Merge branch 'fix/migration-alter-citext-field-with-key' into 'develop'

Fix occasional migration failures

See merge request pleroma/pleroma!1373

priv/repo/migrations/20170522160642_case_insensivtivity.exs

@@ -1,19 +1,31 @@
 defmodule Pleroma.Repo.Migrations.CaseInsensivtivity do
   use Ecto.Migration
 
+  # Two-steps alters are intentional.
+  # When alter of 2 columns is done in a single operation,
+  # inconsistent failures happen because of index on `email` column.
+
   def up do
     execute("create extension if not exists citext")
+
     alter table(:users) do
-      modify :email, :citext
+      modify(:email, :citext)
-      modify :nickname, :citext
+    end
+
+    alter table(:users) do
+      modify(:nickname, :citext)
     end
   end
 
   def down do
     alter table(:users) do
-      modify :email, :string
+      modify(:email, :string)
-      modify :nickname, :string
     end
+
+    alter table(:users) do
+      modify(:nickname, :string)
+    end
+
     execute("drop extension if exists citext")
   end
 end