It's not about the number of lines. I was thinking that open-id would be more performant than db:open + root id match. I can create my custom index for root ids but since there is always a mechanism in place that handle ids I thought it could be useful to avoid duplicating features that already exist. I was going to see if I could use you ids in my docs instead by that would create issues for any export/import where ids might change in BaseX plus, the integer vs xml id format is blocking.