Release: 1.3.0b1 pre release | Release Date: unreleased

# 0.9 Changelog¶

## 0.9.10¶

Released: July 22, 2015

### 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.

References: #3320

• [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, a warning is emitted. As of 1.0.0b5 this will raise an error.

References: #3349

• [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.

References: #3352

### 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.

References: #3418

• [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.

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 postgresql.ENUM type used to be a standalone type without a “non native” option.

References: #3354

### 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.

References: #3337

• [mysql] [bug] [py3k] Fixed the mysql.BIT type on Py3K which was not using the ord() function correctly. Pull request courtesy David Marin.

References: #3333, pull request github:158

### 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.

References: #3495

### 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 referencable, such as an integer.

References: #3408

• [bug] [pypy] [tests] Fixed an import that prevented “pypy setup.py test” from working correctly.

References: #3406

• [bug] [ext] Fixed regression from 0.9.9 where the as_declarative() symbol was removed from the sqlalchemy.ext.declarative namespace.

References: #3324

## 0.9.9¶

Released: March 10, 2015

### orm¶

• [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.

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

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.

• [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.

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.

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.

References: pull request github:147

• [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.

References: #3300

• [orm] [bug] The “wildcard” loader options, in particular the one set up by the orm.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.

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.

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.

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.

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.

References: #3232

### sql¶

• [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.

References: pull request bitbucket:41

• [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.

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.

References: #3248

### schema¶

• [schema] [bug] Fixed bug in 0.9’s foreign key setup system, such that the logic used to link a ForeignKey to its parent could fail when the foreign key used “link_to_name=True” in conjunction with a target Table that would not receive its parent column until later, such as within a reflection + “useexisting” scenario, if the target column in fact had a key value different from its name, as would occur in reflection if column reflect events were used to alter the .key of reflected Column objects so that the link_to_name becomes significant. Also repaired support for column type via FK transmission in a similar way when target columns had a different key and were referenced using link_to_name.

References: #1765, #3298

### postgresql¶

• [postgresql] [feature] Added support for the CONCURRENTLY keyword with PostgreSQL indexes, established using postgresql_concurrently. Pull request courtesy Iuri de Silvio.

References: pull request bitbucket:45

• [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.

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.

References: pull request github:145

• [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.

• [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.

References: #3174

### mysql¶

• [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.

References: #3274

• [mysql] [change] The gaerdbms dialect is no longer necessary, and emits a deprecation warning. Google now recommends using the MySQLdb dialect directly.

References: #3275

### sqlite¶

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

Partial Indexes

References: pull request bitbucket:42

• [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.

### misc¶

• [bug] [ext] [py3k] Fixed bug where the association proxy list class would not interpret slices correctly under Py3K. Pull request courtesy Gilles Dartiguelongue.

References: pull request github:154

• [bug] [examples] 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.

• [bug] [examples] Fixed a bug in the examples/generic_assocaitions/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.

## 0.9.8¶

Released: October 13, 2014

### orm¶

• [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.

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 event.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.

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.

References: #3194

### orm declarative¶

• [bug] [declarative] [orm] Fixed “‘NoneType’ object has no attribute ‘concrete’” error when using AbstractConcreteBase in conjunction with a subclass that declares __abstract__.

References: #3185

### engine¶

• [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.

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.

References: #3165

### sql¶

• [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__().

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.

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.

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.

References: #3067, #3144

### postgresql¶

• [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.

References: pull request github:125

• [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.

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 peristed as SQL NULL, rather than JSON-encoded 'null'.

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

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.

References: #3075

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

References: #3141, pull request github:124

• [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.

References: #3137

### mysql¶

• [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 %.

• [mysql] [bug] [mysqlconnector] Unicode SQL is now passed for MySQLconnector version 2.0 and above; for Py2k and MySQL < 2.0, strings are encoded.

### sqlite¶

• [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.

References: #3211

### mssql¶

• [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”.

References: #3151

### oracle¶

• [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.

References: #2138

### misc¶

• [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.

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.

References: #3191

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

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

• [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.

References: #3168

## 0.9.7¶

Released: July 22, 2014

### orm¶

• [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.

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.

References: #2736, #3083

• [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’; a warning is now emitted. In 1.0 this will be promoted to a full exception.

References: #3117

• [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.

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.

References: #3106

• [orm] [bug] Fixed bug involving dynamic attributes, that was again a regression of #3060 from version 0.9.5. A self-referential relationship with lazy=’dynamic’ would raise a TypeError within a flush operation.

References: #3099

### sql¶

• [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: 0.8.7

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: 0.8.7

References: #3102

• [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.

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.

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.

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.

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.

References: #3122

### postgresql¶

• [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.

References: #3078, pull request bitbucket:22

• [postgresql] [feature] Added support for PostgreSQL JSONB via JSONB. Pull request courtesy Damian Dimmich.

References: pull request github:101

• [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.

References: #3134

### mysql¶

• [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: 0.8.7

References: #3101

### sqlite¶

• [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.

References: #3130

### 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.

References: pull request github:98

• [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: 0.8.7

• [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: 0.8.7

References: #3091

• [mssql] [bug] Fixed a regression from 0.9.5 caused by #3025 where the query used to determine “default schema” is invalid in SQL Server 2000. For SQL Server 2000 we go back to defaulting to the “schema name” parameter of the dialect, which is configurable but defaults to ‘dbo’.

References: #3025

### oracle¶

• [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.

References: #3128

### misc¶

• [bug] [tests] 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.

• [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.

References: #3097

## 0.9.6¶

Released: June 23, 2014

### orm¶

• [orm] [bug] Reverted the change for #3060 - this is a unit of work fix that is updated more comprehensively in 1.0 via #3061. The fix in #3060 unfortunately produces a new issue whereby an eager load of a many-to-one attribute can produce an event that is interpreted into an attribute change.

References: #3060

## 0.9.5¶

Released: June 23, 2014

### orm¶

• [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.

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.

References: #3017

• [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: 0.8.7

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: 0.8.7

References: #3047

• [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.

References: #3042

• [orm] [bug] Modified the behavior of orm.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.

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 unresovled 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.

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.

• [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.

References: #3057

• [orm] [bug] [sql] Fixes to the newly enhanced boolean coercion in #2804 where the new rules for “where” and “having” woudn’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.

References: #3013

### engine¶

• [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.

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.

References: #3043

### postgresql¶

• [postgresql] [feature] Added support for AUTOCOMMIT isolation level when using the pg8000 DBAPI. Pull request courtesy Tony Locke.

References: pull request github:88

• [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.

References: #2785, pull request bitbucket:18

• [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: 0.8.7

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: 0.8.7

References: pull request bitbucket:13

• [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.

References: #3021, pull request github:87

• [postgresql] [enhancement] Added a new type postgresql.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.

References: #3002

### mysql¶

• [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: 0.8.7

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: 0.8.7

References: pull request bitbucket:15

### mssql¶

• [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).

References: #3025

### firebird¶

• [firebird] [bug] Fixed bug where the combination of “limit” rendering as “SELECT FIRST n ROWS” using a bound parameter (only firebird has both), combined with column-level subqueries which also feature “limit” as well as “positional” bound parameters (e.g. qmark style) would erroneously assign the subquery-level positions before that of the enclosing SELECT, thus returning parameters which are out of order.

References: #3038

### misc¶

• [feature] [examples] Added a new example illustrating materialized paths, using the latest relationship features. Example courtesy Jack Zhou.

References: pull request bitbucket:21

• [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: 0.8.7

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: 0.8.7

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: 0.8.7

References: #3051, #3093, pull request bitbucket:24

• [bug] [testsuite] In public test suite, shanged to use of String(40) from less-supported Text in StringTest.test_literal_backslashes. Pullreq courtesy Jan.

References: pull request github:95

• [bug] [py3k] [tests] Corrected for some deprecation warnings involving the imp module and Python 3.3 or greater, when running tests. Pull request courtesy Matt Chisholm.

References: #2830, pull request bitbucket:2830

## 0.9.4¶

Released: March 28, 2014

### general¶

• [general] [feature] Support has been added for pytest to run tests. This runner is currently being supported in addition to nose, and will likely be preferred to nose going forward. The nose plugin system used by SQLAlchemy has been split out so that it works under pytest as well. There are no plans to drop support for nose at the moment and we hope that the test suite itself can continue to remain as agnostic of testing platform as possible. See the file README.unittests.rst for updated information on running tests with pytest.

The test plugin system has also been enhanced to support running tests against multiple database URLs at once, by specifying the --db and/or --dburi flags multiple times. This does not run the entire test suite for each database, but instead allows test cases that are specific to certain backends make use of that backend as the test is run. When using pytest as the test runner, the system will also run specific test suites multiple times, once for each database, particularly those tests within the “dialect suite”. The plan is that the enhanced system will also be used by Alembic, and allow Alembic to run migration operation tests against multiple backends in one run, including third-party backends not included within Alembic itself. Third party dialects and extensions are also encouraged to standardize on SQLAlchemy’s test suite as a basis; see the file README.dialects.rst for background on building out from SQLAlchemy’s test platform.

• [general] [bug] Adjusted setup.py file to support the possible future removal of the setuptools.Feature extension from setuptools. If this keyword isn’t present, the setup will still succeed with setuptools rather than falling back to distutils. C extension building can be disabled now also by setting the DISABLE_SQLALCHEMY_CEXT environment variable. This variable works whether or not setuptools is even available.

This change is also backported to: 0.8.6

References: #2986

• [general] [bug] Fixed some test/feature failures occurring in Python 3.4, in particular the logic used to wrap “column default” callables wouldn’t work properly for Python built-ins.

References: #2979

### orm¶

• [orm] [feature] Added new parameter orm.mapper.confirm_deleted_rows. Defaults to True, indicates that a series of DELETE statements should confirm that the cursor rowcount matches the number of primary keys that should have matched; this behavior had been taken off in most cases (except when version_id is used) to support the unusual edge case of self-referential ON DELETE CASCADE; to accommodate this, the message is now just a warning, not an exception, and the flag can be used to indicate a mapping that expects self-refererntial cascaded deletes of this nature. See also #2403 for background on the original change.

References: #3007

• [orm] [feature] A warning is emitted if the MapperEvents.before_configured() or MapperEvents.after_configured() events are applied to a specific mapper or mapped class, as the events are only invoked for the Mapper target at the general level.

• [orm] [feature] Added a new keyword argument once=True to event.listen() and event.listens_for(). This is a convenience feature which will wrap the given listener such that it is only invoked once.

• [orm] [feature] Added a new option to relationship.innerjoin which is to specify the string "nested". When set to "nested" as opposed to True, the “chaining” of joins will parenthesize the inner join on the right side of an existing outer join, instead of chaining as a string of outer joins. This possibly should have been the default behavior when 0.9 was released, as we introduced the feature of right-nested joins in the ORM, however we are keeping it as a non-default for now to avoid further surprises.

References: #2976

• [orm] [bug] Fixed ORM bug where changing the primary key of an object, then marking it for DELETE would fail to target the correct row for DELETE.

