Update README.md

README.md

@@ -4,6 +4,11 @@ license: odc-by
 
 # DuckDB datasets for (dump, id) querying on FineWeb 2
 
+This repo contains some DuckDB databases to check whether a given WARC UID exists in a FineWeb-2 dump. Usage example
+is given below, but note especially that if you are using URNs (likely, if you are working with CommonCrawl data),
+then you first have to extract the UID (the `id` column is of type `UUID` in the databases).
+
+
 ## Download
 
 All files: