IndexHandle

An index that has been defined, as the registry records it.

Identity is the id, not the definition. An index dropped and created again over the same path is a different index with a different id, and the ids of dropped indexes are never reused. That is not bookkeeping fastidiousness: posting files are named after the id, and a crash can leave one behind. Reusing an id would let a stale file from a dropped index be read as the postings of a live one — a wrong answer produced by a file that decodes perfectly.