title: Mongo template left join between two queries
body: <p>In a spring project, I'm using <strong>reactive</strong> mongodb with mongo template to return a result of type Report class.</p>
  <pre><code>    var res1 = (Flux&lt;Report&gt;) template.find(query1, ReportFactory.getReport(reportType).getClass());
  
      var res2 = (Flux&lt;Report&gt;) template.find(query2, ReportFactory.getReport(reportType).getClass());
  </code></pre>
  <p>I want a way to find the left join between two result using mongo template <strong>without using java.</strong>
  For example:</p>
  <p>if <code>res1 = {Rep1,Rep2,Rep3]</code>and: <code>res2 = {Rep2,Rep5}</code></p>
  <p>the left join between them should be <strong>Rep2</strong></p>
  <p><a href="https://i.stack.imgur.com/ldAs9.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ldAs9.png" alt="enter image description here" /></a></p>