- columns from Alias objects, when used to target result-row columns, must match exactly

  to the label used in the generated statement.  This is so searching for columns in a
  result row which match aliases won't accidentally match non-aliased columns.
  fixes errors which can arise in eager loading scenarios.

3 files changed, 25 insertions, 4 deletions

diff --git a/lib/sqlalchemy/engine/base.py b/lib/sqlalchemy/engine/base.py
index cc2ea6d5d..7e9d57d97 100644
--- a/lib/sqlalchemy/engine/base.py
+++ b/lib/sqlalchemy/engine/base.py
@@ -1287,10 +1287,19 @@ class ResultProxy(object):
             elif isinstance(key, basestring) and key.lower() in props:
                 rec = props[key.lower()]
             elif isinstance(key, expression.ColumnElement):
-                label = context.column_labels.get(key._label, key.name).lower()
-                if label in props:
-                    rec = props[label]
-
+                try:
+                    if getattr(key, '_exact_match', False):
+                        # exact match flag means the label must be present in the
+                        # generated column_labels
+                        label = context.column_labels[key._label].lower()
+                    else:
+                        # otherwise, fall back to the straight name of the column
+                        # if not in generated labels
+                        label = context.column_labels.get(key._label, key.name).lower()
+                    if label in props:
+                        rec = props[label]
+                except KeyError:
+                    pass
             if not "rec" in locals():
                 raise exceptions.NoSuchColumnError("Could not locate column in row for column '%s'" % (str(key)))
 
diff --git a/lib/sqlalchemy/orm/strategies.py b/lib/sqlalchemy/orm/strategies.py
index 8016673ff..f3a0029f5 100644
--- a/lib/sqlalchemy/orm/strategies.py
+++ b/lib/sqlalchemy/orm/strategies.py
@@ -615,6 +615,10 @@ class EagerLoader(AbstractRelationLoader):
                 selectcontext.stack.pop()
 
             selectcontext.stack.pop()
+
+            if self._should_log_debug:
+                self.logger.debug("Returning eager instance loader for %s" % str(self))
+
             return (execute, execute, None)
         else:
             if self._should_log_debug:
diff --git a/lib/sqlalchemy/sql/expression.py b/lib/sqlalchemy/sql/expression.py
index f7514fec9..dac5d7a74 100644
--- a/lib/sqlalchemy/sql/expression.py
+++ b/lib/sqlalchemy/sql/expression.py
@@ -2423,6 +2423,14 @@ class Alias(FromClause):
     def _get_from_objects(self, **modifiers):
         return [self]
 
+    def _proxy_column(self, column):
+        c = column._make_proxy(self)
+        # send a note to ResultProxy to not "approximate"
+        # this column based on its name when targeting result columns
+        # see test/sql/query.py QueryTest.test_exact_match
+        c._exact_match = True
+        return c
+
     bind = property(lambda s: s.selectable.bind)
 
 class _ColumnElementAdapter(ColumnElement):