presto-main/src/main/java/io/prestosql/sql/planner/optimizations/IndexJoinOptimizer.java/Visitor/visitAggregation
class Visitor:            @Override
            public Map<Symbol, Symbol> visitAggregation(AggregationNode node, Set<Symbol> lookupSymbols)
            {
                Set<Symbol> groupByLookupSymbols = lookupSymbols.stream()
                        .filter(node.getGroupingKeys()::contains)
                        .collect(toImmutableSet());
                checkState(!groupByLookupSymbols.isEmpty(), "No lookup symbols were able to pass through the aggregation group by");
                return node.getSource().accept(this, groupByLookupSymbols);
            }