expression: add NewDistAggFunc interface for mock tikv. (#3009)
expression: add NewDistAggFunc interface for mock tikv. (#3009)


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