@Override
  public boolean isFamilyEssential(byte[] name) {
    return !this.filterIfMissing || Bytes.equals(name, this.columnFamily);
  }
The only CF this filter needs is given column family. So, it's the only essential column in
whole scan. If filterIfMissing == false, all families are essential, because of possibility of
skipping the rows without any data in filtered CF.
hbase-client/src/main/java/org/apache/hadoop/hbase/filter/SingleColumnValueFilter.java