If the requested range wraps around the end of the ring, make_local_reader()
ends up trying to create an sstable reader with that wrapping range, which
is not supported. Also our shard-looping code is wrong in a wrapping range.
The solution is simple: split the wrap-around range into two (from the start
of the range until the end of the ring, and then from the beginning of the
ring until the end of the range), and read each of these subranges normally.
This feature is needed to allow streaming a range that wraps around, because
streaming currently uses make_local_reader().
Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>
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