multi-import of all items in parallel

app/models/user.rb

···
   has_many :quotes, foreign_key: 'actor_id'
   has_many :pins, foreign_key: 'actor_id'
   has_many :imports
+
+  def all_pending_items
+    [:likes, :reposts, :quotes, :pins].map { |x| self.send(x).pending.to_a }.reduce(&:+)
+  end
 end

lib/tasks/import.rake

···
   case ENV['COLLECTION']
   when 'likes'
     queue = ItemQueue.new(pending ? user.likes.pending.to_a : [])
-    importer = LikesImporter.new(ENV['USER'])
+    importers = [LikesImporter.new(ENV['USER'])]
   when 'reposts'
     queue = ItemQueue.new(pending ? user.reposts.pending.to_a : [])
-    importer = RepostsImporter.new(ENV['USER'])
+    importers = [RepostsImporter.new(ENV['USER'])]
   when 'posts'
     queue = ItemQueue.new(pending ? user.quotes.pending.to_a + user.pins.pending.to_a : [])
-    importer = PostsImporter.new(ENV['USER'])
+    importers = [PostsImporter.new(ENV['USER'])]
+  when 'all'
+    queue = ItemQueue.new(pending ? user.all_pending_items : [])
+    importers = [
+      LikesImporter.new(ENV['USER']),
+      RepostsImporter.new(ENV['USER']),
+      PostsImporter.new(ENV['USER'])
+    ]
   when nil
     raise "Required COLLECTION parameter missing"
   else
···
 
   report = ImportReport.new
 
-  importer.item_queue = queue
-  importer.report = report
-
   downloader = PostDownloader.new
   downloader.report = report
 
···
     exit
   }
 
-  importer.run_import(ENV['UNTIL'])
+  import_threads = importers.map do |import|
+    import.item_queue = queue
+    import.report = report
+
+    Thread.new { import.run_import(ENV['UNTIL']) }
+  end
+
+  import_threads.each { |i| i.join }
 
   downloader.stop_when_empty = true
   download_thread.join