target of :paramref:`.relationship.secondary` for the purposes of creating very complex :func:`.relationship` join conditions. The change includes adjustments to query joining, joined eager loading to not render a SELECT subquery, changes to lazy loading such that the "secondary" target is properly included in the SELECT, and changes to declarative to better support specification of a join() object with classes as targets.
:class:`.DeferredReflection` to define classes pending for reflection, if some subset of those classes were discarded before the :meth:`.DeferredReflection.prepare` method were called to reflect and map the class, a strong reference to the class would remain held within the declarative internals. This internal collection of "classes to map" now uses weak references against the classes themselves.
attribute on declarative to simply refer directly to an :class:`.InstrumentedAttribute` on a superclass or on the class itself, and it acts more or less like a synonym; in 0.9, this fails to set up enough bookkeeping to keep up with the more liberalized backref logic from :ticket:`2789`. Even though this use case was never directly considered, it is now detected by declarative at the "setattr()" level as well as when setting up a subclass, and the mirrored/renamed attribute is now set up as a :func:`.synonym` instead. [ticket:2900]
:class:`.Column` is mapped multiple times under different properties (which typically should be a :func:`.synonym` instead) or if two or more :class:`.Column` objects are given the same name, raising a warning if this condition is detected. [ticket:2828]
doesn't resolve to a class or mapper has been corrected to work the same way as when a non-string arg is received, which indicates the name of the relationship which had the configurational error. [ticket:2888]
automatic reflection support for the "secondary" table referred to by a :func:`.relationship`. "secondary", when specified either as a string table name, or as a :class:`.Table` object with only a name and :class:`.MetaData` object will also be included in the reflection process when :meth:`.DeferredReflection.prepare` is called. [ticket:2865] - clsregistry._resolver() now uses a stateful _class_resolver() class in order to handle the work of mapping strings to objects. This is to provide for simpler extensibility, namely a ._resolvers collection of ad-hoc name resolution functions; the DeferredReflection class adds its own resolver here in order to handle relationship(secondary) names which generate new Table objects.
as the string name of a class or other argument within declarative using :func:`.relationship`.
instead of relying upon various ``quote=True`` flags being passed around, these flags are converted into rich string objects with quoting information included at the point at which they are passed to common schema constructs like :class:`.Table`, :class:`.Column`, etc. This solves the issue of various methods that don't correctly honor the "quote" flag such as :meth:`.Engine.has_table` and related methods. The :class:`.quoted_name` object is a string subclass that can also be used explicitly if needed; the object will hold onto the quoting preferences passed and will also bypass the "name normalization" performed by dialects that standardize on uppercase symbols, such as Oracle, Firebird and DB2. The upshot is that the "uppercase" backends can now work with force-quoted names, such as lowercase-quoted names and new reserved words. [ticket:2812]
- rework the event system so that event modules load after their targets, dependencies are reversed - create an improved strategy lookup system for the ORM - rework the ORM to have very few import cycles - move out "importlater" to just util.dependency - other tricks to cross-populate modules in as clear a way as possible
by name in a string argument used with ``order_by``, ``primaryjoin``, or similar in :func:`.relationship`, in addition to column-bound attributes. [ticket:2761]