From 9dc93a4519d9d5d7be48ff274127136236a3adb3 Mon Sep 17 00:00:00 2001
From: GitLab Bot <gitlab-bot@gitlab.com>
Date: Tue, 20 Apr 2021 23:50:22 +0000
Subject: Add latest changes from gitlab-org/gitlab@13-11-stable-ee

---
 lib/gitlab/object_hierarchy.rb | 46 ++++++++++++++++++++++++++++++++++--------
 1 file changed, 38 insertions(+), 8 deletions(-)

(limited to 'lib/gitlab/object_hierarchy.rb')

diff --git a/lib/gitlab/object_hierarchy.rb b/lib/gitlab/object_hierarchy.rb
index b1a1045a1f0..9a74266693b 100644
--- a/lib/gitlab/object_hierarchy.rb
+++ b/lib/gitlab/object_hierarchy.rb
@@ -68,13 +68,22 @@ module Gitlab
         expose_depth = hierarchy_order.present?
         hierarchy_order ||= :asc
 
-        recursive_query = base_and_ancestors_cte(upto, hierarchy_order).apply_to(model.all).distinct
-
         # if hierarchy_order is given, the calculated `depth` should be present in SELECT
         if expose_depth
+          recursive_query = base_and_ancestors_cte(upto, hierarchy_order).apply_to(model.all).distinct
           read_only(model.from(Arel::Nodes::As.new(recursive_query.arel, objects_table)).order(depth: hierarchy_order))
         else
-          read_only(remove_depth_and_maintain_order(recursive_query, hierarchy_order: hierarchy_order))
+          recursive_query = base_and_ancestors_cte(upto).apply_to(model.all)
+
+          if skip_ordering?
+            recursive_query = recursive_query.distinct
+          else
+            recursive_query = recursive_query.reselect(*recursive_query.arel.projections, 'ROW_NUMBER() OVER () as depth').distinct
+            recursive_query = model.from(Arel::Nodes::As.new(recursive_query.arel, objects_table))
+            recursive_query = remove_depth_and_maintain_order(recursive_query, hierarchy_order: hierarchy_order)
+          end
+
+          read_only(recursive_query)
         end
       else
         recursive_query = base_and_ancestors_cte(upto, hierarchy_order).apply_to(model.all)
@@ -93,12 +102,21 @@ module Gitlab
     def base_and_descendants(with_depth: false)
       if use_distinct?
         # Always calculate `depth`, remove it later if with_depth is false
-        base_cte = base_and_descendants_cte(with_depth: true).apply_to(model.all).distinct
-
         if with_depth
-          read_only(model.from(Arel::Nodes::As.new(recursive_query.arel, objects_table)).order(depth: :asc))
+          base_cte = base_and_descendants_cte(with_depth: true).apply_to(model.all).distinct
+          read_only(model.from(Arel::Nodes::As.new(base_cte.arel, objects_table)).order(depth: :asc))
         else
-          read_only(remove_depth_and_maintain_order(base_cte, hierarchy_order: :asc))
+          base_cte = base_and_descendants_cte.apply_to(model.all)
+
+          if skip_ordering?
+            base_cte = base_cte.distinct
+          else
+            base_cte = base_cte.reselect(*base_cte.arel.projections, 'ROW_NUMBER() OVER () as depth').distinct
+            base_cte = model.from(Arel::Nodes::As.new(base_cte.arel, objects_table))
+            base_cte = remove_depth_and_maintain_order(base_cte, hierarchy_order: :asc)
+          end
+
+          read_only(base_cte)
         end
       else
         read_only(base_and_descendants_cte(with_depth: with_depth).apply_to(model.all))
@@ -161,7 +179,19 @@ module Gitlab
 
     # Use distinct on the Namespace queries to avoid bad planner behavior in PG11.
     def use_distinct?
-      (model <= Namespace) && options[:use_distinct]
+      return unless model <= Namespace
+      # Global use_distinct_for_all_object_hierarchy takes precedence over use_distinct_in_object_hierarchy
+      return true if Feature.enabled?(:use_distinct_for_all_object_hierarchy)
+      return options[:use_distinct] if options.key?(:use_distinct)
+
+      false
+    end
+
+    # Skips the extra ordering when using distinct on the namespace queries
+    def skip_ordering?
+      return options[:skip_ordering] if options.key?(:skip_ordering)
+
+      false
     end
 
     # Remove the extra `depth` field using an INNER JOIN to avoid breaking UNION queries
-- 
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