> If the index had cardinality metadata, it could jump directly to the leaf node containing the first row in the result set. It's difficult to maintain cardina

> If the index had cardinality metadata, it could jump directly to the leaf node containing the first row in the result set. It's difficult to maintain cardinality metadata in the face of MVCC, even for the table as a whole. Page-level or similar on an index would be even harder.