CompactionDetails getCompactionDetails(CompactionPolicy compactionPolicy) throws StoreException {
    return compactionPolicy.getCompactionDetails(capacityInBytes, index.getLogUsedCapacity(), log.getSegmentCapacity(),
        LogSegment.HEADER_SIZE, index.getLogSegmentsNotInJournal(), blobStoreStats, dataDir);
  }
Fetch {@link CompactionDetails} based on the {@link CompactionPolicy} for this {@link BlobStore} containing
information about log segments to be compacted
@param compactionPolicy the {@link CompactionPolicy} that needs to be used to determine the {@link CompactionDetails}
@return the {@link CompactionDetails} containing information about log segments to be compacted. Could be
{@code null} if there isn't anything to compact
@throws StoreException on any issues while reading entries from index
ambry-store/src/main/java/com/github/ambry/store/BlobStore.java