title: Spark left outer join memory issue
body: <p>I have a Spark job which gives me a <em>Java.lang.OutOfMemoryError: Java heap space</em> (or some GC overhead).</p>
  
  <p>It appears in a task whithin a stage where the statics for complete tasks show the 75 percentile memory and disk spill are 0 but for maximum they are respectively 1732.5 MB and 145.5 MB.</p>
  
  <p>I am pretty sure I have a key which represents more than 70% of all lines during a leftOuterJoin. </p>
  
  <p>Is there a way to spread values associates to this key on multiple partition when doing this join?</p>
  
  <p>Thanks</p>