Bump build stage id reference migration identifier

db/post_migrate/20170526185921_migrate_build_stage_reference.rb

@@ -3,25 +3,17 @@ class MigrateBuildStageReference < ActiveRecord::Migration
 
   DOWNTIME = false
 
-  disable_ddl_transaction!
+  ##
+  # This is an empty migration, content has been moved to a new one:
+  # post migrate 20170526190000 MigrateBuildStageReferenceAgain
+  #
+  # See gitlab-org/gitlab-ce!12337 for more details.
 
   def up
-    disable_statement_timeout
-
-    stage_id = Arel.sql <<-SQL.strip_heredoc
-      (SELECT id FROM ci_stages
-         WHERE ci_stages.pipeline_id = ci_builds.commit_id
-           AND ci_stages.name = ci_builds.stage)
-    SQL
-
-    update_column_in_batches(:ci_builds, :stage_id, stage_id) do |table, query|
-      query.where(table[:stage_id].eq(nil))
-    end
+    # noop
   end
 
   def down
-    disable_statement_timeout
-
-    update_column_in_batches(:ci_builds, :stage_id, nil)
+    # noop
   end
 end

db/post_migrate/20170526190000_migrate_build_stage_reference_again.rb

+class MigrateBuildStageReferenceAgain < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    disable_statement_timeout
+
+    stage_id = Arel.sql <<-SQL.strip_heredoc
+      (SELECT id FROM ci_stages
+         WHERE ci_stages.pipeline_id = ci_builds.commit_id
+           AND ci_stages.name = ci_builds.stage)
+    SQL
+
+    update_column_in_batches(:ci_builds, :stage_id, stage_id) do |table, query|
+      query.where(table[:stage_id].eq(nil))
+    end
+  end
+
+  def down
+    disable_statement_timeout
+
+    update_column_in_batches(:ci_builds, :stage_id, nil)
+  end
+end