How getSet of Text from row in cassandra

Question

I have a table with < frozen < set < text > > > , column. I can't understand how I may read a column value from a row.Trying below but not able to get pass through.

  else if (key.getType() == DataType.frozenSet(text))
                    {
                str  =  row.getSet( , )
                    }

I tried the below , but i see nothing is printing out from that frozen set column.

    public static void main(String[] args) throws FileNotFoundException {
    long startTime = System.currentTimeMillis();

    PrintWriter pw = new PrintWriter(new File("test.csv"));
            String keyspace = "xxxxx";
            String table = "xxxxxx";
            String username = "xxxx";
            String password = "xxxx";
            String host     = "xxxxxxx";
            double count = 0;


            Cluster.Builder clusterBuilder = Cluster.builder()
                                            .addContactPoints(host)
                                            .withCredentials(username, password);
            Cluster cluster = clusterBuilder.build();
            Session session = cluster.connect(keyspace);

            Statement stmt = new SimpleStatement("SELECT * FROM " + table);
            stmt.setFetchSize(2000);
            ResultSet rs = session.execute(stmt);
            Iterator<Row> iter = rs.iterator();

            while ( !rs.isFullyFetched()) {
              if (rs.getAvailableWithoutFetching() == 120 )
               rs.fetchMoreResults();
               Row row = iter.next();
               if ( rs != null )
               {
                       StringBuilder line = new StringBuilder();
                       for (Definition key : row.getColumnDefinitions().asList())
                       {
                               String val = myGetValue(key, row);
                               line.append("\"");
                               line.append(val);
                               line.append("\"");
                               line.append(',');
                       }
                       line.deleteCharAt(line.length()-1);
                       line.append('\n');
                       pw.write(line.toString());


                       System.out.println(line.toString());
                       ++count;
               }
            }
            pw.close();
            session.close();
            cluster.close();
            System.out.println(count + "\t rows copied into csv");
            long endTime = System.currentTimeMillis();
            System.out.println("Took "+(endTime - startTime) + " ms"); 
        }
public static String myGetValue(Definition key, Row row)
{
    String str = ""; 

    if (key != null)
    {
            String col = key.getName();
            try
            {
            if (key.getType() == DataType.cdouble())
            {
                    str = new Double(row.getDouble(col)).toString();
            }
            else if (key.getType() == DataType.cint())
            {
                    str = new Integer(row.getInt(col)).toString();
            }
            else if (key.getType() == DataType.uuid())
            {
                    str = row.getUUID(col).toString();
            }
            else if (key.getType() == DataType.cfloat())
            {
                    str = new Float(row.getFloat(col)).toString();
            }


               else if (key.getType() == DataType.timestamp())
            {
                    str = row.getDate(col).toString();
                   SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd HH:mm:ssZ");
                    str = fmt.format(row.getDate(col));


            }

               else if (key.getType().equals(DataType.set(DataType.text()) ))
            { 
                    Set<String> st1 = row.getSet(i, String.class);
                   str = st1.toString();
                    ++i;
            }


            else
            {
                    str = row.getString(col);
            }
            } catch (Exception e)
            {
                 str = "";     
            }
    }

    return str;
}
}

schema:

create table view_page_details(
  clickid uuid,
  view text,
  clickin int,
  names frozen <set<text>>,
  msg_view text,
  number_of_times int,
  primary key ((clickid, view, clickin), names);

cqlsh output for that specific 'names' column in that table:

|                                 {').'{'2', 'STOP', 'williams', 'The', 'appts:', 'at', 'family''s', 'first', 'of', 'one', 'reminder', 'starts', 'to', 'your'}

|                                 {'2'{'2', 'STOP', 'shane', 'The', 'appts:', 'at', 'family''s', 'first', 'of'}

|                      {'1', '2/1/15.'{'2', 'STOP', 'brete', 'The', 'appts:', 'at', 'family''s', 'first', 'of', 'one', 'reminder', 'starts', 'to', 'your'}

My program output for that specific 'names'column in that table:

                           ,,
                           ,,
                           ,,
                           ,,

From what i observed by debugging line by line , String val = myGetValue(key, row); gets the entire row value correctly from cluster, when returns value from that function its not giving out the specified column value. Not sure if something wrong inside the function logic for that specific column.

Answer 1

The first argument is index of the column in the ResultSet. By accessing this way you need to get get columns by their index not by name or key.

Set<String> mySet  =  row.getSet(index, String.class);

If you don't have the index, then you will need keep a counter as you iterate the keys.

You can find out more from the javadoc

https://docs.datastax.com/en/latest-java-driver-api/com/datastax/driver/core/GettableByIndexData.html#getSet-int-java.lang.Class-

longer answer: I'm really guessing what most of your code does, but with the given schema I can output the set using this code:

        Row row = rs.one();
        String str = "";

        int i = 0;
        Iterator<ColumnDefinitions.Definition> it = rs.getColumnDefinitions().iterator();
        while (it.hasNext()) {
            ColumnDefinitions.Definition key = it.next();
            if (key.getType().equals(DataType.set(DataType.varchar()))) {
                Set<String> st1 = row.getSet(i, String.class);
                str = st1.toString();
                System.out.println(str);
            }
            i++;
        }