NeedsCompaction is imprecise for Universal Compaction #14328
Description
NeedsCompaction is imprecise for Universal Compaction. It is computed as num_sorted_runs / mutable_cf_options.level0_file_num_compaction_trigger, yet in practice, even if this logic is triggered, a suitable compaction may still fail to be picked. This is because no appropriate compaction can be selected based on the size ratio, nor via max read amplification (max_read_amp) or size amplification (sizeamp) under the current state. Would you consider adopting a more precise approach to calculate NeedsCompaction?
