PYTHON-1591 - Deprecate Collection.parallel_scan

doc/changelog.rst

@@ -65,6 +65,8 @@ Deprecations:
   :meth:`~pymongo.mongo_client.MongoClient.list_database_names` instead.
 - Deprecated :meth:`~pymongo.database.Database.collection_names`. Use
   :meth:`~pymongo.database.Database.list_collection_names` instead.
+- Deprecated :meth:`~pymongo.collection.Collection.parallel_scan`. MongoDB 4.2
+  will remove the parallelCollectionScan command.
 
 Unavoidable breaking changes:
 

pymongo/collection.py

@@ -1450,7 +1450,7 @@ class Collection(common.BaseObject):
         return RawBatchCursor(self, *args, **kwargs)
 
     def parallel_scan(self, num_cursors, session=None, **kwargs):
-        """Scan this entire collection in parallel.
+        """**DEPRECATED**: Scan this entire collection in parallel.
 
         Returns a list of up to ``num_cursors`` cursors that can be iterated
         concurrently. As long as the collection is not modified during
@@ -1492,6 +1492,9 @@ class Collection(common.BaseObject):
 
         .. note:: Requires server version **>= 2.5.5**.
 
+        .. versionchanged:: 3.7
+           Deprecated.
+
         .. versionchanged:: 3.6
            Added ``session`` parameter.
 
@@ -1504,6 +1507,9 @@ class Collection(common.BaseObject):
            Removed support for arbitrary keyword arguments, since
            the parallelCollectionScan command has no optional arguments.
         """
+        warnings.warn("parallel_scan is deprecated. MongoDB 4.2 will remove "
+                      "the parallelCollectionScan command.",
+                      DeprecationWarning, stacklevel=2)
         cmd = SON([('parallelCollectionScan', self.__name),
                    ('numCursors', num_cursors)])
         cmd.update(kwargs)

test/test_collection.py

@@ -1662,6 +1662,8 @@ class TestCollection(IntegrationTest):
             self.assertTrue(cursor.alive)
 
     @client_context.require_no_mongos
+    @client_context.require_version_max(4, 1, 0)
+    @ignore_deprecations
     def test_parallel_scan(self):
         db = self.db
         db.drop_collection("test")
@@ -1688,7 +1690,9 @@ class TestCollection(IntegrationTest):
 
     @client_context.require_no_mongos
     @client_context.require_version_min(3, 3, 10)
+    @client_context.require_version_max(4, 1, 0)
     @client_context.require_test_commands
+    @ignore_deprecations
     def test_parallel_scan_max_time_ms(self):
             self.client.admin.command("configureFailPoint",
                                       "maxTimeAlwaysTimeOut",

test/test_session.py

@@ -320,6 +320,8 @@ class TestSession(IntegrationTest):
             (coll.aggregate, [[]], {}))
 
     @client_context.require_no_mongos
+    @client_context.require_version_max(4, 1, 0)
+    @ignore_deprecations
     def test_parallel_collection_scan(self):
         listener = self.listener
         client = self.client
@@ -771,7 +773,8 @@ class TestCausalConsistency(unittest.TestCase):
         self._test_reads(
             lambda coll, session: coll.inline_map_reduce(
                 'function() {}', 'function() {}', session=session))
-        if not client_context.is_mongos:
+        if (not client_context.is_mongos and
+                not client_context.version.at_least(4, 1, 0)):
             def scan(coll, session):
                 cursors = coll.parallel_scan(1, session=session)
                 for cur in cursors: