code: private String getIndexesToDrop(CmsSetupDb dbCon, String tablename) {
  
          List<String> indexes = new ArrayList<String>();
          String tableIndex = readQuery(QUERY_SHOW_INDEX);
          Map<String, String> replacer = new HashMap<String, String>();
          replacer.put(REPLACEMENT_TABLENAME, tablename);
          CmsSetupDBWrapper db = null;
          try {
              db = dbCon.executeSqlStatement(tableIndex, replacer);
              while (db.getResultSet().next()) {
                  String index = db.getResultSet().getString(FIELD_INDEX);
                  if (!indexes.contains(index)) {
                      indexes.add(index);
                  }
              }
  
          } catch (SQLException e) {
              e.printStackTrace();
          } finally {
              if (db != null) {
                  db.close();
              }
          }
  
          StringBuffer dropIndex = new StringBuffer();
          for (Iterator<String> it = indexes.iterator(); it.hasNext();) {
              String index = it.next();
              if (index.equals(PRIMARY_KEY)) {
                  dropIndex.append("DROP PRIMARY KEY, ");
              } else {
                  dropIndex.append("DROP INDEX ");
                  dropIndex.append(index);
                  dropIndex.append(", ");
              }
          }
          return dropIndex.toString();
      }
docs: Returns the string of the indexes that shall be dropped before adding the final new indexes.<p>
  
  @param dbCon the connection to the database
  @param tablename the table to drop the indexes from
  
  @return the string to drop the temporary indexes