Try to measure new style caching in the ORM, take two

Supercedes: If78fbb557c6f2cae637799c3fec2cbc5ac248aaf

Trying to see if by making the cache key memoized, we
still can have the older "identity" form of caching
which is the cheapest of all, at the same time as the
newer "cache key each time" version that is not nearly
as cheap; but still much cheaper than no caching at all.

Also needed is a per-execution update of _keymap when
we invoke from a cached select, so that Column objects
that are anonymous or otherwise adapted will match up.
this is analogous to the adaption of bound parameters
from the cache key.

Adds test coverage for the keymap / construct_params()
 changes related to caching.  Also hones performance
to a large extent for statement construction and
cache key generation.

Also includes a new memoized attribute
approach that vastly simplifies the previous approach
of "group_expirable_memoized_property" and finally
integrates cleanly with _clone(), _generate(), etc.
no more hardcoding of attributes is needed, as well
as that most _reset_memoization() calls are no longer
needed as the reset is inherent in a _generate() call;
this also has dramatic performance improvements.

Change-Id: I95c560ffcbfa30b26644999412fb6a385125f663

1 files changed, 97 insertions, 10 deletions

diff --git a/test/sql/test_resultset.py b/test/sql/test_resultset.py
index f08248440..253ad7b38 100644
--- a/test/sql/test_resultset.py
+++ b/test/sql/test_resultset.py
@@ -29,9 +29,11 @@ from sqlalchemy.engine import default
 from sqlalchemy.engine import result as _result
 from sqlalchemy.engine import Row
 from sqlalchemy.ext.compiler import compiles
+from sqlalchemy.sql import ColumnElement
 from sqlalchemy.sql import expression
 from sqlalchemy.sql.selectable import TextualSelect
 from sqlalchemy.sql.sqltypes import NULLTYPE
+from sqlalchemy.sql.util import ClauseAdapter
 from sqlalchemy.testing import assert_raises
 from sqlalchemy.testing import assert_raises_message
 from sqlalchemy.testing import assertions
@@ -1391,16 +1393,20 @@ class KeyTargetingTest(fixtures.TablesTest):
 
     @classmethod
     def insert_data(cls):
-        cls.tables.keyed1.insert().execute(dict(b="a1", q="c1"))
-        cls.tables.keyed2.insert().execute(dict(a="a2", b="b2"))
-        cls.tables.keyed3.insert().execute(dict(a="a3", d="d3"))
-        cls.tables.keyed4.insert().execute(dict(b="b4", q="q4"))
-        cls.tables.content.insert().execute(type="t1")
-
-        if testing.requires.schemas.enabled:
-            cls.tables[
-                "%s.wschema" % testing.config.test_schema
-            ].insert().execute(dict(b="a1", q="c1"))
+        with testing.db.begin() as conn:
+            conn.execute(cls.tables.keyed1.insert(), dict(b="a1", q="c1"))
+            conn.execute(cls.tables.keyed2.insert(), dict(a="a2", b="b2"))
+            conn.execute(cls.tables.keyed3.insert(), dict(a="a3", d="d3"))
+            conn.execute(cls.tables.keyed4.insert(), dict(b="b4", q="q4"))
+            conn.execute(cls.tables.content.insert(), dict(type="t1"))
+
+            if testing.requires.schemas.enabled:
+                conn.execute(
+                    cls.tables[
+                        "%s.wschema" % testing.config.test_schema
+                    ].insert(),
+                    dict(b="a1", q="c1"),
+                )
 
     @testing.requires.schemas
     def test_keyed_accessor_wschema(self):
@@ -1712,6 +1718,87 @@ class KeyTargetingTest(fixtures.TablesTest):
         in_(stmt.selected_columns.keyed2_a, row._mapping)
         in_(stmt.selected_columns.keyed2_b, row._mapping)
 
+    def _adapt_result_columns_fixture_one(self):
+        keyed1 = self.tables.keyed1
+        stmt = (
+            select([keyed1.c.b, keyed1.c.q.label("foo")])
+            .apply_labels()
+            .subquery()
+        )
+
+        return select([stmt.c.keyed1_b, stmt.c.foo])
+
+    def _adapt_result_columns_fixture_two(self):
+        return text("select a AS keyed2_a, b AS keyed2_b from keyed2").columns(
+            keyed2_a=CHAR, keyed2_b=CHAR
+        )
+
+    def _adapt_result_columns_fixture_three(self):
+        keyed1 = self.tables.keyed1
+        stmt = select([keyed1.c.b, keyed1.c.q.label("foo")]).subquery()
+
+        return select([stmt.c.b, stmt.c.foo])
+
+    def _adapt_result_columns_fixture_four(self):
+        keyed1 = self.tables.keyed1
+
+        stmt1 = select([keyed1]).apply_labels()
+
+        a1 = keyed1.alias()
+        stmt2 = ClauseAdapter(a1).traverse(stmt1)
+
+        return stmt2
+
+    @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(self, connection, stmt_fn):
+        """test adaptation of a CursorResultMetadata to another one.
+
+
+        This copies the _keymap from one to the other in terms of the
+        selected columns of a target selectable.
+
+        This is used by the statement caching process to re-use the
+        CursorResultMetadata from the cached statement against the same
+        statement sent separately.
+
+        """
+
+        stmt1 = stmt_fn(self)
+        stmt2 = stmt_fn(self)
+
+        eq_(stmt1._generate_cache_key(), stmt2._generate_cache_key())
+
+        column_linkage = dict(
+            zip(stmt1.selected_columns, stmt2.selected_columns)
+        )
+
+        result = connection.execute(stmt1)
+
+        mock_context = Mock(
+            compiled=result.context.compiled, invoked_statement=stmt2
+        )
+        existing_metadata = result._metadata
+        adapted_metadata = existing_metadata._adapt_to_context(mock_context)
+
+        eq_(existing_metadata.keys, adapted_metadata.keys)
+
+        for k in existing_metadata._keymap:
+            if isinstance(k, ColumnElement) and k in column_linkage:
+                other_k = column_linkage[k]
+            else:
+                other_k = k
+
+            is_(
+                existing_metadata._keymap[k], adapted_metadata._keymap[other_k]
+            )
+        return stmt1, existing_metadata, stmt2, adapted_metadata
+
 
 class PositionalTextTest(fixtures.TablesTest):
     run_inserts = "once"