Release: 1.4.39 | Release Date: June 24, 2022

# SQLAlchemy 1.4 Documentation

# 0.7 Changelog

## 0.7.11

no release date

### orm

- [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.

  References: #2807

- [orm] [bug]

  Fixed bug when a query of the form: `query(SubClass).options(subqueryload(Baseclass.attrname))`, where `SubClass` is a joined inh of `BaseClass`, would fail to apply the `JOIN` inside the subquery on the attribute load, producing a cartesian product. The populated results still tended to be correct as additional rows are just ignored, so this issue may be present as a performance degradation in applications that are otherwise working correctly.

  References: #2699

- [orm] [bug]

  Fixed bug in unit of work whereby a joined-inheritance subclass could insert the row for the “sub” table before the parent table, if the two tables had no ForeignKey constraints set up between them.

  References: #2689

- [orm] [bug]

  Improved the error message emitted when a “backref loop” is detected, that is when an attribute event triggers a bidirectional assignment between two other attributes with no end. This condition can occur not just when an object of the wrong type is assigned, but also when an attribute is mis-configured to backref into an existing backref pair.

  References: #2674

- [orm] [bug]

  A warning is emitted when a MapperProperty is assigned to a mapper that replaces an existing property, if the properties in question aren’t plain column-based properties. Replacement of relationship properties is rarely (ever?) what is intended and usually refers to a mapper mis-configuration. This will also warn if a backref configures itself on top of an existing one in an inheritance relationship (which is an error in 0.8).

  References: #2674

### engine

- [engine] [bug]

  The regexp used by the `make_url()` function now parses ipv6 addresses, e.g. surrounded by brackets.

  References: #2851

### sql

- [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.

  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.

  References: #2783

- [sql] [bug]

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

  References: #2784

### postgresql

- [postgresql] [feature]

  Added support for PostgreSQL’s traditional SUBSTRING function syntax, renders as “SUBSTRING(x FROM y FOR z)” when regular `func.substring()` is used. Courtesy Gunnlaugur Þór Briem.

  References: #2676

### mysql

- [mysql] [bug]

  Updates to MySQL reserved words for versions 5.5, 5.6, courtesy Hanno Schlichting.

  References: #2791

### tests

- [tests] [bug]

  Fixed an import of “logging” in test_execute which was not working on some linux platforms.

  References: #2669, pull request 41

## 0.7.10

Released: Thu Feb 7 2013

### orm

- [orm] [bug]

  Fixed potential memory leak which could occur if an arbitrary number of `sessionmaker` objects were created. The anonymous subclass created by the sessionmaker, when dereferenced, would not be garbage collected due to remaining class-level references from the event package. This issue also applies to any custom system that made use of ad-hoc subclasses in conjunction with an event dispatcher.

  References: #2650

- [orm] [bug]

  `Query.merge_result()` can now load rows from an outer join where an entity may be `None` without throwing an error.

  References: #2640

- [orm] [bug]

  The `MutableComposite` type did not allow for the `MutableBase.coerce()` method to be used, even though the code seemed to indicate this intent, so this now works and a brief example is added. As a side-effect, the mechanics of this event handler have been changed so that new `MutableComposite` types no longer add per-type global event handlers. Also in 0.8.0b2.

  References: #2624

- [orm] [bug]

  Fixed Session accounting bug whereby replacing a deleted object in the identity map with another object of the same primary key would raise a “conflicting state” error on rollback(), if the replaced primary key were established either via non-unitofwork-established INSERT statement or by primary key switch of another instance.

  References: #2583

### engine

- [engine] [bug]

  Fixed `MetaData.reflect()` to correctly use the given `Connection`, if given, without opening a second connection from that connection’s `Engine`.

  References: #2604

### sql

- [sql] [bug]

  Backported adjustment to `__repr__` for `TypeDecorator` to 0.7, allows `PickleType` to produce a clean `repr()` to help with Alembic.

  References: #2584, #2594

- [sql] [bug]

  Fixed bug where `Table.tometadata()` would fail if a `Column` had both a foreign key as well as an alternate “.key” name for the column.

  References: #2643

- [sql] [bug]

  Fixed bug where using server_onupdate=<FetchedValue|DefaultClause> without passing the “for_update=True” flag would apply the default object to the server_default, blowing away whatever was there. The explicit for_update=True argument shouldn’t be needed with this usage (especially since the documentation shows an example without it being used) so it is now arranged internally using a copy of the given default object, if the flag isn’t set to what corresponds to that argument.

  References: #2631

- [sql] [gae] [mysql]

  Added a conditional import to the `gaerdbms` dialect which attempts to import rdbms_apiproxy vs. rdbms_googleapi to work on both dev and production platforms. Also now honors the `instance` attribute. Courtesy Sean Lynch. Also backported enhancements to allow username/password as well as fixing error code interpretation from 0.8.

  References: #2649

### mysql

- [mysql] [feature]

  Added “raise_on_warnings” flag to OurSQL dialect.

  References: #2523

- [mysql] [feature]

  Added “read_timeout” flag to MySQLdb dialect.

  References: #2554

### sqlite

- [sqlite] [bug]

  More adjustment to this SQLite related issue which was released in 0.7.9, to intercept legacy SQLite quoting characters when reflecting foreign keys. In addition to intercepting double quotes, other quoting characters such as brackets, backticks, and single quotes are now also intercepted.

  References: #2568

### mssql

- [mssql] [bug]

  Fixed bug whereby using “key” with Column in conjunction with “schema” for the owning Table would fail to locate result rows due to the MSSQL dialect’s “schema rendering” logic’s failure to take .key into account.

- [mssql] [bug]

  Added a Py3K conditional around unnecessary .decode() call in mssql information schema, fixes reflection in Py3k.

  References: #2638

### oracle

- [oracle] [bug]

  The Oracle LONG type, while an unbounded text type, does not appear to use the cx_Oracle.LOB type when result rows are returned, so the dialect has been repaired to exclude LONG from having cx_Oracle.LOB filtering applied.

  References: #2620

- [oracle] [bug]

  Repaired the usage of `.prepare()` in conjunction with cx_Oracle so that a return value of `False` will result in no call to `connection.commit()`, hence avoiding “no transaction” errors. Two-phase transactions have now been shown to work in a rudimental fashion with SQLAlchemy and cx_oracle, however are subject to caveats observed with the driver; check the documentation for details.

  References: #2611

- [oracle] [bug]

  changed the list of cx_oracle types that are excluded from the setinputsizes() step to only include STRING and UNICODE; CLOB and NCLOB are removed. This is to work around cx_oracle behavior which is broken for the executemany() call. In 0.8, this same change is applied however it is also configurable via the exclude_setinputsizes argument.

  References: #2561

## 0.7.9

Released: Mon Oct 01 2012

### orm

- [orm] [bug]

  Fixed bug mostly local to new AbstractConcreteBase helper where the “type” attribute from the superclass would not be overridden on the subclass to produce the “reserved for base” error message, instead placing a do-nothing attribute there. This was inconsistent vs. using ConcreteBase as well as all the behavior of classical concrete mappings, where the “type” column from the polymorphic base would be explicitly disabled on subclasses, unless overridden explicitly.

- [orm] [bug]

  A warning is emitted when lazy=’dynamic’ is combined with uselist=False. This is an exception raise in 0.8.

- [orm] [bug]

  Fixed bug whereby user error in related-object assignment could cause recursion overflow if the assignment triggered a backref of the same name as a bi-directional attribute on the incorrect class to the same target. An informative error is raised now.

- [orm] [bug]

  Fixed bug where incorrect type information would be passed when the ORM would bind the “version” column, when using the “version” feature. Tests courtesy Daniel Miller.

  References: #2539

- [orm] [bug]

  Extra logic has been added to the “flush” that occurs within Session.commit(), such that the extra state added by an after_flush() or after_flush_postexec() hook is also flushed in a subsequent flush, before the “commit” completes. Subsequent calls to flush() will continue until the after_flush hooks stop adding new state. An “overflow” counter of 100 is also in place, in the event of a broken after_flush() hook adding new content each time.

  References: #2566

### engine

- [engine] [feature]

  Dramatic improvement in memory usage of the event system; instance-level collections are no longer created for a particular type of event until instance-level listeners are established for that event.

  References: #2516

- [engine] [bug]

  Fixed bug whereby a disconnect detect + dispose that occurs when the QueuePool has threads waiting for connections would leave those threads waiting for the duration of the timeout on the old pool (or indefinitely if timeout was disabled). The fix now notifies those waiters with a special exception case and has them move onto the new pool.

  References: #2522

- [engine] [bug]

  Added gaerdbms import to mysql/__init__.py, the absence of which was preventing the new GAE dialect from being loaded.

  References: #2529

- [engine] [bug]

  Fixed cextension bug whereby the “ambiguous column error” would fail to function properly if the given index were a Column object and not a string. Note there are still some column-targeting issues here which are fixed in 0.8.

  References: #2553

- [engine] [bug]

  Fixed the repr() of Enum to include the “name” and “native_enum” flags. Helps Alembic autogenerate.

### sql

- [sql] [bug]

  Fixed the DropIndex construct to support an Index associated with a Table in a remote schema.

  References: #2571

- [sql] [bug]

  Fixed bug in over() construct whereby passing an empty list for either partition_by or order_by, as opposed to None, would fail to generate correctly. Courtesy Gunnlaugur Þór Briem.

  References: #2574

- [sql] [bug]

  Fixed CTE bug whereby positional bound parameters present in the CTEs themselves would corrupt the overall ordering of bound parameters. This primarily affected SQL Server as the platform with positional binds + CTE support.

  References: #2521

- [sql] [bug]

  Fixed more un-intuitivenesses in CTEs which prevented referring to a CTE in a union of itself without it being aliased. CTEs now render uniquely on name, rendering the outermost CTE of a given name only - all other references are rendered just as the name. This even includes other CTE/SELECTs that refer to different versions of the same CTE object, such as a SELECT or a UNION ALL of that SELECT. We are somewhat loosening the usual link between object identity and lexical identity in this case. A true name conflict between two unrelated CTEs now raises an error.

- [sql] [bug]

  quoting is applied to the column names inside the WITH RECURSIVE clause of a common table expression according to the quoting rules for the originating Column.

  References: #2512

- [sql] [bug]

  Fixed regression introduced in 0.7.6 whereby the FROM list of a SELECT statement could be incorrect in certain “clone+replace” scenarios.

  References: #2518

- [sql] [bug]

  Fixed bug whereby usage of a UNION or similar inside of an embedded subquery would interfere with result-column targeting, in the case that a result-column had the same ultimate name as a name inside the embedded UNION.

  References: #2552

- [sql] [bug]

  Fixed a regression since 0.6 regarding result-row targeting. It should be possible to use a select() statement with string based columns in it, that is select([‘id’, ‘name’]).select_from(‘mytable’), and have this statement be targetable by Column objects with those names; this is the mechanism by which query(MyClass).from_statement(some_statement) works. At some point the specific case of using select([‘id’]), which is equivalent to select([literal_column(‘id’)]), stopped working here, so this has been re-instated and of course tested.

  References: #2558

- [sql] [bug]

  Added missing operators is_(), isnot() to the ColumnOperators base, so that these long-available operators are present as methods like all the other operators.

  References: #2544

### postgresql

- [postgresql] [bug]

  Columns in reflected primary key constraint are now returned in the order in which the constraint itself defines them, rather than how the table orders them. Courtesy Gunnlaugur Þór Briem..

  References: #2531

- [postgresql] [bug]

  Added ‘terminating connection’ to the list of messages we use to detect a disconnect with PG, which appears to be present in some versions when the server is restarted.

  References: #2570

### mysql

- [mysql] [bug]

  Updated mysqlconnector interface to use updated “client flag” and “charset” APIs, courtesy David McNelis.

