private String getErrorMessageId(IndexEntry entry, PersistentIndex index) {
    IndexValue value = entry.getValue();
    Offset indexSegmentStartOffset = index.getIndexSegments().floorKey(value.getOffset());
    String kind = value.isFlagSet(IndexValue.Flags.Delete_Index) ? "DELETE" : "PUT";
    return "[" + indexSegmentStartOffset + ":" + entry.getKey() + ":" + kind + "]";
  }
@param entry the {@link IndexEntry} being examined.
@param index the {@link PersistentIndex} that {@code entry} belongs to.
@return a string that can uniquely identify an entry in error messages.
ambry-tools/src/main/java/com/github/ambry/store/CompactionVerifier.java