adds date and booth/officer trace fields to poll partial results

db/migrate/20170201113206_adds_fields_to_poll_partial_results.rb

@@ -0,0 +1,9 @@
+class AddsFieldsToPollPartialResults < ActiveRecord::Migration
+  def change
+    add_column :poll_partial_results, :date, :date
+    add_column :poll_partial_results, :booth_assignment_id, :integer
+    add_column :poll_partial_results, :officer_assignment_id, :integer
+
+    add_index :poll_partial_results, [:booth_assignment_id, :date]
+  end
+end