Ash Framework•6mo ago

Is there a way to do a 'limit' on a relationship?

My use case is eventually an aggregate, like 'count of the last 10 posts that are unpublished'. Was thinking I could get something working if I set up a relationship that was 'most recent 10 posts', and then an aggregate count on that relationship, but not seeing anything on how that'd work. Any ideas?

Solution:

Yeah, that would work. You could also see what happens if you do this: ```elixir has_many :last_ten... do read_action :an_action_with_a_limit...

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10 Replies

ZachDaniel•6mo ago

you can indeed:

has_many ... do
  limit 10
  sort foo: :asc
end

has_many ... do
  limit 10
  sort foo: :asc
end

oh, wait I guess you can't 🤔 I really thought you could do that 😓 but you can limit an aggregate FWIW but apparently only the inline calculation type of aggregate. Wow, how does everyone ask something innocent and stumble into a mess 😜

calculate :count_of_last_ten_posts_that_are_unpublished, :integer, expr(
  count(posts, query: [limit: 10, sort: [inserted_at: :desc], filter: published == true])
)

calculate :count_of_last_ten_posts_that_are_unpublished, :integer, expr(
  count(posts, query: [limit: 10, sort: [inserted_at: :desc], filter: published == true])
)

Something like this should work though And thank you for being the first person to use the new forum setup ❤️ We could support limit on aggregate DSL and on has_many relationships though FWIW Feel free to open proposals for both 😄

pikdumOP•6mo ago

* Cannot set limit on aggregate query

hm i like the idea of doing the limit on a has_many relationship, that seems pretty clean https://github.com/ash-project/ash/blob/f6688fcc71b750f8d96222ec8eb157b0eff523ea/lib/ash/query/aggregate.ex#L523 getting this even if it's an inline calculation type aggregate rather than an aggregate count type

ZachDaniel•6mo ago

huh. Maybe I'm wrong

pikdumOP•6mo ago

i'll make a proposal for limits + sort on a has_many relationship

ZachDaniel•6mo ago

right-o you can't do it apparently 😢 You can definitely do sort just not limit apparently. I'll have to look into why limit isn't supported on aggregate queries

pikdumOP•6mo ago

https://github.com/ash-project/ash/issues/2012 - made this so I think right now my best bet might be to just do things through code, like: * read action for getting last 10 posts that are unpublished * Enum.count or similar

Solution

ZachDaniel•6mo ago

Yeah, that would work. You could also see what happens if you do this:

has_many :last_ten... do
  read_action :an_action_with_a_limit
end

has_many :last_ten... do
  read_action :an_action_with_a_limit
end

nicolkill•5mo ago

A question here, my context

    # action on the relation
    read :latest_filterable do
      filter expr(exists(custom_field, filterable == true))
      prepare build(limit: 10)
    end

    # main module

    # calculation
    calculate :custom_field_text, :string, expr(filterable_custom_fields.value) do
      load [:filterable_custom_fields]
      public? true
    end

    # relation
    has_many :filterable_custom_fields, CustomField
      read_action :latest_filterable
      source_attribute :id
      destination_attribute :custom_field_id
      writable? false
      public? true
    end

    # action on the relation
    read :latest_filterable do
      filter expr(exists(custom_field, filterable == true))
      prepare build(limit: 10)
    end

    # main module

    # calculation
    calculate :custom_field_text, :string, expr(filterable_custom_fields.value) do
      load [:filterable_custom_fields]
      public? true
    end

    # relation
    has_many :filterable_custom_fields, CustomField
      read_action :latest_filterable
      source_attribute :id
      destination_attribute :custom_field_id
      writable? false
      public? true
    end

on this case i have my action on my relation module, on the main module the relation and a calculation that uses this relation and i have a issue of forbidden error, can you help me here please forgot that, the issue was use the source/destination attributes, removing works well (the module has already that data)

ZachDaniel•5mo ago

THis seems like a different question? oh, sounds like you worked it out.

nicolkill•5mo ago

was about the same, use a limit on a relation, using the has_many > read_action but returns a forbidden, but was about my config, not about the action

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Is there a way to do a 'limit' on a relationship?

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