ar_order.rb

# This monkey patches rails to support proper joins
# current PR: https://github.com/rails/rails/pull/36531
module ActiveRecord
  module ConnectionAdapters
    module PostgreSQL
      module SchemaStatements
        def columns_for_distinct(columns, orders) # :nodoc:
          order_columns = orders.reject(&:blank?).map do |s|
                            # Convert Arel node to string
                            unless s.kind_of?(String)
                              if s.kind_of?(Arel::Nodes::Ordering)
                                s = s.expr
                                keep_order = true
                              end
                              if s.respond_to?(:to_sql)
                                s = s.to_sql
                              else # for Arel::Nodes::Attribute
                                engine = Arel::Table.engine
                                collector = Arel::Collectors::SQLString.new
                                collector = engine.connection.visitor.accept(s, collector)
                                s = collector.value
                              end
                            end
              # If we haven't already removed the order clause,
              # Remove any ASC/DESC modifiers
                            if keep_order
                              s
                            else
                              s.gsub(/\s+(?:ASC|DESC)\b/i, "")
                               .gsub(/\s+NULLS\s+(?:FIRST|LAST)\b/i, "")
                            end
                          end.reject(&:blank?).map.with_index { |column, i| "#{column} AS alias_#{i}" }

          (order_columns << super).join(", ")
        end
      end
    end
  end
end