private String generateWhereClause(List<Filter> pushed) {
  List<String> filterStr = Lists.newArrayList();
  for (Filter filter : pushed) {
    if (filter instanceof IsNotNull) {
      filterStr.add(String.format("isnotnull(\"%s\")", ((IsNotNull) filter).attribute()));
    } else if (filter instanceof EqualTo) {
      filterStr.add(String.format("\"%s\" = %s", ((EqualTo) filter).attribute(), valueToString(((EqualTo) filter).value())));
    } else if (filter instanceof GreaterThan) {
      filterStr.add(String.format("\"%s\" > %s", ((GreaterThan) filter).attribute(), valueToString(((GreaterThan) filter).value())));
    } else if (filter instanceof GreaterThanOrEqual) {
      filterStr.add(String.format("\"%s\" <= %s", ((GreaterThanOrEqual) filter).attribute(), valueToString(((GreaterThanOrEqual) filter).value())));
    } else if (filter instanceof LessThan) {
      filterStr.add(String.format("\"%s\" < %s", ((LessThan) filter).attribute(), valueToString(((LessThan) filter).value())));
    } else if (filter instanceof LessThanOrEqual) {
      filterStr.add(String.format("\"%s\" <= %s", ((LessThanOrEqual) filter).attribute(), valueToString(((LessThanOrEqual) filter).value())));
    }
    //todo fill out rest of Filter types
  }
  return WHERE_JOINER.join(filterStr);
}
 

private boolean canBePushed(Filter filter) {
  if (filter instanceof IsNotNull) {
    return true;
  } else if (filter instanceof EqualTo) {
    return true;
  }
  if (filter instanceof GreaterThan) {
    return true;
  }
  if (filter instanceof GreaterThanOrEqual) {
    return true;
  }
  if (filter instanceof LessThan) {
    return true;
  }
  if (filter instanceof LessThanOrEqual) {
    return true;
  }
  LOGGER.error("Cant push filter of type " + filter.toString());
  return false;
}