public boolean containsOnCompletion(Synchronization onCompletion) {
if (unitOfWork != null) {
// if there is an unit of work then the completions is moved there
return unitOfWork.containsSynchronization(onCompletion);
} else {
// check temporary completions if no unit of work yet
return onCompletions != null && onCompletions.contains(onCompletion);
}
}