title: Check is anyone of the dataframe columns are empty
body: <p>I need to check if any of the columns of the dataframe are empty. Empty can be defined as if all rows of the column has values that are either null or empty string</p>
  <p>Dataframe is as follows</p>
  <pre><code>+---+-------+-------+-------+-------+
  | ID|Sample1|Sample2|Sample3|Sample4|
  +---+-------+-------+-------+-------+
  |  1|     a1|     b1|     c1|   null|
  |  2|       |       |       |       |
  |  3|     a3|       |       |       |
  +---+-------+-------+-------+-------+
  </code></pre>
  <p>The code I use for the check</p>
  <pre><code>mainDF.select(mainDF.columns.map(c =&gt; sum((col(c).isNotNull &amp;&amp; col(c)!=&quot;&quot;).cast(&quot;int&quot;)).alias(c)): _*).show()
  </code></pre>
  <p>What I get is</p>
  <pre><code>+---+-------+-------+-------+-------+
  | ID|Sample1|Sample2|Sample3|Sample4|
  +---+-------+-------+-------+-------+
  |  3|      3|      3|      3|      2|
  +---+-------+-------+-------+-------+
  </code></pre>
  <p>What I hope to get is</p>
  <pre><code>+---+-------+-------+-------+-------+
  | ID|Sample1|Sample2|Sample3|Sample4|
  +---+-------+-------+-------+-------+
  |  3|      2|      1|      1|      0|
  +---+-------+-------+-------+-------+
  </code></pre>
  <p>Also, My final results should be a <code>true</code> or <code>false</code> on if anyone of the columns is empty.
  In this case it will be <code>true</code> because count of <code>Sample4</code> is 0</p>