title: Is there any way to supply the allowDiskUse option to an mongoose.js aggregation?
body: <p>I'm running an aggregation on a collection of around 300k+ records which requires several unwinds and regroups. I'm hitting the following error;</p>
  
  <pre><code>'exception: Exceeded memory limit for $group, but didn\'t allow external sort. Pass allowDiskUse:true to opt in.'
  </code></pre>
  
  <p>I can't seem to work out how to pass this option through using the mongoose.js API?</p>