sqlalchemy / CHANGES

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-*- coding: utf-8; fill-column: 68 -*-

=======
CHANGES
=======
0.6.1
=====
- orm
  - Fixed regression introduced in 0.6.0 involving improper
    history accounting on mutable attributes.  [ticket:1782]
  
  - Fixed regression introduced in 0.6.0 unit of work refactor
    that broke updates for bi-directional relationship()
    with post_update=True. [ticket:1807]
    
  - session.merge() will not expire attributes on the returned
    instance if that instance is "pending".  [ticket:1789]

  - fixed __setstate__ method of CollectionAdapter to not
    fail during deserialize where parent InstanceState not
    yet unserialized.  [ticket:1802]

  - Added internal warning in case an instance without a 
    full PK happened to be expired and then was asked
    to refresh. [ticket:1797]

  - Added more aggressive caching to the mapper's usage of
    UPDATE, INSERT, and DELETE expressions.  Assuming the 
    statement has no per-object SQL expressions attached,
    the expression objects are cached by the mapper after 
    the first create, and their compiled form is stored
    persistently in a cache dictionary for the duration of
    the related Engine.  The cache is an LRUCache for the
    rare case that a mapper receives an extremely
    high number of different column patterns as UPDATEs.
    
- sql
  - expr.in_() now accepts a text() construct as the argument.
    Grouping parenthesis are added automatically, i.e. usage
    is like `col.in_(text("select id from table"))`.
    [ticket:1793]

  - Columns of _Binary type (i.e. LargeBinary, BLOB, etc.)
    will coerce a "basestring" on the right side into a 
    _Binary as well so that required DBAPI processing 
    takes place.
    
  - Added table.add_is_dependent_on(othertable), allows manual
    placement of dependency rules between two Table objects
    for use within create_all(), drop_all(), sorted_tables.
    [ticket:1801]

  - Fixed bug that prevented implicit RETURNING from functioning
    properly with composite primary key that contained zeroes.
    [ticket:1778]
  
  - Fixed errant space character when generating ADD CONSTRAINT
    for a named UNIQUE constraint.

  - Fixed "table" argument on constructor of ForeginKeyConstraint
    [ticket:1571]

  - Fixed bug in connection pool cursor wrapper whereby if a
    cursor threw an exception on close(), the logging of the 
    message would fail.  [ticket:1786]

  - the _make_proxy() method of ColumnClause and Column now use
    self.__class__ to determine the class of object to be returned
    instead of hardcoding to ColumnClause/Column, making it slightly 
    easier to produce specific subclasses of these which work in 
    alias/subquery situations.

  - func.XXX() doesn't inadvertently resolve to non-Function 
    classes (e.g. fixes func.text()).  [ticket:1798]

- engines
  - Fixed building the C extensions on Python 2.4. [ticket:1781]

  - Pool classes will reuse the same "pool_logging_name" setting
    after a dispose() occurs.
    
  - Engine gains an "execution_options" argument and 
    update_execution_options() method, which will apply to 
    all connections generated by this engine.
    
- mysql
  - func.sysdate() emits "SYSDATE()", i.e. with the ending
    parenthesis, on MySQL.  [ticket:1794]

- sqlite
  - Fixed concatenation of constraints when "PRIMARY KEY" 
    constraint gets moved to column level due to SQLite
    AUTOINCREMENT keyword being rendered.  [ticket:1812]
    
- oracle
  - Added a check for cx_oracle versions lower than version 5,
    in which case the incompatible "output type handler" won't 
    be used.   This will impact decimal accuracy and some
    unicode handling issues.  [ticket:1775]

  - Fixed use_ansi=False mode, which was producing broken 
    WHERE clauses in pretty much all cases.  [ticket:1790]

  - Re-established support for Oracle 8 with cx_oracle, 
    including that use_ansi is set to False automatically, 
    NVARCHAR2 and NCLOB are not rendered for Unicode, 
    "native unicode" check doesn't fail, cx_oracle 
    "native unicode" mode is disabled, VARCHAR() is emitted 
    with bytes count instead of char count. [ticket:1808]
    
  - oracle_xe 5 doesn't accept a Python unicode object in 
    its connect string in normal Python 2.x mode - so we coerce
    to str() directly.  non-ascii characters aren't supported
    in connect strings here since we don't know what encoding
    we could use.  [ticket:1670]

  - FOR UPDATE is emitted in the syntactically correct position
    when limit/offset is used, i.e. the ROWNUM subquery.
    However, Oracle can't really handle FOR UPDATE with ORDER BY
    or with subqueries, so its still not very usable, but at
    least SQLA gets the SQL past the Oracle parser.
    [ticket:1815]
    
- firebird
  - Added a label to the query used within has_table() and 
    has_sequence() to work with older versions of Firebird
    that don't provide labels for result columns. [ticket:1521]
    
  - Added integer coercion to the "type_conv" attribute when 
    passed via query string, so that it is properly interpreted
    by Kinterbasdb. [ticket:1779]

  - Added 'connection shutdown' to the list of exception strings
    which indicate a dropped connection.  [ticket:1646]

- sqlsoup
  - the SqlSoup constructor accepts a `base` argument which specifies
    the base class to use for mapped classes, the default being
    `object`.  [ticket:1783]

0.6.0
=====

- orm
  - Unit of work internals have been rewritten.  Units of work
    with large numbers of objects interdependent objects 
    can now be flushed without recursion overflows 
    as there is no longer reliance upon recursive calls
    [ticket:1081].  The number of internal structures now stays 
    constant for a particular session state, regardless of 
    how many relationships are present on mappings.  The flow 
    of events now corresponds to a linear list of steps, 
    generated by the mappers and relationships based on actual
    work to be done, filtered through a single topological sort 
    for correct ordering.  Flush actions are assembled using 
    far fewer steps and less memory. [ticket:1742]

  - Along with the UOW rewrite, this also removes an issue
    introduced in 0.6beta3 regarding topological cycle detection 
    for units of work with long dependency cycles.  We now use
    an algorithm written by Guido (thanks Guido!).

  - one-to-many relationships now maintain a list of positive
    parent-child associations within the flush, preventing
    previous parents marked as deleted from cascading a 
    delete or NULL foreign key set on those child objects,
    despite the end-user not removing the child from the old
    association. [ticket:1764]

  - A collection lazy load will switch off default 
    eagerloading on the reverse many-to-one side, since 
    that loading is by definition unnecessary.  [ticket:1495]

  - Session.refresh() now does an equivalent expire()
    on the given instance first, so that the "refresh-expire"
    cascade is propagated.   Previously, refresh() was
    not affected in any way by the presence of "refresh-expire"
    cascade.   This is a change in behavior versus that
    of 0.6beta2, where the "lockmode" flag passed to refresh()
    would cause a version check to occur.  Since the instance
    is first expired, refresh() always upgrades the object
    to the most recent version.
    
  - The 'refresh-expire' cascade, when reaching a pending object,
    will expunge the object if the cascade also includes
    "delete-orphan", or will simply detach it otherwise.
    [ticket:1754]

  - id(obj) is no longer used internally within topological.py,
    as the sorting functions now require hashable objects
    only.  [ticket:1756]

  - The ORM will set the docstring of all generated descriptors
    to None by default.  This can be overridden using 'doc'
    (or if using Sphinx, attribute docstrings work too).
    
  - Added kw argument 'doc' to all mapper property callables 
    as well as Column().  Will assemble the string 'doc' as 
    the '__doc__' attribute on the descriptor.  

  - Usage of version_id_col on a backend that supports 
    cursor.rowcount for execute() but not executemany() now works
    when a delete is issued (already worked for saves, since those
    don't use executemany()). For a backend that doesn't support 
    cursor.rowcount at all, a warning is emitted the same
    as with saves.  [ticket:1761]

  - The ORM now short-term caches the "compiled" form of
    insert() and update() constructs when flushing lists of 
    objects of all the same class, thereby avoiding redundant
    compilation per individual INSERT/UPDATE within an 
    individual flush() call.
    
  - internal getattr(), setattr(), getcommitted() methods
    on ColumnProperty, CompositeProperty, RelationshipProperty
    have been underscored (i.e. are private), signature has 
    changed.
    
- engines
  - The C extension now also works with DBAPIs which use custom
    sequences as row (and not only tuples). [ticket:1757]

- sql
  - Restored some bind-labeling logic from 0.5 which ensures
    that tables with column names that overlap another column
    of the form "<tablename>_<columnname>" won't produce 
    errors if column._label is used as a bind name during
    an UPDATE.  Test coverage which wasn't present in 0.5
    has been added.  [ticket:1755]

  - somejoin.select(fold_equivalents=True) is no longer 
    deprecated, and will eventually be rolled into a more 
    comprehensive version of the feature for [ticket:1729].
    
  - the Numeric type raises an *enormous* warning when expected
    to convert floats to Decimal from a DBAPI that returns floats.
    This includes SQLite, Sybase, MS-SQL. [ticket:1759]

  - Fixed an error in expression typing which caused an endless
    loop for expressions with two NULL types.
  
  - Fixed bug in execution_options() feature whereby the existing
    Transaction and other state information from the parent 
    connection would not be propagated to the sub-connection.

  - Added new 'compiled_cache' execution option.  A dictionary 
    where Compiled objects will be cached when the Connection
    compiles a clause expression into a dialect- and parameter- 
    specific Compiled object.  It is the user's responsibility to
    manage the size of this dictionary, which will have keys
    corresponding to the dialect, clause element, the column
    names within the VALUES or SET clause of an INSERT or UPDATE, 
    as well as the "batch" mode for an INSERT or UPDATE statement.
  
  - Added get_pk_constraint() to reflection.Inspector, similar
    to get_primary_keys() except returns a dict that includes the
    name of the constraint, for supported backends (PG so far).
    [ticket:1769]

  - Table.create() and Table.drop() no longer apply metadata-
    level create/drop events.  [ticket:1771]
    
- ext
  - the compiler extension now allows @compiles decorators
    on base classes that extend to child classes, @compiles
    decorators on child classes that aren't broken by a 
    @compiles decorator on the base class.
   
  - Declarative will raise an informative error message
    if a non-mapped class attribute is referenced in the
    string-based relationship() arguments.

  - Further reworked the "mixin" logic in declarative to 
    additionally allow __mapper_args__ as a @classproperty
    on a mixin, such as to dynamically assign polymorphic_identity.

- postgresql
  - Postgresql now reflects sequence names associated with 
    SERIAL columns correctly, after the name of of the sequence
    has been changed.  Thanks to Kumar McMillan for the patch.
    [ticket:1071]
    
  - Repaired missing import in psycopg2._PGNumeric type when 
    unknown numeric is received.

  - psycopg2/pg8000 dialects now aware of REAL[], FLOAT[], 
    DOUBLE_PRECISION[], NUMERIC[] return types without
    raising an exception.

  - Postgresql reflects the name of primary key constraints,
    if one exists.  [ticket:1769]
        
- oracle
  - Now using cx_oracle output converters so that the
    DBAPI returns natively the kinds of values we prefer:
    - NUMBER values with positive precision + scale convert
      to cx_oracle.STRING and then to Decimal.   This 
      allows perfect precision for the Numeric type when
      using cx_oracle.  [ticket:1759]
    - STRING/FIXED_CHAR now convert to unicode natively.
      SQLAlchemy's String types then don't need to 
      apply any kind of conversions.

- firebird
   - The functionality of result.rowcount can be disabled on a
     per-engine basis by setting 'enable_rowcount=False' 
     on create_engine().  Normally, cursor.rowcount is called
     after any UPDATE or DELETE statement unconditionally,
     because the cursor is then closed and Firebird requires
     an open cursor in order to get a rowcount.  This 
     call is slightly expensive however so it can be disabled.
     To re-enable on a per-execution basis, the 
     'enable_rowcount=True' execution option may be used.
     
- examples
  - Updated attribute_shard.py example to use a more robust
    method of searching a Query for binary expressions which
    compare columns against literal values.
    
0.6beta3
========

- orm
  - Major feature: Added new "subquery" loading capability to 
    relationship().   This is an eager loading option which
    generates a second SELECT for each collection represented
    in a query, across all parents at once.  The query 
    re-issues the original end-user query wrapped in a subquery,
    applies joins out to the target collection, and loads 
    all those collections fully in one result, similar to 
    "joined" eager loading but using all inner joins and not 
    re-fetching full parent rows repeatedly (as most DBAPIs seem 
    to do, even if columns are skipped).   Subquery loading is 
    available at mapper config level using "lazy='subquery'" and 
    at the query options level using "subqueryload(props..)", 
    "subqueryload_all(props...)".  [ticket:1675]

  - To accomodate the fact that there are now two kinds of eager 
    loading available, the new names for eagerload() and 
    eagerload_all() are joinedload() and joinedload_all().  The 
    old names will remain as synonyms for the foreseeable future.
    
  - The "lazy" flag on the relationship() function now accepts 
    a string argument for all kinds of loading: "select", "joined",
    "subquery", "noload" and "dynamic", where the default is now
    "select".  The old values of True/
    False/None still retain their usual meanings and will remain
    as synonyms for the foreseeable future.

  - Added with_hint() method to Query() construct.  This calls
    directly down to select().with_hint() and also accepts
    entities as well as tables and aliases.  See with_hint() in the 
    SQL section below. [ticket:921]
    
  - Fixed bug in Query whereby calling q.join(prop).from_self(...).
    join(prop) would fail to render the second join outside the
    subquery, when joining on the same criterion as was on the 
    inside.

  - Fixed bug in Query whereby the usage of aliased() constructs
    would fail if the underlying table (but not the actual alias) 
    were referenced inside the subquery generated by 
    q.from_self() or q.select_from().
    
  - Fixed bug which affected all eagerload() and similar options 
    such that "remote" eager loads, i.e. eagerloads off of a lazy
    load such as query(A).options(eagerload(A.b, B.c))
    wouldn't eagerload anything, but using eagerload("b.c") would
    work fine.

  - Query gains an add_columns(*columns) method which is a multi-
    version of add_column(col).  add_column(col) is future 
    deprecated.

  - Query.join() will detect if the end result will be 
    "FROM A JOIN A", and will raise an error if so.

  - Query.join(Cls.propname, from_joinpoint=True) will check more
    carefully that "Cls" is compatible with the current joinpoint,
    and act the same way as Query.join("propname", from_joinpoint=True)
    in that regard.
    
- sql
   - Added with_hint() method to select() construct.  Specify
     a table/alias, hint text, and optional dialect name, and
     "hints" will be rendered in the appropriate place in the 
     statement.  Works for Oracle, Sybase, MySQL.  [ticket:921]
     
   - Fixed bug introduced in 0.6beta2 where column labels would 
     render inside of column expressions already assigned a label.
     [ticket:1747]

- postgresql
   - The psycopg2 dialect will log NOTICE messages via the
     "sqlalchemy.dialects.postgresql" logger name. 
     [ticket:877]

   - the TIME and TIMESTAMP types are now availble from the
     postgresql dialect directly, which add the PG-specific
     argument 'precision' to both.   'precision' and 
     'timezone' are correctly reflected for both TIME and 
     TIMEZONE types. [ticket:997]

- mysql
   - No longer guessing that TINYINT(1) should be BOOLEAN
     when reflecting - TINYINT(1) is returned.  Use Boolean/
     BOOLEAN in table definition to get boolean conversion
     behavior.  [ticket:1752]
     
- oracle
   - The Oracle dialect will issue VARCHAR type definitions
     using character counts, i.e. VARCHAR2(50 CHAR), so that
     the column is sized in terms of characters and not bytes.
     Column reflection of character types will also use
     ALL_TAB_COLUMNS.CHAR_LENGTH instead of 
     ALL_TAB_COLUMNS.DATA_LENGTH.  Both of these behaviors take
     effect when the server version is 9 or higher - for 
     version 8, the old behaviors are used.  [ticket:1744]

- declarative
   - Using a mixin won't break if the mixin implements an 
     unpredictable __getattribute__(), i.e. Zope interfaces.
     [ticket:1746]

   - Using @classdecorator and similar on mixins to define 
     __tablename__, __table_args__, etc. now works if
     the method references attributes on the ultimate 
     subclass. [ticket:1749]
    
   - relationships and columns with foreign keys aren't 
     allowed on declarative mixins, sorry.  [ticket:1751]

- ext
    - The sqlalchemy.orm.shard module now becomes an extension,
      sqlalchemy.ext.horizontal_shard.   The old import 
      works with a deprecation warning.
      
0.6beta2
========

- py3k
  - Improved the installation/test setup regarding Python 3,
    now that Distribute runs on Py3k.   distribute_setup.py
    is now included.  See README.py3k for Python 3 installation/
    testing instructions.
    
- orm
  - The official name for the relation() function is now
    relationship(), to eliminate confusion over the relational
    algebra term.  relation() however will remain available 
    in equal capacity for the foreseeable future.  [ticket:1740]

  - Added "version_id_generator" argument to Mapper, this is a
    callable that, given the current value of the "version_id_col",
    returns the next version number.  Can be used for alternate
    versioning schemes such as uuid, timestamps.  [ticket:1692]
  
  - added "lockmode" kw argument to Session.refresh(), will
    pass through the string value to Query the same as  
    in with_lockmode(), will also do version check for a 
    version_id_col-enabled mapping.

  - Fixed bug whereby calling query(A).join(A.bs).add_entity(B)
    in a joined inheritance scenario would double-add B as a 
    target and produce an invalid query.  [ticket:1188]

  - Fixed bug in session.rollback() which involved not removing
    formerly "pending" objects from the session before
    re-integrating "deleted" objects, typically occured with
    natural primary keys. If there was a primary key conflict
    between them, the attach of the deleted would fail
    internally. The formerly "pending" objects are now expunged
    first. [ticket:1674]

  - Removed a lot of logging that nobody really cares about,
    logging that remains will respond to live changes in the
    log level.  No significant overhead is added.  [ticket:1719]

  - Fixed bug in session.merge() which prevented dict-like
    collections from merging.
    