This change is also backported to: 0.8.6

References: #3006

• [orm] [bug] Fixed regression from 0.8.3 as a result of #2818 where Query.exists() wouldn’t work on a query that only had a Query.select_from() entry but no other entities.

This change is also backported to: 0.8.6

References: #2995

• [orm] [bug] Improved an error message which would occur if a query() were made against a non-selectable, such as a literal_column(), and then an attempt was made to use Query.join() such that the “left” side would be determined as None and then fail. This condition is now detected explicitly.

This change is also backported to: 0.8.6

• [orm] [bug] Removed stale names from sqlalchemy.orm.interfaces.__all__ and refreshed with current names, so that an import * from this module again works.

This change is also backported to: 0.8.6

References: #2975

• [orm] [bug] Fixed a very old behavior where the lazy load emitted for a one-to-many could inappropriately pull in the parent table, and also return results inconsistent based on what’s in the parent table, when the primaryjoin includes some kind of discriminator against the parent table, such as and_(parent.id == child.parent_id, parent.deleted == False). While this primaryjoin doesn’t make that much sense for a one-to-many, it is slightly more common when applied to the many-to-one side, and the one-to-many comes as a result of a backref. Loading rows from child in this case would keep parent.deleted == False as is within the query, thereby yanking it into the FROM clause and doing a cartesian product. The new behavior will now substitute the value of the local “parent.deleted” for that parameter as is appropriate. Though typically, a real-world app probably wants to use a different primaryjoin for the o2m side in any case.

References: #2948

• [orm] [bug] Improved the check for “how to join from A to B” such that when a table has multiple, composite foreign keys targeting a parent table, the relationship.foreign_keys argument will be properly interpreted in order to resolve the ambiguity; previously this condition would raise that there were multiple FK paths when in fact the foreign_keys argument should be establishing which one is expected.

References: #2965

• [orm] [bug] Added support for the not-quite-yet-documented insert=True flag for event.listen() to work with mapper / instance events.

• [orm] [bug] [engine] Fixed bug where events set to listen at the class level (e.g. on the Mapper or ClassManager level, as opposed to on an individual mapped class, and also on Connection) that also made use of internal argument conversion (which is most within those categories) would fail to be removable.

References: #2973

• [orm] [bug] Fixed regression from 0.8 where using an option like orm.lazyload() with the “wildcard” expression, e.g. "*", would raise an assertion error in the case where the query didn’t contain any actual entities. This assertion is meant for other cases and was catching this one inadvertently.

• [orm] [bug] [sqlite] More fixes to SQLite “join rewriting”; the fix from #2967 implemented right before the release of 0.9.3 affected the case where a UNION contained nested joins in it. “Join rewriting” is a feature with a wide range of possibilities and is the first intricate “SQL rewriting” feature we’ve introduced in years, so we’re sort of going through a lot of iterations with it (not unlike eager loading back in the 0.2/0.3 series, polymorphic loading in 0.4/0.5). We should be there soon so thanks for bearing with us :).

References: #2969

### engine¶

• [engine] [feature] Added some new event mechanics for dialect-level events; the initial implementation allows an event handler to redefine the specific mechanics by which an arbitrary dialect invokes execute() or executemany() on a DBAPI cursor. The new events, at this point semi-public and experimental, are in support of some upcoming transaction-related extensions.

• [engine] [feature] An event listener can now be associated with a Engine, after one or more Connection objects have been created (such as by an orm Session or via explicit connect) and the listener will pick up events from those connections. Previously, performance concerns pushed the event transfer from Engine to Connection at init-time only, but we’ve inlined a bunch of conditional checks to make this possible without any additional function calls.

References: #2978

• [engine] [bug] A major improvement made to the mechanics by which the Engine recycles the connection pool when a “disconnect” condition is detected; instead of discarding the pool and explicitly closing out connections, the pool is retained and a “generational” timestamp is updated to reflect the current time, thereby causing all existing connections to be recycled when they are next checked out. This greatly simplifies the recycle process, removes the need for “waking up” connect attempts waiting on the old pool and eliminates the race condition that many immediately-discarded “pool” objects could be created during the recycle operation.

References: #2985

• [engine] [bug] The ConnectionEvents.after_cursor_execute() event is now emitted for the “_cursor_execute()” method of Connection; this is the “quick” executor that is used for things like when a sequence is executed ahead of an INSERT statement, as well as for dialect startup checks like unicode returns, charset, etc. the ConnectionEvents.before_cursor_execute() event was already invoked here. The “executemany” flag is now always set to False here, as this event always corresponds to a single execution. Previously the flag could be True if we were acting on behalf of an executemany INSERT statement.

### sql¶

• [sql] [feature] Added support for literal rendering of boolean values, e.g. “true” / “false” or “1” / “0”.

• [sql] [feature] Added a new feature schema.conv(), the purpose of which is to mark a constraint name as already having had a naming convention applied. This token will be used by Alembic migrations as of Alembic 0.6.4 in order to render constraints in migration scripts with names marked as already having been subject to a naming convention.

• [sql] [feature] The new dialect-level keyword argument system for schema-level constructs has been enhanced in order to assist with existing schemes that rely upon addition of ad-hoc keyword arguments to constructs.

E.g., a construct such as Index will again accept ad-hoc keyword arguments within the Index.kwargs collection, after construction:

idx = Index('a', 'b')
idx.kwargs['mysql_someargument'] = True

To suit the use case of allowing custom arguments at construction time, the DialectKWArgs.argument_for() method now allows this registration:

Index.argument_for('mysql', 'someargument', False)

idx = Index('a', 'b', mysql_someargument=True)

References: #2866, #2962

• [sql] [bug] Fixed bug in tuple_() construct where the “type” of essentially the first SQL expression would be applied as the “comparison type” to a compared tuple value; this has the effect in some cases of an inappropriate “type coersion” occurring, such as when a tuple that has a mix of String and Binary values improperly coerces target values to Binary even though that’s not what they are on the left side. tuple_() now expects heterogeneous types within its list of values.

This change is also backported to: 0.8.6

References: #2977

• [sql] [bug] Fixed an 0.9 regression where a Table that failed to reflect correctly wouldn’t be removed from the parent MetaData, even though in an invalid state. Pullreq courtesy Roman Podoliaka.

References: #2988, pull request github:78

• [sql] [bug] MetaData.naming_convention feature will now also apply to CheckConstraint objects that are associated directly with a Column instead of just on the Table.

• [sql] [bug] Fixed bug in new MetaData.naming_convention feature where the name of a check constraint making use of the “%(constraint_name)s” token would get doubled up for the constraint generated by a boolean or enum type, and overall duplicate events would cause the “%(constraint_name)s” token to keep compounding itself.

References: #2991

• [sql] [bug] Adjusted the logic which applies names to the .c collection when a no-name BindParameter is received, e.g. via sql.literal() or similar; the “key” of the bind param is used as the key within .c. rather than the rendered name. Since these binds have “anonymous” names in any case, this allows individual bound parameters to have their own name within a selectable if they are otherwise unlabeled.

References: #2974

• [sql] [bug] Some changes to how the FromClause.c collection behaves when presented with duplicate columns. The behavior of emitting a warning and replacing the old column with the same name still remains to some degree; the replacement in particular is to maintain backwards compatibility. However, the replaced column still remains associated with the c collection now in a collection ._all_columns, which is used by constructs such as aliases and unions, to deal with the set of columns in c more towards what is actually in the list of columns rather than the unique set of key names. This helps with situations where SELECT statements with same-named columns are used in unions and such, so that the union can match the columns up positionally and also there’s some chance of FromClause.corresponding_column() still being usable here (it can now return a column that is only in selectable.c._all_columns and not otherwise named). The new collection is underscored as we still need to decide where this list might end up. Theoretically it would become the result of iter(selectable.c), however this would mean that the length of the iteration would no longer match the length of keys(), and that behavior needs to be checked out.

References: #2974

• [sql] [bug] Fixed issue in new TextClause.columns() method where the ordering of columns given positionally would not be preserved. This could have potential impact in positional situations such as applying the resulting TextAsFrom object to a union.

### postgresql¶

• [postgresql] [feature] Enabled “sane multi-row count” checking for the psycopg2 DBAPI, as this seems to be supported as of psycopg2 2.0.9.

This change is also backported to: 0.8.6

• [postgresql] [bug] Fixed regression caused by release 0.8.5 / 0.9.3’s compatibility enhancements where index reflection on PostgreSQL versions specific to only the 8.1, 8.2 series again broke, surrounding the ever problematic int2vector type. While int2vector supports array operations as of 8.1, apparently it only supports CAST to a varchar as of 8.3.

This change is also backported to: 0.8.6

References: #3000

### mysql¶

• [mysql] [bug] Tweaked the settings for mysql-connector-python; in Py2K, the “supports unicode statements” flag is now False, so that SQLAlchemy will encode the SQL string (note: not the parameters) to bytes before sending to the database. This seems to allow all unicode-related tests to pass for mysql-connector, including those that use non-ascii table/column names, as well as some tests for the TEXT type using unicode under cursor.executemany().

### oracle¶

• [oracle] [feature] Added a new engine option coerce_to_unicode=True to the cx_Oracle dialect, which restores the cx_Oracle outputtypehandler approach to Python unicode conversion under Python 2, which was removed in 0.9.2 as a result of #2911. Some use cases would prefer that unicode coersion is unconditional for all string values, despite performance concerns. Pull request courtesy Christoph Zwerschke.

References: #2911, pull request github:74

• [oracle] [bug] Added new datatype oracle.DATE, which is a subclass of DateTime. As Oracle has no “datetime” type per se, it instead has only DATE, it is appropriate here that the DATE type as present in the Oracle dialect be an instance of DateTime. This issue doesn’t change anything as far as the behavior of the type, as data conversion is handled by the DBAPI in any case, however the improved subclass layout will help the use cases of inspecting types for cross-database compatibility. Also removed uppercase DATETIME from the Oracle dialect as this type isn’t functional in that context.

References: #2987

### misc¶

• [bug] [ext] Fixed bug in mutable extension as well as attributes.flag_modified() where the change event would not be propagated if the attribute had been reassigned to itself.

This change is also backported to: 0.8.6

References: #2997

• [bug] [automap] [ext] Added support to automap for the case where a relationship should not be created between two classes that are in a joined inheritance relationship, for those foreign keys that link the subclass back to the superclass.

References: #3004

• [bug] [tests] Fixed a few errant u'' strings that would prevent tests from passing in Py3.2. Patch courtesy Arfrever Frehtes Taifersar Arahesis.

References: #2980

• [bug] [pool] Fixed small issue in SingletonThreadPool where the current connection to be returned might get inadvertently cleaned out during the “cleanup” process. Patch courtesy jd23.

• [bug] [ext] [py3k] Fixed bug in association proxy where assigning an empty slice (e.g. x[:] = [...]) would fail on Py3k.

• [bug] [ext] Fixed a regression in association proxy caused by #2810 which caused a user-provided “getter” to no longer receive values of None when fetching scalar values from a target that is non-present. The check for None introduced by this change is now moved into the default getter, so a user-provided getter will also again receive values of None.

