Mike Bayer  committed efd2631

back-merged current 0.4 trunk into rel_0_4 branch, which will become the 0.4 maintenance branch

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+- orm
+    - A fix to the recent relation() refactoring which fixes
+      exotic viewonly relations which join between local and
+      remote table multiple times, with a common column shared
+      between the joins.
+    - Also re-established viewonly relation() configurations
+      that join across multiple tables.
+    - contains_eager(), the hot function of the week, suppresses
+      the eager loader's own generation of the LEFT OUTER JOIN,
+      so that it is reasonable to use any Query, not just those
+      which use from_statement().  
+    - Added an experimental relation() flag to help with
+      primaryjoins across functions, etc.,
+      _local_remote_pairs=[tuples].  This complements a complex
+      primaryjoin condition allowing you to provide the
+      individual column pairs which comprise the relation's
+      local and remote sides.  Also improved lazy load SQL
+      generation to handle placing bind params inside of
+      functions and other expressions.  (partial progress
+      towards [ticket:610])
+    - Fixed "concatenate tuple" bug which could occur with
+      Query.order_by() if clause adaption had taken place.
+      [ticket:1027]
+    - Removed an ancient assertion that mapped selectables
+      require "alias names" - the mapper creates its own alias
+      now if none is present.  Though in this case you need to
+      use the class, not the mapped selectable, as the source of
+      column attributes - so a warning is still issued.
+    - Fixes to the "exists" function involving inheritance
+      (any(), has(), ~contains()); the full target join will be
+      rendered into the EXISTS clause for relations that link to
+      subclasses.
+    - Restored usage of append_result() extension method for
+      primary query rows, when the extension is present and only
+      a single- entity result is being returned.
+    - Fixed Class.collection==None for m2m relationships
+      [ticket:4213]
+    - Refined mapper._save_obj() which was unnecessarily calling
+      __ne__() on scalar values during flush [ticket:1015]
+    - Added a feature to eager loading whereby subqueries set as
+      column_property() with explicit label names (which is not
+      necessary, btw) will have the label anonymized when the
+      instance is part of the eager join, to prevent conflicts
+      with a subquery or column of the same name on the parent
+      object.  [ticket:1019]
+    - Same as [ticket:1019] but repaired the non-labeled use
+      case [ticket:1022]
+    - Adjusted class-member inspection during attribute and
+      collection instrumentation that could be problematic when
+      integrating with other frameworks.
+    - Fixed duplicate append event emission on repeated
+      instrumented set.add() operations.
+    - set-based collections |=, -=, ^= and &= are stricter about
+      their operands and only operate on sets, frozensets or
+      subclasses of the collection type. Previously, they would
+      accept any duck-typed set.
+    - added an example dynamic_dict/, illustrating
+      a simple way to place dictionary behavior on top of 
+      a dynamic_loader.
+- sql
+    - Added COLLATE support via the .collate(<collation>)
+      expression operator and collate(<expr>, <collation>) sql
+      function.
+    - Fixed bug with union() when applied to non-Table connected
+      select statements
+    - Improved behavior of text() expressions when used as FROM
+      clauses, such as select().select_from(text("sometext"))
+      [ticket:1014]
+    - Column.copy() respects the value of "autoincrement", fixes
+      usage with Migrate [ticket:1021]
+- engines
+    - Pool listeners can now be provided as a dictionary of
+      callables or a (possibly partial) duck-type of
+      PoolListener, your choice.
+    - Added "reset_on_return" option to Pool which will disable
+      the database state cleanup step (e.g. issuing a
+      rollback()) when connections are returned to the pool.
+    - set-based association proxies |=, -=, ^= and &= are
+      stricter about their operands and only operate on sets,
+      frozensets or other association proxies. Previously, they
+      would accept any duck-typed set.
+- declarative extension
+    - Joined table inheritance mappers use a slightly relaxed
+      function to create the "inherit condition" to the parent
+      table, so that other foreign keys to not-yet-declared
+      Table objects don't trigger an error.
+    - Fixed re-entrant mapper compile hang when a declared
+      attribute is used within ForeignKey,
+      i.e. ForeignKey(MyOtherClass.someattribute)
+- mssql
+    - Added "odbc_autotranslate" parameter to engine / dburi
+      parameters. Any given string will be passed through to the
+      ODBC connection string as:
+            "AutoTranslate=%s" % odbc_autotranslate
+      [ticket:1005]
+    - Added "odbc_options" parameter to engine / dburi
+      parameters. The given string is simply appended to the
+      SQLAlchemy-generated odbc connection string.
+      This should obviate the need of adding a myriad of ODBC
+      options in the future.
+- firebird
+    - Handle the "SUBSTRING(:string FROM :start FOR :length)"
+      builtin.
+- orm
+    - A small change in behavior to session.merge() - existing
+      objects are checked for based on primary key attributes, not
+      necessarily _instance_key.  So the widely requested
+      capability, that:
+            x = MyObject(id=1)
+            x = sess.merge(x)
+      will in fact load MyObject with id #1 from the database if
+      present, is now available.  merge() still copies the state
+      of the given object to the persistent one, so an example
+      like the above would typically have copied "None" from all
+      attributes of "x" onto the persistent copy.  These can be
+      reverted using session.expire(x).
+    - Also fixed behavior in merge() whereby collection elements
+      present on the destination but not the merged collection
+      were not being removed from the destination.
+    - Added a more aggressive check for "uncompiled mappers",
+      helps particularly with declarative layer [ticket:995]
+    - The methodology behind "primaryjoin"/"secondaryjoin" has
+      been refactored.  Behavior should be slightly more
+      intelligent, primarily in terms of error messages which
+      have been pared down to be more readable.  In a slight
+      number of scenarios it can better resolve the correct
+      foreign key than before.
+    - Added comparable_property(), adds query Comparator
+      behavior to regular, unmanaged Python properties
+    - The functionality of query.with_polymorphic() has been
+      added to mapper() as a configuration option.
+      It's set via several forms:
+            with_polymorphic='*'
+            with_polymorphic=[mappers]
+            with_polymorphic=('*', selectable)
+            with_polymorphic=([mappers], selectable)
+      This controls the default polymorphic loading strategy for
+      inherited mappers. When a selectable is not given, outer
+      joins are created for all joined-table inheriting mappers
+      requested. Note that the auto-create of joins is not
+      compatible with concrete table inheritance.
+      The existing select_table flag on mapper() is now
+      deprecated and is synonymous with:
+        with_polymorphic('*', select_table).
+      Note that the underlying "guts" of select_table have been
+      completely removed and replaced with the newer, more
+      flexible approach.
+      The new approach also automatically allows eager loads to
+      work for subclasses, if they are present, for example
+        sess.query(Company).options(
+         eagerload_all(
+          [Company.employees.of_type(Engineer), 'machines']
+        ))
+      to load Company objects, their employees, and the
+      'machines' collection of employees who happen to be
+      Engineers. A "with_polymorphic" Query option should be
+      introduced soon as well which would allow per-Query
+      control of with_polymorphic() on relations.
+    - Added two "experimental" features to Query, "experimental"
+      in that their specific name/behavior is not carved in
+      stone just yet: _values() and _from_self().  We'd like
+      feedback on these.
+      - _values(*columns) is given a list of column expressions,
+        and returns a new Query that only returns those
+        columns. When evaluated, the return value is a list of
+        tuples just like when using add_column() or
+        add_entity(), the only difference is that "entity zero",
+        i.e. the mapped class, is not included in the
+        results. This means it finally makes sense to use
+        group_by() and having() on Query, which have been
+        sitting around uselessly until now.
+        A future change to this method may include that its
+        ability to join, filter and allow other options not
+        related to a "resultset" are removed, so the feedback
+        we're looking for is how people want to use
+        _values()...i.e. at the very end, or do people prefer to
+        continue generating after it's called.
+      - _from_self() compiles the SELECT statement for the Query
+        (minus any eager loaders), and returns a new Query that
+        selects from that SELECT. So basically you can query
+        from a Query without needing to extract the SELECT
+        statement manually. This gives meaning to operations
+        like query[3:5]._from_self().filter(some
+        criterion). There's not much controversial here except
+        that you can quickly create highly nested queries that
+        are less efficient, and we want feedback on the naming
+        choice.
+    - query.order_by() and query.group_by() will accept multiple
+      arguments using *args (like select() already does).
+    - Added some convenience descriptors to Query:
+      query.statement returns the full SELECT construct,
+      query.whereclause returns just the WHERE part of the
+      SELECT construct.
+    - Fixed/covered case when using a False/0 value as a
+      polymorphic discriminator.
+    - Fixed bug which was preventing synonym() attributes from
+      being used with inheritance
+    - Fixed SQL function truncation of trailing underscores
+      [ticket:996]
+    - When attributes are expired on a pending instance, an
+      error will not be raised when the "refresh" action is
+      triggered and no result is found.
