)` to render as “col NOT BETWEEN x AND y”, rather than a parenthesized NOT string.

  This change is also backported to: 0.9.5

  References: #2990

- [sql] [feature]

  The SQL compiler now generates the mapping of expected columns such that they are matched to the received result set positionally, rather than by name. Originally, this was seen as a way to handle cases where we had columns returned with difficult-to-predict names, though in modern use that issue has been overcome by anonymous labeling. In this version, the approach basically reduces function call count per-result by a few dozen calls, or more for larger sets of result columns. The approach still degrades into a modern version of the old approach if any discrepancy in size exists between the compiled set of columns versus what was received, so there’s no issue for partially or fully textual compilation scenarios where these lists might not line up.

  References: #918

- [sql] [feature]

  Literal values within a `DefaultClause`, which is invoked when using the `Column.server_default` parameter, will now be rendered using the “inline” compiler, so that they are rendered as-is, rather than as bound parameters.

  See also

  Column server defaults now render literal values

  References: #3087

- [sql] [feature]

  The type of expression is reported when an object passed to a SQL expression unit can’t be interpreted as a SQL fragment; pull request courtesy Ryan P. Kelly.

- [sql] [feature]

  Added a new parameter `Table.tometadata.name` to the `Table.tometadata()` method. Similar to `Table.tometadata.schema`, this argument causes the newly copied `Table` to take on the new name instead of the existing one. An interesting capability this adds is that of copying a `Table` object to the same `MetaData` target with a new name. Pull request courtesy n.d. parker.

- [sql] [feature]

  Exception messages have been spiffed up a bit. The SQL statement and parameters are not displayed if None, reducing confusion for error messages that weren’t related to a statement. The full module and classname for the DBAPI-level exception is displayed, making it clear that this is a wrapped DBAPI exception. The statement and parameters themselves are bounded within a bracketed sections to better isolate them from the error message and from each other.

  References: #3172

- [sql] [feature]

  `Insert.from_select()` now includes Python and SQL-expression defaults if otherwise unspecified; the limitation where non- server column defaults aren’t included in an INSERT FROM SELECT is now lifted and these expressions are rendered as constants into the SELECT statement.

  See also

  INSERT FROM SELECT now includes Python and SQL-expression defaults

- [sql] [feature]

  The `UniqueConstraint` construct is now included when reflecting a `Table` object, for databases where this is applicable. In order to achieve this with sufficient accuracy, MySQL and PostgreSQL now contain features that correct for the duplication of indexes and unique constraints when reflecting tables, indexes, and constraints. In the case of MySQL, there is not actually a “unique constraint” concept independent of a “unique index”, so for this backend `UniqueConstraint` continues to remain non-present for a reflected `Table`. For PostgreSQL, the query used to detect indexes against `pg_index` has been improved to check for the same construct in `pg_constraint`, and the implicitly constructed unique index is not included with a reflected `Table`.

  In both cases, the `Inspector.get_indexes()` and the `Inspector.get_unique_constraints()` methods return both constructs individually, but include a new token `duplicates_constraint` in the case of PostgreSQL or `duplicates_index` in the case of MySQL to indicate when this condition is detected. Pull request courtesy Johannes Erdfelt.

  See also

  UniqueConstraint is now part of the Table reflection process

  References: #3184

- [sql] [feature]

  Added new method `Select.with_statement_hint()` and ORM method `Query.with_statement_hint()` to support statement-level hints that are not specific to a table.

  References: #3206

- [sql] [feature]

  The `info` parameter has been added as a constructor argument to all schema constructs including `MetaData`, `Index`, `ForeignKey`, `ForeignKeyConstraint`, `UniqueConstraint`, `PrimaryKeyConstraint`, `CheckConstraint`.

  References: #2963

- [sql] [feature]

  The `Table.autoload_with` flag now implies that `Table.autoload` should be `True`. Pull request courtesy Malik Diarra.

  References: #3027

- [sql] [feature]

  The `Select.limit()` and `Select.offset()` methods now accept any SQL expression, in addition to integer values, as arguments. Typically this is used to allow a bound parameter to be passed, which can be substituted with a value later thus allowing Python-side caching of the SQL query. The implementation here is fully backwards compatible with existing third party dialects, however those dialects which implement special LIMIT/OFFSET systems will need modification in order to take advantage of the new capabilities. Limit and offset also support “literal_binds” mode,

  References: #3034

- [sql] [changed]

  The `column()` and `table()` constructs are now importable from the “from sqlalchemy” namespace, just like every other Core construct.

- [sql] [changed]

  The implicit conversion of strings to `text()` constructs when passed to most builder methods of `select()` as well as `Query` now emits a warning with just the plain string sent. The textual conversion still proceeds normally, however. The only method that accepts a string without a warning are the “label reference” methods like order_by(), group_by(); these functions will now at compile time attempt to resolve a single string argument to a column or label expression present in the selectable; if none is located, the expression still renders, but you get the warning again. The rationale here is that the implicit conversion from string to text is more unexpected than not these days, and it is better that the user send more direction to the Core / ORM when passing a raw string as to what direction should be taken. Core/ORM tutorials have been updated to go more in depth as to how text is handled.

  See also

  Warnings emitted when coercing full SQL fragments into text()

  References: #2992

- [sql] [bug]

  Fixed bug in `Enum` and other `SchemaType` subclasses where direct association of the type with a `MetaData` would lead to a hang when events (like create events) were emitted on the `MetaData`.

