validate_index_length!

# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1340
        def validate_index_length!(table_name, new_name, internal = false)
          max_index_length = internal ? index_name_length : allowed_index_name_length

          if new_name.length > max_index_length
            raise ArgumentError, "Index name '#{new_name}' on table '#{table_name}' is too long; the limit is #{allowed_index_name_length} characters"
          end
        end