... schema::get_partitioner and make schema::get_partitioner
return const&' from Piotr
Partitioners returned from get_partitioner are shared
and not supposed to be changed so let's use the type system
to enforce that.
dht::global_partitioner() is deprecated and will be removed
as soon as custom partitioners are implemented so it's best
to replace it with schema::get_partitioner.
Tests: unit(dev)
* hawk/global_partitioner_cleanup:
schema: get_partitioner return const&
compaction_manager: stop calling dht::global_partitioner()
sstable_datafile_test: stop calling dht::global_partitioner()