+    - Session.execute can now find binds from metadata
+    - Adjusted the definition of "self-referential" to be any
+      two mappers with a common parent (this affects whether or
+      not aliased=True is required when joining with Query).
+    - Made some fixes to the "from_joinpoint" argument to
+      query.join() so that if the previous join was aliased and
+      this one isn't, the join still happens successfully.
+    - Assorted "cascade deletes" fixes:
+        - Fixed "cascade delete" operation of dynamic relations,
+          which had only been implemented for foreign-key
+          nulling behavior in 0.4.2 and not actual cascading
+          deletes [ticket:895]
+        - Delete cascade without delete-orphan cascade on a
+          many-to-one will not delete orphans which were
+          disconnected from the parent before session.delete()
+          is called on the parent (one-to-many already had
+          this).
+        - Delete cascade with delete-orphan will delete orphans
+          whether or not it remains attached to its also-deleted
+          parent.
+        - delete-orphan casacde is properly detected on
+          relations that are present on superclasses when using
+          inheritance.
+    - Fixed order_by calculation in Query to properly alias
+      mapper-config'ed order_by when using select_from()
+    - Refactored the diffing logic that kicks in when replacing
+      one collection with another into collections.bulk_replace,
+      useful to anyone building multi-level collections.
+    - Cascade traversal algorithm converted from recursive to
+      iterative to support deep object graphs.
+- sql
+    - Schema-qualified tables now will place the schemaname
+      ahead of the tablename in all column expressions as well
+      as when generating column labels.  This prevents cross-
+      schema name collisions in all cases [ticket:999]
+    - Can now allow selects which correlate all FROM clauses and
+      have no FROM themselves.  These are typically used in a
+      scalar context, i.e. SELECT x, (SELECT x WHERE y) FROM
+      table.  Requires explicit correlate() call.
+    - 'name' is no longer a required constructor argument for
+      Column().  It (and .key) may now be deferred until the
+      column is added to a Table.
+    - like(), ilike(), contains(), startswith(), endswith() take
+      an optional keyword argument "escape=<somestring>", which
+      is set as the escape character using the syntax "x LIKE y
+      ESCAPE '<somestring>'" [ticket:993], [ticket:791]
+    - random() is now a generic sql function and will compile to
+      the database's random implementation, if any.
+    - update().values() and insert().values() take keyword
+      arguments.
+    - Fixed an issue in select() regarding its generation of
+      FROM clauses, in rare circumstances two clauses could be
+      produced when one was intended to cancel out the other.
+      Some ORM queries with lots of eager loads might have seen
+      this symptom.
+    - The case() function now also takes a dictionary as its
+      whens parameter.  It also interprets the "THEN"
+      expressions as values by default, meaning case([(x==y,
+      "foo")]) will interpret "foo" as a bound value, not a SQL
+      expression.  use text(expr) for literal SQL expressions in
+      this case.  For the criterion itself, these may be literal
+      strings only if the "value" keyword is present, otherwise
+      SA will force explicit usage of either text() or
+      literal().
+- declarative extension
+    - The "synonym" function is now directly usable with
+      "declarative".  Pass in the decorated property using the
+      "descriptor" keyword argument, e.g.: somekey =
+      synonym('_somekey', descriptor=property(g, s))
+    - The "deferred" function is usable with "declarative".
+      Simplest usage is to declare deferred and Column together,
+      e.g.: data = deferred(Column(Text))
+    - Declarative also gained @synonym_for(...) and
+      @comparable_using(...), front-ends for synonym and
+      comparable_property.
+    - Improvements to mapper compilation when using declarative;
+      already-compiled mappers will still trigger compiles of
+      other uncompiled mappers when used [ticket:995]
+    - Declarative will complete setup for Columns lacking names,
+      allows a more DRY syntax.
+        class Foo(Base):
+            __tablename__ = 'foos'
+            id = Column(Integer, primary_key=True)
+     - inheritance in declarative can be disabled when sending
+       "inherits=None" to __mapper_args__.
+     - declarative_base() takes optional kwarg "mapper", which
+       is any callable/class/method that produces a mapper, such
+       as declarative_base(mapper=scopedsession.mapper).  This
+       property can also be set on individual declarative
+       classes using the "__mapper_cls__" property.
+- postgres
+    - Got PG server side cursors back into shape, added fixed
+      unit tests as part of the default test suite.  Added
+      better uniqueness to the cursor ID [ticket:1001]
+- oracle
+    - The "owner" keyword on Table is now deprecated, and is
+      exactly synonymous with the "schema" keyword.  Tables can
+      now be reflected with alternate "owner" attributes,
+      explicitly stated on the Table object or not using
+      "schema".
+    - All of the "magic" searching for synonyms, DBLINKs etc.
+      during table reflection are disabled by default unless you
+      specify "oracle_resolve_synonyms=True" on the Table
+      object.  Resolving synonyms necessarily leads to some
+      messy guessing which we'd rather leave off by default.
+      When the flag is set, tables and related tables will be
+      resolved against synonyms in all cases, meaning if a
+      synonym exists for a particular table, reflection will use
+      it when reflecting related tables.  This is stickier
+      behavior than before which is why it's off by default.
+- mssql
+     - Reflected tables will now automatically load other tables
+       which are referenced by Foreign keys in the auto-loaded
+       table, [ticket:979].
+     - Added executemany check to skip identity fetch,
+       [ticket:916].
+     - Added stubs for small date type, [ticket:884]
+     - Added a new 'driver' keyword parameter for the pyodbc
+       dialect.  Will substitute into the ODBC connection string
+       if given, defaults to 'SQL Server'.
+     - Added a new 'max_identifier_length' keyword parameter for
+       the pyodbc dialect.
+     - Improvements to pyodbc + Unix. If you couldn't get that
+       combination to work before, please try again.
+- mysql
+     - The keys the dialect uses to cache server
+       settings have changed and are now namespaced.
+- sql
+    - Can again create aliases of selects against textual FROM
+      clauses, [ticket:975]
+    - The value of a bindparam() can be a callable, in which
+      case it's evaluated at statement execution time to get the
+      value.
+    - Added exception wrapping/reconnect support to result set
+      fetching.  Reconnect works for those databases that raise
+      a catchable data error during results (i.e. doesn't work
+      on MySQL) [ticket:978]
+    - Implemented two-phase API for "threadlocal" engine, via
+      engine.begin_twophase(), engine.prepare() [ticket:936]
+    - Fixed bug which was preventing UNIONS from being
+      cloneable, [ticket:986]
+    - Added "bind" keyword argument to insert(), update(),
+      delete() and DDL(). The .bind property is now assignable
+      on those statements as well as on select().
+    - Insert statements can now be compiled with extra "prefix"
+      words between INSERT and INTO, for vendor extensions like
+      MySQL's INSERT IGNORE INTO table.
+- orm
+    - any(), has(), contains(), ~contains(), attribute level ==
+      and != now work properly with self-referential relations -
+      the clause inside the EXISTS is aliased on the "remote"
+      side to distinguish it from the parent table.  This
+      applies to single table self-referential as well as
+      inheritance-based self-referential.
+    - Repaired behavior of == and != operators at the relation()
+      level when compared against NULL for one-to-one relations
+      [ticket:985]
+    - Fixed bug whereby session.expire() attributes were not
+      loading on an polymorphically-mapped instance mapped by a
+      select_table mapper.
+    - Added query.with_polymorphic() - specifies a list of
+      classes which descend from the base class, which will be
+      added to the FROM clause of the query.  Allows subclasses
+      to be used within filter() criterion as well as eagerly
+      loads the attributes of those subclasses.
+    - Your cries have been heard: removing a pending item from
+      an attribute or collection with delete-orphan expunges the
+      item from the session; no FlushError is raised.  Note that
+      if you'ed the pending item explicitly, the
+      attribute/collection removal still knocks it out.
+    - session.refresh() and session.expire() raise an error when
+      called on instances which are not persistent within the
+      session
+    - Fixed potential generative bug when the same Query was
+      used to generate multiple Query objects using join().
+    - Fixed bug which was introduced in 0.4.3, whereby loading
+      an already-persistent instance mapped with joined table
+      inheritance would trigger a useless "secondary" load from
+      its joined table, when using the default "select"
+      polymorphic_fetch.  This was due to attributes being
+      marked as expired during its first load and not getting
+      unmarked from the previous "secondary" load.  Attributes
+      are now unexpired based on presence in __dict__ after any
+      load or commit operation succeeds.
+    - Deprecated Query methods apply_sum(), apply_max(),
+      apply_min(), apply_avg().  Better methodologies are
+      coming....
+    - relation() can accept a callable for its first argument,
+      which returns the class to be related.  This is in place
+      to assist declarative packages to define relations without
+      classes yet being in place.
