Generating primary keys (IDs) at the backend

[ddenev]

I want to delegate the generation of IDs to my backend (to avoid conflicts when using multiple client devices, also I have a legacy backend data that already has IDs generated).

1. What is the correct way to set the SyncManager so that it recognizes and properly syncs a new item (after collection.insert()) that has its ID created on the backend?
2. How to get the new backend ID (after collection.insert()) and use it in the client code?

[maxnowack]

This is possible, but it isn't a good idea if you have other options.

Since SignalDB is a local-first database, it must be able to generate IDs on its own. What you could do is map the backend ID to a field in your document (let's call it remote_id) during the pull operation. During the push, you need to map it back and discard the ID generated by SignalDB before making calls to your backend.

If a document doesn't have a remote_id set, create it in the backend. Otherwise, update the existing record.

I don't recommend this approach, as it makes it difficult to verify which documents were already created in your backend. This can lead to duplicate entries. Only use this method if you cannot modify your backend's API.

If you're able to make changes to your backend, consider one of these better alternatives:

1. Use UUIDs or strings as primary keys and allow the client to define them (easiest option).
2. Add a client_id field to your schemas and refactor your API to treat this field as the id. This way, you can retain backend-defined primary keys without the downsides of the workaround above. Keep in mind that all your relations must also use the client_id.

[ddenev]

@maxnowack, thank you for your reply!

After reading some about unique ids and researching for id generating libs (https://github.com/grantcarthew/awesome-unique-id?tab=readme-ov-file#javascript), I think I decided to go with the locally generated IDs but retry the item creation (in push) if the backend gives a duplication error. The only thing I am currently missing and don't know how to do is:

How to inform the code that called collection.insert() about the newly generated ID and how to update the locally created item with the new ID, since this ID will be re-created (when retrying) in the push method and I can't seem to find a way to update the ID of the created local item from the SyncManager. Can you advise?

[maxnowack]

For UUIDs the probability for collisions is really unlikely. I mean really really unlikely.

Imagine filling the entire Earth, inside and out, with grains of sand — from the core to the atmosphere.

Now imagine doing that not just with our planet, but with a trillion Earths, each packed solid with a trillion times more sand than Earth’s beaches.

If you randomly pick one grain from this mega-mountain of sand, and someone else also picks one — the odds that it’s the same grain is about the same as two UUID v4s colliding.

However, you just could just catch the error in your push method and do a collection.updateOne() to change the id to the new one.