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, 17 insertions, 3 deletions

diff --git a/lib/sqlalchemy/sql/functions.py b/lib/sqlalchemy/sql/functions.py
index cedb76f55..6b1172eba 100644
--- a/lib/sqlalchemy/sql/functions.py
+++ b/lib/sqlalchemy/sql/functions.py
@@ -107,6 +107,7 @@ class FunctionElement(Executable, ColumnElement, FromClause):
                 roles.ExpressionElementRole,
                 c,
                 name=getattr(self, "name", None),
+                apply_propagate_attrs=self,
             )
             for c in clauses
         ]
@@ -749,7 +750,10 @@ class GenericFunction(util.with_metaclass(_GenericMeta, Function)):
         if parsed_args is None:
             parsed_args = [
                 coercions.expect(
-                    roles.ExpressionElementRole, c, name=self.name
+                    roles.ExpressionElementRole,
+                    c,
+                    name=self.name,
+                    apply_propagate_attrs=self,
                 )
                 for c in args
             ]
@@ -813,7 +817,12 @@ class ReturnTypeFromArgs(GenericFunction):
 
     def __init__(self, *args, **kwargs):
         args = [
-            coercions.expect(roles.ExpressionElementRole, c, name=self.name)
+            coercions.expect(
+                roles.ExpressionElementRole,
+                c,
+                name=self.name,
+                apply_propagate_attrs=self,
+            )
             for c in args
         ]
         kwargs.setdefault("type_", _type_from_args(args))
@@ -944,7 +953,12 @@ class array_agg(GenericFunction):
     type = sqltypes.ARRAY
 
     def __init__(self, *args, **kwargs):
-        args = [coercions.expect(roles.ExpressionElementRole, c) for c in args]
+        args = [
+            coercions.expect(
+                roles.ExpressionElementRole, c, apply_propagate_attrs=self
+            )
+            for c in args
+        ]
 
         default_array_type = kwargs.pop("_default_array_type", sqltypes.ARRAY)
         if "type_" not in kwargs: