Release: 2.0.23 | Release Date: November 2, 2023

# SQLAlchemy 2.0 Documentation

# 0.4 Changelog

## 0.4.8

Released: Sun Oct 12 2008

### orm

- [orm]

  Fixed bug regarding inherit_condition passed with “A=B” versus “B=A” leading to errors

  References: #1039

- [orm]

  Changes made to new, dirty and deleted collections in SessionExtension.before_flush() will take effect for that flush.

- [orm]

  Added label() method to InstrumentedAttribute to establish forwards compatibility with 0.5.

### sql

- [sql]

  column.in_(someselect) can now be used as a columns-clause expression without the subquery bleeding into the FROM clause

  References: #1074

### mysql

- [mysql]

  Added MSMediumInteger type.

  References: #1146

### sqlite

- [sqlite]

  Supplied a custom strftime() function which handles dates before 1900.

  References: #968

- [sqlite]

  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; https://itsystementwicklung.de/pipermail/list-pysqlite/2008-March/000018.html

### oracle

- [oracle]

  has_sequence() now takes schema name into account

  References: #1155

- [oracle]

  added BFILE to the list of reflected types

  References: #1121

## 0.4.7p1

Released: Thu Jul 31 2008

### orm

- [orm]

  Added “add()” and “add_all()” to scoped_session methods. Workaround for 0.4.7:

      from sqlalchemy.orm.scoping import ScopedSession, instrument

      setattr(ScopedSession, "add", instrument("add"))
      setattr(ScopedSession, "add_all", instrument("add_all"))

- [orm]

  Fixed non-2.3 compatible usage of set() and generator expression within relation().

## 0.4.7

Released: Sat Jul 26 2008

### orm

- [orm]

  The contains() operator when used with many-to-many will alias() the secondary (association) table so that multiple contains() calls will not conflict with each other

  References: #1058

- [orm]

  fixed bug preventing merge() from functioning in conjunction with a comparable_property()

- [orm]

  the enable_typechecks=False setting on relation() now only allows subtypes with inheriting mappers. Totally unrelated types, or subtypes not set up with mapper inheritance against the target mapper are still not allowed.

- [orm]

  Added is_active flag to Sessions to detect when a transaction is in progress. This flag is always True with a “transactional” (in 0.5 a non-“autocommit”) Session.

  References: #976

### sql

- [sql]

  Fixed bug when calling select([literal(‘foo’)]) or select([bindparam(‘foo’)]).

### schema

- [schema]

  create_all(), drop_all(), create(), drop() all raise an error if the table name or schema name contains more characters than that dialect’s configured character limit. Some DB’s can handle too-long table names during usage, and SQLA can handle this as well. But various reflection/ checkfirst-during-create scenarios fail since we are looking for the name within the DB’s catalog tables.

  References: #571

- [schema]

  The index name generated when you say “index=True” on a Column is truncated to the length appropriate for the dialect. Additionally, an Index with a too- long name cannot be explicitly dropped with Index.drop(), similar to.

  References: #571, #820

### mysql

- [mysql]

  Added ‘CALL’ to the list of SQL keywords which return result rows.

### oracle

- [oracle]

  Oracle get_default_schema_name() “normalizes” the name before returning, meaning it returns a lower-case name when the identifier is detected as case insensitive.

- [oracle]

  creating/dropping tables takes schema name into account when searching for the existing table, so that tables in other owner namespaces with the same name do not conflict

  References: #709

- [oracle]

  Cursors now have “arraysize” set to 50 by default on them, the value of which is configurable using the “arraysize” argument to create_engine() with the Oracle dialect. This to account for cx_oracle’s default setting of “1”, which has the effect of many round trips being sent to Oracle. This actually works well in conjunction with BLOB/CLOB-bound cursors, of which there are any number available but only for the life of that row request (so BufferedColumnRow is still needed, but less so).

  References: #1062

- [oracle]

  sqlite

    - add SLFloat type, which matches the SQLite REAL type affinity. Previously, only SLNumeric was provided which fulfills NUMERIC affinity, but that’s not the same as REAL.

### misc

- [postgres]

  Repaired server_side_cursors to properly detect text() clauses.

- [postgres]

  Added PGCidr type.

  References: #1092

## 0.4.6

Released: Sat May 10 2008

### orm

- [orm]

  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.

- [orm]

  Also re-established viewonly relation() configurations that join across multiple tables.

- [orm]

  Added 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)

  References: #610

- [orm]

  repaired single table inheritance such that you can single-table inherit from a joined-table inheriting mapper without issue.

  References: #1036

- [orm]

  Fixed “concatenate tuple” bug which could occur with Query.order_by() if clause adaption had taken place.

  References: #1027

- [orm]

  Removed 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.

- [orm]

  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.

- [orm]

  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.

- [orm]

  Also re-established viewonly relation() configurations that join across multiple tables.

- [orm]

  removed 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.

- [orm]

  refined mapper._save_obj() which was unnecessarily calling __ne__() on scalar values during flush

  References: #1015

- [orm]

  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.

  References: #1019

- [orm]

  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.

- [orm]

  added an example dynamic_dict/dynamic_dict.py, illustrating a simple way to place dictionary behavior on top of a dynamic_loader.

### sql

- [sql]

  Added COLLATE support via the .collate(<collation>) expression operator and collate(<expr>, <collation>) sql function.

- [sql]

  Fixed bug with union() when applied to non-Table connected select statements

- [sql]

  improved behavior of text() expressions when used as FROM clauses, such as select().select_from(text(“sometext”))

  References: #1014

- [sql]

  Column.copy() respects the value of “autoincrement”, fixes usage with Migrate

  References: #1021

### mssql

- [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

  References: #1005

- [mssql]

  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.

### misc

- [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.

- [declarative] [extension]

  fixed reentrant mapper compile hang when a declared attribute is used within ForeignKey, ie. ForeignKey(MyOtherClass.someattribute)

- [engines]

  Pool listeners can now be provided as a dictionary of callables or a (possibly partial) duck-type of PoolListener, your choice.

