问在mongodb中散列分片键是如何工作的？

EN

{name: 'John', height: 73}
{name: 'Zardosht', height: 68}

 % mongodb-linux-x86_64-2.2.5/bin/mongo                 
MongoDB shell version: 2.2.5
connecting to: test
> db.runCommand({_hashBSONElement: {name: "John"}})
{
    "key" : {
        "name" : "John"
    },
    "seed" : 0,
    "out" : NumberLong("5553133884637223031"),
    "ok" : 1
}
> db.runCommand({_hashBSONElement: {name: "Zardosht"}})
{
    "key" : {
        "name" : "Zardosht"
    },
    "seed" : 0,
    "out" : NumberLong("8641066842148283865"),
    "ok" : 1
}