How to store array with Ecto using Postgres

Question

I would like to store an array of floating point values with Ecto using Postgres. I'm using Ecto with the Phoenix Framework and Elixir.

How would I define my model and migration for this?

I haven't tried much, except searching the web, which didn't find anything useful :-(

I did try defining a model with a schema like this:

  schema "my_model" do
    field :my_array, :array

    timestamps
  end

which gave an error "invalid or unknown type :array for field :my_array"

Solution 1

I found the answer in the list of primitive types for Ecto.Schema here:

Ecto.Schema

The answer is to define the type like this:

  schema "my_model" do
    field :my_array, {:array, :float}

    timestamps
  end

Solution 2

As Josh wrote use the array type from Ecto.Schema

In the model:

schema "my_model" do
  field :my_array, {:array, inner_type}
end

@neildaemond Migration:

alter table(:my_models) do
  add :my_array, {:array, inner_type}
end

Replace inner_type with one of the valid types, such as :string.

You can also do the same thing with a map type:

schema "my_model" do
  field :my_map, {:map, inner_type}
end

Comments

[neildaemond]

Thanks, how would you write the migration for that?

[pmarreck]

Any idea how to properly construct a form that would let someone input the elements of this array or map?

[Bartłomiej Skwira]

@pmarreck have you looked at Form docs? hexdocs.pm/phoenix_html/Phoenix.HTML.Form.html I usually work on an API apps so I don't use forms and can't help

[pmarreck]

I have, don't see anything helpful there in this case

[Sash]

Here is a generator example: mix phx.gen.schema Blog.Post blog_posts tags:array:string

[xji]

@pmarreck This post seems to be relevant.

[wodow]

The example from @sash generates a migration with the relevant line add :tags, {:array, :string}