presto-main/src/main/java/io/prestosql/operator/aggregation/arrayagg/LegacyArrayAggregationGroupState.java/LegacyArrayAggregationGroupState/add
class LegacyArrayAggregationGroupState:    @Override
    public void add(Block block, int position)
    {
        BlockBuilder blockBuilder = blockBuilders.get(getGroupId());
        long startSize = 0;
        if (blockBuilder == null) {
            blockBuilder = type.createBlockBuilder(null, 4);
            blockBuilders.set(getGroupId(), blockBuilder);
        }
        else {
            startSize = blockBuilder.getRetainedSizeInBytes();
        }
        type.appendTo(block, position, blockBuilder);
        size += blockBuilder.getRetainedSizeInBytes() - startSize;
    }