  - session.merge() works with relations that specifically
    don't include "merge" in their cascade options - the target
    is ignored completely.
    
  - session.merge() will not expire existing scalar attributes
    on an existing target if the target has a value for that
    attribute, even if the incoming merged doesn't have
    a value for the attribute.  This prevents unnecessary loads
    on existing items.  Will still mark the attr as expired
    if the destination doesn't have the attr, though, which
    fulfills some contracts of deferred cols.  [ticket:1681]

  - The "allow_null_pks" flag is now called "allow_partial_pks",
    defaults to True, acts like it did in 0.5 again.  Except,
    it also is implemented within merge() such that a SELECT
    won't be issued for an incoming instance with partially
    NULL primary key if the flag is False.  [ticket:1680]
  
  - Fixed bug in 0.6-reworked "many-to-one" optimizations
    such that a many-to-one that is against a non-primary key
    column on the remote table (i.e. foreign key against a 
    UNIQUE column) will pull the "old" value in from the
    database during a change, since if it's in the session
    we will need it for proper history/backref accounting,
    and we can't pull from the local identity map on a 
    non-primary key column. [ticket:1737]
    
  - fixed internal error which would occur if calling has()
    or similar complex expression on a single-table inheritance
    relation(). [ticket:1731]
    
  - query.one() no longer applies LIMIT to the query, this to
    ensure that it fully counts all object identities present
    in the result, even in the case where joins may conceal
    multiple identities for two or more rows.  As a bonus,
    one() can now also be called with a query that issued
    from_statement() to start with since it no longer modifies
    the query.  [ticket:1688]

  - query.get() now returns None if queried for an identifier
    that is present in the identity map with a different class 
    than the one requested, i.e. when using polymorphic loading.  
    [ticket:1727]
    
  - A major fix in query.join(), when the "on" clause is an
    attribute of an aliased() construct, but there is already
    an existing join made out to a compatible target, query properly
    joins to the right aliased() construct instead of sticking
    onto the right side of the existing join.  [ticket:1706]
    
  - Slight improvement to the fix for [ticket:1362] to not issue 
    needless updates of the primary key column during a so-called
    "row switch" operation, i.e. add + delete of two objects
    with the same PK.

  - Now uses sqlalchemy.orm.exc.DetachedInstanceError when an 
    attribute load or refresh action fails due to object
    being detached from any Session.   UnboundExecutionError
    is specific to engines bound to sessions and statements.
    
  - Query called in the context of an expression will render
    disambiguating labels in all cases.    Note that this does
    not apply to the existing .statement and .subquery()
    accessor/method, which still honors the .with_labels()
    setting that defaults to False.  
     
  - Query.union() retains disambiguating labels within the
    returned statement, thus avoiding various SQL composition
    errors which can result from column name conflicts.
    [ticket:1676]

  - Fixed bug in attribute history that inadvertently invoked
    __eq__ on mapped instances.

  - Some internal streamlining of object loading grants a 
    small speedup for large results, estimates are around 
    10-15%.   Gave the "state" internals a good solid 
    cleanup with less complexity, datamembers, 
    method calls, blank dictionary creates.

  - Documentation clarification for query.delete()
    [ticket:1689]

  - Fixed cascade bug in many-to-one relation() when attribute
    was set to None, introduced in r6711 (cascade deleted
    items into session during add()).

  - Calling query.order_by() or query.distinct() before calling
    query.select_from(), query.with_polymorphic(), or
    query.from_statement() raises an exception now instead of 
    silently dropping those criterion. [ticket:1736]
    
  - query.scalar() now raises an exception if more than one 
    row is returned.  All other behavior remains the same.
    [ticket:1735]

  - Fixed bug which caused "row switch" logic, that is an 
    INSERT and DELETE replaced by an UPDATE, to fail when 
    version_id_col was in use. [ticket:1692]
    
- sql
  - join() will now simulate a NATURAL JOIN by default.  Meaning,
    if the left side is a join, it will attempt to join the right
    side to the rightmost side of the left first, and not raise
    any exceptions about ambiguous join conditions if successful
    even if there are further join targets across the rest of
    the left.  [ticket:1714]
    
  - The most common result processors conversion function were
    moved to the new "processors" module.  Dialect authors are
    encouraged to use those functions whenever they correspond
    to their needs instead of implementing custom ones.

  - SchemaType and subclasses Boolean, Enum are now serializable,
    including their ddl listener and other event callables.
    [ticket:1694] [ticket:1698]

  - Some platforms will now interpret certain literal values 
    as non-bind parameters, rendered literally into the SQL
    statement.   This to support strict SQL-92 rules that are 
    enforced by some platforms including MS-SQL and Sybase.
    In this model, bind parameters aren't allowed in the
    columns clause of a SELECT, nor are certain ambiguous
    expressions like "?=?".  When this mode is enabled, the base
    compiler will render the binds as inline literals, but only across
    strings and numeric values.  Other types such as dates
    will raise an error, unless the dialect subclass defines
    a literal rendering function for those.  The bind parameter
    must have an embedded literal value already or an error
    is raised (i.e. won't work with straight bindparam('x')).
    Dialects can also expand upon the areas where binds are not 
    accepted, such as within argument lists of functions 
    (which don't work on MS-SQL when native SQL binding is used).
    
  - Added "unicode_errors" parameter to String, Unicode, etc.
    Behaves like the 'errors' keyword argument to
    the standard library's string.decode() functions.   This flag
    requires that `convert_unicode` is set to `"force"` - otherwise,
    SQLAlchemy is not guaranteed to handle the task of unicode
    conversion.   Note that this flag adds significant performance
    overhead to row-fetching operations for backends that already
    return unicode objects natively (which most DBAPIs do).  This
    flag should only be used as an absolute last resort for reading
    strings from a column with varied or corrupted encodings,
    which only applies to databases that accept invalid encodings 
    in the first place (i.e. MySQL. *not* PG, Sqlite, etc.)

  - Added math negation operator support, -x.
  
  - FunctionElement subclasses are now directly executable the
    same way any func.foo() construct is, with automatic 
    SELECT being applied when passed to execute().
    
  - The "type" and "bind" keyword arguments of a func.foo() 
    construct are now local to "func." constructs and are 
    not part of the FunctionElement base class, allowing 
    a "type" to be handled in a custom constructor or 
    class-level variable.
    
  - Restored the keys() method to ResultProxy.
  
  - The type/expression system now does a more complete job
    of determining the return type from an expression
    as well as the adaptation of the Python operator into 
    a SQL operator, based on the full left/right/operator
    of the given expression.  In particular
    the date/time/interval system created for Postgresql
    EXTRACT in [ticket:1647] has now been generalized into
    the type system.   The previous behavior which often
    occured of an expression "column + literal" forcing
    the type of "literal" to be the same as that of "column"
    will now usually not occur - the type of 
    "literal" is first derived from the Python type of the 
    literal, assuming standard native Python types + date 
    types, before falling back to that of the known type
    on the other side of the expression.  If the 
    "fallback" type is compatible (i.e. CHAR from String),
    the literal side will use that.  TypeDecorator
    types override this by default to coerce the "literal"
    side unconditionally, which can be changed by implementing
    the coerce_compared_value() method. Also part of 
    [ticket:1683].

  - Made sqlalchemy.sql.expressions.Executable part of public 
    API, used for any expression construct that can be sent to
    execute().  FunctionElement now inherits Executable so that
    it gains execution_options(), which are also propagated
    to the select() that's generated within execute().
    Executable in turn subclasses _Generative which marks
    any ClauseElement that supports the @_generative
    decorator - these may also become "public" for the benefit
    of the compiler extension at some point.

  - A change to the solution for [ticket:1579] - an end-user
    defined bind parameter name that directly conflicts with 
    a column-named bind generated directly from the SET or
    VALUES clause of an update/insert generates a compile error.
    This reduces call counts and eliminates some cases where
    undesirable name conflicts could still occur.

  - Column() requires a type if it has no foreign keys (this is 
    not new).  An error is now raised if a Column() has no type
    and no foreign keys.  [ticket:1705]
    
  - the "scale" argument of the Numeric() type is honored when 
    coercing a returned floating point value into a string 
    on its way to Decimal - this allows accuracy to function
    on SQLite, MySQL.  [ticket:1717]

  - the copy() method of Column now copies over uninitialized
    "on table attach" events.  Helps with the new declarative
    "mixin" capability.
    
- engines
  - Added an optional C extension to speed up the sql layer by
    reimplementing RowProxy and the most common result processors.
    The actual speedups will depend heavily on your DBAPI and
    the mix of datatypes used in your tables, and can vary from
    a 30% improvement to more than 200%.  It also provides a modest
    (~15-20%) indirect improvement to ORM speed for large queries.
    Note that it is *not* built/installed by default.
    See README for installation instructions.

  - the execution sequence pulls all rowcount/last inserted ID
    info from the cursor before commit() is called on the 
    DBAPI connection in an "autocommit" scenario.  This helps 
    mxodbc with rowcount and is probably a good idea overall.
    
  - Opened up logging a bit such that isEnabledFor() is called 
    more often, so that changes to the log level for engine/pool
    will be reflected on next connect.   This adds a small 
    amount of method call overhead.  It's negligible and will make
    life a lot easier for all those situations when logging 
    just happens to be configured after create_engine() is called.
    [ticket:1719]
    
  - The assert_unicode flag is deprecated.  SQLAlchemy will raise
    a warning in all cases where it is asked to encode a non-unicode
    Python string, as well as when a Unicode or UnicodeType type
    is explicitly passed a bytestring.  The String type will do nothing 
    for DBAPIs that already accept Python unicode objects.

  - Bind parameters are sent as a tuple instead of a list. Some
    backend drivers will not accept bind parameters as a list.

  - threadlocal engine wasn't properly closing the connection
    upon close() - fixed that.

  - Transaction object doesn't rollback or commit if it isn't 
    "active", allows more accurate nesting of begin/rollback/commit.

  - Python unicode objects as binds result in the Unicode type, 
    not string, thus eliminating a certain class of unicode errors
    on drivers that don't support unicode binds.

  - Added "logging_name" argument to create_engine(), Pool() constructor
    as well as "pool_logging_name" argument to create_engine() which
    filters down to that of Pool.   Issues the given string name
    within the "name" field of logging messages instead of the default
    hex identifier string.  [ticket:1555]
    
  - The visit_pool() method of Dialect is removed, and replaced with
    on_connect().  This method returns a callable which receives
    the raw DBAPI connection after each one is created.   The callable
    is assembled into a first_connect/connect pool listener by the 
    connection strategy if non-None.   Provides a simpler interface 
    for dialects.
    
  - StaticPool now initializes, disposes and recreates without 
    opening a new connection - the connection is only opened when 
    first requested. dispose() also works on AssertionPool now.
    [ticket:1728]
    
- metadata
  - Added the ability to strip schema information when using
    "tometadata" by passing "schema=None" as an argument. If schema
    is not specified then the table's schema is retained.
    [ticket: 1673]

- declarative
  - DeclarativeMeta exclusively uses cls.__dict__ (not dict_) 
    as the source of class information; _as_declarative exclusively 
    uses the  dict_ passed to it as the source of class information 
    (which when using DeclarativeMeta is cls.__dict__).  This should 
    in theory make it easier for custom metaclasses to modify
    the state passed into _as_declarative.

  - declarative now accepts mixin classes directly, as a means
    to provide common functional and column-based elements on
    all subclasses, as well as a means to propagate a fixed
    set of __table_args__ or __mapper_args__ to subclasses.  
    For custom combinations of __table_args__/__mapper_args__ from
    an inherited mixin to local, descriptors can now be used.
    New details are all up in the Declarative documentation.
    Thanks to Chris Withers for putting up with my strife 
    on this. [ticket:1707]
    
  - the __mapper_args__ dict is copied when propagating to a subclass,
    and is taken straight off the class __dict__ to avoid any
    propagation from the parent.  mapper inheritance already
    propagates the things you want from the parent mapper.
    [ticket:1393]

  - An exception is raised when a single-table subclass specifies
    a column that is already present on the base class.
    [ticket:1732]
    
- mysql
  - Fixed reflection bug whereby when COLLATE was present, 
    nullable flag and server defaults would not be reflected.
    [ticket:1655]

  - Fixed reflection of TINYINT(1) "boolean" columns defined with
    integer flags like UNSIGNED.

  - Further fixes for the mysql-connector dialect.  [ticket:1668]
  
  - Composite PK table on InnoDB where the "autoincrement" column
    isn't first will emit an explicit "KEY" phrase within 
    CREATE TABLE thereby avoiding errors, [ticket:1496]

  - Added reflection/create table support for a wide range
    of MySQL keywords.  [ticket:1634]
  
  - Fixed import error which could occur reflecting tables on
    a Windows host [ticket:1580]
    
- mssql
  - Re-established support for the pymssql dialect.

  - Various fixes for implicit returning, reflection,
    etc. - the MS-SQL dialects aren't quite complete
    in 0.6 yet (but are close)
  
  - Added basic support for mxODBC [ticket:1710].
  
  - Removed the text_as_varchar option.

- oracle
   - "out" parameters require a type that is supported by
     cx_oracle.  An error will be raised if no cx_oracle
     type can be found.

   - Oracle 'DATE' now does not perform any result processing,
     as the DATE type in Oracle stores full date+time objects,
     that's what you'll get.  Note that the generic types.Date
     type *will* still call value.date() on incoming values, 
     however.  When reflecting a table, the reflected type
     will be 'DATE'.

   - Added preliminary support for Oracle's WITH_UNICODE
     mode.  At the very least this establishes initial
     support for cx_Oracle with Python 3.  When WITH_UNICODE
     mode is used in Python 2.xx, a large and scary warning
     is emitted asking that the user seriously consider
     the usage of this difficult mode of operation.
     [ticket:1670]
  
   - The except_() method now renders as MINUS on Oracle,
     which is more or less equivalent on that platform.
     [ticket:1712]
   
   - Added support for rendering and reflecting 
     TIMESTAMP WITH TIME ZONE, i.e. TIMESTAMP(timezone=True).
     [ticket:651]
     
   - Oracle INTERVAL type can now be reflected.
     
- sqlite
   - Added "native_datetime=True" flag to create_engine().
     This will cause the DATE and TIMESTAMP types to skip 
     all bind parameter and result row processing, under 
     the assumption that PARSE_DECLTYPES has been enabled 
     on the connection.  Note that this is not entirely
     compatible with the "func.current_date()", which 
     will be returned as a string. [ticket:1685]

- sybase
   - Implemented a preliminary working dialect for Sybase,
     with sub-implementations for Python-Sybase as well
     as Pyodbc.  Handles table
     creates/drops and basic round trip functionality.
     Does not yet include reflection or comprehensive
     support of unicode/special expressions/etc.
     
- examples
   - Changed the beaker cache example a bit to have a separate
     RelationCache option for lazyload caching.  This object
     does a lookup among any number of potential attributes
     more efficiently by grouping several into a common structure.
     Both FromCache and RelationCache are simpler individually.

- documentation
   - Major cleanup work in the docs to link class, function, and
     method names into the API docs. [ticket:1700/1702/1703]

0.6beta1
========
- Major Release
  - For the full set of feature descriptions, see
    http://www.sqlalchemy.org/trac/wiki/06Migration .
    This document is a work in progress.

  - All bug fixes and feature enhancements from the most
    recent 0.5 version and below are also included within 0.6.

  - Platforms targeted now include Python 2.4/2.5/2.6, Python
    3.1, Jython2.5.
    
- orm
  - Changes to query.update() and query.delete():
      - the 'expire' option on query.update() has been renamed to
        'fetch', thus matching that of query.delete().  
        'expire' is deprecated and issues a warning.

      - query.update() and query.delete() both default to
        'evaluate' for the synchronize strategy.

      - the 'synchronize' strategy for update() and delete()
        raises an error on failure. There is no implicit fallback
        onto "fetch". Failure of evaluation is based on the
        structure of criteria, so success/failure is deterministic
        based on code structure.

  - Enhancements on many-to-one relations:
      - many-to-one relations now fire off a lazyload in fewer
        cases, including in most cases will not fetch the "old"
        value when a new one is replaced.

      - many-to-one relation to a joined-table subclass now uses
        get() for a simple load (known as the "use_get"
        condition), i.e. Related->Sub(Base), without the need to
        redefine the primaryjoin condition in terms of the base
        table. [ticket:1186]

      - specifying a foreign key with a declarative column, i.e.
        ForeignKey(MyRelatedClass.id) doesn't break the "use_get"
        condition from taking place [ticket:1492]

      - relation(), eagerload(), and eagerload_all() now feature
        an option called "innerjoin". Specify `True` or `False` to
        control whether an eager join is constructed as an INNER
        or OUTER join. Default is `False` as always. The mapper
        options will override whichever setting is specified on
        relation(). Should generally be set for many-to-one, not
        nullable foreign key relations to allow improved join
        performance. [ticket:1544]

      - the behavior of eagerloading such that the main query is
        wrapped in a subquery when LIMIT/OFFSET are present now
        makes an exception for the case when all eager loads are
        many-to-one joins. In those cases, the eager joins are
        against the parent table directly along with the
        limit/offset without the extra overhead of a subquery,
        since a many-to-one join does not add rows to the result.

  - Enhancements / Changes on Session.merge():
     - the "dont_load=True" flag on Session.merge() is deprecated
       and is now "load=False".
    
     - Session.merge() is performance optimized, using half the
       call counts for "load=False" mode compared to 0.5 and
       significantly fewer SQL queries in the case of collections
       for "load=True" mode.

     - merge() will not issue a needless merge of attributes if the
       given instance is the same instance which is already present.
       