References: #2810

• [bug] [examples] Fixed bug in the versioned_history example where column-level INSERT defaults would prevent history values of NULL from being written.

## 0.9.3¶

Released: February 19, 2014

### orm¶

• [orm] [feature] Added new MapperEvents.before_configured() event which allows an event at the start of configure_mappers(), as well as __declare_first__() hook within declarative to complement __declare_last__().

• [orm] [bug] Fixed bug where Query.get() would fail to consistently raise the InvalidRequestError that invokes when called on a query with existing criterion, when the given identity is already present in the identity map.

This change is also backported to: 0.8.5

References: #2951

• [orm] [bug] [sqlite] Fixed bug in SQLite “join rewriting” where usage of an exists() construct would fail to be rewritten properly, such as when the exists is mapped to a column_property in an intricate nested-join scenario. Also fixed a somewhat related issue where join rewriting would fail on the columns clause of the SELECT statement if the targets were aliased tables, as opposed to individual aliased columns.

References: #2967

• [orm] [bug] Fixed an 0.9 regression where ORM instance or mapper events applied to a base class such as a declarative base with the propagate=True flag would fail to apply to existing mapped classes which also used inheritance due to an assertion. Additionally, repaired an attribute error which could occur during removal of such an event, depending on how it was first assigned.

References: #2949

• [orm] [bug] Improved the initialization logic of composite attributes such that calling MyClass.attribute will not require that the configure mappers step has occurred, e.g. it will just work without throwing any error.

References: #2935

• [orm] [bug] More issues with [ticket:2932] first resolved in 0.9.2 where using a column key of the form <tablename>_<columnname> matching that of an aliased column in the text would still not match at the ORM level, which is ultimately due to a core column-matching issue. Additional rules have been added so that the column _label is taken into account when working with a TextAsFrom construct or with literal columns.

References: #2932

### engine¶

• [engine] [bug] [pool] Fixed a critical regression caused by #2880 where the newly concurrent ability to return connections from the pool means that the “first_connect” event is now no longer synchronized either, thus leading to dialect mis-configurations under even minimal concurrency situations.

This change is also backported to: 0.8.5

References: #2880, #2964

### sql¶

• [sql] [bug] Fixed bug where calling Insert.values() with an empty list or tuple would raise an IndexError. It now produces an empty insert construct as would be the case with an empty dictionary.

This change is also backported to: 0.8.5

References: #2944

• [sql] [bug] Fixed bug where in_() would go into an endless loop if erroneously passed a column expression whose comparator included the __getitem__() method, such as a column that uses the postgresql.ARRAY type.

This change is also backported to: 0.8.5

References: #2957

• [sql] [bug] Fixed regression in new “naming convention” feature where conventions would fail if the referred table in a foreign key contained a schema name. Pull request courtesy Thomas Farvour.

References: pull request github:67

• [sql] [bug] Fixed bug where so-called “literal render” of bindparam() constructs would fail if the bind were constructed with a callable, rather than a direct value. This prevented ORM expressions from being rendered with the “literal_binds” compiler flag.

### postgresql¶

• [postgresql] [feature] Added the TypeEngine.python_type convenience accessor onto the postgresql.ARRAY type. Pull request courtesy Alexey Terentev.

References: pull request github:64

• [postgresql] [bug] Added an additional message to psycopg2 disconnect detection, “could not send data to server”, which complements the existing “could not receive data from server” and has been observed by users.

This change is also backported to: 0.8.5

References: #2936

• [postgresql] [bug]

Support has been improved for PostgreSQL reflection behavior on very old (pre 8.1) versions of PostgreSQL, and potentially other PG engines such as Redshift (assuming Redshift reports the version as < 8.1). The query for “indexes” as well as “primary keys” relies upon inspecting a so-called “int2vector” datatype, which refuses to coerce to an array prior to 8.1 causing failures regarding the “ANY()” operator used in the query. Extensive googling has located the very hacky, but recommended-by-PG-core-developer query to use when PG version < 8.1 is in use, so index and primary key constraint reflection now work on these versions.

This change is also backported to: 0.8.5

• [postgresql] [bug] Revised this very old issue where the PostgreSQL “get primary key” reflection query were updated to take into account primary key constraints that were renamed; the newer query fails on very old versions of PostgreSQL such as version 7, so the old query is restored in those cases when server_version_info < (8, 0) is detected.

This change is also backported to: 0.8.5

References: #2291

• [postgresql] [bug] Added server version detection to the newly added dialect startup query for “show standard_conforming_strings”; as this variable was added as of PG 8.2, we skip the query for PG versions who report a version string earlier than that.

References: #2946

### mysql¶

• [mysql] [feature] Added new MySQL-specific mysql.DATETIME which includes fractional seconds support; also added fractional seconds support to mysql.TIMESTAMP. DBAPI support is limited, though fractional seconds are known to be supported by MySQL Connector/Python. Patch courtesy Geert JM Vanderkelen.

This change is also backported to: 0.8.5

References: #2941

• [mysql] [bug] Added support for the PARTITION BY and PARTITIONS MySQL table keywords, specified as mysql_partition_by='value' and mysql_partitions='value' to Table. Pull request courtesy Marcus McCurdy.

This change is also backported to: 0.8.5

References: #2966, pull request bitbucket:12

• [mysql] [bug] Fixed bug which prevented MySQLdb-based dialects (e.g. pymysql) from working in Py3K, where a check for “connection charset” would fail due to Py3K’s more strict value comparison rules. The call in question wasn’t taking the database version into account in any case as the server version was still None at that point, so the method overall has been simplified to rely upon connection.character_set_name().

This change is also backported to: 0.8.5

References: #2933

• [mysql] [bug] [cymysql] Fixed bug in cymysql dialect where a version string such as '33a-MariaDB' would fail to parse properly. Pull request courtesy Matt Schmidt.

References: #2934, pull request github:69

### sqlite¶

• [sqlite] [bug] The SQLite dialect will now skip unsupported arguments when reflecting types; such as if it encounters a string like INTEGER(5), the INTEGER type will be instantiated without the “5” being included, based on detecting a TypeError on the first attempt.

• [sqlite] [bug] Support has been added to SQLite type reflection to fully support the “type affinity” contract specified at http://www.sqlite.org/datatype3.html. In this scheme, keywords like INT, CHAR, BLOB or REAL located in the type name generically associate the type with one of five affinities. Pull request courtesy Erich Blume.

Type Reflection

References: pull request github:65

## 0.9.2¶

Released: February 2, 2014

### orm¶

• [orm] [feature] Added a new parameter Operators.op.is_comparison. This flag allows a custom op from Operators.op() to be considered as a “comparison” operator, thus usable for custom relationship.primaryjoin conditions.

• [orm] [feature] Support is improved for supplying a join() construct as the target of relationship.secondary for the purposes of creating very complex relationship() join conditions. The change includes adjustments to query joining, joined eager loading to not render a SELECT subquery, changes to lazy loading such that the “secondary” target is properly included in the SELECT, and changes to declarative to better support specification of a join() object with classes as targets.

The new use case is somewhat experimental, but a new documentation section has been added.

• [orm] [bug] Fixed error message when an iterator object is passed to class_mapper() or similar, where the error would fail to render on string formatting. Pullreq courtesy Kyle Stark.

This change is also backported to: 0.8.5

References: pull request github:58

• [orm] [bug] Fixed bug in new TextAsFrom construct where Column- oriented row lookups were not matching up to the ad-hoc ColumnClause objects that TextAsFrom generates, thereby making it not usable as a target in Query.from_statement(). Also fixed Query.from_statement() mechanics to not mistake a TextAsFrom for a Select construct. This bug is also an 0.9 regression as the Text.columns() method is called to accommodate the text.typemap argument.

References: #2932

• [orm] [bug] Added a new directive used within the scope of an attribute “set” operation to disable autoflush, in the case that the attribute needs to lazy-load the “old” value, as in when replacing one-to-one values or some kinds of many-to-one. A flush at this point otherwise occurs at the point that the attribute is None and can cause NULL violations.

References: #2921

• [orm] [bug] Fixed an 0.9 regression where the automatic aliasing applied by Query and in other situations where selects or joins were aliased (such as joined table inheritance) could fail if a user-defined Column subclass were used in the expression. In this case, the subclass would fail to propagate ORM-specific “annotations” along needed by the adaptation. The “expression annotations” system has been corrected to account for this case.

References: #2918

• [orm] [bug] Fixed a bug involving the new flattened JOIN structures which are used with joinedload() (thereby causing a regression in joined eager loading) as well as aliased() in conjunction with the flat=True flag and joined-table inheritance; basically multiple joins across a “parent JOIN sub” entity using different paths to get to a target class wouldn’t form the correct ON conditions. An adjustment / simplification made in the mechanics of figuring out the “left side” of the join in the case of an aliased, joined-inh class repairs the issue.

References: #2908

### sql¶

• [sql] [feature] Added MetaData.reflect.**dialect_kwargs to support dialect-level reflection options for all Table objects reflected.

• [sql] [feature] Added a new feature which allows automated naming conventions to be applied to Constraint and Index objects. Based on a recipe in the wiki, the new feature uses schema-events to set up names as various schema objects are associated with each other. The events then expose a configuration system through a new argument MetaData.naming_convention. This system allows production of both simple and custom naming schemes for constraints and indexes on a per-MetaData basis.

References: #2923

• [sql] [feature] Options can now be specified on a PrimaryKeyConstraint object independently of the specification of columns in the table with the primary_key=True flag; use a PrimaryKeyConstraint object with no columns in it to achieve this result.

Previously, an explicit PrimaryKeyConstraint would have the effect of those columns marked as primary_key=True being ignored; since this is no longer the case, the PrimaryKeyConstraint will now assert that either one style or the other is used to specify the columns, or if both are present, that the column lists match exactly. If an inconsistent set of columns in the PrimaryKeyConstraint and within the Table marked as primary_key=True are present, a warning is emitted, and the list of columns is taken only from the PrimaryKeyConstraint alone as was the case in previous releases.

References: #2910

• [sql] [feature] The system by which schema constructs and certain SQL constructs accept dialect-specific keyword arguments has been enhanced. This system includes commonly the Table and Index constructs, which accept a wide variety of dialect-specific arguments such as mysql_engine and postgresql_where, as well as the constructs PrimaryKeyConstraint, UniqueConstraint, Update, Insert and Delete, and also newly added kwarg capability to ForeignKeyConstraint and ForeignKey. The change is that participating dialects can now specify acceptable argument lists for these constructs, allowing an argument error to be raised if an invalid keyword is specified for a particular dialect. If the dialect portion of the keyword is unrecognized, a warning is emitted only; while the system will actually make use of setuptools entrypoints in order to locate non-local dialects, the use case where certain dialect-specific arguments are used in an environment where that third-party dialect is uninstalled remains supported. Dialects also have to explicitly opt-in to this system, so that external dialects which aren’t making use of this system will remain unaffected.

