title: Can MySQL parallelize UNION subqueries (or anything at all)?
body: <p>I use a partitioned table with a large amount of data. According to MySQL docs, it is on the ToDo list that:</p>
  
  <blockquote>
    <p>Queries involving aggregate functions such as SUM() and COUNT() can
    easily be parallelized.</p>
  </blockquote>
  
  <p>... but, can I achieve the same functionality using UNION subqueries? Are they parallelized, or do I have to create a multithreaded client to run concurrent queries with all the possible partition keys?</p>
  
  <hr/>
  
  <p><strong>Edit:</strong></p>
  
  <p>The question is not strictly about UNION or subqueries. I would like to utilize as many cores as possible for my queries. Is there any way to do this (and make sure it's done) without paralellizing my application?</p>
  
  <p>Any good documentation about MySQL's current parallelizing capabilities?</p>