In many cases we trigger offstrategy compaction opportunistically
also when there's nothing to do. In this case we still print
to the log lots of info-level message and call
`run_offstrategy_compaction` that wastes more cpu cycles
on learning that it has nothing to do.
This change bails out early if the maintenance set is empty
and prints a "Skipping off-strategy compaction" message in debug
level instead.
Fixes#13466
Also, add an group_id class and return it from compaction_group and table_state.
Use that to identify the compaction_group / table_state by "ks_name.cf_name compaction_group=idx/total" in log messages.
Fixes#13467Closes#13520
* github.com:scylladb/scylladb:
compaction_manager: print compaction_group id
compaction_group, table_state: add group_id member
compaction_manager: offstrategy compaction: skip compaction if no candidates are found
022465d673