How do I SELECT COUNT(*) w/o relationship?

Ash Forum Ash Questions / Help
,
1

I have a table with no relationship. I need to SELECT COUNT(*) FROM table WHERE condition; How do I do that inside an action/calculation/aggregate?

Thanks.

2 Likes
2

This is likely what you are looking for.

User
|> Ash.Query.filter(....)
|> YourApi.count() # uses the primary read action for authorization rules
3

Thanks, @zachdaniel. Should I use a generic action to run the query or can I do it inside a read action?

4

It depends on what you want to do with it. What are you trying to do with the count of records that you’re getting? Do you want an API endpoint that displays it? Do you want to put it in a view somewhere?

5

The count is used to decide if an engine (the electrical one) is started or not.

6

In what context? In some other resource? In a script? If there is some other code somewhere that needs to know the count, it should be able to do YourApi.count. You can’t make a :read action return an :integer or :boolean, though. If you want to put it behind an action, you’d need something like this:

action :is_started?, :boolean do
  argument ...
  run fn input, _ -> 
     query = build_your_query()

     {:ok, YourApi.exists?(query)}
  end
end

Or

action :count_of_stuff, :integer do
  argument ...
  run fn input, _ -> 
     query = build_your_query()

     {:ok, YourApi.count(query)}
  end
end
2 Likes
7

This is what I need. Thanks.

1 Like
8

If anybody is coming from Ash Tutorial (Livebook), here is how to define action inside Tutorial.Support.Ticket module to get the total tickets count.

  actions do
    action :count_of_tickets, :integer do
      run fn input, _ ->
        {:ok, Tutorial.Support.Ticket |> Ash.count()}
      end
    end
  end
3 Likes