References: #2866

• [sql] [bug] The behavior of Table.tometadata() has been adjusted such that the schema target of a ForeignKey will not be changed unless that schema matches that of the parent table. That is, if a table “schema_a.user” has a foreign key to “schema_b.order.id”, the “schema_b” target will be maintained whether or not the “schema” argument is passed to Table.tometadata(). However if a table “schema_a.user” refers to “schema_a.order.id”, the presence of “schema_a” will be updated on both the parent and referred tables. This is a behavioral change hence isn’t likely to be backported to 0.8; it is assumed that the previous behavior is pretty buggy however and that it’s unlikely anyone was relying upon it.

Additionally, a new parameter has been added Table.tometadata.referred_schema_fn. This refers to a callable function which will be used to determine the new referred schema for any ForeignKeyConstraint encountered in the tometadata operation. This callable can be used to revert to the previous behavior or to customize how referred schemas are treated on a per-constraint basis.

References: #2913

• [sql] [bug] Fixed bug whereby binary type would fail in some cases if used with a “test” dialect, such as a DefaultDialect or other dialect with no DBAPI.

• [sql] [bug] [py3k] Fixed bug where “literal binds” wouldn’t work with a bound parameter that’s a binary type. A similar, but different, issue is fixed in 0.8.

• [sql] [bug] Fixed regression whereby the “annotation” system used by the ORM was leaking into the names used by standard functions in sqlalchemy.sql.functions, such as func.coalesce() and func.max(). Using these functions in ORM attributes and thus producing annotated versions of them could corrupt the actual function name rendered in the SQL.

References: #2927

• [sql] [bug] Fixed 0.9 regression where the new sortable support for RowProxy would lead to TypeError when compared to non-tuple types as it attempted to apply tuple() to the “other” object unconditionally. The full range of Python comparison operators have now been implemented on RowProxy, using an approach that guarantees a comparison system that is equivalent to that of a tuple, and the “other” object is only coerced if it’s an instance of RowProxy.

References: #2848, #2924

• [sql] [bug] A UniqueConstraint created inline with a Table that has no columns within it will be skipped. Pullreq courtesy Derek Harland.

References: pull request bitbucket:11

• [sql] [bug] [orm] Fixed the multiple-table “UPDATE..FROM” construct, only usable on MySQL, to correctly render the SET clause among multiple columns with the same name across tables. This also changes the name used for the bound parameter in the SET clause to “<tablename>_<colname>” for the non-primary table only; as this parameter is typically specified using the Column object directly this should not have an impact on applications. The fix takes effect for both Table.update() as well as Query.update() in the ORM.

References: #2912

### schema¶

• [schema] [bug] Restored sqlalchemy.schema.SchemaVisitor to the .schema module. Pullreq courtesy Sean Dague.

References: pull request github:57

### postgresql¶

• [postgresql] [feature] Added a new dialect-level argument postgresql_ignore_search_path; this argument is accepted by both the Table constructor as well as by the MetaData.reflect() method. When in use against PostgreSQL, a foreign-key referenced table which specifies a remote schema name will retain that schema name even if the name is present in the search_path; the default behavior since 0.7.3 has been that schemas present in search_path would not be copied to reflected ForeignKey objects. The documentation has been updated to describe in detail the behavior of the pg_get_constraintdef() function and how the postgresql_ignore_search_path feature essentially determines if we will honor the schema qualification reported by this function or not.

References: #2922

### mysql¶

• [mysql] [bug] Some missing methods added to the cymysql dialect, including _get_server_version_info() and _detect_charset(). Pullreq courtesy Hajime Nakagami.

This change is also backported to: 0.8.5

References: pull request github:61

• [mysql] [bug] [sql] Added new test coverage for so-called “down adaptions” of SQL types, where a more specific type is adapted to a more generic one - this use case is needed by some third party tools such as sqlacodegen. The specific cases that needed repair within this test suite were that of mysql.ENUM being downcast into a types.Enum, and that of SQLite date types being cast into generic date types. The adapt() method needed to become more specific here to counteract the removal of a “catch all” **kwargs collection on the base TypeEngine class that was removed in 0.9.

References: #2917

• [mysql] [bug] The MySQL CAST compilation now takes into account aspects of a string type such as “charset” and “collation”. While MySQL wants all character- based CAST calls to use the CHAR type, we now create a real CHAR object at CAST time and copy over all the parameters it has, so that an expression like cast(x, mysql.TEXT(charset='utf8')) will render CAST(t.col AS CHAR CHARACTER SET utf8).

• [mysql] [bug] Added new “unicode returns” detection to the MySQL dialect and to the default dialect system overall, such that any dialect can add extra “tests” to the on-first-connect “does this DBAPI return unicode directly?” detection. In this case, we are adding a check specifically against the “utf8” encoding with an explicit “utf8_bin” collation type (after checking that this collation is available) to test for some buggy unicode behavior observed with MySQLdb version 1.2.3. While MySQLdb has resolved this issue as of 1.2.4, the check here should guard against regressions. The change also allows the “unicode” checks to log in the engine logs, which was not previously the case.

References: #2906

• [mysql] [bug] [engine] [pool] Connection now associates a new RootTransaction or TwoPhaseTransaction with its immediate _ConnectionFairy as a “reset handler” for the span of that transaction, which takes over the task of calling commit() or rollback() for the “reset on return” behavior of Pool if the transaction was not otherwise completed. This resolves the issue that a picky transaction like that of MySQL two-phase will be properly closed out when the connection is closed without an explicit rollback or commit (e.g. no longer raises “XAER_RMFAIL” in this case - note this only shows up in logging as the exception is not propagated within pool reset). This issue would arise e.g. when using an orm Session with twophase set, and then Session.close() is called without an explicit rollback or commit. The change also has the effect that you will now see an explicit “ROLLBACK” in the logs when using a Session object in non-autocommit mode regardless of how that session was discarded. Thanks to Jeff Dairiki and Laurence Rowe for isolating the issue here.

References: #2907

### sqlite¶

• [sqlite] [bug] Fixed bug whereby SQLite compiler failed to propagate compiler arguments such as “literal binds” into a CAST expression.

### oracle¶

• [oracle] [bug] It’s been observed that the usage of a cx_Oracle “outputtypehandler” in Python 2.xx in order to coerce string values to Unicode is inordinately expensive; even though cx_Oracle is written in C, when you pass the Python unicode primitive to cursor.var() and associate with an output handler, the library counts every conversion as a Python function call with all the requisite overhead being recorded; this despite the fact when running in Python 3, all strings are also unconditionally coerced to unicode but it does not incur this overhead, meaning that cx_Oracle is failing to use performant techniques in Py2K. As SQLAlchemy cannot easily select for this style of type handler on a per-column basis, the handler was assembled unconditionally thereby adding the overhead to all string access.

So this logic has been replaced with SQLAlchemy’s own unicode conversion system, which now only takes effect in Py2K for columns that are requested as unicode. When C extensions are used, SQLAlchemy’s system appears to be 2-3x faster than cx_Oracle’s. Additionally, SQLAlchemy’s unicode conversion has been enhanced such that when the “conditional” converter is required (now needed for the Oracle backend), the check for “already unicode” is now performed in C and no longer introduces significant overhead.

This change has two impacts on the cx_Oracle backend. One is that string values in Py2K which aren’t specifically requested with the Unicode type or convert_unicode=True will now come back as str, not unicode - this behavior is similar to a backend such as MySQL. Additionally, when unicode values are requested with the cx_Oracle backend, if the C extensions are not used, there is now an additional overhead of an isinstance() check per column. This tradeoff has been made as it can be worked around and no longer places a performance burden on the likely majority of Oracle result columns that are non-unicode strings.

References: #2911

### misc¶

• [bug] [examples] Added a tweak to the “history_meta” example where the check for “history” on a relationship-bound attribute will now no longer emit any SQL if the relationship is unloaded.

• [bug] [pool] The argument names for the PoolEvents.reset() event have been renamed to dbapi_connection and connection_record in order to maintain consistency with all the other pool events. It is expected that any existing listeners for this relatively new and seldom-used event are using positional style to receive arguments in any case.

• [bug] [cextensions] [py3k] Fixed an issue where the C extensions in Py3K are using the wrong API to specify the top-level module function, which breaks in Python 3.4b2. Py3.4b2 changes PyMODINIT_FUNC to return “void” instead of PyObject *, so we now make sure to use “PyMODINIT_FUNC” instead of PyObject * directly. Pull request courtesy cgohlke.

References: pull request github:55

## 0.9.1¶

Released: January 5, 2014

### orm¶

• [orm] [feature] [extensions] A new, experimental extension sqlalchemy.ext.automap is added. This extension expands upon the functionality of Declarative as well as the DeferredReflection class to produce a base class which automatically generates mapped classes and relationships based on table metadata.

• [orm] [bug] [events] Fixed regression where using a functools.partial() with the event system would cause a recursion overflow due to usage of inspect.getargspec() on it in order to detect a legacy calling signature for certain events, and apparently there’s no way to do this with a partial object. Instead we skip the legacy check and assume the modern style; the check itself now only occurs for the SessionEvents.after_bulk_update and SessionEvents.after_bulk_delete events. Those two events will require the new signature style if assigned to a “partial” event listener.

References: #2905

• [orm] [bug] Fixed bug where using new Session.info attribute would fail if the .info argument were only passed to the sessionmaker creation call but not to the object itself. Courtesy Robin Schoonover.

References: pull request bitbucket:9

• [orm] [bug] Fixed regression where we don’t check the given name against the correct string class when setting up a backref based on a name, therefore causing the error “too many values to unpack”. This was related to the Py3k conversion.

References: #2901

• [orm] [bug] Fixed regression where we apparently still create an implicit alias when saying query(B).join(B.cs), where “C” is a joined inh class; however, this implicit alias was created only considering the immediate left side, and not a longer chain of joins along different joined-inh subclasses of the same base. As long as we’re still implicitly aliasing in this case, the behavior is dialed back a bit so that it will alias the right side in a wider variety of cases.

References: #2903

### orm declarative¶

• [bug] [declarative] [orm] Fixed an extremely unlikely memory issue where when using DeferredReflection to define classes pending for reflection, if some subset of those classes were discarded before the DeferredReflection.prepare() method were called to reflect and map the class, a strong reference to the class would remain held within the declarative internals. This internal collection of “classes to map” now uses weak references against the classes themselves.

• [bug] [declarative] [orm] A quasi-regression where apparently in 0.8 you can set a class-level attribute on declarative to simply refer directly to an InstrumentedAttribute on a superclass or on the class itself, and it acts more or less like a synonym; in 0.9, this fails to set up enough bookkeeping to keep up with the more liberalized backref logic from #2789. Even though this use case was never directly considered, it is now detected by declarative at the “setattr()” level as well as when setting up a subclass, and the mirrored/renamed attribute is now set up as a synonym() instead.

References: #2900

### sql¶

• [sql] [feature] Conjunctions like and_() and or_() can now accept Python generators as a single argument, e.g.:

and_(x == y for x, y in tuples)

The logic here looks for a single argument *args where the first element is an instance of types.GeneratorType.