  This change is also backported to: 0.9.7, 0.8.7

  References: #3124

- [sql] [bug]

  Fixed a bug within the custom operator plus `TypeEngine.with_variant()` system, whereby using a `TypeDecorator` in conjunction with variant would fail with an MRO error when a comparison operator was used.

  This change is also backported to: 0.9.7, 0.8.7

  References: #3102

- [sql] [bug]

  Fixed bug in INSERT..FROM SELECT construct where selecting from a UNION would wrap the union in an anonymous (e.g. unlabeled) subquery.

  This change is also backported to: 0.9.5, 0.8.7

  References: #3044

- [sql] [bug]

  Fixed bug where `Table.update()` and `Table.delete()` would produce an empty WHERE clause when an empty `and_()` or `or_()` or other blank expression were applied. This is now consistent with that of `select()`.

  This change is also backported to: 0.9.5, 0.8.7

  References: #3045

- [sql] [bug]

  Added the `native_enum` flag to the `__repr__()` output of `Enum`, which is mostly important when using it with Alembic autogenerate. Pull request courtesy Dimitris Theodorou.

  This change is also backported to: 0.9.9

- [sql] [bug]

  Fixed bug where using a `TypeDecorator` that implemented a type that was also a `TypeDecorator` would fail with Python’s “Cannot create a consistent method resolution order (MRO)” error, when any kind of SQL comparison expression were used against an object using this type.

  This change is also backported to: 0.9.9

  References: #3278

- [sql] [bug]

  Fixed issue where the columns from a SELECT embedded in an INSERT, either through the values clause or as a “from select”, would pollute the column types used in the result set produced by the RETURNING clause when columns from both statements shared the same name, leading to potential errors or mis-adaptation when retrieving the returning rows.

  This change is also backported to: 0.9.9

  References: #3248

- [sql] [bug]

  Fixed bug where a fair number of SQL elements within the sql package would fail to `__repr__()` successfully, due to a missing `description` attribute that would then invoke a recursion overflow when an internal AttributeError would then re-invoke `__repr__()`.

  This change is also backported to: 0.9.8

  References: #3195

- [sql] [bug]

  An adjustment to table/index reflection such that if an index reports a column that isn’t found to be present in the table, a warning is emitted and the column is skipped. This can occur for some special system column situations as has been observed with Oracle.

  This change is also backported to: 0.9.8

  References: #3180

- [sql] [bug]

  Fixed bug in CTE where `literal_binds` compiler argument would not be always be correctly propagated when one CTE referred to another aliased CTE in a statement.

  This change is also backported to: 0.9.8

  References: #3154

- [sql] [bug]

  Fixed 0.9.7 regression caused by #3067 in conjunction with a mis-named unit test such that so-called “schema” types like `Boolean` and `Enum` could no longer be pickled.

  This change is also backported to: 0.9.8

  References: #3067, #3144

- [sql] [bug]

  Fix bug in naming convention feature where using a check constraint convention that includes `constraint_name` would then force all `Boolean` and `Enum` types to require names as well, as these implicitly create a constraint, even if the ultimate target backend were one that does not require generation of the constraint such as PostgreSQL. The mechanics of naming conventions for these particular constraints has been reorganized such that the naming determination is done at DDL compile time, rather than at constraint/table construction time.

  This change is also backported to: 0.9.7

  References: #3067

- [sql] [bug]

  Fixed bug in common table expressions whereby positional bound parameters could be expressed in the wrong final order when CTEs were nested in certain ways.

  This change is also backported to: 0.9.7

  References: #3090

- [sql] [bug]

  Fixed bug where multi-valued `Insert` construct would fail to check subsequent values entries beyond the first one given for literal SQL expressions.

  This change is also backported to: 0.9.7

  References: #3069

- [sql] [bug]

  Added a “str()” step to the dialect_kwargs iteration for Python version < 2.6.5, working around the “no unicode keyword arg” bug as these args are passed along as keyword args within some reflection processes.

  This change is also backported to: 0.9.7

  References: #3123

- [sql] [bug]

  The `TypeEngine.with_variant()` method will now accept a type class as an argument which is internally converted to an instance, using the same convention long established by other constructs such as `Column`.

  This change is also backported to: 0.9.7

  References: #3122

- [sql] [bug]

  The `Column.nullable` flag is implicitly set to `False` when that `Column` is referred to in an explicit `PrimaryKeyConstraint` for that table. This behavior now matches that of when the `Column` itself has the `Column.primary_key` flag set to `True`, which is intended to be an exactly equivalent case.

  This change is also backported to: 0.9.5

  References: #3023

- [sql] [bug]

  Fixed bug where the `Operators.__and__()`, `Operators.__or__()` and `Operators.__invert__()` operator overload methods could not be overridden within a custom `Comparator` implementation.

  This change is also backported to: 0.9.5

  References: #3012

- [sql] [bug]

  Fixed bug in new `DialectKWArgs.argument_for()` method where adding an argument for a construct not previously included for any special arguments would fail.

  This change is also backported to: 0.9.5

  References: #3024

- [sql] [bug]

  Fixed regression introduced in 0.9 where new “ORDER BY <labelname>” feature from #1068 would not apply quoting rules to the label name as rendered in the ORDER BY.

  This change is also backported to: 0.9.5

  References: #1068, #3020

- [sql] [bug]

  Restored the import for `Function` to the `sqlalchemy.sql.expression` import namespace, which was removed at the beginning of 0.9.

