only start automigrator in prod env

config/config.exs

@@ -20,6 +20,8 @@ config :lokal, LokalWeb.Endpoint,
   pubsub_server: Lokal.PubSub,
   live_view: [signing_salt: "zOLgd3lr"]
 
+config :lokal, Lokal.Application, automigrate: false
+
 # Configures the mailer
 #
 # By default it uses the "Local" adapter which stores the emails

config/prod.exs

@@ -18,6 +18,8 @@ config :lokal, Lokal.Repo,
   url: "ecto://postgres:postgres@localhost/lokal",
   pool_size: 10
 
+config :lokal, Lokal.Application, automigrate: true
+
 # Do not print debug messages in production
 config :logger, level: :info
 

lib/lokal/application.ex

@@ -15,13 +15,17 @@ defmodule Lokal.Application do
       # Start the PubSub system
       {Phoenix.PubSub, name: Lokal.PubSub},
       # Start the Endpoint (http/https)
-      LokalWeb.Endpoint,
+      LokalWeb.Endpoint
       # Start a worker by calling: Lokal.Worker.start_link(arg)
       # {Lokal.Worker, arg}
-      # Automatically migrate on start
-      Lokal.Repo.Migrator
     ]
 
+    # Automatically migrate on start in prod
+    children =
+      if Application.get_env(:lokal, Lokal.Application, automigrate: false)[:automigrate],
+        do: children ++ [Lokal.Repo.Migrator],
+        else: children
+
     # See https://hexdocs.pm/elixir/Supervisor.html
     # for other strategies and supported options
     opts = [strategy: :one_for_one, name: Lokal.Supervisor]