- [engines]

  added “rollback_returned” option to Pool which will disable the rollback() issued when connections are returned. This flag is only safe to use with a database which does not support transactions (i.e. MySQL/MyISAM).

- [ext]

  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.

- [firebird]

  Handle the “SUBSTRING(:string FROM :start FOR :length)” builtin.

## 0.4.5

Released: Fri Apr 04 2008

### orm

- [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).

- [orm]

  Also fixed behavior in merge() whereby collection elements present on the destination but not the merged collection were not being removed from the destination.

- [orm]

  Added a more aggressive check for “uncompiled mappers”, helps particularly with declarative layer

  References: #995

- [orm]

  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.

- [orm]

  Added comparable_property(), adds query Comparator behavior to regular, unmanaged Python properties

- [orm] [‘machines’] [Company.employees.of_type(Engineer)]

  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())

  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.

- [orm]

  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.

- [orm]

  query.order_by() and query.group_by() will accept multiple arguments using *args (like select() already does).

- [orm]

  Added some convenience descriptors to Query: query.statement returns the full SELECT construct, query.whereclause returns just the WHERE part of the SELECT construct.

- [orm]

  Fixed/covered case when using a False/0 value as a polymorphic discriminator.

- [orm]

  Fixed bug which was preventing synonym() attributes from being used with inheritance

- [orm]

  Fixed SQL function truncation of trailing underscores

  References: #996

- [orm]

  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.

- [orm]

  Session.execute can now find binds from metadata

- [orm]

  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).

- [orm]

  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.

- [orm]

  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

    - 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 cascade is properly detected on relations that are present on superclasses when using inheritance.

  References: #895

- [orm]

  Fixed order_by calculation in Query to properly alias mapper-config’ed order_by when using select_from()

- [orm]

  Refactored the diffing logic that kicks in when replacing one collection with another into collections.bulk_replace, useful to anyone building multi-level collections.

- [orm]

  Cascade traversal algorithm converted from recursive to iterative to support deep object graphs.

### sql

- [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

  References: #999

- [sql]

  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.

- [sql]

  ’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.

- [sql]

  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>’”.

  References: #791, #993

- [sql]

  random() is now a generic sql function and will compile to the database’s random implementation, if any.

- [sql]

  update().values() and insert().values() take keyword arguments.

- [sql]

  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.

- [sql]

  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().

### mysql

- [mysql]

  The connection.info keys the dialect uses to cache server settings have changed and are now namespaced.

### mssql

- [mssql]

  Reflected tables will now automatically load other tables which are referenced by Foreign keys in the auto-loaded table,.

  References: #979

- [mssql]

  Added executemany check to skip identity fetch,.

  References: #916

- [mssql]

  Added stubs for small date type.

  References: #884

- [mssql]

  Added a new ‘driver’ keyword parameter for the pyodbc dialect. Will substitute into the ODBC connection string if given, defaults to ‘SQL Server’.

- [mssql]

  Added a new ‘max_identifier_length’ keyword parameter for the pyodbc dialect.

- [mssql]

  Improvements to pyodbc + Unix. If you couldn’t get that combination to work before, please try again.

### oracle

- [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”.

- [oracle]

  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.

### misc

- [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))

- [declarative] [extension]

  The “deferred” function is usable with “declarative”. Simplest usage is to declare deferred and Column together, e.g.: data = deferred(Column(Text))

- [declarative] [extension]

  Declarative also gained @synonym_for(…) and @comparable_using(…), front-ends for synonym and comparable_property.

- [declarative] [extension]

  Improvements to mapper compilation when using declarative; already-compiled mappers will still trigger compiles of other uncompiled mappers when used

  References: #995

- [declarative] [extension]

  Declarative will complete setup for Columns lacking names, allows a more DRY syntax.

  > class Foo(Base):

  >   __tablename__ = ‘foos’ id = Column(Integer, primary_key=True)

- [declarative] [extension]

  inheritance in declarative can be disabled when sending “inherits=None” to __mapper_args__.

- [declarative] [extension]

  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

  References: #1001

## 0.4.4

Released: Wed Mar 12 2008

### orm

- [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.

- [orm]

  Repaired behavior of == and != operators at the relation() level when compared against NULL for one-to-one relations

  References: #985

- [orm]

  Fixed bug whereby session.expire() attributes were not loading on an polymorphically-mapped instance mapped by a select_table mapper.

- [orm]

  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.

- [orm]

  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 session.save()’ed the pending item explicitly, the attribute/collection removal still knocks it out.

- [orm]

  session.refresh() and session.expire() raise an error when called on instances which are not persistent within the session

- [orm]

  Fixed potential generative bug when the same Query was used to generate multiple Query objects using join().

- [orm]

  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.

- [orm]

  Deprecated Query methods apply_sum(), apply_max(), apply_min(), apply_avg(). Better methodologies are coming….

- [orm]

  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.

- [orm]

  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(Engineer.name==’foo’))

  > or

  > query.join(Company.employees.of_type(Engineer)).

  >   filter(Engineer.name==’foo’)

- [orm]

  Preventive code against a potential lost-reference bug in flush().

- [orm]

  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.

- [orm]

  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.

- [orm]

  Synonyms riding on top of existing descriptors are now full proxies to those descriptors.

### sql

- [sql]

  Can again create aliases of selects against textual FROM clauses.

  References: #975

- [sql]

  The value of a bindparam() can be a callable, in which case it’s evaluated at statement execution time to get the value.

- [sql]

  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)

  References: #978

- [sql]

  Implemented two-phase API for “threadlocal” engine, via engine.begin_twophase(), engine.prepare()

  References: #936

- [sql]

  Fixed bug which was preventing UNIONS from being cloneable.

