Add contiguity flag to cache entry and set it in scanning reader.
Partitions fetched during scanning are continuous
and we know there's nothing between them.
Clear contiguity flag on cache entries
when the succeeding entry is removed.
Use continuous flag in range queries.
Don't go do disk if we know that there's nothing
between two entries we have in cache. We know that
when continuous flag of the first one is set to true.
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
Message-Id: <72bae432717037e95d1ac9465deaccfa7c7da707.1466627603.git.piotr@scylladb.com>
9b011bff18