+    - Added a new "higher level" operator called "of_type()":
+      used in join() as well as with any() and has(), qualifies
+      the subclass which will be used in filter criterion, e.g.:
+        query.filter(Company.employees.of_type(Engineer).
+          any('foo'))
+        or
+        query.join(Company.employees.of_type(Engineer)).
+          filter('foo')
+    - Preventive code against a potential lost-reference bug in
+      flush().
+    - Expressions used in filter(), filter_by() and others, when
+      they make usage of a clause generated from a relation
+      using the identity of a child object (e.g.,
+      filter(Parent.child==<somechild>)), evaluate the actual
+      primary key value of <somechild> at execution time so that
+      the autoflush step of the Query can complete, thereby
+      populating the PK value of <somechild> in the case that
+      <somechild> was pending.
+    - setting the relation()-level order by to a column in the
+      many-to-many "secondary" table will now work with eager
+      loading, previously the "order by" wasn't aliased against
+      the secondary table's alias.
+    - Synonyms riding on top of existing descriptors are now
+      full proxies to those descriptors.
+- dialects
+    - Invalid SQLite connection URLs now raise an error.
+    - postgres TIMESTAMP renders correctly [ticket:981]
+    - postgres PGArray is a "mutable" type by default; when used
+      with the ORM, mutable-style equality/ copy-on-write
+      techniques are used to test for changes.
+- extensions
+    - a new super-small "declarative" extension has been added,
+      which allows Table and mapper() configuration to take
+      place inline underneath a class declaration.  This
+      extension differs from ActiveMapper and Elixir in that it
+      does not redefine any SQLAlchemy semantics at all; literal
+      Column, Table and relation() constructs are used to define
+      the class behavior and table definition.
+- sql
+    - Added "schema.DDL", an executable free-form DDL statement.
+      DDLs can be executed in isolation or attached to Table or
+      MetaData instances and executed automatically when those
+      objects are created and/or dropped.
+    - Table columns and constraints can be overridden on a an
+      existing table (such as a table that was already reflected)
+      using the 'useexisting=True' flag, which now takes into
+      account the arguments passed along with it.
+    - Added a callable-based DDL events interface, adds hooks
+      before and after Tables and MetaData create and drop.
+    - Added generative where(<criterion>) method to delete() and
+      update() constructs which return a new object with criterion
+      joined to existing criterion via AND, just like
+      select().where().
+    - Added "ilike()" operator to column operations.  Compiles to
+      ILIKE on postgres, lower(x) LIKE lower(y) on all
+      others. [ticket:727]
+    - Added "now()" as a generic function; on SQLite, Oracle
+      and MSSQL compiles as "CURRENT_TIMESTAMP"; "now()" on
+      all others. [ticket:943]
+    - The startswith(), endswith(), and contains() operators now
+      concatenate the wildcard operator with the given operand in
+      SQL, i.e. "'%' || <bindparam>" in all cases, accept
+      text('something') operands properly [ticket:962]
+    - cast() accepts text('something') and other non-literal
+      operands properly [ticket:962]
+    - fixed bug in result proxy where anonymously generated
+      column labels would not be accessible using their straight
+      string name
+    - Deferrable constraints can now be defined.
+    - Added "autocommit=True" keyword argument to select() and
+      text(), as well as generative autocommit() method on
+      select(); for statements which modify the database through
+      some user-defined means other than the usual INSERT/UPDATE/
+      DELETE etc.  This flag will enable "autocommit" behavior
+      during execution if no transaction is in progress.
+      [ticket:915]
+    - The '.c.' attribute on a selectable now gets an entry for
+      every column expression in its columns clause.  Previously,
+      "unnamed" columns like functions and CASE statements weren't
+      getting put there.  Now they will, using their full string
+      representation if no 'name' is available.
+    - a CompositeSelect, i.e. any union(), union_all(),
+      intersect(), etc. now asserts that each selectable contains
+      the same number of columns.  This conforms to the
+      corresponding SQL requirement.
+    - The anonymous 'label' generated for otherwise unlabeled
+      functions and expressions now propagates outwards at compile
+      time for expressions like select([select([])]).
+    - Building on the above ideas, CompositeSelects now build up
+      their ".c." collection based on the names present in the
+      first selectable only; corresponding_column() now works
+      fully for all embedded selectables.
+    - Oracle and others properly encode SQL used for defaults like
+      sequences, etc., even if no unicode idents are used since
+      identifier preparer may return a cached unicode identifier.
+    - Column and clause comparisons to datetime objects on the
+      left hand side of the expression now work (d < table.c.col).
+      (datetimes on the RHS have always worked, the LHS exception
+      is a quirk of the datetime implementation.)
+- orm
+    - Every Session.begin() must now be accompanied by a
+      corresponding commit() or rollback() unless the session is
+      closed with Session.close().  This also includes the begin()
+      which is implicit to a session created with
+      transactional=True.  The biggest change introduced here is
+      that when a Session created with transactional=True raises
+      an exception during flush(), you must call
+      Session.rollback() or Session.close() in order for that
+      Session to continue after an exception.
+    - Fixed merge() collection-doubling bug when merging transient
+      entities with backref'ed collections.  [ticket:961]
+    - merge(dont_load=True) does not accept transient entities,
+      this is in continuation with the fact that
+      merge(dont_load=True) does not accept any "dirty" objects
+      either.
+    - Added standalone "query" class attribute generated by a
+      scoped_session.  This provides MyClass.query without using
+      Session.mapper.  Use via:
+        MyClass.query = Session.query_property()
+    - The proper error message is raised when trying to access
+      expired instance attributes with no session present
+    - dynamic_loader() / lazy="dynamic" now accepts and uses
+      the order_by parameter in the same way in which it works
+      with relation().
+    - Added expire_all() method to Session.  Calls expire() for
+      all persistent instances.  This is handy in conjunction
+      with...
+    - Instances which have been partially or fully expired will
+      have their expired attributes populated during a regular
+      Query operation which affects those objects, preventing a
+      needless second SQL statement for each instance.
+    - Dynamic relations, when referenced, create a strong
+      reference to the parent object so that the query still has a
+      parent to call against even if the parent is only created
+      (and otherwise dereferenced) within the scope of a single
+      expression. [ticket:938]
+    - Added a mapper() flag "eager_defaults". When set to True,
+      defaults that are generated during an INSERT or UPDATE
+      operation are post-fetched immediately, instead of being
+      deferred until later.  This mimics the old 0.3 behavior.
+    - query.join() can now accept class-mapped attributes as
+      arguments. These can be used in place or in any combination
+      with strings.  In particular this allows construction of
+      joins to subclasses on a polymorphic relation, i.e.:
+        query(Company).join(['employees',])
+    - query.join() can also accept tuples of attribute name/some
+      selectable as arguments.  This allows construction of joins
+      *from* subclasses of a polymorphic relation, i.e.:
+        query(Company).\
+        join(
+          [('employees', people.join(engineer)),]
+        )
+    - General improvements to the behavior of join() in
+      conjunction with polymorphic mappers, i.e. joining from/to
+      polymorphic mappers and properly applying aliases.
+    - Fixed/improved behavior when a mapper determines the natural
+      "primary key" of a mapped join, it will more effectively
+      reduce columns which are equivalent via foreign key
+      relation.  This affects how many arguments need to be sent
+      to query.get(), among other things.  [ticket:933]
+    - The lazy loader can now handle a join condition where the
+      "bound" column (i.e. the one that gets the parent id sent as
+      a bind parameter) appears more than once in the join
+      condition.  Specifically this allows the common task of a
+      relation() which contains a parent-correlated subquery, such
+      as "select only the most recent child item". [ticket:946]
+    - Fixed bug in polymorphic inheritance where an incorrect
+      exception is raised when base polymorphic_on column does not
+      correspond to any columns within the local selectable of an
+      inheriting mapper more than one level deep
+    - Fixed bug in polymorphic inheritance which made it difficult
+      to set a working "order_by" on a polymorphic mapper.
+    - Fixed a rather expensive call in Query that was slowing down
+      polymorphic queries.
+    - "Passive defaults" and other "inline" defaults can now be
+      loaded during a flush() call if needed; in particular, this
+      allows constructing relations() where a foreign key column
+      references a server-side-generated, non-primary-key
+      column. [ticket:954]
+    - Additional Session transaction fixes/changes:
+        - Fixed bug with session transaction management: parent
+          transactions weren't started on the connection when
+          adding a connection to a nested transaction.
+        - session.transaction now always refers to the innermost
+          active transaction, even when commit/rollback are called
+          directly on the session transaction object.
+        - Two-phase transactions can now be prepared.
+        - When preparing a two-phase transaction fails on one
+          connection, all the connections are rolled back.
+        - session.close() didn't close all transactions when
+          nested transactions were used.
