copy_table_indexes

# File activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb, line 557
        def copy_table_indexes(from, to, rename = {}) #:nodoc:
          indexes(from).each do |index|
            name = index.name
            if to == "a#{from}"
              name = "t#{name}"
            elsif from == "a#{to}"
              name = name[1..-1]
            end

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

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