Convert execution to move through Session

This patch replaces the ORM execution flow with a
single pathway through Session.execute() for all queries,
including Core and ORM.

Currently included is full support for ORM Query,
Query.from_statement(), select(), as well as the
baked query and horizontal shard systems.  Initial
changes have also been made to the dogpile caching
example, which like baked query makes use of a
new ORM-specific execution hook that replaces the
use of both QueryEvents.before_compile() as well
as Query._execute_and_instances() as the central
ORM interception hooks.

select() and Query() constructs alike can be passed to
Session.execute() where they will return ORM
results in a Results object.   This API is currently
used internally by Query.   Full support for
Session.execute()->results to behave in a fully
2.0 fashion will be in later changesets.

bulk update/delete with ORM support will also
be delivered via the update() and delete()
constructs, however these have not yet been adapted
to the new system and may follow in a subsequent
update.

Performance is also beginning to lag as of this
commit and some previous ones.   It is hoped that
a few central functions such as the coercions
functions can be rewritten in C to re-gain
performance.  Additionally, query caching
is now available and some subsequent patches
will attempt to cache more of the per-execution
work from the ORM layer, e.g. column getters
and adapters.

This patch also contains initial "turn on" of the
caching system enginewide via the query_cache_size
parameter to create_engine(). Still defaulting at
zero for "no caching".   The caching system still
needs adjustments in order to gain adequate performance.

Change-Id: I047a7ebb26aa85dc01f6789fac2bff561dcd555d

1 files changed, 5 insertions, 9 deletions

diff --git a/lib/sqlalchemy/util/_collections.py b/lib/sqlalchemy/util/_collections.py
index 9a832ba1b..605686494 100644
--- a/lib/sqlalchemy/util/_collections.py
+++ b/lib/sqlalchemy/util/_collections.py
@@ -97,17 +97,13 @@ class FacadeDict(ImmutableContainer, dict):
 
     def __new__(cls, *args):
         new = dict.__new__(cls)
-        dict.__init__(new, *args)
         return new
 
-    def __init__(self, *args):
-        pass
-
-    # note that currently, "copy()" is used as a way to get a plain dict
-    # from an immutabledict, while also allowing the method to work if the
-    # dictionary is already a plain dict.
-    # def copy(self):
-    #    return immutabledict.__new__(immutabledict, self)
+    def copy(self):
+        raise NotImplementedError(
+            "an immutabledict shouldn't need to be copied.  use dict(d) "
+            "if you need a mutable dictionary."
+        )
 
     def __reduce__(self):
         return FacadeDict, (dict(self),)