planner: tidy code (#9845)
planner: tidy code (#9845)


ngaut/tidb,kyle-wang/tidb,kyle-wang/tidb,coocood/tidb,Cofyc/tidb,pingcap/tidb,pingcap/tidb,cosmtrek/tidb,pingcap/tidb,ngaut/tidb,EvilMcJerkface/tidb,c4pt0r/tidb,ngaut/tidb,qiuyesuifeng/tidb,pingcap/tidb,ming-relax/tidb,qiuyesuifeng/tidb,c4pt0r/tidb,EvilMcJerkface/tidb,cosmtrek/tidb,pingcap/tidb,Cofyc/tidb,ming-relax/tidb,kyle-wang/tidb,XuHuaiyu/tidb,ngaut/tidb,c4pt0r/tidb,ngaut/tidb,c4pt0r/tidb,coocood/tidb,c4pt0r/tidb,XuHuaiyu/tidb,ngaut/tidb,kyle-wang/tidb,pingcap/tidb,kyle-wang/tidb,c4pt0r/tidb,kyle-wang/tidb