### sqlite

- [sqlite] [feature]

  Added support for the localtimestamp() SQL function implemented in SQLite, courtesy Richard Mitchell.

- [sqlite] [bug]

  Adjusted a very old bugfix which attempted to work around a SQLite issue that itself was “fixed” as of sqlite 3.6.14, regarding quotes surrounding a table name when using the “foreign_key_list” pragma. The fix has been adjusted to not interfere with quotes that are actually in the name of a column or table, to as much a degree as possible; sqlite still doesn’t return the correct result for foreign_key_list() if the target table actually has quotes surrounding its name, as part of its name (i.e. “””mytable”””).

  References: #2568

- [sqlite] [bug]

  Adjusted column default reflection code to convert non-string values to string, to accommodate old SQLite versions that don’t deliver default info as a string.

  References: #2265

### mssql

- [mssql] [bug]

  Fixed compiler bug whereby using a correlated subquery within an ORDER BY would fail to render correctly if the statement also used LIMIT/OFFSET, due to mis-rendering within the ROW_NUMBER() OVER clause. Fix courtesy sayap

  References: #2538

- [mssql] [bug]

  Fixed compiler bug whereby a given select() would be modified if it had an “offset” attribute, causing the construct to not compile correctly a second time.

  References: #2545

- [mssql] [bug]

  Fixed bug where reflection of primary key constraint would double up columns if the same constraint/table existed in multiple schemas.

## 0.7.8

Released: Sat Jun 16 2012

### orm

- [orm] [feature]

  The ‘objects’ argument to flush() is no longer deprecated, as some valid use cases have been identified.

- [orm] [bug]

  Fixed bug whereby subqueryload() from a polymorphic mapping to a target would incur a new invocation of the query for each distinct class encountered in the polymorphic result.

  References: #2480

- [orm] [bug]

  Fixed bug in declarative whereby the precedence of columns in a joined-table, composite column (typically for id) would fail to be correct if the columns contained names distinct from their attribute names. This would cause things like primaryjoin conditions made against the entity attributes to be incorrect. Related to as this was supposed to be part of that, this is.

  References: #1892, #2491

- [orm] [bug]

  Fixed identity_key() function which was not accepting a scalar argument for the identity. .

  References: #2508

- [orm] [bug]

  Fixed bug whereby populate_existing option would not propagate to subquery eager loaders. .

  References: #2497

### engine

- [engine] [bug]

  Fixed memory leak in C version of result proxy whereby DBAPIs which don’t deliver pure Python tuples for result rows would fail to decrement refcounts correctly. The most prominently affected DBAPI is pyodbc.

  References: #2489

- [engine] [bug]

  Fixed bug affecting Py3K whereby string positional parameters passed to engine/connection execute() would fail to be interpreted correctly, due to __iter__ being present on Py3K string..

  References: #2503

### sql

- [sql] [bug]

  added BIGINT to types.__all__, BIGINT, BINARY, VARBINARY to sqlalchemy module namespace, plus test to ensure this breakage doesn’t occur again.

  References: #2499

- [sql] [bug]

  Repaired common table expression rendering to function correctly when the SELECT statement contains UNION or other compound expressions, courtesy btbuilder.

  References: #2490

- [sql] [bug]

  Fixed bug whereby append_column() wouldn’t function correctly on a cloned select() construct, courtesy Gunnlaugur Þór Briem.

  References: #2482

### postgresql

- [postgresql] [bug]

  removed unnecessary table clause when reflecting enums,. Courtesy Gunnlaugur Þór Briem.

  References: #2510

### mysql

- [mysql] [feature]

  Added a new dialect for Google App Engine. Courtesy Richie Foreman.

  References: #2484

### oracle

- [oracle] [bug]

  Added ROWID to oracle.*.

  References: #2483

## 0.7.7

Released: Sat May 05 2012

### orm

- [orm] [feature]

  Added prefix_with() method to Query, calls upon select().prefix_with() to allow placement of MySQL SELECT directives in statements. Courtesy Diana Clarke

  References: #2443

- [orm] [feature]

  Added new flag to @validates include_removes. When True, collection remove and attribute del events will also be sent to the validation function, which accepts an additional argument “is_remove” when this flag is used.

- [orm] [bug]

  Fixed issue in unit of work whereby setting a non-None self-referential many-to-one relationship to None would fail to persist the change if the former value was not already loaded..

  References: #2477

- [orm] [bug]

  Fixed bug in 0.7.6 introduced by whereby column_mapped_collection used against columns that were mapped as joins or other indirect selectables would fail to function.

  References: #2409

- [orm] [bug]

  Fixed bug whereby polymorphic_on column that’s not otherwise mapped on the class would be incorrectly included in a merge() operation, raising an error.

  References: #2449

- [orm] [bug]

  Fixed bug in expression annotation mechanics which could lead to incorrect rendering of SELECT statements with aliases and joins, particularly when using column_property().

  References: #2453

- [orm] [bug]

  Fixed bug which would prevent OrderingList from being pickleable. Courtesy Jeff Dairiki

  References: #2454

- [orm] [bug]

  Fixed bug in relationship comparisons whereby calling unimplemented methods like SomeClass.somerelationship.like() would produce a recursion overflow, instead of NotImplementedError.

### sql

- [sql] [feature]

  Added new connection event dbapi_error(). Is called for all DBAPI-level errors passing the original DBAPI exception before SQLAlchemy modifies the state of the cursor.

- [sql] [bug]

  Removed warning when Index is created with no columns; while this might not be what the user intended, it is a valid use case as an Index could be a placeholder for just an index of a certain name.

- [sql] [bug]

  If conn.begin() fails when calling “with engine.begin()”, the newly acquired Connection is closed explicitly before propagating the exception onward normally.

- [sql] [bug]

  Add BINARY, VARBINARY to types.__all__.

  References: #2474

### postgresql

- [postgresql] [feature]

  Added new for_update/with_lockmode() options for PostgreSQL: for_update=”read”/ with_lockmode(“read”), for_update=”read_nowait”/ with_lockmode(“read_nowait”). These emit “FOR SHARE” and “FOR SHARE NOWAIT”, respectively. Courtesy Diana Clarke

  References: #2445

- [postgresql] [bug]

  removed unnecessary table clause when reflecting domains.

  References: #2473

### mysql

- [mysql] [bug]

  Fixed bug whereby column name inside of “KEY” clause for autoincrement composite column with InnoDB would double quote a name that’s a reserved word. Courtesy Jeff Dairiki.

  References: #2460

- [mysql] [bug]

  Fixed bug whereby get_view_names() for “information_schema” schema would fail to retrieve views marked as “SYSTEM VIEW”. courtesy Matthew Turland.

- [mysql] [bug]

  Fixed bug whereby if cast() is used on a SQL expression whose type is not supported by cast() and therefore CAST isn’t rendered by the dialect, the order of evaluation could change if the casted expression required that it be grouped; grouping is now applied to those expressions.

  References: #2467

### sqlite

- [sqlite] [feature]

  Added SQLite execution option “sqlite_raw_colnames=True”, will bypass attempts to remove “.” from column names returned by SQLite cursor.description.

  References: #2475

- [sqlite] [bug]

  When the primary key column of a Table is replaced, such as via extend_existing, the “auto increment” column used by insert() constructs is reset. Previously it would remain referring to the previous primary key column.

  References: #2525

### mssql

- [mssql] [feature]

  Added interim create_engine flag supports_unicode_binds to PyODBC dialect, to force whether or not the dialect passes Python unicode literals to PyODBC or not.

- [mssql] [bug]

  Repaired the use_scope_identity create_engine() flag when using the pyodbc dialect. Previously this flag would be ignored if set to False. When set to False, you’ll get “SELECT @@identity” after each INSERT to get at the last inserted ID, for those tables which have “implicit_returning” set to False.

- [mssql] [bug]

  UPDATE..FROM syntax with SQL Server requires that the updated table be present in the FROM clause when an alias of that table is also present in the FROM clause. The updated table is now always present in the FROM, when FROM is present in the first place. Courtesy sayap.

  References: #2468

## 0.7.6

Released: Wed Mar 14 2012

### orm

- [orm] [feature]

  Added “no_autoflush” context manager to Session, used with with: will temporarily disable autoflush.

- [orm] [feature]

  Added cte() method to Query, invokes common table expression support from the Core (see below).

  References: #1859

- [orm] [feature]

  Added the ability to query for Table-bound column names when using query(sometable).filter_by(colname=value).

  References: #2400

- [orm] [bug]

  Fixed event registration bug which would primarily show up as events not being registered with sessionmaker() instances created after the event was associated with the Session class.

  References: #2424

- [orm] [bug]

  Fixed bug whereby a primaryjoin condition with a “literal” in it would raise an error on compile with certain kinds of deeply nested expressions which also needed to render the same bound parameter name more than once.

  References: #2425

- [orm] [bug]

  Removed the check for number of rows affected when doing a multi-delete against mapped objects. If an ON DELETE CASCADE exists between two rows, we can’t get an accurate rowcount from the DBAPI; this particular count is not supported on most DBAPIs in any case, MySQLdb is the notable case where it is.

  References: #2403

- [orm] [bug]

  Fixed bug whereby objects using attribute_mapped_collection or column_mapped_collection could not be pickled.

  References: #2409

- [orm] [bug]

  Fixed bug whereby MappedCollection would not get the appropriate collection instrumentation if it were only used in a custom subclass that used @collection.internally_instrumented.

  References: #2406

- [orm] [bug]

  Fixed bug whereby SQL adaption mechanics would fail in a very nested scenario involving joined-inheritance, joinedload(), limit(), and a derived function in the columns clause.

  References: #2419

- [orm] [bug]

  Fixed the repr() for CascadeOptions to include refresh-expire. Also reworked CascadeOptions to be a <frozenset>.

  References: #2417

- [orm] [bug]

  Improved the “declarative reflection” example to support single-table inheritance, multiple calls to prepare(), tables that are present in alternate schemas, establishing only a subset of classes as reflected.

- [orm] [bug]

  Scaled back the test applied within flush() to check for UPDATE against partially NULL PK within one table to only actually happen if there’s really an UPDATE to occur.

  References: #2390

- [orm] [bug]

  Fixed bug whereby if a method name conflicted with a column name, a TypeError would be raised when the mapper tried to inspect the __get__() method on the method object.

  References: #2352

### examples

- [examples] [bug]

  Altered _params_from_query() function in Beaker example to pull bindparams from the fully compiled statement, as a quick means to get everything including subqueries in the columns clause, etc.

### engine

- [engine] [feature]

  Added “no_parameters=True” execution option for connections. If no parameters are present, will pass the statement as cursor.execute(statement), thereby invoking the DBAPIs behavior when no parameter collection is present; for psycopg2 and mysql-python, this means not interpreting % signs in the string. This only occurs with this option, and not just if the param list is blank, as otherwise this would produce inconsistent behavior of SQL expressions that normally escape percent signs (and while compiling, can’t know ahead of time if parameters will be present in some cases).

  References: #2407

- [engine] [feature]

  Added pool_reset_on_return argument to create_engine, allows control over “connection return” behavior. Also added new arguments ‘rollback’, ‘commit’, None to pool.reset_on_return to allow more control over connection return activity.

  References: #2378

- [engine] [feature]

  Added some decent context managers to Engine, Connection:

      with engine.begin() as conn:
          <work with conn in a transaction>

  and:

      with engine.connect() as conn:
          <work with conn>

  Both close out the connection when done, commit or rollback transaction with errors on engine.begin().

- [engine] [bug]

  Added execution_options() call to MockConnection (i.e., that used with strategy=”mock”) which acts as a pass through for arguments.

### sql

- [sql] [feature]

  Added support for SQL standard common table expressions (CTE), allowing SELECT objects as the CTE source (DML not yet supported). This is invoked via the cte() method on any select() construct.

