1 files changed, 76 insertions, 0 deletions
diff --git a/lib/gitlab/pagination/keyset/in_operator_optimization/order_by_columns.rb b/lib/gitlab/pagination/keyset/in_operator_optimization/order_by_columns.rb
new file mode 100644
index 00000000000..d8c69a74e6b
--- /dev/null
+++ b/lib/gitlab/pagination/keyset/in_operator_optimization/order_by_columns.rb
@@ -0,0 +1,76 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Pagination
+    module Keyset
+      module InOperatorOptimization
+        class OrderByColumns
+          include Enumerable
+
+          # This class exposes collection methods for the order by columns
+          #
+          # Example: by modelling the `issues.created_at ASC, issues.id ASC` ORDER BY
+          # SQL clause, this class will receive two ColumnOrderDefinition objects
+          def initialize(columns, arel_table)
+            @columns = columns.map do |column|
+              ColumnData.new(column.attribute_name, "order_by_columns_#{column.attribute_name}", arel_table)
+            end
+          end
+
+          def arel_columns
+            columns.map(&:arel_column)
+          end
+
+          def array_aggregated_columns
+            columns.map(&:array_aggregated_column)
+          end
+
+          def array_aggregated_column_names
+            columns.map(&:array_aggregated_column_name)
+          end
+
+          def original_column_names
+            columns.map(&:original_column_name)
+          end
+
+          def original_column_names_as_arel_string
+            columns.map { |c| Arel.sql(c.original_column_name) }
+          end
+
+          def original_column_names_as_tmp_tamble
+            temp_table = Arel::Table.new('record')
+            original_column_names.map { |c| temp_table[c] }
+          end
+
+          def cursor_values(table_name)
+            columns.each_with_object({}) do |column, hash|
+              hash[column.original_column_name] = Arel.sql("#{table_name}.#{column.array_aggregated_column_name}[position]")
+            end
+          end
+
+          def array_lookup_expressions_by_position(table_name)
+            columns.map do |column|
+              Arel.sql("#{table_name}.#{column.array_aggregated_column_name}[position]")
+            end
+          end
+
+          def replace_value_in_array_by_position_expressions
+            columns.map do |column|
+              name = "#{QueryBuilder::RECURSIVE_CTE_NAME}.#{column.array_aggregated_column_name}"
+              new_value = "next_cursor_values.#{column.original_column_name}"
+              "#{name}[:position_query.position-1]||#{new_value}||#{name}[position_query.position+1:]"
+            end
+          end
+
+          def each(&block)
+            columns.each(&block)
+          end
+
+          private
+
+          attr_reader :columns
+        end
+      end
+    end
+  end
+end