Turn on caching everywhere, add logging

A variety of caching issues found by running
all tests with statement caching turned on.

The cache system now has a more conservative approach where
any subclass of a SQL element will by default invalidate
the cache key unless it adds the flag inherit_cache=True
at the class level, or if it implements its own caching.

Add working caching to a few elements that were
omitted previously; fix some caching implementations
to suit lesser used edge cases such as json casts
and array slices.

Refine the way BaseCursorResult and CursorMetaData
interact with caching; to suit cases like Alembic
modifying table structures, don't cache the
cursor metadata if it were created against a
cursor.description using non-positional matching,
e.g. "select *".   if a table re-ordered its columns
or added/removed, now that data is obsolete.

Additionally we have to adapt the cursor metadata
_keymap regardless of if we just processed
cursor.description, because if we ran against
a cached SQLCompiler we won't have the right
columns in _keymap.

Other refinements to how and when we do this
adaption as some weird cases
were exposed in the Postgresql dialect,
a text() construct that names just one column that
is not actually in the statement.   Fixed that
also as it looks like a cut-and-paste artifact
that doesn't actually affect anything.

Various issues with re-use of compiled result maps
and cursor metadata in conjunction with tables being
changed, such as change in order of columns.

mappers can be cleared but the class remains, meaning
a mapper has to use itself as the cache key not the class.

lots of bound parameter / literal issues, due to Alembic
creating a straight subclass of bindparam that renders
inline directly.   While we can update Alembic to not
do this, we have to assume other people might be doing
this, so bindparam() implements the inherit_cache=True
logic as well that was a bit involved.

turn on cache stats in logging.

Includes a fix to subqueryloader which moves all setup to
the create_row_processor() phase and elminates any storage
within the compiled context.   This includes some changes
to create_row_processor() signature and a revising of the
technique used to determine if the loader can participate
in polymorphic queries, which is also applied to
selectinloading.

DML update.values() and ordered_values() now coerces the
keys as we have tests that pass an arbitrary class here
which only includes __clause_element__(), so the
key can't be cached unless it is coerced.  this in turn
changed how composite attributes support bulk update
to use the standard approach of ClauseElement with
annotations that are parsed in the ORM context.

memory profiling successfully caught that the Session
from Query was getting passed into _statement_20()
so that was a big win for that test suite.

Apparently Compiler had .execute() and .scalar() methods
stuck on it, these date back to version 0.4 and there
was a single test in the PostgreSQL dialect tests
that exercised it for no apparent reason.   Removed
these methods as well as the concept of a Compiler
holding onto a "bind".

Fixes: #5386

Change-Id: I990b43aab96b42665af1b2187ad6020bee778784

1 files changed, 112 insertions, 17 deletions

diff --git a/lib/sqlalchemy/sql/traversals.py b/lib/sqlalchemy/sql/traversals.py
index 68281f33d..ed0bfa27a 100644
--- a/lib/sqlalchemy/sql/traversals.py
+++ b/lib/sqlalchemy/sql/traversals.py
@@ -19,6 +19,7 @@ NO_CACHE = util.symbol("no_cache")
 CACHE_IN_PLACE = util.symbol("cache_in_place")
 CALL_GEN_CACHE_KEY = util.symbol("call_gen_cache_key")
 STATIC_CACHE_KEY = util.symbol("static_cache_key")
+PROPAGATE_ATTRS = util.symbol("propagate_attrs")
 ANON_NAME = util.symbol("anon_name")
 
 
@@ -31,10 +32,74 @@ def compare(obj1, obj2, **kw):
     return strategy.compare(obj1, obj2, **kw)
 
 
+def _preconfigure_traversals(target_hierarchy):
+
+    stack = [target_hierarchy]
+    while stack:
+        cls = stack.pop()
+        stack.extend(cls.__subclasses__())
+
+        if hasattr(cls, "_traverse_internals"):
+            cls._generate_cache_attrs()
+            _copy_internals.generate_dispatch(
+                cls,
+                cls._traverse_internals,
+                "_generated_copy_internals_traversal",
+            )
+            _get_children.generate_dispatch(
+                cls,
+                cls._traverse_internals,
+                "_generated_get_children_traversal",
+            )
+
+
 class HasCacheKey(object):
     _cache_key_traversal = NO_CACHE
     __slots__ = ()
 
+    @classmethod
+    def _generate_cache_attrs(cls):
+        """generate cache key dispatcher for a new class.
+
+        This sets the _generated_cache_key_traversal attribute once called
+        so should only be called once per class.
+
+        """
+        inherit = cls.__dict__.get("inherit_cache", False)
+
+        if inherit:
+            _cache_key_traversal = getattr(cls, "_cache_key_traversal", None)
+            if _cache_key_traversal is None:
+                try:
+                    _cache_key_traversal = cls._traverse_internals
+                except AttributeError:
+                    cls._generated_cache_key_traversal = NO_CACHE
+                    return NO_CACHE
+
+            # TODO: wouldn't we instead get this from our superclass?
+            # also, our superclass may not have this yet, but in any case,
+            # we'd generate for the superclass that has it.   this is a little
+            # more complicated, so for the moment this is a little less
+            # efficient on startup but simpler.
+            return _cache_key_traversal_visitor.generate_dispatch(
+                cls, _cache_key_traversal, "_generated_cache_key_traversal"
+            )
+        else:
+            _cache_key_traversal = cls.__dict__.get(
+                "_cache_key_traversal", None
+            )
+            if _cache_key_traversal is None:
+                _cache_key_traversal = cls.__dict__.get(
+                    "_traverse_internals", None
+                )
+                if _cache_key_traversal is None:
+                    cls._generated_cache_key_traversal = NO_CACHE
+                    return NO_CACHE
+
+            return _cache_key_traversal_visitor.generate_dispatch(
+                cls, _cache_key_traversal, "_generated_cache_key_traversal"
+            )
+
     @util.preload_module("sqlalchemy.sql.elements")
     def _gen_cache_key(self, anon_map, bindparams):
         """return an optional cache key.
@@ -72,14 +137,18 @@ class HasCacheKey(object):
         else:
             id_ = None
 