+        - rollback() previously erroneously set the current
+          transaction directly to the parent of the transaction
+          that could be rolled back to. Now it rolls back the next
+          transaction up that can handle it, but sets the current
+          transaction to it's parent and inactivates the
+          transactions in between. Inactive transactions can only
+          be rolled back or closed, any other call results in an
+          error.
+        - autoflush for commit() wasn't flushing for simple
+          subtransactions.
+        - unitofwork flush didn't close the failed transaction
+          when the session was not in a transaction and commiting
+          the transaction failed.
+    - Miscellaneous tickets: [ticket:940] [ticket:964]
+- general
+    - Fixed a variety of hidden and some not-so-hidden
+      compatibility issues for Python 2.3, thanks to new support
+      for running the full test suite on 2.3.
+    - Warnings are now issued as type exceptions.SAWarning.
+- dialects
+    - Better support for schemas in SQLite (linked in by ATTACH
+      DATABASE ... AS name).  In some cases in the past, schema
+      names were ommitted from generated SQL for SQLite.  This is
+      no longer the case.
+    - table_names on SQLite now picks up temporary tables as well.
+    - Auto-detect an unspecified MySQL ANSI_QUOTES mode during
+      reflection operations, support for changing the mode
+      midstream.  Manual mode setting is still required if no
+      reflection is used.
+    - Fixed reflection of TIME columns on SQLite.
+    - Finally added PGMacAddr type to postgres [ticket:580]
+    - Reflect the sequence associated to a PK field (typically
+      with a BEFORE INSERT trigger) under Firebird
+    - Oracle assembles the correct columns in the result set
+      column mapping when generating a LIMIT/OFFSET subquery,
+      allows columns to map properly to result sets even if
+      long-name truncation kicks in [ticket:941]
+    - MSSQL now includes EXEC in the _is_select regexp, which
+      should allow row-returning stored procedures to be used.
+    - MSSQL now includes an experimental implementation of
+      LIMIT/OFFSET using the ANSI SQL row_number() function, so it
+      requires MSSQL-2005 or higher. To enable the feature, add
+      "has_window_funcs" to the keyword arguments for connect, or
+      add "?has_window_funcs=1" to your dburi query arguments.
+- ext
+    - Changed ext.activemapper to use a non-transactional session
+      for the objectstore.
+    - Fixed output order of "['a'] + obj.proxied" binary operation
+      on association-proxied lists.
+- general
+    - sub version numbering scheme changed to suite
+      setuptools version number rules; easy_install -u
+      should now get this version over 0.4.2.
+- sql
+    - Text type is properly exported now and does not
+      raise a warning on DDL create; String types with no
+      length only raise warnings during CREATE TABLE
+      [ticket:912]
+    - new UnicodeText type is added, to specify an
+      encoded, unlengthed Text type
+    - fixed bug in union() so that select() statements
+      which don't derive from FromClause objects can be
+      unioned
+- orm
+    - fixed bug with session.dirty when using "mutable
+      scalars" (such as PickleTypes)
+    - added a more descriptive error message when flushing
+      on a relation() that has non-locally-mapped columns
+      in its primary or secondary join condition
+- dialects
+    - Fixed reflection of mysql empty string column
+      defaults.
+0.4.2b  (0.4.2p2)
+- sql
+    - changed name of TEXT to Text since its a "generic"
+      type; TEXT name is deprecated until 0.5. The
+      "upgrading" behavior of String to Text when no
+      length is present is also deprecated until 0.5; will
+      issue a warning when used for CREATE TABLE
+      statements (String with no length for SQL expression
+      purposes is still fine) [ticket:912]
+    - generative select.order_by(None) / group_by(None)
+      was not managing to reset order by/group by
+      criterion, fixed [ticket:924]
+- orm
+    - suppressing *all* errors in
+      InstanceState.__cleanup() now.
+    - fixed an attribute history bug whereby assigning a
+      new collection to a collection-based attribute which
+      already had pending changes would generate incorrect
+      history [ticket:922]
+    - fixed delete-orphan cascade bug whereby setting the
+      same object twice to a scalar attribute could log it
+      as an orphan [ticket:925]
+    - Fixed cascades on a += assignment to a list-based
+      relation.
+    - synonyms can now be created against props that don't
+      exist yet, which are later added via add_property().
+      This commonly includes backrefs. (i.e. you can make
+      synonyms for backrefs without worrying about the
+      order of operations) [ticket:919]
+    - fixed bug which could occur with polymorphic "union"
+      mapper which falls back to "deferred" loading of
+      inheriting tables
+    - the "columns" collection on a mapper/mapped class
+      (i.e. 'c') is against the mapped table, not the
+      select_table in the case of polymorphic "union"
+      loading (this shouldn't be noticeable).
+- ext
+    - '+', '*', '+=' and '*=' support for association
+      proxied lists.
+- dialects
+    - mssql - narrowed down the test for "date"/"datetime"
+      in MSDate/ MSDateTime subclasses so that incoming
+      "datetime" objects don't get mis-interpreted as
+      "date" objects and vice versa, [ticket:923]
+0.4.2a   (0.4.2p1)
+- orm
+    - fixed fairly critical bug whereby the same instance could be listed
+      more than once in the collection; most typically
+      reproduced when using a combination of inheriting mappers and 
+      ScopedSession.mapper, as the multiple __init__ calls per instance
+      could save() the object with distinct _state objects
+    - added very rudimentary yielding iterator behavior to Query.  Call
+      query.yield_per(<number of rows>) and evaluate the Query in an 
+      iterative context; every collection of N rows will be packaged up
+      and yielded.  Use this method with extreme caution since it does
+      not attempt to reconcile eagerly loaded collections across
+      result batch boundaries, nor will it behave nicely if the same
+      instance occurs in more than one batch.  This means that an eagerly
+      loaded collection will get cleared out if it's referenced in more than
+      one batch, and in all cases attributes will be overwritten on instances
+      that occur in more than one batch.
+   - Fixed in-place set mutation operators for set collections and association
+     proxied sets. [ticket:920]
+- dialects
+    - Fixed the missing call to subtype result processor for the PGArray
+      type. [ticket:913]
+- sql
+    - generic functions ! we introduce a database of known SQL functions, such
+      as current_timestamp, coalesce, and create explicit function objects
+      representing them. These objects have constrained argument lists, are
+      type aware, and can compile in a dialect-specific fashion. So saying
+      func.char_length("foo", "bar") raises an error (too many args),
+      func.coalesce(, 10, 5),, 10, 15))
+      knows that its return type is a Date. We only have a few functions
+      represented so far but will continue to add to the system [ticket:615]
+    - auto-reconnect support improved; a Connection can now automatically
+      reconnect after its underlying connection is invalidated, without
+      needing to connect() again from the engine.  This allows an ORM session
+      bound to a single Connection to not need a reconnect.
+      Open transactions on the Connection must be rolled back after an invalidation 
+      of the underlying connection else an error is raised.  Also fixed
+      bug where disconnect detect was not being called for cursor(), rollback(),
+      or commit().
+    - added new flag to String and create_engine(),
+      assert_unicode=(True|False|'warn'|None). Defaults to `False` or `None` on
+      create_engine() and String, `'warn'` on the Unicode type. When `True`,
+      results in all unicode conversion operations raising an exception when a
+      non-unicode bytestring is passed as a bind parameter. 'warn' results
+      in a warning. It is strongly advised that all unicode-aware applications 
+      make proper use of Python unicode objects (i.e. u'hello' and not 'hello')
+      so that data round trips accurately.
+    - generation of "unique" bind parameters has been simplified to use the same
+      "unique identifier" mechanisms as everything else.  This doesn't affect
+      user code, except any code that might have been hardcoded against the generated
+      names.  Generated bind params now have the form "<paramname>_<num>",
+      whereas before only the second bind of the same name would have this form.
+    - select().as_scalar() will raise an exception if the select does not have
+      exactly one expression in its columns clause.
+    - bindparam() objects themselves can be used as keys for execute(), i.e.
+      statement.execute({bind1:'foo', bind2:'bar'})
+    - added new methods to TypeDecorator, process_bind_param() and
+      process_result_value(), which automatically take advantage of the processing
+      of the underlying type.  Ideal for using with Unicode or Pickletype.
+      TypeDecorator should now be the primary way to augment the behavior of any
+      existing type including other TypeDecorator subclasses such as PickleType.
+    - selectables (and others) will issue a warning when two columns in
+      their exported columns collection conflict based on name.
+    - tables with schemas can still be used in sqlite, firebird,
+      schema name just gets dropped [ticket:890]
+    - changed the various "literal" generation functions to use an anonymous
+      bind parameter.  not much changes here except their labels now look 
+      like ":param_1", ":param_2" instead of ":literal"
+    - column labels in the form "tablename.columname", i.e. with a dot, are now
+      supported.
+    - from_obj keyword argument to select() can be a scalar or a list.
