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截断表挂

WBOY
发布： 2016-06-07 16:04:56
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我有一个表gtlions.cannottruncatetable，该表中有零行，我可以从表中删除，但不能截断，挂起语句sql。详细信息如下：###################在会话 1 上：gtlions=# select version();版本----

我有一个表gtlions.cannottruncatetable，这个表中有零行，我可以从表中删除，但不能截断，挂起语句sql。

详细信息如下：
##################在会话 1 上：
gtlions=# select version();
                                                                       version                                                                        
------------------------------------------------------------------------------------------------------------------------------------------------------
 PostgreSQL 8.2.15 (Greenplum Database 4.2.5.2 build 1) on x86_64-unknown-linux-gnu, compiled by GCC gcc (GCC) 4.4.2 compiled on May 16 2013 23:35:01
(1 row)

gtlions=# \d+ gtlions.cannottruncatetable
                     Table "gtlions.cannottruncatetable"
      Column      |          Type          | Modifiers | Storage  | Description
------------------+------------------------+-----------+----------+-------------
 host_ip          | character varying      |           | extended |
 sys_int_id       | numeric                |           | main     |
 hostname         | character varying      |           | extended |
 prog_name        | character varying(300) |           | extended |
 app_name         | character varying      |           | extended |
 app_name_en      | character varying      |           | extended |
 app_id           | numeric(12,0)          |           | main     |
 serverport       | numeric(22,0)          |           | main     |
 logpath          | numeric(22,0)          |           | main     |
 log_generall     | numeric(22,0)          |           | main     |
 log_detail       | numeric(22,0)          |           | main     |
 transaction_open | numeric(22,0)          |           | main     |
 generall_open    | numeric(22,0)          |           | main     |
 is_use           | numeric(22,0)          |           | main     |
 id               | numeric(22,0)          |           | main     |
 logmasterswitch  | numeric(22,0)          |           | main     |
 process_numb     | numeric(22,0)          |           | main     |
 process_total    | numeric(22,0)          |           | main     |
 ips_addr         | character varying      |           | extended |
 host_id          | numeric(8,0)           |           | main     |
 prog_id          | numeric(8,0)           |           | main     |
 prog_apptypeid   | numeric(8,0)           |           | main     |
Has OIDs: no
Distributed by: (app_id)

gtlions=# select count(*) from gtlions.cannottruncatetable;
 count
-------
     0
(1 row)
 
gtlions=# select * from pg_class where relname='cannottruncatetable';
        relname         | relnamespace | reltype  | relowner | relam | relfilenode | reltablespace | relpages | reltuples | reltoastrelid | reltoastidxid | relaosegrel
id | relaosegidxid | relhasindex | relisshared | relkind | relstorage | relnatts | relchecks | reltriggers | relukeys | relfkeys | relrefs | relhasoids | relhaspkey |
relhasrules | relhassubclass | relfrozenxid | relacl | reloptions
------------------------+--------------+----------+----------+-------+-------------+---------------+----------+-----------+---------------+---------------+------------
---+---------------+-------------+-------------+---------+------------+----------+-----------+-------------+----------+----------+---------+------------+------------+-
------------+----------------+--------------+--------+------------
 cannottruncatetable |        17021 | 11051471 |    17010 |     0 |    23496358 |             0 |       19 |         0 |      11052150 |             0 |            
 0 |             0 | f           | f           | r       | h          |       22 |         0 |           0 |        0 |        0 |       0 | f          | f          |
f           | f              |   1558748414 |        |
(1 row)
 
gtlions=# select pg_size_pretty(pg_relation_size('gtlions.cannottruncatetable'));
 pg_size_pretty
----------------
 608 kB
(1 row)
 
gtlions=# vacuum analyze gtlions.cannottruncatetable;
VACUUM
gtlions=# select * from pg_class where relname='cannottruncatetable';
        relname         | relnamespace | reltype  | relowner | relam | relfilenode | reltablespace | relpages | reltuples | reltoastrelid | reltoastidxid | relaosegrel
id | relaosegidxid | relhasindex | relisshared | relkind | relstorage | relnatts | relchecks | reltriggers | relukeys | relfkeys | relrefs | relhasoids | relhaspkey |
relhasrules | relhassubclass | relfrozenxid | relacl | reloptions
------------------------+--------------+----------+----------+-------+-------------+---------------+----------+-----------+---------------+---------------+------------
---+---------------+-------------+-------------+---------+------------+----------+-----------+-------------+----------+----------+---------+------------+------------+-
------------+----------------+--------------+--------+------------
 cannottruncatetable |        17021 | 11051471 |    17010 |     0 |    23496358 |             0 |       16 |         0 |      11052150 |             0 |            
 0 |             0 | f           | f           | r       | h          |       22 |         0 |           0 |        0 |        0 |       0 | f          | f          |
f           | f              |   1558793687 |        |
(1 row)
 