-        _cache_key_traversal = self._cache_key_traversal
-        if _cache_key_traversal is None:
-            try:
-                _cache_key_traversal = self._traverse_internals
-            except AttributeError:
-                _cache_key_traversal = NO_CACHE
+        try:
+            dispatcher = self.__class__.__dict__[
+                "_generated_cache_key_traversal"
+            ]
+        except KeyError:
+            # most of the dispatchers are generated up front
+            # in sqlalchemy/sql/__init__.py ->
+            # traversals.py-> _preconfigure_traversals().
+            # this block will generate any remaining dispatchers.
+            dispatcher = self.__class__._generate_cache_attrs()
 
-        if _cache_key_traversal is NO_CACHE:
+        if dispatcher is NO_CACHE:
             if anon_map is not None:
                 anon_map[NO_CACHE] = True
             return None
@@ -87,19 +156,13 @@ class HasCacheKey(object):
         result = (id_, self.__class__)
 
         # inline of _cache_key_traversal_visitor.run_generated_dispatch()
-        try:
-            dispatcher = self.__class__.__dict__[
-                "_generated_cache_key_traversal"
-            ]
-        except KeyError:
-            dispatcher = _cache_key_traversal_visitor.generate_dispatch(
-                self, _cache_key_traversal, "_generated_cache_key_traversal"
-            )
 
         for attrname, obj, meth in dispatcher(
             self, _cache_key_traversal_visitor
         ):
             if obj is not None:
+                # TODO: see if C code can help here as Python lacks an
+                # efficient switch construct
                 if meth is CACHE_IN_PLACE:
                     # cache in place is always going to be a Python
                     # tuple, dict, list, etc. so we can do a boolean check
@@ -116,6 +179,15 @@ class HasCacheKey(object):
                         attrname,
                         obj._gen_cache_key(anon_map, bindparams),
                     )
+                elif meth is PROPAGATE_ATTRS:
+                    if obj:
+                        result += (
+                            attrname,
+                            obj["compile_state_plugin"],
+                            obj["plugin_subject"]._gen_cache_key(
+                                anon_map, bindparams
+                            ),
+                        )
                 elif meth is InternalTraversal.dp_annotations_key:
                     # obj is here is the _annotations dict.   however,
                     # we want to use the memoized cache key version of it.
@@ -332,6 +404,8 @@ class _CacheKey(ExtendedInternalTraversal):
     visit_type = STATIC_CACHE_KEY
     visit_anon_name = ANON_NAME
 
+    visit_propagate_attrs = PROPAGATE_ATTRS
+
     def visit_inspectable(self, attrname, obj, parent, anon_map, bindparams):
         return (attrname, inspect(obj)._gen_cache_key(anon_map, bindparams))
 
@@ -445,10 +519,16 @@ class _CacheKey(ExtendedInternalTraversal):
     def visit_setup_join_tuple(
         self, attrname, obj, parent, anon_map, bindparams
     ):
+        is_legacy = "legacy" in attrname
+
         return tuple(
             (
-                target._gen_cache_key(anon_map, bindparams),
-                onclause._gen_cache_key(anon_map, bindparams)
+                target
+                if is_legacy and isinstance(target, str)
+                else target._gen_cache_key(anon_map, bindparams),
+                onclause
+                if is_legacy and isinstance(onclause, str)
+                else onclause._gen_cache_key(anon_map, bindparams)
                 if onclause is not None
                 else None,
                 from_._gen_cache_key(anon_map, bindparams)
@@ -711,6 +791,11 @@ class _CopyInternals(InternalTraversal):
             for sequence in element
         ]
 
+    def visit_propagate_attrs(
+        self, attrname, parent, element, clone=_clone, **kw
+    ):
+        return element
+
 
 _copy_internals = _CopyInternals()
 
@@ -782,6 +867,9 @@ class _GetChildren(InternalTraversal):
     def visit_dml_multi_values(self, element, **kw):
         return ()
 
+    def visit_propagate_attrs(self, element, **kw):
+        return ()
+
 
 _get_children = _GetChildren()
 
@@ -916,6 +1004,13 @@ class TraversalComparatorStrategy(InternalTraversal, util.MemoizedSlots):
         ):
             return COMPARE_FAILED
 
+    def visit_propagate_attrs(
+        self, attrname, left_parent, left, right_parent, right, **kw
+    ):
+        return self.compare_inner(
+            left.get("plugin_subject", None), right.get("plugin_subject", None)
+        )
+
     def visit_has_cache_key_list(
         self, attrname, left_parent, left, right_parent, right, **kw
     ):