Oracle层次查询及其应用于子集的层次结构

Question

我正在为Oracle SE创建用于DB锁监视的自定义工具。基本上，我有调度器作业，它每10秒获取gv$session信息的快照，并将其存储在定制的ashstat_data表中。

现在，为了方便起见，我正试图创建一个视图，以分层格式列出会话阻塞链。该视图基于层次选择，它将阻塞会话显示为阻塞会话父级之下的子会话：

with l_snap as
(select * 
from ashstat_data
where sample_time>sysdate - interval '10' second )
SELECT 
s.sample_time,
' '||LPAD('-', (LEVEL-1), '-' ) || SESSION_ID asid,
s.wait_class,
s.event,
s.LOGON_TIME,
s.sql_id
FROM l_snap s
natural join dba_users d
inner join dba_objects do on s.LOCKED_OBJECT_ID=do.object_id
WHERE s.SESSION_ID IN 
(SELECT blocking_session FROM l_snap where blocking_session is not null)
OR s.blocking_session IS NOT NULL
CONNECT BY PRIOR 
 s.SESSION_ID=s.blocking_session
START WITH s.blocking_session IS NULL
;

到目前为止，只有当我从单个快照(where sample_time>sysdate - interval '10' second)中选择数据时，它才能完美地工作：

SAMPLE_TIME              ASID   WAIT_CLASS  LOGON_TIME          SQL_ID
5/9/2018 16:13:08.173    302    Idle        05/09/2018 11:33:57 
5/9/2018 16:13:08.173    -594   Application 05/09/2018 11:34:01 0wvbggc3p3swx
5/9/2018 16:13:08.173    -646   Application 05/09/2018 11:34:07 0wvbggc3p3swx

但是如果我从多个快照中选择记录(即。(where sample_time>sysdate - interval '12' second)它根据条件对它们进行排列：

SAMPLE_TIME              ASID   WAIT_CLASS  LOGON_TIME          SQL_ID
5/9/2018 16:17:18.166    302    Idle        05/09/2018 11:33:57 
5/9/2018 16:17:18.166    -594   Application 05/09/2018 11:34:01 0wvbggc3p3swx
5/9/2018 16:17:08.170    -594   Application 05/09/2018 11:34:01 0wvbggc3p3swx
5/9/2018 16:17:18.166    -646   Application 05/09/2018 11:34:07 0wvbggc3p3swx
5/9/2018 16:17:08.170    -646   Application 05/09/2018 11:34:07 0wvbggc3p3swx
5/9/2018 16:17:08.170    302    Idle        05/09/2018 11:33:57 
5/9/2018 16:17:18.166    -594   Application 05/09/2018 11:34:01 0wvbggc3p3swx
5/9/2018 16:17:08.170    -594   Application 05/09/2018 11:34:01 0wvbggc3p3swx
5/9/2018 16:17:18.166    -646   Application 05/09/2018 11:34:07 0wvbggc3p3swx
5/9/2018 16:17:08.170    -646   Application 05/09/2018 11:34:07 0wvbggc3p3swx

我想要实现的是，对每个快照分别表示阻塞链，所以最后的选择结果对于整个收集的数据如下所示：

SAMPLE_TIME              ASID   WAIT_CLASS  LOGON_TIME          SQL_ID
5/9/2018 16:17:18.166    302    Idle        05/09/2018 11:33:57 
5/9/2018 16:17:18.166    -594   Application 05/09/2018 11:34:01 0wvbggc3p3swx
5/9/2018 16:17:18.166    -646   Application 05/09/2018 11:34:07 0wvbggc3p3swx
5/9/2018 16:17:08.170    302    Idle        05/09/2018 11:33:57 
5/9/2018 16:17:08.170    -594   Application 05/09/2018 11:34:01 0wvbggc3p3swx
5/9/2018 16:17:08.170    -646   Application 05/09/2018 11:34:07 0wvbggc3p3swx

Answer 1

您可能需要将sample_time添加到CONNECT BY子句中：

with l_snap as
(select * 
from ashstat_data
where sample_time>sysdate - interval '10' second )
SELECT 
s.sample_time,
' '||LPAD('-', (LEVEL-1), '-' ) || SESSION_ID asid,
s.wait_class,
s.event,
s.LOGON_TIME,
s.sql_id
FROM l_snap s
natural join dba_users d
inner join dba_objects do on s.LOCKED_OBJECT_ID=do.object_id
WHERE s.SESSION_ID IN 
(SELECT blocking_session FROM l_snap where blocking_session is not null)
OR s.blocking_session IS NOT NULL
CONNECT BY PRIOR 
 s.SESSION_ID=s.blocking_session
 and prior s.sample_time = s.sample_time
START WITH s.blocking_session IS NULL
;