Refactor migrations in a way it can work with MySQL properly

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

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: 20180810155213) do
+ActiveRecord::Schema.define(version: 20180807153545) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"

ee/db/migrate/20180720120726_create_packages_package_files.rb

@@ -22,6 +22,8 @@ class CreatePackagesPackageFiles < ActiveRecord::Migration
       t.text :file, null: false
     end
 
+    add_concurrent_index :packages_package_files, [:package_id, :file_name]
+
     add_concurrent_foreign_key :packages_package_files, :packages_packages,
       column: :package_id,
       on_delete: :cascade
@@ -32,6 +34,10 @@ class CreatePackagesPackageFiles < ActiveRecord::Migration
       remove_foreign_key :packages_package_files, column: :package_id
     end
 
+    if index_exists?(:packages_package_files, [:package_id, :file_name])
+      remove_concurrent_index :packages_package_files, [:package_id, :file_name]
+    end
+
     if table_exists?(:packages_package_files)
       drop_table :packages_package_files
     end

ee/db/migrate/20180720121404_create_packages_maven_metadata.rb

@@ -18,6 +18,8 @@ class CreatePackagesMavenMetadata < ActiveRecord::Migration
       t.string :path, limit: 512, null: false
     end
 
+    add_concurrent_index :packages_maven_metadata, [:package_id, :path]
+
     add_concurrent_foreign_key :packages_maven_metadata, :packages_packages,
       column: :package_id,
       on_delete: :cascade
@@ -28,6 +30,10 @@ class CreatePackagesMavenMetadata < ActiveRecord::Migration
       remove_foreign_key :packages_maven_metadata, column: :package_id
     end
 
+    if index_exists?(:packages_maven_metadata, [:package_id, :path])
+      remove_concurrent_index :packages_maven_metadata, [:package_id, :path]
+    end
+
     if table_exists?(:packages_maven_metadata)
       drop_table :packages_maven_metadata
     end

ee/db/migrate/20180810155213_add_more_indices_to_packages.rb

-class AddMoreIndicesToPackages < ActiveRecord::Migration
-  include Gitlab::Database::MigrationHelpers
-
-  DOWNTIME = false
-
-  disable_ddl_transaction!
-
-  def up
-    add_concurrent_index :packages_package_files, [:package_id, :file_name]
-    add_concurrent_index :packages_maven_metadata, [:package_id, :path]
-  end
-
-  def down
-    remove_concurrent_index :packages_package_files, [:package_id, :file_name]
-    remove_concurrent_index :packages_maven_metadata, [:package_id, :path]
-  end
-end