Reschedule the migration to populate fork networks

Rescheduling will make sure the fork networks with a deleted source
project are created.

db/post_migrate/20171124150326_reschedule_fork_network_creation.rb

@@ -0,0 +1,27 @@
+class RescheduleForkNetworkCreation < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  MIGRATION = 'PopulateForkNetworksRange'.freeze
+  BATCH_SIZE = 100
+  DELAY_INTERVAL = 15.seconds
+
+  disable_ddl_transaction!
+
+  class ForkedProjectLink < ActiveRecord::Base
+    include EachBatch
+
+    self.table_name = 'forked_project_links'
+  end
+
+  def up
+    say 'Populating the `fork_networks` based on existing `forked_project_links`'
+
+    queue_background_migration_jobs_by_range_at_intervals(ForkedProjectLink, MIGRATION, DELAY_INTERVAL, batch_size: BATCH_SIZE)
+  end
+
+  def down
+    # nothing
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20171124132536) do
+ActiveRecord::Schema.define(version: 20171124150326) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"