+- orm
+   - a major behavioral change to collection-based backrefs: they no 
+     longer trigger lazy loads !  "reverse" adds and removes 
+     are queued up and are merged with the collection when it is 
+     actually read from and loaded; but do not trigger a load beforehand.
+     For users who have noticed this behavior, this should be much more
+     convenient than using dynamic relations in some cases; for those who 
+     have not, you might notice your apps using a lot fewer queries than
+     before in some situations. [ticket:871]
+   - mutable primary key support is added. primary key columns can be
+     changed freely, and the identity of the instance will change upon
+     flush. In addition, update cascades of foreign key referents (primary
+     key or not) along relations are supported, either in tandem with the
+     database's ON UPDATE CASCADE (required for DB's like Postgres) or
+     issued directly by the ORM in the form of UPDATE statements, by setting
+     the flag "passive_cascades=False".
+   - inheriting mappers now inherit the MapperExtensions of their parent
+     mapper directly, so that all methods for a particular MapperExtension
+     are called for subclasses as well.  As always, any MapperExtension 
+     can return either EXT_CONTINUE to continue extension processing
+     or EXT_STOP to stop processing.  The order of mapper resolution is:
+     <extensions declared on the classes mapper> <extensions declared on the
+     classes' parent mapper> <globally declared extensions>.
+     Note that if you instantiate the same extension class separately 
+     and then apply it individually for two mappers in the same inheritance 
+     chain, the extension will be applied twice to the inheriting class,
+     and each method will be called twice.
+     To apply a mapper extension explicitly to each inheriting class but
+     have each method called only once per operation, use the same 
+     instance of the extension for both mappers.
+     [ticket:490]
+   - MapperExtension.before_update() and after_update() are now called
+     symmetrically; previously, an instance that had no modified column
+     attributes (but had a relation() modification) could be called with 
+     before_update() but not after_update() [ticket:907]
+   - columns which are missing from a Query's select statement
+     now get automatically deferred during load.
+   - mapped classes which extend "object" and do not provide an 
+     __init__() method will now raise TypeError if non-empty *args 
+     or **kwargs are present at instance construction time (and are 
+     not consumed by any extensions such as the scoped_session mapper), 
+     consistent with the behavior of normal Python classes [ticket:908]
+   - fixed Query bug when filter_by() compares a relation against None
+     [ticket:899]
+   - improved support for pickling of mapped entities.  Per-instance
+     lazy/deferred/expired callables are now serializable so that
+     they serialize and deserialize with _state. 
+   - new synonym() behavior: an attribute will be placed on the mapped
+     class, if one does not exist already, in all cases. if a property
+     already exists on the class, the synonym will decorate the property
+     with the appropriate comparison operators so that it can be used in in
+     column expressions just like any other mapped attribute (i.e. usable in
+     filter(), etc.) the "proxy=True" flag is deprecated and no longer means
+     anything. Additionally, the flag "map_column=True" will automatically
+     generate a ColumnProperty corresponding to the name of the synonym,
+     i.e.: 'somename':synonym('_somename', map_column=True) will map the
+     column named 'somename' to the attribute '_somename'. See the example
+     in the mapper docs. [ticket:801]
+   - Query.select_from() now replaces all existing FROM criterion with
+     the given argument; the previous behavior of constructing a list
+     of FROM clauses was generally not useful as is required 
+     filter() calls to create join criterion, and new tables introduced
+     within filter() already add themselves to the FROM clause.  The
+     new behavior allows not just joins from the main table, but select 
+     statements as well.  Filter criterion, order bys, eager load
+     clauses will be "aliased" against the given statement.
+   - this month's refactoring of attribute instrumentation changes
+     the "copy-on-load" behavior we've had since midway through 0.3
+     with "copy-on-modify" in most cases.  This takes a sizable chunk
+     of latency out of load operations and overall does less work
+     as only attributes which are actually modified get their 
+     "committed state" copied.  Only "mutable scalar" attributes
+     (i.e. a pickled object or other mutable item), the reason for 
+     the copy-on-load change in the first place, retain the old 
+     behavior.
+   - a slight behavioral change to attributes is, del'ing an attribute
+     does *not* cause the lazyloader of that attribute to fire off again;
+     the "del" makes the effective value of the attribute "None".  To
+     re-trigger the "loader" for an attribute, use 
+     session.expire(instance, [attrname]).
+   - query.filter(SomeClass.somechild == None), when comparing
+     a many-to-one property to None, properly generates "id IS NULL"
+     including that the NULL is on the right side.
+   - query.order_by() takes into account aliased joins, i.e.
+     query.join('orders', aliased=True).order_by(
+   - eagerload(), lazyload(), eagerload_all() take an optional 
+     second class-or-mapper argument, which will select the mapper
+     to apply the option towards.  This can select among other
+     mappers which were added using add_entity().  
+   - eagerloading will work with mappers added via add_entity().
+   - added "cascade delete" behavior to "dynamic" relations just like
+     that of regular relations.  if passive_deletes flag (also just added)
+     is not set, a delete of the parent item will trigger a full load of 
+     the child items so that they can be deleted or updated accordingly.
+   - also with dynamic, implemented correct count() behavior as well
+     as other helper methods.
+   - fix to cascades on polymorphic relations, such that cascades
+     from an object to a polymorphic collection continue cascading 
+     along the set of attributes specific to each element in the collection.
+   - query.get() and query.load() do not take existing filter or other
+     criterion into account; these methods *always* look up the given id
+     in the database or return the current instance from the identity map, 
+     disregarding any existing filter, join, group_by or other criterion
+     which has been configured. [ticket:893]
+   - added support for version_id_col in conjunction with inheriting mappers.
+     version_id_col is typically set on the base mapper in an inheritance
+     relationship where it takes effect for all inheriting mappers. 
+     [ticket:883]
+   - relaxed rules on column_property() expressions having labels; any
+     ColumnElement is accepted now, as the compiler auto-labels non-labeled
+     ColumnElements now.  a selectable, like a select() statement, still
+     requires conversion to ColumnElement via as_scalar() or label().
+   - fixed backref bug where you could not del instance.attr if attr
+     was None
+   - several ORM attributes have been removed or made private:
+     mapper.get_attr_by_column(), mapper.set_attr_by_column(), 
+     mapper.pks_by_table, mapper.cascade_callable(), 
+     MapperProperty.cascade_callable(), mapper.canload(),
+     mapper.save_obj(), mapper.delete_obj(), mapper._mapper_registry, 
+     attributes.AttributeManager
+   - Assigning an incompatible collection type to a relation attribute now
+     raises TypeError instead of sqlalchemy's ArgumentError.
+   - Bulk assignment of a MappedCollection now raises an error if a key in the
+     incoming dictionary does not match the key that the collection's keyfunc
+     would use for that value. [ticket:886]
+   - Custom collections can now specify a @converter method to translate
+     objects used in "bulk" assignment into a stream of values, as in::
+        obj.col = [newval1, newval2]
+        # or
+        obj.dictcol = {'foo': newval1, 'bar': newval2}
+     The MappedCollection uses this hook to ensure that incoming key/value
+     pairs are sane from the collection's perspective.
+   - fixed endless loop issue when using lazy="dynamic" on both 
+     sides of a bi-directional relationship [ticket:872]
+   - more fixes to the LIMIT/OFFSET aliasing applied with Query + eagerloads,
+     in this case when mapped against a select statement [ticket:904]
+   - fix to self-referential eager loading such that if the same mapped
+     instance appears in two or more distinct sets of columns in the same
+     result set, its eagerly loaded collection will be populated regardless
+     of whether or not all of the rows contain a set of "eager" columns for
+     that collection.  this would also show up as a KeyError when fetching
+     results with join_depth turned on.
+   - fixed bug where Query would not apply a subquery to the SQL when LIMIT
+     was used in conjunction with an inheriting mapper where the eager 
+     loader was only in the parent mapper.
+   - clarified the error message which occurs when you try to update()
+     an instance with the same identity key as an instance already present
+     in the session.
+   - some clarifications and fixes to merge(instance, dont_load=True).  
+     fixed bug where lazy loaders were getting disabled on returned instances.
+     Also, we currently do not support merging an instance which has uncommitted
+     changes on it, in the case that dont_load=True is used....this will
+     now raise an error.  This is due to complexities in merging the 
+     "committed state" of the given instance to correctly correspond to the
+     newly copied instance, as well as other modified state.  
+     Since the use case for dont_load=True is caching, the given instances 
+     shouldn't have any uncommitted changes on them anyway.
+     We also copy the instances over without using any events now, so that
+     the 'dirty' list on the new session remains unaffected.
+   - fixed bug which could arise when using session.begin_nested() in conjunction
+     with more than one level deep of enclosing session.begin() statements
+   - fixed session.refresh() with instance that has custom entity_name 
+     [ticket:914]
+- dialects
+   - sqlite SLDate type will not erroneously render "microseconds" portion 
+     of a datetime or time object.
