What are the various join types in Spark? : <p>I looked at the docs and it says the following join types are supported: </p>

<blockquote>
  <p>Type of join to perform. Default inner. Must be one of: inner, cross,
  outer, full, full_outer, left, left_outer, right, right_outer,
  left_semi, left_anti.</p>
</blockquote>

<p>I looked at the <a href="https://stackoverflow.com/questions/17946221/sql-join-and-different-types-of-joins">StackOverflow answer</a> on SQL joins and top couple of answers do not mention some of the joins from above e.g. <code>left_semi</code> and <code>left_anti</code>. What do they mean in Spark?</p>
