How can I get a document at a specific index after orderBy

Question

I have some code like this:

...
const snapshot = firestore().collection("orders").orderBy("deliveryDate")
...

I want to access only the 100th order in the returned documents. So far, the only way I achieve this is to do firestore().collection("orders").orderBy("deliveryDate").limit(100) and this returns first 100 documents and I can access the last order. But, I end up fetching 99 unwanted documents and this could become quite slower if I want the 200th document or higher.

So, I basically want to know if there's a possible way of getting just the index I want after sorting.

As far as I know, startAt() and startAfter() only accept a doc reference or field values, not an index/offset

Answer 1

Firestore does not offer any way to offset by some numeric amount to web and mobile clients (and doing so would end up having the exact same cost as what you're doing now).

If you need to impose some sort of offset into your collection, you will need to maintain that in the document itself for querying, or use some other type of storage that gives you fast cheap access by index.