mongodb auto increment 自增

[php]代码库

> db.counters.insert(             //计数器表
       {
            _id: "userid",
            seq: 0
       }
    );
WriteResult({ "nInserted" : 1 })
> db.counters.find();
{ "_id" : "userid", "seq" : 0 }
> function getNextSequence(name) {      //取下个ID的函数
   var ret = db.counters.findAndModify(
       {
           query: { _id: name },
           update: { $inc: { seq: 1 } },  //这里seq就是上面counters表中的seq字段
           new: true,
           upsert: true
        }
   );
   return ret.seq;
 };
> db.users.insert(       //插入数据
      {
           _id: getNextSequence("userid"),
           name: "tank"
      }
 );
WriteResult({ "nInserted" : 1 })
> db.users.find();     //查看
{ "_id" : 1, "name" : "tank" }
> db.users.insert(
      {
           _id: getNextSequence("userid"),
           name: "test"
      }
 );
WriteResult({ "nInserted" : 1 })
> db.users.find();
{ "_id" : 1, "name" : "tank" }
{ "_id" : 2, "name" : "test" }