  References: #986

- [sql]

  Added “bind” keyword argument to insert(), update(), delete() and DDL(). The .bind property is now assignable on those statements as well as on select().

- [sql]

  Insert statements can now be compiled with extra “prefix” words between INSERT and INTO, for vendor extensions like MySQL’s INSERT IGNORE INTO table.

### extensions

- [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.

### misc

- [dialects]

  Invalid SQLite connection URLs now raise an error.

- [dialects]

  postgres TIMESTAMP renders correctly

  References: #981

- [dialects]

  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.

## 0.4.3

Released: Thu Feb 14 2008

### general

- [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.

- [general]

  Warnings are now issued as type exceptions.SAWarning.

### orm

- [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.

- [orm]

  Fixed merge() collection-doubling bug when merging transient entities with backref’ed collections.

  References: #961

- [orm]

  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.

- [orm]

  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()

- [orm]

  The proper error message is raised when trying to access expired instance attributes with no session present

- [orm]

  dynamic_loader() / lazy=”dynamic” now accepts and uses the order_by parameter in the same way in which it works with relation().

- [orm]

  Added expire_all() method to Session. Calls expire() for all persistent instances. This is handy in conjunction with…

- [orm]

  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.

- [orm]

  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.

  References: #938

- [orm]

  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.

- [orm]

  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’, Engineer.name])

- [orm] [(‘employees’] [Engineer.name] [people.join(engineer))]

  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(

  > )

- [orm]

  General improvements to the behavior of join() in conjunction with polymorphic mappers, i.e. joining from/to polymorphic mappers and properly applying aliases.

- [orm]

  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.

  References: #933

- [orm]

  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”.

  References: #946

- [orm]

  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

- [orm]

  Fixed bug in polymorphic inheritance which made it difficult to set a working “order_by” on a polymorphic mapper.

- [orm]

  Fixed a rather expensive call in Query that was slowing down polymorphic queries.

- [orm]

  ”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.

  References: #954

- [orm]

  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 its 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 committing the transaction failed.

- [orm]

  Miscellaneous tickets:

  References: #940, #964

### sql

- [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.

- [sql]

  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.

- [sql]

  Added a callable-based DDL events interface, adds hooks before and after Tables and MetaData create and drop.

- [sql]

  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().

- [sql]

  Added “ilike()” operator to column operations. Compiles to ILIKE on postgres, lower(x) LIKE lower(y) on all others.

  References: #727

- [sql]

  Added “now()” as a generic function; on SQLite, Oracle and MSSQL compiles as “CURRENT_TIMESTAMP”; “now()” on all others.

  References: #943

- [sql]

  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

  References: #962

- [sql]

  cast() accepts text(‘something’) and other non-literal operands properly

  References: #962

- [sql]

  fixed bug in result proxy where anonymously generated column labels would not be accessible using their straight string name

- [sql]

  Deferrable constraints can now be defined.

- [sql]

  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.

  References: #915

- [sql]

  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.

- [sql]

  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.

- [sql]

  The anonymous ‘label’ generated for otherwise unlabeled functions and expressions now propagates outwards at compile time for expressions like select([select([func.foo()])]).

- [sql]

  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.

- [sql]

  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.

- [sql]

  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.)

### misc

- [dialects]

  Better support for schemas in SQLite (linked in by ATTACH DATABASE … AS name). In some cases in the past, schema names were omitted from generated SQL for SQLite. This is no longer the case.

- [dialects]

  table_names on SQLite now picks up temporary tables as well.

- [dialects]

  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.

- [dialects]

  Fixed reflection of TIME columns on SQLite.

- [dialects]

  Finally added PGMacAddr type to postgres

  References: #580

- [dialects]

  Reflect the sequence associated to a PK field (typically with a BEFORE INSERT trigger) under Firebird

- [dialects]

  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

  References: #941

- [dialects]

  MSSQL now includes EXEC in the _is_select regexp, which should allow row-returning stored procedures to be used.

- [dialects]

  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.

- [ext]

  Fixed output order of “[‘a’] + obj.proxied” binary operation on association-proxied lists.

## 0.4.2p3

Released: Wed Jan 09 2008

### general

- [general]

  sub version numbering scheme changed to suite setuptools version number rules; easy_install -u should now get this version over 0.4.2.

### orm

- [orm]

  fixed bug with session.dirty when using “mutable scalars” (such as PickleTypes)

- [orm]

  added a more descriptive error message when flushing on a relation() that has non-locally-mapped columns in its primary or secondary join condition

- [orm]

  suppressing all errors in InstanceState.__cleanup() now.

- [orm]

  fixed an attribute history bug whereby assigning a new collection to a collection-based attribute which already had pending changes would generate incorrect history

  References: #922

- [orm]

  fixed delete-orphan cascade bug whereby setting the same object twice to a scalar attribute could log it as an orphan

  References: #925

- [orm]

  Fixed cascades on a += assignment to a list-based relation.

- [orm]

  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)

  References: #919

- [orm]

  fixed bug which could occur with polymorphic “union” mapper which falls back to “deferred” loading of inheriting tables

- [orm]

  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).

- [orm]

  fixed fairly critical bug whereby the same instance could be listed more than once in the unitofwork.new 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

- [orm]

  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.

- [orm]

  Fixed in-place set mutation operators for set collections and association proxied sets.

  References: #920

### sql

- [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

  References: #912

- [sql]

  new UnicodeText type is added, to specify an encoded, unlengthed Text type

- [sql]

  fixed bug in union() so that select() statements which don’t derive from FromClause objects can be unioned

- [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)

  References: #912

- [sql]

  generative select.order_by(None) / group_by(None) was not managing to reset order by/group by criterion, fixed

  References: #924

### misc

- [dialects]

  Fixed reflection of mysql empty string column defaults.

- [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.

  References: #923

- [dialects]

  Fixed the missing call to subtype result processor for the PGArray type.

  References: #913

## 0.4.2

Released: Wed Jan 02 2008

### orm

- [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.

