Different collection find() iteration order between client stub and server

help MongoDB
1

Hi,

We have some methods where we pass an array of doc _ids as parameter. We use optimistic UI, so the methods are executed on both the client stub and server.

When a collection.find({ _id: { $in: doc_ids } } ) is executed inside the method, it turns out that the order in which the documents are iterated on the client (minimongo) can be different from the server.

This is a problem in cases where we insert new documents during each iteration, resulting in different doc id’s for the same documents between client stub and server.

Is this normal behavior, or a bug?

The way we solve it now is to add { sort: { _id: 1 } } to these queries, but we just wonder if this behavior is to be expected?

2

Order is not guaranteed even if you were only on the server or only on the client. Every query may return a different order regardless where the query is called from.

3

Thanks for your response!

So this is definitely something to realize when using the $in operator with optimistic UI.