在Capped Collection MongoDB中更新？

Question

如何更新以下capped collection.i想更新城市：“newyork”到“someplace”

{
"_id" : 101,
"address" : [
    {
        "city" : "newyork",
        "country" : "america",
        "state" : "kerala"
    }
],
"age" : 39,
"email" : "ram@yahoo.com",
"name" : 98989898,
"phone" : 989898998

}

我使用了这个查询

db.employee.update({"_id":101,"address.city":"newyork"},{$set:  {"address.$.city":"somecity"}})

但它没有得到uddate而是我得到这个错误//

更新失败：上限ns中的对象无法成长。如何解决此问题。请帮助我。