title: Multi-path update with Firestore
body: <p>Everywhere I read about Firestore it is stated that it requires less denormalization than Realtime Firebase. I guess this is because it is a document database where you can point at specific documents and only retrieve that amount of data (?). </p>
  
  <p>However, I wonder how to manage a situation where denormalization would still be useful (e.g., we can save a query to the document containing the full information data by storing that same value on other documents as well). If an update of that value is then required, is there something like the Realtime Firebase multi-path update (to update the value at every document) to solve this issue?</p>