## 0.9.0¶

Released: December 30, 2013

### orm¶

• [orm] [feature] The exc.StatementError or DBAPI-related subclass now can accommodate additional information about the “reason” for the exception; the Session now adds some detail to it when the exception occurs within an autoflush. This approach is taken as opposed to combining FlushError with a Python 3 style “chained exception” approach so as to maintain compatibility both with Py2K code as well as code that already catches IntegrityError or similar.

• [orm] [feature] [backrefs] Added new argument include_backrefs=True to the validates() function; when set to False, a validation event will not be triggered if the event was initated as a backref to an attribute operation from the other side.

References: #1535

• [orm] [feature] A new API for specifying the FOR UPDATE clause of a SELECT is added with the new Query.with_for_update() method, to complement the new GenerativeSelect.with_for_update() method. Pull request courtesy Mario Lassnig.

References: pull request github:42

• [orm] [bug] An adjustment to the subqueryload() strategy which ensures that the query runs after the loading process has begun; this is so that the subqueryload takes precedence over other loaders that may be hitting the same attribute due to other eager/noload situations at the wrong time.

This change is also backported to: 0.8.5

References: #2887

• [orm] [bug] Fixed bug when using joined table inheritance from a table to a select/alias on the base, where the PK columns were also not same named; the persistence system would fail to copy primary key values from the base table to the inherited table upon INSERT.

This change is also backported to: 0.8.5

References: #2885

• [orm] [bug] composite() will raise an informative error message when the columns/attribute (names) passed don’t resolve to a Column or mapped attribute (such as an erroneous tuple); previously raised an unbound local.

This change is also backported to: 0.8.5

References: #2889

• [orm] [bug] Fixed a regression introduced by #2818 where the EXISTS query being generated would produce a “columns being replaced” warning for a statement with two same-named columns, as the internal SELECT wouldn’t have use_labels set.

This change is also backported to: 0.8.4

References: #2818

• [orm] [bug] [collections] [py3k] Added support for the Python 3 method list.clear() within the ORM collection instrumentation system; pull request courtesy Eduardo Schettino.

References: pull request github:40

• [orm] [bug] Some refinements to the AliasedClass construct with regards to descriptors, like hybrids, synonyms, composites, user-defined descriptors, etc. The attribute adaptation which goes on has been made more robust, such that if a descriptor returns another instrumented attribute, rather than a compound SQL expression element, the operation will still proceed. Additionally, the “adapted” operator will retain its class; previously, a change in class from InstrumentedAttribute to QueryableAttribute (a superclass) would interact with Python’s operator system such that an expression like aliased(MyClass.x) > MyClass.x would reverse itself to read myclass.x < myclass_1.x. The adapted attribute will also refer to the new AliasedClass as its parent which was not always the case before.

References: #2872

• [orm] [bug] The viewonly flag on relationship() will now prevent attribute history from being written on behalf of the target attribute. This has the effect of the object not being written to the Session.dirty list if it is mutated. Previously, the object would be present in Session.dirty, but no change would take place on behalf of the modified attribute during flush. The attribute still emits events such as backref events and user-defined events and will still receive mutations from backrefs.

References: #2833

• [orm] [bug] Added support for new Session.info attribute to scoped_session.

• [orm] [bug] Fixed bug where usage of new Bundle object would cause the Query.column_descriptions attribute to fail.

• [orm] [bug] [sql] [sqlite] Fixed a regression introduced by the join rewriting feature of #2369 and #2587 where a nested join with one side already an aliased select would fail to translate the ON clause on the outside correctly; in the ORM this could be seen when using a SELECT statement as a “secondary” table.

References: #2858

### engine¶

• [engine] [feature] The engine_from_config() function has been improved so that we will be able to parse dialect-specific arguments from string configuration dictionaries. Dialect classes can now provide their own list of parameter types and string-conversion routines. The feature is not yet used by the built-in dialects, however.

References: #2875

• [engine] [bug] A DBAPI that raises an error on connect() which is not a subclass of dbapi.Error (such as TypeError, NotImplementedError, etc.) will propagate the exception unchanged. Previously, the error handling specific to the connect() routine would both inappropriately run the exception through the dialect’s Dialect.is_disconnect() routine as well as wrap it in a sqlalchemy.exc.DBAPIError. It is now propagated unchanged in the same way as occurs within the execute process.

This change is also backported to: 0.8.4

References: #2881

• [engine] [bug] [pool] The QueuePool has been enhanced to not block new connection attempts when an existing connection attempt is blocking. Previously, the production of new connections was serialized within the block that monitored overflow; the overflow counter is now altered within its own critical section outside of the connection process itself.

This change is also backported to: 0.8.4

References: #2880

• [engine] [bug] [pool] Made a slight adjustment to the logic which waits for a pooled connection to be available, such that for a connection pool with no timeout specified, it will every half a second break out of the wait to check for the so-called “abort” flag, which allows the waiter to break out in case the whole connection pool was dumped; normally the waiter should break out due to a notify_all() but it’s possible this notify_all() is missed in very slim cases. This is an extension of logic first introduced in 0.8.0, and the issue has only been observed occasionally in stress tests.

This change is also backported to: 0.8.4

References: #2522

• [engine] [bug] Fixed bug where SQL statement would be improperly ASCII-encoded when a pre-DBAPI StatementError were raised within Connection.execute(), causing encoding errors for non-ASCII statements. The stringification now remains within Python unicode thus avoiding encoding errors.

This change is also backported to: 0.8.4

References: #2871

• [engine] [bug] The create_engine() routine and the related make_url() function no longer considers the + sign to be a space within the password field. The parsing has been adjuted to match RFC 1738 exactly, in that both username and password expect only :, @, and / to be encoded.

References: #2873

• [engine] [bug] The RowProxy object is now sortable in Python as a regular tuple is; this is accomplished via ensuring tuple() conversion on both sides within the __eq__() method as well as the addition of a __lt__() method.

References: #2848

### sql¶

• [sql] [feature] New improvements to the text() construct, including more flexible ways to set up bound parameters and return types; in particular, a text() can now be turned into a full FROM-object, embeddable in other statements as an alias or CTE using the new method TextClause.columns(). The text() construct can also render “inline” bound parameters when the construct is compiled in a “literal bound” context.

References: #2877, #2882

• [sql] [feature] A new API for specifying the FOR UPDATE clause of a SELECT is added with the new GenerativeSelect.with_for_update() method. This method supports a more straightforward system of setting dialect-specific options compared to the for_update keyword argument of select(), and also includes support for the SQL standard FOR UPDATE OF clause. The ORM also includes a new corresponding method Query.with_for_update(). Pull request courtesy Mario Lassnig.

References: pull request github:42

• [sql] [feature] The precision used when coercing a returned floating point value to Python Decimal via string is now configurable. The flag decimal_return_scale is now supported by all Numeric and Float types, which will ensure this many digits are taken from the native floating point value when it is converted to string. If not present, the type will make use of the value of .scale, if the type supports this setting and it is non-None. Otherwise the original default length of 10 is used.

References: #2867

• [sql] [bug] Fixed issue where a primary key column that has a Sequence on it, yet the column is not the “auto increment” column, either because it has a foreign key constraint or autoincrement=False set, would attempt to fire the Sequence on INSERT for backends that don’t support sequences, when presented with an INSERT missing the primary key value. This would take place on non-sequence backends like SQLite, MySQL.

This change is also backported to: 0.8.5

References: #2896

• [sql] [bug] Fixed bug with Insert.from_select() method where the order of the given names would not be taken into account when generating the INSERT statement, thus producing a mismatch versus the column names in the given SELECT statement. Also noted that Insert.from_select() implies that Python-side insert defaults cannot be used, since the statement has no VALUES clause.

This change is also backported to: 0.8.5

References: #2895

• [sql] [bug] The cast() function, when given a plain literal value, will now apply the given type to the given literal value on the bind parameter side according to the type given to the cast, in the same manner as that of the type_coerce() function. However unlike type_coerce(), this only takes effect if a non-clauseelement value is passed to cast(); an existing typed construct will retain its type.

• [sql] [bug] The ForeignKey class more aggressively checks the given column argument. If not a string, it checks that the object is at least a ColumnClause, or an object that resolves to one, and that the .table attribute, if present, refers to a TableClause or subclass, and not something like an Alias. Otherwise, a ArgumentError is raised.

References: #2883

• [sql] [bug] The precedence rules for the ColumnOperators.collate() operator have been modified, such that the COLLATE operator is now of lower precedence than the comparison operators. This has the effect that a COLLATE applied to a comparison will not render parenthesis around the comparison, which is not parsed by backends such as MSSQL. The change is backwards incompatible for those setups that were working around the issue by applying Operators.collate() to an individual element of the comparison expression, rather than the comparison expression as a whole.

References: #2879

• [sql] [enhancement] The exception raised when a BindParameter is present in a compiled statement without a value now includes the key name of the bound parameter in the error message.

This change is also backported to: 0.8.5

### schema¶

• [schema] [bug] Fixed a regression caused by #2812 where the repr() for table and column names would fail if the name contained non-ascii characters.

References: #2868

### postgresql¶

• [postgresql] [feature] Support for PostgreSQL JSON has been added, using the new JSON type. Huge thanks to Nathan Rice for implementing and testing this.

References: #2581, pull request github:50

• [postgresql] [feature] Added support for PostgreSQL TSVECTOR via the postgresql.TSVECTOR type. Pull request courtesy Noufal Ibrahim.

References: pull request bitbucket:8

• [postgresql] [bug] Fixed bug where index reflection would mis-interpret indkey values when using the pypostgresql adapter, which returns these values as lists vs. psycopg2’s return type of string.

This change is also backported to: 0.8.4

References: #2855

• [postgresql] [bug] Now using psycopg2 UNICODEARRAY extension for handling unicode arrays with psycopg2 + normal “native unicode” mode, in the same way the UNICODE extension is used.

• [postgresql] [bug] Fixed bug where values within an ENUM weren’t escaped for single quote signs. Note that this is backwards-incompatible for existing workarounds that manually escape the single quotes.

References: #2878

### mysql¶

• [mysql] [bug] Improvements to the system by which SQL types generate within __repr__(), particularly with regards to the MySQL integer/numeric/ character types which feature a wide variety of keyword arguments. The __repr__() is important for use with Alembic autogenerate for when Python code is rendered in a migration script.

References: #2893

### mssql¶

• [mssql] [bug] [firebird] The “asdecimal” flag used with the Float type will now work with Firebird as well as the mssql+pyodbc dialects; previously the decimal conversion was not occurring.

This change is also backported to: 0.8.5

• [mssql] [bug] [pymssql] Added “Net-Lib error during Connection reset by peer” message to the list of messages checked for “disconnect” within the pymssql dialect. Courtesy John Anderson.

This change is also backported to: 0.8.5

References: pull request github:51

• [mssql] [bug] Fixed bug introduced in 0.8.0 where the DROP INDEX statement for an index in MSSQL would render incorrectly if the index were in an alternate schema; the schemaname/tablename would be reversed. The format has been also been revised to match current MSSQL documentation. Courtesy Derek Harland.

This change is also backported to: 0.8.4

References: pull request bitbucket:7

### oracle¶

• [oracle] [bug] Added ORA-02396 “maximum idle time” error code to list of “is disconnect” codes with cx_oracle.