  References: #871

- [orm]

  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”.

- [orm]

  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.

  References: #490

- [orm]

  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()

  References: #907

- [orm]

  columns which are missing from a Query’s select statement now get automatically deferred during load.

- [orm]

  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

  References: #908

- [orm]

  fixed Query bug when filter_by() compares a relation against None

  References: #899

- [orm]

  improved support for pickling of mapped entities. Per-instance lazy/deferred/expired callables are now serializable so that they serialize and deserialize with _state.

- [orm]

  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 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.

  References: #801

- [orm]

  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.

- [orm]

  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.

- [orm] [attrname]

  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,).

- [orm]

  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.

- [orm]

  query.order_by() takes into account aliased joins, i.e. query.join(‘orders’, aliased=True).order_by(Order.id)

- [orm]

  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().

- [orm]

  eagerloading will work with mappers added via add_entity().

- [orm]

  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.

- [orm]

  also with dynamic, implemented correct count() behavior as well as other helper methods.

- [orm]

  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.

- [orm]

  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.

  References: #893

- [orm]

  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.

  References: #883

- [orm]

  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().

- [orm]

  fixed backref bug where you could not del instance.attr if attr was None

- [orm]

  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

- [orm]

  Assigning an incompatible collection type to a relation attribute now raises TypeError instead of sqlalchemy’s ArgumentError.

- [orm]

  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.

  References: #886

- [orm] [newval1] [newval2]

  Custom collections can now specify a @converter method to translate objects used in “bulk” assignment into a stream of values, as in:

      obj.col =
      # 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.

- [orm]

  fixed endless loop issue when using lazy=”dynamic” on both sides of a bi-directional relationship

  References: #872

- [orm]

  more fixes to the LIMIT/OFFSET aliasing applied with Query + eagerloads, in this case when mapped against a select statement

  References: #904

- [orm]

  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.

- [orm]

  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.

- [orm]

  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.

- [orm]

  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.

- [orm]

  fixed bug which could arise when using session.begin_nested() in conjunction with more than one level deep of enclosing session.begin() statements

- [orm]

  fixed session.refresh() with instance that has custom entity_name

  References: #914

### sql

- [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(datetime.date(2007, 10, 5), datetime.date(2005, 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

  References: #615

- [sql]

  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().

- [sql]

  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.

- [sql]

  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.

- [sql]

  select().as_scalar() will raise an exception if the select does not have exactly one expression in its columns clause.

- [sql]

  bindparam() objects themselves can be used as keys for execute(), i.e. statement.execute({bind1:’foo’, bind2:’bar’})

- [sql]

  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.

- [sql]

  selectables (and others) will issue a warning when two columns in their exported columns collection conflict based on name.

- [sql]

  tables with schemas can still be used in sqlite, firebird, schema name just gets dropped

  References: #890

- [sql]

  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”

- [sql]

  column labels in the form “tablename.columname”, i.e. with a dot, are now supported.

- [sql]

  from_obj keyword argument to select() can be a scalar or a list.

### misc

- [dialects]

  sqlite SLDate type will not erroneously render “microseconds” portion of a datetime or time object.

- [dialects]

  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

  References: #902

- [dialects]

  MSSQL

    - PyODBC no longer has a global “set nocount on”.

    - Fix non-identity integer PKs on autoload

    - Better support for convert_unicode

    - Less strict date conversion for pyodbc/adodbapi

    - Schema-qualified tables / autoload

  References: #824, #839, #842, #901

- [backend] [firebird]

  does properly reflect domains (partially fixing) and PassiveDefaults

  References: #410

- [3562] [backend] [firebird]

  reverted to use default poolclass (was set to SingletonThreadPool in 0.4.0 for test purposes)

- [backend] [firebird]

  map func.length() to ‘char_length’ (easily overridable with the UDF ‘strlen’ on old versions of Firebird)

## 0.4.1

Released: Sun Nov 18 2007

### orm

- [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.

  References: #843

- [orm]

  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.

  References: #802

- [orm]

  added op() operator to instrumented attributes; i.e. User.name.op(‘ilike’)(‘%somename%’)

  References: #767

- [orm]

  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 ‘==’)

  References: #676

- [orm]

  the “properties” accessor on Mapper is removed; it now throws an informative exception explaining the usage of mapper.get_property() and mapper.iterate_properties

- [orm]

  added having() method to Query, applies HAVING to the generated statement in the same way as filter() appends to the WHERE clause.

- [orm]

  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.

  References: #777

- [orm]

  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).

- [orm]

  query doesn’t throw an error if you use distinct() and an order_by() containing UnaryExpressions (or other) together

  References: #848

- [orm]

  order_by() expressions from joined tables are properly added to columns clause when using distinct()

  References: #786

- [orm]

  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)

  References: #858

- [orm]

  added a little more checking for garbage-collection dereferences in InstanceState.__cleanup() to reduce “gc ignored” errors on app shutdown

- [orm]

  The session API has been solidified:

- [orm]

  It’s an error to session.save() an object which is already persistent

  References: #840

- [orm]

  It’s an error to session.delete() an object which is not persistent.

- [orm]

  session.update() and session.delete() raise an error when updating or deleting an instance that is already in the session with a different identity.

- [orm]

  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

- [orm]

  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.

- [orm]

  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.

- [orm]

  Fixed a truncation error when re-assigning a subset of a collection (obj.relation = obj.relation[1:])

  References: #834

- [orm]

  De-cruftified backref configuration code, backrefs which step on existing properties now raise an error

  References: #832

- [orm]

  Improved behavior of add_property() etc., fixed involving synonym/deferred.

  References: #831

- [orm]

  Fixed clear_mappers() behavior to better clean up after itself.

- [orm]

  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.

  References: #841

- [orm]

  Fixed __hash__ for association proxy- these collections are unhashable, just like their mutable Python counterparts.

