optimizer/plan: sort switch case order.
optimizer/plan: sort switch case order.

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