This change is also backported to: 0.8.4

References: #2864

• [oracle] [bug] Fixed bug where Oracle VARCHAR types given with no length (e.g. for a CAST or similar) would incorrectly render None CHAR or similar.

This change is also backported to: 0.8.4

References: #2870

### firebird¶

• [firebird] [bug] The firebird dialect will quote identifiers which begin with an underscore. Courtesy Treeve Jelbert.

This change is also backported to: 0.8.5

References: #2897

• [firebird] [bug] Fixed bug in Firebird index reflection where the columns within the index were not sorted correctly; they are now sorted in order of RDB$FIELD_POSITION. This change is also backported to: 0.8.5 • [firebird] [bug] Changed the queries used by Firebird to list table and view names to query from the rdb$relations view instead of the rdb$relation_fields and rdb$view_relations views. Variants of both the old and new queries are mentioned on many FAQ and blogs, however the new queries are taken straight from the “Firebird FAQ” which appears to be the most official source of info.

References: #2898

### misc¶

• [removed] The “informix” and “informixdb” dialects have been removed; the code is now available as a separate repository on Bitbucket. The IBM-DB project has provided production-level Informix support since the informixdb dialect was first added.

• [bug] [declarative] Error message when a string arg sent to relationship() which doesn’t resolve to a class or mapper has been corrected to work the same way as when a non-string arg is received, which indicates the name of the relationship which had the configurational error.

This change is also backported to: 0.8.5

References: #2888

• [bug] [ext] Fixed bug which prevented the serializer extension from working correctly with table or column names that contain non-ASCII characters.

This change is also backported to: 0.8.4

References: #2869

• [bug] [examples] Fixed bug which prevented history_meta recipe from working with joined inheritance schemes more than one level deep.

## 0.9.0b1¶

Released: October 26, 2013

### general¶

• [general] [feature] [py3k] The C extensions are ported to Python 3 and will build under any supported CPython 2 or 3 environment.

References: #2161

• [general] [feature] [py3k] The codebase is now “in-place” for Python 2 and 3, the need to run 2to3 has been removed. Compatibility is now against Python 2.6 on forward.

References: #2671

• [general] A large refactoring of packages has reorganized the import structure of many Core modules as well as some aspects of the ORM modules. In particular sqlalchemy.sql has been broken out into several more modules than before so that the very large size of sqlalchemy.sql.expression is now pared down. The effort has focused on a large reduction in import cycles. Additionally, the system of API functions in sqlalchemy.sql.expression and sqlalchemy.orm has been reorganized to eliminate redundancy in documentation between the functions vs. the objects they produce.

### orm¶

• [orm] [feature] Added new option to relationship() distinct_target_key. This enables the subquery eager loader strategy to apply a DISTINCT to the innermost SELECT subquery, to assist in the case where duplicate rows are generated by the innermost query which corresponds to this relationship (there’s not yet a general solution to the issue of dupe rows within subquery eager loading, however, when joins outside of the innermost subquery produce dupes). When the flag is set to True, the DISTINCT is rendered unconditionally, and when it is set to None, DISTINCT is rendered if the innermost relationship targets columns that do not comprise a full primary key. The option defaults to False in 0.8 (e.g. off by default in all cases), None in 0.9 (e.g. automatic by default). Thanks to Alexander Koval for help with this.

This change is also backported to: 0.8.3

References: #2836

• [orm] [feature] The association proxy now returns None when fetching a scalar attribute off of a scalar relationship, where the scalar relationship itself points to None, instead of raising an AttributeError.

References: #2810

• [orm] [feature] Added new method AttributeState.load_history(), works like AttributeState.history but also fires loader callables.

References: #2787

• [orm] [feature] Added a new load option orm.load_only(). This allows a series of column names to be specified as loading “only” those attributes, deferring the rest.

References: #1418

• [orm] [feature] The system of loader options has been entirely rearchitected to build upon a much more comprehensive base, the Load object. This base allows any common loader option like joinedload(), defer(), etc. to be used in a “chained” style for the purpose of specifying options down a path, such as joinedload("foo").subqueryload("bar"). The new system supersedes the usage of dot-separated path names, multiple attributes within options, and the usage of _all() options.

References: #1418

• [orm] [feature] The composite() construct now maintains the return object when used in a column-oriented Query, rather than expanding out into individual columns. This makes use of the new Bundle feature internally. This behavior is backwards incompatible; to select from a composite column which will expand out, use MyClass.some_composite.clauses.

References: #2824

• [orm] [feature] A new construct Bundle is added, which allows for specification of groups of column expressions to a Query construct. The group of columns are returned as a single tuple by default. The behavior of Bundle can be overridden however to provide any sort of result processing to the returned row. The behavior of Bundle is also embedded into composite attributes now when they are used in a column-oriented Query.

References: #2824

• [orm] [feature] The version_id_generator parameter of Mapper can now be specified to rely upon server generated version identifiers, using triggers or other database-provided versioning features, or via an optional programmatic value, by setting version_id_generator=False. When using a server-generated version identfier, the ORM will use RETURNING when available to immediately load the new version value, else it will emit a second SELECT.

References: #2793

• [orm] [feature] The eager_defaults flag of Mapper will now allow the newly generated default values to be fetched using an inline RETURNING clause, rather than a second SELECT statement, for backends that support RETURNING.

References: #2793

• [orm] [feature] Added a new attribute Session.info to Session; this is a dictionary where applications can store arbitrary data local to a Session. The contents of Session.info can be also be initialized using the info argument of Session or sessionmaker.

• [orm] [feature] Removal of event listeners is now implemented. The feature is provided via the event.remove() function.

References: #2268

• [orm] [feature] The mechanism by which attribute events pass along an AttributeImpl as an “initiator” token has been changed; the object is now an event-specific object called attributes.Event. Additionally, the attribute system no longer halts events based on a matching “initiator” token; this logic has been moved to be specific to ORM backref event handlers, which are the typical source of the re-propagation of an attribute event onto subsequent append/set/remove operations. End user code which emulates the behavior of backrefs must now ensure that recursive event propagation schemes are halted, if the scheme does not use the backref handlers. Using this new system, backref handlers can now perform a “two-hop” operation when an object is appended to a collection, associated with a new many-to-one, de-associated with the previous many-to-one, and then removed from a previous collection. Before this change, the last step of removal from the previous collection would not occur.

References: #2789

• [orm] [feature] A major change regarding how the ORM constructs joins where the right side is itself a join or left outer join. The ORM is now configured to allow simple nesting of joins of the form a JOIN (b JOIN c ON b.id=c.id) ON a.id=b.id, rather than forcing the right side into a SELECT subquery. This should allow significant performance improvements on most backends, most particularly MySQL. The one database backend that has for many years held back this change, SQLite, is now addressed by moving the production of the SELECT subquery from the ORM to the SQL compiler; so that a right-nested join on SQLite will still ultimately render with a SELECT, while all other backends are no longer impacted by this workaround.

As part of this change, a new argument flat=True has been added to the orm.aliased(), Join.alias(), and orm.with_polymorphic() functions, which allows an “alias” of a JOIN to be produced which applies an anonymous alias to each component table within the join, rather than producing a subquery.

References: #2587

• [orm] [bug] Fixed bug where using an annotation such as remote() or foreign() on a Column before association with a parent Table could produce issues related to the parent table not rendering within joins, due to the inherent copy operation performed by an annotation.

This change is also backported to: 0.8.3

References: #2813

• [orm] [bug] Fixed bug where Query.exists() failed to work correctly without any WHERE criterion. Courtesy Vladimir Magamedov.

This change is also backported to: 0.8.3

References: #2818

• [orm] [bug] Fixed a potential issue in an ordered sequence implementation used by the ORM to iterate mapper hierarchies; under the Jython interpreter this implementation wasn’t ordered, even though cPython and Pypy maintained ordering.

This change is also backported to: 0.8.3

References: #2794

• [orm] [bug] Fixed bug in ORM-level event registration where the “raw” or “propagate” flags could potentially be mis-configured in some “unmapped base class” configurations.

This change is also backported to: 0.8.3

References: #2786

• [orm] [bug] A performance fix related to the usage of the defer() option when loading mapped entities. The function overhead of applying a per-object deferred callable to an instance at load time was significantly higher than that of just loading the data from the row (note that defer() is meant to reduce DB/network overhead, not necessarily function call count); the function call overhead is now less than that of loading data from the column in all cases. There is also a reduction in the number of “lazy callable” objects created per load from N (total deferred values in the result) to 1 (total number of deferred cols).

This change is also backported to: 0.8.3

References: #2778

• [orm] [bug] Fixed bug whereby attribute history functions would fail when an object we moved from “persistent” to “pending” using the make_transient() function, for operations involving collection-based backrefs.

This change is also backported to: 0.8.3

References: #2773

• [orm] [bug] A warning is emitted when trying to flush an object of an inherited class where the polymorphic discriminator has been assigned to a value that is invalid for the class.

This change is also backported to: 0.8.2

References: #2750

• [orm] [bug] Fixed bug in polymorphic SQL generation where multiple joined-inheritance entities against the same base class joined to each other as well would not track columns on the base table independently of each other if the string of joins were more than two entities long.

This change is also backported to: 0.8.2

References: #2759

• [orm] [bug] Fixed bug where sending a composite attribute into Query.order_by() would produce a parenthesized expression not accepted by some databases.

This change is also backported to: 0.8.2

References: #2754

• [orm] [bug] Fixed the interaction between composite attributes and the aliased() function. Previously, composite attributes wouldn’t work correctly in comparison operations when aliasing was applied.

This change is also backported to: 0.8.2

References: #2755

• [orm] [bug] [ext] Fixed bug where MutableDict didn’t report a change event when clear() was called.

This change is also backported to: 0.8.2

References: #2730

• [orm] [bug] Fixed bug where list instrumentation would fail to represent a setslice of [0:0] correctly, which in particular could occur when using insert(0, item) with the association proxy. Due to some quirk in Python collections, the issue was much more likely with Python 3 rather than 2.

This change is also backported to: 0.8.3, 0.7.11

References: #2807

• [orm] [bug] attributes.get_history() when used with a scalar column-mapped attribute will now honor the “passive” flag passed to it; as this defaults to PASSIVE_OFF, the function will by default query the database if the value is not present. This is a behavioral change vs. 0.8.

References: #2787

• [orm] [bug] [associationproxy] Added additional criterion to the ==, != comparators, used with scalar values, for comparisons to None to also take into account the association record itself being non-present, in addition to the existing test for the scalar endpoint on the association record being NULL. Previously, comparing Cls.scalar == None would return records for which Cls.associated were present and Cls.associated.scalar is None, but not rows for which Cls.associated is non-present. More significantly, the inverse operation Cls.scalar != None would return Cls rows for which Cls.associated was non-present.

The case for Cls.scalar != 'somevalue' is also modified to act more like a direct SQL comparison; only rows for which Cls.associated is present and Associated.scalar is non-NULL and not equal to 'somevalue' are returned. Previously, this would be a simple NOT EXISTS.

