In Cloud Firestore, why is it not possible to “single bulk” delete a collection (as can be done with Realtime Database)?

Question

With Firebase real time database we can delete a huge list of items with one single command simply by calling remove () on the parent node (the node is deleted

Answer 1

I was happily refactoring my app for Firestore from Realtime Database, enjoying the shorter code and simpler syntax, until I refactored the delete() functions! To delete a document with subcollections:

• Create an array of promises.
• get() a subcollection, that doesn't have further subcollections.
• Iterate through a forEach() function to read each document in the subcollection.
• Delete each document, and push the delete command into the array of promises.
• Go on to the next subcollection and repeat this.
• Use Promise.all(arrayOfPromises) to wait until all the subcollections have been deleted.
• Then delete the top-level document.

With multi layers of collections and documents you'll want to make that a function, then call it from another function to get the next higher layer, etc.

You can see this in the console. To manually delete collections and documents, delete the right-most document, then delete the right-most collection, and so on working left.

Here's my code, in AngularJS. It only works if the top-level collection wasn't deleted before the subcollections.

$scope.deleteClip = function(docId) {
if (docId === undefined) {
docId = $scope.movieOrTvShow + '_' + $scope.clipInMovieModel;
}
$scope.languageVideos = longLanguageFactory.toController($scope.language) + 'Videos';
var promises = [];
firebase.firestore().collection($scope.languageVideos).doc($scope.movieOrTvShow).collection('Video Clips').doc(docId).collection('SentenceTranslations').get()
.then(function(translations) {
  translations.forEach(function(doc) {
    console.log(doc.id);
    promises.push(firebase.firestore().collection($scope.languageVideos).doc($scope.movieOrTvShow).collection('Video Clips').doc(docId).collection('SentenceTranslations').doc(doc.id).delete());
  });
});
firebase.firestore().collection($scope.languageVideos).doc($scope.movieOrTvShow).collection('Video Clips').doc(docId).collection('SentenceExplanations').get()
.then(function(explanations) {
  explanations.forEach(function(doc) {
    console.log(doc.id);
    promises.push(firebase.firestore().collection($scope.languageVideos).doc($scope.movieOrTvShow).collection('Video Clips').doc(docId).collection('SentenceExplanations').doc(doc.id).delete());
  });
});
Promise.all(promises).then(function() {
  console.log("All subcollections deleted.");
  firebase.firestore().collection($scope.languageVideos).doc($scope.movieOrTvShow).collection('Video Clips').doc(docId).delete()
  .then(function() {
    console.log("Collection deleted.");
    $scope.clipInMovieModel = null;
    $scope.$apply();
  })
  .catch(function(error) {
    console.log("Remove failed: " + error.message);
  });
})
.catch(function(error){
  console.log("Error deleting subcollections: " + error);
});
};

All that would have been one line in Realtime Database.