- [orm]

  Added proxying of save_or_update, __contains__ and __iter__ methods for scoped sessions.

- [orm]

  fixed very hard-to-reproduce issue where by the FROM clause of Query could get polluted by certain generative calls

  References: #852

### sql

- [sql]

  the “shortname” keyword parameter on bindparam() has been deprecated.

- [sql]

  Added contains operator (generates a “LIKE %<other>%” clause).

- [sql]

  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).

- [sql]

  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.

- [sql]

  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

  References: #819

- [sql]

  Removed regular expression step from most statement compilations. Also fixes

  References: #833

- [sql]

  Fixed empty (zero column) sqlite inserts, allowing inserts on autoincrementing single column tables.

- [sql]

  Fixed expression translation of text() clauses; this repairs various ORM scenarios where literal text is used for SQL expressions

- [sql]

  Removed ClauseParameters object; compiled.params returns a regular dictionary now, as well as result.last_inserted_params() / last_updated_params().

- [sql]

  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

- [sql]

  func. objects can be pickled/unpickled

  References: #844

- [sql]

  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.

- [sql]

  Added a field (“info”) for storing arbitrary data on schema items

  References: #573

- [sql]

  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.

- [sql]

  fixed the close() method on Transaction when using strategy=’threadlocal’

- [sql]

  fix to compiled bind parameters to not mistakenly populate None

  References: #853

- [sql]

  <Engine|Connection>._execute_clauseelement becomes a public method Connectable.execute_clauseelement

### misc

- [dialects]

  Added experimental support for MaxDB (versions >= 7.6.03.007 only).

- [dialects]

  oracle will now reflect “DATE” as an OracleDateTime column, not OracleDate

- [dialects]

  added awareness of schema name in oracle table_names() function, fixes metadata.reflect(schema=’someschema’)

  References: #847

- [dialects]

  MSSQL anonymous labels for selection of functions made deterministic

- [dialects]

  sqlite will reflect “DECIMAL” as a numeric column.

- [dialects]

  Made access dao detection more reliable

  References: #828

- [dialects]

  Renamed the Dialect attribute ‘preexecute_sequences’ to ‘preexecute_pk_sequences’. An attribute proxy is in place for out-of-tree dialects using the old name.

- [dialects]

  Added test coverage for unknown type reflection. Fixed sqlite/mysql handling of type reflection for unknown types.

- [dialects]

  Added REAL for mysql dialect (for folks exploiting the REAL_AS_FLOAT sql mode).

- [dialects]

  mysql Float, MSFloat and MSDouble constructed without arguments now produce no-argument DDL, e.g.’FLOAT’.

- [misc]

  Removed unused util.hash().

## 0.4.0

Released: Wed Oct 17 2007

- [no_tags]

  (see 0.4.0beta1 for the start of major changes against 0.3, as well as https://www.sqlalchemy.org/trac/wiki/WhatsNewIn04 )

- [no_tags]

  Added initial Sybase support (mxODBC so far)

  References: #785

- [no_tags]

  Added partial index support for PostgreSQL. Use the postgres_where keyword on the Index.

- [no_tags]

  string-based query param parsing/config file parser understands wider range of string values for booleans

  References: #817

- [no_tags]

  backref remove object operation doesn’t fail if the other-side collection doesn’t contain the item, supports noload collections

  References: #813

- [no_tags]

  removed __len__ from “dynamic” collection as it would require issuing a SQL “count()” operation, thus forcing all list evaluations to issue redundant SQL

  References: #818

- [no_tags]

  inline optimizations added to locate_dirty() which can greatly speed up repeated calls to flush(), as occurs with autoflush=True

  References: #816

- [no_tags]

  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.

- [no_tags]

  Firebird has supports_sane_rowcount and supports_sane_multi_rowcount set to False due to ticket #370 (right way).

- [no_tags]

  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.

- [no_tags]

  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.

- [no_tags]

  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.

- [no_tags]

  Fixed three- and multi-level select and deferred inheritance loading (i.e. abc inheritance with no select_table).

  References: #795

- [no_tags]

  Ident passed to id_chooser in shard.py always a list.

- [no_tags]

  The no-arg ResultProxy._row_processor() is now the class attribute _process_row.

- [no_tags]

  Added support for returning values from inserts and updates for PostgreSQL 8.2+.

  References: #797

- [no_tags]

  PG reflection, upon seeing the default schema name being used explicitly as the “schema” argument in a Table, will assume that this is 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.

- [no_tags]

  fixed sqlite reflection of BOOL/BOOLEAN

  References: #808

- [no_tags]

  Added support for UPDATE with LIMIT on mysql.

- [no_tags]

  null foreign key on a m2o doesn’t trigger a lazyload

  References: #803

- [no_tags]

  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

  References: #800

- [no_tags]

  fix to anonymous label generation of long table/column names

  References: #806

- [no_tags]

  Firebird dialect now uses SingletonThreadPool as poolclass.

- [no_tags]

  Firebird now uses dialect.preparer to format sequences names

- [no_tags]

  Fixed breakage with postgres and multiple two-phase transactions. Two-phase commits and rollbacks didn’t automatically end up with a new transaction as the usual dbapi commits/rollbacks do.

  References: #810

- [no_tags]

  Added an option to the _ScopedExt mapper extension to not automatically save new objects to session on object initialization.

- [no_tags]

  fixed Oracle non-ansi join syntax

- [no_tags]

  PickleType and Interval types (on db not supporting it natively) are now slightly faster.

- [no_tags]

  Added Float and Time types to Firebird (FBFloat and FBTime). Fixed BLOB SUB_TYPE for TEXT and Binary types.

- [no_tags]

  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.

## 0.4.0beta6

Released: Thu Sep 27 2007

- [no_tags]

  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.

- [no_tags]

  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). 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).

  References: #758

- [no_tags]

  added “FETCH” to the keywords detected by Postgres to indicate a result-row holding statement (i.e. in addition to “SELECT”).

