title: Nest.JS graphql get requested fields
body: <p>In Nest.js Graphql, is it possible to fetch the required list of fields from a resolver? To determine which joins to executed, and which not to, for example for this db schema:</p>
  
  <pre><code>Employee
   id
   employer_id
   name
  
  Employer
   id
   name
  </code></pre>
  
  <p>In case of the following graphql query:</p>
  
  <pre><code>  query {
      employees {
        id
        name
        employer {
          id
        }
      }
    }
  </code></pre>
  
  <p>It is not necessary to fetch/join the employer data from the database, since the employer id can be accessed from the employee table.</p>