title: Spark Cosmos db connector is dropping columns where majority of rows are null
body: <p>I am trying to read a 30K rows data from cosmos db using the spark cosmos connector using the following
  code</p>
  <pre><code>val readConfig = Config(Map(
    &quot;Endpoint&quot; -&gt; &quot;&quot;,
    &quot;Masterkey&quot; -&gt; &quot;&quot;,
    &quot;Database&quot; -&gt; &quot;&quot;,
    &quot;Collection&quot; -&gt; &quot;&quot;,
    &quot;PreferredRegions&quot; -&gt; &quot;&quot;,
     &quot;query_custom&quot; -&gt; &quot;&quot;&quot;SELECT t.id,t.gender,t.loc from Tab t&quot;&quot;&quot;
   ))
  
  val df = spark.read.cosmosDB(readConfig)
  </code></pre>
  <p>In the 30k, only 2 rows have non null values for '<strong>loc</strong>' column. But for some reason the connector is dropping the '<strong>loc</strong>' column altogether in the final dataframe and the final dataframe is giving the following schema</p>
  <pre><code>df.printSchema
  root
   |-- id: string (nullable = true)
   |-- gender: string (nullable = true)
  </code></pre>
  <p>Can someone please help me how to get the '<strong>loc</strong>' column included in my final dataframe.</p>