gtlions=# select pg_size_pretty(pg_relation_size('gtlions.cannottruncatetable'));
 pg_size_pretty
----------------
 512 kB
(1 row)
 
gtlions=# select pg_backend_pid();
 pg_backend_pid
----------------
          14027
(1 row)
 
gtlions=# select now();
              now              
-------------------------------
 2014-10-15 16:52:25.112906+08
(1 row)
 
gtlions=# truncate table gtlions.cannottruncatetable;
Cancel request sent
ERROR:  canceling statement due to user request
gtlions=# select now();
              now              
-------------------------------
 2014-10-15 16:53:39.877717+08
(1 row)
 
 
###################On the session 2:
During the session 1 running, open new session 2, check the session 1
 
gtlions=# select procpid,sess_id,usename,current_query,waiting,age(now(),query_start) from pg_stat_activity where procpid=14027;
 procpid |  sess_id  | usename |                 current_query                 | waiting |       age       
---------+-----------+---------+-----------------------------------------------+---------+-----------------
   14027 | 113747736 | gpadmin | truncate table gtlions.cannottruncatetable; | f       | 00:00:49.671096
(1 row)
 
gtlions=# select * from pg_locks where pid=14027;                                                                               
   locktype    | database | relation | page | tuple | transactionid | classid | objid | objsubid | transaction |  pid  |        mode         | granted | mppsessionid |
 mppiswriter | gp_segment_id
---------------+----------+----------+------+-------+---------------+---------+-------+----------+-------------+-------+---------------------+---------+--------------+
-------------+---------------
 relation      |    17020 | 11052151 |      |       |               |         |       |          |  1658824590 | 14027 | AccessExclusiveLock | t       |    113747736 |
 t           |            -1
 relation      |    17020 | 11051470 |      |       |               |         |       |          |  1658824590 | 14027 | ShareLock           | t       |    113747736 |
 t           |            -1
 relation      |    17020 | 11051470 |      |       |               |         |       |          |  1658824590 | 14027 | AccessExclusiveLock | t       |    113747736 |
 t           |            -1
 relation      |    17020 | 11052150 |      |       |               |         |       |          |  1658824590 | 14027 | ShareLock           | t       |    113747736 |
 t           |            -1
 relation      |    17020 | 11052150 |      |       |               |         |       |          |  1658824590 | 14027 | AccessExclusiveLock | t       |    113747736 |
 t           |            -1
 transactionid |          |          |      |       |    1658824590 |         |       |          |  1658824590 | 14027 | ExclusiveLock       | t       |    113747736 |
 t           |            -1
(6 rows)
 
gtlions=# select procpid,sess_id,usename,current_query,waiting,age(now(),query_start) from pg_stat_activity where procpid=14027;
 procpid |  sess_id  | usename |                 current_query                 | waiting |       age       
---------+-----------+---------+-----------------------------------------------+---------+-----------------
   14027 | 113747736 | gpadmin | truncate table gtlions.cannottruncatetable; | f       | 00:01:03.655322
(1 row)
 
gtlions=# select * from pg_locks where pid=14027;                                                                               
   locktype    | database | relation | page | tuple | transactionid | classid | objid | objsubid | transaction |  pid  |        mode         | granted | mppsessionid |
 mppiswriter | gp_segment_id
---------------+----------+----------+------+-------+---------------+---------+-------+----------+-------------+-------+---------------------+---------+--------------+
-------------+---------------
 relation      |    17020 | 11052151 |      |       |               |         |       |          |  1658824590 | 14027 | AccessExclusiveLock | t       |    113747736 |
 t           |            -1
 relation      |    17020 | 11051470 |      |       |               |         |       |          |  1658824590 | 14027 | ShareLock           | t       |    113747736 |
 t           |            -1
 relation      |    17020 | 11051470 |      |       |               |         |       |          |  1658824590 | 14027 | AccessExclusiveLock | t       |    113747736 |
 t           |            -1
 relation      |    17020 | 11052150 |      |       |               |         |       |          |  1658824590 | 14027 | ShareLock           | t       |    113747736 |
 t           |            -1
 relation      |    17020 | 11052150 |      |       |               |         |       |          |  1658824590 | 14027 | AccessExclusiveLock | t       |    113747736 |
 t           |            -1
 transactionid |          |          |      |       |    1658824590 |         |       |          |  1658824590 | 14027 | ExclusiveLock       | t       |    113747736 |
 t           |            -1
(6 rows)
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根据售后的提示说明做以下检查：
截断表需要对所有段进行独占锁定才能成功完成事务。