  References: #1859

- [sql] [bug]

  Fixed memory leak in core which would occur when C extensions were used with particular types of result fetches, in particular when orm query.count() were called.

  References: #2427

- [sql] [bug]

  Fixed issue whereby attribute-based column access on a row would raise AttributeError with non-C version, NoSuchColumnError with C version. Now raises AttributeError in both cases.

  References: #2398

- [sql] [bug]

  Added support for using the .key of a Column as a string identifier in a result set row. The .key is currently listed as an “alternate” name for a column, and is superseded by the name of a column which has that key value as its regular name. For the next major release of SQLAlchemy we may reverse this precedence so that .key takes precedence, but this is not decided on yet.

  References: #2392

- [sql] [bug]

  A warning is emitted when a not-present column is stated in the values() clause of an insert() or update() construct. Will move to an exception in 0.8.

  References: #2413

- [sql] [bug]

  A significant change to how labeling is applied to columns in SELECT statements allows “truncated” labels, that is label names that are generated in Python which exceed the maximum identifier length (note this is configurable via label_length on create_engine()), to be properly referenced when rendered inside of a subquery, as well as to be present in a result set row using their original in-Python names.

  References: #2396

- [sql] [bug]

  Fixed bug in new “autoload_replace” flag which would fail to preserve the primary key constraint of the reflected table.

  References: #2402

- [sql] [bug]

  Index will raise when arguments passed cannot be interpreted as columns or expressions. Will warn when Index is created with no columns at all.

  References: #2380

### mysql

- [mysql] [feature]

  Added support for MySQL index and primary key constraint types (i.e. USING) via new mysql_using parameter to Index and PrimaryKeyConstraint, courtesy Diana Clarke.

  References: #2386

- [mysql] [feature]

  Added support for the “isolation_level” parameter to all MySQL dialects. Thanks to mu_mind for the patch here.

  References: #2394

### sqlite

- [sqlite] [bug]

  Fixed bug in C extensions whereby string format would not be applied to a Numeric value returned as integer; this affected primarily SQLite which does not maintain numeric scale settings.

  References: #2432

### mssql

- [mssql] [feature]

  Added support for MSSQL INSERT, UPDATE, and DELETE table hints, using new with_hint() method on UpdateBase.

  References: #2430

### oracle

- [oracle] [feature]

  Added a new create_engine() flag coerce_to_decimal=False, disables the precision numeric handling which can add lots of overhead by converting all numeric values to Decimal.

  References: #2399

- [oracle] [bug]

  Added missing compilation support for LONG

  References: #2401

- [oracle] [bug]

  Added ‘LEVEL’ to the list of reserved words for Oracle.

  References: #2435

## 0.7.5

Released: Sat Jan 28 2012

### orm

- [orm] [feature]

  Added “class_registry” argument to declarative_base(). Allows two or more declarative bases to share the same registry of class names.

- [orm] [feature]

  query.filter() accepts multiple criteria which will join via AND, i.e. query.filter(x==y, z>q, …)

- [orm] [feature]

  Added new capability to relationship loader options to allow “default” loader strategies. Pass ‘*’ to any of joinedload(), lazyload(), subqueryload(), or noload() and that becomes the loader strategy used for all relationships, except for those explicitly stated in the Query. Thanks to up-and-coming contributor Kent Bower for an exhaustive and well written test suite !

  References: #2351

- [orm] [feature]

  New declarative reflection example added, illustrates how best to mix table reflection with declarative as well as uses some new features from.

  References: #2356

- [orm] [bug]

  Fixed issue where modified session state established after a failed flush would be committed as part of the subsequent transaction that begins automatically after manual call to rollback(). The state of the session is checked within rollback(), and if new state is present, a warning is emitted and restore_snapshot() is called a second time, discarding those changes.

  References: #2389

- [orm] [bug]

  Fixed regression from 0.7.4 whereby using an already instrumented column from a superclass as “polymorphic_on” failed to resolve the underlying Column.

  References: #2345

- [orm] [bug]

  Raise an exception if xyzload_all() is used inappropriately with two non-connected relationships.

  References: #2370

- [orm] [bug]

  Fixed bug whereby event.listen(SomeClass) forced an entirely unnecessary compile of the mapper, making events very hard to set up at module import time (nobody noticed this ??)

  References: #2367

- [orm] [bug]

  Fixed bug whereby hybrid_property didn’t work as a kw arg in any(), has().

- [orm] [bug]

  ensure pickleability of all ORM exceptions for multiprocessing compatibility.

  References: #2371

- [orm] [bug]

  implemented standard “can’t set attribute” / “can’t delete attribute” AttributeError when setattr/delattr used on a hybrid that doesn’t define fset or fdel.

  References: #2353

- [orm] [bug]

  Fixed bug where unpickled object didn’t have enough of its state set up to work correctly within the unpickle() event established by the mutable object extension, if the object needed ORM attribute access within __eq__() or similar.

  References: #2362

- [orm] [bug]

  Fixed bug where “merge” cascade could mis-interpret an unloaded attribute, if the load_on_pending flag were used with relationship(). Thanks to Kent Bower for tests.

  References: #2374

- [orm]

  Fixed regression from 0.6 whereby if “load_on_pending” relationship() flag were used where a non-“get()” lazy clause needed to be emitted on a pending object, it would fail to load.

### examples

- [examples] [feature]

  Simplified the versioning example a bit to use a declarative mixin as well as an event listener, instead of a metaclass + SessionExtension.

  References: #2313

- [examples] [bug]

  Fixed large_collection.py to close the session before dropping tables.

  References: #2346

### engine

- [engine] [bug]

  Added __reduce__ to StatementError, DBAPIError, column errors so that exceptions are pickleable, as when using multiprocessing. However, not all DBAPIs support this yet, such as psycopg2.

  References: #2371

- [engine] [bug]

  Improved error messages when a non-string or invalid string is passed to any of the date/time processors used by SQLite, including C and Python versions.

  References: #2382

- [engine] [bug]

  Fixed bug whereby a table-bound Column object named “<a>_<b>” which matched a column labeled as “<tablename>_<colname>” could match inappropriately when targeting in a result set row.

  References: #2377

- [engine] [bug]

  Fixed bug in “mock” strategy whereby correct DDL visit method wasn’t called, resulting in “CREATE/DROP SEQUENCE” statements being duplicated

  References: #2384

### sql

- [sql] [feature]

  New reflection feature “autoload_replace”; when set to False on Table, the Table can be autoloaded without existing columns being replaced. Allows more flexible chains of Table construction/reflection to be constructed, including that it helps with combining Declarative with table reflection. See the new example on the wiki.

  References: #2356

- [sql] [feature]

  Added “false()” and “true()” expression constructs to sqlalchemy.sql namespace, though not part of __all__ as of yet.

- [sql] [feature]

  Dialect-specific compilers now raise CompileError for all type/statement compilation issues, instead of InvalidRequestError or ArgumentError. The DDL for CREATE TABLE will re-raise CompileError to include table/column information for the problematic column.

  References: #2361

- [sql] [bug]

  Improved the API for add_column() such that if the same column is added to its own table, an error is not raised and the constraints don’t get doubled up. Also helps with some reflection/declarative patterns.

  References: #2356

- [sql] [bug]

  Fixed issue where the “required” exception would not be raised for bindparam() with required=True, if the statement were given no parameters at all.

  References: #2381

### mysql

- [mysql] [bug]

  fixed regexp that filters out warnings for non-reflected “PARTITION” directives, thanks to George Reilly

  References: #2376

### sqlite

- [sqlite] [bug]

  the “name” of an FK constraint in SQLite is reflected as “None”, not “0” or other integer value. SQLite does not appear to support constraint naming in any case.

  References: #2364

- [sqlite] [bug]

  sql.false() and sql.true() compile to 0 and 1, respectively in sqlite

  References: #2368

- [sqlite] [bug]

  removed an erroneous “raise” in the SQLite dialect when getting table names and view names, where logic is in place to fall back to an older version of SQLite that doesn’t have the “sqlite_temp_master” table.

### mssql

- [mssql] [bug]

  Adjusted the regexp used in the mssql.TIME type to ensure only six digits are received for the “microseconds” portion of the value, which is expected by Python’s datetime.time(). Note that support for sending microseconds doesn’t seem to be possible yet with pyodbc at least.

  References: #2340

- [mssql] [bug]

  Dropped the “30 char” limit on pymssql, based on reports that it’s doing things better these days. pymssql hasn’t been well tested and as the DBAPI is in flux it’s still not clear what the status is on this driver and how SQLAlchemy’s implementation should adapt.

  References: #2347

### oracle

- [oracle] [bug]

  Added ORA-03135 to the never ending list of oracle “connection lost” errors

  References: #2388

### misc

- [bug] [core]

  Changed LRUCache, used by the mapper to cache INSERT/UPDATE/DELETE statements, to use an incrementing counter instead of a timestamp to track entries, for greater reliability versus using time.time(), which can cause test failures on some platforms.

  References: #2379

- [bug] [core]

  Added a boolean check for the “finalize” function within the pool connection proxy’s weakref callback before calling it, so that a warning isn’t emitted that this function is None when the application is exiting and gc has removed the function from the module before the weakref callback was invoked.

  References: #2383

- [bug] [py3k]

  Fixed inappropriate usage of util.py3k flag and renamed it to util.py3k_warning, since this flag is intended to detect the -3 flag series of import restrictions only.

  References: #2348

## 0.7.4

Released: Fri Dec 09 2011

### orm

- [orm] [feature]

  polymorphic_on now accepts many new kinds of values:

  > - standalone expressions that aren’t otherwise mapped

  > - column_property() objects

  > - string names of any column_property() or attribute name of a mapped Column

  The docs include an example using the case() construct, which is likely to be a common constructed used here. and part of

  Standalone expressions in polymorphic_on propagate to single-table inheritance subclasses so that they are used in the WHERE /JOIN clause to limit rows to that subclass as is the usual behavior.

  References: #2238, #2345

- [orm] [feature]

  IdentitySet supports the - operator as the same as difference(), handy when dealing with Session.dirty etc.

  References: #2301

- [orm] [feature]

  Added new value for Column autoincrement called “ignore_fk”, can be used to force autoincrement on a column that’s still part of a ForeignKeyConstraint. New example in the relationship docs illustrates its use.

- [orm] [bug]

  Fixed backref behavior when “popping” the value off of a many-to-one in response to a removal from a stale one-to-many - the operation is skipped, since the many-to-one has since been updated.

  References: #2315

- [orm] [bug]

  After some years of not doing this, added more granularity to the “is X a parent of Y” functionality, which is used when determining if the FK on “Y” needs to be “nulled out” as well as if “Y” should be deleted with delete-orphan cascade. The test now takes into account the Python identity of the parent as well its identity key, to see if the last known parent of Y is definitely X. If a decision can’t be made, a StaleDataError is raised. The conditions where this error is raised are fairly rare, requiring that the previous parent was garbage collected, and previously could very well inappropriately update/delete a record that’s since moved onto a new parent, though there may be some cases where “silent success” occurred previously that will now raise in the face of ambiguity. Expiring “Y” resets the “parent” tracker, meaning X.remove(Y) could then end up deleting Y even if X is stale, but this is the same behavior as before; it’s advised to expire X also in that case.

  References: #2264

- [orm] [bug]

  fixed inappropriate evaluation of user-mapped object in a boolean context within query.get(). Also in 0.6.9.

  References: #2310

- [orm] [bug]

  Added missing comma to PASSIVE_RETURN_NEVER_SET symbol

  References: #2304

- [orm] [bug]

  Cls.column.collate(“some collation”) now works. Also in 0.6.9

  References: #1776

- [orm] [bug]

  the value of a composite attribute is now expired after an insert or update operation, instead of regenerated in place. This ensures that a column value which is expired within a flush will be loaded first, before the composite is regenerated using that value.

