mix: add task to compact the database

lib/mix/tasks/compact_database.ex

@@ -0,0 +1,57 @@
+defmodule Mix.Tasks.CompactDatabase do
+  @moduledoc """
+  Compact the database by flattening the object graph.
+  """
+
+  require Logger
+
+  use Mix.Task
+  import Mix.Ecto
+  import Ecto.Query
+  alias Pleroma.{Repo, Object, Activity}
+
+  defp maybe_compact(%Activity{data: %{"object" => %{"id" => object_id}}} = activity) do
+    data =
+      activity.data
+      |> Map.put("object", object_id)
+
+    {:ok, activity} =
+      Activity.change(activity, %{data: data})
+      |> Repo.update()
+
+    {:ok, activity}
+  end
+
+  defp maybe_compact(%Activity{} = activity), do: {:ok, activity}
+
+  defp activity_query(min_id, max_id) do
+    from(
+      a in Activity,
+      where: fragment("?->>'type' = 'Create'", a.data),
+      where: a.id >= ^min_id,
+      where: a.id < ^max_id
+    )
+  end
+
+  def run(args) do
+    Application.ensure_all_started(:pleroma)
+
+    max = Repo.aggregate(Activity, :max, :id)
+    Logger.info("Considering #{max} activities")
+
+    chunks = 0..(round(max / 100))
+
+    Enum.each(chunks, fn (i) ->
+      min = i * 100
+      max = min + 100
+
+      activity_query(min, max)
+      |> Repo.all()
+      |> Enum.each(&maybe_compact/1)
+
+      IO.write(".")
+    end)
+
+    Logger.info("Finished.")
+  end
+end