fix bugs for parent relationship
fix bugs for parent relationship

ehalpern/go-mysql-elasticsearch,siddontang/go-mysql-elasticsearch,EagleChen/go-mysql-elasticsearch,jack230230/go-mysql-elasticsearch,jrots/go-mysql-elasticsearch,siddontang/go-mysql-elasticsearch,jrots/go-mysql-elasticsearch,Charlesdong/go-mysql-elasticsearch,WangXiangUSTC/go-mysql-elasticsearch,WangXiangUSTC/go-mysql-elasticsearch,trigrass2/go-mysql-elasticsearch,roth1002/go-mysql-elasticsearch