db.createUser({user:"admin",pwd:"admin",roles:[{role:"dbAdminAnyDatabase",db:"admin"}]})
use admin
sh.enableSharding("xxx")
db.createCollection('xxx.a1')
sh.shardCollection("xxx.a1", {"_id" : "hashed"})
// 集合的切片,如果使用了upset,fillter字段做为切片key
sh.shardCollection("xxx.a1", {"name" : 1}, {"cn":1})