Does lock_version need to be cast() into ChangeSet, or doing changeset |> optimistic_lock(:lock_version) is enough? I mean, AFAIK every attempt to update an object should have lock_version in the attributes map, so how does Ecto know what value to use for lock_version if we don’t put it into chan…

It just gets the field from the changeset source: https://github.com/elixir-ecto/ecto/blob/4a143348ab89e0174a1a5082fd47d868ebd9689b/lib/ecto/changeset.ex#L3418 You don’t need to cast just to access the source data. And you don’t want to cast the lock version, because you don’t want the value to be…

I don’t? For the value to be set from the parameters I need to put it in a changesset somehow - I thought it’s done by “casting”. And the whole point of optimistic lock is to make sure the caller doesn’t have the stale version of the data, so it would seem like having the most recent value of lock_v…

When you call the changeset function, you pass the struct that you have, which has the lock_version value at the time you fetched it from the database. In the changeset, this original struct is under the data field. That’s where the optimistic_lock function gets the current lock version from. Ecto.…

In my case I have a absinthe client that pulls the object from the backend via graphql, and edits some fields on the object. The save operation takes id of the object, the changed field, e.g. description, and lockVersion from the last time the data was pulled. Multiple users can edit the same object…

Elixir Programming Language Forum

Optimistic Locking clarification?

Questions & Help Questions

woylie December 21, 2023, 7:13am 6

Yes, in your case, you’d want to cast the lock version indeed.