     - merge() now also merges the "options" associated with a given
       state, i.e. those passed through query.options() which follow
       along with an instance, such as options to eagerly- or
       lazyily- load various attributes.   This is essential for
       the construction of highly integrated caching schemes.  This
       is a subtle behavioral change vs. 0.5.
       
     - A bug was fixed regarding the serialization of the "loader
       path" present on an instance's state, which is also necessary
       when combining the usage of merge() with serialized state
       and associated options that should be preserved.  
       
     - The all new merge() is showcased in a new comprehensive 
       example of how to integrate Beaker with SQLAlchemy.  See
       the notes in the "examples" note below.
  
  - Primary key values can now be changed on a joined-table inheritance
    object, and ON UPDATE CASCADE will be taken into account when
    the flush happens.  Set the new "passive_updates" flag to False
    on mapper() when using SQLite or MySQL/MyISAM. [ticket:1362]
    
  - flush() now detects when a primary key column was updated by
    an ON UPDATE CASCADE operation from another primary key, and
    can then locate the row for a subsequent UPDATE on the new PK
    value.  This occurs when a relation() is there to establish
    the relationship as well as passive_updates=True.  [ticket:1671]
    
  - the "save-update" cascade will now cascade the pending *removed*
    values from a scalar or collection attribute into the new session 
    during an add() operation.  This so that the flush() operation
    will also delete or modify rows of those disconnected items.
    
  - Using a "dynamic" loader with a "secondary" table now produces
    a query where the "secondary" table is *not* aliased.  This
    allows the secondary Table object to be used in the "order_by"
    attribute of the relation(), and also allows it to be used
    in filter criterion against the dynamic relation.
    [ticket:1531]

  - relation() with uselist=False will emit a warning when 
    an eager or lazy load locates more than one valid value for 
    the row.  This may be due to primaryjoin/secondaryjoin 
    conditions which aren't appropriate for an eager LEFT OUTER 
    JOIN or for other conditions.  [ticket:1643]
    
  - an explicit check occurs when a synonym() is used with 
    map_column=True, when a ColumnProperty (deferred or otherwise)
    exists separately in the properties dictionary sent to mapper
    with the same keyname.   Instead of silently replacing 
    the existing property (and possible options on that property), 
    an error is raised.  [ticket:1633]
    
  - a "dynamic" loader sets up its query criterion at construction
    time so that the actual query is returned from non-cloning
    accessors like "statement".
    
  - the "named tuple" objects returned when iterating a
    Query() are now pickleable.

  - mapping to a select() construct now requires that you 
    make an alias() out of it distinctly.   This to eliminate
    confusion over such issues as [ticket:1542]
    
  - query.join() has been reworked to provide more consistent 
    behavior and more flexibility (includes [ticket:1537])

  - query.select_from() accepts multiple clauses to produce 
    multiple comma separated entries within the FROM clause.
    Useful when selecting from multiple-homed join() clauses.

  - query.select_from() also accepts mapped classes, aliased()
    constructs, and mappers as arguments.  In particular this
    helps when querying from multiple joined-table classes to ensure
    the full join gets rendered.

  - query.get() can be used with a mapping to an outer join
    where one or more of the primary key values are None.
    [ticket:1135]
    
  - query.from_self(), query.union(), others which do a 
    "SELECT * from (SELECT...)" type of nesting will do
    a better job translating column expressions within the subquery
    to the columns clause of the outer query.  This is
    potentially backwards incompatible with 0.5, in that this 
    may break queries with literal expressions that do not have labels
    applied (i.e. literal('foo'), etc.)
    [ticket:1568]
  
  - relation primaryjoin and secondaryjoin now check that they
    are column-expressions, not just clause elements.  this prohibits
    things like FROM expressions being placed there directly.
    [ticket:1622]
    
  - `expression.null()` is fully understood the same way
    None is when comparing an object/collection-referencing
    attribute within query.filter(), filter_by(), etc.
    [ticket:1415]

  - added "make_transient()" helper function which transforms a
    persistent/ detached instance into a transient one (i.e.
    deletes the instance_key and removes from any session.)
    [ticket:1052]

  - the allow_null_pks flag on mapper() is deprecated, and 
    the feature is turned "on" by default.  This means that 
    a row which has a non-null value for any of its primary key
    columns will be considered an identity.  The need for this
    scenario typically only occurs when mapping to an outer join.
    [ticket:1339]

   - the mechanics of "backref" have been fully merged into the
     finer grained "back_populates" system, and take place entirely
     within the _generate_backref() method of RelationProperty.  This
     makes the initialization procedure of RelationProperty
     simpler and allows easier propagation of settings (such as from
     subclasses of RelationProperty) into the reverse reference. 
     The internal BackRef() is gone and backref() returns a plain 
     tuple that is understood by RelationProperty.
     
   - The version_id_col feature on mapper() will raise a warning when
     used with dialects that don't support "rowcount" adequately.
     [ticket:1569]

   - added "execution_options()" to Query, to so options can be
     passed to the resulting statement. Currently only
     Select-statements have these options, and the only option
     used is "stream_results", and the only dialect which knows
     "stream_results" is psycopg2. 
     
   - Query.yield_per() will set the "stream_results" statement
     option automatically.
     
   - Deprecated or removed:
      * 'allow_null_pks' flag on mapper() is deprecated.  It does
        nothing now and the setting is "on" in all cases.
      * 'transactional' flag on sessionmaker() and others is
        removed. Use 'autocommit=True' to indicate 'transactional=False'.
      * 'polymorphic_fetch' argument on mapper() is removed.
        Loading can be controlled using the 'with_polymorphic'
        option.
      * 'select_table' argument on mapper() is removed.  Use 
        'with_polymorphic=("*", <some selectable>)' for this 
        functionality.
      * 'proxy' argument on synonym() is removed.  This flag
        did nothing throughout 0.5, as the "proxy generation"
        behavior is now automatic.
      * Passing a single list of elements to eagerload(),
        eagerload_all(), contains_eager(), lazyload(),
        defer(), and undefer() instead of multiple positional 
        *args is deprecated.
      * Passing a single list of elements to query.order_by(),
        query.group_by(), query.join(), or query.outerjoin()
        instead of multiple positional *args is deprecated.
      * query.iterate_instances() is removed.  Use query.instances().
      * Query.query_from_parent() is removed.  Use the
        sqlalchemy.orm.with_parent() function to produce a 
        "parent" clause, or alternatively query.with_parent().
      * query._from_self() is removed, use query.from_self()
        instead.
      * the "comparator" argument to composite() is removed.
        Use "comparator_factory".
      * RelationProperty._get_join() is removed.
      * the 'echo_uow' flag on Session is removed.  Use
        logging on the "sqlalchemy.orm.unitofwork" name.
      * session.clear() is removed.  use session.expunge_all().
      * session.save(), session.update(), session.save_or_update()
        are removed.  Use session.add() and session.add_all().
      * the "objects" flag on session.flush() remains deprecated.
      * the "dont_load=True" flag on session.merge() is deprecated
        in favor of "load=False".
      * ScopedSession.mapper remains deprecated.  See the 
        usage recipe at 
        http://www.sqlalchemy.org/trac/wiki/UsageRecipes/SessionAwareMapper
      * passing an InstanceState (internal SQLAlchemy state object) to
        attributes.init_collection() or attributes.get_history() is 
        deprecated.  These functions are public API and normally
        expect a regular mapped object instance.
      * the 'engine' parameter to declarative_base() is removed.
        Use the 'bind' keyword argument.
        
- sql
  
    - the "autocommit" flag on select() and text() as well
      as select().autocommit() are deprecated - now call
      .execution_options(autocommit=True) on either of those
      constructs, also available directly on Connection and orm.Query.

    - the autoincrement flag on column now indicates the column
      which should be linked to cursor.lastrowid, if that method
      is used.  See the API docs for details.
    
    - an executemany() now requires that all bound parameter
      sets require that all keys are present which are 
      present in the first bound parameter set.  The structure
      and behavior of an insert/update statement is very much
      determined by the first parameter set, including which
      defaults are going to fire off, and a minimum of 
      guesswork is performed with all the rest so that performance
      is not impacted.  For this reason defaults would otherwise 
      silently "fail" for missing parameters, so this is now guarded 
      against. [ticket:1566]
      
    - returning() support is native to insert(), update(),
      delete(). Implementations of varying levels of
      functionality exist for Postgresql, Firebird, MSSQL and
      Oracle. returning() can be called explicitly with column
      expressions which are then returned in the resultset,
      usually via fetchone() or first().

      insert() constructs will also use RETURNING implicitly to
      get newly generated primary key values, if the database
      version in use supports it (a version number check is
      performed). This occurs if no end-user returning() was
      specified.
    
    - union(), intersect(), except() and other "compound" types
      of statements have more consistent behavior w.r.t. 
      parenthesizing.   Each compound element embedded within 
      another will now be grouped with parenthesis - previously,
      the first compound element in the list would not be grouped,
      as SQLite doesn't like a statement to start with 
      parenthesis.   However, Postgresql in particular has
      precedence rules regarding INTERSECT, and it is 
      more consistent for parenthesis to be applied equally
      to all sub-elements.   So now, the workaround for SQLite
      is also what the workaround for PG was previously -
      when nesting compound elements, the first one usually needs
      ".alias().select()" called on it to wrap it inside
      of a subquery.  [ticket:1665]
      
    - insert() and update() constructs can now embed bindparam()
      objects using names that match the keys of columns.  These
      bind parameters will circumvent the usual route to those 
      keys showing up in the VALUES or SET clause of the generated
      SQL. [ticket:1579]
      
    - the Binary type now returns data as a Python string
      (or a "bytes" type in Python 3), instead of the built-
      in "buffer" type.  This allows symmetric round trips
      of binary data. [ticket:1524]
    
    - Added a tuple_() construct, allows sets of expressions
      to be compared to another set, typically with IN against
      composite primary keys or similar.  Also accepts an 
      IN with multiple columns.   The "scalar select can
      have only one column" error message is removed - will
      rely upon the database to report problems with 
      col mismatch.
        
    - User-defined "default" and "onupdate" callables which 
      accept a context should now call upon 
      "context.current_parameters" to get at the dictionary
      of bind parameters currently being processed.  This
      dict is available in the same way regardless of 
      single-execute or executemany-style statement execution.

    - multi-part schema names, i.e. with dots such as 
      "dbo.master", are now rendered in select() labels
      with underscores for dots, i.e. "dbo_master_table_column".
      This is a "friendly" label that behaves better
      in result sets. [ticket:1428]
    
    - removed needless "counter" behavior with select()
      labelnames that match a column name in the table,
      i.e. generates "tablename_id" for "id", instead of
      "tablename_id_1" in an attempt to avoid naming 
      conflicts, when the table has a column actually 
      named "tablename_id" - this is because
      the labeling logic is always applied to all columns
      so a naming conflict will never occur.
    
    - calling expr.in_([]), i.e. with an empty list, emits a warning
      before issuing the usual "expr != expr" clause.  The
      "expr != expr" can be very expensive, and it's preferred
      that the user not issue in_() if the list is empty,
      instead simply not querying, or modifying the criterion
       as appropriate for more complex situations.
       [ticket:1628]

    - Added "execution_options()" to select()/text(), which set the
      default options for the Connection.  See the note in "engines".
       
    - Deprecated or removed:
        * "scalar" flag on select() is removed, use 
          select.as_scalar().
        * "shortname" attribute on bindparam() is removed.
        * postgres_returning, firebird_returning flags on 
          insert(), update(), delete() are deprecated, use
          the new returning() method.
        * fold_equivalents flag on join is deprecated (will remain
          until [ticket:1131] is implemented)
    
- engines
  - transaction isolation level may be specified with
    create_engine(... isolation_level="..."); available on
    postgresql and sqlite. [ticket:443]
    
  - Connection has execution_options(), generative method
    which accepts keywords that affect how the statement 
    is executed w.r.t. the DBAPI.   Currently supports 
    "stream_results", causes psycopg2 to use a server
    side cursor for that statement, as well as 
    "autocommit", which is the new location for the "autocommit"
    option from select() and text().   select() and
    text() also have .execution_options() as well as 
    ORM Query().
    
  - fixed the import for entrypoint-driven dialects to 
    not rely upon silly tb_info trick to determine import
    error status.  [ticket:1630]
    
  - added first() method to ResultProxy, returns first row and
    closes result set immediately.

  - RowProxy objects are now pickleable, i.e. the object returned
    by result.fetchone(), result.fetchall() etc.

  - RowProxy no longer has a close() method, as the row no longer
    maintains a reference to the parent.  Call close() on 
    the parent ResultProxy instead, or use autoclose.
    
  - ResultProxy internals have been overhauled to greatly reduce
    method call counts when fetching columns.  Can provide a large 
    speed improvement (up to more than 100%) when fetching large 
    result sets.  The improvement is larger when fetching columns 
    that have no type-level processing applied and when using 
    results as tuples (instead of as dictionaries).  Many 
    thanks to Elixir's Gaëtan de Menten for this dramatic 
    improvement !  [ticket:1586]

  - Databases which rely upon postfetch of "last inserted id"
    to get at a generated sequence value (i.e. MySQL, MS-SQL)
    now work correctly when there is a composite primary key
    where the "autoincrement" column is not the first primary
    key column in the table.

  - the last_inserted_ids() method has been renamed to the
    descriptor "inserted_primary_key".
    
  - setting echo=False on create_engine() now sets the loglevel
    to WARN instead of NOTSET.  This so that logging can be
    disabled for a particular engine even if logging
    for "sqlalchemy.engine" is enabled overall.  Note that the
    default setting of "echo" is `None`. [ticket:1554]
  
  - ConnectionProxy now has wrapper methods for all transaction
    lifecycle events, including begin(), rollback(), commit()
    begin_nested(), begin_prepared(), prepare(), release_savepoint(),
    etc.
    
  - Connection pool logging now uses both INFO and DEBUG
    log levels for logging.  INFO is for major events such
    as invalidated connections, DEBUG for all the acquire/return
    logging.  `echo_pool` can be False, None, True or "debug"
    the same way as `echo` works.
  
  - All pyodbc-dialects now support extra pyodbc-specific 
    kw arguments 'ansi', 'unicode_results', 'autocommit'.
    [ticket:1621]

  - the "threadlocal" engine has been rewritten and simplified 
    and now supports SAVEPOINT operations.
    
  - deprecated or removed
      * result.last_inserted_ids() is deprecated.  Use 
        result.inserted_primary_key
      * dialect.get_default_schema_name(connection) is now
        public via dialect.default_schema_name.
      * the "connection" argument from engine.transaction() and
        engine.run_callable() is removed - Connection itself
        now has those methods.   All four methods accept
        *args and **kwargs which are passed to the given callable, 
        as well as the operating connection.
        
- schema
    - the `__contains__()` method of `MetaData` now accepts
      strings or `Table` objects as arguments.  If given
      a `Table`, the argument is converted to `table.key` first,
      i.e. "[schemaname.]<tablename>" [ticket:1541]
      
    - deprecated MetaData.connect() and
      ThreadLocalMetaData.connect() have been removed - send
      the "bind" attribute to bind a metadata.

    - deprecated metadata.table_iterator() method removed (use
      sorted_tables)
    
    - deprecated PassiveDefault - use DefaultClause.
    
    - the "metadata" argument is removed from DefaultGenerator
      and subclasses, but remains locally present on Sequence,
      which is a standalone construct in DDL.

    - Removed public mutability from Index and Constraint
      objects:
        - ForeignKeyConstraint.append_element()
        - Index.append_column()
        - UniqueConstraint.append_column()
        - PrimaryKeyConstraint.add()
        - PrimaryKeyConstraint.remove()
      These should be constructed declaratively (i.e. in one
      construction).
    
    - The "start" and "increment" attributes on Sequence now
      generate "START WITH" and "INCREMENT BY" by default,
      on Oracle and Postgresql.  Firebird doesn't support
      these keywords right now.  [ticket:1545]
      
    - UniqueConstraint, Index, PrimaryKeyConstraint all accept
      lists of column names or column objects as arguments.

    - Other removed things:
        - Table.key (no idea what this was for)
        - Table.primary_key is not assignable - use
          table.append_constraint(PrimaryKeyConstraint(...))
        - Column.bind       (get via column.table.bind)
        - Column.metadata   (get via column.table.metadata)
        - Column.sequence   (use column.default)
        - ForeignKey(constraint=some_parent) (is now private _constraint)
        
    - The use_alter flag on ForeignKey is now a shortcut option
      for operations that can be hand-constructed using the
      DDL() event system. A side effect of this refactor is
      that ForeignKeyConstraint objects with use_alter=True
      will *not* be emitted on SQLite, which does not support
      ALTER for foreign keys.
    
    - ForeignKey and ForeignKeyConstraint objects now correctly
      copy() all their public keyword arguments.  [ticket:1605]
      
- Reflection/Inspection
    - Table reflection has been expanded and generalized into 
      a new API called "sqlalchemy.engine.reflection.Inspector".
      The Inspector object provides fine-grained information about
      a wide variety of schema information, with room for expansion,
      including table names, column names, view definitions, sequences,
      indexes, etc.  
    
    - Views are now reflectable as ordinary Table objects.  The same
      Table constructor is used, with the caveat that "effective" 
      primary and foreign key constraints aren't part of the reflection
      results; these have to be specified explicitly if desired.
    
    - The existing autoload=True system now uses Inspector underneath
      so that each dialect need only return "raw" data about tables
      and other objects - Inspector is the single place that information
      is compiled into Table objects so that consistency is at a maximum.
      
- DDL
    - the DDL system has been greatly expanded.  the DDL() class
      now extends the more generic DDLElement(), which forms the basis
      of many new constructs:
      
        - CreateTable()
        - DropTable()
        - AddConstraint()
        - DropConstraint()
        - CreateIndex()
        - DropIndex()
        - CreateSequence()
        - DropSequence()
        
       These support "on" and "execute-at()" just like plain DDL() 
       does.  User-defined DDLElement subclasses can be created and 
       linked to a compiler using the sqlalchemy.ext.compiler extension.

