Wrap get_item inside bulk_operations internally, to cache query for active versions

[LMS-11402]

common/lib/xmodule/xmodule/modulestore/split_mongo/split.py

@@ -849,13 +849,14 @@ class SplitMongoModuleStore(SplitBulkWriteMixin, ModuleStoreWriteBase):
             # The supplied UsageKey is of the wrong type, so it can't possibly be stored in this modulestore.
             raise ItemNotFoundError(usage_key)
 
-        course = self._lookup_course(usage_key.course_key)
-        items = self._load_items(course, [BlockKey.from_usage_key(usage_key)], depth, lazy=True, **kwargs)
-        if len(items) == 0:
-            raise ItemNotFoundError(usage_key)
-        elif len(items) > 1:
-            log.debug("Found more than one item for '{}'".format(usage_key))
-        return items[0]
+        with self.bulk_operations(usage_key.course_key):
+            course = self._lookup_course(usage_key.course_key)
+            items = self._load_items(course, [BlockKey.from_usage_key(usage_key)], depth, lazy=True, **kwargs)
+            if len(items) == 0:
+                raise ItemNotFoundError(usage_key)
+            elif len(items) > 1:
+                log.debug("Found more than one item for '{}'".format(usage_key))
+            return items[0]
 
     def get_items(self, course_locator, settings=None, content=None, qualifiers=None, **kwargs):
         """

common/lib/xmodule/xmodule/modulestore/tests/test_mixed_modulestore.py

@@ -321,9 +321,9 @@ class TestMixedModuleStore(CourseComparisonTest):
     #   problem: find draft item, find all items pertinent to inheritance computation
     #   non-existent problem: find draft, find published
     # split:
-    #   problem: active_versions, structure, then active_versions again?
+    #   problem: active_versions, structure
     #   non-existent problem: ditto
-    @ddt.data(('draft', [2, 2], 0), ('split', [3, 3], 0))
+    @ddt.data(('draft', [2, 2], 0), ('split', [2, 2], 0))
     @ddt.unpack
     def test_get_item(self, default_ms, max_find, max_send):
         self.initdb(default_ms)
@@ -817,8 +817,8 @@ class TestMixedModuleStore(CourseComparisonTest):
             xml_store.create_course("org", "course", "run", self.user_id)
 
     # draft is 2: find out which ms owns course, get item
-    # split: find out which ms owns course, active_versions, structure, definition (definition s/b unnecessary unless lazy is false)
-    @ddt.data(('draft', 2, 0), ('split', 4, 0))
+    # split: active_versions, structure, definition (to load course wiki string)
+    @ddt.data(('draft', 2, 0), ('split', 3, 0))
     @ddt.unpack
     def test_get_course(self, default_ms, max_find, max_send):
         """