@Test
  public void testParseIgnoreNulls() throws Exception {
    ASTNode tree = parseDriver.parse(
            "select last_value(b) ignore nulls over(partition by a) from t1", null).getTree();

    Assert.assertEquals(String.format(EXPECTED_RESULT_BASE, "TOK_IGNORE_NULLS"),
            ((ASTNode)tree.getChild(0)).dump());
  }
Test cases for parse WITHIN GROUP clause syntax.
function(expression) WITHIN GROUP (ORDER BY sort_expression)
parser/src/test/org/apache/hadoop/hive/ql/parse/TestNullTreatment.java