presto-main/src/main/java/io/prestosql/operator/aggregation/histogram/GroupedTypedHistogram.java/GroupedTypedHistogram/ValueNode
class GroupedTypedHistogram:        ValueNode(int nodePointer)
        {
            checkState(nodePointer > -1, "ValueNode must point to a non-empty node");
            this.nodePointer = nodePointer;
        }