Sqlalchemy

:released: Sat Jun 16 2012

.. change::
:tags: orm, bug
:tickets: 2480

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.

.. change::
:tags: orm, bug
:tickets: 2491, 1892

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.

.. change::
:tags: orm, feature
:tickets:

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

.. change::
:tags: orm, bug
:tickets: 2508

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

.. change::
:tags: orm, bug
:tickets: 2497

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

.. change::
:tags: bug, sql
:tickets: 2499

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

.. change::
:tags: bug, sql
:tickets: 2490

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

.. change::
:tags: bug, sql
:tickets: 2482

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

.. change::
:tags: engine, bug
:tickets: 2489

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.

.. change::
:tags: engine, bug
:tickets: 2503

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..

.. change::
:tags: postgresql, bug
:tickets: 2510

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

.. change::
:tags: oracle, bug
:tickets: 2483

Added ROWID to oracle.*.

.. change::
:tags: feature, mysql
:tickets: 2484

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

.. changelog::

:released: Sat May 05 2012

.. change::
:tags: orm, bug
:tickets: 2477

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..

.. change::
:tags: orm, feature
:tickets: 2443

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

.. change::
:tags: orm, bug
:tickets: 2409

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.

.. change::
:tags: orm, feature
:tickets:

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.

.. change::
:tags: orm, bug
:tickets: 2449

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.

.. change::
:tags: orm, bug
:tickets: 2453

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

.. change::
:tags: orm, bug
:tickets: 2454

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

.. change::
:tags: orm, bug
:tickets:

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

.. change::
:tags: bug, sql
:tickets:

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.

.. change::
:tags: feature, sql
:tickets:

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.

.. change::
:tags: bug, sql
:tickets:

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

.. change::
:tags: bug, sql
:tickets: 2474

Add BINARY, VARBINARY to types.__all__.

.. change::
:tags: mssql, feature
:tickets:

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.

.. change::
:tags: mssql, bug
:tickets:

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.

.. change::
:tags: mssql, bug
:tickets: 2468

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.

.. change::
:tags: postgresql, feature
:tickets: 2445

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

.. change::
:tags: postgresql, bug
:tickets: 2473

removed unnecessary table clause
when reflecting domains.

.. change::
:tags: bug, mysql
:tickets: 2460

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.

.. change::
:tags: bug, mysql
:tickets:

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

.. change::
:tags: bug, mysql
:tickets: 2467

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.

.. change::
:tags: sqlite, feature
:tickets: 2475

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

.. change::
:tags: sqlite, bug
:tickets: 2525

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.

.. changelog::

:released: Wed Mar 14 2012

.. change::
:tags: orm, bug
:tickets: 2424

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.

.. change::
:tags: orm, bug
:tickets: 2425

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.

.. change::
:tags: orm, feature
:tickets:

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

.. change::
:tags: orm, feature
:tickets: 1859

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

.. change::
:tags: orm, bug
:tickets: 2403

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.

.. change::
:tags: orm, bug
:tickets: 2409

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

.. change::
:tags: orm, bug
:tickets: 2406

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.

.. change::
:tags: orm, bug
:tickets: 2419

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.

.. change::
:tags: orm, bug
:tickets: 2417

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

.. change::
:tags: orm, feature
:tickets: 2400

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

.. change::
:tags: orm, bug
:tickets:

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.

.. change::
:tags: orm, bug
:tickets: 2390

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.

.. change::
:tags: orm, bug
:tickets: 2352

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.

.. change::
:tags: bug, sql
:tickets: 2427

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.

.. change::
:tags: bug, sql
:tickets: 2398

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.

.. change::
:tags: feature, sql
:tickets: 1859

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.

.. change::
:tags: bug, sql
:tickets: 2392

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.

.. change::
:tags: bug, sql
:tickets: 2413

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.

.. change::
:tags: bug, sql
:tickets: 2396

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.

.. change::
:tags: bug, sql
:tickets: 2402

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

.. change::
:tags: bug, sql
:tickets: 2380

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

.. change::
:tags: engine, feature
:tickets: 2407

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).

.. change::
:tags: engine, bug
:tickets:

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

.. change::
:tags: engine, feature
:tickets: 2378

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.

.. change::
:tags: engine, feature
:tickets:

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().

.. change::
:tags: sqlite, bug
:tickets: 2432

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.

.. change::
:tags: mssql, feature
:tickets: 2430

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

.. change::
:tags: feature, mysql
:tickets: 2386

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.

.. change::
:tags: feature, mysql
:tickets: 2394

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

.. change::
:tags: oracle, feature
:tickets: 2399

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.

