Ash FrameworkAF
Ash Framework•3y ago•
5 replies
Mylan Connolly

Issue using datetime_add

Hello, thanks again for the awesome library, I was trying to get into some more useful functionalities of Ash (calculations, etc.) and I'm mostly having a good time learning about it but there was one bit that I was having a hard time with. I was modeling an appointment, which I wanted to store the start date and the duration of. I thought calculating the end time would be useful, so I added made the following resource:

use Ash.Resource, data_layer: AshPostgres.DataLayer

# ...

calculations do
  calculate(
    :end_time,
    :utc_datetime,
    expr(datetime_add(start_time, duration, :minute))
  )
end

attributes do
  uuid_primary_key(:id)

  attribute :start_time, :utc_datetime do
    allow_nil?(false)
  end

  attribute :duration, :integer do
    default(30)
  end

  attribute(:description, :string)

  timestamps()
end


If I attempt to load the calculation, I get an error:

Mindset.Patients.Appointment.read_all(load: :end_time)
** (Postgrex.Error) ERROR 42846 (cannot_coerce) cannot cast type interval to timestamp without time zone


This is the SQL that is generated:

SELECT a0."id", a0."start_time", a0."duration", a0."description", a0."inserted_at", a0."updated_at", a0."patient_id", a0."start_time"::timestamp + (a0."duration"::bigint::numeric * interval '1 minute')::timestamp FROM "client_0d98e96c-ddb3-43e2-98ee-df027173c950"."appointments" AS a0


If I tweak it to include parentheses around the timestamp calculation, it works:

SELECT a0."id", a0."start_time", a0."duration", a0."description", a0."inserted_at", a0."updated_at", a0."patient_id", a0.("start_time"::timestamp + (a0."duration"::bigint::numeric * interval '1 minute'))::timestamp FROM "client_0d98e96c-ddb3-43e2-98ee-df027173c950"."appointments" AS a0


Is there something I'm doing incorrectly in defining the calculation?

Thanks!
Was this page helpful?