  This change is also backported to: 0.9.5

- [sql] [bug]

  The multi-values version of `Insert.values()` has been repaired to work more usefully with tables that have Python- side default values and/or functions, as well as server-side defaults. The feature will now work with a dialect that uses “positional” parameters; a Python callable will also be invoked individually for each row just as is the case with an “executemany” style invocation; a server- side default column will no longer implicitly receive the value explicitly specified for the first row, instead refusing to invoke without an explicit value.

  See also

  Python-side defaults invoked for each row individually when using a multivalued insert

  References: #3288

- [sql] [bug]

  Fixed bug in `Table.tometadata()` method where the `CheckConstraint` associated with a `Boolean` or `Enum` type object would be doubled in the target table. The copy process now tracks the production of this constraint object as local to a type object.

  References: #3260

- [sql] [bug]

  The behavioral contract of the `ForeignKeyConstraint.columns` collection has been made consistent; this attribute is now a `ColumnCollection` like that of all other constraints and is initialized at the point when the constraint is associated with a `Table`.

  See also

  ForeignKeyConstraint.columns is now a ColumnCollection

  References: #3243

- [sql] [bug]

  The `Column.key` attribute is now used as the source of anonymous bound parameter names within expressions, to match the existing use of this value as the key when rendered in an INSERT or UPDATE statement. This allows `Column.key` to be used as a “substitute” string to work around a difficult column name that doesn’t translate well into a bound parameter name. Note that the paramstyle is configurable on `create_engine()` in any case, and most DBAPIs today support a named and positional style.

  References: #3245

- [sql] [bug]

  Fixed the name of the `PoolEvents.reset.dbapi_connection` parameter as passed to this event; in particular this affects usage of the “named” argument style for this event. Pull request courtesy Jason Goldberger.

- [sql] [bug]

  Reversing a change that was made in 0.9, the “singleton” nature of the “constants” `null()`, `true()`, and `false()` has been reverted. These functions returning a “singleton” object had the effect that different instances would be treated as the same regardless of lexical use, which in particular would impact the rendering of the columns clause of a SELECT statement.

  See also

  null(), false() and true() constants are no longer singletons

  References: #3170

- [sql] [bug] [engine]

  Fixed bug where a “branched” connection, that is the kind you get when you call `Connection.connect()`, would not share invalidation status with the parent. The architecture of branching has been tweaked a bit so that the branched connection defers to the parent for all invalidation status and operations.

  References: #3215

- [sql] [bug] [engine]

  Fixed bug where a “branched” connection, that is the kind you get when you call `Connection.connect()`, would not share transaction status with the parent. The architecture of branching has been tweaked a bit so that the branched connection defers to the parent for all transactional status and operations.

  References: #3190

- [sql] [bug]

  Using `Insert.from_select()` now implies `inline=True` on `insert()`. This helps to fix a bug where an INSERT…FROM SELECT construct would inadvertently be compiled as “implicit returning” on supporting backends, which would cause breakage in the case of an INSERT that inserts zero rows (as implicit returning expects a row), as well as arbitrary return data in the case of an INSERT that inserts multiple rows (e.g. only the first row of many). A similar change is also applied to an INSERT..VALUES with multiple parameter sets; implicit RETURNING will no longer emit for this statement either. As both of these constructs deal with variable numbers of rows, the `ResultProxy.inserted_primary_key` accessor does not apply. Previously, there was a documentation note that one may prefer `inline=True` with INSERT..FROM SELECT as some databases don’t support returning and therefore can’t do “implicit” returning, but there’s no reason an INSERT…FROM SELECT needs implicit returning in any case. Regular explicit `Insert.returning()` should be used to return variable numbers of result rows if inserted data is needed.

  References: #3169

- [sql] [enhancement]

  Custom dialects that implement `GenericTypeCompiler` can now be constructed such that the visit methods receive an indication of the owning expression object, if any. Any visit method that accepts keyword arguments (e.g. `**kw`) will in most cases receive a keyword argument `type_expression`, referring to the expression object that the type is contained within. For columns in DDL, the dialect’s compiler class may need to alter its `get_column_specification()` method to support this as well. The `UserDefinedType.get_col_spec()` method will also receive `type_expression` if it provides `**kw` in its argument signature.

  References: #3074

### schema

- [schema] [feature]

  The DDL generation system of `MetaData.create_all()` and `MetaData.drop_all()` has been enhanced to in most cases automatically handle the case of mutually dependent foreign key constraints; the need for the `ForeignKeyConstraint.use_alter` flag is greatly reduced. The system also works for constraints which aren’t given a name up front; only in the case of DROP is a name required for at least one of the constraints involved in the cycle.

  See also

  The use_alter flag on ForeignKeyConstraint is (usually) no longer needed

  References: #3282

- [schema] [feature]

  Added a new accessor `Table.foreign_key_constraints` to complement the `Table.foreign_keys` collection, as well as `ForeignKeyConstraint.referred_table`.

- [schema] [bug]

  The `CheckConstraint` construct now supports naming conventions that include the token `%(column_0_name)s`; the constraint expression is scanned for columns. Additionally, naming conventions for check constraints that don’t include the `%(constraint_name)s` token will now work for `SchemaType`- generated constraints, such as those of `Boolean` and `Enum`; this stopped working in 0.9.7 due to #3067.

