WIP and notes

Author: tompave

lib/fun_with_flags/store/persistent/ecto/record.ex

@@ -13,7 +13,7 @@ defmodule FunWithFlags.Store.Persistent.Ecto.Record do
     field :gate_type, :string
     field :target, :string
     field :enabled, :boolean
-    timestamps()
+    # timestamps()
   end
 
   @fields [:flag_name, :gate_type, :target, :enabled]

priv/ecto_repo/migrations/00000000000000_create_feature_flags_table.exs

@@ -12,7 +12,7 @@ defmodule FunWithFlags.Dev.EctoRepo.Migrations.CreateFeatureFlagsTable do
       add :gate_type, :string, null: false
       add :target, :string, null: false
       add :enabled, :boolean, null: false
-      timestamps()
+      # timestamps()
     end
 
     create index(

priv/ecto_repo/migrations/00000000000002_add_timestamps.exs

@@ -22,10 +22,28 @@ defmodule FunWithFlags.Dev.EctoRepo.Migrations.EnsureColumnsAreNotNull do
         # timestamp columns exist, do nothing
         true
 
+      # !! This doesn't work in postgres because the error fails the transaction,
+      # and then any other statement is ignored.
+      # It works in MySQL though.
+      #
       {:error, _} ->
+        # We must set a default value, because Ecto timestamps come with a
+        # NOT NULL constraint, and without a default the the migration will
+        # fail if the table already contains records.
+        #
+        # WARNING: adding a new column with a default value is a blocking operation
+        # on Postgres and can be problematic on MySQL unless a special DDL is used.
+        # This is usually fine for small tables, but it requires special care and
+        # planning for tables that contain a lot of flag data.
+        #
+        current_time = NaiveDateTime.utc_now()
+
         # Assume error is from timestamp columns not existing, run migration
         alter table(:fun_with_flags_toggles) do
-          timestamps()
+          # timestamps(default: current_time)
+
+          # Alternative: declare the timestamps as nullable? Does Ecto complain?
+          timestamps null: true
         end
     end
   end