- The ``str()`` call for :class:`.Query` will now take into account

the :class:`.Engine` to which the :class:`.Session` is bound, when
generating the string form of the SQL, so that the actual SQL
that would be emitted to the database is shown, if possible.  Previously,
only the engine associated with the :class:`.MetaData` to which the
mappings are associated would be used, if present.  If
no bind can be located either on the :class:`.Session` or on
the :class:`.MetaData` to which the mappings are associated, then
the "default" dialect is used to render the SQL, as was the case
previously.  fixes #3081

1 files changed, 20 insertions, 7 deletions

diff --git a/lib/sqlalchemy/orm/query.py b/lib/sqlalchemy/orm/query.py
index e1b920bbb..6b808a701 100644
--- a/lib/sqlalchemy/orm/query.py
+++ b/lib/sqlalchemy/orm/query.py
@@ -2741,22 +2741,37 @@ class Query(object):
             self.session._autoflush()
         return self._execute_and_instances(context)
 
+    def __str__(self):
+        context = self._compile_context()
+        try:
+            bind = self._get_bind_args(
+                context, self.session.get_bind) if self.session else None
+        except sa_exc.UnboundExecutionError:
+            bind = None
+        return str(context.statement.compile(bind))
+
     def _connection_from_session(self, **kw):
-        conn = self.session.connection(
-            **kw)
+        conn = self.session.connection(**kw)
         if self._execution_options:
             conn = conn.execution_options(**self._execution_options)
         return conn
 
     def _execute_and_instances(self, querycontext):
-        conn = self._connection_from_session(
-            mapper=self._bind_mapper(),
-            clause=querycontext.statement,
+        conn = self._get_bind_args(
+            querycontext,
+            self._connection_from_session,
             close_with_result=True)
 
         result = conn.execute(querycontext.statement, self._params)
         return loading.instances(querycontext.query, result, querycontext)
 
+    def _get_bind_args(self, querycontext, fn, **kw):
+        return fn(
+            mapper=self._bind_mapper(),
+            clause=querycontext.statement,
+            **kw
+        )
+
     @property
     def column_descriptions(self):
         """Return metadata about the columns which would be
@@ -3358,8 +3373,6 @@ class Query(object):
                     sql.True_._ifnone(context.whereclause),
                     single_crit)
 
-    def __str__(self):
-        return str(self._compile_context().statement)
 
 from ..sql.selectable import ForUpdateArg