ddl: minor clean up (#2003)
ddl: minor clean up (#2003)


yuanwhy/tidb,ngaut/tidb,Cofyc/tidb,c4pt0r/tidb,wusphinx/tidb,cosmtrek/tidb,andelf/tidb,spongedu/tidb,JinheLin/tidb,ngaut/tidb,yuanwhy/tidb,c4pt0r/tidb,louishust/tidb,ngaut/tidb,simon-xia/tidb,ngaut/tidb,EvilMcJerkface/tidb,kyle-wang/tidb,c4pt0r/tidb,gaocegege/tidb,silenceper/tidb,myrice/tidb,silenceper/tidb,qiuyesuifeng/tidb,pingcap/tidb,kyle-wang/tidb,zimulala/tidb,mccxj/tidb,coocood/tidb,tiancaiamao/tidb,pingcap/tidb,ming-relax/tidb,silentred/tidb,pingcap/tidb,louishust/tidb,ngaut/tidb,8cbx/tidb,kyle-wang/tidb,spongedu/tidb,tiancaiamao/tidb,XuHuaiyu/tidb,coocood/tidb,zimulala/tidb,ueizhou/tidb,kyle-wang/tidb,ueizhou/tidb,astaxie/tidb,JinheLin/tidb,kyle-wang/tidb,kyle-wang/tidb,astaxie/tidb,andelf/tidb,XuHuaiyu/tidb,pingcap/tidb,pingcap/tidb,CodeRushing/tidb,simon-xia/tidb,Cofyc/tidb,silentred/tidb,8cbx/tidb,EvilMcJerkface/tidb,Nify/tidb,wusphinx/tidb,pingcap/tidb,cosmtrek/tidb,qiuyesuifeng/tidb,ngaut/tidb,anywhy/tidb,c4pt0r/tidb,zs634134578/tidb,liyu4/tidb,yangwenmai/tidb,qhsong/tidb,anywhy/tidb,c4pt0r/tidb,Nify/tidb,c4pt0r/tidb,yangwenmai/tidb,CodeRushing/tidb,liyu4/tidb,gaocegege/tidb,zs634134578/tidb,myrice/tidb,ming-relax/tidb,mccxj/tidb,qhsong/tidb