Object: remove context_id field

30 to 70% of the objects in the object table are simple JSON objects
containing a single field, 'id', being the context's ID. The reason for
the creation of an object per context seems to be an old relic from the
StatusNet era, and has only been used nowadays as an helper for threads
in Pleroma-FE via the `pleroma.conversation_id` field in status views.
An object per context was created, and its numerical ID (table column)
was used and stored as 'context_id' in the object and activity along
with the full 'context' URI/string.

This commit removes this field and stops creation of objects for each
context, which will also allow incoming activities to use activity IDs
as contexts, something which was not possible before, or would have been
very broken under most circumstances.

The `pleroma.conversation_id` field has been reimplemented in a way to
maintain backwards-compatibility by calculating a CRC32 of the full
context URI/string in the object, instead of relying on the row ID for
the created context object.

lib/pleroma/object.ex

@@ -208,10 +208,6 @@ defmodule Pleroma.Object do
     end
   end
 
-  def context_mapping(context) do
-    Object.change(%Object{}, %{data: %{"id" => context}})
-  end
-
   def make_tombstone(%Object{data: %{"id" => id, "type" => type}}, deleted \\ DateTime.utc_now()) do
     %ObjectTombstone{
       id: id,

lib/pleroma/web/activity_pub/object_validators/article_note_page_validator.ex

@@ -94,7 +94,7 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.ArticleNotePageValidator do
   defp validate_data(data_cng) do
     data_cng
     |> validate_inclusion(:type, ["Article", "Note", "Page"])
-    |> validate_required([:id, :actor, :attributedTo, :type, :context, :context_id])
+    |> validate_required([:id, :actor, :attributedTo, :type, :context])
     |> CommonValidations.validate_any_presence([:cc, :to])
     |> CommonValidations.validate_fields_match([:actor, :attributedTo])
     |> CommonValidations.validate_actor_presence()

lib/pleroma/web/activity_pub/object_validators/common_fixes.ex

@@ -22,14 +22,12 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.CommonFixes do
   end
 
   def fix_object_defaults(data) do
-    %{data: %{"id" => context}, id: context_id} =
-      Utils.create_context(data["context"] || data["conversation"])
+    context = Utils.maybe_create_context(data["context"] || data["conversation"])
 
     %User{follower_address: follower_collection} = User.get_cached_by_ap_id(data["attributedTo"])
 
     data
     |> Map.put("context", context)
-    |> Map.put("context_id", context_id)
     |> cast_and_filter_recipients("to", follower_collection)
     |> cast_and_filter_recipients("cc", follower_collection)
     |> cast_and_filter_recipients("bto", follower_collection)

lib/pleroma/web/activity_pub/object_validators/event_validator.ex

@@ -62,7 +62,7 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.EventValidator do
   defp validate_data(data_cng) do
     data_cng
     |> validate_inclusion(:type, ["Event"])
-    |> validate_required([:id, :actor, :attributedTo, :type, :context, :context_id])
+    |> validate_required([:id, :actor, :attributedTo, :type, :context])
     |> CommonValidations.validate_any_presence([:cc, :to])
     |> CommonValidations.validate_fields_match([:actor, :attributedTo])
     |> CommonValidations.validate_actor_presence()

lib/pleroma/web/activity_pub/object_validators/question_validator.ex

@@ -80,7 +80,7 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.QuestionValidator do
   defp validate_data(data_cng) do
     data_cng
     |> validate_inclusion(:type, ["Question"])
-    |> validate_required([:id, :actor, :attributedTo, :type, :context, :context_id])
+    |> validate_required([:id, :actor, :attributedTo, :type, :context])
     |> CommonValidations.validate_any_presence([:cc, :to])
     |> CommonValidations.validate_fields_match([:actor, :attributedTo])
     |> CommonValidations.validate_actor_presence()

lib/pleroma/web/activity_pub/utils.ex

@@ -154,22 +154,7 @@ defmodule Pleroma.Web.ActivityPub.Utils do
     Notification.get_notified_from_activity(%Activity{data: object}, false)
   end
 
