Utilizing Firebase Cloud Functions to perform querying operations on a collection

Question

Utilizing Firebase Cloud Functions to perform querying operations on a collection

Imagine having two main collections: one for users and another for stories. Whenever a user document is updated (specifically the values username or photoUrl), you want to mirror those changes on corresponding documents in the story collection.

A sample user document might resemble this (simplified):

{
    username: 'blubber',
    photoUrl: 'my/photo/path',
    uid: 'usersUniqueId'
}

This would be an example of a story document (simplified):

{
    username: 'blubber',
    photoUrl: 'my/photo/path',
    uid: 'usersUniqueId',
    sid: 'storiesUniqueId,
    content: '...'
}

When it comes to cloud functions, you're unsure how to retrieve all story documents that match the user's id. The current code snippet looks like this:

export const onUpdateUser = functions.firestore.document('/users/{userId}')
    .onUpdate((change, context) => {
    const before = change.before.data();
    const after = change.after.data();

    if(before.username !== after.username || before.photoURL !== after.photoURL) {
        return admin.firestore().collection('/stories/')
               .where(before.uid, '==', ***fetch the comparison***)
        // perform specific action
    } else {
        return null;
    }
});

Any assistance regarding this matter would be greatly appreciated.

typescript firebase google-cloud-firestore google-cloud-functions

Answer 1

Answer №1

Recently made some adjustments to the code provided below. It was almost there, but I decided to incorporate async await for better code readability. Adding error handling is also recommended for a more robust implementation.

const onUpdateUser = functions.firestore.document('/users/{userId}')
    .onUpdate(async (change, context) => {
    const previousData = change.before.data();
    const newData = change.after.data();

    if (previousData.username !== newData.username || previousData.photoURL !== newData.photoURL) {
        return admin.firestore().collection('/stories/')
           .where('uid', '==', previousData.uid).get().then(  
               result => {
                   if (result.size > 0) {
                       result.forEach(async doc => {
                           await doc.ref.update({
                               username: newData.username,
                               photoUrl: newData.photoUrl
                           })
                        })
                   }
                   return;
               }
           )
    } else {
        return null;
    }
});

Answer 2

Recently made some adjustments to the code provided below. It was almost there, but I decided to incorporate async await for better code readability. Adding error handling is also recommended for a more robust implementation.

const onUpdateUser = functions.firestore.document('/users/{userId}')
    .onUpdate(async (change, context) => {
    const previousData = change.before.data();
    const newData = change.after.data();

    if (previousData.username !== newData.username || previousData.photoURL !== newData.photoURL) {
        return admin.firestore().collection('/stories/')
           .where('uid', '==', previousData.uid).get().then(  
               result => {
                   if (result.size > 0) {
                       result.forEach(async doc => {
                           await doc.ref.update({
                               username: newData.username,
                               photoUrl: newData.photoUrl
                           })
                        })
                   }
                   return;
               }
           )
    } else {
        return null;
    }
});

Answer 3

Answer №2

It seems like this is the goal you are aiming for.

In order to achieve that, I have restructured the function call and its reference within the .onUpdate method. Assuming your intention is to update multiple documents in the stories collection, I have implemented the use of batch.

const onUpdateUser = functions
  .firestore
  .document('/users/{userID}')
  .onUpdate(myFunc);

const myFunc = (change, context) => {
  const before = change.before.data();
  const after = change.after.data();

  // Checking if username and photoURL have changed
  if (before.username === after.username
    && before.photoURL === after.photoURL) {
    return Promise.resolve(); // Exit cloud function early if nothing has changed
  }

  return admin
    .firestore()
    .collection('stories')
    .where('uid', '==', before.uid)
    .get()
    .then((docs) => {
      const batch = admin.firestore().batch();

      docs.forEach((doc) => {
        batch.set(doc.ref, {
          username: after.username,
          photoURL: after.photoURL,
        }, {
            merge: true, // Merge fields instead of replacing entire document data
        });
      });

      return batch.commit();
    })
    .catch(console.error);
};

Answer 4

It seems like this is the goal you are aiming for.

In order to achieve that, I have restructured the function call and its reference within the .onUpdate method. Assuming your intention is to update multiple documents in the stories collection, I have implemented the use of batch.

const onUpdateUser = functions
  .firestore
  .document('/users/{userID}')
  .onUpdate(myFunc);

const myFunc = (change, context) => {
  const before = change.before.data();
  const after = change.after.data();

  // Checking if username and photoURL have changed
  if (before.username === after.username
    && before.photoURL === after.photoURL) {
    return Promise.resolve(); // Exit cloud function early if nothing has changed
  }

  return admin
    .firestore()
    .collection('stories')
    .where('uid', '==', before.uid)
    .get()
    .then((docs) => {
      const batch = admin.firestore().batch();

      docs.forEach((doc) => {
        batch.set(doc.ref, {
          username: after.username,
          photoURL: after.photoURL,
        }, {
            merge: true, // Merge fields instead of replacing entire document data
        });
      });

      return batch.commit();
    })
    .catch(console.error);
};

Utilizing Firebase Cloud Functions to perform querying operations on a collection

Answer №1

Answer №2

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