3

我在 Java 中使用过 RDD.flatMap 函数。现在尝试使用 DataFrames。

他们说：

public <R> RDD<R> flatMap(scala.Function1<org.apache.spark.sql.Row,
    scala.collection.TraversableOnce<R>> f, scala.reflect.ClassTag<R> evidence$4)

通过首先将一个函数应用于此 DataFrame 的所有行，然后将结果展平，返回一个新的 RDD。

指定者：接口RDDApi中的flatMap

但是当我尝试这个时Function1，它迫使我重写很多很多未实现的方法。这就是我得到的：

    RDD<Row> res = df.flatMap(new Function1<Row, TraversableOnce<Row>>() {

        @Override
        public <A> Function1<Row, A> andThen(
                Function1<TraversableOnce<Row>, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcDD$sp(
                Function1<Object, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcDF$sp(
                Function1<Object, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcDI$sp(
                Function1<Object, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcDJ$sp(
                Function1<Object, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcFD$sp(
                Function1<Object, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcFF$sp(
                Function1<Object, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcFI$sp(
                Function1<Object, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcFJ$sp(
                Function1<Object, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcID$sp(
                Function1<Object, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcIF$sp(
                Function1<Object, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcII$sp(
                Function1<Object, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcIJ$sp(
                Function1<Object, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcJD$sp(
                Function1<Object, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcJF$sp(
                Function1<Object, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcJI$sp(
                Function1<Object, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcJJ$sp(
                Function1<Object, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcVD$sp(
                Function1<BoxedUnit, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcVF$sp(
                Function1<BoxedUnit, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcVI$sp(
                Function1<BoxedUnit, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcVJ$sp(
                Function1<BoxedUnit, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcZD$sp(
                Function1<Object, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcZF$sp(
                Function1<Object, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcZI$sp(
                Function1<Object, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<Object, A> andThen$mcZJ$sp(
                Function1<Object, A> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public TraversableOnce<Row> apply(Row arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public double apply$mcDD$sp(double arg0) {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public double apply$mcDF$sp(float arg0) {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public double apply$mcDI$sp(int arg0) {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public double apply$mcDJ$sp(long arg0) {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public float apply$mcFD$sp(double arg0) {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public float apply$mcFF$sp(float arg0) {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public float apply$mcFI$sp(int arg0) {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public float apply$mcFJ$sp(long arg0) {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public int apply$mcID$sp(double arg0) {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public int apply$mcIF$sp(float arg0) {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public int apply$mcII$sp(int arg0) {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public int apply$mcIJ$sp(long arg0) {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public long apply$mcJD$sp(double arg0) {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public long apply$mcJF$sp(float arg0) {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public long apply$mcJI$sp(int arg0) {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public long apply$mcJJ$sp(long arg0) {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public void apply$mcVD$sp(double arg0) {
            // TODO Auto-generated method stub

        }

        @Override
        public void apply$mcVF$sp(float arg0) {
            // TODO Auto-generated method stub

        }

        @Override
        public void apply$mcVI$sp(int arg0) {
            // TODO Auto-generated method stub

        }

        @Override
        public void apply$mcVJ$sp(long arg0) {
            // TODO Auto-generated method stub

        }

        @Override
        public boolean apply$mcZD$sp(double arg0) {
            // TODO Auto-generated method stub
            return false;
        }

        @Override
        public boolean apply$mcZF$sp(float arg0) {
            // TODO Auto-generated method stub
            return false;
        }

        @Override
        public boolean apply$mcZI$sp(int arg0) {
            // TODO Auto-generated method stub
            return false;
        }

        @Override
        public boolean apply$mcZJ$sp(long arg0) {
            // TODO Auto-generated method stub
            return false;
        }

        @Override
        public <A> Function1<A, TraversableOnce<Row>> compose(
                Function1<A, Row> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, Object> compose$mcDD$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, Object> compose$mcDF$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, Object> compose$mcDI$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, Object> compose$mcDJ$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, Object> compose$mcFD$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, Object> compose$mcFF$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, Object> compose$mcFI$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, Object> compose$mcFJ$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, Object> compose$mcID$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, Object> compose$mcIF$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, Object> compose$mcII$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, Object> compose$mcIJ$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, Object> compose$mcJD$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, Object> compose$mcJF$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, Object> compose$mcJI$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, Object> compose$mcJJ$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, BoxedUnit> compose$mcVD$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, BoxedUnit> compose$mcVF$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, BoxedUnit> compose$mcVI$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, BoxedUnit> compose$mcVJ$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, Object> compose$mcZD$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, Object> compose$mcZF$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, Object> compose$mcZI$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public <A> Function1<A, Object> compose$mcZJ$sp(
                Function1<A, Object> arg0) {
            // TODO Auto-generated method stub
            return null;
        }
    }, evidence$4);

这看起来很奇怪，但我继续制作evidence$4：

ClassTag<Row> evidence$4 = scala.reflect.ClassTag$.MODULE$.apply(Row.class);

我的意图是玩弄flatMap（当然是在 DataFrames 上而不是在 RDD 上）。所以我不需要对Row. 可以按原样返回输入而不做任何更改。

所以我想我只需要在apply方法上进行更改。

    @Override
    public TraversableOnce<Row> apply(Row arg0) {
        // TODO Auto-generated method stub
        return null;
    }

但同样，我应该如何从中TraversableOnce<Row>获得Row？

另外，我尝试的方法是否正确？还是我错过了什么？

我正在使用 Apache Spark 1.3.1

4

1 回答 1

1

您应该执行以下操作：

RDD<Row> res = df.flatMap(new AbstractFunction1<Row, TraversableOnce<Row>>() {
  public TraversableOnce<Row> apply(Row row) {
    return new ListSet<Row>().$plus(row); //Note the updated list is returned from $plus()
  }
}, evidence$4);

这将与 类似map，只是有更多的更改自由。例如，为了过滤掉一些东西，你可以new ListSet<Row>()在你想返回它的时候返回它，或者保持当前的行为。flatMap非常灵活。

（似乎从 Java 集合到 Scala 集合的转换并非易事。）

于 2015-05-25T15:48:07.170 回答