Also added a special use case where you can call Cls.scalar.has() with no arguments, when Cls.scalar is a column-based value - this returns whether or not Cls.associated has any rows present, regardless of whether or not Cls.associated.scalar is NULL or not.

References: #2751

• [orm] [bug] Fixed an obscure bug where the wrong results would be fetched when joining/joinedloading across a many-to-many relationship to a single-table-inheriting subclass with a specific discriminator value, due to “secondary” rows that would come back. The “secondary” and right-side tables are now inner joined inside of parenthesis for all ORM joins on many-to-many relationships so that the left->right join can accurately filtered. This change was made possible by finally addressing the issue with right-nested joins outlined in #2587.

References: #2369

• [orm] [bug] The “auto-aliasing” behavior of the Query.select_from() method has been turned off. The specific behavior is now available via a new method Query.select_entity_from(). The auto-aliasing behavior here was never well documented and is generally not what’s desired, as Query.select_from() has become more oriented towards controlling how a JOIN is rendered. Query.select_entity_from() will also be made available in 0.8 so that applications which rely on the auto-aliasing can shift their applications to use this method.

References: #2736

### orm declarative¶

• [feature] [declarative] [orm] Added a convenience class decorator as_declarative(), is a wrapper for declarative_base() which allows an existing base class to be applied using a nifty class-decorated approach.

This change is also backported to: 0.8.3

• [feature] [declarative] [orm] ORM descriptors such as hybrid properties can now be referenced by name in a string argument used with order_by, primaryjoin, or similar in relationship(), in addition to column-bound attributes.

This change is also backported to: 0.8.2

References: #2761

### engine¶

• [engine] [feature] repr() for the URL of an Engine will now conceal the password using asterisks. Courtesy Gunnlaugur Þór Briem.

This change is also backported to: 0.8.3

References: #2821

• [engine] [feature] New events added to ConnectionEvents:

References: #2770

• [engine] [bug] [oracle] Dialect.initialize() is not called a second time if an Engine is recreated, due to a disconnect error. This fixes a particular issue in the Oracle 8 dialect, but in general the dialect.initialize() phase should only be once per dialect.

This change is also backported to: 0.8.3

References: #2776

• [engine] [bug] [pool] Fixed bug where QueuePool would lose the correct checked out count if an existing pooled connection failed to reconnect after an invalidate or recycle event.

This change is also backported to: 0.8.3

References: #2772

• [engine] [bug] Fixed bug where the reset_on_return argument to various Pool implementations would not be propagated when the pool was regenerated. Courtesy Eevee.

This change is also backported to: 0.8.2

References: pull request github:6

• [engine] [bug] The regexp used by the make_url() function now parses ipv6 addresses, e.g. surrounded by brackets.

This change is also backported to: 0.8.3, 0.7.11

References: #2851

• [engine] [bug] The method signature of Dialect.reflecttable(), which in all known cases is provided by DefaultDialect, has been tightened to expect include_columns and exclude_columns arguments without any kw option, reducing ambiguity - previously exclude_columns was missing.

References: #2748

### sql¶

• [sql] [feature] Added support for “unique constraint” reflection, via the Inspector.get_unique_constraints() method. Thanks for Roman Podolyaka for the patch.

This change is also backported to: 0.8.4

References: #1443

• [sql] [feature] The update(), insert(), and delete() constructs will now interpret ORM entities as target tables to be operated upon, e.g.:

from sqlalchemy import insert, update, delete

ins = insert(SomeMappedClass).values(x=5)

del_ = delete(SomeMappedClass).where(SomeMappedClass.id == 5)

upd = update(SomeMappedClass).where(SomeMappedClass.id == 5).values(name='ed')

This change is also backported to: 0.8.3

• [sql] [feature] [mysql] [postgresql] The PostgreSQL and MySQL dialects now support reflection/inspection of foreign key options, including ON UPDATE, ON DELETE. PostgreSQL also reflects MATCH, DEFERRABLE, and INITIALLY. Coutesy ijl.

References: #2183

• [sql] [feature] A bindparam() construct with a “null” type (e.g. no type specified) is now copied when used in a typed expression, and the new copy is assigned the actual type of the compared column. Previously, this logic would occur on the given bindparam() in place. Additionally, a similar process now occurs for bindparam() constructs passed to ValuesBase.values() for an Insert or Update construct, within the compilation phase of the construct.

These are both subtle behavioral changes which may impact some usages.

References: #2850

• [sql] [feature] An overhaul of expression handling for special symbols particularly with conjunctions, e.g. None expression.null() expression.true() expression.false(), including consistency in rendering NULL in conjunctions, “short-circuiting” of and_() and or_() expressions which contain boolean constants, and rendering of boolean constants and expressions as compared to “1” or “0” for backends that don’t feature true/false constants.

References: #2734, #2804, #2823

• [sql] [feature] The typing system now handles the task of rendering “literal bind” values, e.g. values that are normally bound parameters but due to context must be rendered as strings, typically within DDL constructs such as CHECK constraints and indexes (note that “literal bind” values become used by DDL as of #2742). A new method TypeEngine.literal_processor() serves as the base, and TypeDecorator.process_literal_param() is added to allow wrapping of a native literal rendering method.

References: #2838

• [sql] [feature] The Table.tometadata() method now produces copies of all SchemaItem.info dictionaries from all SchemaItem objects within the structure including columns, constraints, foreign keys, etc. As these dictionaries are copies, they are independent of the original dictionary. Previously, only the .info dictionary of Column was transferred within this operation, and it was only linked in place, not copied.

References: #2716

• [sql] [feature] The default argument of Column now accepts a class or object method as an argument, in addition to a standalone function; will properly detect if the “context” argument is accepted or not.

• [sql] [feature] Added new method to the insert() construct Insert.from_select(). Given a list of columns and a selectable, renders INSERT INTO (table) (columns) SELECT ... While this feature is highlighted as part of 0.9 it is also backported to 0.8.3.

References: #722

• [sql] [feature] Provided a new attribute for TypeDecorator called TypeDecorator.coerce_to_is_types, to make it easier to control how comparisons using == or != to None and boolean types goes about producing an IS expression, or a plain equality expression with a bound parameter.

References: #2734, #2744

• [sql] [feature] A label() construct will now render as its name alone in an ORDER BY clause, if that label is also referred to in the columns clause of the select, instead of rewriting the full expression. This gives the database a better chance to optimize the evaluation of the same expression in two different contexts.

References: #1068

• [sql] [bug] Fixed bug where type_coerce() would not interpret ORM elements with a __clause_element__() method properly.

This change is also backported to: 0.8.3

References: #2849

• [sql] [bug] The Enum and Boolean types now bypass any custom (e.g. TypeDecorator) type in use when producing the CHECK constraint for the “non native” type. This so that the custom type isn’t involved in the expression within the CHECK, since this expression is against the “impl” value and not the “decorated” value.

This change is also backported to: 0.8.3

References: #2842

• [sql] [bug] The .unique flag on Index could be produced as None if it was generated from a Column that didn’t specify unique (where it defaults to None). The flag will now always be True or False.

This change is also backported to: 0.8.3

References: #2825

• [sql] [bug] Fixed bug in default compiler plus those of postgresql, mysql, and mssql to ensure that any literal SQL expression values are rendered directly as literals, instead of as bound parameters, within a CREATE INDEX statement. This also changes the rendering scheme for other DDL such as constraints.

This change is also backported to: 0.8.3

References: #2742

• [sql] [bug] A select() that is made to refer to itself in its FROM clause, typically via in-place mutation, will raise an informative error message rather than causing a recursion overflow.

This change is also backported to: 0.8.3

References: #2815

• [sql] [bug] Fixed bug where using the column_reflect event to change the .key of the incoming Column would prevent primary key constraints, indexes, and foreign key constraints from being correctly reflected.

This change is also backported to: 0.8.3

References: #2811

• [sql] [bug] The ColumnOperators.notin_() operator added in 0.8 now properly produces the negation of the expression “IN” returns when used against an empty collection.

This change is also backported to: 0.8.3

• [sql] [bug] [postgresql] Fixed bug where the expression system relied upon the str() form of a some expressions when referring to the .c collection on a select() construct, but the str() form isn’t available since the element relies on dialect-specific compilation constructs, notably the __getitem__() operator as used with a PostgreSQL ARRAY element. The fix also adds a new exception class UnsupportedCompilationError which is raised in those cases where a compiler is asked to compile something it doesn’t know how to.

This change is also backported to: 0.8.3

References: #2780

• [sql] [bug] Multiple fixes to the correlation behavior of Select constructs, first introduced in 0.8.0:

• To satisfy the use case where FROM entries should be correlated outwards to a SELECT that encloses another, which then encloses this one, correlation now works across multiple levels when explicit correlation is established via Select.correlate(), provided that the target select is somewhere along the chain contained by a WHERE/ORDER BY/columns clause, not just nested FROM clauses. This makes Select.correlate() act more compatibly to that of 0.7 again while still maintaining the new “smart” correlation.
• When explicit correlation is not used, the usual “implicit” correlation limits its behavior to just the immediate enclosing SELECT, to maximize compatibility with 0.7 applications, and also prevents correlation across nested FROMs in this case, maintaining compatibility with 0.8.0/0.8.1.
• The Select.correlate_except() method was not preventing the given FROM clauses from correlation in all cases, and also would cause FROM clauses to be incorrectly omitted entirely (more like what 0.7 would do), this has been fixed.
• Calling select.correlate_except(None) will enter all FROM clauses into correlation as would be expected.

This change is also backported to: 0.8.2

References: #2668, #2746

• [sql] [bug] Fixed bug whereby joining a select() of a table “A” with multiple foreign key paths to a table “B”, to that table “B”, would fail to produce the “ambiguous join condition” error that would be reported if you join table “A” directly to “B”; it would instead produce a join condition with multiple criteria.

This change is also backported to: 0.8.2

References: #2738

• [sql] [bug] [reflection] Fixed bug whereby using MetaData.reflect() across a remote schema as well as a local schema could produce wrong results in the case where both schemas had a table of the same name.

This change is also backported to: 0.8.2

References: #2728

• [sql] [bug] Removed the “not implemented” __iter__() call from the base ColumnOperators class, while this was introduced in 0.8.0 to prevent an endless, memory-growing loop when one also implements a __getitem__() method on a custom operator and then calls erroneously list() on that object, it had the effect of causing column elements to report that they were in fact iterable types which then throw an error when you try to iterate. There’s no real way to have both sides here so we stick with Python best practices. Careful with implementing __getitem__() on your custom operators!

This change is also backported to: 0.8.2

References: #2726

• [sql] [bug] Fixed regression dating back to 0.7.9 whereby the name of a CTE might not be properly quoted if it was referred to in multiple FROM clauses.

This change is also backported to: 0.8.3, 0.7.11

References: #2801

• [sql] [bug] [cte] Fixed bug in common table expression system where if the CTE were used only as an alias() construct, it would not render using the WITH keyword.

This change is also backported to: 0.8.3, 0.7.11

References: #2783

• [sql] [bug] Fixed bug in CheckConstraint DDL where the “quote” flag from a Column object would not be propagated.