    - The signature of the "on" callable passed to DDL() and
      DDLElement() is revised as follows:
      
        "ddl" - the DDLElement object itself.
        "event" - the string event name.
        "target" - previously "schema_item", the Table or 
        MetaData object triggering the event.
        "connection" - the Connection object in use for the operation.
        **kw - keyword arguments.  In the case of MetaData before/after
          create/drop, the list of Table objects for which
          CREATE/DROP DDL is to be issued is passed as the kw
          argument "tables". This is necessary for metadata-level
          DDL that is dependent on the presence of specific tables.

      - the "schema_item" attribute of DDL has been renamed to 
        "target".

- dialect refactor
    - Dialect modules are now broken into database dialects
      plus DBAPI implementations. Connect URLs are now
      preferred to be specified using dialect+driver://...,
      i.e. "mysql+mysqldb://scott:tiger@localhost/test". See
      the 0.6 documentation for examples.

    - the setuptools entrypoint for external dialects is now 
      called "sqlalchemy.dialects".
      
    - the "owner" keyword argument is removed from Table. Use
      "schema" to represent any namespaces to be prepended to
      the table name.

    - server_version_info becomes a static attribute.

    - dialects receive an initialize() event on initial
      connection to determine connection properties.

    - dialects receive a visit_pool event have an opportunity
      to establish pool listeners.

    - cached TypeEngine classes are cached per-dialect class 
      instead of per-dialect.
    
    - new UserDefinedType should be used as a base class for
      new types, which preserves the 0.5 behavior of 
      get_col_spec().
      
    - The result_processor() method of all type classes now 
      accepts a second argument "coltype", which is the DBAPI
      type argument from cursor.description.  This argument
      can help some types decide on the most efficient processing
      of result values.
      
    - Deprecated Dialect.get_params() removed.

    - Dialect.get_rowcount() has been renamed to a descriptor
      "rowcount", and calls cursor.rowcount directly. Dialects
      which need to hardwire a rowcount in for certain calls
      should override the method to provide different behavior.

    - DefaultRunner and subclasses have been removed.  The job
      of this object has been simplified and moved into 
      ExecutionContext.  Dialects which support sequences should
      add a `fire_sequence()` method to their execution context
      implementation.  [ticket:1566]
      
    - Functions and operators generated by the compiler now use
      (almost) regular dispatch functions of the form
      "visit_<opname>" and "visit_<funcname>_fn" to provide
      customed processing. This replaces the need to copy the
      "functions" and "operators" dictionaries in compiler
      subclasses with straightforward visitor methods, and also
      allows compiler subclasses complete control over
      rendering, as the full _Function or _BinaryExpression
      object is passed in.

- postgresql
    - New dialects: pg8000, zxjdbc, and pypostgresql
      on py3k.
      
    - The "postgres" dialect is now named "postgresql" !
      Connection strings look like:

           postgresql://scott:tiger@localhost/test
           postgresql+pg8000://scott:tiger@localhost/test

       The "postgres" name remains for backwards compatiblity
       in the following ways:

           - There is a "postgres.py" dummy dialect which
             allows old URLs to work, i.e.
             postgres://scott:tiger@localhost/test

           - The "postgres" name can be imported from the old
             "databases" module, i.e. "from
             sqlalchemy.databases import postgres" as well as
             "dialects", "from sqlalchemy.dialects.postgres
             import base as pg", will send a deprecation
             warning.

           - Special expression arguments are now named
             "postgresql_returning" and "postgresql_where", but
             the older "postgres_returning" and
             "postgres_where" names still work with a
             deprecation warning.
    
    - "postgresql_where" now accepts SQL expressions which 
      can also include literals, which will be quoted as needed.
      
    - The psycopg2 dialect now uses psycopg2's "unicode extension"
      on all new connections, which allows all String/Text/etc.
      types to skip the need to post-process bytestrings into
      unicode (an expensive step due to its volume).  Other 
      dialects which return unicode natively (pg8000, zxjdbc)
      also skip unicode post-processing.
      
    - Added new ENUM type, which exists as a schema-level
      construct and extends the generic Enum type.  Automatically
      associates itself with tables and their parent metadata
      to issue the appropriate CREATE TYPE/DROP TYPE 
      commands as needed, supports unicode labels, supports
      reflection.  [ticket:1511]
    
    - INTERVAL supports an optional "precision" argument 
      corresponding to the argument that PG accepts.

    - using new dialect.initialize() feature to set up
      version-dependent behavior.

    - somewhat better support for % signs in table/column names;
      psycopg2 can't handle a bind parameter name of 
      %(foobar)s however and SQLA doesn't want to add overhead
      just to treat that one non-existent use case.
      [ticket:1279]
    
    - Inserting NULL into a primary key + foreign key column
      will allow the "not null constraint" error to raise,
      not an attempt to execute a nonexistent "col_id_seq" 
      sequence.  [ticket:1516]
    
    - autoincrement SELECT statements, i.e. those which 
      select from a procedure that modifies rows, now work 
      with server-side cursor mode (the named cursor isn't 
      used for such statements.)
    
    - postgresql dialect can properly detect pg "devel" version
      strings, i.e. "8.5devel" [ticket:1636]

    - The psycopg2 now respects the statement option
      "stream_results". This option overrides the connection setting
      "server_side_cursors". If true, server side cursors will be
      used for the statement. If false, they will not be used, even
      if "server_side_cursors" is true on the
      connection. [ticket:1619]
      
- mysql
    - New dialects: oursql, a new native dialect, 
      MySQL Connector/Python, a native Python port of MySQLdb,
      and of course zxjdbc on Jython.
    
    - VARCHAR/NVARCHAR will not render without a length, raises
      an error before passing to MySQL.   Doesn't impact 
      CAST since VARCHAR is not allowed in MySQL CAST anyway,
      the dialect renders CHAR/NCHAR in those cases.
      
    - all the _detect_XXX() functions now run once underneath
      dialect.initialize()

    - somewhat better support for % signs in table/column names;
      MySQLdb can't handle % signs in SQL when executemany() is used,
      and SQLA doesn't want to add overhead just to treat that one 
      non-existent use case. [ticket:1279]
    
    - the BINARY and MSBinary types now generate "BINARY" in all
      cases.  Omitting the "length" parameter will generate
      "BINARY" with no length.  Use BLOB to generate an unlengthed
      binary column.
      
    - the "quoting='quoted'" argument to MSEnum/ENUM is deprecated.
      It's best to rely upon the automatic quoting.
      
    - ENUM now subclasses the new generic Enum type, and also handles
      unicode values implicitly, if the given labelnames are unicode
      objects.
    
    - a column of type TIMESTAMP now defaults to NULL if
      "nullable=False" is not passed to Column(), and no default
      is present. This is now consistent with all other types, 
      and in the case of TIMESTAMP explictly renders "NULL" 
      due to MySQL's "switching" of default nullability
      for TIMESTAMP columns. [ticket:1539]
      
- oracle
    - unit tests pass 100% with cx_oracle !

    - support for cx_Oracle's "native unicode" mode which does
      not require NLS_LANG to be set. Use the latest 5.0.2 or
      later of cx_oracle.

    - an NCLOB type is added to the base types.
    
    - use_ansi=False won't leak into the FROM/WHERE clause of
      a statement that's selecting from a subquery that also
      uses JOIN/OUTERJOIN.
      
    - added native INTERVAL type to the dialect.  This supports
      only the DAY TO SECOND interval type so far due to lack 
      of support in cx_oracle for YEAR TO MONTH. [ticket:1467]
      
    - usage of the CHAR type results in cx_oracle's 
      FIXED_CHAR dbapi type being bound to statements.
      
    - the Oracle dialect now features NUMBER which intends
      to act justlike Oracle's NUMBER type.  It is the primary
      numeric type returned by table reflection and attempts
      to return Decimal()/float/int based on the precision/scale
      parameters.  [ticket:885]
      
    - func.char_length is a generic function for LENGTH

    - ForeignKey() which includes onupdate=<value> will emit a
      warning, not emit ON UPDATE CASCADE which is unsupported
      by oracle

    - the keys() method of RowProxy() now returns the result
      column names *normalized* to be SQLAlchemy case
      insensitive names. This means they will be lower case for
      case insensitive names, whereas the DBAPI would normally
      return them as UPPERCASE names. This allows row keys() to
      be compatible with further SQLAlchemy operations.

    - using new dialect.initialize() feature to set up
      version-dependent behavior.
    
    - using types.BigInteger with Oracle will generate
      NUMBER(19) [ticket:1125]
    
    - "case sensitivity" feature will detect an all-lowercase
      case-sensitive column name during reflect and add 
      "quote=True" to the generated Column, so that proper
      quoting is maintained.
      
- firebird
    - the keys() method of RowProxy() now returns the result
      column names *normalized* to be SQLAlchemy case
      insensitive names. This means they will be lower case for
      case insensitive names, whereas the DBAPI would normally
      return them as UPPERCASE names. This allows row keys() to
      be compatible with further SQLAlchemy operations.

    - using new dialect.initialize() feature to set up
      version-dependent behavior.

    - "case sensitivity" feature will detect an all-lowercase
      case-sensitive column name during reflect and add 
      "quote=True" to the generated Column, so that proper
      quoting is maintained.

- mssql
    - MSSQL + Pyodbc + FreeTDS now works for the most part,
      with possible exceptions regarding binary data as well as
      unicode schema identifiers.
    - the "has_window_funcs" flag is removed. LIMIT/OFFSET
      usage will use ROW NUMBER as always, and if on an older
      version of SQL Server, the operation fails. The behavior
      is exactly the same except the error is raised by SQL
      server instead of the dialect, and no flag setting is
      required to enable it.
    - the "auto_identity_insert" flag is removed. This feature
      always takes effect when an INSERT statement overrides a
      column that is known to have a sequence on it. As with
      "has_window_funcs", if the underlying driver doesn't
      support this, then you can't do this operation in any
      case, so there's no point in having a flag.
    - using new dialect.initialize() feature to set up
      version-dependent behavior.
    - removed references to sequence which is no longer used.
      implicit identities in mssql work the same as implicit
      sequences on any other dialects. Explicit sequences are
      enabled through the use of "default=Sequence()". See
      the MSSQL dialect documentation for more information.

- sqlite
    - DATE, TIME and DATETIME types can now take optional storage_format
      and regexp argument. storage_format can be used to store those types
      using a custom string format. regexp allows to use a custom regular
      expression to match string values from the database.
    - Time and DateTime types now use by a default a stricter regular
      expression to match strings from the database. Use the regexp
      argument if you are using data stored in a legacy format.
    - __legacy_microseconds__ on SQLite Time and DateTime types is not
      supported anymore. You should use the storage_format argument
      instead.
    - Date, Time and DateTime types are now stricter in what they accept as
      bind parameters: Date type only accepts date objects (and datetime
      ones, because they inherit from date), Time only accepts time
      objects, and DateTime only accepts date and datetime objects.
    - Table() supports a keyword argument "sqlite_autoincrement", which
      applies the SQLite keyword "AUTOINCREMENT" to the single integer
      primary key column when generating DDL. Will prevent generation of 
      a separate PRIMARY KEY constraint. [ticket:1016]
      
- new dialects
    - postgresql+pg8000
    - postgresql+pypostgresql (partial)
    - postgresql+zxjdbc
    - mysql+pyodbc
    - mysql+zxjdbc

- types
    - The construction of types within dialects has been totally
      overhauled.  Dialects now define publically available types
      as UPPERCASE names exclusively, and internal implementation
      types using underscore identifiers (i.e. are private).
      The system by which types are expressed in SQL and DDL
      has been moved to the compiler system.  This has the 
      effect that there are much fewer type objects within
      most dialects. A detailed document on this architecture
      for dialect authors is in 
      lib/sqlalchemy/dialects/type_migration_guidelines.txt .

    - Types no longer make any guesses as to default
      parameters. In particular, Numeric, Float, NUMERIC,
      FLOAT, DECIMAL don't generate any length or scale unless
      specified.
    
    - types.Binary is renamed to types.LargeBinary, it only
      produces BLOB, BYTEA, or a similar "long binary" type.   
      New base BINARY and VARBINARY
      types have been added to access these MySQL/MS-SQL specific
      types in an agnostic way [ticket:1664].
      
    - String/Text/Unicode types now skip the unicode() check
      on each result column value if the dialect has 
      detected the DBAPI as returning Python unicode objects
      natively.  This check is issued on first connect
      using "SELECT CAST 'some text' AS VARCHAR(10)" or
      equivalent, then checking if the returned object
      is a Python unicode.   This allows vast performance
      increases for native-unicode DBAPIs, including
      pysqlite/sqlite3, psycopg2, and pg8000.

    - Most types result processors have been checked for possible speed
      improvements. Specifically, the following generic types have been 
      optimized, resulting in varying speed improvements: 
      Unicode, PickleType, Interval, TypeDecorator, Binary. 
      Also the following dbapi-specific implementations have been improved:
      Time, Date and DateTime on Sqlite, ARRAY on Postgresql,
      Time on MySQL, Numeric(as_decimal=False) on MySQL, oursql and 
      pypostgresql, DateTime on cx_oracle and LOB-based types on cx_oracle.
      
    - Reflection of types now returns the exact UPPERCASE
      type within types.py, or the UPPERCASE type within
      the dialect itself if the type is not a standard SQL 
      type.  This means reflection now returns more accurate
      information about reflected types.  
    
    - Added a new Enum generic type. Enum is a schema-aware object
      to support databases which require specific DDL in order to
      use enum or equivalent; in the case of PG it handles the
      details of `CREATE TYPE`, and on other databases without
      native enum support will by generate VARCHAR + an inline CHECK
      constraint to enforce the enum.
      [ticket:1109] [ticket:1511]
    
    - The Interval type includes a "native" flag which controls
      if native INTERVAL types (postgresql + oracle) are selected
      if available, or not.  "day_precision" and "second_precision"
      arguments are also added which propagate as appropriately
      to these native types. Related to [ticket:1467].
      
    - The Boolean type, when used on a backend that doesn't 
      have native boolean support, will generate a CHECK 
      constraint "col IN (0, 1)" along with the int/smallint-
      based column type.  This can be switched off if 
      desired with create_constraint=False. 
      Note that MySQL has no native boolean *or* CHECK constraint
      support so this feature isn't available on that platform.
      [ticket:1589]
      
    - PickleType now uses == for comparison of values when
      mutable=True, unless the "comparator" argument with a
      comparsion function is specified to the type. Objects
      being pickled will be compared based on identity (which
      defeats the purpose of mutable=True) if __eq__() is not
      overridden or a comparison function is not provided.
      
    - The default "precision" and "scale" arguments of Numeric
      and Float have been removed and now default to None.
      NUMERIC and FLOAT will be rendered with no numeric
      arguments by default unless these values are provided.

    - AbstractType.get_search_list() is removed - the games
      that was used for are no longer necessary.
    
    - Added a generic BigInteger type, compiles to 
      BIGINT or NUMBER(19). [ticket:1125]

-ext
    - sqlsoup has been overhauled to explicitly support an 0.5 style
      session, using autocommit=False, autoflush=True. Default
      behavior of SQLSoup now requires the usual usage of commit()
      and rollback(), which have been added to its interface. An
      explcit Session or scoped_session can be passed to the
      constructor, allowing these arguments to be overridden.

    - sqlsoup db.<sometable>.update() and delete() now call
      query(cls).update() and delete(), respectively.
    
    - sqlsoup now has execute() and connection(), which call upon
      the Session methods of those names, ensuring that the bind is
      in terms of the SqlSoup object's bind.
    
    - sqlsoup objects no longer have the 'query' attribute - it's
      not needed for sqlsoup's usage paradigm and it gets in the
      way of a column that is actually named 'query'.
      
    - The signature of the proxy_factory callable passed to 
      association_proxy is now (lazy_collection, creator, 
      value_attr, association_proxy), adding a fourth argument
      that is the parent AssociationProxy argument.  Allows
      serializability and subclassing of the built in collections.
      [ticket:1259]

    - association_proxy now has basic comparator methods .any(),
      .has(), .contains(), ==, !=, thanks to Scott Torborg.
      [ticket:1372]
      
- examples
    - The "query_cache" examples have been removed, and are replaced
      with a fully comprehensive approach that combines the usage of
      Beaker with SQLAlchemy.  New query options are used to indicate
      the caching characteristics of a particular Query, which 
      can also be invoked deep within an object graph when lazily
      loading related objects.  See /examples/beaker_caching/README.
    
0.5.9
=====
- sql
    - Fixed erroneous self_group() call in expression package.
      [ticket:1661]
    
0.5.8
=====
- sql
    - The copy() method on Column now supports uninitialized,
      unnamed Column objects. This allows easy creation of 
      declarative helpers which place common columns on multiple 
      subclasses.
    
    - Default generators like Sequence() translate correctly
      across a copy() operation.
      
    - Sequence() and other DefaultGenerator objects are accepted 
      as the value for the "default" and "onupdate" keyword
      arguments of Column, in addition to being accepted
      positionally.  
      
