When performing a range query, we want to iterate over shards, running the
query on each shard in order until the query range is exhausted or we have
the right number of rows.
To be able to do this, introduce token_for_next_shard(), which allows us
to determine the boundary between shards.
It is a sort-of inverse to shard_of(), in that
shard_of(token_for_next_range(t)) == shard_of(t) + 1
In order to support ByteOrderedPartitioner, we need to implement the
missing describe_ownership and midpoint function in
byte_ordered_partitioner class.
As a starter, this path uses a simple node token distance based method
to calculate ownership. C* uses a complicated key samples based method.
We can switch to what C* does later.
Tests are added to tests/partitioner_test.cc.
Fixes#1378
Make sharding partitioner-specific, since different partitioners interpret
the byte content differently.
Implement it by extracting the shard from the most significant bits, which
can be used to minimize cross shard traffic for range queries, and reduces
sstable sharing.
Some of the tests in DTEST take advantage of the fact that
ByteOrderedPartitioner guarantees certain ordering of partition keys.
Signed-off-by: Paweł Dziepak <pdziepak@cloudius-systems.com>
