CODEWITHSUNDEEP
firebasegoogle-cloud-platformgoogle-cloud-firestore
Damjan
Damjan

Reputation: 486

Firestore collection count

How to efficiently count the documents in a large Firestore collection.

Obviously, I do not want to get the entire collection and count it on the front end as the money will go through the roof. Is there really not a simple API such as db.collection('someCollection').count() or similar, but we need to hack around it?

Upvotes: 0

Views: 2052

Answers (1)

Alex Mamo
Alex Mamo

Reputation: 138824

(2022-10-20) Edit:

Starting from now, counting the documents in a collection or the documents that are returned by a query is actually possible without the need for keeping a counter. So you can count the documents using the new count() method which:

Returns a query that counts the documents in the result set of this query.

This new feature was announced at this year's Firebase summit. Keep in mind that this feature doesn't read the actual documents. So according to the official documentation:

For aggregation queries such as count(), you are charged one document read for each batch of up to 1000 index entries matched by the query. For aggregation queries that match 0 index entries, there is a minimum charge of one document read.

For example, count() operations that match between 0 and 1000 index entries are billed for one document read. For A count() operation that matches 1500 index entries, you are billed 2 document reads.

Is there really not a simple api such as db.collection('someCollection').count() or similar

No, there is not.

but we need to hack around it

Yes, we can use a workaround for counting the number of documents within a collection, which would be to keep a separate counter that should be updated every time a document is added to, or removed from the collection.

This counter can be added as a field inside a document in Firestore. However, if the documents in the collection are added or deleted very frequently, then this solution might be a little costly, a case in which I highly recommend you to use the Realtime Database. In this case, there is nothing you need to pay when you update the counter, but only when you read (download) it. And since it's just a number, then you'll have to pay almost nothing. I have even written an article a couple of years ago regarding solutions for counting documents in Firestore:

Upvotes: 3

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