View Source Atomics

Atomics allow you to attach expression-based changes to changesets, to be executed in the data layer when the action is performed.

For example:

update :increment_score do
  argument :points, :integer, allow_nil?: false
  change atomic_update(:score, expr(score + ^arg(:points)))
end

What is supported

  • Atomics are only supported in update actions and upserts. In the case of upserts, the atomic changes are only applied in the case of a conflicting record.
  • Attaching atomics to an action using the atomic_update/2 change in the action, as shown in the example below.
  • Attaching atomics to a changeset manually with Ash.Changeset.atomic_update/3
  • Using calculations that don't refer to aggregates or related values in expressions

Manually attached 

changeset
|> Ash.Changeset.atomic_update(:score, Ash.Expr.expr(score + 1))
|> Api.update!()

Upsert example 

create :upsert do
  upsert? true
  change set_attribute(:points, 1) # set to 1
  set_on_upsert :points, expr(points + 1) # or increment existing
end