How to change field type in Ecto?

Question

I have a schema:

schema "editables" do
    field :title, :string
    field :content, :string

    timestamps
  end

Now I want to change the type of one field form :integer to :binary. What's the correct way of writing the migration because using add is not working...?

def change do
    alter table(:editables) do
      add :title, :binary
      add :content, :binary

      timestamps
    end
  end

Solution

You have to use modify/3 to change the type. add/3 is only for adding new columns.

alter table(:editables) do
  modify :content, :binary
end

Comments

[Paulo Janeiro]

but now i'm getting this error: ERROR (datatype_mismatch): column "title" cannot be cast automatically to type bytea

[Gazler]

@PauloJaneiro If you can delete your database then deleting and recreating will fix it. The problem is that it won't be able to automatically migrate the type.

[Gazler]

@PauloJaneiro be sure to update your schema in your model too.

[Paulo Janeiro]

Right. So this cannot be done when in production...Thanks Gazler.

[Gazler]

One of your records will be causing the issue with incompatible data (maybe NULLs?) Check out postgresql.org/message-id/… - it can be done but not with the Ecto migration DSL.

[Jonathan Soifer]

In my case I successfully migrated from :string to :text but I had to restart the server afterwards. I was getting a weird PostgreSQL error.