The query scheduler executes queries by scanning each segment in portions of a particular byte size (\The query scheduler executes queries by scanning each segment in portions of a particular byte size (\ If a chunk takes too long, the scheduler might decide to stop execution part way through, and defer the rest of the work for later. This allows the scheduler to context switch to other queries, even if some very slow query is present where chunks take a long time. This metric counts how many times that kind of deferment happens, which is an indicator of the presence of one or more very slow queries.