  References: #2309

- [orm] [bug]

  The fix in also emits the “refresh” event when the composite value is loaded on access, even if all column values were already present, as is appropriate. This fixes the “mutable” extension which relies upon the “load” event to ensure the _parents dictionary is up to date, fixes. Thanks to Scott Torborg for the test case here.

  References: #2308, #2309

- [orm] [bug]

  Fixed bug whereby a subclass of a subclass using concrete inheritance in conjunction with the new ConcreteBase or AbstractConcreteBase would fail to apply the subclasses deeper than one level to the “polymorphic loader” of each base

  References: #2312

- [orm] [bug]

  Fixed bug whereby a subclass of a subclass using the new AbstractConcreteBase would fail to acquire the correct “base_mapper” attribute when the “base” mapper was generated, thereby causing failures later on.

  References: #2312

- [orm] [bug]

  Fixed bug whereby column_property() created against ORM-level column could be treated as a distinct entity when producing certain kinds of joined-inh joins.

  References: #2316

- [orm] [bug]

  Fixed the error formatting raised when a tuple is inadvertently passed to session.query(). Also in 0.6.9.

  References: #2297

- [orm] [bug]

  Calls to query.join() to a single-table inheritance subclass are now tracked, and are used to eliminate the additional WHERE.. IN criterion normally tacked on with single table inheritance, since the join should accommodate it. This allows OUTER JOIN to a single table subclass to produce the correct results, and overall will produce fewer WHERE criterion when dealing with single table inheritance joins.

  References: #2328

- [orm] [bug]

  __table_args__ can now be passed as an empty tuple as well as an empty dict.. Thanks to Fayaz Yusuf Khan for the patch.

  References: #2339

- [orm] [bug]

  Updated warning message when setting delete-orphan without delete to no longer refer to 0.6, as we never got around to upgrading this to an exception. Ideally this might be better as an exception but it’s not critical either way.

  References: #2325

- [orm] [bug]

  Fixed bug in get_history() when referring to a composite attribute that has no value; added coverage for get_history() regarding composites which is otherwise just a userland function.

### examples

- [examples] [bug]

  Fixed bug in history_meta.py example where the “unique” flag was not removed from a single-table-inheritance subclass which generates columns to put up onto the base.

### engine

- [engine] [bug]

  Fixed bug whereby transaction.rollback() would throw an error on an invalidated connection if the transaction were a two-phase or savepoint transaction. For plain transactions, rollback() is a no-op if the connection is invalidated, so while it wasn’t 100% clear if it should be a no-op, at least now the interface is consistent.

  References: #2317

### sql

- [sql] [feature]

  The update() construct can now accommodate multiple tables in the WHERE clause, which will render an “UPDATE..FROM” construct, recognized by PostgreSQL and MSSQL. When compiled on MySQL, will instead generate “UPDATE t1, t2, ..”. MySQL additionally can render against multiple tables in the SET clause, if Column objects are used as keys in the “values” parameter or generative method.

  References: #1944, #2166

- [sql] [feature]

  Added accessor to types called “python_type”, returns the rudimentary Python type object for a particular TypeEngine instance, if known, else raises NotImplementedError.

  References: #77

- [sql] [bug]

  related to, made some adjustments to the change from regarding the “from” list on a select(). The _froms collection is no longer memoized, as this simplifies various use cases and removes the need for a “warning” if a column is attached to a table after it was already used in an expression - the select() construct will now always produce the correct expression. There’s probably no real-world performance hit here; select() objects are almost always made ad-hoc, and systems that wish to optimize the re-use of a select() would be using the “compiled_cache” feature. A hit which would occur when calling select.bind has been reduced, but the vast majority of users shouldn’t be using “bound metadata” anyway :).

  References: #2261, #2316

- [sql] [bug]

  further tweak to the fix from, so that generative methods work a bit better off of cloned (this is almost a non-use case though). In particular this allows with_only_columns() to behave more consistently. Added additional documentation to with_only_columns() to clarify expected behavior, which changed as a result of.

  References: #2261, #2319

### schema

- [schema] [feature]

  Added new support for remote “schemas”:

- [schema] [feature]

  The “extend_existing” flag on Table now allows for the reflection process to take effect for a Table object that’s already been defined; when autoload=True and extend_existing=True are both set, the full set of columns will be reflected from the Table which will then overwrite those columns already present, rather than no activity occurring. Columns that are present directly in the autoload run will be used as always, however.

  References: #1410

- [schema] [bug]

  Fixed bug whereby TypeDecorator would return a stale value for _type_affinity, when using a TypeDecorator that “switches” types, like the CHAR/UUID type.

- [schema] [bug]

  Fixed bug whereby “order_by=’foreign_key’” option to Inspector.get_table_names wasn’t implementing the sort properly, replaced with the existing sort algorithm

- [schema] [bug]

  the “name” of a column-level CHECK constraint, if present, is now rendered in the CREATE TABLE statement using “CONSTRAINT <name> CHECK <expression>”.

  References: #2305

- [schema]

  MetaData() accepts “schema” and “quote_schema” arguments, which will be applied to the same-named arguments of a Table or Sequence which leaves these at their default of `None`.

- [schema]

  Sequence accepts “quote_schema” argument

- [schema]

  tometadata() for Table will use the “schema” of the incoming MetaData for the new Table if the schema argument is explicitly “None”

- [schema]

  Added CreateSchema and DropSchema DDL constructs - these accept just the string name of a schema and a “quote” flag.

- [schema]

  When using default “schema” with MetaData, ForeignKey will also assume the “default” schema when locating remote table. This allows the “schema” argument on MetaData to be applied to any set of Table objects that otherwise don’t have a “schema”.

- [schema]

  a “has_schema” method has been implemented on dialect, but only works on PostgreSQL so far. Courtesy Manlio Perillo.

  References: #1679

### postgresql

- [postgresql] [feature]

  Added create_type constructor argument to pg.ENUM. When False, no CREATE/DROP or checking for the type will be performed as part of a table create/drop event; only the create()/drop)() methods called directly will do this. Helps with Alembic “offline” scripts.

- [postgresql] [bug]

  PostgreSQL dialect memoizes that an ENUM of a particular name was processed during a create/drop sequence. This allows a create/drop sequence to work without any calls to “checkfirst”, and also means with “checkfirst” turned on it only needs to check for the ENUM once.

  References: #2311

### mysql

- [mysql] [bug]

  Unicode adjustments allow latest pymysql (post 0.4) to pass 100% on Python 2.

### mssql

- [mssql] [feature]

  lifted the restriction on SAVEPOINT for SQL Server. All tests pass using it, it’s not known if there are deeper issues however.

  References: #822

- [mssql] [bug]

  repaired the with_hint() feature which wasn’t implemented correctly on MSSQL - usually used for the “WITH (NOLOCK)” hint (which you shouldn’t be using anyway ! use snapshot isolation instead :) )

  References: #2336

- [mssql] [bug]

  use new pyodbc version detection for _need_decimal_fix option.

  References: #2318

- [mssql] [bug]

  don’t cast “table name” as NVARCHAR on SQL Server 2000. Still mostly in the dark what incantations are needed to make PyODBC work fully with FreeTDS 0.91 here, however.

  References: #2343

- [mssql] [bug]

  Decode incoming values when retrieving list of index names and the names of columns within those indexes.

  References: #2269

### misc

- [feature] [ext]

  Added an example to the hybrid docs of a “transformer” - a hybrid that returns a query-transforming callable in combination with a custom comparator. Uses a new method on Query called with_transformation(). The use case here is fairly experimental, but only adds one line of code to Query.

- [bug] [pyodbc]

  pyodbc-based dialects now parse the pyodbc accurately as far as observed pyodbc strings, including such gems as “py3-3.0.1-beta4”

  References: #2318

- [bug] [ext]

  the @compiles decorator raises an informative error message when no “default” compilation handler is present, rather than KeyError.

## 0.7.3

Released: Sun Oct 16 2011

### general

- [general]

  Adjusted the “importlater” mechanism, which is used internally to resolve import cycles, such that the usage of __import__ is completed when the import of sqlalchemy or sqlalchemy.orm is done, thereby avoiding any usage of __import__ after the application starts new threads, fixes. Also in 0.6.9.

  References: #2279

### orm

- [orm]

  Improved query.join() such that the “left” side can more flexibly be a non-ORM selectable, such as a subquery. A selectable placed in select_from() will now be used as the left side, favored over implicit usage of a mapped entity. If the join still fails based on lack of foreign keys, the error message includes this detail. Thanks to brianrhude on IRC for the test case.

  References: #2298

- [orm]

  Added after_soft_rollback() Session event. This event fires unconditionally whenever rollback() is called, regardless of if an actual DBAPI level rollback occurred. This event is specifically designed to allow operations with the Session to proceed after a rollback when the Session.is_active is True.

  References: #2241

- [orm]

  added “adapt_on_names” boolean flag to orm.aliased() construct. Allows an aliased() construct to link the ORM entity to a selectable that contains aggregates or other derived forms of a particular attribute, provided the name is the same as that of the entity mapped column.

- [orm]

  Added new flag expire_on_flush=False to column_property(), marks those properties that would otherwise be considered to be “readonly”, i.e. derived from SQL expressions, to retain their value after a flush has occurred, including if the parent object itself was involved in an update.

- [orm]

  Enhanced the instrumentation in the ORM to support Py3K’s new argument style of “required kw arguments”, i.e. fn(a, b, *, c, d), fn(a, b, *args, c, d). Argument signatures of mapped object’s __init__ method will be preserved, including required kw rules.

  References: #2237

- [orm]

  Fixed bug in unit of work whereby detection of “cycles” among classes in highly interlinked patterns would not produce a deterministic result; thereby sometimes missing some nodes that should be considered cycles and causing further issues down the road. Note this bug is in 0.6 also; not backported at the moment.

  References: #2282

- [orm]

  Fixed a variety of synonym()-related regressions from 0.6:

  > - making a synonym against a synonym now works.

  > - synonyms made against a relationship() can be passed to query.join(), options sent to query.options(), passed by name to query.with_parent().

- [orm]

  Fixed bug whereby mapper.order_by attribute would be ignored in the “inner” query within a subquery eager load. . Also in 0.6.9.

  References: #2287

- [orm]

  Identity map .discard() uses dict.pop(,None) internally instead of “del” to avoid KeyError/warning during a non-determinate gc teardown

  References: #2267

- [orm]

  Fixed regression in new composite rewrite where deferred=True option failed due to missing import

  References: #2253

- [orm]

  Reinstated “comparator_factory” argument to composite(), removed when 0.7 was released.

  References: #2248

- [orm]

  Fixed bug in query.join() which would occur in a complex multiple-overlapping path scenario, where the same table could be joined to twice. Thanks much to Dave Vitek for the excellent fix here.

  References: #2247

- [orm]

  Query will convert an OFFSET of zero when slicing into None, so that needless OFFSET clauses are not invoked.

- [orm]

  Repaired edge case where mapper would fail to fully update internal state when a relationship on a new mapper would establish a backref on the first mapper.

- [orm]

  Fixed bug whereby if __eq__() was redefined, a relationship many-to-one lazyload would hit the __eq__() and fail. Does not apply to 0.6.9.

  References: #2260

- [orm]

  Calling class_mapper() and passing in an object that is not a “type” (i.e. a class that could potentially be mapped) now raises an informative ArgumentError, rather than UnmappedClassError.

  References: #2196

- [orm]

  New event hook, MapperEvents.after_configured(). Called after a configure() step has completed and mappers were in fact affected. Theoretically this event is called once per application, unless new mappings are constructed after existing ones have been used already.

