presto-main/src/main/java/io/prestosql/operator/aggregation/builder/InMemoryHashAggregationBuilder.java/Aggregator/processPage
class Aggregator:        public void processPage(GroupByIdBlock groupIds, Page page)
        {
            if (step.isInputRaw()) {
                aggregation.addInput(groupIds, page);
            }
            else {
                aggregation.addIntermediate(groupIds, page.getBlock(intermediateChannel));
            }
        }