Deprecate textual column matching in Row

Deprecate query.instances() without a context

Deprecate string alias with contains_eager()

Deprecated the behavior by which a :class:`.Column` can be used as the key
in a result set row lookup, when that :class:`.Column` is not part of the
SQL selectable that is being selected; that is, it is only matched on name.
A deprecation warning is now emitted for this case.   Various ORM use
cases, such as those involving :func:`.text` constructs, have been improved
so that this fallback logic is avoided in most cases.

Calling the :meth:`.Query.instances` method without passing a
:class:`.QueryContext` is deprecated.   The original use case for this was
that a :class:`.Query` could yield ORM objects when given only the entities
to be selected as well as a DBAPI cursor object.  However, for this to work
correctly there is essential metadata that is passed from a SQLAlchemy
:class:`.ResultProxy` that is derived from the mapped column expressions,
which comes originally from the :class:`.QueryContext`.   To retrieve ORM
results from arbitrary SELECT statements, the :meth:`.Query.from_statement`
method should be used.

Note there is a small bump in test_zoomark because the
column._label is being calculated for each of those columns within
baseline_3_properties, as it is now part of the result map.
This label can't be calculated when the column is attached
to the table because it needs to have all the columns present
to do this correctly.  Another approach here would be to
pre-load the _label before the test runs however the zoomark
tests don't have an easy place for this to happen and it's
not really worth it.

Fixes: #4877
Fixes: #4719
Change-Id: I9bd29e72e6dce7c855651d69ba68d7383469acbc

1 files changed, 26 insertions, 3 deletions

diff --git a/lib/sqlalchemy/sql/compiler.py b/lib/sqlalchemy/sql/compiler.py
index 5e432a74c..1381e734c 100644
--- a/lib/sqlalchemy/sql/compiler.py
+++ b/lib/sqlalchemy/sql/compiler.py
@@ -490,6 +490,13 @@ class SQLCompiler(Compiled):
     True unless using an unordered TextualSelect.
     """
 
+    _loose_column_name_matching = False
+    """tell the result object that the SQL staement is textual, wants to match
+    up to Column objects, and may be using the ._label in the SELECT rather
+    than the base name.
+
+    """
+
     _numeric_binds = False
     """
     True if paramstyle is "numeric".  This paramstyle is trickier than
@@ -799,6 +806,7 @@ class SQLCompiler(Compiled):
         within_label_clause=False,
         within_columns_clause=False,
         render_label_as_label=None,
+        result_map_targets=(),
         **kw
     ):
         # only render labels within the columns clause
@@ -820,7 +828,7 @@ class SQLCompiler(Compiled):
                 add_to_result_map(
                     labelname,
                     label.name,
-                    (label, labelname) + label._alt_names,
+                    (label, labelname) + label._alt_names + result_map_targets,
                     label.type,
                 )
 
@@ -847,7 +855,12 @@ class SQLCompiler(Compiled):
         )
 
     def visit_column(
-        self, column, add_to_result_map=None, include_table=True, **kwargs
+        self,
+        column,
+        add_to_result_map=None,
+        include_table=True,
+        result_map_targets=(),
+        **kwargs
     ):
         name = orig_name = column.name
         if name is None:
@@ -859,7 +872,10 @@ class SQLCompiler(Compiled):
 
         if add_to_result_map is not None:
             add_to_result_map(
-                name, orig_name, (column, name, column.key), column.type
+                name,
+                orig_name,
+                (column, name, column.key, column._label) + result_map_targets,
+                column.type,
             )
 
         if is_literal:
@@ -948,6 +964,13 @@ class SQLCompiler(Compiled):
             self._ordered_columns = (
                 self._textual_ordered_columns
             ) = taf.positional
+
+            # enable looser result column matching when the SQL text links to
+            # Column objects by name only
+            self._loose_column_name_matching = not taf.positional and bool(
+                taf.column_args
+            )
+
             for c in taf.column_args:
                 self.process(
                     c,