1 files changed, 43 insertions, 0 deletions
diff --git a/db/post_migrate/20180604123514_cleanup_stages_position_migration.rb b/db/post_migrate/20180604123514_cleanup_stages_position_migration.rb
new file mode 100644
index 00000000000..73c23dffca0
--- /dev/null
+++ b/db/post_migrate/20180604123514_cleanup_stages_position_migration.rb
@@ -0,0 +1,43 @@
+class CleanupStagesPositionMigration < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  TMP_INDEX_NAME = 'tmp_id_stage_position_partial_null_index'.freeze
+
+  disable_ddl_transaction!
+
+  class Stages < ActiveRecord::Base
+    include EachBatch
+    self.table_name = 'ci_stages'
+  end
+
+  def up
+    disable_statement_timeout
+
+    Gitlab::BackgroundMigration.steal('MigrateStageIndex')
+
+    unless index_exists_by_name?(:ci_stages, TMP_INDEX_NAME)
+      add_concurrent_index(:ci_stages, :id, where: 'position IS NULL', name: TMP_INDEX_NAME)
+    end
+
+    migratable = <<~SQL
+      position IS NULL AND EXISTS (
+        SELECT 1 FROM ci_builds WHERE stage_id = ci_stages.id AND stage_idx IS NOT NULL
+      )
+    SQL
+
+    Stages.where(migratable).each_batch(of: 1000) do |batch|
+      batch.pluck(:id).each do |stage|
+        Gitlab::BackgroundMigration::MigrateStageIndex.new.perform(stage, stage)
+      end
+    end
+
+    remove_concurrent_index_by_name(:ci_stages, TMP_INDEX_NAME)
+  end
+
+  def down
+    if index_exists_by_name?(:ci_stages, TMP_INDEX_NAME)
+      remove_concurrent_index_by_name(:ci_stages, TMP_INDEX_NAME)
+    end
+  end
+end