When I try to search on Multilink items this happens
(roundup-0.7.5, postgresql backend):

psycopg.ProgrammingError: ERROR: JOIN/ON clause refers
to "_issue", which is not part of JOIN select
distinct(_issue.id),_priority._order,_issue._activity
from _issue,issue_nosy LEFT OUTER JOIN _priority on
_issue._priority=_priority.id where
_issue.id=issue_nosy.nodeid and issue_nosy.linkid in
('3','1') and _issue.__retired__ <> 1 order by
_priority._order,_issue._activity desc

[...]

  File
"/usr/lib/python2.3/site-packages/roundup/cgi/PageTemplates/PythonExpr.py",
line 72, in __call__
    return f()
  File "<string>", line 2, in f
  File
"/usr/lib/python2.3/site-packages/roundup/cgi/templating.py",
line 2056, in batch
    l = klass.filter(matches, filterspec, sort, group)
  File
"/usr/lib/python2.3/site-packages/roundup/backends/rdbms_common.py",
line 2270, in filter
    self.db.cursor.execute(sql, args)
ProgrammingError: ERROR:  JOIN/ON clause refers to
"_issue", which is not part of JOIN

It works when the FROM part is changed to ... from
_issue_nosy,_issue ...