    - Fixed a column arithmetic bug that affected column
      correspondence for cloned selectables which contain
      free-standing column expressions.   This bug is
      generally only noticeable when exercising newer 
      ORM behavior only availble in 0.6 via [ticket:1568], 
      but is more correct at the SQL expression level 
      as well. [ticket:1617]
    
- postgresql
    - The extract() function, which was slightly improved in
      0.5.7, needed a lot more work to generate the correct
      typecast (the typecasts appear to be necessary in PG's
      EXTRACT quite a lot of the time).  The typecast is 
      now generated using a rule dictionary based 
      on PG's documentation for date/time/interval arithmetic.
      It also accepts text() constructs again, which was broken
      in 0.5.7. [ticket:1647]

- firebird 
    - Recognize more errors as disconnections. [ticket:1646]

0.5.7
=====
- orm
    - contains_eager() now works with the automatically 
      generated subquery that results when you say 
      "query(Parent).join(Parent.somejoinedsubclass)", i.e. 
      when Parent joins to a joined-table-inheritance subclass.  
      Previously contains_eager() would erroneously add the 
      subclass table to the query separately producing a 
      cartesian product.  An example is in the ticket
      description.  [ticket:1543]
    
    - query.options() now only propagate to loaded objects
      for potential further sub-loads only for options where
      such behavior is relevant, keeping
      various unserializable options like those generated
      by contains_eager() out of individual instance states.
      [ticket:1553]
    
    - Session.execute() now locates table- and 
      mapper-specific binds based on a passed
      in expression which is an insert()/update()/delete() 
      construct. [ticket:1054]
      
    - Session.merge() now properly overwrites a many-to-one or 
      uselist=False attribute to None if the attribute 
      is also None in the given object to be merged.
     
    - Fixed a needless select which would occur when merging
      transient objects that contained a null primary key
      identifier.  [ticket:1618]

    - Mutable collection passed to the "extension" attribute
      of relation(), column_property() etc. will not be mutated
      or shared among multiple instrumentation calls, preventing
      duplicate extensions, such as backref populators,
      from being inserted into the list.
      [ticket:1585]
    
    - Fixed the call to get_committed_value() on CompositeProperty.
      [ticket:1504]

    - Fixed bug where Query would crash if a join() with no clear
      "left" side were called when a non-mapped column entity
      appeared in the columns list. [ticket:1602]
    
    - Fixed bug whereby composite columns wouldn't load properly
      when configured on a joined-table subclass, introduced in
      version 0.5.6 as a result of the fix for [ticket:1480].
      [ticket:1616] thx to Scott Torborg.

    - The "use get" behavior of many-to-one relations, i.e. that a 
      lazy load will fallback to the possibly cached query.get() 
      value, now works across join conditions where the two compared 
      types are not exactly the same class, but share the same 
      "affinity" - i.e. Integer and SmallInteger.  Also allows
      combinations of reflected and non-reflected types to work
      with 0.5 style type reflection, such as PGText/Text (note 0.6 
      reflects types as their generic versions).   [ticket:1556]
    
    - Fixed bug in query.update() when passing Cls.attribute
      as keys in the value dict and using synchronize_session='expire'
      ('fetch' in 0.6). [ticket:1436]
      
- sql
    - Fixed bug in two-phase transaction whereby commit() method
      didn't set the full state which allows subsequent close()
      call to succeed. [ticket:1603]
      
    - Fixed the "numeric" paramstyle, which apparently is the
      default paramstyle used by Informixdb.
      
    - Repeat expressions in the columns clause of a select
      are deduped based on the identity of each clause element,
      not the actual string.  This allows positional 
      elements to render correctly even if they all render
      identically, such as "qmark" style bind parameters.
      [ticket:1574]
    
    - The cursor associated with connection pool connections
      (i.e. _CursorFairy) now proxies `__iter__()` to the 
      underlying cursor correctly. [ticket:1632]

    - types now support an "affinity comparison" operation, i.e.
      that an Integer/SmallInteger are "compatible", or 
      a Text/String, PickleType/Binary, etc.  Part of 
      [ticket:1556].

    - Fixed bug preventing alias() of an alias() from being
      cloned or adapted (occurs frequently in ORM operations).
      [ticket:1641]
      
- sqlite
    - sqlite dialect properly generates CREATE INDEX for a table
      that is in an alternate schema.  [ticket:1439]
      
- postgresql
    - Added support for reflecting the DOUBLE PRECISION type,
      via a new postgres.PGDoublePrecision object.  
      This is postgresql.DOUBLE_PRECISION in 0.6.
      [ticket:1085]

    - Added support for reflecting the INTERVAL YEAR TO MONTH
      and INTERVAL DAY TO SECOND syntaxes of the INTERVAL 
      type.  [ticket:460]

    - Corrected the "has_sequence" query to take current schema,
      or explicit sequence-stated schema, into account.
      [ticket:1576]

    - Fixed the behavior of extract() to apply operator
      precedence rules to the "::" operator when applying
      the "timestamp" cast - ensures proper parenthesization.  
      [ticket:1611]

- mssql
    - Changed the name of TrustedConnection to
      Trusted_Connection when constructing pyodbc connect
      arguments [ticket:1561]

- oracle
     - The "table_names" dialect function, used by MetaData
       .reflect(), omits "index overflow tables", a system
       table generated by Oracle when "index only tables"
       with overflow are used.  These tables aren't accessible
       via SQL and can't be reflected.  [ticket:1637]
       
- ext 
    - A column can be added to a joined-table declarative 
      superclass after the class has been constructed 
      (i.e. via class-level attribute assignment), and
      the column will be propagated down to 
      subclasses. [ticket:1570]  This is the reverse
      situation as that of [ticket:1523], fixed in 0.5.6.

    - Fixed a slight inaccuracy in the sharding example.
      Comparing equivalence of columns in the ORM is best 
      accomplished using col1.shares_lineage(col2).
      [ticket:1491]
    
    - Removed unused `load()` method from ShardedQuery.
      [ticket:1606]
      
0.5.6
=====
- orm
    - Fixed bug whereby inheritance discriminator part of a
      composite primary key would fail on updates.
      Continuation of [ticket:1300].

    - Fixed bug which disallowed one side of a many-to-many 
      bidirectional reference to declare itself as "viewonly"
      [ticket:1507]
    
    - Added an assertion that prevents a @validates function
      or other AttributeExtension from loading an unloaded
      collection such that internal state may be corrupted.
      [ticket:1526]
      
    - Fixed bug which prevented two entities from mutually
      replacing each other's primary key values within a single
      flush() for some orderings of operations.  [ticket:1519]
      
    - Fixed an obscure issue whereby a joined-table subclass
      with a self-referential eager load on the base class
      would populate the related object's "subclass" table with
      data from the "subclass" table of the parent.
      [ticket:1485]
    
    - relations() now have greater ability to be "overridden",
      meaning a subclass that explicitly specifies a relation()
      overriding that of the parent class will be honored
      during a flush.  This is currently to support 
      many-to-many relations from concrete inheritance setups.
      Outside of that use case, YMMV.  [ticket:1477]
    
    - Squeezed a few more unnecessary "lazy loads" out of 
      relation().  When a collection is mutated, many-to-one
      backrefs on the other side will not fire off to load
      the "old" value, unless "single_parent=True" is set.  
      A direct assignment of a many-to-one still loads 
      the "old" value in order to update backref collections 
      on that value, which may be present in the session 
      already, thus maintaining the 0.5 behavioral contract.
      [ticket:1483]
      
    - Fixed bug whereby a load/refresh of joined table
      inheritance attributes which were based on 
      column_property() or similar would fail to evaluate.
      [ticket:1480]
    
    - Improved support for MapperProperty objects overriding
      that of an inherited mapper for non-concrete 
      inheritance setups - attribute extensions won't randomly
      collide with each other.  [ticket:1488]
    
    - UPDATE and DELETE do not support ORDER BY, LIMIT, OFFSET,
      etc. in standard SQL.  Query.update() and Query.delete()
      now raise an exception if any of limit(), offset(),
      order_by(), group_by(), or distinct() have been
      called. [ticket:1487]
      
    - Added AttributeExtension to sqlalchemy.orm.__all__
      
    - Improved error message when query() is called with
      a non-SQL /entity expression. [ticket:1476]
    
    - Using False or 0 as a polymorphic discriminator now
      works on the base class as well as a subclass.
      [ticket:1440]

    - Added enable_assertions(False) to Query which disables
      the usual assertions for expected state - used
      by Query subclasses to engineer custom state.
      [ticket:1424].  See
      http://www.sqlalchemy.org/trac/wiki/UsageRecipes/PreFilteredQuery
      for an example.

    - Fixed recursion issue which occured if a mapped object's
      `__len__()` or `__nonzero__()` method resulted in state
      changes.  [ticket:1501]

    - Fixed incorrect exception raise in 
      Weak/StrongIdentityMap.add() 
      [ticket:1506]

    - Fixed the error message for "could not find a FROM clause"
      in query.join() which would fail to issue correctly
      if the query was against a pure SQL construct.
      [ticket:1522]
    
    - Fixed a somewhat hypothetical issue which would result
      in the wrong primary key being calculated for a mapper
      using the old polymorphic_union function - but this
      is old stuff.  [ticket:1486]
      
- sql
    - Fixed column.copy() to copy defaults and onupdates.
      [ticket:1373]

    - Fixed a bug in extract() introduced in 0.5.4 whereby
      the string "field" argument was getting treated as a 
      ClauseElement, causing various errors within more 
      complex SQL transformations.
      
    - Unary expressions such as DISTINCT propagate their 
      type handling to result sets, allowing conversions like
      unicode and such to take place.  [ticket:1420]
    
    - Fixed bug in Table and Column whereby passing empty
      dict for "info" argument would raise an exception.
      [ticket:1482]

- oracle
    - Backported 0.6 fix for Oracle alias names not getting
      truncated.  [ticket:1309]
      
- ext
   - The collection proxies produced by associationproxy are now
     pickleable.  A user-defined proxy_factory however
     is still not pickleable unless it defines __getstate__
     and __setstate__. [ticket:1446]

   - Declarative will raise an informative exception if 
     __table_args__ is passed as a tuple with no dict argument.
     Improved documentation.  [ticket:1468]

   - Table objects declared in the MetaData can now be used
     in string expressions sent to primaryjoin/secondaryjoin/
     secondary - the name is pulled from the MetaData of the
     declarative base.  [ticket:1527]
     
   - A column can be added to a joined-table subclass after
     the class has been constructed (i.e. via class-level
     attribute assignment).  The column is added to the underlying
     Table as always, but now the mapper will rebuild its
     "join" to include the new column, instead of raising
     an error about "no such column, use column_property()
     instead".  [ticket:1523]
     
- test
   - Added examples into the test suite so they get exercised
     regularly and cleaned up a couple deprecation warnings.

     
0.5.5
=======
- general
    - unit tests have been migrated from unittest to nose.  See
      README.unittests for information on how to run the tests.
      [ticket:970]

- orm
    - The "foreign_keys" argument of relation() will now propagate
      automatically to the backref in the same way that primaryjoin
      and secondaryjoin do.  For the extremely rare use case where
      the backref of a relation() has intentionally different
      "foreign_keys" configured, both sides now need to be
      configured explicity (if they do in fact require this setting,
      see the next note...).

    - ...the only known (and really, really rare) use case where a
      different foreign_keys setting was used on the
      forwards/backwards side, a composite foreign key that
      partially points to its own columns, has been enhanced such
      that the fk->itself aspect of the relation won't be used to
      determine relation direction.

    - Session.mapper is now *deprecated*.

      Call session.add() if you'd like a free-standing object to be
      part of your session.  Otherwise, a DIY version of
      Session.mapper is now documented at
      http://www.sqlalchemy.org/trac/wiki/UsageRecipes/SessionAwareMapper
      The method will remain deprecated throughout 0.6.

    - Fixed Query being able to join() from individual columns of a
      joined-table subclass entity, i.e.  query(SubClass.foo,
      SubcClass.bar).join(<anything>).  In most cases, an error
      "Could not find a FROM clause to join from" would be
      raised. In a few others, the result would be returned in terms
      of the base class rather than the subclass - so applications
      which relied on this erroneous result need to be
      adjusted. [ticket:1431]

    - Fixed a bug involving contains_eager(), which would apply
      itself to a secondary (i.e. lazy) load in a particular rare
      case, producing cartesian products.  improved the targeting of
      query.options() on secondary loads overall [ticket:1461].

    - Fixed bug introduced in 0.5.4 whereby Composite types fail
      when default-holding columns are flushed.

    - Fixed another 0.5.4 bug whereby mutable attributes
      (i.e. PickleType) wouldn't be deserialized correctly when the
      whole object was serialized.  [ticket:1426]

    - Fixed bug whereby session.is_modified() would raise an
      exception if any synonyms were in use.

    - Fixed potential memory leak whereby previously pickled objects
      placed back in a session would not be fully garbage collected
      unless the Session were explicitly closed out.

    - Fixed bug whereby list-based attributes, like pickletype and
      PGArray, failed to be merged() properly.

    - Repaired non-working attributes.set_committed_value function.

    - Trimmed the pickle format for InstanceState which should
      further reduce the memory footprint of pickled instances.  The
      format should be backwards compatible with that of 0.5.4 and
      previous.

    - sqlalchemy.orm.join and sqlalchemy.orm.outerjoin are now
      added to __all__ in sqlalchemy.orm.*. [ticket:1463]

    - Fixed bug where Query exception raise would fail when
      a too-short composite primary key value were passed to
      get().  [ticket:1458]

- sql
    - Removed an obscure feature of execute() (including connection,
      engine, Session) whereby a bindparam() construct can be sent
      as a key to the params dictionary.  This usage is undocumented
      and is at the core of an issue whereby the bindparam() object
      created implicitly by a text() construct may have the same
      hash value as a string placed in the params dictionary and may
      result in an inappropriate match when computing the final bind
      parameters.  Internal checks for this condition would add
      significant latency to the critical task of parameter
      rendering, so the behavior is removed.  This is a backwards
      incompatible change for any application that may have been
      using this feature, however the feature has never been
      documented.

- engine/pool
    - Implemented recreate() for StaticPool.


0.5.4p2
=======

- sql
    - Repaired the printing of SQL exceptions which are not 
      based on parameters or are not executemany() style.
      
- postgresql
    - Deprecated the hardcoded TIMESTAMP function, which when
      used as func.TIMESTAMP(value) would render "TIMESTAMP value".
      This breaks on some platforms as PostgreSQL doesn't allow
      bind parameters to be used in this context.  The hard-coded
      uppercase is also inappropriate and there's lots of other
      PG casts that we'd need to support.  So instead, use
      text constructs i.e. select(["timestamp '12/05/09'"]).
      
      
0.5.4p1
=======

- orm
    - Fixed an attribute error introduced in 0.5.4 which would 
      occur when merge() was used with an incomplete object.
    
0.5.4
=====

- orm
    - Significant performance enhancements regarding Sessions/flush()
      in conjunction with large mapper graphs, large numbers of 
      objects:
      
      - Removed all* O(N) scanning behavior from the flush() process,
        i.e. operations that were scanning the full session, 
        including an extremely expensive one that was erroneously
        assuming primary key values were changing when this 
        was not the case.
        
        * one edge case remains which may invoke a full scan,
          if an existing primary key attribute is modified
          to a new value.
      
      - The Session's "weak referencing" behavior is now *full* -
        no strong references whatsoever are made to a mapped object
        or related items/collections in its __dict__.  Backrefs and 
        other cycles in objects no longer affect the Session's ability 
        to lose all references to unmodified objects.  Objects with 
        pending changes still are maintained strongly until flush.  
        [ticket:1398]
        
        The implementation also improves performance by moving
        the "resurrection" process of garbage collected items
        to only be relevant for mappings that map "mutable" 
        attributes (i.e. PickleType, composite attrs).  This removes
        overhead from the gc process and simplifies internal 
        behavior.
        
        If a "mutable" attribute change is the sole change on an object 
        which is then dereferenced, the mapper will not have access to 
        other attribute state when the UPDATE is issued.  This may present 
        itself differently to some MapperExtensions.
        
        The change also affects the internal attribute API, but not
        the AttributeExtension interface nor any of the publically
        documented attribute functions.
        
      - The unit of work no longer genererates a graph of "dependency"
        processors for the full graph of mappers during flush(), instead
        creating such processors only for those mappers which represent
        objects with pending changes.  This saves a tremendous number
        of method calls in the context of a large interconnected 
        graph of mappers.
        
      - Cached a wasteful "table sort" operation that previously
        occured multiple times per flush, also removing significant
        method call count from flush().
        
      - Other redundant behaviors have been simplified in 
        mapper._save_obj().
      
    - Modified query_cls on DynamicAttributeImpl to accept a full
      mixin version of the AppenderQuery, which allows subclassing
      the AppenderMixin.

    - The "polymorphic discriminator" column may be part of a 
      primary key, and it will be populated with the correct 
      discriminator value.  [ticket:1300]
      
    - Fixed the evaluator not being able to evaluate IS NULL clauses.

    - Fixed the "set collection" function on "dynamic" relations to
      initiate events correctly.  Previously a collection could only
      be assigned to a pending parent instance, otherwise modified
      events would not be fired correctly.  Set collection is now
      compatible with merge(), fixes [ticket:1352].
    
    - Allowed pickling of PropertyOption objects constructed with
      instrumented descriptors; previously, pickle errors would occur 
      when pickling an object which was loaded with a descriptor-based 
      option, such as query.options(eagerload(MyClass.foo)).
      
    - Lazy loader will not use get() if the "lazy load" SQL clause
      matches the clause used by get(), but contains some parameters
      hardcoded.  Previously the lazy strategy would fail with the
      get().  Ideally get() would be used with the hardcoded
      parameters but this would require further development.
      [ticket:1357]

    - MapperOptions and other state associated with query.options()
      is no longer bundled within callables associated with each 
      lazy/deferred-loading attribute during a load.
      The options are now associated with the instance's
      state object just once when it's populated.  This removes
      the need in most cases for per-instance/attribute loader 
      objects, improving load speed and memory overhead for
      individual instances. [ticket:1391]
      
    - Fixed another location where autoflush was interfering
      with session.merge().  autoflush is disabled completely
      for the duration of merge() now. [ticket:1360]
    
    - Fixed bug which prevented "mutable primary key" dependency
      logic from functioning properly on a one-to-one
      relation().  [ticket:1406]
      
    - Fixed bug in relation(), introduced in 0.5.3, 
      whereby a self referential relation
      from a base class to a joined-table subclass would 
      not configure correctly.