.. change::
:tags: oracle, bug
:tickets: 2401

Added missing compilation support for
LONG

.. change::
:tags: oracle, bug
:tickets: 2435

Added 'LEVEL' to the list of reserved
words for Oracle.

.. change::
:tags: examples, bug
:tickets:

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.

.. changelog::

:released: Sat Jan 28 2012

.. change::
:tags: orm, bug
:tickets: 2389

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.

.. change::
:tags: orm, bug
:tickets: 2345

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

.. change::
:tags: orm, bug
:tickets: 2370

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

.. change::
:tags: orm, feature
:tickets:

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

.. change::
:tags: orm, feature
:tickets:

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

.. change::
:tags: orm, feature
:tickets: 2351

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 !

.. change::
:tags: orm, bug
:tickets: 2367

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 ??)

.. change::
:tags: orm, bug
:tickets:

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

.. change::
:tags: orm
:tickets:

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.

.. change::
:tags: orm, bug
:tickets: 2371

ensure pickleability of all ORM exceptions
for multiprocessing compatibility.

.. change::
:tags: orm, bug
:tickets: 2353

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.

.. change::
:tags: orm, bug
:tickets: 2362

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.

.. change::
:tags: orm, bug
:tickets: 2374

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.

.. change::
:tags: orm, feature
:tickets: 2356

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

.. change::
:tags: feature, sql
:tickets: 2356

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.

.. change::
:tags: bug, sql
:tickets: 2356

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.

.. change::
:tags: feature, sql
:tickets:

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

.. change::
:tags: feature, sql
:tickets: 2361

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.

.. change::
:tags: bug, sql
:tickets: 2381

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

.. change::
:tags: engine, bug
:tickets: 2371

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.

.. change::
:tags: engine, bug
:tickets: 2382

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.

.. change::
:tags: engine, bug
:tickets: 2377

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.

.. change::
:tags: engine, bug
:tickets: 2384

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

.. change::
:tags: sqlite, bug
:tickets: 2364

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.

.. change::
:tags: sqlite, bug
:tickets: 2368

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

.. change::
:tags: sqlite, bug
:tickets:

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.

.. change::
:tags: bug, mysql
:tickets: 2376

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

.. change::
:tags: mssql, bug
:tickets: 2340

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.

.. change::
:tags: mssql, bug
:tickets: 2347

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.

.. change::
:tags: oracle, bug
:tickets: 2388

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

.. change::
:tags: core, bug
:tickets: 2379

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.

.. change::
:tags: core, bug
:tickets: 2383

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.

.. change::
:tags: bug, py3k
:tickets: 2348

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.

.. change::
:tags: examples, feature
:tickets: 2313

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

.. change::
:tags: examples, bug
:tickets: 2346

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

.. changelog::

:released: Fri Dec 09 2011

.. change::
:tags: orm, bug
:tickets: 2315

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.

.. change::
:tags: orm, bug
:tickets: 2264

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.

.. change::
:tags: orm, bug
:tickets: 2310

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

.. change::
:tags: orm, bug
:tickets: 2304

Added missing comma to PASSIVE_RETURN_NEVER_SET
symbol

.. change::
:tags: orm, bug
:tickets: 1776

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

.. change::
:tags: orm, bug
:tickets: 2309

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.

.. change::
:tags: orm, bug
:tickets: 2309, 2308

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.

.. change::
:tags: orm, bug
:tickets: 2312

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

.. change::
:tags: orm, bug
:tickets: 2312

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.

.. change::
:tags: orm, bug
:tickets: 2316

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.

.. change::
:tags: orm, bug
:tickets: 2297

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

.. change::
:tags: orm, bug
:tickets: 2328

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.

.. change::
:tags: orm, bug
:tickets: 2339

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

.. change::
:tags: orm, bug
:tickets: 2325

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.

.. change::
:tags: orm, feature
:tickets: 2345, 2238

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.

.. change::
:tags: orm, feature
:tickets: 2301

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

.. change::
:tags: orm, feature
:tickets:

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.

.. change::
:tags: orm, bug
:tickets:

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.

.. change::
:tags: bug, sql
:tickets: 2316, 2261

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 :).

.. change::
:tags: feature, sql
:tickets: 2166, 1944

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.

.. change::
:tags: feature, sql
:tickets: 77

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

.. change::
:tags: bug, sql
:tickets: 2261, 2319

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.

.. change::
:tags: engine, bug
:tickets: 2317

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.

.. change::
:tags: feature, schema
:tickets:

Added new support for remote "schemas":

.. change::
:tags: schema
:tickets:

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``.

