Namespaced macros inside the Ecto queries

Questions / Help
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1

Greetings,
I’m looking to define a couple of macros in different modules to use them in my ecto queries, as part of the where conditions inside a Ecto.Query.from call. The problem I’m facing is how to call the macros by their fully qualified name (i.e. MyModule.my_macro), without importing the module and using the short name.
A simplified example of what I tried:

defmodule Order do
  schema "orders" do … end

  defmacro recent(o) do
    quote do
      unquote(o).inserted_at > ago(5, "day")
    end
  end
end

defmodule Quote do
  schema "quotes do … end

  defmacro recent(q) do
    quote do
      unquote(q).inserted_at > ago(3, "day")
    end
  end
end

# my_context.ex

> require Quote
> Repo.all(from(q in Quote, where: Quote.recent(q))
# ** (Ecto.Query.CompileError) `Quote.recent(q)` is not a valid query expression. If you want to invoke Quote.recent/1 in a query, make sure that the module Quote is required and that recent/1 is a macro

> require Order
> Repo.all(from(o in Order, where: Order.recent(o))

I’m afraid this is a limitation of the way Ecto.Query.from/2 uses Macro.postwalk to parse the query expressions. But I would like someone to confirm (or refute) my suspicion. And could Ecto theoretically be extended to support this case, or is it a hard limitation?

Thank you.

2

I realize this is a bit of a tangent, but the more normal way to compose queries is:

def recent(queryable \\ __MODULE__) do
  from q in queryable, where: q.inserted_at > ago(3, "day")
end

Order |> Order.recent() |> Repo.all

# or

from o in Order.recent(), where: o.foo == :bar # if you want to filter other things too

Can you elaborate on what you’re trying to achieve here with the macro?

3

Hi Ben, thanks for your suggestion. Unfortunately it doesn’t fit my needs, as the part which I want to put in a macro would be nested somewhere deep in a query among other “where” conditions. It doesn’t lend itself to the easy composition like in your example. I realize I could use dynamic, so there is a way to do what I need. But I’m rather exploring what else is possible.