- flush() refactor merged from uow_nontree branch r3871-r3885

- topological.py cleaned up, presents three public facing functions which
return list/tuple based structures, without exposing any internals.  only
the third function returns the "hierarchical" structure.  when results
include "cycles" or "child" items, 2- or 3- tuples are used to represent
results.
- unitofwork uses InstanceState almost exclusively now.  new and deleted lists
are now dicts which ref the actual object to provide a strong ref for the
duration that they're in those lists.  IdentitySet is only used for the public
facing versions of "new" and "deleted".
- unitofwork topological sort no longer uses the "hierarchical" version of the sort
for the base sort, only for the "per-object" secondary sort where it still
helps to group non-dependent operations together and provides expected insert
order.  the default sort deals with UOWTasks in a straight list and is greatly
simplified.  Tests all pass but need to see if svilen's stuff still works,
one block of code in _sort_cyclical_dependencies() seems to not be needed anywhere
but i definitely put it there for a reason at some point; if not hopefully we
can derive more test coverage from that.
- the UOWEventHandler is only applied to object-storing attributes, not
scalar (i.e. column-based) ones.  cuts out a ton of overhead when setting
non-object based attributes.
- InstanceState also used throughout the flush process, i.e. dependency.py,
mapper.save_obj()/delete_obj(), sync.execute() all expect InstanceState objects
in most cases now.
- mapper/property cascade_iterator() takes InstanceState as its argument,
but still returns lists of object instances so that they are not dereferenced.
- a few tricks needed when dealing with InstanceState, i.e. when loading a list
of items that are possibly fresh from the DB, you *have* to get the actual objects
into a strong-referencing datastructure else they fall out of scope immediately.
dependency.py caches lists of dependent objects which it loads now (i.e. history
collections).
- AttributeHistory is gone, replaced by a function that returns a 3-tuple of
added, unchanged, deleted.  these collections still reference the object
instances directly for the strong-referencing reasons mentiontioned, but
it uses less IdentitySet logic to generate.

1 files changed, 5 insertions, 6 deletions

diff --git a/lib/sqlalchemy/engine/base.py b/lib/sqlalchemy/engine/base.py
index 45e4c036f..259909d47 100644
--- a/lib/sqlalchemy/engine/base.py
+++ b/lib/sqlalchemy/engine/base.py
@@ -320,6 +320,10 @@ class ExecutionContext(object):
       
     returns_rows
       True if the statement should return result rows
+
+    postfetch_cols
+     a list of Column objects for which a server-side default
+     or inline SQL expression value was fired off.  applies to inserts and updates.
       
     The Dialect should provide an ExecutionContext via the
     create_execution_context() method.  The `pre_exec` and `post_exec`
@@ -414,11 +418,6 @@ class ExecutionContext(object):
 
         raise NotImplementedError()
 
-    def postfetch_cols(self):
-        """return a list of Column objects for which a 'passive' server-side default
-        value was fired off.  applies to inserts and updates."""
-
-        raise NotImplementedError()
 
 class Compiled(object):
     """Represent a compiled SQL expression.
@@ -1481,7 +1480,7 @@ class ResultProxy(object):
 
         See ExecutionContext for details.
         """
-        return self.context.postfetch_cols()
+        return self.context.postfetch_cols
         
     def supports_sane_rowcount(self):
         """Return ``supports_sane_rowcount`` from the dialect.