似乎某些进程无法获取的段上有锁。

请按照以下步骤操作，并让我知道这是否有助于确定哪些部分是问题点。

识别进程是否已获取段上的所有锁，例如例如 s

从 pg_stat_Activity 中选择 procpid,sess_id,current_query ;
select * from pg_locks where mppsessionid=;并 grant='f';

第二个查询将告诉它在哪里无法获取锁（例如关系），一旦找到它，您可以使用下面的查询来了解谁在这些段上持有它。

select * from pg_locks where relation=<上面提到的第二个查询的关系值>并授予='t';

如果您发现段上有一些孤立进程持有锁，请尝试终止这些进程（避免使用kill -9，因为它会导致 postmaster 重置）

根据上述步骤我答复如下：

谢谢，详细信息：
在会话 1 上，截断表，仍然挂起：
gtlions=# select pg_backend_pid();
 pg_backend_pid
----------------
          14027
(1 row)
 
gtlions=# truncate table gtlions.cannottruncatetable;
Cancel request sent
ERROR:  canceling statement due to user request
 
On the session 2, check the lock info, not find result for the session:
gtlions=# select procpid,sess_id,current_query from pg_stat_activity  where procpid=14027;
 procpid |  sess_id  |                 current_query                 
---------+-----------+-----------------------------------------------
   14027 | 113747736 | truncate table gtlions.cannottruncatetable;
(1 row)
 
gtlions=# select * from pg_locks where mppsessionid=14027;
 locktype | database | relation | page | tuple | transactionid | classid | objid | objsubid | transaction | pid | mode | granted | mppsessionid | mppiswriter | gp_segm
ent_id
----------+----------+----------+------+-------+---------------+---------+-------+----------+-------------+-----+------+---------+--------------+-------------+--------
-------
(0 rows)
 
gtlions=# select * from pg_locks where mppsessionid=14027;
 locktype | database | relation | page | tuple | transactionid | classid | objid | objsubid | transaction | pid | mode | granted | mppsessionid | mppiswriter | gp_segm
ent_id
----------+----------+----------+------+-------+---------------+---------+-------+----------+-------------+-----+------+---------+--------------+-------------+--------
-------
(0 rows)
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Y的，这也太水了吧，我是在搞节日mppsessionid怎么会和那个关联起来。由于SR的位置在爱尔兰，这会估计人家正在休息，只好自己继续摸索：

gtlions=# select * from pg_locks where pid=14027;            
   locktype    | database | relation | page | tuple | transactionid | classid | objid | objsubid | transaction |  pid  |        mode         | granted | mppsessionid |
 mppiswriter | gp_segment_id
---------------+----------+----------+------+-------+---------------+---------+-------+----------+-------------+-------+---------------------+---------+--------------+
-------------+---------------
 relation      |    17020 | 11052151 |      |       |               |         |       |          |  1662808322 | 14027 | AccessExclusiveLock | t       |    113747736 |
 t           |            -1
 transactionid |          |          |      |       |    1662808322 |         |       |          |  1662808322 | 14027 | ExclusiveLock       | t       |    113747736 |
 t           |            -1
 relation      |    17020 | 11051470 |      |       |               |         |       |          |  1662808322 | 14027 | ShareLock           | t       |    113747736 |
 t           |            -1
 relation      |    17020 | 11051470 |      |       |               |         |       |          |  1662808322 | 14027 | AccessExclusiveLock | t       |    113747736 |
 t           |            -1
 relation      |    17020 | 11052150 |      |       |               |         |       |          |  1662808322 | 14027 | ShareLock           | t       |    113747736 |
 t           |            -1
 relation      |    17020 | 11052150 |      |       |               |         |       |          |  1662808322 | 14027 | AccessExclusiveLock | t       |    113747736 |
 t           |            -1
(6 rows)
 
