@Override
  public boolean filterRowKey(Cell cell) throws IOException {
    // Impl in FilterBase might do unnecessary copy for Off heap backed Cells.
    return false;
  }
A filter that will only return the key component of each KV (the value will be rewritten as
empty).
<p>
This filter can be used to grab all of the keys without having to also grab the values.
hbase-client/src/main/java/org/apache/hadoop/hbase/filter/KeyOnlyFilter.java