title: How to check if key exists in Spark SQL map type
body: <p>So I have a table with one column of map type (the key and value are both strings).</p>
  <p>I'd like to write Spark SQL like this to check if given key exists in the map.</p>
  <pre class="lang-sql prettyprint-override"><code>select count(*) from my_table where map_contains_key(map_column, &quot;testKey&quot;)
  </code></pre>
  <p>How can I do this?</p>