- [no_tags]

  Added full list of SQLite reserved keywords so that they get escaped properly.

- [no_tags]

  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.

- [no_tags]

  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.

- [no_tags]

  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)”

  References: #560

- [no_tags]

  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.

- [no_tags]

  Added “schema” argument to Sequence; use this with Postgres /Oracle when the sequence is located in an alternate schema. Implements part of, should fix.

  References: #584, #761

- [no_tags]

  Fixed reflection of the empty string for mysql enums.

- [no_tags]

  Changed MySQL dialect to use the older LIMIT <offset>, <limit> syntax instead of LIMIT <l> OFFSET <o> for folks using 3.23.

  References: #794

- [no_tags]

  Added ‘passive_deletes=”all”’ flag to relation(), disables all nulling-out of foreign key attributes during a flush where the parent object is deleted.

- [no_tags]

  Column defaults and onupdates, executing inline, will add parenthesis for subqueries and other parenthesis-requiring expressions

- [no_tags]

  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.

  References: #793

- [no_tags]

  Fixes to ShardedSession to work with deferred columns.

  References: #771

- [no_tags]

  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.)

- [no_tags]

  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.. 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.

  References: #764

- [no_tags]

  Other tickets:,,.

  References: #728, #757, #768, #779

## 0.4.0beta5

no release date

- [no_tags]

  Connection pool fixes; the better performance of beta4 remains but fixes “connection overflow” and other bugs which were present (like).

  References: #754

- [no_tags]

  Fixed bugs in determining proper sync clauses from custom inherit conditions.

  References: #769

- [no_tags]

  Extended ‘engine_from_config’ coercion for QueuePool size / overflow.

  References: #763

- [no_tags]

  mysql views can be reflected again.

  References: #748

- [no_tags]

  AssociationProxy can now take custom getters and setters.

- [no_tags]

  Fixed malfunctioning BETWEEN in orm queries.

- [no_tags]

  Fixed OrderedProperties pickling

  References: #762

- [no_tags]

  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.

- [no_tags]

  Fixed PG executemany() behavior.

  References: #759

- [no_tags]

  postgres reflects tables with autoincrement=False for primary key columns which have no defaults.

- [no_tags]

  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().

- [fixed] [tickets]

  References: #742

- [fixed] [tickets]

  References: #748

- [fixed] [tickets]

  References: #760

- [fixed] [tickets]

  References: #762

- [fixed] [tickets]

  References: #763

## 0.4.0beta4

Released: Wed Aug 22 2007

- [no_tags]

  Tidied up what ends up in your namespace when you ‘from sqlalchemy import *’:

- [no_tags]

  ’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.

- [no_tags]

  Internal-ish classes like ClauseElement, FromClause, NullTypeEngine, etc., are also no longer imported into your namespace

- [no_tags]

  The ‘Smallinteger’ compatibility name (small i!) is no longer imported, but remains in schema.py for now. SmallInteger (big I!) is still imported.

- [no_tags]

  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.

- [no_tags]

  Fix to bind param processing such that “False” values (like blank strings) still get processed/encoded.

- [no_tags]

  Fix to select() “generative” behavior, such that calling column(), select_from(), correlate(), and with_prefix() does not modify the original select object

  References: #752

- [no_tags]

  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.

- [no_tags]

  Added session.prune(), trims away instances cached in a session that are no longer referenced elsewhere. (A utility for strong-ref identity maps).

- [no_tags]

  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.

- [no_tags]

  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.

- [no_tags]

  Modified SQL operator functions to be module-level operators, allowing SQL expressions to be pickleable.

  References: #735

- [no_tags]

  Small adjustment to mapper class.__init__ to allow for Py2.6 object.__init__() behavior.

- [no_tags]

  Fixed ‘prefix’ argument for select()

- [no_tags]

  Connection.begin() no longer accepts nested=True, this logic is now all in begin_nested().

- [no_tags]

  Fixes to new “dynamic” relation loader involving cascades

- [fixed] [tickets]

  References: #735

- [fixed] [tickets]

  References: #752

## 0.4.0beta3

Released: Thu Aug 16 2007

- [no_tags]

  SQL types optimization:

- [no_tags]

  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.

- [no_tags]

  General performance improvement of result set iteration is around 10-20%.

- [no_tags]

  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.

- [no_tags]

  Hooks added throughout base/sql/defaults to optimize the calling of bind param/result processors so that method call overhead is minimized.

- [no_tags]

  Support added for executemany() scenarios such that unneeded “last row id” logic doesn’t kick in, parameters aren’t excessively traversed.

- [no_tags]

  Added ‘inherit_foreign_keys’ arg to mapper().

- [no_tags]

  Added support for string date passthrough in sqlite.

- [fixed] [tickets]

  References: #738

- [fixed] [tickets]

  References: #739

- [fixed] [tickets]

  References: #743

- [fixed] [tickets]

  References: #744

## 0.4.0beta2

Released: Tue Aug 14 2007

### oracle

- [oracle] [improvements.]

  Auto-commit after LOAD DATA INFILE for mysql.

- [oracle] [improvements.]

  A rudimental SessionExtension class has been added, allowing user-defined functionality to take place at flush(), commit(), and rollback() boundaries.

- [oracle] [improvements.]

  Added engine_from_config() function for helping to create_engine() from an .ini style config.

- [oracle] [improvements.]

  base_mapper() becomes a plain attribute.

- [oracle] [improvements.]

  session.execute() and scalar() can search for a Table with which to bind from using the given ClauseElement.

- [oracle] [improvements.]

  Session automatically extrapolates tables from mappers with binds, also uses base_mapper so that inheritance hierarchies bind automatically.

- [oracle] [improvements.]

  Moved ClauseVisitor traversal back to inlined non-recursive.

