How can I create and touch a document only if none exist for it already?

Question

I have a case where if there is data in my Firestore database, I want it to fail on create a new document, and definitely not overwrite or send any updates to that document.

I'm doing these in batches so I can't have any batches fail or it kills the whole batch.

Here's what I've tried/ruled out:

batch.update - Ruled out due to updating data batch.set - Ruled out as its default is to overwrite the data batch.set...{merge: true} - Ruled out as it would overwrite any fields I already have batch.create - This seemed hopeful but fails when a document already exists

let batch = db.batch()
...
batch.xyz(refToCreateOnly, Data) // this should be successful either way such that it does not kill the batch, and only updates if the ref does not exist
...
await batch.commit()

Is the best/possibly only way to do this with a transaction?

Yes, the entire batch has to succeed, or it's all rolled back. — Doug Stevenson, Oct 25 '19 at 15:49
If a security rule will kill a batch, and a batch needs to fully succeed, then that won't work. I don't think this is a duplicate. If you don't know to pair your search with security rules you'd never find the first one, and the answers to the second link you posted are about updating only. — Thingamajig, Oct 25 '19 at 15:53

score 0 · Answer 1 · answered Oct 25 '19 at 16:23

0

Yes, your only option here is to use a transaction to verify that the document doesn't exist prior to adding it.

answered Oct 25 '19 at 16:23

Doug Stevenson

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How can I create and touch a document only if none exist for it already?

1 Answers1