presto-main/src/main/java/io/prestosql/operator/aggregation/AbstractGroupCollectionAggregationState.java/AbstractGroupCollectionAggregationState/appendAtChannel
class AbstractGroupCollectionAggregationState:    protected final void appendAtChannel(int channel, Block block, int position)
    {
        currentPageBuilder.getType(channel).appendTo(block, position, currentPageBuilder.getBlockBuilder(channel));
    }