    - Fixed obscure mapper compilation issue when inheriting
      mappers are used which would result in un-initialized
      attributes.
      
    - Fixed documentation for session weak_identity_map - 
      the default value is True, indicating a weak
      referencing map in use.
      
    - Fixed a unit of work issue whereby the foreign
      key attribute on an item contained within a collection 
      owned by an object being deleted would not be set to
      None if the relation() was self-referential. [ticket:1376]

    - Fixed Query.update() and Query.delete() failures with eagerloaded
      relations. [ticket:1378]

    - It is now an error to specify both columns of a binary primaryjoin
      condition in the foreign_keys or remote_side collection.  Whereas
      previously it was just nonsensical, but would succeed in a 
      non-deterministic way.
      
- schema
    - Added a quote_schema() method to the IdentifierPreparer class
      so that dialects can override how schemas get handled. This
      enables the MSSQL dialect to treat schemas as multipart
      identifiers, such as 'database.owner'. [ticket: 594, 1341]

- sql
    - Back-ported the "compiler" extension from SQLA 0.6.  This
      is a standardized interface which allows the creation of custom
      ClauseElement subclasses and compilers.  In particular it's
      handy as an alternative to text() when you'd like to 
      build a construct that has database-specific compilations.
      See the extension docs for details.
      
    - Exception messages are truncated when the list of bound 
      parameters is larger than 10, preventing enormous
      multi-page exceptions from filling up screens and logfiles
      for large executemany() statements. [ticket:1413]
      
    - ``sqlalchemy.extract()`` is now dialect sensitive and can
      extract components of timestamps idiomatically across the
      supported databases, including SQLite.

    - Fixed __repr__() and other _get_colspec() methods on
      ForeignKey constructed from __clause_element__() style
      construct (i.e. declarative columns).  [ticket:1353]

- mysql
    - Reflecting a FOREIGN KEY construct will take into account
      a dotted schema.tablename combination, if the foreign key
      references a table in a remote schema. [ticket:1405]
      
- mssql
    - Modified how savepoint logic works to prevent it from
      stepping on non-savepoint oriented routines. Savepoint
      support is still very experimental.

    - Added in reserved words for MSSQL that covers version 2008
      and all prior versions. [ticket:1310]

    - Corrected problem with information schema not working with a
      binary collation based database. Cleaned up information schema
      since it is only used by mssql now. [ticket:1343]

- sqlite
    - Corrected the SLBoolean type so that it properly treats only 1
      as True. [ticket:1402]

    - Corrected the float type so that it correctly maps to a
      SLFloat type when being reflected. [ticket:1273]

- extensions

    - Fixed adding of deferred or other column properties to a
      declarative class. [ticket:1379]

0.5.3
=====
- orm
    - The "objects" argument to session.flush() is deprecated.
      State which represents the linkage between a parent and
      child object does not support "flushed" status on
      one side of the link and not the other, so supporting
      this operation leads to misleading results.
      [ticket:1315]
    
    - Query now implements __clause_element__() which produces
      its selectable, which means a Query instance can be accepted 
      in many SQL expressions, including col.in_(query), 
      union(query1, query2), select([foo]).select_from(query), 
      etc.

    - Query.join() can now construct multiple FROM clauses, if 
      needed.  Such as, query(A, B).join(A.x).join(B.y)
      might say SELECT A.*, B.* FROM A JOIN X, B JOIN Y.  
      Eager loading can also tack its joins onto those 
      multiple FROM clauses.  [ticket:1337]

    - Fixed bug in dynamic_loader() where append/remove events
      after construction time were not being propagated to the 
      UOW to pick up on flush(). [ticket:1347]
      
    - Fixed bug where column_prefix wasn't being checked before
      not mapping an attribute that already had class-level 
      name present.

    - a session.expire() on a particular collection attribute
      will clear any pending backref additions as well, so that
      the next access correctly returns only what was present
      in the database.  Presents some degree of a workaround for 
      [ticket:1315], although we are considering removing the 
      flush([objects]) feature altogether.
    
    - Session.scalar() now converts raw SQL strings to text()
      the same way Session.execute() does and accepts same 
      alternative **kw args.
      
    - improvements to the "determine direction" logic of 
      relation() such that the direction of tricky situations 
      like mapper(A.join(B)) -> relation-> mapper(B) can be
      determined.
      
    - When flushing partial sets of objects using session.flush([somelist]),
      pending objects which remain pending after the operation won't
      inadvertently be added as persistent. [ticket:1306]
     
    - Added "post_configure_attribute" method to InstrumentationManager,
      so that the "listen_for_events.py" example works again.
      [ticket:1314]
    
    - a forward and complementing backwards reference which are both
      of the same direction, i.e. ONETOMANY or MANYTOONE, 
      is now detected, and an error message is raised.   
      Saves crazy CircularDependencyErrors later on.
        
    - Fixed bugs in Query regarding simultaneous selection of 
      multiple joined-table inheritance entities with common base 
      classes:
      
      - previously the adaption applied to "B" on 
        "A JOIN B" would be erroneously partially applied 
        to "A".
      
      - comparisons on relations (i.e. A.related==someb)
        were not getting adapted when they should.
      
      - Other filterings, like 
        query(A).join(A.bs).filter(B.foo=='bar'), were erroneously
        adapting "B.foo" as though it were an "A".
    
     - Fixed adaptation of EXISTS clauses via any(), has(), etc.
       in conjunction with an aliased object on the left and 
       of_type() on the right.  [ticket:1325]
       
     - Added an attribute helper method ``set_committed_value`` in 
       sqlalchemy.orm.attributes.  Given an object, attribute name,
       and value, will set the value on the object as part of its
       "committed" state, i.e. state that is understood to have 
       been loaded from the database.   Helps with the creation of 
       homegrown collection loaders and such.

     - Query won't fail with weakref error when a non-mapper/class
       instrumented descriptor is passed, raises 
       "Invalid column expession".
    
     - Query.group_by() properly takes into account aliasing applied
       to the FROM clause, such as with select_from(), using
       with_polymorphic(), or using from_self().
        
- sql
    - An alias() of a select() will convert to a "scalar subquery"
      when used in an unambiguously scalar context, i.e. it's used 
      in a comparison operation.  This applies to
      the ORM when using query.subquery() as well.
      
    - Fixed missing _label attribute on Function object, others
      when used in a select() with use_labels (such as when used
      in an ORM column_property()).  [ticket:1302]

    - anonymous alias names now truncate down to the max length
      allowed by the dialect.  More significant on DBs like
      Oracle with very small character limits. [ticket:1309]
      
    - the __selectable__() interface has been replaced entirely
      by __clause_element__().

    - The per-dialect cache used by TypeEngine to cache
      dialect-specific types is now a WeakKeyDictionary.
      This to prevent dialect objects from 
      being referenced forever for an application that 
      creates an arbitrarily large number of engines
      or dialects.   There is a small performance penalty
      which will be resolved in 0.6.  [ticket:1299]

- sqlite
    - Fixed SQLite reflection methods so that non-present
      cursor.description, which triggers an auto-cursor
      close, will be detected so that no results doesn't
      fail on recent versions of pysqlite which raise 
      an error when fetchone() called with no rows present.
      
- postgresql
    - Index reflection won't fail when an index with 
      multiple expressions is encountered.
      
    - Added PGUuid and PGBit types to 
      sqlalchemy.databases.postgres. [ticket:1327]
    
    - Refection of unknown PG types won't crash when those
      types are specified within a domain.  [ticket:1327]

- mssql
    - Preliminary support for pymssql 1.0.1

    - Corrected issue on mssql where max_identifier_length was
      not being respected.

- extensions

    - Fixed a recursive pickling issue in serializer, triggered
      by an EXISTS or other embedded FROM construct.

    - Declarative locates the "inherits" class using a search
      through __bases__, to skip over mixins that are local
      to subclasses.   
      
    - Declarative figures out joined-table inheritance primary join
      condition even if "inherits" mapper argument is given 
      explicitly. 

    - Declarative will properly interpret the "foreign_keys" argument
      on a backref() if it's a string.
      
    - Declarative will accept a table-bound column as a property
      when used in conjunction with __table__, if the column is already
      present in __table__.  The column will be remapped to the given 
      key the same way as when added to the mapper() properties dict.
      
0.5.2
======

- orm
    - Further refined 0.5.1's warning about delete-orphan cascade
      placed on a many-to-many relation.   First, the bad news:
      the warning will apply to both many-to-many as well as
      many-to-one relations.  This is necessary since in both 
      cases, SQLA does not scan the full set of potential parents
      when determining "orphan" status - for a persistent object
      it only detects an in-python de-association event to establish
      the object as an "orphan".  Next, the good news: to support 
      one-to-one via a foreign key or assocation table, or to 
      support one-to-many via an association table, a new flag 
      single_parent=True may be set which indicates objects 
      linked to the relation are only meant to have a single parent.
      The relation will raise an error if multiple parent-association
      events occur within Python.

    - Adjusted the attribute instrumentation change from 0.5.1 to 
      fully establish instrumentation for subclasses where the mapper
      was created after the superclass had already been fully
      instrumented. [ticket:1292]
      
    - Fixed bug in delete-orphan cascade whereby two one-to-one
      relations from two different parent classes to the same target 
      class would prematurely expunge the instance.

    - Fixed an eager loading bug whereby self-referential eager 
      loading would prevent other eager loads, self referential or not,
      from joining to the parent JOIN properly.  Thanks to Alex K
      for creating a great test case.
    
    - session.expire() and related methods will not expire() unloaded
      deferred attributes.  This prevents them from being needlessly
      loaded when the instance is refreshed.

    - query.join()/outerjoin() will now properly join an aliased()
      construct to the existing left side, even if query.from_self()
      or query.select_from(someselectable) has been called.
      [ticket:1293]
      
- sql
    - Further fixes to the "percent signs and spaces in column/table
       names" functionality. [ticket:1284]

- mssql
    - Restored convert_unicode handling. Results were being passed
      on through without conversion. [ticket:1291]

    - Really fixing the decimal handling this time. [ticket:1282].

    - Modified table reflection code to use only kwargs when 
      constructing tables. [Ticket:1289]

0.5.1
========

- orm
    - Removed an internal join cache which could potentially leak 
      memory when issuing query.join() repeatedly to ad-hoc 
      selectables.

    - The "clear()", "save()", "update()", "save_or_update()"
      Session methods have been deprecated, replaced by 
      "expunge_all()" and "add()".  "expunge_all()" has also
      been added to ScopedSession.
      
    - Modernized the "no mapped table" exception and added a more
      explicit __table__/__tablename__ exception to declarative.

    - Concrete inheriting mappers now instrument attributes which
      are inherited from the superclass, but are not defined for
      the concrete mapper itself, with an InstrumentedAttribute that
      issues a descriptive error when accessed. [ticket:1237]

    - Added a new `relation()` keyword `back_populates`. This
      allows configuation of backreferences using explicit
      relations. [ticket:781] This is required when creating
      bidirectional relations between a hierarchy of concrete
      mappers and another class. [ticket:1237]

    - Test coverage added for `relation()` objects specified on
      concrete mappers. [ticket:1237]
    
    - Query.from_self() as well as query.subquery() both disable 
      the rendering of eager joins inside the subquery produced.
      The "disable all eager joins" feature is available publically
      via a new query.enable_eagerloads() generative. [ticket:1276]
      
    - Added a rudimental series of set operations to Query that
      receive Query objects as arguments, including union(),
      union_all(), intersect(), except_(), insertsect_all(),
      except_all().  See the API documentation for
      Query.union() for examples. 

    - Fixed bug that prevented Query.join() and eagerloads from 
      attaching to a query that selected from a union or aliased union.
      
    - A short documentation example added for bidirectional
      relations specified on concrete mappers. [ticket:1237]

    - Mappers now instrument class attributes upon construction
      with the final InstrumentedAttribute object which remains
      persistent. The `_CompileOnAttr`/`__getattribute__()`
      methodology has been removed. The net effect is that
      Column-based mapped class attributes can now be used fully
      at the class level without invoking a mapper compilation
      operation, greatly simplifying typical usage patterns
      within declarative. [ticket:1269]

    - ColumnProperty (and front-end helpers such as ``deferred``) no
      longer ignores unknown **keyword arguments.

    - Fixed a bug with the unitofwork's "row switch" mechanism,
      i.e. the conversion of INSERT/DELETE into an UPDATE, when
      combined with joined-table inheritance and an object
      which contained no defined values for the child table where
      an UPDATE with no SET clause would be rendered.

    - Using delete-orphan on a many-to-many relation is deprecated.
      This produces misleading or erroneous results since SQLA does 
      not retrieve the full list of "parents" for m2m.  To get delete-orphan
      behavior with an m2m table, use an explcit association class
      so that the individual association row is treated as a parent.
      [ticket:1281]
    
    - delete-orphan cascade always requires delete cascade.  Specifying
      delete-orphan without delete now raises a deprecation warning.
      [ticket:1281]
      
- sql
    - Improved the methodology to handling percent signs in column
      names from [ticket:1256].  Added more tests.  MySQL and
      PostgreSQL dialects still do not issue correct CREATE TABLE
      statements for identifiers with percent signs in them.
      
- schema
    - Index now accepts column-oriented InstrumentedAttributes
      (i.e. column-based mapped class attributes) as column
      arguments. [ticket:1214]

    - Column with no name (as in declarative) won't raise a 
      NoneType error when it's string output is requsted
      (such as in a stack trace).
      
    - Fixed bug when overriding a Column with a ForeignKey
      on a reflected table, where derived columns (i.e. the 
      "virtual" columns of a select, etc.) would inadvertently
      call upon schema-level cleanup logic intended only
      for the original column. [ticket:1278]
      
- declarative
    - Can now specify Column objects on subclasses which have no
      table of their own (i.e. use single table inheritance).  
      The columns will be appended to the base table, but only
      mapped by the subclass.

    - For both joined and single inheriting subclasses, the subclass
      will only map those columns which are already mapped on the 
      superclass and those explicit on the subclass.  Other 
      columns that are present on the `Table` will be excluded
      from the mapping by default, which can be disabled
      by passing a blank `exclude_properties` collection to the
      `__mapper_args__`.  This is so that single-inheriting
      classes which define their own columns are the only classes
      to map those columns.   The effect is actually a more organized
      mapping than you'd normally get with explicit `mapper()`
      calls unless you set up the `exclude_properties` arguments
      explicitly.

    - It's an error to add new Column objects to a declarative class
      that specified an existing table using __table__.
      
- mysql
    - Added the missing keywords from MySQL 4.1 so they get escaped
      properly.

- mssql
    - Corrected handling of large decimal values with more robust
      tests. Removed string manipulation on floats. [ticket:1280]

    - Modified the do_begin handling in mssql to use the Cursor not
      the Connection so it is DBAPI compatible.

    - Corrected SAVEPOINT support on adodbapi by changing the
      handling of savepoint_release, which is unsupported on mssql.

0.5.0
========

- new features
- general
    - Documentation has been converted to Sphinx.  In particular,
      the generated API documentation has been constructed into a
      full blown "API Reference" section which organizes editorial
      documentation combined with generated docstrings.  Cross
      linking between sections and API docs are vastly improved, a
      javascript-powered search feature is provided, and a full
      index of all classes, functions and members is provided.

    - setup.py now imports setuptools only optionally.  If not
      present, distutils is used.  The new "pip" installer is
      recommended over easy_install as it installs in a more
      simplified way.

    - added an extremely basic illustration of a PostGIS integration
      to the examples folder.

- orm
    - Query.with_polymorphic() now accepts a third argument
      "discriminator" which will replace the value of
      mapper.polymorphic_on for that query.  Mappers themselves no
      longer require polymorphic_on to be set, even if the mapper
      has a polymorphic_identity.  When not set, the mapper will
      load non-polymorphically by default. Together, these two
      features allow a non-polymorphic concrete inheritance setup to
      use polymorphic loading on a per-query basis, since concrete
      setups are prone to many issues when used polymorphically in
      all cases.

    - dynamic_loader accepts a query_class= to customize the Query
      classes used for both the dynamic collection and the queries
      built from it.

    - query.order_by() accepts None which will remove any pending
      order_by state from the query, as well as cancel out any
      mapper/relation configured ordering. This is primarily useful
      for overriding the ordering specified on a dynamic_loader().
      [ticket:1079]

- sql
    - RowProxy objects can be used in place of dictionary arguments
      sent to connection.execute() and friends.  [ticket:935]

- dialect
    - Added a new description_encoding attribute on the dialect that
      is used for encoding the column name when processing the
      metadata. This usually defaults to utf-8.

- mssql
    - Added in a new MSGenericBinary type. This maps to the Binary
      type so it can implement the specialized behavior of treating
      length specified types as fixed-width Binary types and
      non-length types as an unbound variable length Binary type.

    - Added in new types: MSVarBinary and MSImage. [ticket:1249]

    - Added in the MSReal, MSNText, MSSmallDateTime, MSTime,
      MSDateTimeOffset, and MSDateTime2 types

- sqlite
    - Table reflection now stores the actual DefaultClause value for
      the column. [ticket:1266]

- bugfixes, behavioral changes
- general
- orm
    - Exceptions raised during compile_mappers() are now preserved
      to provide "sticky behavior" - if a hasattr() call on a
      pre-compiled mapped attribute triggers a failing compile and
      suppresses the exception, subsequent compilation is blocked
      and the exception will be reiterated on the next compile()
      call.  This issue occurs frequently when using declarative.

    - property.of_type() is now recognized on a single-table
      inheriting target, when used in the context of
      prop.of_type(..).any()/has(), as well as
      query.join(prop.of_type(...)).

    - query.join() raises an error when the target of the join
      doesn't match the property-based attribute - while it's
      unlikely anyone is doing this, the SQLAlchemy author was
      guilty of this particular loosey-goosey behavior.

