Question

我必须添加值为UUID的新列。我使用Spark 1.4 Java使用以下代码完成了这项工作。

StructType objStructType = inputDataFrame.schema();
        StructField []arrStructField=objStructType.fields();
        List<StructField> fields = new ArrayList<StructField>();
        List<StructField> newfields = new ArrayList<StructField>();
        List <StructField> listFields = Arrays.asList(arrStructField);
        StructField a = DataTypes.createStructField(leftCol,DataTypes.StringType, true);
        fields.add(a);
        newfields.addAll(listFields);
        newfields.addAll(fields);
        final int size = objStructType.size();

    JavaRDD<Row> rowRDD =   inputDataFrame.javaRDD().map(new Function<Row, Row>() {
        private static final long serialVersionUID = 3280804931696581264L;
        public Row call(Row tblRow) throws Exception {

                Object[] newRow = new Object[size+1];
                int rowSize=    tblRow.length();
                for (int itr = 0; itr < rowSize; itr++)
                {
                    if(tblRow.apply(itr)!=null)
                    {
                        newRow[itr] = tblRow.apply(itr);
                    }

                }
                newRow[size] = UUID.randomUUID().toString();
                return RowFactory.create(newRow);

        }
    });



    inputDataFrame = objsqlContext.createDataFrame(rowRDD, DataTypes.createStructType(newfields));

我想知道在Spark 2中是否有一些巧妙的方法。请建议。

Answer 1

您可以注册udf以获取UUID，并使用callUDF功能向您的inputDataFrame添加新列。请使用Spark 2.0查看示例代码。

public class SparkUUIDSample {
public static void main(String[] args) {
    SparkSession spark = SparkSession.builder().appName("SparkUUIDSample").master("local[*]").getOrCreate();
    //sample input data
    List<Tuple2<String, String>> inputList = new ArrayList<Tuple2<String, String>>();
    inputList.add(new Tuple2<String, String>("A", "v1"));
    inputList.add(new Tuple2<String, String>("B", "v2"));
    //dataset
    Dataset<Row> df = spark.createDataset(inputList, Encoders.tuple(Encoders.STRING(), Encoders.STRING())).toDF("key", "value");
    df.show();
    //register udf
    UDF1<String, String> uuid = str -> UUID.randomUUID().toString();
    spark.udf().register("uuid", uuid, DataTypes.StringType);
    //call udf
    df.select(col("*"), callUDF("uuid", col("value"))).show();
    //stop
    spark.stop();
  }     
}

SpakrSQL使用UUID生成新列

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