  See also

  Naming CHECK Constraints

  Configuring Naming for Boolean, Enum, and other schema types

  References: #3067, #3299

### postgresql

- [postgresql] [feature]

  Added support for the `CONCURRENTLY` keyword with PostgreSQL indexes, established using `postgresql_concurrently`. Pull request courtesy Iuri de Silvio.

  See also

  Indexes with CONCURRENTLY

  This change is also backported to: 0.9.9

- [postgresql] [feature] [pg8000]

  Support is added for “sane multi row count” with the pg8000 driver, which applies mostly to when using versioning with the ORM. The feature is version-detected based on pg8000 1.9.14 or greater in use. Pull request courtesy Tony Locke.

  This change is also backported to: 0.9.8

- [postgresql] [feature]

  Added kw argument `postgresql_regconfig` to the `ColumnOperators.match()` operator, allows the “reg config” argument to be specified to the `to_tsquery()` function emitted. Pull request courtesy Jonathan Vanasco.

  This change is also backported to: 0.9.7

  References: #3078

- [postgresql] [feature]

  Added support for PostgreSQL JSONB via `JSONB`. Pull request courtesy Damian Dimmich.

  This change is also backported to: 0.9.7

- [postgresql] [feature]

  Added support for AUTOCOMMIT isolation level when using the pg8000 DBAPI. Pull request courtesy Tony Locke.

  This change is also backported to: 0.9.5

- [postgresql] [feature]

  Added a new flag `ARRAY.zero_indexes` to the PostgreSQL `ARRAY` type. When set to `True`, a value of one will be added to all array index values before passing to the database, allowing better interoperability between Python style zero-based indexes and PostgreSQL one-based indexes. Pull request courtesy Alexey Terentev.

  This change is also backported to: 0.9.5

  References: #2785

- [postgresql] [feature]

  The PG8000 dialect now supports the `create_engine.encoding` parameter, by setting up the client encoding on the connection which is then intercepted by pg8000. Pull request courtesy Tony Locke.

- [postgresql] [feature]

  Added support for PG8000’s native JSONB feature. Pull request courtesy Tony Locke.

- [postgresql] [feature] [pypy]

  Added support for the psycopg2cffi DBAPI on pypy. Pull request courtesy shauns.

  See also

  `sqlalchemy.dialects.postgresql.psycopg2cffi`

  References: #3052

- [postgresql] [feature]

  Added support for the FILTER keyword as applied to aggregate functions, supported by PostgreSQL 9.4. Pull request courtesy Ilja Everilä.

  See also

  PostgreSQL FILTER keyword

- [postgresql] [feature]

  Support has been added for reflection of materialized views and foreign tables, as well as support for materialized views within `Inspector.get_view_names()`, and a new method `PGInspector.get_foreign_table_names()` available on the PostgreSQL version of `Inspector`. Pull request courtesy Rodrigo Menezes.

  See also

  PostgreSQL Dialect reflects Materialized Views, Foreign Tables

  References: #2891

- [postgresql] [feature]

  Added support for PG table options TABLESPACE, ON COMMIT, WITH(OUT) OIDS, and INHERITS, when rendering DDL via the `Table` construct. Pull request courtesy malikdiarra.

  See also

  PostgreSQL Table Options

  References: #2051

- [postgresql] [feature]

  Added new method `PGInspector.get_enums()`, when using the inspector for PostgreSQL will provide a list of ENUM types. Pull request courtesy Ilya Pekelny.

- [postgresql] [bug]

  Added the `hashable=False` flag to the PG `HSTORE` type, which is needed to allow the ORM to skip over trying to “hash” an ORM-mapped HSTORE column when requesting it in a mixed column/entity list. Patch courtesy Gunnlaugur Þór Briem.

  This change is also backported to: 0.9.5, 0.8.7

  References: #3053

- [postgresql] [bug]

  Added a new “disconnect” message “connection has been closed unexpectedly”. This appears to be related to newer versions of SSL. Pull request courtesy Antti Haapala.

  This change is also backported to: 0.9.5, 0.8.7

- [postgresql] [bug]

  Repaired support for PostgreSQL UUID types in conjunction with the ARRAY type when using psycopg2. The psycopg2 dialect now employs use of the psycopg2.extras.register_uuid() hook so that UUID values are always passed to/from the DBAPI as UUID() objects. The `UUID.as_uuid` flag is still honored, except with psycopg2 we need to convert returned UUID objects back into strings when this is disabled.

  This change is also backported to: 0.9.9

  References: #2940

- [postgresql] [bug]

  Added support for the `postgresql.JSONB` datatype when using psycopg2 2.5.4 or greater, which features native conversion of JSONB data so that SQLAlchemy’s converters must be disabled; additionally, the newly added psycopg2 extension `extras.register_default_jsonb` is used to establish a JSON deserializer passed to the dialect via the `json_deserializer` argument. Also repaired the PostgreSQL integration tests which weren’t actually round-tripping the JSONB type as opposed to the JSON type. Pull request courtesy Mateusz Susik.

  This change is also backported to: 0.9.9

- [postgresql] [bug]

  Repaired the use of the “array_oid” flag when registering the HSTORE type with older psycopg2 versions < 2.4.3, which does not support this flag, as well as use of the native json serializer hook “register_default_json” with user-defined `json_deserializer` on psycopg2 versions < 2.5, which does not include native json.