### misc

- [fixed] [tickets]

  References: #730

- [fixed] [tickets]

  References: #732

- [fixed] [tickets]

  References: #733

- [fixed] [tickets]

  References: #734

## 0.4.0beta1

Released: Sun Aug 12 2007

### orm

- [orm]

  Speed! Along with recent speedups to ResultProxy, total number of function calls significantly reduced for large loads.

- [orm]

  test/perf/masseagerload.py reports 0.4 as having the fewest number of function calls across all SA versions (0.1, 0.2, and 0.3).

- [orm]

  New collection_class api and implementation. 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.

  References: #213

- [orm]

  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.

- [orm]

  __setitem__-like assignments now fire remove events for the existing value, if any.

- [orm]

  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.

- [orm]

  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.

- [orm]

  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.

- [orm]

  AttributeExtension moved to interfaces, and .delete is now .remove The event method signature has also been swapped around.

- [orm]

  Major overhaul for Query:

- [orm]

  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.

- [orm]

  Class-level properties are now usable as query elements… no more ‘.c.’! “Class.c.propname” is now superseded 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.

  References: #643

- [orm]

  Removed ancient query.select_by_attributename() capability.

- [orm]

  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”. Yhis 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

- [orm]

  Added query.populate_existing(), marks the query to reload all attributes and collections of all instances touched in the query, including eagerly-loaded entities.

  References: #660

- [orm]

  Added eagerload_all(), allows eagerload_all(‘x.y.z’) to specify eager loading of all properties in the given path.

- [orm]

  Major overhaul for Session:

- [orm]

  New function which “configures” a session called “sessionmaker()”. Send various keyword arguments to this function once, returns a new class which creates a Session against that stereotype.

- [orm]

  SessionTransaction removed from “public” API. You now can call begin()/ commit()/rollback() on the Session itself.

- [orm]

  Session also supports SAVEPOINT transactions; call begin_nested().

- [orm]

  Session supports two-phase commit behavior when vertically or horizontally partitioning (i.e., using more than one engine). Use twophase=True.

- [orm]

  Session flag “transactional=True” produces a session which always places itself into a transaction when first used. Upon commit(), rollback() or close(), the transaction ends; but begins again on the next usage.

- [orm]

  Session supports “autoflush=True”. This issues a flush() before each query. Use in conjunction with transactional, and you can just save()/update() and then query, the new objects will be there. Use commit() at the end (or flush() if non-transactional) to flush remaining changes.

- [orm]

  New scoped_session() function replaces SessionContext and assignmapper. Builds onto “sessionmaker()” concept to produce a class whose Session() construction returns the thread-local session. Or, call all Session methods as class methods, i.e. Session.save(foo); Session.commit(). just like the old “objectstore” days.

- [orm]

  Added new “binds” argument to Session to support configuration of multiple binds with sessionmaker() function.

- [orm]

  A rudimental SessionExtension class has been added, allowing user-defined functionality to take place at flush(), commit(), and rollback() boundaries.

- [orm]

  Query-based relation()s available with dynamic_loader(). This is a writable collection (supporting append() and remove()) which is also a live Query object when accessed for reads. Ideal for dealing with very large collections where only partial loading is desired.

- [orm]

  flush()-embedded inline INSERT/UPDATE expressions. Assign any SQL expression, like “sometable.c.column + 1”, to an instance’s attribute. Upon flush(), the mapper detects the expression and embeds it directly in the INSERT or UPDATE statement; the attribute gets deferred on the instance so it loads the new value the next time you access it.

- [orm]

  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.

  References: #618

- [orm]

  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 themselves are generated at compile time using a simple counting scheme now and are a lot easier on the eyes, as well as of course completely deterministic.

  References: #659

- [orm]

  Added composite column properties. This allows you to create a type which is represented by more than one column, when using the ORM. Objects of the new type are fully functional in query expressions, comparisons, query.get() clauses, etc. and act as though they are regular single-column scalars… except they’re not! Use the function composite(cls, *columns) inside of the mapper’s “properties” dict, and instances of cls will be created/mapped to a single attribute, comprised of the values corresponding to *columns.

  References: #211

- [orm]

  Improved support for custom column_property() attributes which feature correlated subqueries, works better with eager loading now.

- [orm]

  Primary key “collapse” behavior; the mapper will analyze all columns in its given selectable for primary key “equivalence”, that is, columns which are equivalent via foreign key relationship or via an explicit inherit_condition. primarily for joined-table inheritance scenarios where different named PK columns in inheriting tables should “collapse” into a single-valued (or fewer-valued) primary key. Fixes things like.

  References: #611

- [orm]

  Joined-table inheritance will now generate the primary key columns of all inherited classes against the root table of the join only. This implies that each row in the root table is distinct to a single instance. If for some rare reason this is not desirable, explicit primary_key settings on individual mappers will override it.

- [orm]

  When “polymorphic” flags are used with joined-table or single-table inheritance, all identity keys are generated against the root class of the inheritance hierarchy; this allows query.get() to work polymorphically using the same caching semantics as a non-polymorphic get. Note that this currently does not work with concrete inheritance.

- [orm]

  Secondary inheritance loading: polymorphic mappers can be constructed without a select_table argument. inheriting mappers whose tables were not represented in the initial load will issue a second SQL query immediately, once per instance (i.e. not very efficient for large lists), in order to load the remaining columns.

- [orm]

  Secondary inheritance loading can also move its second query into a column-level “deferred” load, via the “polymorphic_fetch” argument, which can be set to ‘select’ or ‘deferred’

- [orm]

  It’s now possible to map only a subset of available selectable columns onto mapper properties, using include_columns/exclude_columns..

  References: #696

- [orm]

  Added undefer_group() MapperOption, sets a set of “deferred” columns joined by a “group” to load as “undeferred”.

- [orm]

  Rewrite of the “deterministic alias name” logic to be part of the SQL layer, produces much simpler alias and label names more in the style of Hibernate

### sql

- [sql]

  Speed! Clause compilation as well as the mechanics of SQL constructs have been streamlined and simplified to a significant degree, for a 20-30% improvement of the statement construction/compilation overhead of 0.3.

