Geo: Improve performance of LFS object queries

See discussion of various approaches at:
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/42423#note_418699307

ee/app/models/ee/lfs_object.rb

@@ -23,7 +23,7 @@ module EE
       def replicables_for_geo_node(primary_key_in, node = ::Gitlab::Geo.current_node)
         local_storage_only = !node.sync_object_storage
 
-        scope = node.lfs_objects.primary_key_in(primary_key_in)
+        scope = node.lfs_objects(primary_key_in: primary_key_in)
         scope = scope.with_files_stored_locally if local_storage_only
         scope
       end

ee/app/models/geo_node.rb

@@ -265,23 +265,17 @@ class GeoNode < ApplicationRecord
     designs.where(id: project_id).exists?
   end
 
-  def lfs_objects
-    return LfsObject.all unless selective_sync?
-
-    query = LfsObjectsProject.project_id_in(projects).select(:lfs_object_id).distinct
-    cte = Gitlab::SQL::CTE.new(:restricted_lfs_objects, query)
-    lfs_object_table = LfsObject.arel_table
-
-    inner_join_restricted_lfs_objects =
-      cte.table
-        .join(lfs_object_table, Arel::Nodes::InnerJoin)
-        .on(cte.table[:lfs_object_id].eq(lfs_object_table[:id]))
-        .join_sources
-
-    LfsObject
-      .with(cte.to_arel)
-      .from(cte.table)
-      .joins(inner_join_restricted_lfs_objects)
+  # @param primary_key_in [Range, LfsObject] arg to pass to primary_key_in scope
+  # @return [ActiveRecord::Relation<LfsObject>] scope of LfsObject filtered by selective sync settings and primary key arg
+  def lfs_objects(primary_key_in:)
+    return LfsObject.primary_key_in(primary_key_in) unless selective_sync?
+
+    ids = LfsObjectsProject.project_id_in(projects)
+                           .where(lfs_object_id: primary_key_in)
+                           .select(:lfs_object_id)
+                           .distinct
+
+    LfsObject.where(id: ids)
   end
 
   def projects

ee/changelogs/unreleased/mk-remove-cte-from-lfs-objects-query.yml

+---
+title: 'Geo: Improve performance of LFS objects queries'
+merge_request: 42423
+author:
+type: performance

ee/spec/models/geo_node_spec.rb

@@ -835,9 +835,11 @@ RSpec.describe GeoNode, :request_store, :geo, type: :model do
       create(:lfs_objects_project, project: project_broken_storage, lfs_object: lfs_object_5)
     end
 
+    subject(:lfs_objects) { node.lfs_objects(primary_key_in: 1..LfsObject.last.id) }
+
     context 'without selective sync' do
       it 'returns all projects without selective sync' do
-        expect(node.lfs_objects).to match_array([lfs_object_1, lfs_object_2, lfs_object_3, lfs_object_4, lfs_object_5])
+        expect(lfs_objects).to match_array([lfs_object_1, lfs_object_2, lfs_object_3, lfs_object_4, lfs_object_5])
       end
     end
 
@@ -847,14 +849,14 @@ RSpec.describe GeoNode, :request_store, :geo, type: :model do
       end
 
       it 'excludes LFS objects that are not in selectively synced projects' do
-        expect(node.lfs_objects).to match_array([lfs_object_1, lfs_object_2, lfs_object_3])
+        expect(lfs_objects).to match_array([lfs_object_1, lfs_object_2, lfs_object_3])
       end
 
       it 'excludes LFS objects from fork networks' do
         forked_project = create(:project, group: synced_group)
         create(:lfs_objects_project, project: forked_project, lfs_object: lfs_object_1)
 
-        expect(node.lfs_objects).to match_array([lfs_object_1, lfs_object_2, lfs_object_3])
+        expect(lfs_objects).to match_array([lfs_object_1, lfs_object_2, lfs_object_3])
       end
     end
 
@@ -864,14 +866,14 @@ RSpec.describe GeoNode, :request_store, :geo, type: :model do
       end
 
       it 'excludes LFS objects that are not in selectively synced shards' do
-        expect(node.lfs_objects).to match_array([lfs_object_5])
+        expect(lfs_objects).to match_array([lfs_object_5])
       end
 
       it 'excludes LFS objects from fork networks' do
         forked_project = create(:project, :broken_storage)
         create(:lfs_objects_project, project: forked_project, lfs_object: lfs_object_5)
 
-        expect(node.lfs_objects).to match_array([lfs_object_5])
+        expect(lfs_objects).to match_array([lfs_object_5])
       end
     end
   end