added Tag schema

lib/pleroma/tag.ex

@@ -0,0 +1,37 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Tag do
+  use Ecto.Schema
+
+  import Ecto.Query
+
+  alias Pleroma.Repo
+  alias Pleroma.Web.ActivityPub.MRF
+
+  @type t :: %__MODULE__{}
+
+  schema "tags" do
+    field(:name, :string)
+
+    timestamps()
+  end
+
+  @spec upsert(String.t()) :: {:ok, t()} | {:error, Ecto.Changeset.t()}
+  def upsert(name) do
+    %__MODULE__{}
+    |> Ecto.Changeset.change(name: name)
+    |> Ecto.Changeset.unique_constraint(:name)
+    |> Repo.insert(on_conflict: :nothing, conflict_target: :name)
+  end
+
+  @spec list_tags() :: list(String.t())
+  def list_tags do
+    from(u in __MODULE__, select: u.name)
+    |> Repo.all()
+    |> Kernel.++(MRF.TagPolicy.policy_tags())
+    |> Enum.uniq()
+    |> Enum.sort()
+  end
+end

lib/pleroma/user.ex

@@ -1259,15 +1259,6 @@ defmodule Pleroma.User do
     |> Repo.all()
   end
 
-  @spec list_tags() :: list(String.t())
-  def list_tags do
-    from(
-      u in __MODULE__,
-      select: type(fragment("DISTINCT unnest(?)", u.tags), :string)
-    )
-    |> Repo.all()
-  end
-
   def increase_note_count(%User{} = user) do
     User
     |> where(id: ^user.id)

lib/pleroma/web/admin_api/controllers/tag_controller.ex

@@ -25,11 +25,7 @@ defmodule Pleroma.Web.AdminAPI.TagController do
   action_fallback(AdminAPI.FallbackController)
 
   def list(%{assigns: %{user: _admin}} = conn, _) do
-    tags =
-      Pleroma.User.list_tags()
-      |> Kernel.++(Pleroma.Web.ActivityPub.MRF.TagPolicy.policy_tags())
-      |> Enum.uniq()
-      |> Enum.sort()
+    tags = Pleroma.Tag.list_tags()
 
     json(conn, tags)
   end

priv/repo/migrations/20201012093959_create_tags.exs

@@ -0,0 +1,27 @@
+defmodule Pleroma.Repo.Migrations.CreateTags do
+  use Ecto.Migration
+
+  def up do
+    create_if_not_exists table(:tags) do
+      add(:name, :string, null: false)
+      timestamps()
+    end
+
+    create_if_not_exists(unique_index(:tags, :name))
+    flush()
+
+    execute(collect_user_tags_query())
+  end
+
+  def down do
+    drop_if_exists(table(:tags))
+  end
+
+  defp collect_user_tags_query do
+    """
+    INSERT INTO tags(name, inserted_at, updated_at)
+    SELECT DISTINCT unnest(tags), now(), now() from users
+    ON CONFLICT DO NOTHING
+    """
+  end
+end

test/support/factory.ex

@@ -490,4 +490,8 @@ defmodule Pleroma.Factory do
       context: ["home"]
     }
   end
+
+  def tag_factory do
+    %Pleroma.Tag{name: "verify"}
+  end
 end

test/web/admin_api/controllers/tag_controller_test.exs

@@ -32,9 +32,9 @@ defmodule Pleroma.Web.AdminAPI.TagControllerTest do
 
   describe "GET /api/pleroma/admin/users/tag" do
     test "it returns user tags and mrf policy tags", %{conn: conn} do
-      insert(:user, %{tags: ["x"]})
-      insert(:user, %{tags: ["y"]})
-      insert(:user, %{tags: ["unchanged"]})
+      insert(:tag, name: "x")
+      insert(:tag, name: "y")
+      insert(:tag, name: "unchanged")
 
       response =
         conn