+   - oracle
+      - added disconnect detection support for Oracle
+      - some cleanup to binary/raw types so that cx_oracle.LOB is detected
+        on an ad-hoc basis [ticket:902]
+   - MSSQL
+      - PyODBC no longer has a global "set nocount on".
+      - Fix non-identity integer PKs on autload [ticket:824]
+      - Better support for convert_unicode [ticket:839]
+      - Less strict date conversion for pyodbc/adodbapi [ticket:842]
+      - Schema-qualified tables / autoload [ticket:901]
+   - Firebird backend
+     - does properly reflect domains (partially fixing [ticket:410]) and
+       PassiveDefaults
+     - reverted to use default poolclass (was set to SingletonThreadPool in
+       0.4.0 [3562] for test purposes)
+     - map func.length() to 'char_length' (easily overridable with the UDF
+       'strlen' on old versions of Firebird)
+- sql
+  - the "shortname" keyword parameter on bindparam() has been 
+    deprecated.
+  - Added contains operator (generates a "LIKE %<other>%" clause).
+  - anonymous column expressions are automatically labeled.  
+    e.g. select([x* 5]) produces "SELECT x * 5 AS anon_1".
+    This allows the labelname to be present in the cursor.description
+    which can then be appropriately matched to result-column processing
+    rules. (we can't reliably use positional tracking for result-column 
+    matches since text() expressions may represent multiple columns).
+  - operator overloading is now controlled by TypeEngine objects - the 
+    one built-in operator overload so far is String types overloading
+    '+' to be the string concatenation operator.
+    User-defined types can also define their own operator overloading
+    by overriding the adapt_operator(self, op) method.
+  - untyped bind parameters on the right side of a binary expression
+    will be assigned the type of the left side of the operation, to better
+    enable the appropriate bind parameter processing to take effect
+    [ticket:819]
+  - Removed regular expression step from most statement compilations.
+    Also fixes [ticket:833]
+  - Fixed empty (zero column) sqlite inserts, allowing inserts on
+    autoincrementing single column tables.
+  - Fixed expression translation of text() clauses; this repairs various
+    ORM scenarios where literal text is used for SQL expressions
+  - Removed ClauseParameters object; compiled.params returns a regular
+    dictionary now, as well as result.last_inserted_params() /
+    last_updated_params().
+  - Fixed INSERT statements w.r.t. primary key columns that have
+    SQL-expression based default generators on them; SQL expression
+    executes inline as normal but will not trigger a "postfetch" condition
+    for the column, for those DB's who provide it via cursor.lastrowid
+  - func. objects can be pickled/unpickled [ticket:844]
+  - rewrote and simplified the system used to "target" columns across
+    selectable expressions.  On the SQL side this is represented by the
+    "corresponding_column()" method. This method is used heavily by the ORM
+    to "adapt" elements of an expression to similar, aliased expressions,
+    as well as to target result set columns originally bound to a 
+    table or selectable to an aliased, "corresponding" expression.  The new
+    rewrite features completely consistent and accurate behavior.
+  - Added a field ("info") for storing arbitrary data on schema items
+    [ticket:573]    
+  - The "properties" collection on Connections has been renamed "info" to
+    match schema's writable collections.  Access is still available via
+    the "properties" name until 0.5.
+  - fixed the close() method on Transaction when using strategy='threadlocal'
+  - fix to compiled bind parameters to not mistakenly populate None
+    [ticket:853]
+  - <Engine|Connection>._execute_clauseelement becomes a public method
+    Connectable.execute_clauseelement
+- orm
+  - eager loading with LIMIT/OFFSET applied no longer adds the primary 
+    table joined to a limited subquery of itself; the eager loads now
+    join directly to the subquery which also provides the primary table's
+    columns to the result set.  This eliminates a JOIN from all eager loads
+    with LIMIT/OFFSET.  [ticket:843]
+  - session.refresh() and session.expire() now support an additional argument
+    "attribute_names", a list of individual attribute keynames to be refreshed
+    or expired, allowing partial reloads of attributes on an already-loaded 
+    instance. [ticket:802]
+  - added op() operator to instrumented attributes; i.e. 
+'ilike')('%somename%') [ticket:767]
+  - Mapped classes may now define __eq__, __hash__, and __nonzero__ methods
+    with arbitrary semantics.  The orm now handles all mapped instances on
+    an identity-only basis. (e.g. 'is' vs '==') [ticket:676]
+  - the "properties" accessor on Mapper is removed; it now throws an informative
+    exception explaining the usage of mapper.get_property() and 
+    mapper.iterate_properties
+  - added having() method to Query, applies HAVING to the generated statement
+    in the same way as filter() appends to the WHERE clause.
+  - The behavior of query.options() is now fully based on paths, i.e. an
+    option such as eagerload_all('x.y.z.y.x') will apply eagerloading to
+    only those paths, i.e. and not 'x.y.x'; eagerload('children.children')
+    applies only to exactly two-levels deep, etc. [ticket:777]
+  - PickleType will compare using `==` when set up with mutable=False,
+    and not the `is` operator.  To use `is` or any other comparator, send
+    in a custom comparison function using PickleType(comparator=my_custom_comparator).
+  - query doesn't throw an error if you use distinct() and an order_by()
+    containing UnaryExpressions (or other) together [ticket:848]
+  - order_by() expressions from joined tables are properly added to columns 
+    clause when using distinct() [ticket:786]
+  - fixed error where Query.add_column() would not accept a class-bound
+    attribute as an argument; Query also raises an error if an invalid
+    argument was sent to add_column() (at instances() time) [ticket:858]
+  - added a little more checking for garbage-collection dereferences in
+    InstanceState.__cleanup() to reduce "gc ignored" errors on app
+    shutdown
+  - The session API has been solidified:
+    - It's an error to an object which is already
+      persistent [ticket:840]
+    - It's an error to session.delete() an object which is *not*
+      persistent.
+    - session.update() and session.delete() raise an error when updating
+      or deleting an instance that is already in the session with a
+      different identity.
+    - The session checks more carefully when determining "object X already
+      in another session"; e.g. if you pickle a series of objects and
+      unpickle (i.e. as in a Pylons HTTP session or similar), they can go
+      into a new session without any conflict
+    - merge() includes a keyword argument "dont_load=True".  setting this
+      flag will cause the merge operation to not load any data from the
+      database in response to incoming detached objects, and will accept
+      the incoming detached object as though it were already present in
+      that session.  Use this to merge detached objects from external
+      caching systems into the session.
+  - Deferred column attributes no longer trigger a load operation when the
+    attribute is assigned to.  In those cases, the newly assigned value
+    will be present in the flushes' UPDATE statement unconditionally.
+  - Fixed a truncation error when re-assigning a subset of a collection
+    (obj.relation = obj.relation[1:]) [ticket:834]
+  - De-cruftified backref configuration code, backrefs which step on
+    existing properties now raise an error [ticket:832]
+  - Improved behavior of add_property() etc., fixed [ticket:831] involving
+    synonym/deferred.
+  - Fixed clear_mappers() behavior to better clean up after itself.
+  - Fix to "row switch" behavior, i.e. when an INSERT/DELETE is combined
+    into a single UPDATE; many-to-many relations on the parent object
+    update properly.  [ticket:841]
+  - Fixed __hash__ for association proxy- these collections are unhashable,
+    just like their mutable Python counterparts.
+  - Added proxying of save_or_update, __contains__ and __iter__ methods for
+    scoped sessions.
+  - fixed very hard-to-reproduce issue where by the FROM clause of Query
+    could get polluted by certain generative calls [ticket:852]
+- dialects
+  - Added experimental support for MaxDB (versions >= only).
+  - oracle will now reflect "DATE" as an OracleDateTime column, not 
+    OracleDate
+  - added awareness of schema name in oracle table_names() function,
+    fixes metadata.reflect(schema='someschema') [ticket:847]
+  - MSSQL anonymous labels for selection of functions made deterministic
+  - sqlite will reflect "DECIMAL" as a numeric column.
+  - Made access dao detection more reliable [ticket:828]
+  - Renamed the Dialect attribute 'preexecute_sequences' to
+    'preexecute_pk_sequences'.  An attribute porxy is in place for
+    out-of-tree dialects using the old name.
+  - Added test coverage for unknown type reflection. Fixed sqlite/mysql
+    handling of type reflection for unknown types.
+  - Added REAL for mysql dialect (for folks exploiting the 
+    REAL_AS_FLOAT sql mode).
+  - mysql Float, MSFloat and MSDouble constructed without arguments
+    now produce no-argument DDL, e.g.'FLOAT'.
+- misc
+  - Removed unused util.hash().
+- (see 0.4.0beta1 for the start of major changes against 0.3, 
+  as well as )
+- Added initial Sybase support (mxODBC so far) [ticket:785]
+- Added partial index support for PostgreSQL. Use the postgres_where keyword
+  on the Index.