- [orm]

  When an open Session is garbage collected, the objects within it which remain are considered detached again when they are add()-ed to a new Session. This is accomplished by an extra check that the previous “session_key” doesn’t actually exist among the pool of Sessions.

  References: #2281

- [orm]

  New declarative features:

  > - __declare_last__() method, establishes an event listener for the class method that will be called when mappers are completed with the final “configure” step.

  > - __abstract__ flag. The class will not be mapped at all when this flag is present on the class.

  > - New helper classes ConcreteBase, AbstractConcreteBase. Allow concrete mappings using declarative which automatically set up the “polymorphic_union” when the “configure” mapper step is invoked.

  > - The mapper itself has semi-private methods that allow the “with_polymorphic” selectable to be assigned to the mapper after it has already been configured.

  References: #2239

- [orm]

  Declarative will warn when a subclass’ base uses @declared_attr for a regular column - this attribute does not propagate to subclasses.

  References: #2283

- [orm]

  The integer “id” used to link a mapped instance with its owning Session is now generated by a sequence generation function rather than id(Session), to eliminate the possibility of recycled id() values causing an incorrect result, no need to check that object actually in the session.

  References: #2280

- [orm]

  Behavioral improvement: empty conjunctions such as and_() and or_() will be flattened in the context of an enclosing conjunction, i.e. and_(x, or_()) will produce ‘X’ and not ‘X AND ()’..

  References: #2257

- [orm]

  Fixed bug regarding calculation of “from” list for a select() element. The “from” calc is now delayed, so that if the construct uses a Column object that is not yet attached to a Table, but is later associated with a Table, it generates SQL using the table as a FROM. This change impacted fairly deeply the mechanics of how the FROM list as well as the “correlates” collection is calculated, as some “clause adaption” schemes (these are used very heavily in the ORM) were relying upon the fact that the “froms” collection would typically be cached before the adaption completed. The rework allows it such that the “froms” collection can be cleared and re-generated at any time.

  References: #2261

- [orm]

  Fixed bug whereby with_only_columns() method of Select would fail if a selectable were passed.. Also in 0.6.9.

  References: #2270

### examples

- [examples]

  Adjusted dictlike-polymorphic.py example to apply the CAST such that it works on PG, other databases. Also in 0.6.9.

  References: #2266

### engine

- [engine]

  The recreate() method in all pool classes uses self.__class__ to get at the type of pool to produce, in the case of subclassing. Note there’s no usual need to subclass pools.

  References: #2254

- [engine]

  Improvement to multi-param statement logging, long lists of bound parameter sets will be compressed with an informative indicator of the compression taking place. Exception messages use the same improved formatting.

  References: #2243

- [engine]

  Added optional “sa_pool_key” argument to pool.manage(dbapi).connect() so that serialization of args is not necessary.

- [engine]

  The entry point resolution supported by create_engine() now supports resolution of individual DBAPI drivers on top of a built-in or entry point-resolved dialect, using the standard ‘+’ notation - it’s converted to a ‘.’ before being resolved as an entry point.

  References: #2286

- [engine]

  Added an exception catch + warning for the “return unicode detection” step within connect, allows databases that crash on NVARCHAR to continue initializing, assuming no NVARCHAR type implemented.

  References: #2299

### schema

- [schema]

  Modified Column.copy() to use _constructor(), which defaults to self.__class__, in order to create the new object. This allows easier support of subclassing Column.

  References: #2284

- [schema]

  Added a slightly nicer __repr__() to SchemaItem classes. Note the repr here can’t fully support the “repr is the constructor” idea since schema items can be very deeply nested/cyclical, have late initialization of some things, etc.

  References: #2223

### postgresql

- [postgresql]

  Added “postgresql_using” argument to Index(), produces USING clause to specify index implementation for PG. . Thanks to Ryan P. Kelly for the patch.

  References: #2290

- [postgresql]

  Added client_encoding parameter to create_engine() when the postgresql+psycopg2 dialect is used; calls the psycopg2 set_client_encoding() method with the value upon connect.

  References: #1839

- [postgresql]

  Fixed bug related to whereby the same modified index behavior in PG 9 affected primary key reflection on a renamed column.. Also in 0.6.9.

  References: #2141, #2291

- [postgresql]

  Reflection functions for Table, Sequence no longer case insensitive. Names can be differ only in case and will be correctly distinguished.

  References: #2256

- [postgresql]

  Use an atomic counter as the “random number” source for server side cursor names; conflicts have been reported in rare cases.

- [postgresql]

  Narrowed the assumption made when reflecting a foreign-key referenced table with schema in the current search path; an explicit schema will be applied to the referenced table only if it actually matches that of the referencing table, which also has an explicit schema. Previously it was assumed that “current” schema was synonymous with the full search_path.

  References: #2249

### mysql

- [mysql]

  a CREATE TABLE will put the COLLATE option after CHARSET, which appears to be part of MySQL’s arbitrary rules regarding if it will actually work or not. Also in 0.6.9.

  References: #2225

- [mysql]

  Added mysql_length parameter to Index construct, specifies “length” for indexes.

  References: #2293

### sqlite

- [sqlite]

  Ensured that the same ValueError is raised for illegal date/time/datetime string parsed from the database regardless of whether C extensions are in use or not.

### mssql

- [mssql]

  Changes to attempt support of FreeTDS 0.91 with Pyodbc. This includes that string binds are sent as Python unicode objects when FreeTDS 0.91 is detected, and a CAST(? AS NVARCHAR) is used when we detect for a table. However, I’d continue to characterize Pyodbc + FreeTDS 0.91 behavior as pretty crappy, there are still many queries such as used in reflection which cause a core dump on Linux, and it is not really usable at all on OSX, MemoryErrors abound and just plain broken unicode support.

  References: #2273

- [mssql]

  The behavior of =/!= when comparing a scalar select to a value will no longer produce IN/NOT IN as of 0.8; this behavior is a little too heavy handed (use `in_()` if you want to emit IN) and now emits a deprecation warning. To get the 0.8 behavior immediately and remove the warning, a compiler recipe is given at https://www.sqlalchemy.org/docs/07/dialects/mssql.html#scalar-select-comparisons to override the behavior of visit_binary().

  References: #2277

- [mssql]

  ”0” is accepted as an argument for limit() which will produce “TOP 0”.

  References: #2222

### oracle

- [oracle]

  Fixed ReturningResultProxy for zxjdbc dialect.. Regression from 0.6.

  References: #2272

- [oracle]

  The String type now generates VARCHAR2 on Oracle which is recommended as the default VARCHAR. Added an explicit VARCHAR2 and NVARCHAR2 to the Oracle dialect as well. Using NVARCHAR still generates “NVARCHAR2” - there is no “NVARCHAR” on Oracle - this remains a slight breakage of the “uppercase types always give exactly that” policy. VARCHAR still generates “VARCHAR”, keeping with the policy. If Oracle were to ever define “VARCHAR” as something different as they claim (IMHO this will never happen), the type would be available.

  References: #2252

### misc

- [types]

  Extra keyword arguments to the base Float type beyond “precision” and “asdecimal” are ignored; added a deprecation warning here and additional docs, related to

  References: #2258

- [ext]

  SQLSoup will not be included in version 0.8 of SQLAlchemy; while useful, we would like to keep SQLAlchemy itself focused on one ORM usage paradigm. SQLSoup will hopefully soon be superseded by a third party project.

  References: #2262

- [ext]

  Added local_attr, remote_attr, attr accessors to AssociationProxy, providing quick access to the proxied attributes at the class level.

  References: #2236

- [ext]

  Changed the update() method on association proxy dictionary to use a duck typing approach, i.e. checks for “keys”, to discern between update({}) and update((a, b)). Previously, passing a dictionary that had tuples as keys would be misinterpreted as a sequence.

  References: #2275

## 0.7.2

Released: Sun Jul 31 2011

### orm

- [orm]

  Feature enhancement: joined and subquery loading will now traverse already-present related objects and collections in search of unpopulated attributes throughout the scope of the eager load being defined, so that the eager loading that is specified via mappings or query options unconditionally takes place for the full depth, populating whatever is not already populated. Previously, this traversal would stop if a related object or collection were already present leading to inconsistent behavior (though would save on loads/cycles for an already-loaded graph). For a subqueryload, this means that the additional SELECT statements emitted by subqueryload will invoke unconditionally, no matter how much of the existing graph is already present (hence the controversy). The previous behavior of “stopping” is still in effect when a query is the result of an attribute-initiated lazyload, as otherwise an “N+1” style of collection iteration can become needlessly expensive when the same related object is encountered repeatedly. There’s also an as-yet-not-public generative Query method _with_invoke_all_eagers() which selects old/new behavior

  References: #2213

- [orm]

  A rework of “replacement traversal” within the ORM as it alters selectables to be against aliases of things (i.e. clause adaption) includes a fix for multiply-nested any()/has() constructs against a joined table structure.

  References: #2195

- [orm]

  Fixed bug where query.join() + aliased=True from a joined-inh structure to itself on relationship() with join condition on the child table would convert the lead entity into the joined one inappropriately. Also in 0.6.9.

  References: #2234

- [orm]

  Fixed regression from 0.6 where Session.add() against an object which contained None in a collection would raise an internal exception. Reverted this to 0.6’s behavior which is to accept the None but obviously nothing is persisted. Ideally, collections with None present or on append() should at least emit a warning, which is being considered for 0.8.

  References: #2205

- [orm]

  Load of a deferred() attribute on an object where row can’t be located raises ObjectDeletedError instead of failing later on; improved the message in ObjectDeletedError to include other conditions besides a simple “delete”.

  References: #2191

- [orm]

  Fixed regression from 0.6 where a get history operation on some relationship() based attributes would fail when a lazyload would emit; this could trigger within a flush() under certain conditions. Thanks to the user who submitted the great test for this.

  References: #2224

- [orm]

  Fixed bug apparent only in Python 3 whereby sorting of persistent + pending objects during flush would produce an illegal comparison, if the persistent object primary key is not a single integer. Also in 0.6.9

  References: #2228

- [orm]

  Fixed bug whereby the source clause used by query.join() would be inconsistent if against a column expression that combined multiple entities together. Also in 0.6.9

  References: #2197

- [orm]

  Fixed bug whereby if a mapped class redefined __hash__() or __eq__() to something non-standard, which is a supported use case as SQLA should never consult these, the methods would be consulted if the class was part of a “composite” (i.e. non-single-entity) result set. Also in 0.6.9.

  References: #2215

- [orm]

  Added public attribute “.validators” to Mapper, an immutable dictionary view of all attributes that have been decorated with the @validates decorator. courtesy Stefano Fontanelli

  References: #2240

- [orm]

  Fixed subtle bug that caused SQL to blow up if: column_property() against subquery + joinedload + LIMIT + order by the column property() occurred. . Also in 0.6.9

  References: #2188

- [orm]

  The join condition produced by with_parent as well as when using a “dynamic” relationship against a parent will generate unique bindparams, rather than incorrectly repeating the same bindparam. . Also in 0.6.9.

  References: #2207

- [orm]

  Added the same “columns-only” check to mapper.polymorphic_on as used when receiving user arguments to relationship.order_by, foreign_keys, remote_side, etc.

- [orm]

  Fixed bug whereby comparison of column expression to a Query() would not call as_scalar() on the underlying SELECT statement to produce a scalar subquery, in the way that occurs if you called it on Query().subquery().

  References: #2190

- [orm]

  Fixed declarative bug where a class inheriting from a superclass of the same name would fail due to an unnecessary lookup of the name in the _decl_class_registry.

  References: #2194

- [orm]

  Repaired the “no statement condition” assertion in Query which would attempt to raise if a generative method were called after from_statement() were called.. Also in 0.6.9.

  References: #2199

### examples

- [examples]

  Repaired the examples/versioning test runner to not rely upon SQLAlchemy test libs, nosetests must be run from within examples/versioning to get around setup.cfg breaking it.