  This change is also backported to: 0.9.9

- [postgresql] [bug]

  Fixed bug where PostgreSQL dialect would fail to render an expression in an `Index` that did not correspond directly to a table-bound column; typically when a `text()` construct was one of the expressions within the index; or could misinterpret the list of expressions if one or more of them were such an expression.

  This change is also backported to: 0.9.9

  References: #3174

- [postgresql] [bug]

  A revisit to this issue first patched in 0.9.5, apparently psycopg2’s `.closed` accessor is not as reliable as we assumed, so we have added an explicit check for the exception messages “SSL SYSCALL error: Bad file descriptor” and “SSL SYSCALL error: EOF detected” when detecting an is-disconnect scenario. We will continue to consult psycopg2’s connection.closed as a first check.

  This change is also backported to: 0.9.8

  References: #3021

- [postgresql] [bug]

  Fixed bug where PostgreSQL JSON type was not able to persist or otherwise render a SQL NULL column value, rather than a JSON-encoded `'null'`. To support this case, changes are as follows:

  - The value `null()` can now be specified, which will always result in a NULL value resulting in the statement.

  - A new parameter `JSON.none_as_null` is added, which when True indicates that the Python `None` value should be persisted as SQL NULL, rather than JSON-encoded `'null'`.

  Retrieval of NULL as None is also repaired for DBAPIs other than psycopg2, namely pg8000.

  This change is also backported to: 0.9.8

  References: #3159

- [postgresql] [bug]

  The exception wrapping system for DBAPI errors can now accommodate non-standard DBAPI exceptions, such as the psycopg2 TransactionRollbackError. These exceptions will now be raised using the closest available subclass in `sqlalchemy.exc`, in the case of TransactionRollbackError, `sqlalchemy.exc.OperationalError`.

  This change is also backported to: 0.9.8

  References: #3075

- [postgresql] [bug]

  Fixed bug in `array` object where comparison to a plain Python list would fail to use the correct array constructor. Pull request courtesy Andrew.

  This change is also backported to: 0.9.8

  References: #3141

- [postgresql] [bug]

  Added a supported `FunctionElement.alias()` method to functions, e.g. the `func` construct. Previously, behavior for this method was undefined. The current behavior mimics that of pre-0.9.4, which is that the function is turned into a single-column FROM clause with the given alias name, where the column itself is anonymously named.

  This change is also backported to: 0.9.8

  References: #3137

- [postgresql] [bug] [pg8000]

  Fixed bug introduced in 0.9.5 by new pg8000 isolation level feature where engine-level isolation level parameter would raise an error on connect.

  This change is also backported to: 0.9.7

  References: #3134

- [postgresql] [bug]

  The psycopg2 `.closed` accessor is now consulted when determining if an exception is a “disconnect” error; ideally, this should remove the need for any other inspection of the exception message to detect disconnect, however we will leave those existing messages in place as a fallback. This should be able to handle newer cases like “SSL EOF” conditions. Pull request courtesy Dirk Mueller.

  This change is also backported to: 0.9.5

  References: #3021

- [postgresql] [bug]

  The PostgreSQL `ENUM` type will emit a DROP TYPE instruction when a plain `table.drop()` is called, assuming the object is not associated directly with a `MetaData` object. In order to accommodate the use case of an enumerated type shared between multiple tables, the type should be associated directly with the `MetaData` object; in this case the type will only be created at the metadata level, or if created directly. The rules for create/drop of PostgreSQL enumerated types have been highly reworked in general.

  See also

  Overhaul of ENUM type create/drop rules

  References: #3319

- [postgresql] [bug]

  The `PGDialect.has_table()` method will now query against `pg_catalog.pg_table_is_visible(c.oid)`, rather than testing for an exact schema match, when the schema name is None; this so that the method will also illustrate that temporary tables are present. Note that this is a behavioral change, as PostgreSQL allows a non-temporary table to silently overwrite an existing temporary table of the same name, so this changes the behavior of `checkfirst` in that unusual scenario.

  See also

  PostgreSQL has_table() now works for temporary tables

  References: #3264

- [postgresql] [enhancement]

  Added a new type `OID` to the PostgreSQL dialect. While “oid” is generally a private type within PG that is not exposed in modern versions, there are some PG use cases such as large object support where these types might be exposed, as well as within some user-reported schema reflection use cases.

  This change is also backported to: 0.9.5

  References: #3002

### mysql

- [mysql] [feature]

  The MySQL dialect now renders TIMESTAMP with NULL / NOT NULL in all cases, so that MySQL 5.6.6 with the `explicit_defaults_for_timestamp` flag enabled will will allow TIMESTAMP to continue to work as expected when `nullable=False`. Existing applications are unaffected as SQLAlchemy has always emitted NULL for a TIMESTAMP column that is `nullable=True`.

  See also

  MySQL TIMESTAMP Type now renders NULL / NOT NULL in all cases

  TIMESTAMP Columns and NULL

  References: #3155

- [mysql] [feature]

  Updated the “supports_unicode_statements” flag to True for MySQLdb and Pymysql under Python 2. This refers to the SQL statements themselves, not the parameters, and affects issues such as table and column names using non-ASCII characters. These drivers both appear to support Python 2 Unicode objects without issue in modern versions.

  References: #3121

- [mysql] [change]

  The `gaerdbms` dialect is no longer necessary, and emits a deprecation warning. Google now recommends using the MySQLdb dialect directly.

