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, 9 insertions, 1 deletions

diff --git a/lib/sqlalchemy/sql/roles.py b/lib/sqlalchemy/sql/roles.py
index b861f721b..d0f4fef60 100644
--- a/lib/sqlalchemy/sql/roles.py
+++ b/lib/sqlalchemy/sql/roles.py
@@ -142,12 +142,20 @@ class AnonymizedFromClauseRole(StrictFromClauseRole):
 
 
 class CoerceTextStatementRole(SQLRole):
-    _role_name = "Executable SQL, text() construct, or string statement"
+    _role_name = "Executable SQL or text() construct"
+
+
+#    _executable_statement = None
 
 
 class StatementRole(CoerceTextStatementRole):
     _role_name = "Executable SQL or text() construct"
 
+    _is_future = False
+
+    def _get_plugin_compile_state_cls(self, name):
+        return None
+
 
 class ReturnsRowsRole(StatementRole):
     _role_name = (