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elixirphoenix-frameworkecto

How to insert default data into an Ecto database?

I have a table which contains the job types that can be created, and a migration and schema to go with these, however I would like to insert default data into the table on migration / creation.

Currently, I resort to just adding the data myself and hoping I don't accidentally rollback too far, but I would like a more robust solution to this.

Solution

  • These are called "seeds".

    In your mix.exs, create an alias like this:

      defp aliases do
    [
      "ecto.setup": ["ecto.create", "ecto.migrate", "run priv/repo/seeds.exs"],

    Now just create that file priv/repo/seeds.exs and put something like this in it:

    case Mix.env() do
  :dev ->
    IO.puts("Let's add some data!")
    {:ok, job_0} = YourModule.create_job(%{name: "job_0"})
    {:ok, job_1} = YourModule.create_job(%{name: "job_1"})

  _ ->
    nil
end

    Note that I am careful to only run "seeds" in the :dev environment.

    With all this setup, you can just do mix ecto.drop to drop the current database and then mix ecto.setup to create a new database, run migrations and populate with seed data.

    What I have written is purely illustrative. You are free to make any kind of mix alias and seeds script you want.