callcount reductions and refinement for cached queries

This commit includes that we've removed the "_orm_query"
attribute from compile state as well as query context.
The attribute created reference cycles and also added
method call overhead.    As part of this change,
the interface for ORMExecuteState changes a bit, as well
as the interface for the horizontal sharding extension
which now deprecates the "query_chooser" callable
in favor of "execute_chooser", which receives the contextual
object.  This will also work more nicely when we implement
the new execution path for bulk updates and deletes.

Pre-merge execution options for statement, connection,
arguments all up front in Connection.  that way they
can be passed to the before_execute / after_execute events,
and the ExecutionContext doesn't have to merge as second
time.   Core execute is pretty close to 1.3 now.

baked wasn't using the new one()/first()/one_or_none() methods,
fixed that.

Convert non-buffered cursor strategy to be a stateless
singleton.  inline all the paths by which the strategy
gets chosen, oracle and SQL Server dialects make use of the
already-invoked post_exec() hook to establish the alternate
strategies, and this is actually much nicer than it was before.

Add caching to mapper instance processor for getters.

Identified a reference cycle per query that was showing
up as a lot of gc cleanup, fixed that.

After all that, performance not budging much.  Even
test_baked_query now runs with significantly fewer function
calls than 1.3, still 40% slower.

Basically something about the new patterns just makes
this slower and while I've walked a whole bunch of them
back, it hardly makes a dent.  that said, the performance
issues are relatively small, in the 20-40% time increase
range, and the new caching feature
does provide for regular ORM and Core queries that
are cached, and they are faster than non-cached.

Change-Id: I7b0b0d8ca550c05f79e82f75cd8eff0bbfade053

1 files changed, 5 insertions, 5 deletions

diff --git a/lib/sqlalchemy/sql/traversals.py b/lib/sqlalchemy/sql/traversals.py
index 482248ada..a38088a27 100644
--- a/lib/sqlalchemy/sql/traversals.py
+++ b/lib/sqlalchemy/sql/traversals.py
@@ -179,7 +179,7 @@ class HasCacheKey(object):
         if NO_CACHE in _anon_map:
             return None
         else:
-            return CacheKey(key, bindparams, self)
+            return CacheKey(key, bindparams)
 
     @classmethod
     def _generate_cache_key_for_object(cls, obj):
@@ -190,7 +190,7 @@ class HasCacheKey(object):
         if NO_CACHE in _anon_map:
             return None
         else:
-            return CacheKey(key, bindparams, obj)
+            return CacheKey(key, bindparams)
 
 
 class MemoizedHasCacheKey(HasCacheKey, HasMemoized):
@@ -199,13 +199,13 @@ class MemoizedHasCacheKey(HasCacheKey, HasMemoized):
         return HasCacheKey._generate_cache_key(self)
 
 
-class CacheKey(namedtuple("CacheKey", ["key", "bindparams", "statement"])):
+class CacheKey(namedtuple("CacheKey", ["key", "bindparams"])):
     def __hash__(self):
         """CacheKey itself is not hashable - hash the .key portion"""
 
         return None
 
-    def to_offline_string(self, statement_cache, parameters):
+    def to_offline_string(self, statement_cache, statement, parameters):
         """generate an "offline string" form of this :class:`.CacheKey`
 
         The "offline string" is basically the string SQL for the
@@ -222,7 +222,7 @@ class CacheKey(namedtuple("CacheKey", ["key", "bindparams", "statement"])):
 
         """
         if self.key not in statement_cache:
-            statement_cache[self.key] = sql_str = str(self.statement)
+            statement_cache[self.key] = sql_str = str(statement)
         else:
             sql_str = statement_cache[self.key]