@Override
  public RequiredFieldResponse pushProjection(RequiredFieldList requiredFieldsInfo) throws FrontendException {
    // Store the required fields information in the UDFContext so that we
    // can retrieve it later.
    storeInUDFContext(signature, PRUNE_PROJECTION_INFO, requiredFieldsInfo);

    // HCat will always prune columns based on what we ask of it - so the
    // response is true
    return new RequiredFieldResponse(true);
  }
Base class for HCatLoader and HCatEximLoader
hcatalog/hcatalog-pig-adapter/src/main/java/org/apache/hive/hcatalog/pig/HCatBaseLoader.java