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, 28 insertions, 1 deletions

diff --git a/test/sql/test_resultset.py b/test/sql/test_resultset.py
index 6c83697dc..0eff94635 100644
--- a/test/sql/test_resultset.py
+++ b/test/sql/test_resultset.py
@@ -1856,7 +1856,34 @@ class KeyTargetingTest(fixtures.TablesTest):
             is_(
                 existing_metadata._keymap[k], adapted_metadata._keymap[other_k]
             )
-        return stmt1, existing_metadata, stmt2, adapted_metadata
+
+    @testing.combinations(
+        _adapt_result_columns_fixture_one,
+        _adapt_result_columns_fixture_two,
+        _adapt_result_columns_fixture_three,
+        _adapt_result_columns_fixture_four,
+        argnames="stmt_fn",
+    )
+    def test_adapt_result_columns_from_cache(self, connection, stmt_fn):
+        stmt1 = stmt_fn(self)
+        stmt2 = stmt_fn(self)
+
+        cache = {}
+        result = connection._execute_20(
+            stmt1,
+            execution_options={"compiled_cache": cache, "future_result": True},
+        )
+        result.close()
+        assert cache
+
+        result = connection._execute_20(
+            stmt2,
+            execution_options={"compiled_cache": cache, "future_result": True},
+        )
+
+        row = result.first()
+        for col in stmt2.selected_columns:
+            assert col in row._mapping
 
 
 class PositionalTextTest(fixtures.TablesTest):