我有以下两个查询导致死锁。 但是不知道为什么在这种情况下Oracle试图使SSX表锁定。

所有测试样本都试图重现该问题，仅行锁定。

------------Blocker(s)----------- ------------Waiter(s)------------

Resource Name process session holds waits serial process session holds waits serial

TM-000386AF-00000000-00000000-00000000 101 298 SX SSX 65474 27 646 SX SSX 21533

TM-000386AF-00000000-00000000-00000000 27 646 SX SSX 21533 101 298 SX SSX 65474

Query:

DELETE FROM VERSANDPALETTE V WHERE V.ID IN (SELECT COLUMN_VALUE FROM TABLE(:B1 ))

----- Information for the OTHER waiting sessions -----

Session 646:

DELETE FROM VERSANDPALETTE WHERE ID IN (SELECT * FROM TABLE(:B1 )) AND ID NOT IN (SELECT * FROM TABLE(:B2 ))

我希望删除独立的行集，并且不创建表锁。

有人暗示为什么会发生吗？

编辑2 ：(问题的简化版本，需要2分钟才能复制)

谢谢你的帮助！

我使用以下代码对其进行了进一步测试：

-- setup

create table p ( x int primary key );

create table c ( x references p );

insert into p select rownum from dual connect by level <= 10;

insert into c select * from p;

commit;

-- 2 session test

-- session 1

update c set x = 2 where x = 1;

-- session 2

update c set x = 4 where x = 3;

delete from p where x = 3;

-- session 1

delete from p where x = 1;

-- deadlock is happening now

-- rollback both sessions

这导致了预期的死锁，因为子表fk上没有索引。 (正如您向我指出的那样)

令我困惑的是，当仅使用一个会话时，只有locked_mode 3 v $ locked_object打开。 某处应该有一个locked_mode 5行。

-- 1 session test

update c set x = 2 where x = 1;

update c set x = 4 where x = 3;

delete from p where x = 3;

delete from p where x = 1;

select

c.owner,

c.object_name,

c.object_type,

b.sid,

b.serial#,

b.status,

b.osuser,

b.machine,

a.locked_mode

from

v$locked_object a ,

v$session b,

dba_objects c

where

b.sid = a.session_id

and

a.object_id = c.object_id;

-- no locked_mode 5 entries...

-- rollback the session

添加索引可以解决该问题：

CREATE INDEX c_index ON c(x);

-- 2 session test

-- session 1

update c set x = 2 where x = 1;

-- session 2

update c set x = 4 where x = 3;

delete from p where x = 3;

-- session 1

delete from p where x = 1;

-- deadlock is not happening :)

所以我猜有一些锁升级在继续吗？ 因为单会话测试不会获取相同的表锁。