Postgres递归查询+分组+加入Django

Question

我的要求是编写一个 sql 查询来获取托管对象发生的子区域明智（故障）事件计数。我的数据库是 postgres 8.4。让我解释一下使用表结构。

我在 django 中的表： 托管对象：

class Managedobject(models.Model):
   name                = models.CharField(max_length=200, unique=True)
   iscontainer         = models.BooleanField(default=False,)
   parentkey           = models.ForeignKey('self', null=True)

事件表：

class Event(models.Model):
    Name        = models.CharField(verbose_name=_('Name'))
    foid        = models.ForeignKey(Managedobject)

托管对象记录：

NOC
   Chennai
      MO_1
      MO_2
      MO_3
   Mumbai
      MO_4
      MO_5
      MO_6
   Delhi
   Bangalore
IP
   Calcutta
   Cochin

事件记录：

event1 MO_1
event2 MO_2
event3 MO_3
event4 MO_5
event5 MO_6    

现在我需要获取所有子区域的事件计数。例如，

for NOC region:
  Chennai - 3
  Mumbai - 2
  Delhi - 0
  Bangalore - 0

到目前为止，我能够在两个不同的查询中得到结果。

1. 获取子区域。

   select id from managedobject where iscontainer = True and parentkey = 3489
   

2. 对于每个区域（使用for循环），获取计数如下：

   SELECT count(*) 
   from event ev 
   WHERE ev.foid 
   IN (
       WITH RECURSIVE q AS (
           SELECT h 
           FROM managedobject h 
           WHERE parentkey = 3489 
           UNION ALL 
           SELECT hi 
           FROM q 
           JOIN managedobject hi 
           ON hi.parentkey = (q.h).id 
       ) 
       SELECT (q.h).id FROM q
   )
   

请帮助组合查询以使其成为单个查询并获得前 5 个区域。由于在 django 中查询很困难，所以我要进行原始 sql 查询。

Answer 1

我收到了查询：

WITH RECURSIVE q AS ( 
  SELECT  h, 
          1 AS level, 
          id AS ckey, 
          displayname as dname 
  FROM managedobject h 
  WHERE parentkey = 3489  
    and logicalnode=True 

 UNION ALL 

 SELECT  hi, 
         q.level + 1 AS level, 
         ckey, 
         dname 
 FROM q 
   JOIN managedobject hi ON hi.parentkey = (q.h).id 
) 
SELECT count(ckey) as ccount, 
       ckey, 
       dname 
FROM q 
  JOIN event as ev on ev.foid_id = (q.h).id 
GROUP BY ckey, dname 
ORDER BY ccount DESC 
LIMIT 5