# File lib/tapkit/access/adapters/openbase.rb, line 254
                def primary_keys_for_new_row( count, entity )
                        attrs = entity.primary_key_attributes
                        if attrs.size > 1 then return nil end

                        open
                        attr = attrs.first
                        column_name = attr.column_name

                        if (maxnum = @pk_cache[entity]) > 0 then
                                @pk_cache[entity] = maxnum + count
                                return _primary_keys(attr, maxnum, count)
                        end

                        sql =  "SELECT #{column_name} FROM #{entity.external_name}"
                        sql << " ORDER BY #{column_name} DESC RETURN RESULTS 1"

                        factory = @adapter_context.adapter.expression_factory
                        expr = factory.create entity
                        expr.statement = sql
                        result = evaluate expr
                        row = result.fetch

                        if row.nil? then
                                maxnum = 0
                        else
                                maxnum = row[0]
                        end

                        @pk_cache[entity] = maxnum + count
                        _primary_keys(attr, maxnum, count)
                end