presto-main/src/main/java/io/prestosql/sql/planner/optimizations/HashGenerationOptimizer.java/HashGenerationOptimizer/withHashComputation
class HashGenerationOptimizer:        public HashComputationSet withHashComputation(PlanNode node, Optional<HashComputation> hashComputation)
        {
            return pruneSymbols(node.getOutputSymbols()).withHashComputation(hashComputation);
        }