Firestore batch in for loop stores only last document

Question

I am trying to update user data in multiple tasks collection. So I have multiple id's of tasks, where I use forEach loop reading each of task. In each task I have multiple users where I want to update only one specific user.

I am using firestore and batch for writing data. The problem is that only last task is updated. This is my code

tasksIds.forEach(async function(taskId) {
 
                
                const batch = db.batch()

                try {
                    taskRef =  db.collection("tasks")
                        .doc(taskId)
                    const projectDataTemp = await taskRef.get()
                    projectData=  projectDataTemp.data()
                    allClients = projectData.users
                } catch (error) {
                    console.log(error)
                
                await allClients.map(async (oneClient) => {
                    if(oneClient.id === id) {
                        oneClient.name = name
                    }

                })

                    
                    await batch.update(taskRef, { users: allClients})
                
                // Commit the batch
                 await batch.commit().then(() => console.log("success",allClients))
        
            })
        }

So everything is good except that only last task is updated, I suppose that the problem is of synchronisation that batch.commit isn't finished and another task is started. Anyone idea how to solve this?

It might be helpful if you add some logging that shows how your code is executing, and share that specific output so we can see what's actually happening. — Doug Stevenson, Oct 25 '20 at 15:48
The problem is `const projectDataTemp = await taskRef.get()` here await waits until data is fetched, in meantime loop goes on, and in the end only last one is updated — HardRock, Oct 25 '20 at 22:00
async/await does not work in a forEach loop in the way you expect. I suggest reading this: https://stackoverflow.com/questions/37576685/using-async-await-with-a-foreach-loop — Doug Stevenson, Oct 25 '20 at 22:17
Thank you for pointing me in right direction, using standard for loop solved my problem — HardRock, Oct 26 '20 at 07:23

score 1 · Answer 1 · answered Oct 26 '20 at 07:23

If you want to read the files in sequence, you cannot use forEach indeed. Just use a modern for … of loop instead, in which await will work as expected:

async function printFiles () {
  const files = await getFilePaths();

  for (const file of files) {
    const contents = await fs.readFile(file, 'utf8');
    console.log(contents);
  }
}

Changing forEach loop for standard one, solved problem.

Thank you @DougStevenson for pointing me in right direction

Firestore batch in for loop stores only last document

1 Answers1