presto-main/src/main/java/io/prestosql/operator/TopNProcessor.java/TopNProcessor/updateMemoryReservation
class TopNProcessor:    private void updateMemoryReservation()
    {
        requireNonNull(topNBuilder, "topNBuilder is null");
        localUserMemoryContext.setBytes(topNBuilder.getEstimatedSizeInBytes());
    }