copy_table_indexes

# File activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb, line 585
        def copy_table_indexes(from, to, rename = {})
          indexes(from).each do |index|
            name = index.name
            if to == "a#{from}"
              name = "t#{name}"
            elsif from == "a#{to}"
              name = name[1..-1]
            end

            columns = index.columns
            if columns.is_a?(Array)
              to_column_names = columns(to).map(&:name)
              columns = columns.map { |c| rename[c] || c }.select do |column|
                to_column_names.include?(column)
              end
            end

            unless columns.empty?
              # index name can't be the same
              options = { name: name.gsub(/(^|_)(#{from})_/, "\\1#{to}_"), internal: true }
              options[:unique] = true if index.unique
              options[:where] = index.where if index.where
              options[:order] = index.orders if index.orders
              add_index(to, columns, **options)
            end
          end
        end