    - Fixed bug when using weak_instance_map=False where modified
      events would not be intercepted for a flush(). [ticket:1272]

    - Fixed some deep "column correspondence" issues which could
      impact a Query made against a selectable containing multiple
      versions of the same table, as well as unions and similar
      which contained the same table columns in different column
      positions at different levels.  [ticket:1268]

    - Custom comparator classes used in conjunction with
      column_property(), relation() etc. can define new comparison
      methods on the Comparator, which will become available via
      __getattr__() on the InstrumentedAttribute.  In the case of
      synonym() or comparable_property(), attributes are resolved
      first on the user-defined descriptor, then on the user-defined
      comparator.

    - Added ScopedSession.is_active accessor. [ticket:976]

    - Can pass mapped attributes and column objects as keys to
      query.update({}).  [ticket:1262]

    - Mapped attributes passed to the values() of an expression
      level insert() or update() will use the keys of the mapped
      columns, not that of the mapped attribute.

    - Corrected problem with Query.delete() and Query.update() not
      working properly with bind parameters. [ticket:1242]

    - Query.select_from(), from_statement() ensure that the given
      argument is a FromClause, or Text/Select/Union, respectively.

    - Query() can be passed a "composite" attribute as a column
      expression and it will be expanded.  Somewhat related to
      [ticket:1253].

    - Query() is a little more robust when passed various column
      expressions such as strings, clauselists, text() constructs
      (which may mean it just raises an error more nicely).

    - first() works as expected with Query.from_statement().

    - Fixed bug introduced in 0.5rc4 involving eager loading not
      functioning for properties which were added to a mapper
      post-compile using add_property() or equivalent.

    - Fixed bug where many-to-many relation() with viewonly=True
      would not correctly reference the link between
      secondary->remote.

    - Duplicate items in a list-based collection will be maintained
      when issuing INSERTs to a "secondary" table in a many-to-many
      relation.  Assuming the m2m table has a unique or primary key
      constraint on it, this will raise the expected constraint
      violation instead of silently dropping the duplicate
      entries. Note that the old behavior remains for a one-to-many
      relation since collection entries in that case don't result in
      INSERT statements and SQLA doesn't manually police
      collections. [ticket:1232]

    - Query.add_column() can accept FromClause objects in the same
      manner as session.query() can.

    - Comparison of many-to-one relation to NULL is properly
      converted to IS NOT NULL based on not_().

    - Extra checks added to ensure explicit
      primaryjoin/secondaryjoin are ClauseElement instances, to
      prevent more confusing errors later on. [ticket:1087]

    - Improved mapper() check for non-class classes.  [ticket:1236]

    - comparator_factory argument is now documented and supported by
      all MapperProperty types, including column_property(),
      relation(), backref(), and synonym() [ticket:5051].

    - Changed the name of PropertyLoader to RelationProperty, to be
      consistent with all the other names.  PropertyLoader is still
      present as a synonym.

    - fixed "double iter()" call causing bus errors in shard API,
      removed errant result.close() left over from the 0.4
      version. [ticket:1099] [ticket:1228]

    - made Session.merge cascades not trigger autoflush.  Fixes
      merged instances getting prematurely inserted with missing
      values.

    - Two fixes to help prevent out-of-band columns from being
      rendered in polymorphic_union inheritance scenarios (which
      then causes extra tables to be rendered in the FROM clause
      causing cartesian products):

        - improvements to "column adaption" for a->b->c inheritance
          situations to better locate columns that are related to
          one another via multiple levels of indirection, rather
          than rendering the non-adapted column.

        - the "polymorphic discriminator" column is only rendered
          for the actual mapper being queried against. The column
          won't be "pulled in" from a subclass or superclass mapper
          since it's not needed.

    - Fixed shard_id argument on ShardedSession.execute().
      [ticket:1072]

- sql
    - Columns can again contain percent signs within their
      names. [ticket:1256]

    - sqlalchemy.sql.expression.Function is now a public class.  It
      can be subclassed to provide user-defined SQL functions in an
      imperative style, including with pre-established behaviors.
      The postgis.py example illustrates one usage of this.

    - PickleType now favors == comparison by default, if the
      incoming object (such as a dict) implements __eq__().  If the
      object does not implement __eq__() and mutable=True, a
      deprecation warning is raised.

    - Fixed the import weirdness in sqlalchemy.sql to not export
      __names__ [ticket:1215].

    - Using the same ForeignKey object repeatedly raises an error
      instead of silently failing later. [ticket:1238]

    - Added NotImplementedError for params() method on
      Insert/Update/Delete constructs.  These items currently don't
      support this functionality, which also would be a little
      misleading compared to values().

    - Reflected foreign keys will properly locate their referenced
      column, even if the column was given a "key" attribute
      different from the reflected name.  This is achieved via a new
      flag on ForeignKey/ForeignKeyConstraint called "link_to_name",
      if True means the given name is the referred-to column's name,
      not its assigned key.  [ticket:650]

    - select() can accept a ClauseList as a column in the same way
      as a Table or other selectable and the interior expressions
      will be used as column elements. [ticket:1253]

    - the "passive" flag on session.is_modified() is correctly
      propagated to the attribute manager.

    - union() and union_all() will not whack any order_by() that has
      been applied to the select()s inside.  If you union() a
      select() with order_by() (presumably to support LIMIT/OFFSET),
      you should also call self_group() on it to apply parenthesis.

- engine/pool

    - Connection.invalidate() checks for closed status to avoid
      attribute errors. [ticket:1246]

    - NullPool supports reconnect on failure behavior.
      [ticket:1094]

    - Added a mutex for the initial pool creation when using
      pool.manage(dbapi).  This prevents a minor case of "dogpile"
      behavior which would otherwise occur upon a heavy load
      startup.  [ticket:799]

    - _execute_clauseelement() goes back to being a private method.
      Subclassing Connection is not needed now that ConnectionProxy
      is available.

- documentation
    - Tickets [ticket:1200] [ticket:1149].

    - Added note about create_session() defaults.

    - Added section about metadata.reflect().

    - Updated `TypeDecorator` section.

    - Rewrote the "threadlocal" strategy section of the docs due to
      recent confusion over this feature.

    - Removed badly out of date 'polymorphic_fetch' and
      'select_table' docs from inheritance, reworked the second half
      of "joined table inheritance".

    - Documented `comparator_factory` kwarg, added new doc section
      "Custom Comparators".

- mssql
    - Refactored the Date/Time types. The ``smalldatetime`` data
      type no longer truncates to a date only, and will now be
      mapped to the MSSmallDateTime type. [ticket:1254]

    - Corrected an issue with Numerics to accept an int.

    - Mapped ``char_length`` to the ``LEN()`` function.

    - If an ``INSERT`` includes a subselect the ``INSERT`` is
      converted from an ``INSERT INTO VALUES`` construct to a
      ``INSERT INTO SELECT`` construct.

    - If the column is part of a ``primary_key`` it will be ``NOT
      NULL`` since MSSQL doesn't allow ``NULL`` in primary_key
      columns.

    - ``MSBinary`` now returns a ``BINARY`` instead of an
      ``IMAGE``. This is a backwards incompatible change in that
      ``BINARY`` is a fixed length data type whereas ``IMAGE`` is a
      variable length data type. [ticket:1249]

    - ``get_default_schema_name`` is now reflected from the database
      based on the user's default schema. This only works with MSSQL
      2005 and later. [ticket:1258]

    - Added collation support through the use of a new collation
      argument. This is supported on the following types: char,
      nchar, varchar, nvarchar, text, ntext. [ticket:1248]

    - Changes to the connection string parameters favor DSN as the
      default specification for pyodbc. See the mssql.py docstring
      for detailed usage instructions.

    - Added experimental support of savepoints. It currently does
      not work fully with sessions.

    - Support for three levels of column nullability: NULL, NOT
      NULL, and the database's configured default.  The default
      Column configuration (nullable=True) will now generate NULL in
      the DDL. Previously no specification was emitted and the
      database default would take effect (usually NULL, but not
      always).  To explicitly request the database default,
      configure columns with nullable=None and no specification will
      be emitted in DDL. This is backwards incompatible
      behavior. [ticket:1243]

- postgres
    - "%" signs in text() constructs are automatically escaped to
      "%%".  Because of the backwards incompatible nature of this
      change, a warning is emitted if '%%' is detected in the
      string.  [ticket:1267]

    - Calling alias.execute() in conjunction with
      server_side_cursors won't raise AttributeError.

    - Added Index reflection support to PostgreSQL, using a great
      patch we long neglected, submitted by Ken
      Kuhlman. [ticket:714]

- oracle
    - Adjusted the format of create_xid() to repair two-phase
      commit.  We now have field reports of Oracle two-phase commit
      working properly with this change.

    - Added OracleNVarchar type, produces NVARCHAR2, and also
      subclasses Unicode so that convert_unicode=True by default.
      NVARCHAR2 reflects into this type automatically so these
      columns pass unicode on a reflected table with no explicit
      convert_unicode=True flags.  [ticket:1233]

    - Fixed bug which was preventing out params of certain types
      from being received; thanks a ton to huddlej at wwu.edu !
      [ticket:1265]

- mysql
    - "%" signs in text() constructs are automatically escaped to
      "%%".  Because of the backwards incompatible nature of this
      change, a warning is emitted if '%%' is detected in the
      string.

    - Fixed bug in exception raise when FK columns not present
      during reflection. [ticket:1241]

    - Fixed bug involving reflection of a remote-schema table with a
      foreign key ref to another table in that schema.

- associationproxy
    - The association proxy properties are make themselves available
      at the class level, e.g. MyClass.aproxy.  Previously this
      evaluated to None.

- declarative
    - The full list of arguments accepted as string by backref()
      includes 'primaryjoin', 'secondaryjoin', 'secondary',
      'foreign_keys', 'remote_side', 'order_by'.

0.5.0rc4
========
- features
- orm
    - Query.count() has been enhanced to do the "right thing" in a
      wider variety of cases. It can now count multiple-entity
      queries, as well as column-based queries. Note that this means
      if you say query(A, B).count() without any joining criterion,
      it's going to count the cartesian product of A*B. Any query
      which is against column-based entities will automatically
      issue "SELECT count(1) FROM (SELECT...)" so that the real
      rowcount is returned, meaning a query such as
      query(func.count(A.name)).count() will return a value of one,
      since that query would return one row.

    - Lots of performance tuning.  A rough guesstimate over various
      ORM operations places it 10% faster over 0.5.0rc3, 25-30% over
      0.4.8.

- bugfixes and behavioral changes
- general:
    - global "propigate"->"propagate" change.

- orm
    - Adjustments to the enhanced garbage collection on
      InstanceState to better guard against errors due to lost
      state.

    - Query.get() returns a more informative error message when
      executed against multiple entities.  [ticket:1220]

    - Restored NotImplementedError on Cls.relation.in_()
      [ticket:1140] [ticket:1221]

    - Fixed PendingDeprecationWarning involving order_by parameter
      on relation(). [ticket:1226]

- sql
    - Removed the 'properties' attribute of the Connection object,
      Connection.info should be used.

    - Restored "active rowcount" fetch before ResultProxy autocloses
      the cursor.  This was removed in 0.5rc3.

    - Rearranged the `load_dialect_impl()` method in `TypeDecorator`
      such that it will take effect even if the user-defined
      `TypeDecorator` uses another `TypeDecorator` as its impl.

- access
    - Added support for Currency type.

    - Functions were not return their result. [ticket:1017]

    - Corrected problem with joins. Access only support LEFT OUTER
      or INNER not just JOIN by itself.  [ticket:1017]

- mssql
    - Lots of cleanup and fixes to correct problems with limit and
      offset.

    - Correct situation where subqueries as part of a binary
      expression need to be translated to use the IN and NOT IN
      syntax.

    - Fixed E Notation issue that prevented the ability to insert
      decimal values less than 1E-6. [ticket:1216]

    - Corrected problems with reflection when dealing with schemas,
      particularly when those schemas are the default
      schema. [ticket:1217]

    - Corrected problem with casting a zero length item to a
      varchar. It now correctly adjusts the CAST.

- ext
    - Can now use a custom "inherit_condition" in __mapper_args__
      when using declarative.

    - fixed string-based "remote_side", "order_by" and others not
      propagating correctly when used in backref().

0.5.0rc3
========
- features
- orm
    - Added two new hooks to SessionExtension: after_bulk_delete()
      and after_bulk_update().  after_bulk_delete() is called after
      a bulk delete() operation on a query. after_bulk_update() is
      called after a bulk update() operation on a query.

- sql
    - SQL compiler optimizations and complexity reduction. The call
      count for compiling a typical select() construct is 20% less
      versus 0.5.0rc2.

    - Dialects can now generate label names of adjustable
      length. Pass in the argument "label_length=<value>" to
      create_engine() to adjust how many characters max will be
      present in dynamically generated column labels, i.e.
      "somecolumn AS somelabel". Any value less than 6 will result
      in a label of minimal size, consisting of an underscore and a
      numeric counter. The compiler uses the value of
      dialect.max_identifier_length as a default.  [ticket:1211]

- ext
    - Added a new extension sqlalchemy.ext.serializer.  Provides
      Serializer/Deserializer "classes" which mirror
      Pickle/Unpickle, as well as dumps() and loads(). This
      serializer implements an "external object" pickler which keeps
      key context-sensitive objects, including engines, sessions,
      metadata, Tables/Columns, and mappers, outside of the pickle
      stream, and can later restore the pickle using any
      engine/metadata/session provider. This is used not for
      pickling regular object instances, which are pickleable
      without any special logic, but for pickling expression objects
      and full Query objects, such that all mapper/engine/session
      dependencies can be restored at unpickle time.

- oracle
    - Wrote a docstring for Oracle dialect. Apparently that Ohloh
      "few source code comments" label is starting to sting :).

    - Removed FIRST_ROWS() optimize flag when using LIMIT/OFFSET,
      can be reenabled with optimize_limits=True create_engine()
      flag.  [ticket:536]

- bugfixes and behavioral changes
- orm
    - "not equals" comparisons of simple many-to-one relation to an
      instance will not drop into an EXISTS clause and will compare
      foreign key columns instead.

    - Removed not-really-working use cases of comparing a collection
      to an iterable. Use contains() to test for collection
      membership.

    - Improved the behavior of aliased() objects such that they more
      accurately adapt the expressions generated, which helps
      particularly with self-referential comparisons. [ticket:1171]

    - Fixed bug involving primaryjoin/secondaryjoin conditions
      constructed from class-bound attributes (as often occurs when
      using declarative), which later would be inappropriately
      aliased by Query, particularly with the various EXISTS based
      comparators.

    - Fixed bug when using multiple query.join() with an
      aliased-bound descriptor which would lose the left alias.

    - Improved weakref identity map memory management to no longer
      require mutexing, resurrects garbage collected instance on a
      lazy basis for an InstanceState with pending changes.

    - InstanceState object now removes circular references to itself
      upon disposal to keep it outside of cyclic garbage collection.

    - relation() won't hide unrelated ForeignKey errors inside of
      the "please specify primaryjoin" message when determining join
      condition.

    - Fixed bug in Query involving order_by() in conjunction with
      multiple aliases of the same class (will add tests in
      [ticket:1218])

    - When using Query.join() with an explicit clause for the ON
      clause, the clause will be aliased in terms of the left side
      of the join, allowing scenarios like query(Source).
      from_self().join((Dest, Source.id==Dest.source_id)) to work
      properly.

    - polymorphic_union() function respects the "key" of each Column
      if they differ from the column's name.

    - Repaired support for "passive-deletes" on a many-to-one
      relation() with "delete" cascade.  [ticket:1183]

    - Fixed bug in composite types which prevented a primary-key
      composite type from being mutated [ticket:1213].

    - Added more granularity to internal attribute access, such that
      cascade and flush operations will not initialize unloaded
      attributes and collections, leaving them intact for a
      lazy-load later on. Backref events still initialize attrbutes
      and collections for pending instances.  [ticket:1202]

- sql
    - Simplified the check for ResultProxy "autoclose without
      results" to be based solely on presence of
      cursor.description. All the regexp-based guessing about
      statements returning rows has been removed [ticket:1212].

    - Direct execution of a union() construct will properly set up
      result-row processing.  [ticket:1194]

    - The internal notion of an "OID" or "ROWID" column has been
      removed. It's basically not used by any dialect, and the
      possibility of its usage with psycopg2's cursor.lastrowid is
      basically gone now that INSERT..RETURNING is available.

    - Removed "default_order_by()" method on all FromClause objects.

    - Repaired the table.tometadata() method so that a passed-in
      schema argument is propagated to ForeignKey constructs.

    - Slightly changed behavior of IN operator for comparing to
      empty collections. Now results in inequality comparison
      against self. More portable, but breaks with stored procedures
      that aren't pure functions.

- oracle
    - Setting the auto_convert_lobs to False on create_engine() will
      also instruct the OracleBinary type to return the cx_oracle
      LOB object unchanged.

- mysql
    - Fixed foreign key reflection in the edge case where a Table's
      explicit schema= is the same as the schema (database) the
      connection is attached to.

    - No longer expects include_columns in table reflection to be
      lower case.

- ext
    - Fixed bug preventing declarative-bound "column" objects from
      being used in column_mapped_collection(). [ticket:1174]

- misc
    - util.flatten_iterator() func doesn't interpret strings with
      __iter__() methods as iterators, such as in pypy
      [ticket:1077].

0.5.0rc2
========
- orm
    - Fixed bug involving read/write relation()s that contain
      literal or other non-column expressions within their
      primaryjoin condition equated to a foreign key column.

    - "non-batch" mode in mapper(), a feature which allows mapper
      extension methods to be called as each instance is
      updated/inserted, now honors the insert order of the objects
      given.

    - Fixed RLock-related bug in mapper which could deadlock upon
      reentrant mapper compile() calls, something that occurs when
      using declarative constructs inside of ForeignKey objects.

    - ScopedSession.query_property now accepts a query_cls factory,
      overriding the session's configured query_cls.

