@Test
  public void testDropAlterViewNoLocks() throws Exception {
    driver.run("drop view if exists v_tab_acid");
    dropTable(new String[] {"tab_acid"});

    driver.run("create table if not exists tab_acid (a int, b int) partitioned by (p string) " +
      "stored as orc TBLPROPERTIES ('transactional'='true')");
    driver.run("insert into tab_acid partition(p) (a,b,p) values(1,2,'foo'),(3,4,'bar')");

    driver.run("create view v_tab_acid partitioned on (p) " +
      "as select a, p from tab_acid where b > 1");

    driver.compileAndRespond("alter view v_tab_acid as select a, p from tab_acid where b < 5");
    
    driver.lockAndRespond();
    List<ShowLocksResponseElement> locks = getLocks();
    Assert.assertEquals("Unexpected lock count", 2, locks.size());
    TestTxnDbUtil.checkLock(LockType.SHARED_READ,
      LockState.ACQUIRED, "default", "tab_acid", null, locks);
    // FIXME: redundant read-lock on db level
    TestTxnDbUtil.checkLock(LockType.SHARED_READ,
      LockState.ACQUIRED, "default", null, null, locks);
    driver.close();

    driver.compileAndRespond("drop view if exists v_tab_acid");

    driver.lockAndRespond();
    locks = getLocks();
    Assert.assertEquals("Unexpected lock count", 0, locks.size());
  }
T7 is a table with 2 partitions
1. run select from T7
2. run drop partition from T7
concurrently with 1 starting first so that 2 blocks
3. start another concurrent select on T7 - it should block behind waiting X (from drop) - LM should be fair
4. finish #1 so that drop unblocks
5. rollback the drop to release its X lock
6. # should unblock
ql/src/test/org/apache/hadoop/hive/ql/lockmgr/TestDbTxnManager2.java