@Override
  public String toString() {
    return String.format("%s (%s, %s, %s, %s)", this.getClass().getSimpleName(),
      Bytes.toStringBinary(this.columnFamily), Bytes.toStringBinary(this.columnQualifier),
      this.op.name(), Bytes.toStringBinary(this.comparator.getValue()));
  }
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