Firestore batch - actions which requires more than 1 write

Ofir Cohen 0
Viewed 32

TL;DR - There are conventions/payloads/actions out there, which requires more than 1 batch write to take place.

It occur to me that when im adding a set operation to a batch, for an object which is using firestore serverTimstamp feature, it costs 2 write operations rather than 1. Could not find any documentation about that. The problem is, that if you wrap firestore batch with a local counter in your code, to avoid reaching the 500 threshold, you might miss-calculate batch size.

In my example, I am using Golang firestore sdk (but I do believe this issue will be common for all other sdk's because it derives from firestore fundamental mechanism)

batch.Set(ctx, docRef, struct {
    LastUpdate time.Time `firestore:"lastUpdate,serverTimestamp"`
}{}, firestore.MergeAll)

--> batch.writes was increased by 2 writes rather than 1

My question is - are any other special firestore values/actions etc' which might also require more than 1 batch write operation to take place? Also do anyone can suggest a workaround for that issue?

transactions go google-cloud-firestore firebase
1 Answers

So-called field transform operations indeed may require more than one write operation on the server, reducing the capacity of logical write operations you can perform in a batched write or transaction. If I recall correct, you only be charged for one write operation in such cases though.

From the answer I gave before to what is "field transformations" in Firestore?, it seems that the field transform operations that are available are setToServerValue (the server timestamp you use), increment, appendMissingElements, removeAllFromArray, maximum and minimum. I'm not sure if the last two are exposed on any SDK yet.

Frank van Puffelen0
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