- [sql]

  All “type” keyword arguments, such as those to bindparam(), column(), Column(), and func.<something>(), renamed to “type_”. Those objects still name their “type” attribute as “type”.

- [sql]

  case_sensitive=(True|False) setting removed from schema items, since checking this state added a lot of method call overhead and there was no decent reason to ever set it to False. Table and column names which are all lower case will be treated as case-insensitive (yes we adjust for Oracle’s UPPERCASE style too).

### extensions

- [extensions]

  proxyengine is temporarily removed, pending an actually working replacement.

- [extensions]

  SelectResults has been replaced by Query. SelectResults / SelectResultsExt still exist but just return a slightly modified Query object for backwards-compatibility. join_to() method from SelectResults isn’t present anymore, need to use join().

### mysql

- [mysql]

  Table and column names loaded via reflection are now Unicode.

- [mysql]

  All standard column types are now supported, including SET.

- [mysql]

  Table reflection can now be performed in as little as one round-trip.

- [mysql]

  ANSI and ANSI_QUOTES sql modes are now supported.

- [mysql]

  Indexes are now reflected.

### oracle

- [oracle]

  Very rudimental support for OUT parameters added; use sql.outparam(name, type) to set up an OUT parameter, just like bindparam(); after execution, values are available via result.out_parameters dictionary.

  References: #507

### misc

- [transactions]

  Added context manager (with statement) support for transactions.

- [transactions]

  Added support for two phase commit, works with mysql and postgres so far.

- [transactions]

  Added a subtransaction implementation that uses savepoints.

- [transactions]

  Added support for savepoints.

- [metadata]

  Tables can be reflected from the database en-masse without declaring them in advance. MetaData(engine, reflect=True) will load all tables present in the database, or use metadata.reflect() for finer control.

- [metadata]

  DynamicMetaData has been renamed to ThreadLocalMetaData

- [metadata]

  The ThreadLocalMetaData constructor now takes no arguments.

- [metadata]

  BoundMetaData has been removed- regular MetaData is equivalent

- [metadata]

  Numeric and Float types now have an “asdecimal” flag; defaults to True for Numeric, False for Float. When True, values are returned as decimal.Decimal objects; when False, values are returned as float(). The defaults of True/False are already the behavior for PG and MySQL’s DBAPI modules.

  References: #646

- [metadata]

  New SQL operator implementation which removes all hardcoded operators from expression structures and moves them into compilation; allows greater flexibility of operator compilation; for example, “+” compiles to “||” when used in a string context, or “concat(a,b)” on MySQL; whereas in a numeric context it compiles to “+”. Fixes.

  References: #475

- [metadata]

  ”Anonymous” alias and label names are now generated at SQL compilation time in a completely deterministic fashion… no more random hex IDs

- [metadata]

  Significant architectural overhaul to SQL elements (ClauseElement). All elements share a common “mutability” framework which allows a consistent approach to in-place modifications of elements as well as generative behavior. Improves stability of the ORM which makes heavy usage of mutations to SQL expressions.

- [metadata]

  select() and union()’s now have “generative” behavior. Methods like order_by() and group_by() return a new instance - the original instance is left unchanged. Non-generative methods remain as well.

- [metadata]

  The internals of select/union vastly simplified- all decision making regarding “is subquery” and “correlation” pushed to SQL generation phase. select() elements are now never mutated by their enclosing containers or by any dialect’s compilation process

  References: #52, #569

- [metadata]

  select(scalar=True) argument is deprecated; use select(..).as_scalar(). The resulting object obeys the full “column” interface and plays better within expressions.

- [metadata]

  Added select().with_prefix(‘foo’) allowing any set of keywords to be placed before the columns clause of the SELECT

  References: #504

- [metadata]

  Added array slice support to row[<index>]

  References: #686

- [metadata]

  Result sets make a better attempt at matching the DBAPI types present in cursor.description to the TypeEngine objects defined by the dialect, which are then used for result-processing. Note this only takes effect for textual SQL; constructed SQL statements always have an explicit type map.

- [metadata]

  Result sets from CRUD operations close their underlying cursor immediately and will also autoclose the connection if defined for the operation; this allows more efficient usage of connections for successive CRUD operations with less chance of “dangling connections”.

- [metadata]

  Column defaults and onupdate Python functions (i.e. passed to ColumnDefault) may take zero or one arguments; the one argument is the ExecutionContext, from which you can call “context.parameters[someparam]” to access the other bind parameter values affixed to the statement. The connection used for the execution is available as well so that you can pre-execute statements.

  References: #559

- [metadata]

  Added “explicit” create/drop/execute support for sequences (i.e. you can pass a “connectable” to each of those methods on Sequence).

- [metadata]

  Better quoting of identifiers when manipulating schemas.

- [metadata]

  Standardized the behavior for table reflection where types can’t be located; NullType is substituted instead, warning is raised.

- [metadata]

  ColumnCollection (i.e. the ‘c’ attribute on tables) follows dictionary semantics for “__contains__”

  References: #606

- [engines]

  Speed! The mechanics of result processing and bind parameter processing have been overhauled, streamlined and optimized to issue as little method calls as possible. Bench tests for mass INSERT and mass rowset iteration both show 0.4 to be over twice as fast as 0.3, using 68% fewer function calls.

- [engines]

  You can now hook into the pool lifecycle and run SQL statements or other logic at new each DBAPI connection, pool check-out and check-in.

- [engines]

  Connections gain a .properties collection, with contents scoped to the lifetime of the underlying DBAPI connection

- [engines]

  Removed auto_close_cursors and disallow_open_cursors arguments from Pool; reduces overhead as cursors are normally closed by ResultProxy and Connection.

- [postgres]

  Added PGArray datatype for using postgres array datatypes.