@Override
  public synchronized boolean isAggregate(final FunctionName functionName) {
    return udafs.containsKey(functionName.text().toUpperCase());
  }
@Test
  public void shouldKnowIfFunctionIsAggregate() {
    loadAllUserFunctions(functionRegistry);
    assertFalse(functionRegistry.isAggregate(FunctionName.of("lcase")));
    assertTrue(functionRegistry.isAggregate(FunctionName.of("topk")));
  }