presto-main/src/main/java/io/prestosql/operator/aggregation/minmaxby/BlockAndBlockPositionStateSerializer.java/BlockAndBlockPositionStateSerializer/readFirstField
class BlockAndBlockPositionStateSerializer:    @Override
    void readFirstField(Block block, int position, BlockAndBlockPositionValueState state)
    {
        state.setFirst((Block) firstType.getObject(block, position));
    }