title: Can we get all the column names from an HBase table?
body: <h1>Setup:</h1>
  <p>I have an HBase table, with 100M+ rows and 1 Million+ columns. Every row has data for only 2 to 5 columns. There is in just 1 Column Family.</p>
  <h1>Problem:</h1>
  <p>I want to find out all the distinct <code>qualifiers</code> (columns) in this <code>column family</code>. Is there a quick way to do that?</p>
  <p>I can think of about scanning the whole table, then getting <code>familyMap</code> for each row, get <code>qualifier</code> and add it to a <code>Set&lt;&gt;</code>. But that would be awfully  slow, as there are 100M+ rows.</p>
  <p>Can we do any better?</p>