This change is also backported to: 0.8.3, 0.7.11

References: #2784

• [sql] [bug] The “name” attribute is set on Index before the “attach” events are called, so that attachment events can be used to dynamically generate a name for the index based on the parent table and/or columns.

References: #2835

• [sql] [bug] The erroneous kw arg “schema” has been removed from the ForeignKey object. this was an accidental commit that did nothing; a warning is raised in 0.8.3 when this kw arg is used.

References: #2831

• [sql] [bug] A rework to the way that “quoted” identifiers are handled, in that instead of relying upon various quote=True flags being passed around, these flags are converted into rich string objects with quoting information included at the point at which they are passed to common schema constructs like Table, Column, etc. This solves the issue of various methods that don’t correctly honor the “quote” flag such as Engine.has_table() and related methods. The quoted_name object is a string subclass that can also be used explicitly if needed; the object will hold onto the quoting preferences passed and will also bypass the “name normalization” performed by dialects that standardize on uppercase symbols, such as Oracle, Firebird and DB2. The upshot is that the “uppercase” backends can now work with force-quoted names, such as lowercase-quoted names and new reserved words.

References: #2812

• [sql] [bug] The resolution of ForeignKey objects to their target Column has been reworked to be as immediate as possible, based on the moment that the target Column is associated with the same MetaData as this ForeignKey, rather than waiting for the first time a join is constructed, or similar. This along with other improvements allows earlier detection of some foreign key configuration issues. Also included here is a rework of the type-propagation system, so that it should be reliable now to set the type as None on any Column that refers to another via ForeignKey - the type will be copied from the target column as soon as that other column is associated, and now works for composite foreign keys as well.

References: #1765

### postgresql¶

• [postgresql] [feature] Support for PostgreSQL 9.2 range types has been added. Currently, no type translation is provided, so works directly with strings or psycopg2 2.5 range extension types at the moment. Patch courtesy Chris Withers.

This change is also backported to: 0.8.2

• [postgresql] [feature] Added support for “AUTOCOMMIT” isolation when using the psycopg2 DBAPI. The keyword is available via the isolation_level execution option. Patch courtesy Roman Podolyaka.

This change is also backported to: 0.8.2

References: #2072

• [postgresql] [feature] Added support for rendering SMALLSERIAL when a SmallInteger type is used on a primary key autoincrement column, based on server version detection of PostgreSQL version 9.2 or greater.

References: #2840

• [postgresql] [bug] Removed a 128-character truncation from the reflection of the server default for a column; this code was original from PG system views which truncated the string for readability.

This change is also backported to: 0.8.3

References: #2844

• [postgresql] [bug] Parenthesis will be applied to a compound SQL expression as rendered in the column list of a CREATE INDEX statement.

This change is also backported to: 0.8.3

References: #2742

• [postgresql] [bug] Fixed bug where PostgreSQL version strings that had a prefix preceding the words “PostgreSQL” or “EnterpriseDB” would not parse. Courtesy Scott Schaefer.

This change is also backported to: 0.8.3

References: #2819

• [postgresql] [bug] The behavior of extract() has been simplified on the PostgreSQL dialect to no longer inject a hardcoded ::timestamp or similar cast into the given expression, as this interfered with types such as timezone-aware datetimes, but also does not appear to be at all necessary with modern versions of psycopg2.

This change is also backported to: 0.8.2

References: #2740

• [postgresql] [bug] Fixed bug in HSTORE type where keys/values that contained backslashed quotes would not be escaped correctly when using the “non native” (i.e. non-psycopg2) means of translating HSTORE data. Patch courtesy Ryan Kelly.

This change is also backported to: 0.8.2

References: #2766

• [postgresql] [bug] Fixed bug where the order of columns in a multi-column PostgreSQL index would be reflected in the wrong order. Courtesy Roman Podolyaka.

This change is also backported to: 0.8.2

References: #2767

### mysql¶

• [mysql] [feature] The mysql_length parameter used with Index can now be passed as a dictionary of column names/lengths, for use with composite indexes. Big thanks to Roman Podolyaka for the patch.

This change is also backported to: 0.8.2

References: #2704

• [mysql] [feature] The MySQL mysql.SET type now features the same auto-quoting behavior as that of mysql.ENUM. Quotes are not required when setting up the value, but quotes that are present will be auto-detected along with a warning. This also helps with Alembic where the SET type doesn’t render with quotes.

References: #2817

• [mysql] [bug] The change in #2721, which is that the deferrable keyword of ForeignKeyConstraint is silently ignored on the MySQL backend, will be reverted as of 0.9; this keyword will now render again, raising errors on MySQL as it is not understood - the same behavior will also apply to the initially keyword. In 0.8, the keywords will remain ignored but a warning is emitted. Additionally, the match keyword now raises a CompileError on 0.9 and emits a warning on 0.8; this keyword is not only silently ignored by MySQL but also breaks the ON UPDATE/ON DELETE options.

To use a ForeignKeyConstraint that does not render or renders differently on MySQL, use a custom compilation option. An example of this usage has been added to the documentation, see MySQL Foreign Keys.

This change is also backported to: 0.8.3

References: #2721, #2839

• [mysql] [bug] MySQL-connector dialect now allows options in the create_engine query string to override those defaults set up in the connect, including “buffered” and “raise_on_warnings”.

This change is also backported to: 0.8.3

References: #2515

• [mysql] [bug] Fixed bug when using multi-table UPDATE where a supplemental table is a SELECT with its own bound parameters, where the positioning of the bound parameters would be reversed versus the statement itself when using MySQL’s special syntax.

This change is also backported to: 0.8.2

References: #2768

• [mysql] [bug] Added another conditional to the mysql+gaerdbms dialect to detect so-called “development” mode, where we should use the rdbms_mysqldb DBAPI. Patch courtesy Brett Slatkin.

This change is also backported to: 0.8.2

References: #2715

• [mysql] [bug] The deferrable keyword argument on ForeignKey and ForeignKeyConstraint will not render the DEFERRABLE keyword on the MySQL dialect. For a long time we left this in place because a non-deferrable foreign key would act very differently than a deferrable one, but some environments just disable FKs on MySQL, so we’ll be less opinionated here.

This change is also backported to: 0.8.2

References: #2721

• [mysql] [bug] Updates to MySQL reserved words for versions 5.5, 5.6, courtesy Hanno Schlichting.

This change is also backported to: 0.8.3, 0.7.11

References: #2791

• [mysql] [bug] Fix and test parsing of MySQL foreign key options within reflection; this complements the work in #2183 where we begin to support reflection of foreign key options such as ON UPDATE/ON DELETE cascade.

References: #2839

• [mysql] [bug] Improved support for the cymysql driver, supporting version 0.6.5, courtesy Hajime Nakagami.

### sqlite¶

• [sqlite] [bug] The newly added SQLite DATETIME arguments storage_format and regexp apparently were not fully implemented correctly; while the arguments were accepted, in practice they would have no effect; this has been fixed.

This change is also backported to: 0.8.3

References: #2781

• [sqlite] [bug] Added sqlalchemy.types.BIGINT to the list of type names that can be reflected by the SQLite dialect; courtesy Russell Stuart.

This change is also backported to: 0.8.2

References: #2764

### mssql¶

• [mssql] [bug] When querying the information schema on SQL Server 2000, removed a CAST call that was added in 0.8.1 to help with driver issues, which apparently is not compatible on 2000. The CAST remains in place for SQL Server 2005 and greater.

This change is also backported to: 0.8.2

References: #2747

• [mssql] [bug] [pyodbc] Fixes to MSSQL with Python 3 + pyodbc, including that statements are passed correctly.

References: #2355

### oracle¶

• [oracle] [feature] [py3k] The Oracle unit tests with cx_oracle now pass fully under Python 3.

• [oracle] [bug] Fixed bug where Oracle table reflection using synonyms would fail if the synonym and the table were in different remote schemas. Patch to fix courtesy Kyle Derr.

This change is also backported to: 0.8.3

References: #2853

### firebird¶

• [firebird] [feature] Added new flag retaining=True to the kinterbasdb and fdb dialects. This controls the value of the retaining flag sent to the commit() and rollback() methods of the DBAPI connection. Due to historical concerns, this flag defaults to True in 0.8.2, however in 0.9.0b1 this flag defaults to False.

This change is also backported to: 0.8.2

References: #2763

• [firebird] [feature] The fdb dialect is now the default dialect when specified without a dialect qualifier, i.e. firebird://, per the Firebird project publishing fdb as their official Python driver.

References: #2504

• [firebird] [bug] Type lookup when reflecting the Firebird types LONG and INT64 has been fixed so that LONG is treated as INTEGER, INT64 treated as BIGINT, unless the type has a “precision” in which case it’s treated as NUMERIC. Patch courtesy Russell Stuart.

This change is also backported to: 0.8.2

References: #2757

### misc¶

• [feature] Added a new flag system=True to Column, which marks the column as a “system” column which is automatically made present by the database (such as PostgreSQL oid or xmin). The column will be omitted from the CREATE TABLE statement but will otherwise be available for querying. In addition, the CreateColumn construct can be appled to a custom compilation rule which allows skipping of columns, by producing a rule that returns None.

This change is also backported to: 0.8.3

• [feature] [examples] Improved the examples in examples/generic_associations, including that discriminator_on_association.py makes use of single table inheritance do the work with the “discriminator”. Also added a true “generic foreign key” example, which works similarly to other popular frameworks in that it uses an open-ended integer to point to any other table, foregoing traditional referential integrity. While we don’t recommend this pattern, information wants to be free.

This change is also backported to: 0.8.3

• [feature] [core] Added a new variant to UpdateBase.returning() called ValuesBase.return_defaults(); this allows arbitrary columns to be added to the RETURNING clause of the statement without interfering with the compilers usual “implicit returning” feature, which is used to efficiently fetch newly generated primary key values. For supporting backends, a dictionary of all fetched values is present at ResultProxy.returned_defaults.

References: #2793

• [feature] [pool] Added pool logging for “rollback-on-return” and the less used “commit-on-return”. This is enabled with the rest of pool “debug” logging.

References: #2752

• [bug] [examples] Added “autoincrement=False” to the history table created in the versioning example, as this table shouldn’t have autoinc on it in any case, courtesy Patrick Schmid.

This change is also backported to: 0.8.3

• [bug] [ext] Fixed bug whereby if a composite type were set up with a function instead of a class, the mutable extension would trip up when it tried to check that column for being a MutableComposite (which it isn’t). Courtesy asldevi.

This change is also backported to: 0.8.2

• [bug] [examples] Fixed an issue with the “versioning” recipe whereby a many-to-one reference could produce a meaningless version for the target, even though it was not changed, when backrefs were present. Patch courtesy Matt Chisholm.

This change is also backported to: 0.8.2

• [requirements] The Python mock library is now required in order to run the unit test suite. While part of the standard library as of Python 3.3, previous Python installations will need to install this in order to run unit tests or to use the sqlalchemy.testing package for external dialects.

This change is also backported to: 0.8.2

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