"
Users are adjusted by sprinkling `upgrade_to_v2()` and
`downgrade_to_v1()` where necessary (or removing any of these where
possible). No attempt was made to optimize and reduce the amount of
v1<->v2 conversions. This is left for follow-up patches to keep this set
small.
The combined reader is composed of 3 layers:
1. fragment producer - pop fragments from readers, return them in batches
(each fragment in a batch having the same type and pos).
2. fragment merger - merge fragment batches into single fragments
3. reader implementation glue-code
Converting layers (1) and (3) was mostly mechanical. The logic of
merging range tombstone changes is implemented at layer (2), so the two
different producer (layer 1) implementations we have share this logic.
Tests: unit(dev)
"
* 'combined-reader-v2/v4' of https://github.com/denesb/scylla:
test/boost/mutation_reader_test: add test_combined_reader_range_tombstone_change_merging
mutation_reader: convert make_clustering_combined_reader() to v2
mutation_reader: convert position_reader_queue to v2
mutation_reader: convert make_combined_reader() overloads to v2
mutation_reader: combined_reader: convert reader_selector to v2
mutation_reader: convert combined reader to v2
mutation_reader: combined_reader: attach stream_id to mutation_fragments
flat_mutation_reader_v2: add v2 version of empty reader
test/boost/mutation_reader_test: clustering_combined_reader_mutation_source_test: fix end bound calculation
e772fcbd57