[web2py] Problem with DAL query self join

[Pradeeshnarayan]

I am trying to convert the below sql query to DAL query.

SQL query:
    SELECT L1_alt_obj.objid,L1_obj.objid
    FROM tbl_alt_objects
    JOIN tbl_objects on tbl_objects.horid = tbl_alt_objects.horid
        AND tbl_objects.objid = tbl_alt_objects.objid
    LEFT JOIN tbl_objects L1_obj ON L1_obj.horid = tbl_objects.horid
        AND L1_obj.objid = tbl_objects.rlord
    LEFT JOIN tbl_alt_objects L1_alt_obj ON L1_alt_obj.horid = 
tbl_objects.horid
        AND L1_alt_obj.objid = tbl_alt_objects.rlord
    WHERE tbl_alt_objects.horid=1076
        AND tbl_alt_objects.objid=1
SQL is working fine and getting result
+-------+-------+
| objid | objid |
+-------+-------+
|     4 |     5 |
+-------+-------+

        
DAL query:

L1_obj = db.tbl_objects.with_alias('l1_obj')
L1_alt_obj = db.tbl_alt_objects.with_alias('l1_alt_obj')
query = (db.tbl_alt_objects.horid==1076) & \
        (db.tbl_alt_objects.horid==db.tbl_objects.horid) & \
        (db.tbl_objects.objid==1) & 
(db.tbl_alt_objects.objid==db.tbl_objects.objid)
result = db(query).select(L1_obj.objid,L1_alt_obj.objid,
                        left=[
                            L1_obj.on((L1_obj.horid==horid) & 
(db.tbl_objects.rlord == L1_obj.objid)),
                            L1_alt_obj.on((L1_alt_obj.horid==horid) & 
(L1_alt_obj.objid==db.tbl_alt_objects.rlord))
                        ]
                   ).first()
                   
But I am getting an error as 

  File 
"/var/www/vhosts/astrozon/web2py/applications/astrozon/controllers/horoscope.py",
 
line 104, in testing
    L1_alt_obj.on((L1_alt_obj.horid==horid) & 
(L1_alt_obj.objid==db.tbl_alt_objects.rlord))
  File "/var/www/vhosts/astrozon/web2py/gluon/dal.py", line 7578, in select
    return adapter.select(self.query,fields,attributes)
  File "/var/www/vhosts/astrozon/web2py/gluon/dal.py", line 1315, in select
    rows = response(sql)
  File "/var/www/vhosts/astrozon/web2py/gluon/dal.py", line 1305, in 
response
    self.execute(sql)
  File "/var/www/vhosts/astrozon/web2py/gluon/dal.py", line 1392, in execute
    return self.log_execute(*a, **b)
  File "/var/www/vhosts/astrozon/web2py/gluon/dal.py", line 1386, in 
log_execute
    ret = self.cursor.execute(*a, **b)
  File "/var/www/vhosts/astrozon/web2py/gluon/contrib/pymysql/cursors.py", 
line 108, in execute
    self.errorhandler(self, exc, value)
  File 
"/var/www/vhosts/astrozon/web2py/gluon/contrib/pymysql/connections.py", 
line 184, in defaulterrorhandler
    raise errorclass, errorvalue
InternalError: (1054, u"Unknown column 'tbl_objects.rlord' in 'on clause'")

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