Introduce instances admin page

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

priv/repo/migrations/20211223141104_add_instance_materialized_view.exs

@@ -0,0 +1,64 @@
+defmodule Mobilizon.Storage.Repo.Migrations.AddInstanceMaterializedView do
+  use Ecto.Migration
+
+  def up do
+    execute("""
+    CREATE MATERIALIZED VIEW instances AS
+    SELECT
+      a.domain,
+      COUNT(DISTINCT(p.id)) AS person_count,
+      COUNT(DISTINCT(g.id)) AS group_count,
+      COUNT(DISTINCT(e.id)) AS event_count,
+      COUNT(f1.id) AS followers_count,
+      COUNT(f2.id) AS followings_count,
+      COUNT(r.id) AS reports_count,
+      SUM(COALESCE((m.file->>'size')::int, 0)) AS media_size
+    FROM actors a
+    LEFT JOIN actors p ON a.id = p.id AND p.type = 'Person'
+    LEFT JOIN actors g ON a.id = g.id AND g.type = 'Group'
+    LEFT JOIN events e ON a.id = e.organizer_actor_id
+    LEFT JOIN followers f1 ON a.id = f1.actor_id
+    LEFT JOIN followers f2 ON a.id = f2.target_actor_id
+    LEFT JOIN reports r ON r.reported_id = a.id
+    LEFT JOIN medias m ON m.actor_id = a.id
+    WHERE a.domain IS NOT NULL
+    GROUP BY a.domain;
+    """)
+
+    execute("""
+    CREATE OR REPLACE FUNCTION refresh_instances()
+    RETURNS trigger AS $$
+    BEGIN
+      REFRESH MATERIALIZED VIEW instances;
+      RETURN NULL;
+    END;
+    $$ LANGUAGE plpgsql;
+    """)
+
+    execute("""
+    DROP TRIGGER IF EXISTS refresh_instances_trigger ON actors;
+    """)
+
+    execute("""
+    CREATE TRIGGER refresh_instances_trigger
+    AFTER INSERT OR UPDATE OR DELETE
+    ON actors
+    FOR EACH STATEMENT
+    EXECUTE PROCEDURE refresh_instances();
+    """)
+
+    create_if_not_exists(unique_index("instances", [:domain]))
+  end
+
+  def down do
+    drop_if_exists(unique_index("instances", [:domain]))
+
+    execute("""
+    DROP FUNCTION IF EXISTS refresh_instances() CASCADE;
+    """)
+
+    execute("""
+    DROP MATERIALIZED VIEW IF EXISTS instances;
+    """)
+  end
+end