Use explode_outer() when rows have null values.
tor. 16. feb. 2023 kl. 16:48 skrev Navneet <kr.navneetve...@gmail.com>:
> I am not expert, may be try if this works:
> In order to achieve the desired output using the explode() method in
> Java, you can create a User-Defined Function (UDF) that zips the lists
> in each row and returns the resulting list. Here's an example
> implementation:
>
> typescript
> Copy code
> import org.apache.spark.sql.Row;
> import org.apache.spark.sql.api.java.UDF1;
> import org.apache.spark.sql.types.DataTypes;
>
> public class ZipRows implements UDF1<Row, Row> {
> @Override
> public Row call(Row row) {
> List<String> list1 = row.getList(0);
> List<String> list2 = row.getList(1);
> List<String> list3 = row.getList(2);
> List<List<String>> zipped = new ArrayList<>();
> for (int i = 0; i < list1.size(); i++) {
> List<String> sublist = new ArrayList<>();
> sublist.add(list1.get(i));
> sublist.add(list2.get(i));
> sublist.add(list3.get(i));
> zipped.add(sublist);
> }
> return RowFactory.create(zipped);
> }
> }
> This UDF takes a Row as input, which contains the three lists in each
> row of the original DataFrame. It then zips these lists using a loop
> that creates a new sublist for each element in the lists. Finally, it
> returns a new Row that contains the zipped list.
>
> You can then use this UDF in combination with explode() to achieve the
> desired output:
>
> javascript
> Copy code
> import org.apache.spark.sql.Dataset;
> import org.apache.spark.sql.Row;
> import static org.apache.spark.sql.functions.*;
>
> // assuming you have a Dataset<Row> called "df"
> df.withColumn("zipped", callUDF(new ZipRows(),
>
> DataTypes.createArrayType(DataTypes.createArrayType(DataTypes.StringType))),
> "col1", "col2", "col3")
> .selectExpr("explode(zipped) as zipped")
> .selectExpr("zipped[0] as col1", "zipped[1] as col2", "zipped[2] as col3")
> .show();
> This code first adds a new column called "zipped" to the DataFrame
> using the callUDF() function, which applies the ZipRows UDF to the
> "col1", "col2", and "col3" columns. It then uses explode() to explode
> the "zipped" column, and finally selects the three sub-elements of the
> zipped list as separate columns using selectExpr(). The output should
> be the desired DataFrame.
>
>
>
> Regards,
> Navneet Kr
>
>
> On Thu, 16 Feb 2023 at 00:07, Enrico Minack <i...@enrico.minack.dev>
> wrote:
> >
> > You have to take each row and zip the lists, each element of the result
> becomes one new row.
> >
> > So turn write a method that turns
> > Row(List("A","B","null"), List("C","D","null"),
> List("E","null","null"))
> > into
> > List(List("A","C","E"), List("B","D","null"),
> List("null","null","null"))
> > and use flatmap with that method.
> >
> > In Scala, this would read:
> >
> > df.flatMap { row => (row.getSeq[String](0), row.getSeq[String](1),
> row.getSeq[String](2)).zipped.toIterable }.show()
> >
> > Enrico
> >
> >
> > Am 14.02.23 um 22:54 schrieb sam smith:
> >
> > Hello guys,
> >
> > I have the following dataframe:
> >
> > col1
> >
> > col2
> >
> > col3
> >
> > ["A","B","null"]
> >
> > ["C","D","null"]
> >
> > ["E","null","null"]
> >
> >
> >
> > I want to explode it to the following dataframe:
> >
> > col1
> >
> > col2
> >
> > col3
> >
> > "A"
> >
> > "C"
> >
> > "E"
> >
> > "B"
> >
> > "D"
> >
> > "null"
> >
> > "null"
> >
> > "null"
> >
> > "null"
> >
> >
> > How to do that (preferably in Java) using the explode() method ? knowing
> that something like the following won't yield correct output:
> >
> > for (String colName: dataset.columns())
> > dataset=dataset.withColumn(colName,explode(dataset.col(colName)));
> >
> >
> >
>
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