  This change is also backported to: 0.9.9

  References: #3275

- [mysql] [bug]

  MySQL error 2014 “commands out of sync” appears to be raised as a ProgrammingError, not OperationalError, in modern MySQL-Python versions; all MySQL error codes that are tested for “is disconnect” are now checked within OperationalError and ProgrammingError regardless.

  This change is also backported to: 0.9.7, 0.8.7

  References: #3101

- [mysql] [bug]

  Fixed bug where column names added to `mysql_length` parameter on an index needed to have the same quoting for quoted names in order to be recognized. The fix makes the quotes optional but also provides the old behavior for backwards compatibility with those using the workaround.

  This change is also backported to: 0.9.5, 0.8.7

  References: #3085

- [mysql] [bug]

  Added support for reflecting tables where an index includes KEY_BLOCK_SIZE using an equal sign. Pull request courtesy Sean McGivern.

  This change is also backported to: 0.9.5, 0.8.7

- [mysql] [bug]

  Added a version check to the MySQLdb dialect surrounding the check for ‘utf8_bin’ collation, as this fails on MySQL server < 5.0.

  This change is also backported to: 0.9.9

  References: #3274

- [mysql] [bug] [mysqlconnector]

  Mysqlconnector as of version 2.0, probably as a side effect of the python 3 merge, now does not expect percent signs (e.g. as used as the modulus operator and others) to be doubled, even when using the “pyformat” bound parameter format (this change is not documented by Mysqlconnector). The dialect now checks for py2k and for mysqlconnector less than version 2.0 when detecting if the modulus operator should be rendered as `%%` or `%`.

  This change is also backported to: 0.9.8

- [mysql] [bug] [mysqlconnector]

  Unicode SQL is now passed for MySQLconnector version 2.0 and above; for Py2k and MySQL < 2.0, strings are encoded.

  This change is also backported to: 0.9.8

- [mysql] [bug]

  The MySQL dialect now supports CAST on types that are constructed as `TypeDecorator` objects.

- [mysql] [bug]

  A warning is emitted when `cast()` is used with the MySQL dialect on a type where MySQL does not support CAST; MySQL only supports CAST on a subset of datatypes. SQLAlchemy has for a long time just omitted the CAST for unsupported types in the case of MySQL. While we don’t want to change this now, we emit a warning to show that it’s taken place. A warning is also emitted when a CAST is used with an older MySQL version (< 4) that doesn’t support CAST at all, it’s skipped in this case as well.

  References: #3237

- [mysql] [bug]

  The `SET` type has been overhauled to no longer assume that the empty string, or a set with a single empty string value, is in fact a set with a single empty string; instead, this is by default treated as the empty set. In order to handle persistence of a `SET` that actually wants to include the blank value `''` as a legitimate value, a new bitwise operational mode is added which is enabled by the `SET.retrieve_as_bitwise` flag, which will persist and retrieve values unambiguously using their bitflag positioning. Storage and retrieval of unicode values for driver configurations that aren’t converting unicode natively is also repaired.

  See also

  MySQL SET Type Overhauled to support empty sets, unicode, blank value handling

  References: #3283

- [mysql] [bug]

  The `ColumnOperators.match()` operator is now handled such that the return type is not strictly assumed to be boolean; it now returns a `Boolean` subclass called `MatchType`. The type will still produce boolean behavior when used in Python expressions, however the dialect can override its behavior at result time. In the case of MySQL, while the MATCH operator is typically used in a boolean context within an expression, if one actually queries for the value of a match expression, a floating point value is returned; this value is not compatible with SQLAlchemy’s C-based boolean processor, so MySQL’s result-set behavior now follows that of the `Float` type. A new operator object `notmatch_op` is also added to better allow dialects to define the negation of a match operation.

  See also

  The match() operator now returns an agnostic MatchType compatible with MySQL’s floating point return value

  References: #3263

- [mysql] [bug]

  MySQL boolean symbols “true”, “false” work again. 0.9’s change in #2682 disallowed the MySQL dialect from making use of the “true” and “false” symbols in the context of “IS” / “IS NOT”, but MySQL supports this syntax even though it has no boolean type. MySQL remains “non native boolean”, but the `true()` and `false()` symbols again produce the keywords “true” and “false”, so that an expression like `column.is_(true())` again works on MySQL.

  See also

  MySQL boolean symbols “true”, “false” work again

  References: #3186

- [mysql] [bug]

  The MySQL dialect will now disable `ConnectionEvents.handle_error()` events from firing for those statements which it uses internally to detect if a table exists or not. This is achieved using an execution option `skip_user_error_events` that disables the handle error event for the scope of that execution. In this way, user code that rewrites exceptions doesn’t need to worry about the MySQL dialect or other dialects that occasionally need to catch SQLAlchemy specific exceptions.

- [mysql] [bug]

  Changed the default value of “raise_on_warnings” to False for MySQLconnector. This was set at True for some reason. The “buffered” flag unfortunately must stay at True as MySQLconnector does not allow a cursor to be closed unless all results are fully fetched.

  References: #2515

### sqlite

- [sqlite] [feature]

  Added support for partial indexes (e.g. with a WHERE clause) on SQLite. Pull request courtesy Kai Groner.

  See also

  Partial Indexes

  This change is also backported to: 0.9.9

- [sqlite] [feature]

  Added a new SQLite backend for the SQLCipher backend. This backend provides for encrypted SQLite databases using the pysqlcipher Python driver, which is very similar to the pysqlite driver.

