Merge index during table creation

db/migrate/20170918072948_create_job_artifacts.rb

@@ -17,6 +17,7 @@ class CreateJobArtifacts < ActiveRecord::Migration
       t.string :file
       t.foreign_key :ci_builds, column: :job_id, on_delete: :cascade
+      t.index [:job_id, :file_type], unique: true
     end
   end
 end

db/migrate/20171130145523_uniqueness_contraint_job_artifact_file_type.rb

-class UniquenessContraintJobArtifactFileType < ActiveRecord::Migration
-  include Gitlab::Database::MigrationHelpers
-
-  # Set this constant to true if this migration requires downtime.
-  DOWNTIME = false
-
-  disable_ddl_transaction!
-
-  def up
-    add_concurrent_index :ci_job_artifacts, [:job_id, :file_type], unique: true
-  end
-
-  def down
-    remove_concurrent_index :ci_job_artifacts, [:job_id, :file_type]
-  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: 20171130145523) do
+ActiveRecord::Schema.define(version: 20171124150326) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"