Add latest changes from gitlab-org/gitlab@13-5-stable-eev13.5.0-rc42

3 files changed, 73 insertions, 3 deletions

diff --git a/lib/gitlab/graphql/pagination/keyset/connection.rb b/lib/gitlab/graphql/pagination/keyset/connection.rb
index 17cd22d38ad..252f6371765 100644
--- a/lib/gitlab/graphql/pagination/keyset/connection.rb
+++ b/lib/gitlab/graphql/pagination/keyset/connection.rb
@@ -110,8 +110,7 @@ module Gitlab
               end
 
               if last
-                # grab one more than we need
-                paginated_nodes = sliced_nodes.last(limit_value + 1)
+                paginated_nodes = LastItems.take_items(sliced_nodes, limit_value + 1)
 
                 # there is an extra node, so there is a previous page
                 @has_previous_page = paginated_nodes.count > limit_value
diff --git a/lib/gitlab/graphql/pagination/keyset/last_items.rb b/lib/gitlab/graphql/pagination/keyset/last_items.rb
new file mode 100644
index 00000000000..45bf15236c1
--- /dev/null
+++ b/lib/gitlab/graphql/pagination/keyset/last_items.rb
@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Graphql
+    module Pagination
+      module Keyset
+        # This class handles the last(N) ActiveRecord call even if a special ORDER BY configuration is present.
+        # For the last(N) call, ActiveRecord calls reverse_order, however for some cases it raises
+        # ActiveRecord::IrreversibleOrderError error.
+        class LastItems
+          # rubocop: disable CodeReuse/ActiveRecord
+          def self.take_items(scope, count)
+            if custom_order = lookup_custom_reverse_order(scope.order_values)
+              items = scope.reorder(*custom_order).first(count) # returns a single record when count is nil
+              items.is_a?(Array) ? items.reverse : items
+            else
+              scope.last(count)
+            end
+          end
+          # rubocop: enable CodeReuse/ActiveRecord
+
+          # Detect special ordering and provide the reversed order
+          def self.lookup_custom_reverse_order(order_values)
+            if ordering_by_merged_at_and_mr_id_desc?(order_values)
+              [
+                Gitlab::Database.nulls_first_order('merge_request_metrics.merged_at', 'ASC'), # reversing the order
+                MergeRequest.arel_table[:id].asc
+              ]
+            elsif ordering_by_merged_at_and_mr_id_asc?(order_values)
+              [
+                Gitlab::Database.nulls_first_order('merge_request_metrics.merged_at', 'DESC'),
+                MergeRequest.arel_table[:id].asc
+              ]
+            end
+          end
+
+          def self.ordering_by_merged_at_and_mr_id_desc?(order_values)
+            order_values.size == 2 &&
+              order_values.first.to_s == Gitlab::Database.nulls_last_order('merge_request_metrics.merged_at', 'DESC') &&
+              order_values.last.is_a?(Arel::Nodes::Descending) &&
+              order_values.last.to_sql == MergeRequest.arel_table[:id].desc.to_sql
+          end
+
+          def self.ordering_by_merged_at_and_mr_id_asc?(order_values)
+            order_values.size == 2 &&
+              order_values.first.to_s == Gitlab::Database.nulls_last_order('merge_request_metrics.merged_at', 'ASC') &&
+              order_values.last.is_a?(Arel::Nodes::Descending) &&
+              order_values.last.to_sql == MergeRequest.arel_table[:id].desc.to_sql
+          end
+
+          private_class_method :ordering_by_merged_at_and_mr_id_desc?
+          private_class_method :ordering_by_merged_at_and_mr_id_asc?
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/graphql/pagination/keyset/order_info.rb b/lib/gitlab/graphql/pagination/keyset/order_info.rb
index f54695ddb9a..f3ce3a10703 100644
--- a/lib/gitlab/graphql/pagination/keyset/order_info.rb
+++ b/lib/gitlab/graphql/pagination/keyset/order_info.rb
@@ -94,6 +94,10 @@ module Gitlab
               [order_value.expr.expressions[0].name.to_s, order_value.direction, order_value.expr]
             elsif ordering_by_similarity?(order_value)
               ['similarity', order_value.direction, order_value.expr]
+            elsif ordering_by_case?(order_value)
+              ['case_order_value', order_value.direction, order_value.expr]
+            elsif ordering_by_array_position?(order_value)
+              ['array_position', order_value.direction, order_value.expr]
             else
               [order_value.expr.name, order_value.direction, nil]
             end
@@ -104,9 +108,19 @@ module Gitlab
             order_value.expr.is_a?(Arel::Nodes::NamedFunction) && order_value.expr&.name&.downcase == 'lower'
           end
 
+          # determine if ordering using ARRAY_POSITION, eg. "ORDER BY ARRAY_POSITION(Array[4,3,1,2]::smallint, state)"
+          def ordering_by_array_position?(order_value)
+            order_value.expr.is_a?(Arel::Nodes::NamedFunction) && order_value.expr&.name&.downcase == 'array_position'
+          end
+
           # determine if ordering using SIMILARITY scoring based on Gitlab::Database::SimilarityScore
           def ordering_by_similarity?(order_value)
-            order_value.to_sql.match?(/SIMILARITY\(.+\*/)
+            Gitlab::Database::SimilarityScore.order_by_similarity?(order_value)
+          end
+
+          # determine if ordering using CASE
+          def ordering_by_case?(order_value)
+            order_value.expr.is_a?(Arel::Nodes::Case)
           end
         end
       end