- [examples]

  Tweak to examples/versioning to pick the correct foreign key in a multi-level inheritance situation.

- [examples]

  Fixed the attribute shard example to check for bind param callable correctly in 0.7 style.

### engine

- [engine]

  Context manager provided by Connection.begin() will issue rollback() if the commit() fails, not just if an exception occurs.

- [engine]

  Use urllib.parse_qsl() in Python 2.6 and above, no deprecation warning about cgi.parse_qsl()

  References: #1682

- [engine]

  Added mixin class sqlalchemy.ext.DontWrapMixin. User-defined exceptions of this type are never wrapped in StatementException when they occur in the context of a statement execution.

- [engine]

  StatementException wrapping will display the original exception class in the message.

- [engine]

  Failures on connect which raise dbapi.Error will forward the error to dialect.is_disconnect() and set the “connection_invalidated” flag if the dialect knows this to be a potentially “retryable” condition. Only Oracle ORA-01033 implemented for now.

  References: #2201

### sql

- [sql]

  Fixed two subtle bugs involving column correspondence in a selectable, one with the same labeled subquery repeated, the other when the label has been “grouped” and loses itself. Affects.

  References: #2188

### schema

- [schema]

  New feature: with_variant() method on all types. Produces an instance of Variant(), a special TypeDecorator which will select the usage of a different type based on the dialect in use.

  References: #2187

- [schema]

  Added an informative error message when ForeignKeyConstraint refers to a column name in the parent that is not found. Also in 0.6.9.

- [schema]

  Fixed bug whereby adaptation of old append_ddl_listener() function was passing unexpected **kw through to the Table event. Table gets no kws, the MetaData event in 0.6 would get “tables=somecollection”, this behavior is preserved.

  References: #2206

- [schema]

  Fixed bug where “autoincrement” detection on Table would fail if the type had no “affinity” value, in particular this would occur when using the UUID example on the site that uses TypeEngine as the “impl”.

- [schema]

  Added an improved repr() to TypeEngine objects that will only display constructor args which are positional or kwargs that deviate from the default.

  References: #2209

### postgresql

- [postgresql]

  Added new “postgresql_ops” argument to Index, allows specification of PostgreSQL operator classes for indexed columns. Courtesy Filip Zyzniewski.

  References: #2198

### mysql

- [mysql]

  Fixed OurSQL dialect to use ansi-neutral quote symbol “’” for XA commands instead of ‘”’. . Also in 0.6.9.

  References: #2186

### sqlite

- [sqlite]

  SQLite dialect no longer strips quotes off of reflected default value, allowing a round trip CREATE TABLE to work. This is consistent with other dialects that also maintain the exact form of the default.

  References: #2189

### mssql

- [mssql]

  Adjusted the pyodbc dialect such that bound values are passed as bytes and not unicode if the “Easysoft” unix drivers are detected. This is the same behavior as occurs with FreeTDS. Easysoft appears to segfault if Python unicodes are passed under certain circumstances.

### oracle

- [oracle]

  Added ORA-00028 to disconnect codes, use cx_oracle _Error.code to get at the code,. Also in 0.6.9.

  References: #2200

- [oracle]

  Added ORA-01033 to disconnect codes, which can be caught during a connection event.

  References: #2201

- [oracle]

  repaired the oracle.RAW type which did not generate the correct DDL. Also in 0.6.9.

  References: #2220

- [oracle]

  added CURRENT to reserved word list. Also in 0.6.9.

  References: #2212

- [oracle]

  Fixed bug in the mutable extension whereby if the same type were used twice in one mapping, the attributes beyond the first would not get instrumented.

- [oracle]

  Fixed bug in the mutable extension whereby if None or a non-corresponding type were set, an error would be raised. None is now accepted which assigns None to all attributes, illegal values raise ValueError.

## 0.7.1

Released: Sun Jun 05 2011

### general

- [general]

  Added a workaround for Python bug 7511 where failure of C extension build does not raise an appropriate exception on Windows 64 bit + VC express

  References: #2184

### orm

- [orm]

  ”delete-orphan” cascade is now allowed on self-referential relationships - this since SQLA 0.7 no longer enforces “parent with no child” at the ORM level; this check is left up to foreign key nullability. Related to

  References: #1912

- [orm]

  Repaired new “mutable” extension to propagate events to subclasses correctly; don’t create multiple event listeners for subclasses either.

  References: #2180

- [orm]

  Modify the text of the message which occurs when the “identity” key isn’t detected on flush, to include the common cause that the Column isn’t set up to detect auto-increment correctly;. Also in 0.6.8.

  References: #2170

- [orm]

  Fixed bug where transaction-level “deleted” collection wouldn’t be cleared of expunged states, raising an error if they later became transient. Also in 0.6.8.

  References: #2182

### engine

- [engine]

  Deprecate schema/SQL-oriented methods on Connection/Engine that were never well known and are redundant: reflecttable(), create(), drop(), text(), engine.func

- [engine]

  Adjusted the __contains__() method of a RowProxy result row such that no exception throw is generated internally; NoSuchColumnError() also will generate its message regardless of whether or not the column construct can be coerced to a string.. Also in 0.6.8.

  References: #2178

### sql

- [sql]

  Fixed bug whereby metadata.reflect(bind) would close a Connection passed as a bind argument. Regression from 0.6.

- [sql]

  Streamlined the process by which a Select determines what’s in its ‘.c’ collection. Behaves identically, except that a raw ClauseList() passed to select([]) (which is not a documented case anyway) will now be expanded into its individual column elements instead of being ignored.

### postgresql

- [postgresql]

  Some unit test fixes regarding numeric arrays, MATCH operator. A potential floating-point inaccuracy issue was fixed, and certain tests of the MATCH operator only execute within an EN-oriented locale for now. . Also in 0.6.8.

  References: #2175

### mysql

- [mysql]

  Unit tests pass 100% on MySQL installed on windows.

- [mysql]

  Removed the “adjust casing” step that would fail when reflecting a table on MySQL on windows with a mixed case name. After some experimenting with a windows MySQL server, it’s been determined that this step wasn’t really helping the situation much; MySQL does not return FK names with proper casing on non-windows platforms either, and removing the step at least allows the reflection to act more like it does on other OSes. A warning here has been considered but its difficult to determine under what conditions such a warning can be raised, so punted on that for now - added some docs instead.

  References: #2181

- [mysql]

  supports_sane_rowcount will be set to False if using MySQLdb and the DBAPI doesn’t provide the constants.CLIENT module.

### sqlite

- [sqlite]

  Accept None from cursor.fetchone() when “PRAGMA read_uncommitted” is called to determine current isolation mode at connect time and default to SERIALIZABLE; this to support SQLite versions pre-3.3.0 that did not have this feature.

  References: #2173

## 0.7.0

Released: Fri May 20 2011

### orm

- [orm]

  Fixed regression introduced in 0.7b4 (!) whereby query.options(someoption(“nonexistent name”)) would fail to raise an error. Also added additional error catching for cases where the option would try to build off a column-based element, further fixed up some of the error messages tailored in

  References: #2069

- [orm]

  query.count() emits “count(*)” instead of “count(1)”.

  References: #2162

- [orm]

  Fine tuning of Query clause adaptation when from_self(), union(), or other “select from myself” operation, such that plain SQL expression elements added to filter(), order_by() etc. which are present in the nested “from myself” query will be adapted in the same way an ORM expression element will, since these elements are otherwise not easily accessible.

  References: #2155

- [orm]

  Fixed bug where determination of “self referential” relationship would fail with no workaround for joined-inh subclass related to itself, or joined-inh subclass related to a subclass of that with no cols in the sub-sub class in the join condition. Also in 0.6.8.

  References: #2149

- [orm]

  mapper() will ignore non-configured foreign keys to unrelated tables when determining inherit condition between parent and child class, but will raise as usual for unresolved columns and table names regarding the inherited table. This is an enhanced generalization of behavior that was already applied to declarative previously. 0.6.8 has a more conservative version of this which doesn’t fundamentally alter how join conditions are determined.

  References: #2153

- [orm]

  It is an error to call query.get() when the given entity is not a single, full class entity or mapper (i.e. a column). This is a deprecation warning in 0.6.8.

  References: #2144

- [orm]

  Fixed a potential KeyError which under some circumstances could occur with the identity map, part of

  References: #2148

- [orm]

  added Query.with_session() method, switches Query to use a different session.

- [orm]

  horizontal shard query should use execution options per connection as per

  References: #2131

- [orm]

  a non_primary mapper will inherit the _identity_class of the primary mapper. This so that a non_primary established against a class that’s normally in an inheritance mapping will produce results that are identity-map compatible with that of the primary mapper (also in 0.6.8)

  References: #2151

- [orm]

  Fixed the error message emitted for “can’t execute syncrule for destination column ‘q’; mapper ‘X’ does not map this column” to reference the correct mapper. . Also in 0.6.8.

  References: #2163

- [orm]

  polymorphic_union() gets a “cast_nulls” option, disables the usage of CAST when it renders the labeled NULL columns.

  References: #1502

- [orm]

  polymorphic_union() renders the columns in their original table order, as according to the first table/selectable in the list of polymorphic unions in which they appear. (which is itself an unordered mapping unless you pass an OrderedDict).

- [orm]

  Fixed bug whereby mapper mapped to an anonymous alias would fail if logging were used, due to unescaped % sign in the alias name. Also in 0.6.8.

  References: #2171

### examples

- [examples]

  removed the ancient “polymorphic association” examples and replaced with an updated set of examples that use declarative mixins, “generic_associations”. Each presents an alternative table layout.

### sql

- [sql]

  Fixed bug whereby nesting a label of a select() with another label in it would produce incorrect exported columns. Among other things this would break an ORM column_property() mapping against another column_property(). . Also in 0.6.8

  References: #2167

- [sql]

  Changed the handling in determination of join conditions such that foreign key errors are only considered between the two given tables. That is, t1.join(t2) will report FK errors that involve ‘t1’ or ‘t2’, but anything involving ‘t3’ will be skipped. This affects join(), as well as ORM relationship and inherit condition logic.

- [sql]

  Some improvements to error handling inside of the execute procedure to ensure auto-close connections are really closed when very unusual DBAPI errors occur.

- [sql]

  metadata.reflect() and reflection.Inspector() had some reliance on GC to close connections which were internally procured, fixed this.

- [sql]

  Added explicit check for when Column .name is assigned as blank string

  References: #2140

- [sql]

  Fixed bug whereby if FetchedValue was passed to column server_onupdate, it would not have its parent “column” assigned, added test coverage for all column default assignment patterns. also in 0.6.8

  References: #2147

### postgresql

- [postgresql]

  Fixed the psycopg2_version parsing in the psycopg2 dialect.

- [postgresql]

  Fixed bug affecting PG 9 whereby index reflection would fail if against a column whose name had changed. . Also in 0.6.8.

  References: #2141

### mssql

- [mssql]

  Fixed bug in MSSQL dialect whereby the aliasing applied to a schema-qualified table would leak into enclosing select statements. Also in 0.6.8.

  References: #2169

### misc

- [no_tags]

  This section documents those changes from 0.7b4 to 0.7.0. For an overview of what’s new in SQLAlchemy 0.7, see https://docs.sqlalchemy.org/en/latest/changelog/migration_07.html

- [documentation]

  Removed the usage of the “collections.MutableMapping” abc from the ext.mutable docs as it was being used incorrectly and makes the example more difficult to understand in any case.

  References: #2152

- [ext]

  Fixed bugs in sqlalchemy.ext.mutable extension where None was not appropriately handled, replacement events were not appropriately handled.

  References: #2143

## 0.7.0b4

Released: Sun Apr 17 2011

### general

- [general]

  Changes to the format of CHANGES, this file. The format changes have been applied to the 0.7 releases.

