Result initial introduction

This builds on cc718cccc0bf8a01abdf4068c7ea4f3 which moved
RowProxy to Row, allowing Row to be more like a named tuple.

- KeyedTuple in ORM is replaced with Row

- ResultSetMetaData broken out into "simple" and "cursor" versions
  for ORM and Core, as well as LegacyCursor version.

- Row now has _mapping attribute that supplies full mapping behavior.
Row and SimpleRow both have named tuple behavior otherwise.
LegacyRow has some mapping features on the tuple which emit
deprecation warnings (e.g. keys(), values(), etc).   the biggest
change for mapping->tuple is the behavior of __contains__ which
moves from testing of "key in row" to "value in row".

- ResultProxy breaks into ResultProxy and FutureResult (interim),
the latter has the newer APIs.   Made available to dialects
using execution options.

- internal reflection methods and most tests move off of implicit
Row mapping behavior and move to row._mapping, result.mappings()
method using future result

- a new strategy system for cursor handling replaces the various
subclasses of RowProxy

- some execution context adjustments. We will leave EC in but
refined things like get_result_proxy() and out parameter handling.
Dialects for 1.4 will need to adjust from get_result_proxy()
to get_result_cursor_strategy(), if they are using this method

- out parameter handling now accommodated by get_out_parameter_values()
EC method.   Oracle changes for this.  external dialect for
DB2 for example will also need to adjust for this.

- deprecate case_insensitive flag for engine / result, this
feature is not used

mapping-methods on Row are deprecated, and replaced with
Row._mapping.<meth>, including:

   row.keys()  -> use row._mapping.keys()
   row.items()  -> use row._mapping.items()
   row.values() -> use row._mapping.values()
   key in row  -> use key in row._mapping
   int in row  -> use int < len(row)

Fixes: #4710
Fixes: #4878
Change-Id: Ieb9085e9bcff564359095b754da9ae0af55679f0

1 files changed, 26 insertions, 22 deletions

diff --git a/lib/sqlalchemy/orm/loading.py b/lib/sqlalchemy/orm/loading.py
index 617f027d9..193980e6c 100644
--- a/lib/sqlalchemy/orm/loading.py
+++ b/lib/sqlalchemy/orm/loading.py
@@ -28,6 +28,7 @@ from .util import aliased
 from .util import state_str
 from .. import exc as sa_exc
 from .. import util
+from ..engine import result_tuple
 from ..sql import util as sql_util
 
 
@@ -56,7 +57,7 @@ def instances(query, cursor, context):
                 )
 
     try:
-        (process, labels) = list(
+        (process, labels, extra) = list(
             zip(
                 *[
                     query_entity.row_processor(query, context, cursor)
@@ -66,7 +67,7 @@ def instances(query, cursor, context):
         )
 
         if not single_entity:
-            keyed_tuple = util.lightweight_named_tuple("result", labels)
+            keyed_tuple = result_tuple(labels, extra)
 
         while True:
             context.partials = {}
@@ -138,7 +139,9 @@ def merge_result(querylib, query, iterator, load=True):
             ]
             result = []
             keys = [ent._label_name for ent in query._entities]
-            keyed_tuple = util.lightweight_named_tuple("result", keys)
+            keyed_tuple = result_tuple(
+                keys, [ent.entities for ent in query._entities]
+            )
             for row in iterator:
                 newrow = list(row)
                 for i in mapped_entities:
@@ -190,7 +193,6 @@ def load_on_ident(
     query, key, refresh_state=None, with_for_update=None, only_load_props=None
 ):
     """Load the given identity key from the database."""
-
     if key is not None:
         ident = key[1]
         identity_token = key[2]
@@ -452,10 +454,19 @@ def _instance_processor(
     instance_state = attributes.instance_state
     instance_dict = attributes.instance_dict
     session_id = context.session.hash_key
-    version_check = context.version_check
     runid = context.runid
     identity_token = context.identity_token
 
+    version_check = context.version_check
+    if version_check:
+        version_id_col = mapper.version_id_col
+        if version_id_col is not None:
+            if adapter:
+                version_id_col = adapter.columns[version_id_col]
+            version_id_getter = result._getter(version_id_col)
+        else:
+            version_id_getter = None
+
     if not refresh_state and _polymorphic_from is not None:
         key = ("loader", path.path)
         if key in context.attributes and context.attributes[key].strategy == (
@@ -539,8 +550,10 @@ def _instance_processor(
                 currentload = not isnew
                 loaded_instance = False
 
-                if version_check and not currentload:
-                    _validate_version_id(mapper, state, dict_, row, adapter)
+                if version_check and version_id_getter and not currentload:
+                    _validate_version_id(
+                        mapper, state, dict_, row, version_id_getter
+                    )
 
             else:
                 # create a new instance
@@ -667,7 +680,7 @@ def _instance_processor(
         def ensure_no_pk(row):
             identitykey = (
                 identity_class,
-                tuple([row[column] for column in pk_cols]),
+                tuple_getter(row),
                 identity_token,
             )
             if not is_not_primary_key(identitykey[1]):
@@ -812,20 +825,11 @@ def _populate_partial(
     return to_load
 
 
-def _validate_version_id(mapper, state, dict_, row, adapter):
+def _validate_version_id(mapper, state, dict_, row, getter):
 
-    version_id_col = mapper.version_id_col
-
-    if version_id_col is None:
-        return
-
-    if adapter:
-        version_id_col = adapter.columns[version_id_col]
-
-    if (
-        mapper._get_state_attr_by_column(state, dict_, mapper.version_id_col)
-        != row[version_id_col]
-    ):
+    if mapper._get_state_attr_by_column(
+        state, dict_, mapper.version_id_col
+    ) != getter(row):
         raise orm_exc.StaleDataError(
             "Instance '%s' has version id '%s' which "
             "does not match database-loaded version id '%s'."
@@ -834,7 +838,7 @@ def _validate_version_id(mapper, state, dict_, row, adapter):
                 mapper._get_state_attr_by_column(
                     state, dict_, mapper.version_id_col
                 ),
-                row[version_id_col],
+                getter(row),
             )
         )