Add the RedirectRoute#path index setup_postgresql

db/post_migrate/20180306164012_add_path_index_to_redirect_routes.rb

@@ -22,17 +22,17 @@ class AddPathIndexToRedirectRoutes < ActiveRecord::Migration
 
     disable_statement_timeout
 
-    if_not_exists = Gitlab::Database.version.to_f >= 9.5 ? "IF NOT EXISTS" : ""
-
-    # Unique index on lower(path) across both types of redirect_routes:
-    execute("CREATE UNIQUE INDEX CONCURRENTLY #{if_not_exists} #{INDEX_NAME} ON redirect_routes (lower(path) varchar_pattern_ops);")
+    unless index_exists_by_name?(:redirect_routes, INDEX_NAME)
+      execute("CREATE UNIQUE INDEX CONCURRENTLY #{INDEX_NAME} ON redirect_routes (lower(path) varchar_pattern_ops);")
+    end
   end
 
   def down
-    return unless Gitlab::Database.postgresql?
-
-    disable_statement_timeout
-
-    execute("DROP INDEX IF EXISTS #{INDEX_NAME};")
+    # Do nothing in the DOWN. Since the index above is originally created in the
+    # `ReworkRedirectRoutesIndexes`. This migration wouldn't have actually
+    # created any new index.
+    #
+    # This migration is only here to be called form `setup_postgresql.rake` so
+    # any newly created database would have this index.
   end
 end

lib/tasks/migrate/setup_postgresql.rake

@@ -8,6 +8,7 @@ task setup_postgresql: :environment do
   require Rails.root.join('db/migrate/20170503185032_index_redirect_routes_path_for_like')
   require Rails.root.join('db/migrate/20171220191323_add_index_on_namespaces_lower_name.rb')
   require Rails.root.join('db/migrate/20180215181245_users_name_lower_index.rb')
+  require Rails.root.join('db/post_migrate/20180306164012_add_path_index_to_redirect_routes.rb')
 
   NamespacesProjectsPathLowerIndexes.new.up
   AddUsersLowerUsernameEmailIndexes.new.up
@@ -17,4 +18,5 @@ task setup_postgresql: :environment do
   IndexRedirectRoutesPathForLike.new.up
   AddIndexOnNamespacesLowerName.new.up
   UsersNameLowerIndex.new.up
+  AddPathIndexToRedirectRoutes.new.up
 end