This patch has two goals -- speed up the total partitions
calculations (walking databases is faster than walking tables),
and get rid og row_cache._partitions.size() call, which will
not be available on new _partitions collection implementation.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Message-Id: <20200423133900.27818-1-xemul@scylladb.com>