@Test
  public void testMaterializedViewEnableRewriteNonBlocking() throws Exception {
    driver.run("drop materialized view if exists mv_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')");

    HiveConf.setBoolVar(conf, HiveConf.ConfVars.HIVE_ACID_LOCKLESS_READS_ENABLED, true);
    driver.run("create materialized view mv_tab_acid partitioned on (p) " +
      "stored as orc TBLPROPERTIES ('transactional'='true') as select a, p from tab_acid where b > 1");

    driver.compileAndRespond("alter materialized view mv_tab_acid enable rewrite");
    driver.lockAndRespond();

    List<ShowLocksResponseElement> locks = getLocks();
    Assert.assertEquals("Unexpected lock count", 1, locks.size());
    TestTxnDbUtil.checkLock(LockType.EXCL_WRITE,
      LockState.ACQUIRED, "default", "mv_tab_acid", null, locks);
    // cleanup
    txnMgr.rollbackTxn();
    driver.run("drop materialized view mv_tab_acid");
  }
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