  See also

  `pysqlcipher`

  This change is also backported to: 0.9.9

- [sqlite] [bug]

  When selecting from a UNION using an attached database file, the pysqlite driver reports column names in cursor.description as ‘dbname.tablename.colname’, instead of ‘tablename.colname’ as it normally does for a UNION (note that it’s supposed to just be ‘colname’ for both, but we work around it). The column translation logic here has been adjusted to retrieve the rightmost token, rather than the second token, so it works in both cases. Workaround courtesy Tony Roberts.

  This change is also backported to: 0.9.8

  References: #3211

- [sqlite] [bug]

  Fixed a SQLite join rewriting issue where a subquery that is embedded as a scalar subquery such as within an IN would receive inappropriate substitutions from the enclosing query, if the same table were present inside the subquery as were in the enclosing query such as in a joined inheritance scenario.

  This change is also backported to: 0.9.7

  References: #3130

- [sqlite] [bug]

  UNIQUE and FOREIGN KEY constraints are now fully reflected on SQLite both with and without names. Previously, foreign key names were ignored and unnamed unique constraints were skipped. Thanks to Jon Nelson for assistance with this.

  References: #3244, #3261

- [sqlite] [bug]

  The SQLite dialect, when using the `DATE`, `TIME`, or `DATETIME` types, and given a `storage_format` that only renders numbers, will render the types in DDL as `DATE_CHAR`, `TIME_CHAR`, and `DATETIME_CHAR`, so that despite the lack of alpha characters in the values, the column will still deliver the “text affinity”. Normally this is not needed, as the textual values within the default storage formats already imply text.

  See also

  Date and Time Types

  References: #3257

- [sqlite] [bug]

  SQLite now supports reflection of unique constraints from temp tables; previously, this would fail with a TypeError. Pull request courtesy Johannes Erdfelt.

  See also

  SQLite/Oracle have distinct methods for temporary table/view name reporting - changes regarding SQLite temporary table and view reflection.

  References: #3203

- [sqlite] [bug]

  Added `Inspector.get_temp_table_names()` and `Inspector.get_temp_view_names()`; currently, only the SQLite and Oracle dialects support these methods. The return of temporary table and view names has been removed from SQLite and Oracle’s version of `Inspector.get_table_names()` and `Inspector.get_view_names()`; other database backends cannot support this information (such as MySQL), and the scope of operation is different in that the tables can be local to a session and typically aren’t supported in remote schemas.

  See also

  SQLite/Oracle have distinct methods for temporary table/view name reporting

  References: #3204

### mssql

- [mssql] [feature]

  Enabled “multivalues insert” for SQL Server 2008. Pull request courtesy Albert Cervin. Also expanded the checks for “IDENTITY INSERT” mode to include when the identity key is present in the VALUEs clause of the statement.

  This change is also backported to: 0.9.7

- [mssql] [feature]

  SQL Server 2012 now recommends VARCHAR(max), NVARCHAR(max), VARBINARY(max) for large text/binary types. The MSSQL dialect will now respect this based on version detection, as well as the new `deprecate_large_types` flag.

  See also

  Large Text/Binary Type Deprecation

  References: #3039

- [mssql] [changed]

  The hostname-based connection format for SQL Server when using pyodbc will no longer specify a default “driver name”, and a warning is emitted if this is missing. The optimal driver name for SQL Server changes frequently and is per-platform, so hostname based connections need to specify this. DSN-based connections are preferred.

  See also

  PyODBC driver name is required with hostname-based SQL Server connections

  References: #3182

- [mssql] [bug]

  Added statement encoding to the “SET IDENTITY_INSERT” statements which operate when an explicit INSERT is being interjected into an IDENTITY column, to support non-ascii table identifiers on drivers such as pyodbc + unix + py2k that don’t support unicode statements.

  This change is also backported to: 0.9.7, 0.8.7

- [mssql] [bug]

  In the SQL Server pyodbc dialect, repaired the implementation for the `description_encoding` dialect parameter, which when not explicitly set was preventing cursor.description from being parsed correctly in the case of result sets that contained names in alternate encodings. This parameter shouldn’t be needed going forward.

  This change is also backported to: 0.9.7, 0.8.7

  References: #3091

- [mssql] [bug]

  Fixed the version string detection in the pymssql dialect to work with Microsoft SQL Azure, which changes the word “SQL Server” to “SQL Azure”.

  This change is also backported to: 0.9.8

  References: #3151

- [mssql] [bug]

  Revised the query used to determine the current default schema name to use the `database_principal_id()` function in conjunction with the `sys.database_principals` view so that we can determine the default schema independently of the type of login in progress (e.g., SQL Server, Windows, etc).

  This change is also backported to: 0.9.5

  References: #3025

### oracle

- [oracle] [feature]

  Added support for cx_oracle connections to a specific service name, as opposed to a tns name, by passing `?service_name=<name>` to the URL. Pull request courtesy Sławomir Ehlert.

- [oracle] [feature]

  New Oracle DDL features for tables, indexes: COMPRESS, BITMAP. Patch courtesy Gabor Gombas.

- [oracle] [feature]

  Added support for CTEs under Oracle. This includes some tweaks to the aliasing syntax, as well as a new CTE feature `CTE.suffix_with()`, which is useful for adding in special Oracle-specific directives to the CTE.

