That gives you all distinct tuples of those col values. You need to select
the distinct values of each col one at a time. Sure just collect() the
result as you do here.
On Fri, Feb 10, 2023, 3:34 PM sam smith <qustacksm2123...@gmail.com> wrote:
> I want to get the distinct values of each column in a List (is it good
> practice to use List here?), that contains as first element the column
> name, and the other element its distinct values so that for a dataset we
> get a list of lists, i do it this way (in my opinion no so fast):
>
> List<List<String>> finalList = new ArrayList<List<String>>();
> Dataset<Row> df = spark.read().format("csv").option("header",
> "true").load("/pathToCSV");
> String[] columnNames = df.columns();
> for (int i=0;i<columnNames.length;i++) {
> List<String> columnList = new ArrayList<String>();
>
> columnList.add(columnNames[i]);
>
>
> List<Row> columnValues =
> df.filter(org.apache.spark.sql.functions.col(columnNames[i]).isNotNull()).select(columnNames[i]).distinct().collectAsList();
> for (int j=0;j<columnValues.size();j++)
> columnList.add(columnValues.get(j).apply(0).toString());
>
> finalList.add(columnList);
>
>
> How to improve this?
>
> Also, can I get the results in JSON format?
>
