[Issue Sorting] Improve migration

db/post_migrate/20170309171644_reset_relative_position_for_issue.rb

@@ -7,10 +7,9 @@ class ResetRelativePositionForIssue < ActiveRecord::Migration
   DOWNTIME = false
 
   def up
-    execute <<-EOS
-      UPDATE issues SET relative_position = NULL
-        WHERE issues.relative_position IS NOT NULL;
-    EOS
+    update_column_in_batches(:issues, :relative_position, nil) do |table, query|
+      query.where(table[:relative_position].not_eq(nil))
+    end
   end
 
   def down

spec/models/concerns/relative_positioning_spec.rb

@@ -130,7 +130,6 @@ describe Issue, 'RelativePositioning' do
       expect(new_issue.relative_position).to eq(6000 + RelativePositioning::DISTANCE)
     end
 
-
     it 'positions issue in the middle of other two if distance is not big enough' do
       issue.update relative_position: 100
       issue1.update relative_position: 400