  See also

  Improved support for CTEs in Oracle

  References: #3220

- [oracle] [feature]

  Added support for the Oracle table option ON COMMIT.

- [oracle] [bug]

  Fixed long-standing bug in Oracle dialect where bound parameter names that started with numbers would not be quoted, as Oracle doesn’t like numerics in bound parameter names.

  This change is also backported to: 0.9.8

  References: #2138

- [oracle] [bug] [tests]

  Fixed bug in oracle dialect test suite where in one test, ‘username’ was assumed to be in the database URL, even though this might not be the case.

  This change is also backported to: 0.9.7

  References: #3128

- [oracle] [bug]

  An alias name will be properly quoted when referred to using the `%(name)s` token inside the `Select.with_hint()` method. Previously, the Oracle backend hadn’t implemented this quoting.

### tests

- [tests] [bug]

  Fixed bug where “python setup.py test” wasn’t calling into distutils appropriately, and errors would be emitted at the end of the test suite.

  This change is also backported to: 0.9.7

- [tests] [bug] [py3k]

  Corrected for some deprecation warnings involving the `imp` module and Python 3.3 or greater, when running tests. Pull request courtesy Matt Chisholm.

  This change is also backported to: 0.9.5

  References: #2830

### misc

- [feature] [ext]

  Added a new extension suite `sqlalchemy.ext.baked`. This simple but unusual system allows for a dramatic savings in Python overhead for the construction and processing of orm `Query` objects, from query construction up through rendering of a string SQL statement.

  See also

  Baked Queries

  References: #3054

- [feature] [ext]

  The `sqlalchemy.ext.automap` extension will now set `cascade="all, delete-orphan"` automatically on a one-to-many relationship/backref where the foreign key is detected as containing one or more non-nullable columns. This argument is present in the keywords passed to `generate_relationship()` in this case and can still be overridden. Additionally, if the `ForeignKeyConstraint` specifies `ondelete="CASCADE"` for a non-nullable or `ondelete="SET NULL"` for a nullable set of columns, the argument `passive_deletes=True` is also added to the relationship. Note that not all backends support reflection of ondelete, but backends that do include PostgreSQL and MySQL.

  References: #3210

- [bug] [declarative]

  The `__mapper_args__` dictionary is copied from a declarative mixin or abstract class when accessed, so that modifications made to this dictionary by declarative itself won’t conflict with that of other mappings. The dictionary is modified regarding the `version_id_col` and `polymorphic_on` arguments, replacing the column within with the one that is officially mapped to the local class/table.

  This change is also backported to: 0.9.5, 0.8.7

  References: #3062

- [bug] [ext]

  Fixed bug in mutable extension where `MutableDict` did not report change events for the `setdefault()` dictionary operation.

  This change is also backported to: 0.9.5, 0.8.7

  References: #3051, #3093

- [bug] [ext]

  Fixed bug where `MutableDict.setdefault()` didn’t return the existing or new value (this bug was not released in any 0.8 version). Pull request courtesy Thomas Hervé.

  This change is also backported to: 0.9.5, 0.8.7

  References: #3051, #3093

- [bug] [ext] [py3k]

  Fixed bug where the association proxy list class would not interpret slices correctly under Py3K. Pull request courtesy Gilles Dartiguelongue.

  This change is also backported to: 0.9.9

- [bug] [declarative]

  Fixed an unlikely race condition observed in some exotic end-user setups, where the attempt to check for “duplicate class name” in declarative would hit upon a not-totally-cleaned-up weak reference related to some other class being removed; the check here now ensures the weakref still references an object before calling upon it further.

  This change is also backported to: 0.9.8

  References: #3208

- [bug] [ext]

  Fixed bug in ordering list where the order of items would be thrown off during a collection replace event, if the reorder_on_append flag were set to True. The fix ensures that the ordering list only impacts the list that is explicitly associated with the object.

  This change is also backported to: 0.9.8

  References: #3191

- [bug] [ext]

  Fixed bug where `MutableDict` failed to implement the `update()` dictionary method, thus not catching changes. Pull request courtesy Matt Chisholm.

  This change is also backported to: 0.9.8

- [bug] [ext]

  Fixed bug where a custom subclass of `MutableDict` would not show up in a “coerce” operation, and would instead return a plain `MutableDict`. Pull request courtesy Matt Chisholm.

  This change is also backported to: 0.9.8

- [bug] [pool]

  Fixed bug in connection pool logging where the “connection checked out” debug logging message would not emit if the logging were set up using `logging.setLevel()`, rather than using the `echo_pool` flag. Tests to assert this logging have been added. This is a regression that was introduced in 0.9.0.

  This change is also backported to: 0.9.8

  References: #3168

- [bug] [declarative]

  Fixed bug when the declarative `__abstract__` flag was not being distinguished for when it was actually the value `False`. The `__abstract__` flag needs to actually evaluate to a True value at the level being tested.

  This change is also backported to: 0.9.7

  References: #3097

- [bug] [testsuite]

  In public test suite, changed to use of `String(40)` from less-supported `Text` in `StringTest.test_literal_backslashes`. Pullreq courtesy Jan.

  This change is also backported to: 0.9.5

- [removed]

  The Drizzle dialect has been removed from the Core; it is now available as sqlalchemy-drizzle, an independent, third party dialect. The dialect is still based almost entirely off of the MySQL dialect present in SQLAlchemy.

  See also

  Drizzle Dialect is now an External Dialect