- Fixed bug where if an exception were thrown at the start of a

:class:`.Query` before it fetched results, particularly when
row processors can't be formed, the cursor would stay open with
results pending and not actually be closed.  This is typically only
an issue on an interpreter like Pypy where the cursor isn't
immediately GC'ed, and can in some circumstances lead to transactions/
locks being open longer than is desirable.
fixes #3285

3 files changed, 78 insertions, 34 deletions

diff --git a/doc/build/changelog/changelog_09.rst b/doc/build/changelog/changelog_09.rst
index e0f46eb66..81a26d187 100644
--- a/doc/build/changelog/changelog_09.rst
+++ b/doc/build/changelog/changelog_09.rst
@@ -15,6 +15,19 @@
     :version: 0.9.9
 
     .. change::
+        :tags: bug, orm, pypy
+        :versions: 1.0.0
+        :tickets: 3285
+
+        Fixed bug where if an exception were thrown at the start of a
+        :class:`.Query` before it fetched results, particularly when
+        row processors can't be formed, the cursor would stay open with
+        results pending and not actually be closed.  This is typically only
+        an issue on an interpreter like Pypy where the cursor isn't
+        immediately GC'ed, and can in some circumstances lead to transactions/
+        locks being open longer than is desirable.
+
+    .. change::
         :tags: change, mysql
         :versions: 1.0.0
         :tickets: 3275
diff --git a/lib/sqlalchemy/orm/loading.py b/lib/sqlalchemy/orm/loading.py
index 380afcdc7..fdc787545 100644
--- a/lib/sqlalchemy/orm/loading.py
+++ b/lib/sqlalchemy/orm/loading.py
@@ -42,41 +42,45 @@ def instances(query, cursor, context):
             def filter_fn(row):
                 return tuple(fn(x) for x, fn in zip(row, filter_fns))
 
-    (process, labels) = \
-        list(zip(*[
-            query_entity.row_processor(query,
-                                       context, cursor)
-            for query_entity in query._entities
-        ]))
-
-    if not single_entity:
-        keyed_tuple = util.lightweight_named_tuple('result', labels)
-
-    while True:
-        context.partials = {}
-
-        if query._yield_per:
-            fetch = cursor.fetchmany(query._yield_per)
-            if not fetch:
-                break
-        else:
-            fetch = cursor.fetchall()
+    try:
+        (process, labels) = \
+            list(zip(*[
+                query_entity.row_processor(query,
+                                           context, cursor)
+                for query_entity in query._entities
+            ]))
+
+        if not single_entity:
+            keyed_tuple = util.lightweight_named_tuple('result', labels)
+
+        while True:
+            context.partials = {}
+
+            if query._yield_per:
+                fetch = cursor.fetchmany(query._yield_per)
+                if not fetch:
+                    break
+            else:
+                fetch = cursor.fetchall()
 
-        if single_entity:
-            proc = process[0]
-            rows = [proc(row) for row in fetch]
-        else:
-            rows = [keyed_tuple([proc(row) for proc in process])
-                    for row in fetch]
+            if single_entity:
+                proc = process[0]
+                rows = [proc(row) for row in fetch]
+            else:
+                rows = [keyed_tuple([proc(row) for proc in process])
+                        for row in fetch]
 
-        if filtered:
-            rows = util.unique_list(rows, filter_fn)
+            if filtered:
+                rows = util.unique_list(rows, filter_fn)
 
-        for row in rows:
-            yield row
+            for row in rows:
+                yield row
 
-        if not query._yield_per:
-            break
+            if not query._yield_per:
+                break
+    except Exception as err:
+        cursor.close()
+        util.raise_from_cause(err)
 
 
 @util.dependencies("sqlalchemy.orm.query")
diff --git a/test/orm/test_loading.py b/test/orm/test_loading.py
index 97c08ea29..f86477ec2 100644
--- a/test/orm/test_loading.py
+++ b/test/orm/test_loading.py
@@ -1,13 +1,40 @@
 from . import _fixtures
 from sqlalchemy.orm import loading, Session, aliased
-from sqlalchemy.testing.assertions import eq_
+from sqlalchemy.testing.assertions import eq_, assert_raises
 from sqlalchemy.util import KeyedTuple
-
-# class InstancesTest(_fixtures.FixtureTest):
+from sqlalchemy.testing import mock
 # class GetFromIdentityTest(_fixtures.FixtureTest):
 # class LoadOnIdentTest(_fixtures.FixtureTest):
 # class InstanceProcessorTest(_fixture.FixtureTest):
 
+
+class InstancesTest(_fixtures.FixtureTest):
+    run_setup_mappers = 'once'
+    run_inserts = 'once'
+    run_deletes = None
+
+    @classmethod
+    def setup_mappers(cls):
+        cls._setup_stock_mapping()
+
+    def test_cursor_close_w_failed_rowproc(self):
+        User = self.classes.User
+        s = Session()
+
+        q = s.query(User)
+
+        ctx = q._compile_context()
+        cursor = mock.Mock()
+        q._entities = [
+            mock.Mock(row_processor=mock.Mock(side_effect=Exception("boom")))
+        ]
+        assert_raises(
+            Exception,
+            list, loading.instances(q, cursor, ctx)
+        )
+        assert cursor.close.called, "Cursor wasn't closed"
+
+
 class MergeResultTest(_fixtures.FixtureTest):
     run_setup_mappers = 'once'
     run_inserts = 'once'