title: Angular 6 - AnguarFire - query a collection using multiple document fields
body: <p>I use AngularFire &amp; Cloud Firestore in my project and I need to make a query with multiple conditions(where) to a collection.</p>
  
  <p>I tried to use this code but it's ignoring the second condition.</p>
  
  <pre><code> this.itemCollection = this.afs.collection&lt;Item&gt;('items', ref =&gt; {
  
   return ref
           .where('size', '==', 'large')
           .where('brand', '==', 'some-brand')
   })
   this.items = this.itemCollection.valueChanges();
  </code></pre>
  
  <p>What am I doing wrong, how do I apply multiple conditions in AngularFire?</p>