gtlions=# select * from pg_locks where relation=&#39;gtlions.cannottruncatetable&#39;::regclass;
 locktype | database | relation | page | tuple | transactionid | classid | objid | objsubid | transaction |  pid  |        mode         | granted | mppsessionid | mppi
swriter | gp_segment_id
----------+----------+----------+------+-------+---------------+---------+-------+----------+-------------+-------+---------------------+---------+--------------+-----
--------+---------------
 relation |    17020 | 11051470 |      |       |               |         |       |          |  1662808322 | 14027 | ShareLock           | t       |    113747736 | t   
        |            -1
 relation |    17020 | 11051470 |      |       |               |         |       |          |  1662808322 | 14027 | AccessExclusiveLock | t       |    113747736 | t   
        |            -1
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653373155 | 15567 | AccessExclusiveLock | f       |    113747736 | t   
        |             0
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 13773 | AccessShareLock     | t       |     75284454 | f   
        |             0
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653366790 | 15569 | AccessExclusiveLock | f       |    113747736 | t   
        |             1
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 13789 | AccessShareLock     | t       |     75284454 | f   
        |             1
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 13807 | AccessShareLock     | t       |     75284454 | f   
        |             2
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653175988 | 15572 | AccessExclusiveLock | f       |    113747736 | t   
        |             2
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 13830 | AccessShareLock     | t       |     75284454 | f   
        |             3
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653198212 | 15577 | AccessExclusiveLock | f       |    113747736 | t   
        |             3
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653197212 | 15583 | ShareLock           | t       |    113747736 | t   
        |             4
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653197212 | 15583 | AccessExclusiveLock | t       |    113747736 | t   
        |             4
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 13858 | AccessShareLock     | t       |     75284454 | f   
        |             5
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653196128 | 15589 | AccessExclusiveLock | f       |    113747736 | t   
        |             5
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 13091 | AccessShareLock     | t       |     75284454 | f   
        |             6
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653195038 | 16256 | AccessExclusiveLock | f       |    113747736 | t   
        |             6
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 13098 | AccessShareLock     | t       |     75284454 | f   
        |             7
gtlions=# select * from pg_locks where relation=&#39;gtlions.cannottruncatetable&#39;::regclass and pid!=14027;
 locktype | database | relation | page | tuple | transactionid | classid | objid | objsubid | transaction |  pid  |        mode         | granted | mppsessionid | mppi
swriter | gp_segment_id
----------+----------+----------+------+-------+---------------+---------+-------+----------+-------------+-------+---------------------+---------+--------------+-----
--------+---------------
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653373155 | 15567 | AccessExclusiveLock | f       |    113747736 | t   
        |             0
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 13773 | AccessShareLock     | t       |     75284454 | f   
        |             0
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653366790 | 15569 | AccessExclusiveLock | f       |    113747736 | t   
        |             1
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 13789 | AccessShareLock     | t       |     75284454 | f   
        |             1
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 13807 | AccessShareLock     | t       |     75284454 | f   
        |             2
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653175988 | 15572 | AccessExclusiveLock | f       |    113747736 | t   
        |             2
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 13830 | AccessShareLock     | t       |     75284454 | f   
        |             3
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653198212 | 15577 | AccessExclusiveLock | f       |    113747736 | t   
        |             3
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653197212 | 15583 | ShareLock           | t       |    113747736 | t   
        |             4
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653197212 | 15583 | AccessExclusiveLock | t       |    113747736 | t   
        |             4
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 13858 | AccessShareLock     | t       |     75284454 | f   
        |             5
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653196128 | 15589 | AccessExclusiveLock | f       |    113747736 | t   
        |             5
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 13091 | AccessShareLock     | t       |     75284454 | f   
        |             6
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653195038 | 16256 | AccessExclusiveLock | f       |    113747736 | t   
        |             6
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 13098 | AccessShareLock     | t       |     75284454 | f   
        |             7
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653223811 | 16258 | AccessExclusiveLock | f       |    113747736 | t   
        |             7
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653164802 | 16261 | ShareLock           | t       |    113747736 | t   
        |             8
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653164802 | 16261 | AccessExclusiveLock | t       |    113747736 | t   
        |             8
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653228628 | 16266 | AccessExclusiveLock | f       |    113747736 | t   
        |             9
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 13118 | AccessShareLock     | t       |     75284454 | f   
        |             9
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653420396 | 16271 | AccessExclusiveLock | f       |    113747736 | t   
        |            10
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 13135 | AccessShareLock     | t       |     75284454 | f   
        |            10
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653180874 | 16277 | AccessExclusiveLock | f       |    113747736 | t   
        |            11
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 13146 | AccessShareLock     | t       |     75284454 | f   
        |            11
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653191613 |  8822 | ShareLock           | t       |    113747736 | t   
        |            12
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653191613 |  8822 | AccessExclusiveLock | t       |    113747736 | t   
        |            12
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653137608 |  8824 | ShareLock           | t       |    113747736 | t   
        |            13
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653137608 |  8824 | AccessExclusiveLock | t       |    113747736 | t   
        |            13
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653170505 |  8827 | AccessExclusiveLock | f       |    113747736 | t   
        |            14
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 19567 | AccessShareLock     | t       |     75284454 | f   
        |            14
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653146597 |  8832 | ShareLock           | t       |    113747736 | t   
        |            15
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653146597 |  8832 | AccessExclusiveLock | t       |    113747736 | t   
        |            15
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653166445 |  8838 | AccessExclusiveLock | f       |    113747736 | t   
        |            16
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 19593 | AccessShareLock     | t       |     75284454 | f   
        |            16
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653165327 |  8844 | ShareLock           | t       |    113747736 | t   
        |            17
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653165327 |  8844 | AccessExclusiveLock | t       |    113747736 | t   
        |            17
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653219764 | 11121 | ShareLock           | t       |    113747736 | t   
        |            18
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653219764 | 11121 | AccessExclusiveLock | t       |    113747736 | t   
        |            18
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653227486 | 11123 | AccessExclusiveLock | f       |    113747736 | t   
        |            19
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 15309 | AccessShareLock     | t       |     75284454 | f   
        |            19
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653155802 | 11125 | AccessExclusiveLock | f       |    113747736 | t   
        |            20
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 15320 | AccessShareLock     | t       |     75284454 | f   
        |            20
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 15330 | AccessShareLock     | t       |     75284454 | f   
        |            21
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653185053 | 11131 | AccessExclusiveLock | f       |    113747736 | t   
        |            21
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653157522 | 11137 | AccessExclusiveLock | f       |    113747736 | t   
        |            22
 relation |    17020 | 11051470 |      |       |               |         |       |          |           0 | 15341 | AccessShareLock     | t       |     75284454 | f   
        |            22
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653151279 | 11143 | ShareLock           | t       |    113747736 | t   
        |            23
 relation |    17020 | 11051470 |      |       |               |         |       |          |  2653151279 | 11143 | AccessExclusiveLock | t       |    113747736 | t   
        |            23
(48 rows)
 
