#fixed code
                              @Override
  public List<String> getPartitionColumns(String schema, String table) throws VerdictDBDbmsException {
    List<String> partition = new ArrayList<>();
    DbmsQueryResult queryResult = execute(syntax.getPartitionCommand(schema, table));
    while (queryResult.next()) {
      partition.add((String) queryResult.getValue(0));
    }

    return partition;
  }
#vulnerable code 
                              @Override
  public List<String> getPartitionColumns(String schema, String table) throws VerdictDBDbmsException {
    List<String> partition = new ArrayList<>();
    DbmsQueryResult queryResult = execute(syntax.getPartitionCommand(schema, table));
    JdbcResultSet jdbcResultSet = new JdbcResultSet(queryResult);
    // the result of postgresql is a vector of column index

    try {
      if (syntax instanceof PostgresqlSyntax) {
        queryResult.next();
        Object o = jdbcResultSet.getObject(1);
        String[] arr = o.toString().split(" ");
        List<Pair<String, String>> columns = getColumns(schema, table);
        for (int i=0; i<arr.length; i++) {
          partition.add(columns.get(Integer.valueOf(arr[i])-1).getKey());
        }
      }
      else {
        while (queryResult.next()) {
          partition.add(jdbcResultSet.getString(1));
        }
      }
    } catch (SQLException e) {
      throw new VerdictDBDbmsException(e);
    } finally {
      jdbcResultSet.close();
    }
    jdbcResultSet.close();
    return partition;
  } 
                            #location 5 
                            #vulnerability type NULL_DEREFERENCE