Multi-table query (left-join) problem in the Doctrine_Hydrator_Graph class

I tried below code. It must be return 2 records, but It returned 1 record. I traced Doctrine and found to reason in
Doctrine_Hydrator_Graph class line 165 ( $identifierMap[$rootAlias][$id[$rootAlias]] = $this->getLastKey($result); ) When couple $rootAlias not get record.

I attached my data and code. Is it problem?!

77 $q = Doctrine_Query::create();
78 $q->select("r.post_id as id, p.title as title, p.slug as slug, p.created_on as created_on")->
79 from("Relations r")->
80 leftJoin("r.Taxonomies t")->
81 leftJoin("t.Marks m")->
82 leftJoin("r.Posts p")->
83 where("m.slug = ?", $slug)->
84 andWhere("m.status = ?", self::PUBLISH)->
85 andWhere("p.status = ?", self::PUBLISH)->
86 andWhere("t.status = ?", self::PUBLISH)->
87 andWhere("t.type = ?", self::CATEGORY)->
88 orderBy("p.created_on desc");