title: Parallel mongoose queries with promises/bluebird?
body: <p>I have a nodejs/mongodb project using mongoose, and also bluebird for promises.</p>
  
  <p>Here is my problem : I have a function that has to execute sometimes 1 query, sometimes 2 queries in parallel, and then join the result from both queries. Here is a pseudo code (because I use coffeescript, however this isn't related) :</p>
  
  <pre><code>function(param) {
    // 1st query
    query1.exec
  
    // 2nd query, should be done in parallel with the 1st
    if (param)
      query2.exec
  
    // process requiring result from both queries
    callback()
  }
  </code></pre>
  
  <p>I know how to perform parallel tasks with async, however I don't understand how to perform this with bluebird or mongoose promises.</p>
  
  <p>Thanks,</p>