gtlions=# select distinct pid from pg_locks where relation=&#39;gtlions.cannottruncatetable&#39;::regclass and pid!=14027;
  pid  
-------
  8822
  8824
  8827
  8832
  8838
  8844
 11121
 11123
 11125
 11131
 11137
 11143
 13091
 13098
 13118
 13135
 13146
 13773
 13789
 13807
 13830
 13858
 15309
 15320
 15330
 15341
 15567
 15569
 15572
 15577
 15583
 15589
 16256
 16258
 16261
 16266
 16271
 16277
 19567
 19593
(40 rows)
 
gtlions=# select procpid,sess_id,current_query,query_start, backend_start,client_addr,application_name from pg_Stat_activity where procpid in (select distinct pid from pg_locks where relation=&#39;gtlions.cannottruncatetable&#39;::r
gtlions.b-# ;
 procpid | sess_id | current_query | query_start | backend_start | client_addr | application_name
---------+---------+---------------+-------------+---------------+-------------+------------------
(0 rows)
 
gtlions=# select procpid,sess_id,current_query,query_start, backend_start,client_addr,application_name from pg_Stat_activity where procpid in (select distinct pid from pg_locks where relation=&#39;gtlions.cannottruncatetable&#39;::regclass and pid!=14027);                                                                                    procpid | sess_id | current_query | query_start | backend_start | client_addr | application_name
---------+---------+---------------+-------------+---------------+-------------+------------------
(0 rows)
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终于发现了点异常情况，这个对象被不存在的会话进程锁住了，顿时觉得有希望了。
午饭过后发现数据库又重新启动了，我F**K。。。。。自然而然又执行truncate是没有问题了，白白丢失了一次可以继续摸索的机会。
附：还有的疑惑就是，在使用alter table rename to之前是没有问题的，而这个命令和truncate应该持有同样级别的锁，按理说不应该成功一个失败。
相关标签：
g table
来源：php.cn
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