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
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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
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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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