1 files changed, 41 insertions, 0 deletions
diff --git a/db/post_migrate/20180216121020_fill_pages_domain_verification_code.rb b/db/post_migrate/20180216121020_fill_pages_domain_verification_code.rb
new file mode 100644
index 00000000000..d423673d2a5
--- /dev/null
+++ b/db/post_migrate/20180216121020_fill_pages_domain_verification_code.rb
@@ -0,0 +1,41 @@
+class FillPagesDomainVerificationCode < ActiveRecord::Migration
+  DOWNTIME = false
+
+  class PagesDomain < ActiveRecord::Base
+    include EachBatch
+  end
+
+  # Allow this migration to resume if it fails partway through
+  disable_ddl_transaction!
+
+  def up
+    PagesDomain.where(verification_code: [nil, '']).each_batch do |relation|
+      connection.execute(set_codes_sql(relation))
+
+      # Sleep 2 minutes between batches to not overload the DB with dead tuples
+      sleep(2.minutes) unless relation.reorder(:id).last == PagesDomain.reorder(:id).last
+    end
+
+    change_column_null(:pages_domains, :verification_code, false)
+  end
+
+  def down
+    change_column_null(:pages_domains, :verification_code, true)
+  end
+
+  private
+
+  def set_codes_sql(relation)
+    ids = relation.pluck(:id)
+    whens = ids.map { |id| "WHEN #{id} THEN '#{SecureRandom.hex(16)}'" }
+
+    <<~SQL
+      UPDATE pages_domains
+      SET verification_code =
+        CASE id
+        #{whens.join("\n")}
+        END
+      WHERE id IN(#{ids.join(',')})
+    SQL
+  end
+end