+- string-based query param parsing/config file parser understands
+  wider range of string values for booleans [ticket:817]
+- backref remove object operation doesn't fail if the other-side
+  collection doesn't contain the item, supports noload collections
+  [ticket:813]
+- removed __len__ from "dynamic" collection as it would require issuing
+  a SQL "count()" operation, thus forcing all list evaluations to issue
+  redundant SQL [ticket:818]
+- inline optimizations added to locate_dirty() which can greatly speed up
+  repeated calls to flush(), as occurs with autoflush=True [ticket:816]
+- The IdentifierPreprarer's _requires_quotes test is now regex based.  Any
+  out-of-tree dialects that provide custom sets of legal_characters or
+  illegal_initial_characters will need to move to regexes or override
+  _requires_quotes.
+- Firebird has supports_sane_rowcount and supports_sane_multi_rowcount set
+  to False due to ticket #370 (right way).
+- Improvements and fixes on Firebird reflection:
+  . FBDialect now mimics OracleDialect, regarding case-sensitivity of TABLE and
+    COLUMN names (see 'case_sensitive remotion' topic on this current file).
+  . FBDialect.table_names() doesn't bring system tables (ticket:796).
+  . FB now reflects Column's nullable property correctly.
+- Fixed SQL compiler's awareness of top-level column labels as used
+  in result-set processing; nested selects which contain the same column 
+  names don't affect the result or conflict with result-column metadata.
+- query.get() and related functions (like many-to-one lazyloading)
+  use compile-time-aliased bind parameter names, to prevent
+  name conflicts with bind parameters that already exist in the 
+  mapped selectable.
+- Fixed three- and multi-level select and deferred inheritance loading
+  (i.e. abc inheritance with no select_table), [ticket:795]
+- Ident passed to id_chooser in always a list.
+- The no-arg ResultProxy._row_processor() is now the class attribute
+  `_process_row`.
+- Added support for returning values from inserts and udpates for
+  PostgreSQL 8.2+. [ticket:797]
+- PG reflection, upon seeing the default schema name being used explicitly
+  as the "schema" argument in a Table, will assume that this is the the 
+  user's desired convention, and will explicitly set the "schema" argument
+  in foreign-key-related reflected tables, thus making them match only
+  with Table constructors that also use the explicit "schema" argument
+  (even though its the default schema).  
+  In other words, SA assumes the user is being consistent in this usage.
+- fixed sqlite reflection of BOOL/BOOLEAN [ticket:808]
+- Added support for UPDATE with LIMIT on mysql.
+- null foreign key on a m2o doesn't trigger a lazyload [ticket:803]
+- oracle does not implicitly convert to unicode for non-typed result
+  sets (i.e. when no TypeEngine/String/Unicode type is even being used;
+  previously it was detecting DBAPI types and converting regardless).
+  should fix [ticket:800]
+- fix to anonymous label generation of long table/column names [ticket:806]
+- Firebird dialect now uses SingletonThreadPool as poolclass.
+- Firebird now uses dialect.preparer to format sequences names
+- Fixed breakage with postgres and multiple two-phase transactions. Two-phase
+  commits and and rollbacks didn't automatically end up with a new transaction
+  as the usual dbapi commits/rollbacks do. [ticket:810]
+- Added an option to the _ScopedExt mapper extension to not automatically
+  save new objects to session on object initialization.
+- fixed Oracle non-ansi join syntax
+- PickleType and Interval types (on db not supporting it natively) are now 
+  slightly faster.
+- Added Float and Time types to Firebird (FBFloat and FBTime). Fixed
+  BLOB SUB_TYPE for TEXT and Binary types.
+- Changed the API for the in_ operator. in_() now accepts a single argument
+  that is a sequence of values or a selectable. The old API of passing in
+  values as varargs still works but is deprecated.
+- The Session identity map is now *weak referencing* by default, use
+  weak_identity_map=False to use a regular dict.  The weak dict we are using
+  is customized to detect instances which are "dirty" and maintain a
+  temporary strong reference to those instances until changes are flushed.
+- Mapper compilation has been reorganized such that most compilation occurs
+  upon mapper construction.  This allows us to have fewer calls to
+  mapper.compile() and also to allow class-based properties to force a
+  compilation (i.e. User.addresses == 7 will compile all mappers; this is
+  [ticket:758]).  The only caveat here is that an inheriting mapper now
+  looks for its inherited mapper upon construction; so mappers within
+  inheritance relationships need to be constructed in inheritance order
+  (which should be the normal case anyway).
+- added "FETCH" to the keywords detected by Postgres to indicate a
+  result-row holding statement (i.e. in addition to "SELECT").
+- Added full list of SQLite reserved keywords so that they get escaped
+  properly.
+- Tightened up the relationship between the Query's generation of "eager
+  load" aliases, and Query.instances() which actually grabs the eagerly
+  loaded rows.  If the aliases were not specifically generated for that
+  statement by EagerLoader, the EagerLoader will not take effect when the
+  rows are fetched.  This prevents columns from being grabbed accidentally
+  as being part of an eager load when they were not meant for such, which
+  can happen with textual SQL as well as some inheritance situations.  It's
+  particularly important since the "anonymous aliasing" of columns uses
+  simple integer counts now to generate labels.
+- Removed "parameters" argument from clauseelement.compile(), replaced with
+  "column_keys".  The parameters sent to execute() only interact with the
+  insert/update statement compilation process in terms of the column names
+  present but not the values for those columns.  Produces more consistent
+  execute/executemany behavior, simplifies things a bit internally.
+- Added 'comparator' keyword argument to PickleType.  By default, "mutable"
+  PickleType does a "deep compare" of objects using their dumps()
+  representation.  But this doesn't work for dictionaries.  Pickled objects
+  which provide an adequate __eq__() implementation can be set up with
+  "PickleType(comparator=operator.eq)" [ticket:560]
+- Added session.is_modified(obj) method; performs the same "history"
+  comparison operation as occurs within a flush operation; setting
+  include_collections=False gives the same result as is used when the flush
+  determines whether or not to issue an UPDATE for the instance's row.
+- Added "schema" argument to Sequence; use this with Postgres /Oracle when
+  the sequence is located in an alternate schema.  Implements part of
+  [ticket:584], should fix [ticket:761].
+- Fixed reflection of the empty string for mysql enums.
+- Changed MySQL dialect to use the older LIMIT <offset>, <limit> syntax
+  instead of LIMIT <l> OFFSET <o> for folks using 3.23. [ticket:794]
+- Added 'passive_deletes="all"' flag to relation(), disables all nulling-out
+  of foreign key attributes during a flush where the parent object is
+  deleted.
+- Column defaults and onupdates, executing inline, will add parenthesis for
+  subqueries and other parenthesis-requiring expressions
+- The behavior of String/Unicode types regarding that they auto-convert to
+  TEXT/CLOB when no length is present now occurs *only* for an exact type of
+  String or Unicode with no arguments.  If you use VARCHAR or NCHAR
+  (subclasses of String/Unicode) with no length, they will be interpreted by
+  the dialect as VARCHAR/NCHAR; no "magic" conversion happens there.  This
+  is less surprising behavior and in particular this helps Oracle keep
+  string-based bind parameters as VARCHARs and not CLOBs [ticket:793].
+- Fixes to ShardedSession to work with deferred columns [ticket:771].
+- User-defined shard_chooser() function must accept "clause=None" argument;
+  this is the ClauseElement passed to session.execute(statement) and can be
+  used to determine correct shard id (since execute() doesn't take an
+  instance.)
+- Adjusted operator precedence of NOT to match '==' and others, so that
+  ~(x <operator> y) produces NOT (x <op> y), which is better compatible
+  with older MySQL versions. [ticket:764].  This doesn't apply to "~(x==y)"
+  as it does in 0.3 since ~(x==y) compiles to "x != y", but still applies
+  to operators like BETWEEN.
+- Other tickets: [ticket:768], [ticket:728], [ticket:779], [ticket:757]
+- Connection pool fixes; the better performance of beta4 remains but fixes
+  "connection overflow" and other bugs which were present (like
+  [ticket:754]).
+- Fixed bugs in determining proper sync clauses from custom inherit
+  conditions. [ticket:769]
+- Extended 'engine_from_config' coercion for QueuePool size / overflow.
+  [ticket:763]
+- mysql views can be reflected again. [ticket:748]
+- AssociationProxy can now take custom getters and setters.
+- Fixed malfunctioning BETWEEN in orm queries.
+- Fixed OrderedProperties pickling [ticket:762]
+- SQL-expression defaults and sequences now execute "inline" for all
+  non-primary key columns during an INSERT or UPDATE, and for all columns
+  during an executemany()-style call. inline=True flag on any insert/update
+  statement also forces the same behavior with a single execute().