- [general]

  The “-declarative” changes will now be listed directly under the “-orm” section, as these are closely related.

- [general]

  The 0.5 series changes have been moved to the file CHANGES_PRE_06 which replaces CHANGES_PRE_05.

- [general]

  The changelog for 0.6.7 and subsequent within the 0.6 series is now listed only in the CHANGES file within the 0.6 branch. In the 0.7 CHANGES file (i.e. this file), all the 0.6 changes are listed inline within the 0.7 section in which they were also applied (since all 0.6 changes are in 0.7 as well). Changes that apply to an 0.6 version here are noted as are if any differences in implementation/behavior are present.

### orm

- [orm]

  Some fixes to “evaluate” and “fetch” evaluation when query.update(), query.delete() are called. The retrieval of records is done after autoflush in all cases, and before update/delete is emitted, guarding against unflushed data present as well as expired objects failing during the evaluation.

  References: #2122

- [orm]

  Reworded the exception raised when a flush is attempted of a subclass that is not polymorphic against the supertype.

  References: #2063

- [orm]

  Still more wording adjustments when a query option can’t find the target entity. Explain that the path must be from one of the root entities.

- [orm]

  Some fixes to the state handling regarding backrefs, typically when autoflush=False, where the back-referenced collection wouldn’t properly handle add/removes with no net change. Thanks to Richard Murri for the test case + patch. (also in 0.6.7).

  References: #2123

- [orm]

  Added checks inside the UOW to detect the unusual condition of being asked to UPDATE or DELETE on a primary key value that contains NULL in it.

  References: #2127

- [orm]

  Some refinements to attribute history. More changes are pending possibly in 0.8, but for now history has been modified such that scalar history doesn’t have a “side effect” of populating None for a non-present value. This allows a slightly better ability to distinguish between a None set and no actual change, affects as well.

  References: #2127

- [orm]

  a “having” clause would be copied from the inside to the outside query if from_self() were used; in particular this would break an 0.7 style count() query. (also in 0.6.7)

  References: #2130

- [orm]

  the Query.execution_options() method now passes those options to the Connection rather than the SELECT statement, so that all available options including isolation level and compiled cache may be used.

  References: #2131

### engine

- [engine]

  The C extension is now enabled by default on CPython 2.x with a fallback to pure python if it fails to compile.

  References: #2129

### sql

- [sql]

  The “compiled_cache” execution option now raises an error when passed to a SELECT statement rather than a Connection. Previously it was being ignored entirely. We may look into having this option work on a per-statement level at some point.

  References: #2131

- [sql]

  Restored the “catchall” constructor on the base TypeEngine class, with a deprecation warning. This so that code which does something like Integer(11) still succeeds.

- [sql]

  Fixed regression whereby MetaData() coming back from unpickling did not keep track of new things it keeps track of now, i.e. collection of Sequence objects, list of schema names.

  References: #2104

- [sql]

  The limit/offset keywords to select() as well as the value passed to select.limit()/offset() will be coerced to integer. (also in 0.6.7)

  References: #2116

- [sql]

  fixed bug where “from” clause gathering from an over() clause would be an itertools.chain() and not a list, causing “can only concatenate list” TypeError when combined with other clauses.

- [sql]

  Fixed incorrect usage of “,” in over() clause being placed between the “partition” and “order by” clauses.

  References: #2134

- [sql]

  Before/after attach events for PrimaryKeyConstraint now function, tests added for before/after events on all constraint types.

  References: #2105

- [sql]

  Added explicit true()/false() constructs to expression lib - coercion rules will intercept “False”/”True” into these constructs. In 0.6, the constructs were typically converted straight to string, which was no longer accepted in 0.7.

  References: #2117

### schema

- [schema]

  The ‘useexisting’ flag on Table has been superseded by a new pair of flags ‘keep_existing’ and ‘extend_existing’. ‘extend_existing’ is equivalent to ‘useexisting’ - the existing Table is returned, and additional constructor elements are added. With ‘keep_existing’, the existing Table is returned, but additional constructor elements are not added - these elements are only applied when the Table is newly created.

  References: #2109

### postgresql

- [postgresql]

  Psycopg2 for Python 3 is now supported.

- [postgresql]

  Fixed support for precision numerics when using pg8000.

  References: #2132

### sqlite

- [sqlite]

  Fixed bug where reflection of foreign key created as “REFERENCES <tablename>” without col name would fail. (also in 0.6.7)

  References: #2115

### oracle

- [oracle]

  Using column names that would require quotes for the column itself or for a name-generated bind parameter, such as names with special characters, underscores, non-ascii characters, now properly translate bind parameter keys when talking to cx_oracle. (Also in 0.6.7)

  References: #2100

- [oracle]

  Oracle dialect adds use_binds_for_limits=False create_engine() flag, will render the LIMIT/OFFSET values inline instead of as binds, reported to modify the execution plan used by Oracle. (Also in 0.6.7)

  References: #2116

### misc

- [types]

  REAL has been added to the core types. Supported by PostgreSQL, SQL Server, MySQL, SQLite. Note that the SQL Server and MySQL versions, which add extra arguments, are also still available from those dialects.

  References: #2081

- [types]

  Added @event.listens_for() decorator, given target + event name, applies the decorated function as a listener.

  References: #2106

- [pool]

  AssertionPool now stores the traceback indicating where the currently checked out connection was acquired; this traceback is reported within the assertion raised upon a second concurrent checkout; courtesy Gunnlaugur Briem

  References: #2103

- [pool]

  The “pool.manage” feature doesn’t use pickle anymore to hash the arguments for each pool.

- [documentation]

  Documented SQLite DATE/TIME/DATETIME types. (also in 0.6.7)

  References: #2029

- [documentation]

  Fixed mutable extension docs to show the correct type-association methods.

  References: #2118

## 0.7.0b3

Released: Sun Mar 20 2011

### general

- [general]

  Lots of fixes to unit tests when run under PyPy (courtesy Alex Gaynor).

### orm

- [orm]

  Changed the underlying approach to query.count(). query.count() is now in all cases exactly:

  > query.

  >   from_self(func.count(literal_column(‘1’))). scalar()

  That is, “select count(1) from (<full query>)”. This produces a subquery in all cases, but vastly simplifies all the guessing count() tried to do previously, which would still fail in many scenarios particularly when joined table inheritance and other joins were involved. If the subquery produced for an otherwise very simple count is really an issue, use query(func.count()) as an optimization.

  References: #2093

- [orm]

  some changes to the identity map regarding rare weakref callbacks during iterations. The mutex has been removed as it apparently can cause a reentrant (i.e. in one thread) deadlock, perhaps when gc collects objects at the point of iteration in order to gain more memory. It is hoped that “dictionary changed during iteration” will be exceedingly rare as iteration methods internally acquire the full list of objects in a single values() call. Note 0.6.7 has a more conservative fix here which still keeps the mutex in place.

  References: #2087

- [orm]

  A tweak to the unit of work causes it to order the flush along relationship() dependencies even if the given objects don’t have any inter-attribute references in memory, which was the behavior in 0.5 and earlier, so a flush of Parent/Child with only foreign key/primary key set will succeed. This while still maintaining 0.6 and above’s not generating a ton of useless internal dependency structures within the flush that don’t correspond to state actually within the current flush.

  References: #2082

- [orm]

  Improvements to the error messages emitted when querying against column-only entities in conjunction with (typically incorrectly) using loader options, where the parent entity is not fully present.

  References: #2069

- [orm]

  Fixed bug in query.options() whereby a path applied to a lazyload using string keys could overlap a same named attribute on the wrong entity. Note 0.6.7 has a more conservative fix to this.

  References: #2098

### examples

- [examples]

  Updated the association, association proxy examples to use declarative, added a new example dict_of_sets_with_default.py, a “pushing the envelope” example of association proxy.

- [examples]

  The Beaker caching example allows a “query_cls” argument to the query_callable() function. (also in 0.6.7)

  References: #2090

### engine

- [engine]

  Fixed AssertionPool regression bug.

  References: #2097

- [engine]

  Changed exception raised to ArgumentError when an invalid dialect is specified.

  References: #2060

### sql

- [sql]

  Added a fully descriptive error message for the case where Column is subclassed and _make_proxy() fails to make a copy due to TypeError on the constructor. The method _constructor should be implemented in this case.

- [sql]

  Added new event “column_reflect” for Table objects. Receives the info dictionary about a Column before the object is generated within reflection, and allows modification to the dictionary for control over most aspects of the resulting Column including key, name, type, info dictionary.

  References: #2095

- [sql]

  To help with the “column_reflect” event being used with specific Table objects instead of all instances of Table, listeners can be added to a Table object inline with its construction using a new argument “listeners”, a list of tuples of the form (<eventname>, <fn>), which are applied to the Table before the reflection process begins.

- [sql]

  Added new generic function “next_value()”, accepts a Sequence object as its argument and renders the appropriate “next value” generation string on the target platform, if supported. Also provides “.next_value()” method on Sequence itself.

  References: #2085

- [sql]

  func.next_value() or other SQL expression can be embedded directly into an insert() construct, and if implicit or explicit “returning” is used in conjunction with a primary key column, the newly generated value will be present in result.inserted_primary_key.

  References: #2084

- [sql]

  Added accessors to ResultProxy “returns_rows”, “is_insert” (also in 0.6.7)

  References: #2089

### postgresql

- [postgresql]

  Added RESERVED_WORDS for postgresql dialect. (also in 0.6.7)

  References: #2092

- [postgresql]

  Fixed the BIT type to allow a “length” parameter, “varying” parameter. Reflection also fixed. (also in 0.6.7)

  References: #2073

### mssql

- [mssql]

  Rewrote the query used to get the definition of a view, typically when using the Inspector interface, to use sys.sql_modules instead of the information schema, thereby allowing views definitions longer than 4000 characters to be fully returned. (also in 0.6.7)

  References: #2071

### firebird

- [firebird]

  The “implicit_returning” flag on create_engine() is honored if set to False. (also in 0.6.7)

  References: #2083

### misc

- [declarative]

  Arguments in __mapper_args__ that aren’t “hashable” aren’t mistaken for always-hashable, possibly-column arguments. (also in 0.6.7)

  References: #2091

- [informix]

  Added RESERVED_WORDS informix dialect. (also in 0.6.7)

  References: #2092

- [ext]

  The horizontal_shard ShardedSession class accepts the common Session argument “query_cls” as a constructor argument, to enable further subclassing of ShardedQuery. (also in 0.6.7)

  References: #2090

## 0.7.0b2

Released: Sat Feb 19 2011

### orm

- [orm]

  Fixed bug whereby Session.merge() would call the load() event with one too few arguments.

  References: #2053

- [orm]

  Added logic which prevents the generation of events from a MapperExtension or SessionExtension from generating do-nothing events for all the methods not overridden.

  References: #2052

### examples

- [examples]

  Beaker example now takes into account ‘limit’ and ‘offset’, bind params within embedded FROM clauses (like when you use union() or from_self()) when generating a cache key.

### sql

- [sql]

  Renamed the EngineEvents event class to ConnectionEvents. As these classes are never accessed directly by end-user code, this strictly is a documentation change for end users. Also simplified how events get linked to engines and connections internally.

  References: #2059

- [sql]

  The Sequence() construct, when passed a MetaData() object via its ‘metadata’ argument, will be included in CREATE/DROP statements within metadata.create_all() and metadata.drop_all(), including “checkfirst” logic.

  References: #2055

- [sql]

  The Column.references() method now returns True if it has a foreign key referencing the given column exactly, not just its parent table.