.. change::
:tags: schema
:tickets:

Sequence accepts "quote_schema" argument

.. change::
:tags: schema
:tickets:

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

.. change::
:tags: schema
:tickets:

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

.. change::
:tags: schema
:tickets:

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".

.. change::
:tags: schema
:tickets: 1679

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

.. change::
:tags: feature, schema
:tickets: 1410

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.

.. change::
:tags: bug, schema
:tickets:

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

.. change::
:tags: bug, schema
:tickets:

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

.. change::
:tags: bug, schema
:tickets: 2305

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

.. change::
:tags: pyodbc, bug
:tickets: 2318

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

.. change::
:tags: postgresql, bug
:tickets: 2311

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.

.. change::
:tags: postgresql, feature
:tickets:

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.

.. change::
:tags: mssql, feature
:tickets: 822

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

.. change::
:tags: mssql, bug
:tickets: 2336

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 :) )

.. change::
:tags: mssql, bug
:tickets: 2318

use new pyodbc version detection for
_need_decimal_fix option.

.. change::
:tags: mssql, bug
:tickets: 2343

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.

.. change::
:tags: mssql, bug
:tickets: 2269

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

.. change::
:tags: bug, mysql
:tickets:

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

.. change::
:tags: ext, feature
:tickets:

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.

.. change::
:tags: ext, bug
:tickets:

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

.. change::
:tags: examples, bug
:tickets:

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.

.. changelog::

:released: Sun Oct 16 2011

.. change::
:tags: general
:tickets: 2279

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.

.. change::
:tags: orm
:tickets: 2298

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.

.. change::
:tags: orm
:tickets: 2241

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.

.. change::
:tags: orm
:tickets:

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.

.. change::
:tags: orm
:tickets:

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.

.. change::
:tags: orm
:tickets: 2237

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.

.. change::
:tags: orm
:tickets: 2282

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.

.. change::
:tags: orm
:tickets:

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().

.. change::
:tags: orm
:tickets: 2287

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

.. change::
:tags: orm
:tickets: 2267

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

.. change::
:tags: orm
:tickets: 2253

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

.. change::
:tags: orm
:tickets: 2248

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

.. change::
:tags: orm
:tickets: 2247

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.

.. change::
:tags: orm
:tickets:

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

.. change::
:tags: orm
:tickets:

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.

.. change::
:tags: orm
:tickets: 2260

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.

.. change::
:tags: orm
:tickets: 2196

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.

.. change::
:tags: orm
:tickets:

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.

.. change::
:tags: orm
:tickets: 2281

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.

.. change::
:tags: orm
:tickets: 2239

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.

.. change::
:tags: orm
:tickets: 2283

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

.. change::
:tags: orm
:tickets: 2280

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.

.. change::
:tags: orm
:tickets: 2257

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
()'..

.. change::
:tags: orm
:tickets: 2261

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.

.. change::
:tags: orm
:tickets: 2270

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

.. change::
:tags: schema
:tickets: 2284

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.

.. change::
:tags: schema
:tickets: 2223

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.

.. change::
:tags: engine
:tickets: 2254

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.

.. change::
:tags: engine
:tickets: 2243

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.

.. change::
:tags: engine
:tickets:

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

.. change::
:tags: engine
:tickets: 2286

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.

.. change::
:tags: engine
:tickets: 2299

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.

.. change::
:tags: types
:tickets: 2258

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

.. change::
:tags: sqlite
:tickets:

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.

.. change::
:tags: postgresql
:tickets: 2290

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

.. change::
:tags: postgresql
:tickets: 1839

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.

.. change::
:tags: postgresql
:tickets: 2291, 2141

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.

.. change::
:tags: postgresql
:tickets: 2256

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

.. change::
:tags: postgresql
:tickets:

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

.. change::
:tags: postgresql
:tickets: 2249

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.

.. change::
:tags: mysql
:tickets: 2225

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.

.. change::
:tags: mysql
:tickets: 2293

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

.. change::
:tags: mssql
:tickets: 2273

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.

.. change::
:tags: mssql
:tickets: 2277

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().

.. change::
:tags: mssql
:tickets: 2222

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

.. change::
:tags: oracle
:tickets: 2272

Fixed ReturningResultProxy for zxjdbc dialect.. Regression from 0.6.

.. change::
:tags: oracle
:tickets: 2252

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.

.. change::
:tags: ext
:tickets: 2262

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.

.. change::
:tags: ext
:tickets: 2236

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

.. change::
:tags: ext
:tickets: 2275

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.

.. change::
:tags: examples
:tickets: 2266

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

.. changelog::