-  def create_context(context) do
-    context = context || generate_id("contexts")
-
-    # Ecto has problems accessing the constraint inside the jsonb,
-    # so we explicitly check for the existed object before insert
-    object = Object.get_cached_by_ap_id(context)
-
-    with true <- is_nil(object),
-         changeset <- Object.context_mapping(context),
-         {:ok, inserted_object} <- Repo.insert(changeset) do
-      inserted_object
-    else
-      _ ->
-        object
-    end
-  end
+  def maybe_create_context(context), do: context || generate_id("contexts")
 
   @doc """
   Enqueues an activity for federation if it's local
@@ -201,18 +186,16 @@ defmodule Pleroma.Web.ActivityPub.Utils do
     |> Map.put_new("id", "pleroma:fakeid")
     |> Map.put_new_lazy("published", &make_date/0)
     |> Map.put_new("context", "pleroma:fakecontext")
-    |> Map.put_new("context_id", -1)
     |> lazy_put_object_defaults(true)
   end
 
   def lazy_put_activity_defaults(map, _fake?) do
-    %{data: %{"id" => context}, id: context_id} = create_context(map["context"])
+    context = maybe_create_context(map["context"])
 
     map
     |> Map.put_new_lazy("id", &generate_activity_id/0)
     |> Map.put_new_lazy("published", &make_date/0)
     |> Map.put_new("context", context)
-    |> Map.put_new("context_id", context_id)
     |> lazy_put_object_defaults(false)
   end
 
@@ -226,7 +209,6 @@ defmodule Pleroma.Web.ActivityPub.Utils do
       |> Map.put_new("id", "pleroma:fake_object_id")
       |> Map.put_new_lazy("published", &make_date/0)
       |> Map.put_new("context", activity["context"])
-      |> Map.put_new("context_id", activity["context_id"])
       |> Map.put_new("fake", true)
 
     %{activity | "object" => object}
@@ -239,7 +221,6 @@ defmodule Pleroma.Web.ActivityPub.Utils do
       |> Map.put_new_lazy("id", &generate_object_id/0)
       |> Map.put_new_lazy("published", &make_date/0)
       |> Map.put_new("context", activity["context"])
-      |> Map.put_new("context_id", activity["context_id"])
 
     %{activity | "object" => object}
   end

lib/pleroma/web/common_api/utils.ex

@@ -449,35 +449,6 @@ defmodule Pleroma.Web.CommonAPI.Utils do
 
   def get_report_statuses(_, _), do: {:ok, nil}
 
-  # DEPRECATED mostly, context objects are now created at insertion time.
-  def context_to_conversation_id(context) do
-    with %Object{id: id} <- Object.get_cached_by_ap_id(context) do
-      id
-    else
-      _e ->
-        changeset = Object.context_mapping(context)
-
-        case Repo.insert(changeset) do
-          {:ok, %{id: id}} ->
-            id
-
-          # This should be solved by an upsert, but it seems ecto
-          # has problems accessing the constraint inside the jsonb.
-          {:error, _} ->
-            Object.get_cached_by_ap_id(context).id
-        end
-    end
-  end
-
-  def conversation_id_to_context(id) do
-    with %Object{data: %{"id" => context}} <- Repo.get(Object, id) do
-      context
-    else
-      _e ->
-        {:error, dgettext("errors", "No such conversation")}
-    end
-  end
-
   def validate_character_limit("" = _full_payload, [] = _attachments) do
     {:error, dgettext("errors", "Cannot post an empty status without attachments")}
   end

lib/pleroma/web/mastodon_api/views/status_view.ex

@@ -61,7 +61,7 @@ defmodule Pleroma.Web.MastodonAPI.StatusView do
     do: context_id
 
   defp get_context_id(%{data: %{"context" => context}}) when is_binary(context),
-    do: Utils.context_to_conversation_id(context)
+    do: :erlang.crc32(context)
 
   defp get_context_id(_), do: nil