  References: #2064

### postgresql

- [postgresql]

  Fixed regression from 0.6 where SMALLINT and BIGINT types would both generate SERIAL on an integer PK column, instead of SMALLINT and BIGSERIAL

  References: #2065

### misc

- [declarative]

  Fixed regression whereby composite() with Column objects placed inline would fail to initialize. The Column objects can now be inline with the composite() or external and pulled in via name or object ref.

  References: #2058

- [declarative]

  Fix error message referencing old @classproperty name to reference @declared_attr (also in 0.6.7)

  References: #2061

- [declarative]

  the dictionary at the end of the __table_args__ tuple is now optional.

  References: #1468

- [ext]

  Association proxy now has correct behavior for any(), has(), and contains() when proxying a many-to-one scalar attribute to a one-to-many collection (i.e. the reverse of the ‘typical’ association proxy use case)

  References: #2054

## 0.7.0b1

Released: Sat Feb 12 2011

### general

- [general]

  New event system, supersedes all extensions, listeners, etc.

  References: #1902

- [general]

  Logging enhancements

  References: #1926

- [general]

  Setup no longer installs a Nose plugin

  References: #1949

- [general]

  The “sqlalchemy.exceptions” alias in sys.modules has been removed. Base SQLA exceptions are available via “from sqlalchemy import exc”. The “exceptions” alias for “exc” remains in “sqlalchemy” for now, it’s just not patched into sys.modules.

### orm

- [orm]

  More succinct form of query.join(target, onclause)

  References: #1923

- [orm]

  Hybrid Attributes, implements/supersedes synonym()

  References: #1903

- [orm]

  Rewrite of composites

  References: #2008

- [orm]

  Mutation Event Extension, supersedes “mutable=True”

  See also

  Mutation event extension, supersedes “mutable=True”

- [orm]

  PickleType and ARRAY mutability turned off by default

  References: #1980

- [orm]

  Simplified polymorphic_on assignment

  References: #1895

- [orm]

  Flushing of Orphans that have no parent is allowed

  References: #1912

- [orm]

  Adjusted flush accounting step to occur before the commit in the case of autocommit=True. This allows autocommit=True to work appropriately with expire_on_commit=True, and also allows post-flush session hooks to operate in the same transactional context as when autocommit=False.

  References: #2041

- [orm]

  Warnings generated when collection members, scalar referents not part of the flush

  References: #1973

- [orm]

  Non-Table-derived constructs can be mapped

  References: #1876

- [orm]

  Tuple label names in Query Improved

  References: #1942

- [orm]

  Mapped column attributes reference the most specific column first

  References: #1892

- [orm]

  Mapping to joins with two or more same-named columns requires explicit declaration

  References: #1896

- [orm]

  Mapper requires that polymorphic_on column be present in the mapped selectable

  References: #1875

- [orm]

  compile_mappers() renamed configure_mappers(), simplified configuration internals

  References: #1966

- [orm]

  the aliased() function, if passed a SQL FromClause element (i.e. not a mapped class), will return element.alias() instead of raising an error on AliasedClass.

  References: #2018

- [orm]

  Session.merge() will check the version id of the incoming state against that of the database, assuming the mapping uses version ids and incoming state has a version_id assigned, and raise StaleDataError if they don’t match.

  References: #2027

- [orm]

  Session.connection(), Session.execute() accept ‘bind’, to allow execute/connection operations to participate in the open transaction of an engine explicitly.

  References: #1996

- [orm]

  Query.join(), Query.outerjoin(), eagerload(), eagerload_all(), others no longer allow lists of attributes as arguments (i.e. option([x, y, z]) form, deprecated since 0.5)

- [orm]

  ScopedSession.mapper is removed (deprecated since 0.5).

- [orm]

  Horizontal shard query places ‘shard_id’ in context.attributes where it’s accessible by the “load()” event.

  References: #2031

- [orm]

  A single contains_eager() call across multiple entities will indicate all collections along that path should load, instead of requiring distinct contains_eager() calls for each endpoint (which was never correctly documented).

  References: #2032

- [orm]

  The “name” field used in orm.aliased() now renders in the resulting SQL statement.

- [orm]

  Session weak_instance_dict=False is deprecated.

  References: #1473

- [orm]

  An exception is raised in the unusual case that an append or similar event on a collection occurs after the parent object has been dereferenced, which prevents the parent from being marked as “dirty” in the session. Was a warning in 0.6.6.

  References: #2046

- [orm]

  Query.distinct() now accepts column expressions as *args, interpreted by the PostgreSQL dialect as DISTINCT ON (<expr>).

  References: #1069

- [orm]

  Additional tuning to “many-to-one” relationship loads during a flush(). A change in version 0.6.6 ([ticket:2002]) required that more “unnecessary” m2o loads during a flush could occur. Extra loading modes have been added so that the SQL emitted in this specific use case is trimmed back, while still retrieving the information the flush needs in order to not miss anything.

  References: #2049

- [orm]

  the value of “passive” as passed to attributes.get_history() should be one of the constants defined in the attributes package. Sending True or False is deprecated.

- [orm]

  Added a name argument to Query.subquery(), to allow a fixed name to be assigned to the alias object. (also in 0.6.7)

  References: #2030

- [orm]

  A warning is emitted when a joined-table inheriting mapper has no primary keys on the locally mapped table (but has pks on the superclass table). (also in 0.6.7)

  References: #2019

- [orm]

  Fixed bug where “middle” class in a polymorphic hierarchy would have no ‘polymorphic_on’ column if it didn’t also specify a ‘polymorphic_identity’, leading to strange errors upon refresh, wrong class loaded when querying from that target. Also emits the correct WHERE criterion when using single table inheritance. (also in 0.6.7)

  References: #2038

- [orm]

  Fixed bug where a column with a SQL or server side default that was excluded from a mapping with include_properties or exclude_properties would result in UnmappedColumnError. (also in 0.6.7)

  References: #1995

- [orm]

  A warning is emitted in the unusual case that an append or similar event on a collection occurs after the parent object has been dereferenced, which prevents the parent from being marked as “dirty” in the session. This will be an exception in 0.7. (also in 0.6.7)

  References: #2046

### sql

- [sql]

  Added over() function, method to FunctionElement classes, produces the _Over() construct which in turn generates “window functions”, i.e. “<window function> OVER (PARTITION BY <partition by>, ORDER BY <order by>)”.

  References: #1844

- [sql]

  LIMIT/OFFSET clauses now use bind parameters

  References: #805

- [sql]

  select.distinct() now accepts column expressions as *args, interpreted by the PostgreSQL dialect as DISTINCT ON (<expr>). Note this was already available via passing a list to the distinct keyword argument to select().

  References: #1069

- [sql]

  select.prefix_with() accepts multiple expressions (i.e. *expr), ‘prefix’ keyword argument to select() accepts a list or tuple.

- [sql]

  Passing a string to the distinct keyword argument of select() for the purpose of emitting special MySQL keywords (DISTINCTROW etc.) is deprecated - use prefix_with() for this.

- [sql]

  TypeDecorator works with primary key columns

  References: #2005, #2006

- [sql]

  DDL() constructs now escape percent signs

  References: #1897

- [sql]

  Table.c / MetaData.tables refined a bit, don’t allow direct mutation

  References: #1893, #1917

- [sql]

  Callables passed to bindparam() don’t get evaluated

  References: #1950

- [sql]

  types.type_map is now private, types._type_map

  References: #1870

- [sql]

  Non-public Pool methods underscored

  References: #1982

- [sql]

  Added NULLS FIRST and NULLS LAST support. It’s implemented as an extension to the asc() and desc() operators, called nullsfirst() and nullslast().

  References: #723

- [sql]

  The Index() construct can be created inline with a Table definition, using strings as column names, as an alternative to the creation of the index outside of the Table.

- [sql]

  execution_options() on Connection accepts “isolation_level” argument, sets transaction isolation level for that connection only until returned to the connection pool, for those backends which support it (SQLite, PostgreSQL)

  References: #2001

- [sql]

  A TypeDecorator of Integer can be used with a primary key column, and the “autoincrement” feature of various dialects as well as the “sqlite_autoincrement” flag will honor the underlying database type as being Integer-based.

  References: #2005

- [sql]

  Established consistency when server_default is present on an Integer PK column. SQLA doesn’t pre-fetch these, nor do they come back in cursor.lastrowid (DBAPI). Ensured all backends consistently return None in result.inserted_primary_key for these. Regarding reflection for this case, reflection of an int PK col with a server_default sets the “autoincrement” flag to False, except in the case of a PG SERIAL col where we detected a sequence default.

  References: #2020, #2021

- [sql]

  Result-row processors are applied to pre-executed SQL defaults, as well as cursor.lastrowid, when determining the contents of result.inserted_primary_key.

  References: #2006

- [sql]

  Bind parameters present in the “columns clause” of a select are now auto-labeled like other “anonymous” clauses, which among other things allows their “type” to be meaningful when the row is fetched, as in result row processors.

- [sql]

  TypeDecorator is present in the “sqlalchemy” import space.

- [sql]

  Non-DBAPI errors which occur in the scope of an execute() call are now wrapped in sqlalchemy.exc.StatementError, and the text of the SQL statement and repr() of params is included. This makes it easier to identify statement executions which fail before the DBAPI becomes involved.

  References: #2015

- [sql]

  The concept of associating a “.bind” directly with a ClauseElement has been explicitly moved to Executable, i.e. the mixin that describes ClauseElements which represent engine-executable constructs. This change is an improvement to internal organization and is unlikely to affect any real-world usage.

  References: #2048

- [sql]

  Column.copy(), as used in table.tometadata(), copies the ‘doc’ attribute. (also in 0.6.7)

  References: #2028

- [sql]

  Added some defs to the resultproxy.c extension so that the extension compiles and runs on Python 2.4. (also in 0.6.7)

  References: #2023

- [sql]

  The compiler extension now supports overriding the default compilation of expression._BindParamClause including that the auto-generated binds within the VALUES/SET clause of an insert()/update() statement will also use the new compilation rules. (also in 0.6.7)

  References: #2042

- [sql]

  SQLite dialect now uses NullPool for file-based databases

  References: #1921

- [sql]

  The path given as the location of a sqlite database is now normalized via os.path.abspath(), so that directory changes within the process don’t affect the ultimate location of a relative file path.

  References: #2036

### postgresql

- [postgresql]

  When explicit sequence execution derives the name of the auto-generated sequence of a SERIAL column, which currently only occurs if implicit_returning=False, now accommodates if the table + column name is greater than 63 characters using the same logic PostgreSQL uses. (also in 0.6.7)

  References: #1083

- [postgresql]

  Added an additional libpq message to the list of “disconnect” exceptions, “could not receive data from server” (also in 0.6.7)

  References: #2044

### mysql

- [mysql]

  New DBAPI support for pymysql, a pure Python port of MySQL-python.

  References: #1991

- [mysql]

  oursql dialect accepts the same “ssl” arguments in create_engine() as that of MySQLdb. (also in 0.6.7)

  References: #2047

### mssql

- [mssql]

  the String/Unicode types, and their counterparts VARCHAR/ NVARCHAR, emit “max” as the length when no length is specified, so that the default length, normally ‘1’ as per SQL server documentation, is instead ‘unbounded’. This also occurs for the VARBINARY type..

  This behavior makes these types more closely compatible with PostgreSQL’s VARCHAR type which is similarly unbounded when no length is specified.

  References: #1833

### firebird

- [firebird]

  Some adjustments so that Interbase is supported as well. FB/Interbase version idents are parsed into a structure such as (8, 1, 1, ‘interbase’) or (2, 1, 588, ‘firebird’) so they can be distinguished.

  References: #1885

### misc

- [no_tags]

  Detailed descriptions of each change below are described at: https://docs.sqlalchemy.org/en/latest/changelog/migration_07.html

- [declarative]

  Added an explicit check for the case that the name ‘metadata’ is used for a column attribute on a declarative class. (also in 0.6.7)

  References: #2050