    - Fixed shared state bug interfering with ScopedSession.mapper's
      ability to apply default __init__ implementations on object
      subclasses.

    - Fixed up slices on Query (i.e. query[x:y]) to work properly
      for zero length slices, slices with None on either end.
      [ticket:1177]

    - Added an example illustrating Celko's "nested sets" as a 
      SQLA mapping.
    
    - contains_eager() with an alias argument works even when 
      the alias is embedded in a SELECT, as when sent to the
      Query via query.select_from().
      
    - contains_eager() usage is now compatible with a Query that
      also contains a regular eager load and limit/offset, in that
      the columns are added to the Query-generated subquery.
      [ticket:1180]
      
    - session.execute() will execute a Sequence object passed to
      it (regression from 0.4).
    
    - Removed the "raiseerror" keyword argument from object_mapper()
      and class_mapper().  These functions raise in all cases
      if the given class/instance is not mapped.

    - Fixed session.transaction.commit() on a autocommit=False
      session not starting a new transaction.
      
    - Some adjustments to Session.identity_map's weak referencing
      behavior to reduce asynchronous GC side effects.
    
    - Adjustment to Session's post-flush accounting of newly
      "clean" objects to better protect against operating on
      objects as they're asynchronously gc'ed. [ticket:1182]
    
- sql
    - column.in_(someselect) can now be used as a columns-clause
      expression without the subquery bleeding into the FROM clause
      [ticket:1074]
      
- sqlite
    - Overhauled SQLite date/time bind/result processing to use
      regular expressions and format strings, rather than
      strptime/strftime, to generically support pre-1900 dates,
      dates with microseconds.  [ticket:968]

    - String's (and Unicode's, UnicodeText's, etc.) convert_unicode 
      logic disabled in the sqlite dialect, to adjust for pysqlite 
      2.5.0's new requirement that only Python unicode objects are 
      accepted;
      http://itsystementwicklung.de/pipermail/list-pysqlite/2008-March/000018.html
      
- mysql
    - Temporary tables are now reflectable.

- oracle
    - Oracle will detect string-based statements which contain 
      comments at the front before a SELECT as SELECT statements.
      [ticket:1187]

0.5.0rc1
========

- orm
    - Query now has delete() and update(values) methods. This allows
      to perform bulk deletes/updates with the Query object.

    - The RowTuple object returned by Query(*cols) now features
      keynames which prefer mapped attribute names over column keys,
      column keys over column names, i.e.  Query(Class.foo,
      Class.bar) will have names "foo" and "bar" even if those are
      not the names of the underlying Column objects.  Direct Column
      objects such as Query(table.c.col) will return the "key"
      attribute of the Column.

    - Added scalar() and value() methods to Query, each return a
      single scalar value.  scalar() takes no arguments and is
      roughly equivalent to first()[0], value()
      takes a single column expression and is roughly equivalent to
      values(expr).next()[0].
      
    - Improved the determination of the FROM clause when placing SQL
      expressions in the query() list of entities.  In particular
      scalar subqueries should not "leak" their inner FROM objects
      out into the enclosing query.

    - Joins along a relation() from a mapped class to a mapped
      subclass, where the mapped subclass is configured with single
      table inheritance, will include an IN clause which limits the
      subtypes of the joined class to those requested, within the ON
      clause of the join.  This takes effect for eager load joins as
      well as query.join().  Note that in some scenarios the IN
      clause will appear in the WHERE clause of the query as well
      since this discrimination has multiple trigger points.

    - AttributeExtension has been refined such that the event
      is fired before the mutation actually occurs.  Additionally,
      the append() and set() methods must now return the given value,
      which is used as the value to be used in the mutation operation.
      This allows creation of validating AttributeListeners which
      raise before the action actually occurs, and which can change
      the given value into something else before its used.

    - column_property(), composite_property(), and relation() now 
      accept a single or list of AttributeExtensions using the 
      "extension" keyword argument.

    - query.order_by().get() silently drops the "ORDER BY" from 
      the query issued by GET but does not raise an exception.
      
    - Added a Validator AttributeExtension, as well as a 
      @validates decorator which is used in a similar fashion
      as @reconstructor, and marks a method as validating
      one or more mapped attributes.
      
    - class.someprop.in_() raises NotImplementedError pending the
      implementation of "in_" for relation [ticket:1140]

    - Fixed primary key update for many-to-many collections where
      the collection had not been loaded yet [ticket:1127]

    - Fixed bug whereby deferred() columns with a group in conjunction
      with an otherwise unrelated synonym() would produce 
      an AttributeError during deferred load.
      
    - The before_flush() hook on SessionExtension takes place before
      the list of new/dirty/deleted is calculated for the final
      time, allowing routines within before_flush() to further
      change the state of the Session before the flush proceeds.
      [ticket:1128]

    - The "extension" argument to Session and others can now
      optionally be a list, supporting events sent to multiple
      SessionExtension instances.  Session places SessionExtensions
      in Session.extensions.
      
    - Reentrant calls to flush() raise an error.  This also serves
      as a rudimentary, but not foolproof, check against concurrent
      calls to Session.flush().

    - Improved the behavior of query.join() when joining to
      joined-table inheritance subclasses, using explicit join
      criteria (i.e. not on a relation).

    - @orm.attributes.on_reconstitute and
      MapperExtension.on_reconstitute have been renamed to
      @orm.reconstructor and MapperExtension.reconstruct_instance

    - Fixed @reconstructor hook for subclasses which inherit from a
      base class.  [ticket:1129]

    - The composite() property type now supports a
      __set_composite_values__() method on the composite class which
      is required if the class represents state using attribute
      names other than the column's keynames; default-generated
      values now get populated properly upon flush.  Also,
      composites with attributes set to None compare correctly.
      [ticket:1132]

    - The 3-tuple of iterables returned by attributes.get_history()
      may now be a mix of lists and tuples.  (Previously members
      were always lists.)
      
    - Fixed bug whereby changing a primary key attribute on an 
      entity where the attribute's previous value had been expired 
      would produce an error upon flush(). [ticket:1151]
      
    - Fixed custom instrumentation bug whereby get_instance_dict()
      was not called for newly constructed instances not loaded
      by the ORM.

    - Session.delete() adds the given object to the session if 
      not already present.  This was a regression bug from 0.4.
      [ticket:1150]
      
    - The `echo_uow` flag on `Session` is deprecated, and unit-of-work
      logging is now application-level only, not per-session level.

    - Removed conflicting `contains()` operator from 
      `InstrumentedAttribute` which didn't accept `escape` kwaarg
      [ticket:1153].
      
- declarative
    - Fixed bug whereby mapper couldn't initialize if a composite
      primary key referenced another table that was not defined
      yet. [ticket:1161]
    
    - Fixed exception throw which would occur when string-based
      primaryjoin condition was used in conjunction with backref.
      
- schema
    - Added "sorted_tables" accessor to MetaData, which returns
      Table objects sorted in order of dependency as a list.
      This deprecates the MetaData.table_iterator() method.
      The "reverse=False" keyword argument has also been
      removed from util.sort_tables(); use the Python
      'reversed' function to reverse the results.
      [ticket:1033]

    - The 'length' argument to all Numeric types has been renamed
      to 'scale'.  'length' is deprecated and is still accepted
      with a warning.

    - Dropped 0.3-compatibility for user defined types
      (convert_result_value, convert_bind_param).

- sql
    - Temporarily rolled back the "ORDER BY" enhancement from
      [ticket:1068].  This feature is on hold pending further
      development.

    - The exists() construct won't "export" its contained list 
      of elements as FROM clauses, allowing them to be used more
      effectively in the columns clause of a SELECT.
      
    - and_() and or_() now generate a ColumnElement, allowing
      boolean expressions as result columns, i.e.
      select([and_(1, 0)]).  [ticket:798]
    
    - Bind params now subclass ColumnElement which allows them to be
      selectable by orm.query (they already had most ColumnElement
      semantics).
      
    - Added select_from() method to exists() construct, which becomes
      more and more compatible with a regular select().
      
    - Added func.min(), func.max(), func.sum() as "generic functions",
      which basically allows for their return type to be determined
      automatically.  Helps with dates on SQLite, decimal types, 
      others. [ticket:1160]
    
    - added decimal.Decimal as an "auto-detect" type; bind parameters
      and generic functions will set their type to Numeric when a 
      Decimal is used.
      
- mysql
    - The 'length' argument to MSInteger, MSBigInteger, MSTinyInteger,
      MSSmallInteger and MSYear has been renamed to 'display_width'.
      
    - Added MSMediumInteger type [ticket:1146].
    
    - the function func.utc_timestamp() compiles to UTC_TIMESTAMP, without
      the parenthesis, which seem to get in the way when using in 
      conjunction with executemany().

- oracle
    - limit/offset no longer uses ROW NUMBER OVER to limit rows,
      and instead uses subqueries in conjunction with a special
      Oracle optimization comment.  Allows LIMIT/OFFSET to work
      in conjunction with DISTINCT. [ticket:536]
    - has_sequence() now takes the current "schema" argument into
      account [ticket:1155]
    - added BFILE to reflected type names [ticket:1121]

0.5beta3
========

0.5beta3 includes all bugfixes listed under release "0.4.7".

- orm
    - The "entity_name" feature of SQLAlchemy mappers has been
      removed.  For rationale, see http://tinyurl.com/6nm2ne

    - the "autoexpire" flag on Session, sessionmaker(), and
      scoped_session() has been renamed to "expire_on_commit".  It
      does not affect the expiration behavior of rollback().

    - fixed endless loop bug which could occur within a mapper's
      deferred load of inherited attributes.

    - a legacy-support flag "_enable_transaction_accounting" flag
      added to Session which when False, disables all
      transaction-level object accounting, including expire on
      rollback, expire on commit, new/deleted list maintenance, and
      autoflush on begin.

    - The 'cascade' parameter to relation() accepts None as a value,
      which is equivalent to no cascades.

    - A critical fix to dynamic relations allows the "modified"
      history to be properly cleared after a flush().

    - user-defined @properties on a class are detected and left in
      place during mapper initialization.  This means that a
      table-bound column of the same name will not be mapped at all
      if a @property is in the way (and the column is not remapped
      to a different name), nor will an instrumented attribute from
      an inherited class be applied.  The same rules apply for names
      excluded using the include_properties/exclude_properties
      collections.

    - Added a new SessionExtension hook called after_attach().  This
      is called at the point of attachment for objects via add(),
      add_all(), delete(), and merge().

    - A mapper which inherits from another, when inheriting the
      columns of its inherited mapper, will use any reassigned
      property names specified in that inheriting mapper.
      Previously, if "Base" had reassigned "base_id" to the name
      "id", "SubBase(Base)" would still get an attribute called
      "base_id".  This could be worked around by explicitly stating
      the column in each submapper as well but this is fairly
      unworkable and also impossible when using declarative
      [ticket:1111].

    - Fixed a series of potential race conditions in Session whereby
      asynchronous GC could remove unmodified, no longer referenced
      items from the session as they were present in a list of items
      to be processed, typically during session.expunge_all() and
      dependent methods.

    - Some improvements to the _CompileOnAttr mechanism which should
      reduce the probability of "Attribute x was not replaced during
      compile" warnings. (this generally applies to SQLA hackers,
      like Elixir devs).

    - Fixed bug whereby the "unsaved, pending instance" FlushError
      raised for a pending orphan would not take superclass mappers
      into account when generating the list of relations responsible
      for the error.

- sql
    - func.count() with no arguments renders as COUNT(*), equivalent
      to func.count(text('*')).

    - simple label names in ORDER BY expressions render as
      themselves, and not as a re-statement of their corresponding
      expression.  This feature is currently enabled only for
      SQLite, MySQL, and PostgreSQL.  It can be enabled on other
      dialects as each is shown to support this
      behavior. [ticket:1068]

- ext
    - Class-bound attributes sent as arguments to relation()'s
      remote_side and foreign_keys parameters are now accepted,
      allowing them to be used with declarative.  Additionally fixed
      bugs involving order_by being specified as a class-bound
      attribute in conjunction with eager loading.

    - declarative initialization of Columns adjusted so that
      non-renamed columns initialize in the same way as a non
      declarative mapper.  This allows an inheriting mapper to set
      up its same-named "id" columns in particular such that the
      parent "id" column is favored over the child column, reducing
      database round trips when this value is requested.

- mysql
    - Quoting of MSEnum values for use in CREATE TABLE is now
      optional & will be quoted on demand as required.  (Quoting was
      always optional for use with existing tables.) [ticket:1110]

0.5beta2
========

0.5beta2 includes some of the bugfixes listed under release "0.4.7".

- orm
    - In addition to expired attributes, deferred attributes also
      load if their data is present in the result set.  [ticket:870]

    - session.refresh() raises an informative error message if the
      list of attributes does not include any column-based
      attributes.

    - query() raises an informative error message if no columns or
      mappers are specified.

    - lazy loaders now trigger autoflush before proceeding.  This
      allows expire() of a collection or scalar relation to function
      properly in the context of autoflush.

    - column_property() attributes which represent SQL expressions
      or columns that are not present in the mapped tables (such as
      those from views) are automatically expired after an INSERT or
      UPDATE, assuming they have not been locally modified, so that
      they are refreshed with the most recent data upon access.
      [ticket:887]

    - Fixed explicit, self-referential joins between two
      joined-table inheritance mappers when using query.join(cls,
      aliased=True).  [ticket:1082]

    - Fixed query.join() when used in conjunction with a
      columns-only clause and an SQL-expression ON clause in the
      join.

    - The "allow_column_override" flag from mapper() has been
      removed.  This flag is virtually always misunderstood.  Its
      specific functionality is available via the
      include_properties/exclude_properties mapper arguments.

    - Repaired `__str__()` method on Query. [ticket:1066]

    - Session.bind gets used as a default even when table/mapper
      specific binds are defined.

- schema
    - Added prefixes option to `Table` that accepts a list of
      strings to insert after CREATE in the CREATE TABLE statement.
      [ticket:1075]

    - Unicode, UnicodeText types now set "assert_unicode" and
      "convert_unicode" by default, but accept overriding
      **kwargs for these values.

- sql
    - Added new match() operator that performs a full-text search.
      Supported on PostgreSQL, SQLite, MySQL, MS-SQL, and Oracle
      backends.

- sqlite
    - Modified SQLite's representation of "microseconds" to match
      the output of str(somedatetime), i.e. in that the microseconds
      are represented as fractional seconds in string format.  This
      makes SQLA's SQLite date type compatible with datetimes that
      were saved directly using Pysqlite (which just calls str()).
      Note that this is incompatible with the existing microseconds
      values in a SQLA 0.4 generated SQLite database file.

      To get the old behavior globally:

           from sqlalchemy.databases.sqlite import DateTimeMixin
           DateTimeMixin.__legacy_microseconds__ = True

      To get the behavior on individual DateTime types:

            t = sqlite.SLDateTime()
            t.__legacy_microseconds__ = True

      Then use "t" as the type on the Column.

      [ticket:1090]

    - SQLite Date, DateTime, and Time types only accept Python
      datetime objects now, not strings.  If you'd like to format
      dates as strings yourself with SQLite, use a String type.  If
      you'd like them to return datetime objects anyway despite
      their accepting strings as input, make a TypeDecorator around
      String - SQLA doesn't encourage this pattern.

- extensions
    - Declarative supports a __table_args__ class variable, which is
      either a dictionary, or tuple of the form (arg1, arg2, ...,
      {kwarg1:value, ...}) which contains positional + kw arguments
      to be passed to the Table constructor. [ticket:1096]

0.5beta1
========

An ongoing document describing the changes from 0.4 to 0.5 is at:
http://www.sqlalchemy.org/trac/wiki/05Migration

For this section, the list below primarily lists changes within the
attribute instrumentation API and is only a small fraction of the
full changes between 0.4/0.5.

-orm
    - The "__init__" trigger/decorator added by mapper now attempts
      to exactly mirror the argument signature of the original
      __init__.  The pass-through for '_sa_session' is no longer
      implicit- you must allow for this keyword argument in your
      constructor.

    - ClassState is renamed to ClassManager.

    - Classes may supply their own InstrumentationManager by
      providing a __sa_instrumentation_manager__ property.

    - Custom instrumentation may use any mechanism to associate a
      ClassManager with a class and an InstanceState with an
      instance.  Attributes on those objects are still the default
      association mechanism used by SQLAlchemy's native
      instrumentation.

    - Moved entity_name, _sa_session_id, and _instance_key from the
      instance object to the instance state.  These values are still
      available in the old way, which is now deprecated, using
      descriptors attached to the class.  A deprecation warning will
      be issued when accessed.

    - The _prepare_instrumentation alias for prepare_instrumentation
      has been removed.

    - sqlalchemy.exceptions has been renamed to sqlalchemy.exc.  The
      module may be imported under either name.

    - ORM-related exceptions are now defined in sqlalchemy.orm.exc.
      ConcurrentModificationError, FlushError, and
      UnmappedColumnError compatibility aliases are installed in
      sqlalchemy.exc during the import of sqlalchemy.orm.

    - sqlalchemy.logging has been renamed to sqlalchemy.log.

    - The transitional sqlalchemy.log.SADeprecationWarning alias for
      the warning's definition in sqlalchemy.exc has been removed.

    - exc.AssertionError has been removed and usage replaced with
      Python's built-in AssertionError.

    - The behavior of MapperExtensions attached to multiple,
      entity_name= primary mappers for a single class has been
      altered.  The first mapper() defined for a class is the only
      mapper eligible for the MapperExtension 'instrument_class',
      'init_instance' and 'init_failed' events.  This is backwards
      incompatible; previously the extensions of last mapper defined
      would receive these events.

- firebird
    - Added support for returning values from inserts (2.0+ only),
      updates and deletes (2.1+ only).

For changes prior to 0.5, see CHANGES_PRE_05

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