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or added/removed, now that data is obsolete.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, 25 insertions, 12 deletions

diff --git a/lib/sqlalchemy/orm/context.py b/lib/sqlalchemy/orm/context.py
index a16db66f6..588b83571 100644
--- a/lib/sqlalchemy/orm/context.py
+++ b/lib/sqlalchemy/orm/context.py
@@ -63,6 +63,8 @@ class QueryContext(object):
         "post_load_paths",
         "identity_token",
         "yield_per",
+        "loaders_require_buffering",
+        "loaders_require_uniquing",
     )
 
     class default_load_options(Options):
@@ -80,21 +82,23 @@ class QueryContext(object):
     def __init__(
         self,
         compile_state,
+        statement,
         session,
         load_options,
         execution_options=None,
         bind_arguments=None,
     ):
-
         self.load_options = load_options
         self.execution_options = execution_options or _EMPTY_DICT
         self.bind_arguments = bind_arguments or _EMPTY_DICT
         self.compile_state = compile_state
-        self.query = query = compile_state.select_statement
+        self.query = statement
         self.session = session
+        self.loaders_require_buffering = False
+        self.loaders_require_uniquing = False
 
         self.propagated_loader_options = {
-            o for o in query._with_options if o.propagate_to_loaders
+            o for o in statement._with_options if o.propagate_to_loaders
         }
 
         self.attributes = dict(compile_state.attributes)
@@ -237,6 +241,7 @@ class ORMCompileState(CompileState):
         )
         querycontext = QueryContext(
             compile_state,
+            statement,
             session,
             load_options,
             execution_options,
@@ -278,8 +283,6 @@ class ORMFromStatementCompileState(ORMCompileState):
     _has_orm_entities = False
     multi_row_eager_loaders = False
     compound_eager_adapter = None
-    loaders_require_buffering = False
-    loaders_require_uniquing = False
 
     @classmethod
     def create_for_statement(cls, statement_container, compiler, **kw):
@@ -386,8 +389,6 @@ class ORMSelectCompileState(ORMCompileState, SelectState):
     _has_orm_entities = False
     multi_row_eager_loaders = False
     compound_eager_adapter = None
-    loaders_require_buffering = False
-    loaders_require_uniquing = False
 
     correlate = None
     _where_criteria = ()
@@ -416,7 +417,14 @@ class ORMSelectCompileState(ORMCompileState, SelectState):
 
         self = cls.__new__(cls)
 
-        self.select_statement = select_statement
+        if select_statement._execution_options:
+            # execution options should not impact the compilation of a
+            # query, and at the moment subqueryloader is putting some things
+            # in here that we explicitly don't want stuck in a cache.
+            self.select_statement = select_statement._clone()
+            self.select_statement._execution_options = util.immutabledict()
+        else:
+            self.select_statement = select_statement
 
         # indicates this select() came from Query.statement
         self.for_statement = (
@@ -654,6 +662,8 @@ class ORMSelectCompileState(ORMCompileState, SelectState):
             )
             self._setup_with_polymorphics()
 
+        # entities will also set up polymorphic adapters for mappers
+        # that have with_polymorphic configured
         _QueryEntity.to_compile_state(self, query._raw_columns)
         return self
 
@@ -1810,10 +1820,12 @@ class ORMSelectCompileState(ORMCompileState, SelectState):
                 self._where_criteria += (single_crit,)
 
 
-def _column_descriptions(query_or_select_stmt):
-    ctx = ORMSelectCompileState._create_entities_collection(
-        query_or_select_stmt
-    )
+def _column_descriptions(query_or_select_stmt, compile_state=None):
+    if compile_state is None:
+        compile_state = ORMSelectCompileState._create_entities_collection(
+            query_or_select_stmt
+        )
+    ctx = compile_state
     return [
         {
             "name": ent._label_name,
@@ -2097,6 +2109,7 @@ class _MapperEntity(_QueryEntity):
             only_load_props = refresh_state = None
 
         _instance = loading._instance_processor(
+            self,
             self.mapper,
             context,
             result,