MongoDB C++ 数组的写操作

MongoDB C++ 数组的写操作

经常会碰到这类问题，现在将前两年自己写过的代码总结一下，以后编程会方便很多。

Document中包含两个数组，一个简单点，每个元素都是string，一个复杂点，每个元素都是一个对象，有两个属性address和status.

> db.schedule.findOne({"_id" : ObjectId("51e930f92291307bb05a1a84")})

{

 "_id" : ObjectId("51e930f92291307bb05a1a84"),

 "direction" : 2,

 "messages" : [

  "m1",

  "m2",

  "m3"

 ],

 "receivers" : [

  {

   "address" : "000000000020",

   "status" : "waiting"

  },

  {

   "address" : "000000000018",

   "status" : "waiting"

  }

 ],

 "speed" : 3,

 "start_time" : "1374236921",

 "stay_time" : 1,

 "user_id" : ObjectId("518b7fc5117e87bce28f2444")

}

C++代码如下：

 

这个函数填充简单的数组，用到了BSONArrayBuilder. 注意其演示了insert方法的使用。

string AddScheduledMessage(ScheduledMessage const& m) {

  shared_ptr<mongo_session> mongo_session = mongo_session_factory::get_session();

  BSONObjBuilder data_builder;

  OID _id = OID::gen();

  data_builder.append("_id", _id);

  data_builder.append("user_id", mongo::OID(m.user_id));

  data_builder.append("start_time", m.start_time);

  data_builder.append("direction", m.direction);

  data_builder.append("speed", m.speed);

  data_builder.append("stay_time", m.stay_time);

  BSONArrayBuilder msgs_builder;

  size_t size = m.msgs.size();

  for (size_t i = 0; i < size; ++i) {

    msgs_builder.append(m.msgs[i]);

  }

  data_builder.append("messages", msgs_builder.arr());

  mongo_session->get().insert("db.schedule", data_builder.obj());

  return _id.str();

}

第二个函数添加了较复杂的数组，同时演示了update方法的使用。这个方法，假定receivers数组还不存在，采用$set命令进行设置。

void AssignScheduledMessages(ScheduledMessages & ms) {

  shared_ptr<mongo_session> mongo_session = mongo_session_factory::get_session();

  vector<shared_ptr<ScheduledMessage> >::iterator itor, last = ms.values.end();

  for (itor = ms.values.begin(); itor != last; ++itor) {

    shared_ptr<ScheduledMessage> m = *itor;

    BSONObjBuilder condition;

    condition.append("user_id", OID(m->user_id));

    condition.append("_id", OID(m->id));

    BSONArrayBuilder arr_builder;

    size_t size = m->receivers.size();

    for (size_t i = 0; i < size; ++i) {

      BSONObjBuilder rec;

      rec.append("address", m->receivers[i]->address);

      rec.append("status", m->receivers[i]->status);

      arr_builder.append(rec.obj());

    }

    BSONObjBuilder recs;

    recs.append("receivers", arr_builder.arr());

    BSONObjBuilder set;

    set.append("$set", recs.obj());

    

    mongo_session->get().update("db.schedule", mongo::Query(condition.obj()), set.obj());

  }

}

再复杂点。现在想修改一下address为00...20的那个元素的status="sending"。具体原理参考：

http://stackoverflow.com/questions/9247007/mongodb-update-the-specific-element-from-subarray

下面演示JavaScript代码：

db.schedule.update({"_id" : ObjectId("51e930f92291307bb05a1a84"), "receivers": {$elemMatch: {"address": "000000000020"}}}, {$set: {"receivers.$.status": "sending"}})

> db.schedule.findOne()

{

 "_id" : ObjectId("51e930f92291307bb05a1a84"),

 "direction" : 2,

 "messages" : [

  "m1",

  "m2",

  "m3"

 ],

 "receivers" : [

  {

   "address" : "000000000020",

   "status" : "sending"

  },

  {

   "address" : "000000000018",

   "status" : "waiting"

  }

 ],

 "speed" : 3,

 "start_time" : "1374236921",

 "stay_time" : 1,

 "user_id" : ObjectId("518b7fc5117e87bce28f2444")

}

$ 这是个占位符，表示第一个被找到的数组元素。文档：http://docs.mongodb.org/manual/core/update/#array

Name	Description
$	Acts as a placeholder to update the first element that matches the query condition in an update.

C++代码来了：

void SaveScheduleMessageStatus(string const& message_id, string const& address, string const& status) {

  shared_ptr<MongoSession> mongo_session = MongoSessionFactory::GetSession();

  BSONObjBuilder condition;

  condition.append("_id", OID(message_id));

  BSONObjBuilder con1;

  con1.append("address", address);

    

  BSONObjBuilder con2;

  con2.append("$elemMatch", con1.obj());

  condition.append("receivers", con2.obj());

  BSONObjBuilder recs;

  recs.append("receivers.$.status", status);

  BSONObjBuilder set;

  set.append("$set", recs.obj());

    

  mongo_session->GetDBClientBase().update("db.schedule", mongo::Query(condition.obj()), set.obj());

}

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MongoDB在PHP下的应用学习笔记 http://www.linuxidc.com/Linux/2013-07/87296.htm

MongoDB 入门指南、示例 http://www.linuxidc.com/Linux/2013-07/87106.htm

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