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, 26 insertions, 1 deletions

diff --git a/examples/performance/short_selects.py b/examples/performance/short_selects.py
index 376f18f02..db8ab8789 100644
--- a/examples/performance/short_selects.py
+++ b/examples/performance/short_selects.py
@@ -13,6 +13,7 @@ from sqlalchemy import select
 from sqlalchemy import String
 from sqlalchemy.ext import baked
 from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.future import select as future_select
 from sqlalchemy.orm import deferred
 from sqlalchemy.orm import Session
 from . import Profiler
@@ -117,6 +118,20 @@ def test_core_new_stmt_each_time(n):
 
 
 @Profiler.profile
+def test_core_new_stmt_each_time_compiled_cache(n):
+    """test core, creating a new statement each time, but using the cache."""
+
+    compiled_cache = {}
+    with engine.connect().execution_options(
+        compiled_cache=compiled_cache
+    ) as conn:
+        for id_ in random.sample(ids, n):
+            stmt = select([Customer.__table__]).where(Customer.id == id_)
+            row = conn.execute(stmt).first()
+            tuple(row)
+
+
+@Profiler.profile
 def test_core_reuse_stmt(n):
     """test core, reusing the same statement (but recompiling each time)."""
 
@@ -132,8 +147,8 @@ def test_core_reuse_stmt(n):
 def test_core_reuse_stmt_compiled_cache(n):
     """test core, reusing the same statement + compiled cache."""
 
-    compiled_cache = {}
     stmt = select([Customer.__table__]).where(Customer.id == bindparam("id"))
+    compiled_cache = {}
     with engine.connect().execution_options(
         compiled_cache=compiled_cache
     ) as conn:
@@ -142,5 +157,15 @@ def test_core_reuse_stmt_compiled_cache(n):
             tuple(row)
 
 
+@Profiler.profile
+def test_core_just_statement_construct_plus_cache_key(n):
+    for i in range(n):
+        stmt = future_select(Customer.__table__).where(
+            Customer.id == bindparam("id")
+        )
+
+        stmt._generate_cache_key()
+
+
 if __name__ == "__main__":
     Profiler.main()