code: public void onSelectFilterFunction() {
          int selectedIdx = view.getSelectedFunctionIndex();
          if (selectedIdx >= 0) {
              CoreFunctionFilter coreFilter = getCoreFilter();
              CoreFunctionType functionType = getAvailableFunctions(coreFilter).get(selectedIdx);
  
              ColumnType columnType = metadata.getColumnType(coreFilter.getColumnId());
              List params = FilterFactory.createParameters(columnType, functionType);
              coreFilter.setType(functionType);
              coreFilter.setParameters(params);
  
              initFilterSelector();
              fireFilterChanged();
  
              if (!initFilterConfig().isEmpty()) {
                  view.showFilterConfig();
              }
          }
      }
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