Add a test which would rollback db and migrate again

Closes #29106

.gitlab-ci.yml

@@ -222,6 +222,13 @@ rake db:migrate:reset:
   script:
     - bundle exec rake db:migrate:reset
 
+rake db:rollback:
+  stage: test
+  <<: *use-db
+  <<: *dedicated-runner
+  script:
+    - bundle exec rake db:rollback db:migrate STEP=120
+
 rake db:seed_fu:
   stage: test
   <<: *use-db

db/migrate/20160919145149_add_group_id_to_labels.rb

@@ -12,8 +12,8 @@ class AddGroupIdToLabels < ActiveRecord::Migration
   end
 
   def down
+    remove_foreign_key :labels, column: :group_id
     remove_index :labels, :group_id if index_exists? :labels, :group_id
-    remove_foreign_key :labels, :namespaces, column: :group_id
     remove_column :labels, :group_id
   end
 end

db/migrate/20161020083353_add_pipeline_id_to_merge_request_metrics.rb

@@ -32,8 +32,8 @@ class AddPipelineIdToMergeRequestMetrics < ActiveRecord::Migration
   end
 
   def down
+    remove_foreign_key :merge_request_metrics, column: :pipeline_id
     remove_index :merge_request_metrics, :pipeline_id if index_exists? :merge_request_metrics, :pipeline_id
-    remove_foreign_key :merge_request_metrics, :ci_commits, column: :pipeline_id
     remove_column :merge_request_metrics, :pipeline_id
   end
 end

db/migrate/20161031171301_add_project_id_to_subscriptions.rb

@@ -9,6 +9,7 @@ class AddProjectIdToSubscriptions < ActiveRecord::Migration
   end
 
   def down
+    remove_foreign_key :subscriptions, column: :project_id
     remove_column :subscriptions, :project_id
   end
 end

db/migrate/20161207231621_create_environment_name_unique_index.rb

@@ -12,7 +12,7 @@ class CreateEnvironmentNameUniqueIndex < ActiveRecord::Migration
   end
 
   def down
-    remove_index :environments, [:project_id, :name], unique: true
-    add_concurrent_index :environments, [:project_id, :name]
+    remove_index :environments, [:project_id, :name]
+    add_concurrent_index :environments, [:project_id, :name], unique: true
   end
 end

db/migrate/20161209153400_add_unique_index_for_environment_slug.rb

@@ -14,6 +14,6 @@ class AddUniqueIndexForEnvironmentSlug < ActiveRecord::Migration
   end
 
   def down
-    remove_index :environments, [:project_id, :slug], unique: true if index_exists? :environments, [:project_id, :slug]
+    remove_index :environments, [:project_id, :slug] if index_exists? :environments, [:project_id, :slug]
   end
 end

db/migrate/20170124174637_add_foreign_keys_to_timelogs.rb

@@ -49,6 +49,16 @@ class AddForeignKeysToTimelogs < ActiveRecord::Migration
     Timelog.where('issue_id IS NOT NULL').update_all("trackable_id = issue_id, trackable_type = 'Issue'")
     Timelog.where('merge_request_id IS NOT NULL').update_all("trackable_id = merge_request_id, trackable_type = 'MergeRequest'")
 
+    constraint =
+      if Gitlab::Database.postgresql?
+        'CONSTRAINT'
+      else
+        'FOREIGN KEY'
+      end
+
+    execute "ALTER TABLE timelogs DROP #{constraint} fk_timelogs_issues_issue_id"
+    execute "ALTER TABLE timelogs DROP #{constraint} fk_timelogs_merge_requests_merge_request_id"
+
     remove_columns :timelogs, :issue_id, :merge_request_id
   end
 end

db/migrate/20170216141440_drop_index_for_builds_project_status.rb

@@ -3,6 +3,6 @@ class DropIndexForBuildsProjectStatus < ActiveRecord::Migration
   DOWNTIME = false
 
   def change
-    remove_index(:ci_commits, [:gl_project_id, :status])
+    remove_index(:ci_commits, column: [:gl_project_id, :status])
   end
 end

db/post_migrate/20170206101007_remove_trackable_columns_from_timelogs.rb

@@ -18,6 +18,7 @@ class RemoveTrackableColumnsFromTimelogs < ActiveRecord::Migration
   # disable_ddl_transaction!
 
   def change
-    remove_columns :timelogs, :trackable_id, :trackable_type
+    remove_column :timelogs, :trackable_id, :integer
+    remove_column :timelogs, :trackable_type, :string
   end
 end