1 files changed, 33 insertions, 0 deletions
diff --git a/db/post_migrate/20170628080858_migrate_stage_id_reference_in_background.rb b/db/post_migrate/20170628080858_migrate_stage_id_reference_in_background.rb
new file mode 100644
index 00000000000..f31015d77a3
--- /dev/null
+++ b/db/post_migrate/20170628080858_migrate_stage_id_reference_in_background.rb
@@ -0,0 +1,33 @@
+class MigrateStageIdReferenceInBackground < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  BATCH_SIZE = 10000
+  RANGE_SIZE = 1000
+  MIGRATION = 'MigrateBuildStageIdReference'.freeze
+
+  disable_ddl_transaction!
+
+  class Build < ActiveRecord::Base
+    self.table_name = 'ci_builds'
+    include ::EachBatch
+  end
+
+  ##
+  # It will take around 3 days to process 20M ci_builds.
+  #
+  def up
+    Build.where(stage_id: nil).each_batch(of: BATCH_SIZE) do |relation, index|
+      relation.each_batch(of: RANGE_SIZE) do |relation|
+        range = relation.pluck('MIN(id)', 'MAX(id)').first
+
+        BackgroundMigrationWorker
+          .perform_in(index * 2.minutes, MIGRATION, range)
+      end
+    end
+  end
+
+  def down
+    # noop
+  end
+end