presto-main/src/main/java/io/prestosql/operator/aggregation/multimapagg/SingleMultimapAggregationState.java/SingleMultimapAggregationState/forEach
class SingleMultimapAggregationState:    @Override
    public void forEach(MultimapAggregationStateConsumer consumer)
    {
        for (int i = 0; i < keyBlockBuilder.getPositionCount(); i++) {
            consumer.accept(keyBlockBuilder, valueBlockBuilder, i);
        }
    }