Repo.embedded_load/3 convenience

[narrowtux]

When I write queries that filter within embedded fields that are backed by JSON, I see no simple way to select the filtered embeds so they're correctly loaded using the ecto type system.

My example goes like this:

      limits_query = from l in License,
        select: %{
          limit: fragment("jsonb_array_elements(?)", l.limits),
          valid_from: l.valid_from,
          valid_until: l.valid_until
        }

      query = from l in subquery(limits_query),
        select: l.limit,
        where: fragment("? >= now()", l.valid_until),
        where: fragment("? <= now()", l.valid_from),
        where: fragment("(? -> 'category') = ?::jsonb", l.limit, ^category)

The License schema has embeds_many :limits, Limit which is backed by a jsonb field.

What I tried to load the resulting json documents into actual %Limit{} structs was to map the results through the Repo.load/2 function like this:

Repo.all(query)
|> Enum.map(&Repo.load(Limit, &1))

However, since the primary key type is Ecto.UUID, it won't actually work with Ecto.UUID.load since that one expects a binary UUID and not a UUID in text form.

So I propose a new convenience function embedded_load(schema, data, format) that uses Ecto.Type.embedded_load/3 internally so I can fix my example like this:

Repo.all(query)
|> Enum.map(&Repo.embedded_load(Limit, &1, :json))

If there's any other way to prevent having to load manually I'd be glad to hear it :)

[josevalim]

A PR would be welcome!

[narrowtux]

I can try, I'm stuck now anyway :D

[josevalim]

If you want to get unstuck, you can return this select: map(l, :limits) and then extract them out in Elixir land.

[narrowtux]

It was actually pretty easy, in repo/schema.ex:

  def embedded_load(_adapter, schema_or_types, data, format) do
    do_load(schema_or_types, data, &Ecto.Type.embedded_load(&1, &2, format))
  end

PR will follow shorltly

[josevalim]

Closing in favor of PR!