+
+ if @object.respond_to? :name and params[:ensure_unique_name]
+ # Record the original name. See below.
+ name_stem = @object.name
+ counter = 1
+ end
+
+ begin
+ @object.save!
+ rescue ActiveRecord::RecordNotUnique => rn
+ raise unless params[:ensure_unique_name]
+
+ # Dig into the error to determine if it is specifically calling out a
+ # (owner_uuid, name) uniqueness violation. In this specific case, and
+ # the client requested a unique name with ensure_unique_name==true,
+ # update the name field and try to save again. Loop as necessary to
+ # discover a unique name. It is necessary to handle name choosing at
+ # this level (as opposed to the client) to ensure that record creation
+ # never fails due to a race condition.
+ raise unless rn.original_exception.is_a? PG::UniqueViolation
+
+ # Unfortunately ActiveRecord doesn't abstract out any of the
+ # necessary information to figure out if this the error is actually
+ # the specific case where we want to apply the ensure_unique_name
+ # behavior, so the following code is specialized to Postgres.
+ err = rn.original_exception
+ detail = err.result.error_field(PG::Result::PG_DIAG_MESSAGE_DETAIL)
+ raise unless /^Key \(owner_uuid, name\)=\([a-z0-9]{5}-[a-z0-9]{5}-[a-z0-9]{15}, .*?\) already exists\./.match detail
+
+ # OK, this exception really is just a unique name constraint
+ # violation, and we've been asked to ensure_unique_name.
+ counter += 1
+ @object.uuid = nil
+ @object.name = "#{name_stem} (#{counter})"
+ redo
+ end while false