I have the following code in a cloud function which is returning an error with the message

Error: 3 INVALID_ARGUMENT: maximum 500 writes allowed per request

console.log(`${projectId} doClassifySources: Got ${_.size(output)} items`)

const lastClassification = new Date().toJSON()
const batch = firestore.batch()
batch.update(projectRef, {lastClassification})
_.forEach(output, item => {
  batch.set(projectRef.collection('output').doc(encodeURIComponent(item.url)), {
    classifiedAt: admin.firestore.FieldValue.serverTimestamp(),
    ...item
  }, {
    merge: true
  })
})

return batchmit().then(() => lastClassification)

Yet the firebase logs show this right before the error is thrown:

12:28:19.963 PM classifySources ZklZYB5hq96J43CroKgP doClassifySources: Got 310 items

That looks to me like the batch should contain 310 items, well below the 500 limit. Am I missing something in how that 500-item limit is calculated? Does the merge: true influence that in any way? Is it to do with the spread of item in the object being written (i.e. does that increase the number of writes needed)?

I have the following code in a cloud function which is returning an error with the message

Error: 3 INVALID_ARGUMENT: maximum 500 writes allowed per request

console.log(`${projectId} doClassifySources: Got ${_.size(output)} items`)

const lastClassification = new Date().toJSON()
const batch = firestore.batch()
batch.update(projectRef, {lastClassification})
_.forEach(output, item => {
  batch.set(projectRef.collection('output').doc(encodeURIComponent(item.url)), {
    classifiedAt: admin.firestore.FieldValue.serverTimestamp(),
    ...item
  }, {
    merge: true
  })
})

return batch.commit().then(() => lastClassification)

Yet the firebase logs show this right before the error is thrown:

12:28:19.963 PM classifySources ZklZYB5hq96J43CroKgP doClassifySources: Got 310 items

That looks to me like the batch should contain 310 items, well below the 500 limit. Am I missing something in how that 500-item limit is calculated? Does the merge: true influence that in any way? Is it to do with the spread of item in the object being written (i.e. does that increase the number of writes needed)?

• javascript
• google-cloud-firestore

1 Answer 1

With some additional testing, it appears that using admin.firestore.FieldValue.serverTimestamp() counts as an extra 'write'. With the code as above, I'm limited to 249 items (i.e. when output.length >= 250, the code will fail with that error message. If I remove the reference to serverTimeStamp(), I can get up to 499 items per write.

I can't find this documented anywhere, and perhaps it is a bug in the firebase library, so I will post an issue there and see what happens.