title: mongoose findMany query with refs
body: <p>I am new to mongoose I don't really find any reference how mongoose <code>populate</code> deals with findMany query having <code>ref</code></p>
  
  <p>for example I have a <code>categories</code> collection and a <code>products</code> collection as on product can be assigned to many categories that's why they exist in 2 different collections.</p>
  
  <p>Now if I call <code>findMany</code> method on <code>categories</code> collection and also <code>populate</code> with <code>products</code> will mongoose execute per category find products ? or all referenced product ids will be collected and in one query all products will be queried like <code>dataloader</code> do ?</p>