MemStoreCompactionStrategy is the root of a class hierarchy which defines the strategy for
choosing the next action to apply in an (in-memory) memstore compaction. Possible action are: -
No-op - do nothing - Flatten - to change the segment's index from CSLM to a flat representation -
Merge - to merge the indices of the segments in the pipeline - Compact - to merge the indices
while removing data redundancies In addition while applying flat/merge actions it is possible to
count the number of unique keys in the result segment.