Comment #1 originally posted by alexkarpenko on 2012-09-15T23:35:26.000Z:

Similarly, it'd be great if we could get the size of an entry, without also fetching the value from disk.

Comment #2 originally posted by sanjay@google.com on 2012-09-18T17:18:47.000Z:

There is no way to implement Count more efficiently inside leveldb than outside.

"Delete range" could theoretically be implemented more efficiently inside leveldb, but it would be very complicated or would interact badly with snapshots. So it won't happen any time soon.

Comment #3 originally posted by earonesty on 2014-07-10T18:44:29.000Z:

If a fast count is important, you can keep track of the count as you write entries, and write it out as it's own special entry.

# pseudo 
if (!get(k)) {
   put(k,v)
   c=get("*cnt");
   ++c;
   put("*cnt",v)
} else {
   put(k,v)
}