presto-main/src/main/java/io/prestosql/operator/HashBuilderOperator.java/HashBuilderOperator/getAndIncrementPartitionIndex
class HashBuilderOperator:        private int getAndIncrementPartitionIndex(Lifespan lifespan)
        {
            return partitionIndexManager.compute(lifespan, (k, v) -> v == null ? 1 : v + 1) - 1;
        }