+  result.postfetch_cols() is a collection of columns for which the previous
+  single insert or update statement contained a SQL-side default expression.
+- Fixed PG executemany() behavior, [ticket:759]
+- postgres reflects tables with autoincrement=False for primary key columns
+  which have no defaults.
+- postgres no longer wraps executemany() with individual execute() calls,
+  instead favoring performance.  "rowcount"/"concurrency" checks with
+  deleted items (which use executemany) are disabled with PG since psycopg2
+  does not report proper rowcount for executemany().
+- Tickets fixed:
+  - [ticket:742]
+  - [ticket:748]
+  - [ticket:760]
+  - [ticket:762]
+  - [ticket:763]
+- Tidied up what ends up in your namespace when you 'from sqlalchemy import *':
+  - 'table' and 'column' are no longer imported.  They remain available by
+    direct reference (as in 'sql.table' and 'sql.column') or a glob import
+    from the sql package.  It was too easy to accidentally use a
+    sql.expressions.table instead of schema.Table when just starting out
+    with SQLAlchemy, likewise column.
+  - Internal-ish classes like ClauseElement, FromClause, NullTypeEngine,
+    etc., are also no longer imported into your namespace
+  - The 'Smallinteger' compatiblity name (small i!) is no longer imported,
+    but remains in for now.  SmallInteger (big I!) is still
+    imported.
+- The connection pool uses a "threadlocal" strategy internally to return
+  the same connection already bound to a thread, for "contextual" connections;
+  these are the connections used when you do a "connectionless" execution
+  like insert().execute().  This is like a "partial" version of the
+  "threadlocal" engine strategy but without the thread-local transaction part
+  of it.  We're hoping it reduces connection pool overhead as well as
+  database usage.  However, if it proves to impact stability in a negative way,
+  we'll roll it right back.
+- Fix to bind param processing such that "False" values (like blank strings)
+  still get processed/encoded.
+- Fix to select() "generative" behavior, such that calling column(),
+  select_from(), correlate(), and with_prefix() does not modify the
+  original select object [ticket:752]
+- Added a "legacy" adapter to types, such that user-defined TypeEngine
+  and TypeDecorator classes which define convert_bind_param() and/or
+  convert_result_value() will continue to function.  Also supports
+  calling the super() version of those methods.
+- Added session.prune(), trims away instances cached in a session that
+  are no longer referenced elsewhere. (A utility for strong-ref
+  identity maps).
+- Added close() method to Transaction.  Closes out a transaction using
+  rollback if it's the outermost transaction, otherwise just ends
+  without affecting the outer transaction.
+- Transactional and non-transactional Session integrates better with
+  bound connection; a close() will ensure that connection
+  transactional state is the same as that which existed on it before
+  being bound to the Session.
+- Modified SQL operator functions to be module-level operators,
+  allowing SQL expressions to be pickleable. [ticket:735]
+- Small adjustment to mapper class.__init__ to allow for Py2.6
+  object.__init__() behavior.
+- Fixed 'prefix' argument for select()
+- Connection.begin() no longer accepts nested=True, this logic is now
+  all in begin_nested().
+- Fixes to new "dynamic" relation loader involving cascades
+- Tickets fixed:
+  - [ticket:735]
+  - [ticket:752]
+- SQL types optimization:
+  - New performance tests show a combined mass-insert/mass-select test as
+    having 68% fewer function calls than the same test run against 0.3.
+  - General performance improvement of result set iteration is around 10-20%.
+  - In types.AbstractType, convert_bind_param() and convert_result_value()
+    have migrated to callable-returning bind_processor() and
+    result_processor() methods.  If no callable is returned, no pre/post
+    processing function is called.
+  - Hooks added throughout base/sql/defaults to optimize the calling of bind
+    aram/result processors so that method call overhead is minimized.
+  - Support added for executemany() scenarios such that unneeded "last row id"
+    logic doesn't kick in, parameters aren't excessively traversed.
+- Added 'inherit_foreign_keys' arg to mapper().
+- Added support for string date passthrough in sqlite.
+- Tickets fixed:
+  - [ticket:738]
+  - [ticket:739]
+  - [ticket:743]
+  - [ticket:744]
+- mssql improvements.
+- oracle improvements.
+- Auto-commit after LOAD DATA INFILE for mysql.
+- A rudimental SessionExtension class has been added, allowing user-defined
+  functionality to take place at flush(), commit(), and rollback() boundaries.
+- Added engine_from_config() function for helping to create_engine() from an
+  .ini style config.
+- base_mapper() becomes a plain attribute.
+- session.execute() and scalar() can search for a Table with which to bind from
+  using the given ClauseElement.
+- Session automatically extrapolates tables from mappers with binds, also uses
+  base_mapper so that inheritance hierarchies bind automatically.
+- Moved ClauseVisitor traversal back to inlined non-recursive.
+- Tickets fixed:
+  - [ticket:730]
+  - [ticket:732]
+  - [ticket:733]
+  - [ticket:734]
 - orm
-    - new collection_class api and implementation [ticket:213]
-      collections are now instrumented via decorations rather than 
-      proxying.  you can now have collections that manage their own
-      membership, and your class instance will be directly exposed on the
-      relation property.  the changes are transparent for most users.
-        - InstrumentedList (as it was) is removed, and relation properties
-          no longer have 'clear()', '.data', or any other added methods
-          beyond those provided by the collection type. you are free, of
-          course, to add them to a custom class.
-        - __setitem__-like assignments now fire remove events for the
-          existing value, if any.
-        - dict-likes used as collection classes no longer need to change
-          __iter__ semantics- itervalues() is used by default instead. this
-          is a backwards incompatible change.
-        - subclassing dict for a mapped collection is no longer needed in
-          most cases. orm.collections provides canned implementations that
-          key objects by a specified column or a custom function of your
-          choice.
-        - collection assignment now requires a compatible type- assigning
-          None to clear a collection or assigning a list to a dict
-          collection will now raise an argument error.
-        - AttributeExtension moved to interfaces, and .delete is now
-          .remove The event method signature has also been swapped around.
-    - major overhaul for Query:  all selectXXX methods
-      are deprecated.  generative methods are now the standard
-      way to do things, i.e. filter(), filter_by(), all(), one(),
-      etc.  Deprecated methods are docstring'ed with their 
-      new replacements.
-        - Class-level properties are now usable as query elements 
-          more '.c.' !  "Class.c.propname" is now superceded by "Class.propname".
-          All clause operators are supported, as well as higher level operators
-          such as Class.prop==<some instance> for scalar attributes, 
-          Class.prop.contains(<some instance>) and Class.prop.any(<some expression>)
-          for collection-based attributes (all are also negatable).  Table-based column 
-          expressions as well as columns mounted on mapped classes via 'c' are of 
-          course still fully available and can be freely mixed with the new attributes.
-          [ticket:643]
-        - removed ancient query.select_by_attributename() capability.
-        - the aliasing logic used by eager loading has been generalized, so that
-          it also adds full automatic aliasing support to Query.  It's no longer 
-          necessary to create an explicit Alias to join to the same tables multiple times;
-          *even for self-referential relationships!!*
-            - join() and outerjoin() take arguments "aliased=True".  this causes
-            their joins to be built on aliased tables; subsequent calls
-            to filter() and filter_by() will translate all table expressions
-            (yes, real expressions using the original mapped Table) to be that of
-            the Alias for the duration of that join() (i.e. until reset_joinpoint()
-            or another join() is called). 
-            - join() and outerjoin() take arguments "id=<somestring>".  when used 
-            with "aliased=True", the id can be referenced by add_entity(cls, id=<somestring>)
-            so that you can select the joined instances even if they're from an alias.
-            - join() and outerjoin() now work with self-referential relationships!  using
-            "aliased=True", you can join as many levels deep as desired, i.e.
-            query.join(['children', 'children'], aliased=True); filter criterion will 
-            be against the rightmost joined table
-        - added query.populate_existing() - marks the query to reload
-          all attributes and collections of all instances touched in the query,
-          including eagerly-loaded entities [ticket:660]
-        - added eagerload_all(), allows eagerload_all('x.y.z') to specify eager
-          loading of all properties in the given path
-    - a rudimental sharding (horizontal scaling) system is introduced.  This system
-      uses a modified Session which can distribute read and write operations among
-      multiple databases, based on user-defined functions defining the 
-      "sharding strategy".  Instances and their dependents can be distributed 
-      and queried among multiple databases based on attribute values, round-robin
-      approaches or any other user-defined system. [ticket:618]
-    - Eager loading has been enhanced to allow even more joins in more places.
-      It now functions at any arbitrary depth along self-referential 
-      and cyclical structures.  When loading cyclical structures, specify "join_depth" 
-      on relation() indicating how many times you'd like the table to join 
-      to itself; each level gets a distinct table alias.  The alias names