Add RankedTrend concern for trends classes (#29388)

app/models/concerns/ranked_trend.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+module RankedTrend
+  extend ActiveSupport::Concern
+
+  included do
+    scope :by_rank, -> { order(rank: :desc) }
+    scope :ranked_below, ->(value) { where(rank: ..value) }
+  end
+
+  class_methods do
+    def recalculate_ordered_rank
+      connection
+        .exec_update(<<~SQL.squish)
+          UPDATE #{table_name}
+          SET rank = inner_ordered.calculated_rank
+          FROM (
+            SELECT id, row_number() OVER w AS calculated_rank
+            FROM #{table_name}
+            WINDOW w AS (
+              PARTITION BY language
+              ORDER BY score DESC
+            )
+          ) inner_ordered
+          WHERE #{table_name}.id = inner_ordered.id
+        SQL
+    end
+  end
+end