Make FixBrokenGoals migration idempotent (#3405)

* Make FixBrokenGoals migration idempotent

The migration in question was renamed in order to fix order of executing migrations when run
from the ground up (via https://github.com/plausible/analytics/pull/3378).

As a side effect, it's executed again on databases that had it applied earlier, with
a different timestamp prefix.

As this migration is safe to run multiple times, it was modified to make forward
migration work gracefully when constraint already exists.

* Add `pending-migrations.sh` release script

lib/plausible_release.ex

@@ -25,6 +25,13 @@ defmodule Plausible.Release do
     IO.puts("Migrations successful!")
   end
 
+  def pending_migrations do
+    prepare()
+    IO.puts("Pending migrations")
+    IO.puts("")
+    Enum.each(repos(), &list_pending_migrations_for/1)
+  end
+
   def seed do
     prepare()
     # Run seed script
@@ -92,6 +99,28 @@ defmodule Plausible.Release do
     {:ok, _, _} = Ecto.Migrator.with_repo(repo, &Ecto.Migrator.run(&1, :up, all: true))
   end
 
+  defp list_pending_migrations_for(repo) do
+    IO.puts("Listing pending migrations for #{repo}")
+    IO.puts("")
+
+    migration_directory = Ecto.Migrator.migrations_path(repo)
+
+    pending =
+      repo
+      |> Ecto.Migrator.migrations([migration_directory])
+      |> Enum.filter(fn {status, _version, _migration} -> status == :down end)
+
+    if pending == [] do
+      IO.puts("No pending migrations")
+    else
+      Enum.each(pending, fn {_, version, migration} ->
+        IO.puts("* #{version}_#{migration}")
+      end)
+    end
+
+    IO.puts("")
+  end
+
   defp ensure_repo_created(repo) do
     IO.puts("create #{inspect(repo)} database if it doesn't exist")
 

priv/repo/migrations/20230914071244_fix_broken_goals.exs

@@ -9,6 +9,11 @@ defmodule Plausible.Repo.Migrations.FixBrokenGoals do
     UPDATE goals SET page_path = NULL WHERE page_path IS NOT NULL AND event_name IS NOT NULL
     """)
 
+    execute("""
+    ALTER TABLE goals
+    DROP CONSTRAINT IF EXISTS check_event_name_or_page_path;
+    """)
+
     execute("""
      ALTER TABLE goals
      ADD CONSTRAINT check_event_name_or_page_path
@@ -23,7 +28,7 @@ defmodule Plausible.Repo.Migrations.FixBrokenGoals do
   def down do
     execute("""
     ALTER TABLE goals
-    DROP CONSTRAINT check_event_name_or_page_path;
+    DROP CONSTRAINT IF EXISTS check_event_name_or_page_path;
     """)
   end
 end

rel/overlays/pending-migrations.sh

@@ -0,0 +1,6 @@
+#!/bin/sh
+# lists pending migrations
+
+BIN_DIR=$(dirname "$0")
+
+"${BIN_DIR}"/bin/plausible eval Plausible.Release.pending_migrations